Field research 1999

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Introduction
The Cornbelt Field was established in 1954 through the efforts of local interest groups, Kansas State University, and the state legislature. The objective then was to conduct research on the propagation, culture, and development of small-seeded legumes.
Emphasis since 1960 has been on fertilizer management; row spacings, planting rates and dates; variety testing; control of weeds and insects; cultural practices, including disease-and insect-resistant varieties; and cropping systems. Foundation seed of oat, wheat, and soybean cultivars are produced as needed to provide a source of quality seed of public varieties.

Soil Description
The soils on the Experiment Field are silty, windblown, Pleistocene sediments called loess (pronounced luss). Grundy silty clay loam, the dominant soil, has a black silty clay loam surface, usually more than 15 inches thick, and a silty clay subsoil. It typically occupies ridge crests and tablelands of western and southeastern Brown County and is extensive in northeastern Jackson, western Atchison, eastern Jefferson, and western Leavenworth counties in Kansas, as well as in western Richardson County, Nebraska. Grundy soil is similar to the Wymore soil of Nemaha and Marshall counties, Kansas and of Pawnee County, Nebraska.
The nearly level slopes have thick surface soil, which thins rapidly as slopes increase. Gradient terraces usually are needed to reduce sheet erosion, which is a serious hazard because the subsoil absorbs water slowly.

Weather Information
Precipitation during the growing season in 1998 was below normal. However, subsoil moisture and near normal rainfall during June, July, and August resulted in good yields of corn and soybeans.
The last killing frost was on March 24 (normal April 23), and the first killing frost was on November 11 (normal October 15). The frost-free period was 52 days longer than the 170-day average.

Introduction
Chemical weed control and cultivation have been used to reduce weed competition in row crops for many years. This test included 14 herbicide treatments and an untreated control. The major weeds in this test were large crabgrass, green foxtail, redroot pigweed, and velvetleaf.

Procedures
This test was conducted on a Grundy silty clay loam soil previously cropped to soybeans with a pH of 6.7 and an organic matter content of 3.2 percent. Garst 8541 IT corn hybrid was planted on May 5 at 23,500 seeds/a in 30-inch rows. Anhydrous ammonia at 120 lbs N/a was applied preplant. Herbicides were applied preemergent (PRE) -May 5 and postemergent (POST) -June 2. The plots were not cultivated. The data reported here are for crop injury ratings on June 19 and for weed control ratings on July 7. The first significant rainfall after PRE herbicide application was May 9 (0.45 inches). Plots were harvested on September 18 using a modified Gleaner E III plot combine.

Introduction
Chemical weed control and cultivation are commonly used to control weeds and reduce yield losses in soybean. This test included nine chemical treatments and an untreated control for evaluation of weed control. The major weed species in this test were large crabgrass, green foxtail, redroot pigweed, and velvetleaf.

Procedures
This test was conducted of a Grundy silty clay loam soil with a pH of 6.7 and organic matter content of 3.2% previously cropped to corn. Macon soybeans were planted on May 19 at 144,000 seeds/a in 30-inch rows. The herbicides were applied as follows: preplant, incorporated (PPI) and preemergence (PRE) -May 19 and postemergence (POST) -June 30. No significant rainfall was received after the PPI and PRE treatments until June 20 (1.39 inch). The plots were not cultivated. Ratings reported for crop injury were made on July 7 and 13, 8 and 14 days after application of the POST treatments. Ratings reported for weed control were made on July 13, 14 days after application of the POST treatments. Harvest was on October 26 using a modified Gleaner E III plot combine.

Results
Significant soybean injury was observed with the FirstRate + Cobra + Select treatment (Table 3). Crabgrass control was better than 85% with only three of the nine treatments: Python + Prowl, PRE + FirstRate, POST -92%; Authority Broadleaf, PRE + Roundup Ultra, POST -87%; and Dual II, PRE + FirstRate + Flexstar, POST -85%. All treatments gave 85% or greater control of green foxtail and redroot pigweed. The Authority Broadleaf, PRE + Roundup Ultra, POST and the FirstRate + Prowl, PRE treatments gave the poorest velvetleaf control (73 & 75%). The other seven treatments gave better than 85% control of velvetleaf. The control plot yielded only 12 bu/a, whereas the treated plots yielded from 24.5 to 40.5 bu/a. Soybean stands were thin and/or variable in some plots because of the poor soil moisture at planting time and affected some of the yields among treatments. Therefore, yield was not correlated highly with weed control.

Introduction
Current precision agriculture research and extension activities are conducted in cooperation with producers. Although this is an effective method, many desirable activities are limited by operating within the confines of the individual producer=s management practices.
For example, exploring the extreme ranges of nutrient inputs does not coincide with the economic interests of the producer, or intensive groundwater monitoring devices are difficult to implement in a farmer=s field. Long-term control for an entire field allows better research on precision agriculture as a management method.
A recent report to the North Central Soybean Research Program suggested establishing demonstration plots that combine research, education, and training. The report was generated from focus group discussions at four locations. Farmers with experience in precision agriculture participated in the discussion.
They suggested that one of the obstacles to adopting precision agriculture technologies was a lack of training programs and resources. A demonstration farm could meet those needs. With the establishment of this project, K-State would be the leader in this effort.
Developing such facilities at an existing research facility enhances both the research and extension aspects of such a facility as a result of the existing research base, weather data information, and traditional research equipment. As a result of these needs, an area at the Cornbelt Experiment Field was identified to be used as a Precision Agriculture Research and Extension site.

Procedures
Soil on the 53-acre area was sampled on a 5/8 acre (165 ft x 165ft) semi-random grid using DGPS on May 29, 1998. Soil samples were taken to a depth of 6 inches. Samples were analyzed for pH, P 2 O 5 , K 2 O and organic matter. Data were interpolated using an inverse distance-squared method in AgInfo GIS.
Prior to fall crop harvest, an Ag Leader PF3000 yield monitor was installed in an F2 Gleaner. Initial calibration curves were developed for corn, grain sorghum, and soybeans. All yield data were interpolated using an inverse distance-squared method in AgInfo GIS.

Results
Soil pH, P 2 O 5 , K 2 O, and organic matter varied to different degrees for each variable measured (Table 4). Soil test results indicate that pH and P levels had sufficient variability to warrant variable-rate applications ( Figure 1). Soil K 2 O levels did not have sufficient variability to warrant variable-rate applications (data not shown). Organic matter levels varied over a range of approximately 2 percentage points.
Soybean yields overall were quite low because of late-season drought and varied widely among terraces because of crop rotation differences (Table 5). Corn yields were lower than expected because of high temperatures during early ear development and low solar radiation levels during pollination and silking (Table 6).

Introduction
No-till planting of corn and other springplanted crops often takes place when the seedbed is cool and wet, raising questions about the needs for starter fertilizer. Research at the North Central Experiment Field has shown good response to starter fertilizer by corn and grain sorghum even on soil testing medium or higher in available phosphorus (P). The research also has shown that magnitude of response to the starter has varied among hybrids. The N-P ratio in the starter also has been a factor. Application of starter in direct seed contact using relatively low rates has been promoted by some companies. This study was initiated to evaluate direct seed placement of three P fertilizer materials and to compare direct seed placement to other methods of application.

Procedures
The study was established at the Cornbelt Experiment Field near Powhattan on a Grundy silty clay loam soil. The site was in soybeans in 1997, and the corn hybrid DeKalb DK595 was no-till planted on May 5 at 24,000 seeds/a. A soil sample taken prior to planting showed pH of 5.9, Bray P-1 test of 7 ppm (low), and exchangeable K of 162 (H to VH). Weed control was handled by the experiment field technicians. The P sources used were all liquids -ammonium polyphosphate 10-34-0 and two Alpine products, 9-18-9 and 6-24-6. The three products were used in treatments applied in direct seed contact to supply 8 lb/a of P 2 O 5 . No attempt was made to balance N and K 2 O supplied in the starter, but all treatments, except the no fertilizer check, were balanced for total N application at 120 lb/a using anhydrous ammonia applied after planting. In addition to the with-seed starter treatments, 10-34-0 was applied to supply 30 lb/a of P 2 O 5 either 2x2, broadcast, or dual placed with the anhydrous ammonia. Plots were four 30 in. rows by 30 ft replicated three times. Plots were harvested at maturity using a plot combine, and yields were adjusted to 15.5% moisture.

Results
A tremendous response was obtained to N fertilization (Table 7). Although stand counts were not taken, the direct seed placement of P had no obvious visual effect on emergence or stand. This was not unexpected; because all these treatments included less than 10 lb/a of N plus K 2 O in direct seed contact, which is within current K-State guidelines for this method. The highest yields were obtained from the 10-34-0 dual and 2x2 placements and 6-24-6 in direct seed contact. These treatments gave significantly better yields than the broadcast 10-34-0 (not incorporated) and 8 lb/a of P 2 O 5 placed with the seed as 10-34-0. The data clearly show that starter or dual placement of the P is needed to expect a response on this low testing soil.

EAST CENTRAL KANSAS EXPERIMENT FIELD Introduction
The research program at the East Central Kansas Experiment Field is designed to enhance the area's agronomic agriculture. Specific objectives are: (1) to identify the top performing varieties and hybrids of wheat, corn, grain sorghum, soybean, oat, and canola; (2) to determine the amount of tillage necessary for optimum crop production; (3) to evaluate weed control practices using chemical, nonchemical, and combination methods; and (4) to test fertilizer rates and placement methods for crop efficiency and environmental effects.

Soil Description
Soils on the fields 160 acres are Woodson. The terrain is upland, level to gently rolling. The surface soil is dark, gray-brown, somewhat poorly drained, silt loam to silty clay loam with a slowly permeable, clay subsoil. The soil is derived from old alluvium. Water intake is slow, averaging less than 0.1 inch per hour when saturated. This makes the soil susceptible to sheet erosion.

Weather Information
Precipitation during 1998 totaled 49.17 inches, which was 11.56 inches above the 30-yr average ( Table 1).
Most of the extra moisture occurred during the later part of the growing season.
Rainfall during August, September, October, and November exceeded normal rainfall by 14 inches. May was dry, with less than half the normal rainfall. Overall, moisture availability during the 1998 growing season was favorable.
The coldest temperatures in 1998 occurred in January, March, and December, with 10 days in the single digits or below. The very coldest day all year was December 22 when temperature was -2EF. The growing season was overall on the warm side, with 53 days exceeding 90 degrees. The hottest day was on July 20, when temperature reached 100 degrees.
The length of the 1998 growing season was longer than normal, with 207 frost-free days compared with the 185-day average. The last temperature 32EF or lower in the spring was on April 17 (average, April 18), and the first killing frost in the fall was on November 11 (average, October 21).

Introduction
Double-cropped soybean is a potentially profitable crop for east-central Kansas. However, it can be risky because of extremes of moisture at planting, dry summer conditions, and possible early frost. In the past, variety selection has been based mainly on full-season variety performance. This study evaluates soybean variety performance under double-crop conditions. Generally, soybean varieties that make the fullest use of the double-crop season, endure heat and moisture stress, set first pods fairly high, and tolerate cool night temperatures perform best. Procedures In 1998, nine soybean varieties were evaluated for double-crop performance. The soybean varieties were planted following winter wheat on July 9 in 7-inch wide rows with a notill drill. The wheat straw was burnt before planting to facilitate soil drying and planting. Soil at planting was still fairly wet, which resulted in some hairpinning of the remaining straw and occasional poor closure in the row. As a result, some unevenness in stands occurred. No herbicides were applied for weed control. However, burning the straw adequately controlled volunteer wheat and weeds. Rainfall amounts after planting were: July 2.53 in., August 5.29 in., September 9.14 in.; and October 6.78 in. Rainfall during the July through October double-crop season exceeded normal amounts by 10.27 inches. The first frost was on November 11, nearly 3 weeks later than normal. Wet soil delayed harvest until the ground froze. Harvest was on December 31. There was no evidence of shattering.

Results
Soybean yields ranged from 9 to 16 bu/a with a test average of 11 bu/a ( Table 2). This was a 10 bu/a lower yield than in 1997 and 11 bu/a lower yield than in 1996. Soybean plant height in 1998 was shorter compared to the previous 2 years. Plant heights varied with variety from 16 to 20 inches. Pod height ranged from 2.5 to 4.5 inches. The group V soybean varieties, Manokin and KS5292, produced the highest yields. This was because of an unusually long frost-free growing season. Normally, group V soybean varieties are limited by frost. The soybean maturity groups that typically have performed best for the east-central part of Kansas have been late group III, IV, and possibly very early group V varieties.

Introduction
Extensive acreages of soils in the east-central and southeast areas of Kansas have dense clay subsoils. These slowly permeable clay subsoils restrict drainage, limit depth of rooting, and limit crop-available moisture. As a result, crop yields are affected negatively. Various deep tillage practices have been used to loosen these claypan soils. Some farmers deep chisel or subsoil their fields every year, others every other year, and some on a less regular basis. The benefits from these various tillage operations have not been fully evaluated. The clay in these soils is predominantly montmorillonite, which expands and contracts with wetting and drying. Also, in most winters, freeze-and-thaw cycles loosen these soils to a depth of 6 to 8 inches or more.
These shrink-swell, freeze-thaw processes should alleviate much of the surface compaction that results from fertilization, planting, spraying, and harvesting. Consequently, the need for deep tillage is being questioned. Another question is whether some crops are affected more than others by deep tillage. This study evaluates various frequencies of subsoil tillage with shallower chisel plow and no preplant tillage for effects on corn and soybean yields.

Procedures
The experiment was started in 1996. Tillage treatments were no preplant tillage; chisel plowing every year (5-7 in. depth); and subsoil tillage at 8-12 in. depth yearly, every other year, and every 3 years. Treatments were established in two blocks, one for corn and one for soybean. Subsoil and chisel treatments were performed on November 26, 1997 for the 1998 growing season. All plots, except the no-till plots, were field cultivated before planting. Also, all plots were row-crop cultivated once for weed control. Corn (Pioneer 3563) was planted on May 8, 1998 and soybean (KS4694) on June 15, 1998. A mixture of 28-0-0 and 7-21-7 liquid fertilizer was coulter knifed on April 21, 1998 to provide 100 lb N, 34 lb P 2 O 5 and 11 lb K 2 O/a for corn. No fertilizer was applied for soybean.

Results
The 1998 corn grain yields ranged from 101 to 119 bu/a, with a test average of 111 bu/a ( Table 3). Although numerically different, the tillage effects on corn yield were not statistically significant. Yields averaged over 3 years show smaller and nonconsistent yield differences. No symptoms of N deficiency were seen in the no-till corn in 1998 as were observed in 1996. In 1997, we increased the N rate for all treatments.
Soybean yields for 1998 ranged from 30.4 to 38.2 bu/a, with a test average of 35 bu/a. Soybean yield was affected by the tillage treatments. Yields were lower for no-till and the every-third-year subsoil treatments compared to the other treatments. These lower yields may have resulted from less large pore space in soil and more saturated soil conditions with no tillage. Past tillage studies has indicated that soybean is sensitive to wet conditions and lack of oxygen in the soil during pod fill. Rainfall during the 1998 growing season was 11.56 inches above normal. Most of this extra rainfall occurred during the soybean pod development period.
To date, the results form this study suggest that subsoil tillage is having only a small effect on yield. At most, the yield increases are enough to offset the cost of operation. Soybean appears to be more sensitive to tillage than corn. These results have been obtained under conditions of above-normal moisture, so the effects of subsoiling may be different under drier conditions. Additional years of testing with more normal moisture are needed to fully determine the effects of subsoiling. We plan to repeat this study in 1999.

Acknowledgment
Appreciation is expressed to John Wray, Ottawa, KS for providing the tractor and subsoiler for establishing the subsoil treatments.

Introduction
Crop residues are being considered as a source of raw materials for various nonagricultural uses. But crop residues also are needed for soil erosion protection and to replenish organic matter in the soil. Grain producers currently harvest crop residues for livestock feed or other farm uses. Generally, this is not done every year from the same field. Also, some of these plant materials may be returned as animal wastes. With nonagricultural uses, this likely would not be the situation and the probability for more frequent harvests would increase. Harvesting crop residues continually would remove larger amounts of plant nutrients and accelerate the loss of soil organic matter. The effects of fertilizer management in offsetting these losses is not well understood.
This study was established to determine the long-term effects of removal and additions of varying levels of crop residues on crop yields and soil properties in a soybean-wheat-grain sorghum/corn rotation, fertilized with variable rates of nitrogen (N), phosphorus (P), and potassium (K).

Procedures
This study was established in the fall of 1980 on a nearly level, nonerosive (0-1% slope), Woodson silt loam soil at the East Central Kansas Experiment Field. The residue treatments were: (1) crop residue removed annually, (2) normal residue incorporated, and (3) twice (2X) normal residue incorporated (accomplished by evenly spreading the residue from the residue removal treatments). Superimposed over the residue treatments were fertilizer treatments; zero, low, normal, and high levels of N-P-K fertilizer as listed in Table 4. The cropping sequence was a soybean, wheat, grain sorghum rotation with corn substituted for grain sorghum beginning in 1994. Only one crop was grown each year. Grain yields and residue yields were measured each year. Soil samples (0 to 2-inch depth) were collected for chemical analysis after the 16th year.

Results
Grain yields and residue yields are summarized in Tables 5 and 6 for the first 9 years of the study and in Tables 7 and 8 for the second 9 years. On the whole, no interaction (P< 0.05) between the residue and fertilizer treatments affected grain or residue yields. Consequently, only main effects of the treatments are presented.
Grain yields and residue yields varied with crop and year. Soybean yields ranged from 12 to 54 bu/a, with residue yields ranging from 0.29 to 1.08 tons/a; wheat yields ranged from 12 to 60 bu/a, with residue yields ranging from 0.50 to 1.98 tons/a; and grain sorghum and corn yields ranged from 47 to 136 bu/a, with residue yields ranging from 1.04 to 2.87 tons/a. These differences verify that crop residue yields, like those of grain, with vary substantially with growing seasons.
The residue treatments, with the exception of 1987, caused no differences in grain or residue yield for any crop in any year. Neither the annual removal of crop residue nor the addition of 2X normal crop residue had a significant affect on grain or residue yields. In 1987, less residue yield was recorded for the 2X normal residue treatment than with normal residue. This may have been the result of nonuniform hail damage rather than an effect of treatment. Summed over all years, the totals of all grain and residue yields for all residue treatments differ by less than 2.5%. In contrast, the fertilizer treatments significantly affected grain and residue yields almost every year. Highest grain and residue yields were produced with the normal and high fertilizer treatments, and the lowest grain and residue yields with the zero and low fertilizer treatments. The normal and high fertilizer levels increased grain and residue yields on average 31% over no fertilizer. These data confirm that well fertilized crops will benefit not only in grain yield, but also in increased residue production.
Soil properties after the 16th year of residue and fertilizer treatments are shown in Table 9. Unlike grain and residue yields, soil properties were affected significantly by the residue treatments. Soil pH, exchangeable K, and organic matter decreased with crop residue removal. Soil exchangeable K was affected the most. The removal of crop residue depleted exchangeable K in the soil by nearly 20%. Doubling crop residue increased exchangeable K by nearly the same amount. This is because of the high K content in crop residue.
Soil organic matter decreased with crop residue removal.
Doubling crop residue increased soil organic matter. The fertilizer treatments caused the expected changes in soil properties. Soil pH decreased with fertilizer application. Available P, exchangeable K, and organic matter increased with fertilizer application.
These data suggest that on similar soils and with similar climate, and where crop residues are not needed for soil erosion protection, the occasional harvest of crop residues likely will have minimal impact on grain production. However, very long-term, continuous removal of crop residues remains questionable as a sustainable practice. It could cause further decreases in soil organic matter and eventually impact yield. The time line for this to occur is difficult to predict. The change resulting from removal of crop residue is a very slowly occurring process, which could take many years before stabilizing at a new level of equilibrium. With different environments and soil conditions, the effects of removing crop residues could be much different. This soil was initially quite high in soil organic matter and had high levels of fertility. Soil with lower organic matter and lower fertility likely would be affected more quickly by cropresidue removal.

Introduction
Research at the Harvey County Experiment Field deals with many aspects of dryland crop production on soils of the Central Loess Plains and Central Outwash Plains of central and south central Kansas and is designed to benefit directly the agricultural industry of the area. Focus is primarily on wheat, grain sorghum, and soybean, but also includes alternative crops such as corn and oats. Investigations include variety and hybrid performance tests, chemical weed control, tillage methods, fertilizer use, and planting practices, as well as disease and insect resistance and control.

Soil Description
The Harvey County Experiment Field consists of two tracts. The headquarters tract, 75 acres immediately west of Hesston on Hickory St., is all Ladysmith silty clay loam with 0-1% slope. The second tract, located 4 miles south and 2 miles west of Hesston, is comprised of 142 acres of Ladysmith, Smolan, Detroit, and Irwin silty clay loams, as well as Geary and Smolan silt loams. All have 0-3% slope. Soils on the two tracts are representative of much of Harvey, Marion, McPherson, Dickinson, and Rice Counties, as well as adjacent areas.
These are deep, moderately well to well-drained, upland soils with high fertility and good water-holding capacity. Water run-off is slow to moderate. Permeability of the Ladysmith, Smolan, Detroit, and Irwin series is slow to very slow, whereas permeability of the Geary series is moderate.

1997-1998 Weather Information
The wheat growing season began with ample fall rains that ensured the development of good stands. Precipitation remained above normal from December through March. April brought normal rainfall, before a much drier period set in during grain filling. Fall wheat growth was affected by below-normal temperatures, particularly cold in mid-November.
Minimum temperatures averaged 6 o F above normal during December, January, and February. Monthly maximum and minimum temperature averages were well below normal in March and April but above normal thereafter. Dry weather and warm temperatures in May and June reduced a potentially very high wheat yield. Wheat diseases generally were minimal.
Spring rains caused planting delays in some row crop experiments and stand reductions in others as a result of severe soil crusting. The prominent weather features of the row crop season were excellent early growing conditions following emergence, mid-season drouth, abundant late-season rains, and the absence of a fall frost.
Very dry conditions throughout August and the first 18 days of September coincided with high temperatures that reached or exceeded 100 o F on 9 days during this period. As a result, soybean seed development terminated early in some experiments and grain filling was affected adversely in sorghum as well.
Frost occurred last in the spring on April 17 and first in the fall on November 10. This frostfree season of 207 days was about 39 days longer than normal.

REDUCED TILLAGE AND CROP ROTATION SYSTEMS WITH WHEAT, GRAIN SORGHUM, CORN, AND SOYBEAN
Mark M. Claassen

Summary
Tillage system effects on continuous wheat, continuous grain sorghum, and annual rotations of wheat with row crops were investigated. Despite less cheat control in no-till, tillage systems had no significant effect on continuous wheat yield. Prior tillage for row crop did not meaningfully affect no-till wheat in rotations. Soybean and corn rotations improved wheat yields by an average of 6.5 bu/a in comparison with continuous wheat. Wheat after grain sorghum produced yields comparable to those of continuous wheat. Tillage systems did not meaningfully affect yields of continuous sorghum or row crops in rotation with wheat. However, wheat rotation increased sorghum yields by 10.7 bu/a. Introduction Crop rotations facilitate reduced-tillage practices, while enhancing control of diseases and weeds. Long-term research at Hesston has shown that winter wheat and grain sorghum can be grown successfully in an annual rotation. Although subject to greater impact from drouth stress than grain sorghum, corn and soybean also are viable candidates for crop rotations in central Kansas dryland systems that conserve soil moisture. Because of their ability to germinate and grow under cooler conditions, corn and soybean can be planted earlier in the spring and harvested earlier in the fall than sorghum, thereby providing opportunity for soil moisture replenishment as well as a wider window of time within which to plant the succeeding wheat crop. This study was initiated at Hesston on Ladysmith silty clay loam to evaluate the consistency of corn and soybean production versus grain sorghum in an annual rotation with winter wheat and to compare these rotations with monoculture wheat and grain sorghum systems.

Procedures
Three tillage systems were established for continuous wheat; two for each row crop (corn, soybean, and grain sorghum) in annual rotation with wheat; and two for continuous grain sorghum. Each system, except no-till, included secondary tillage as needed for weed control and seedbed preparation. Wheat in rotations was planted after each row-crop harvest without prior tillage. The following procedures were used. Continuous wheat no-till plots were sprayed on August 1, September 1, and October 21 with Roundup Ultra + ammonium sulfate (AS). Roundup Ultra rates were 1 qt/a, 1 pt/a, and 1 pt/a, respectively, in combination with 2.6 lb/a or 3.4 lb of AS. Variety 2137 was planted on October 22 in 8 in. rows at 90 lb/a with a CrustBuster no-till drill equipped with double disk openers. Wheat was fertilized with 120 lb N/a and 32 lb P 2 O 5 /a, applied as preplant, broadcast ammonium nitrate and in-furrow diammonium phosphate at planting.
No herbicides were required for broadleaf weed control in wheat during the growing season. Wheat was harvested on June 27, 1998.
No-till corn after wheat plots received the same Roundup treatments as WW-NT in early August and September. CW-NT plots also were sprayed with 1 lb ai/a atrazine in late October for control of cheat and winter annual broadleaf weeds. Because of wet soil, weeds were controlled in CW-V plots by mowing, Roundup + 2,4-D application, and fall chiseling. Two spring tillage operations with a mulch treader controlled remaining weeds and prepared the seedbed. Corn was fertilized with 111 lb/a N as ammonium nitrate broadcast prior to planting. An additional 14 lb/a N and 37 lb/a P 2 O 5 were banded 2 inches from the row at planting. A White no-till planter with double-disk openers on 30-in. centers was used to plant Golden Harvest H-2404 at approximately 23,000 seeds/a on April 14, 1998. Weeds were controlled with a preemergence application of Partner 65 DF + AAtrex 90 DF (3.85 + 0.28 lb/a). Row cultivation was not required. Corn was harvested on September 9.
Plots of no-till sorghum after wheat were treated with Roundup Ultra as noted for WW-NT, with a subsequent fall application of 1.1 lb/a AAtrex 90 DF and with a spring preplant application of 1 pt/a Roundup Ultra. GG-NT plots were sprayed with Roundup Ultra + 2,4-D LVE + AS (1 qt/a + 0.33 pt/a + 3.4 lb/a) just prior to planting. GW-V plots were managed like CW-V areas during the fallow period between wheat harvest and mid-April. A sweep-treader was used for the final preplant tillage operation in GW-V. GG-C plots were tilled once each with a chisel, mulch treader, and a sweep-treader between crops. Sorghum was fertilized like corn, but with 115 lb/a total N. Pioneer 8500 treated with Concep III safener and Gaucho insecticide was planted at 38,100 seeds/a in 30-inch rows on May 14. Preemergence application of Partner 65 DF at 3.85 lb/a + AAtrex 90 DF at 0.56 lb/a (rotation) or 1.1 lb/a (continuous sorghum) controlled weeds during the season without row cultivation.
Fallow weed control for no-till soybean after wheat consisted of Roundup Ultra + AS applications on August 1, September 1, April 17, and May 14. SW-V field procedures were basically the same as for GW-V. However, soybean received only starter fertilizer, and weeds were controlled after planting with preemergence Partner 65 DF + Scepter 70 DG (3.85 lb/a + 2.8 oz/a). Resnik soybeans were planted at 8 seeds/ft in 30-in. rows on May 14 and harvested on September 8.

Results Wheat
Crop residue covers after planting averaged 69, 75, and 47% in no-till wheat after corn, sorghum, and soybean, respectively (Table 2). In continuous wheat, residue cover ranged from 2% in burned plots to 68% with no-till. Wheat stands were good but slightly lower in WC-NTNT and WG-NTNT. Weed control was generally excellent. However, cheat control was somewhat poorer in WW-NT. Heading date tended to be delayed slightly in WC-NTNT, WG-NTNT, and WW-C, and more notably in WW-NT.
Precipitation pattern during the fall and winter months was favorable for wheat, particularly in rotations. Higher seeding rate and higher N rate for the 1998 crop contributed to less difference than previously noted between wheat following corn or soybean and wheat after sorghum or notill continuous wheat. Whole-plant N in wheat did not differ significantly among rotations, but tended to be higher in continuous no-till than in no-till/ V-blade systems with sorghum and soybean.
Wheat after soybean and corn produced the highest yields that were nearly equal. Yields of continuous wheat and wheat after sorghum did not differ. These systems produced an average of 42.5 bu/a, i.e., 6.5 bu/a less than the average for wheat following soybean or corn. Tillage system did not significantly affect continuous wheat, wheat after sorghum, or wheat after soybean. Although WC-NTNT produced 6.5 bu/a more than WC-NTV, this was not considered meaningful in light of 1997 results. Test weights were comparable for most treatments. No-till continuous wheat had significantly lower test weight at least partly because of the presence of cheat.

Row Crops
Crop residue covers for row crops following wheat averaged 33% for V-blade and 73% for no-till systems (Table 3). Tillage effects on corn were minor and of limited significance. A slight corn yield advantage for no-till versus V-blade systems was inconsistent with previous results.
Continuous sorghum as well as sorghum and soybean after wheat generally were not significantly affected by tillage system. The only exception was a delay in the number of days from planting to half bloom in no-till sorghum versus sorghum in chisel or V-blade systems. The delays averaged 2 and 5 days in sorghum after wheat and continuous sorghum, respectively.
Crop sequence significantly affected sorghum in several ways. In comparison with monoculture sorghum, rotation with wheat decreased the time to reach half bloom by 2 days, increased leaf N content, slightly increased the number of heads/plant, and increased yields by 10.7 bu/a.

Summary
Response of grain sorghum to cold temperatures was evaluated by comparing the performance of 46 hybrids with April versus June planting dates. Yield of sorghum planted early averaged 25 bu/a more than that of sorghum planted in late June. Asgrow A570, DeKalb DK-45, DeKalb DK-53, and MSG O 256 produced the highest yields in the early planting. Only four hybrids produced lower yields when planted early than when planted late, and this decline was generally not significant. Early planting reduced stands in some hybrids, with an average difference of 15% between the two dates. Stands of hybrids in the top yield group of the early planting ranged from 74 to 84%. Grain yields of sorghum planted in April were not related consistently to early plant vigor scores or seedling dry matter yield at 30 days after planting.

Introduction
Experiments at Hesston have shown the potential for increased yield of sorghum planted approximately 1 month earlier than typical June dates in south central Kansas. Early sorghum planting may spread the risk of drouth, reduce the risk of chinch bug injury, avoid damage from early fall frost, eliminate grain moisture dockage at harvest, increase profitability associated with better harvest season prices, spread field work load, and facilitate rotation to wheat in the fall.
Because of differences in hybrid response to cool conditions, more information is needed to characterize sorghum response to early planting. Investigations to evaluate growth and yield of a number of early-planted grain sorghum hybrids were initiated in 1998 at several locations, including Hesston. Hybrids were selected from among those being evaluated in the standard Kansas performance tests.

Procedures
Forty-six sorghum hybrids were planted in three replications on two dates corresponding to early (April 23) and late (June 26) timing. The experiment site was on a Geary silt loam soil that had been cropped to spring oats in 1997. Reduced tillage practices were used for seedbed preparation. The area was fertilized with 116 lb N/a and 35 lb P 2 O 5 broadcast and incorporated in late April. Sorghum was planted at 48,790 seeds/a in 30-inch rows with 7 lb/a Temik 15G insecticide applied in furrow. All sorghum seed was safened with Concep III. Immediately after planting, the respective areas were sprayed with 1 qt/a Dual + 1.1 lb/a AAtrex 90 DF. Grain harvesting for the respective planting dates was completed on September 3 and October 24.

Results
Grain sorghum planted in late June was affected adversely by fall army worms and drouth stress. Grain yield from the early planting averaged 25 bu/a more than from the late planting (Table 4). Only four hybrids produced lower yields when planted early, and this decline was generally not significant. Asgrow A570 produced the top yield of 128 bu/a in the early planting. DeKalb DK-45, DeKalb DK-53, and MSG O 256 had yields not differing significantly from that.
Final sorghum stands tended to be lower in the early planting, with a range from 14 to 86% versus 44 to 95% of the planting rate in the late planting. The average difference in stand between the two planting dates was 15%. Stands of hybrids in the top yield group of the early planting ranged from 74 to 84%. Asgrow A570 had the highest plant vigor score at 19 days after early planting. Nine other hybrids had comparable vigor scores. Three of the four hybrids in the top yield group had below-average vigor scores.
At 30 days after planting, dry matter yield averaged only 0.22 g/plant in the early planting but increased to 13.08 g/plant in the late planting (data not shown). Two of the top four grainproducing hybrids in the early planting had less than average seedling dry matter yield/plant. However, these differences were not statistically significant.
All hybrids required a significantly longer period of time to reach half bloom when planted early. This increase ranged from 14 to 26 days, with an average increase of 20 days. Maturity of most of the hybrids in the top yield group was delayed by less than the 20-day average. However, Asgrow A570 was delayed in maturity by 26 days when planted early. Plant heights were not affected significantly by planting date. No lodging occurred in the early planting. However, lodging averaged 14% and ranged from 0 to 68% in the late planting.
This project was funded partially by the Kansas Grain Sorghum Commission.

Introduction
Amplify-D is a product developed by Conklin Company to enhance early vigor of seedlings and, potentially, to increase plant stand. Not a pesticide, Amplify-D is intended to provide germinating seed with an exogenous source of AMP (adenosine monophosphate), a precursor of ATP (adenosine triphosphate), which provides energy to plant cells. Positive results with Amplify-D have been documented in cotton. This experiment was conducted at Hesston and several other locations to determine if grain sorghum planted at early and conventional dates would respond to Amplify-D seed treatment.

Procedures
Twelve sorghum hybrids were planted in three replications on two dates corresponding to early (April 24) and conventional (June 12) timing. The experiment site was on a Ladysmith silty clay loam soil that had been cropped to wheat in 1997. Reduced tillage practices were used for seedbed preparation. The area was fertilized with 114 lb N/a and 32 lb P 2 O 5 broadcast and incorporated in mid-April. Amplify-D was applied to Concep IIItreated seed at 4 oz/50 lb. Sorghum was planted at 48,790 seeds/a in 30-inch rows with 7 lb/a Temik 15G insecticide applied in furrow. Areas for the respective planting dates were sprayed shortly after planting with 1 qt/a Dual II + 0.56 lb/a or 0.28 lb/a AAtrex 90 DF. Ten plants/plot were harvested at 31 days after planting to determine dry matter accumulation. Sorghum from the early planting was harvested for grain on September 1, 1998. No yields were determined for the second planting because of very severe lodging in mid-September.

Results
Stands of some grain sorghum hybrids tended to be slightly lower with Amplify-D than without the seed treatment (Table 5). In the April planting, the average difference in stand was 4%. A similar trend in the June planting was not statistically significant (Table 6). Early vigor (April planting), dry weight at 31 days after planting, plant height, and heads/plant were not affected by Amplify-D. Half bloom was delayed slightly (1 day) with Amplify-D in some hybrids in one or both planting dates.
Grain yield from the early planting differed significantly among hybrids. Average yields for sorghum with Amplify-D were 7 bu/a lower than these for sorghum without treatment. However, this effect was significant only at P < 0.11. Bushel weight was not affected significantly by Amplify-D.
This project was funded partially by the Kansas Grain Sorghum Commission.

Summary
At the end of the first cycle in a vetchsorghum-wheat rotation, fall residual soil nitrate nitrogen (N) was 4 lb/a higher than in a sorghumwheat rotation. At the beginning of the second cycle of the rotation, hairy vetch planted in mid-September and terminated on May 14 produced an average dry matter yield of 1.64 ton/a. The corresponding potential N contribution was 94 lb/a for the succeeding sorghum crop. Seasonal environmental factors caused increased variation in treatment effects. Vetch significantly increased sorghum leaf N levels and tended to increase grain yields as well. However, the yield response was not significant. In the absence of fertilizer N, sorghum after vetch yielded about 12 bu/a more than sorghum without a preceding cover crop. The apparent yield enhancement following vetch was equivalent to at least 30 lb/a of fertilizer N. Method of vetch termination did not influence leaf N level or yield of sorghum. Fertilizer N rate affected leaf N level significantly, but not sorghum yield.

Introduction
Interest in the use of legume winter cover crops has been rekindled by concerns for soil and water conservation, dependency on commercial fertilizer, and maintenance of soil quality. Hairy vetch is a good candidate for the cover crop role because it can be established in the fall when water use is reduced, it has winterhardiness, and it can fix substantial N. This experiment was conducted to investigate the effect of hairy vetch and N fertilizer rates on the supply of N to the succeeding grain sorghum crop as well as to assess sorghum yield response when the vetch is terminated by tillage versus by herbicides.

Procedures
The experiment was established on a Geary silt loam soil with the initial planting of hairy vetch following winter wheat in the fall of 1995. Sorghum was grown in 1996 after vetch had been terminated, and the comparison was made with sorghum in annual rotation with wheat alone. No-till winter wheat without fertilizer was recropped following sorghum. Reduced-tillage practices with a disk and field cultivator were used to control weeds and prepare a seedbed. In the second cycle of the rotation, hairy vetch plots were planted at 20 lb/a in 8-in. rows with a grain drill equipped with double-disk openers on September 16, 1997.
Volunteer wheat was controlled by an April application of Fusilade DX + crop oil concentrate (10 oz/a + 1% v/v). One set of vetch plots was terminated by disking on May 14. Hairy vetch in a second set of plots was terminated at that time with Roundup Ultra + 2,4-D LVE (1 qt + 1.5 pt/a).
Vetch forage yield was determined by harvesting a 1 sq m area from each plot on May 13, 1998. Nitrogen fertilizer treatments were broadcast as ammonium nitrate on June 11, 1998. All plots received 35 lb/a of P 2 O 5 , which was banded as 0-46-0 at planting. Pioneer 8505 grain sorghum treated with Concep III safener and Gaucho insecticide was planted after a rain delay at approximately 42,000 seeds/a on June 29, 1998. Weeds were controlled with a preemergence application of Microtech + AAtrex 90 DF (2.5 qt/a + 0.28 lb/a). Grain sorghum was combine harvested on October 24.

Results
Initial soil nitrate N (0 to 2 ft) averaged 24 lb/a in the sorghum-wheat rotation and 28 lb/a in the vetch-sorghum-wheat system. Because of poor germination, hairy vetch establishment in the fall was limited, with disuniformity in some plots. Average ground cover on November 13, 1997 was 12%. (Table 7). Hairy vetch was beginning to bloom at the time of termination in May. Vetch dry matter yield averaged 1.64 ton/a, and N content was 2.94%. The average potential amount of N to be mineralized for use by the sorghum crop was 94 lb/a. Disking to terminate hairy vetch growth did not adversely affect soil moisture at the surface because of subsequent rains, which ultimately delayed planting. Sorghum stands averaged 38,370 plants/a and were relatively uniform across treatments. Fall armyworms caused considerable damage to sorghum leaves. Drouth stress occurred from mid-August through mid-September. At the zero N rate, leaf N at boot to early heading stage was higher in sorghum after vetch than in sorghum without a prior vetch cover crop.
This increase was equivalent to that with 30 lb/a of fertilizer N. Method of vetch termination had no effect on leaf N. The overall effect of N rate on leaf N was significant. In sorghum not following vetch, leaf N increased mostly with the first increment (30 lb/a) of fertilizer N, whereas in sorghum after vetch, leaf N increased inconsistently with N rates.
Grain sorghum maturity (days to half bloom) was not affected by any of the treatments. With zero fertilizer N, sorghum after vetch yielded about 12 bu/a more than sorghum without a preceding cover crop. The apparent yield enhancement following vetch was equivalent to at least 30 lb/a of fertilizer N. Nevertheless, when averaged over N rates, the effects of vetch and termination method on sorghum yield were not statistically significant. Yield of sorghum without a prior vetch crop increased by 11 to 14 bu/a with fertilizer N, but most of this occurred with the 30 lb/a rate. Sorghum yields following vetch showed no response to N fertilizer. The overall effect of N rate on yield was not significant.
This project was funded partially by the Kansas Rural Center through the Covered Acres Cluster of south central Kansas.

Summary
Response of wheat in annual wheat-sorghum and wheat-vetch-sorghum rotations was compared at N fertilizer rates of 0 to 90 lb/a. Prior hairy vetch cover crop as well as N rates significantly affected soil nitrate N concentration at the time of wheat planting. Notably, soil nitrate N levels significantly increased only at N rates of 60 and 90 lb/a and only in the rotation involving vetch. Both hairy vetch and N rate significantly increased wheat yield. When averaged over N rates, wheat following vetch-sorghum produced 9 bu/a more than wheat in the rotation without hairy vetch. The residual vetch benefit was equivalent to 28 lb/a of fertilizer N. Wheat after vetch-sorghum appeared to be nearer a maximum yield at 90 lb/a of N than did wheat without a prior hairy vetch crop.

Introduction
Hairy vetch can be planted in September following wheat and used as a winter cover crop ahead of grain sorghum in an annual wheatsorghum rotation. Soil erosion protection and N contribution to the succeeding crop(s) are potential benefits of including hairy vetch in this cropping system. The amount of N contributed by hairy vetch to grain sorghum has been under investigation. The longer term benefit of vetch in the rotation is also of interest. This experiment concludes the first cycle of the crop rotation in which the residual effects of vetch as well as N fertilizer rates were measured in terms of soil N as well as N uptake and yield of wheat.

Procedures
The experiment was established on a Geary silt loam soil with the initial planting of hairy vetch following winter wheat in the fall of 1996. Sorghum was grown in 1997 with or without the preceding cover crop. Variety 2137 winter wheat was no-till planted in 8-inch rows into sorghum stubble on November 8, 1997 at 90 lb/a with 32 lb/a of P 2 O 5 fertilizer banded in the furrow. Fertilizer N was broadcast as 34-0-0 on April 6, 1998 at rates equal to those applied to the prior sorghum crop. Wheat was harvested on June 26.

Results
Hairy vetch terminated on April 25 and May 14, 1997, respectively produced 2.66 and 2.99 ton/a of dry matter, yielding 147 and 188 lb/a of N potentially available to the sorghum that followed (Table 8). However, the contribution of vetch to the yield of sorghum was equivalent to only 70 and 89 lb/a of fertilizer N. Prior hairy vetch cover crop as well as N rates significantly affected soil nitrate N (0 to 2 ft) at the time of wheat planting. In wheat after sorghum, soil nitrate N averaged only 7 lb/a. By comparison, wheat after vetch-sorghum averaged 21 lb/a of nitrate N because of carryover from the highest fertilizer N rates. Date of vetch termination had no effect on soil N. Also, N rates in sorghum without vetch had no effect on residual soil nitrate N. But, rates of 60 and 90 lb/a of N resulted in soil nitrate N levels of 22 and 43 lb/a following sorghum after vetch.
Residual effect of hairy vetch on wheat yield was positive and significant, but vetch termination date did not influence wheat yield significantly. When averaged over N rates, wheat yield following vetch-sorghum averaged 38 bu/a, about 9 bu/a more than for wheat with no prior cover crop. In wheat after sorghum without vetch, each 30 lb/a increment of fertilizer N significantly increased yield. This trend suggested that yields were below maximum at the 90 lb/a rate of fertilizer N. In wheat after vetch-sorghum, yields also increased with increasing fertilizer N, but appeared to be closer to a maximum at 90 lb/a of N. The yield of wheat after vetch-sorghum at the zero N rate indicated a residual vetch benefit equivalent to 28 lb/a of fertilizer N.
Vetch had no significant residual effect on wheat test weight, whole-plant N content at heading, or grain N level. Fertilizer N significantly increased plant N and grain N, with highest levels occurring at the 90 lb/a rate. Wheat test weight decreased somewhat with N rate.   -September, 1996, and terminated the following spring. 2 N applied as 34-0-0 June 23, 1997 for sorghum and April 6, 1998 for wheat. 3 Oven dry weight and N content just prior to termination. 4 Mean nitrate nitrogen at 0 -2 ft. depth in mid-November, 1997. 5 Whole-plant N concentration at heading.

Summary
Chloroacetamide herbicides were applied preemergence at normal and double use rates to eight sorghum hybrids treated with Concep III safener and planted in late April. At 19 days after planting, minor sorghum injury occurred only with double rates of Frontier and Dual II Magnum. No interactions between hybrids and herbicides were detected in the injury ratings. Herbicide treatments did not significantly affect sorghum stands or yields.

Introduction
In prior research at Hesston, grain sorghum planted early in May outperformed that planted at the conventional time in June during years with favorable seasonal weather patterns. In those experiments, unsafened sorghum seed was planted, and Ramrod (propachlor) was applied for preemergence grass control. Stronger grass herbicides such as Dual, Partner, and Frontier were avoided here to reduce the possibility of injury to stand establishment under stressful conditions of cool soil temperatures. Over time, grass control became a greater concern in earlyplanted grain sorghum because of a slower development of plant canopy and late emergence of weeds. This experiment was conducted to assess the effects of five grass herbicides applied at normal and double rates on eight early-planted grain sorghum hybrids.

Procedures
Grain sorghum hybrids were selected for this study on the basis of genetic diversity, general use by growers, previous investigations on cold tolerance, and endosperm color. Grain sorghum was grown on the site in 1997. The area was fertilized with 114 lb N/a and 32 lb P 2 O 5 /a broadcast and incorporated in mid-April. The seedbed was prepared with a field cultivator and mulch treader. Sorghum seed treated with Concep III safener and Gaucho insecticide was planted about 1.25 inches deep at 2.8 seeds/ft in 30-in. rows on April 24, 1998. Immediately after planting, all herbicide treatments were applied in 20 gal/a of water with XR8003 flat-fan nozzles. Injury ratings and stand counts were taken at 19 and 32 days after planting. Plots were harvested on August 31 and September 1.

Results
Seedbed condition was fair. Soil temperatures at seed depth stayed cool after planting until May 6. Light rains fell at 5, 8, and 11 days after planting. More substantial rainfall events occurred at 3, 4, and 15 days after planting in which amounts of 0.78, 1.13, and 0.44 inch were recorded, respectively. Sorghum emergence began about May 7 and reached 94% of the final average stand 7 days later.
Injury ratings were made on the basis of the specific herbicide injury symptoms such as leaf malformations and discoloration. The injury percentage ratings were calculated by dividing the number of injured sorghum seedlings by the total number of plants. On May 13, sorghum injury averaged 2% (Table 9). Significant injury at this time was noted only with double rates of Frontier and Dual II Magnum, at 8 and 3%, respectively. No interactions between hybrids and herbicides were detected in the injury ratings. On May 26, average injury decreased to less than 1%, with no significant differences among treatments.
Hybrid effects on injury, however, were significant on both evaluation dates. Initially, greatest injury was noted in DeKalb DK-40y, a hybrid with yellow endosperm; Mycogen 1482; NC+ 6B50; and Northrup King KS 710. Ratings did not differ significantly among the remaining hybrids. At the second evaluation approximately 2 weeks later, DeKalb DK-40y continued to have the highest level of injury (2%), whereas DeKalb DK-35, Mycogen 1506, NC+ 6B50, and Pioneer 8699 showed the least injury.
Sorghum populations on May 13 averaged 38,400 plants/a or 73% of the planting rate. Final populations on May 26 increased to 40,900 plants/a, i.e., 78% of the number of seed planted. Herbicide treatments did not significantly affect sorghum stands. Hybrids differed considerably in population. NC+ 6B50 had the highest and Northrup King KS 710 had the lowest stand percentages. Double rates of Frontier, Harness CR, and Dual II Magnum caused a small but statistically significant increase in the number of days to half-bloom in comparison with the control (atrazine alone). All double herbicide rates, except for Ramrod, caused a slight increase in plant height when compared with the control.
Herbicide treatments had no significant effects on yield or bushel weight of grain produced (Table 10). However, significant yield differences occurred among hybrids. Mycogen 1506 produced the top yield of 86 bu/a. Northrup King KS 710 recovered well from initial injury and low stand percentages to produce a comparably high yield of 83 bu/a. DeKalb DK-35, with the least herbicide injury, had the lowest yield of 66 bu/a.

Summary
Twenty-four herbicide treatments were evaluated for crop tolerance and weed control efficacy in soybean. Although Cobra caused some foliar burn, none of the treatments produced lasting injury to soybean. Broadstrike + Dual, Authority First + Classic, and Authority First + Prowl provided excellent preemergence (PRE) control of Palmer amaranth and redroot pigweed. PRE grass herbicides were less effective than usual because of initial dry conditions followed by heavy rainfall. Weather interference caused late application of postemergence (POST) herbicides. Best control of large crabgrass occurred with POST treatments involving Roundup Ultra or Assure II. Various late POST treatments provided good to excellent control of oversized pigweeds. Drouth stress obscured treatment effects on soybean yield.

Introduction
Successful soybean production is dependent upon effective weed control. Growers may choose from a number of herbicide options that can accomplish this objective. In recent years, the number of herbicides available for weed control in soybean has increased notably. This experiment was conducted to evaluate new herbicides and herbicide combinations for weed control efficacy as well as soybean tolerance.

Procedures
Spring oats were grown on the experiment site in 1997. The soil was a Smolan silt loam with pH 6.7 and 2.4% organic matter. To promote uniformity of weed populations, pigweed and crabgrass seed were broadcast and incorporated with a field cultivator as the last preplant tillage. Asgrow 3601 Roundup Ready + STS soybean was planted at 142,000 seeds/a in 30-inch rows on June 11, 1998. Seedbed condition was good, but soil moisture was insufficient for soybean emergence. All herbicide treatments were broadcast in 20 gal/a of water, with three replications per treatment. These were applied with XR8003 flat fan nozzles at 20 psi PRE on June 11or 18 psi POST on July 14 (Table 11). POST 2 herbicides were applied as follows: treatment 14 on July 15 and treatments 11 and 12 on August 11. Because of weather delay, POST treatments actually were applied when soybean was 6 to 9 inches tall with three fully expanded trifoliate leaves; pigweeds mostly ranged from 6 to 32 inches; and large crabgrass height was 1.5 to 7 inches. POST 2 Synchrony STS in treatment 14 was applied to relatively few pigweeds ranging up to 12 inches in height on the day following POST application of Assure II for grass control. POST 2 herbicides in treatments 11 and 12 were applied later when soybean was 26 to 33 inches tall; pigweeds were few and ranged from 2 to 18 inches; and large crabgrass was 1 to 8 inches in height.
Crop injury and weed control were evaluated at various times during the growing season. Soybean was harvested on October 27, 1998.

Results
Three weeks of dry weather preceded planting. Seedbed condition was good, but soil moisture was insufficient for soybean emergence. Hard rains 11 days later caused soil crusting. Rainfall totaled 3.01 inches for the period 11 to 15 days after planting.
Soybean populations averaged approximately 99,320 plants/a. Dense pigweed (primarily Palmer amaranth with some redroot pigweed) and large crabgrass populations developed.
Unforecasted heavy rains in early July prevented the first scheduled POST applications. A prolonged hot and wet period that followed allowed pigweed growth to explode. Consequently, weeds were much larger than intended at the time these treatments were made. Light rain fell about 4 hours after the POST 2 applications in treatments 11 and 12, but did not affect weed control.
Broadstrike + Dual as well as Authority First + Classic provided excellent PRE control of Palmer amaranth and redroot pigweed. For this reason, little improvement in pigweed control occurred when these treatments were followed with POST herbicides. Expert alone POST failed to control Palmer amaranth. Pursuit POST with or without PRE Prowl performed unsatisfactorily because of the advanced stage of pigweed growth at application. Late season evaluation of Palmer amaranth indicated that the Pursuit + Pinnacle combination significantly improved control, whereas Pursuit + Cobra did not enhance control in comparison with Pursuit alone. Raptor also was superior to Pursuit alone in the late August rating of Palmer amaranth control. Single as well as sequential Roundup Ultra applications effectively controlled Palmer amaranth and redroot pigweeds. Large crabgrass control was fair to good with Dual or Broadstrike + Dual, poor with Prowl, fair with Pursuit or Raptor, and poor with Pursuit + Pinnacle or Pursuit + Cobra following Prowl. Best control of large crabgrass occurred with treatments involving Roundup Ultra or Assure II Post.
Soybean injury occurred as leaf necrosis with treatments involving Cobra and as slight stunting with Pursuit + Pinnacle following Prowl. Drouth stress caused low soybean yields averaging only 11.9 bu/a across herbicide treatments and resulted in within-site yield variation. Consequently, no significant differences in soybean yield occurred among herbicides. Untreated check plots were not harvestable by combine because of extreme weed infestation and would have had an estimated yield of less than 3 bu/a.   2 PRE= preemergence to soybeans and weeds on June 11; POST = postemergence to 6 to 32 in. pigweeds and 1.5 to 7 in. large crabgrass on July 14; POST 2 = second postemergence application to 2 to12 in. pigweeds on July 15 (treatment 14) or 2 to 18 in. pigweeds and 1 to 8 in. large crabgrass on August 11 (treatments 11 and 12). 3 Lacg =large crabgrass. 4 Paam = Palmer amaranth. Weed population included some redroot pigweeds.

Summary
Late postemergence (LP) and sequential (SEQ) applications of three Roundup Ultra rates were compared with standard preemergence (PRE) and postemergence herbicide treatments in 8-inch and 30-inch row soybean. Initial dry conditions adversely affected PRE Prowl. Squadron provided excellent PRE control of pigweeds as well as a level of large crabgrass control similar to that achieved with single, LP applications of Roundup Ultra. All Roundup Ultra treatments provided excellent control of pigweeds with generally small differences among rates. SEQ tended to provide better results than LP Roundup Ultra, particularly on large crabgrass. Roundup Ultra rates performed similarly in both LP and SEQ applications. Pigweed control with LP Pursuit was inferior to that with Roundup Ultra because of unusually large weed size at application. Row spacing had no observable effect on weed control. Soybean yields were very low and variable because of drouth stress. Among treatments with Roundup Ultra alone, 30-inch rows produced 3.9 bu/a more than 8-inch rows. This yield advantage for 30-inch rows was 3.7 bu/a more with SEQ than with LP Roundup Ultra.

Introduction
Roundup has been used widely for nonselective weed control in fallow periods between crops and in no-till production prior to crop emergence. The development of Roundupresistant soybean makes it possible to use this herbicide for broad spectrum postemergence weed control during the growing season. Questions remain concerning the optimum rate and time of Roundup application as well as the impact of row spacing on weed control efficacy. This study focused on these issues, the use of a preemergent herbicide ahead of Roundup postemergence, and the relative effectiveness of the Roundup program versus a total preemergence weed control program or standard postemergence treatments.

Procedures
The experiment site was cropped to oats in 1997. The soil was a Smolan silt loam with pH 6.7 and 2.4% organic matter. Pigweed and large crabgrass seed were broadcast prior to the last preplant tillage operation to promote uniformity of weed populations. Asgrow 3601 RR + STS and Asgrow 3704 STS soybean were planted on June 10, 1998, in 8-inch and 30-inch rows at 142,000 and 154,000 seeds/a, respectively. Seedbed condition was excellent.
PRE applications, just after planting, as well as postemergence treatments, were made in 20 gal/a of water with XR8003 nozzles at 18 or 20 psi. Subsequent treatments were scheduled for early postemergence (EP) and LP, corresponding to weed heights of 1 to 3 inches and 4 to 6 inches. SEQ treatments were planned for two successive applications at EP.
Because of weather interference, EP was never applied. LP as well as the first of the SEQ treatments were made to 3-to 27-inch pigweeds and 1.5-to 8-inch large crabgrass. The second application in SEQ treatments was made to 4-to 9-inch pigweeds and 1.5-to 7-inch tall large crabgrass.
All treatments were replicated three times. Crop injury and weed control were rated at various times during the growing season. Soybean was harvested on October 27, 1998.

Results
Three weeks of dry weather preceded planting. Although soil physical condition at planting was excellent, soil moisture was insufficient for soybean emergence. Hard rains 11 days later caused soil crusting and resulted in uneven soybean stands in narrow-row plots. Rainfall totaled 3.01 inches for the period 11 to 15 days after planting. Soybean populations averaged approximately 45,740 plants/a in 8-inch rows and 99,320 in 30-inch rows. Dense pigweed (mixture of redroot and Palmer amaranth) and large crabgrass populations developed. In late June, densities of 4 to 10 pigweeds/sq ft and 4 to 33 large crabgrass plants/sq ft were observed across the site.
Unforecasted heavy rains in early July prevented the scheduled EP Roundup Ultra application. A prolonged hot and wet period that followed allowed pigweed growth to explode. Consequently, meaningful timing comparisons with Roundup Ultra were limited to LP and SEQ treatments.
No apparent differences occurred between redroot pigweed and Palmer amaranth responses to herbicides.
Because of their relative distribution across the site, both were included in a single control evaluation for pigweeds. PRE Squadron gave excellent control of pigweeds and fair to good control of large crabgrass (Table 12). However, PRE Prowl was not effective in controlling these species under existing conditions. As a result, Prowl did not provide much assistance in holding down weed development ahead of either Roundup Ultra or Pursuit postemergence applications.
All Roundup Ultra treatments provided excellent control of pigweeds and good to excellent control of large crabgrass. Roundup Ultra rates of 1.5 or 2.0 pt/a tended to be more effective than 1 pt/a on these species, but differences among rates were generally small. The effect of Roundup Ultra application time on pigweeds was relatively small but significant. Timing effect was more notable in large crabgrass control. In both cases, SEQ providing better results than LP Roundup Ultra. No interactions occurred between Roundup Ultra rate and time of application. Row spacing had no observable effect on weed control. Pursuit following PRE Prowl did not provide acceptable pigweed control because of late application.
No herbicide injury of consequence was observed. Drouth stress caused low soybean yields averaging only 9.4 bu/a across herbicide treatments. Untreated check plots were not harvestable by combine because of extreme weed infestation. Among treatments with Roundup Ultra alone, the only significant main effect on yield was that of row spacing, with 30inch rows producing 3.9 bu/a more than 8-inch rows (Table13). The time of application by row spacing interaction was significant in that the yield advantage for 30-inch rows was 3.7 bu/a more with SEQ than with LP Roundup Ultra treatments. Lowest yields in 30-inch rows occurred with LP Roundup Ultra at 1 pt/a alone or following Prowl. Yields of non-Roundup Ready soybean with Squadron or Prowl Pre plus Pursuit LP were inferior to those of Roundup Ready soybean with the best Roundup Ultra treatments.
This project was funded partially by the Kansas Soybean Commission.  2 Pre = preemergence to soybeans and weeds on June 10. LP = Late postemergence to 3 to 27-in. pigweeds and 1.5 to 8-in. large crabgrass on July 14; Seq = two sequential applications of base herbicide rate: LP followed by later postemergence treatment to 4 to 9-in. weeds and 1.5 to 7-in. large crabgrass on August 11. 3 Lacg = large crabgrass. 4 Mixed population of redroot pigweed and Palmer amaranth.

Introduction
Spring oats can serve a useful roll as a rotational crop when weather or soil conditions prevent implementation of a particular crop sequence. They also can provide a significant grain or forage resource in a diversified croplivestock operation. Performance tests with oats were conducted here to evaluate both forage and grain yield potential and other agronomic characteristics of varieties currently available.

Procedures
Seventeen spring oat varieties were seeded on March 3, 1998 at 64 lb/a on a site cropped to winter wheat in 1997. Experimental design was a split plot with four replications.
Fertilizer (90 lb/a of N and 32 lb/a of P 2 O 5 ) was broadcast and incorporated before planting. Bronate at 1.5 pt/a was applied for weed control on May 7, 1998. Plots were harvested for forage on June 16 and for grain on July 1.

Results
Cold and wet weather followed oat planting. Emergence occurred in late March. Brawn had only 73% stand, but the remaining varieties had 92 to 100% stands. Warm, dry weather in May and June was unfavorable for oat grain development. Also, barley yellow dwarf disease had a significant impact, with severe symptoms in some varieties. Jerry, Rio Grande, and Eli were moderately susceptible to susceptible and had the poorest BYVD scores (Tables 14, 15).
Lodging and shattering were minor. Top forage yields of 2.21 to 2.36 ton/a dry matter were produced by Il862081, Prairie, and Rodeo. These varieties also had the highest grain yields, which averaged only about 56% of their 1997 yields. Lowest forage and grain yields were recorded for Brawn and Eli.

IRRIGATION AND NORTH CENTRAL KANSAS EXPERIMENT FIELDS Introduction
The 1952 Kansas legislature provided a special appropriation to establish the Irrigation Experiment Field in order to serve expanding irrigation development in north-central Kansas. The original 35-acre field was located 9 miles northwest of Concordia. In 1958, the field was relocated to its present site on a 160-acre tract near Scandia in the Kansas-Bostwick Irrigation District. Water is supplied by the Miller Canal and stored in Lovewell Reservoir in Jewell County, Kansas and Harlen County Reservoir at Republican City, Nebraska. A 5-acre site in the Republican River Valley on the Mike Brazon Farm also is utilized for irrigated-crop research. In 1997, there were 125,000 acres of irrigated cropland in north-central Kansas. Current research on the field focuses on managing irrigation water and fertilizer in reduced-tillage and crop-rotation systems.
The 40-acre North Central Kansas Experiment Field, located 2 miles west of Belleville, was established on its present site in 1942. The field provides information on factors that allow full development and wise use of natural resources in north-central Kansas. Current research emphasis is on fertilizer management for reduced-tillage crop production and management systems for dryland production corn, sorghum, and soybean.

Soil Description
The predominate soil on both fields is a Crete silt loam. The Crete series consists of deep, welldrained soils that have a loamy surface underlain by a clayey subsoil. These soils developed in loess on nearly level to gently undulating uplands. The Crete soils have slow to medium runoff and slow internal drainage and permeability. Natural fertility is high. Available water holding capacity is approximately 0.19 inch of water per inch of soil.

Weather Information
The 1998 growing season was characterized by above-normal rainfall in April but belownormal rainfall in May and June (Table 1). Rainfall in July was ideal but below normal in August and September. Temperatures were near normal throughout the spring and early summer but were much above normal in August and September.

Summary
When averaged over nitrogen (N) rates, 1982-1995 yields were 23 bu/a greater in sorghum rotated with soybeans than in continuous sorghum. When no N was applied, rotated sorghum yielded 32 bu/a more than continuous sorghum. In the continuous system, grain sorghum yield continued to increase with increasing N rate up to 90 lb/a. In the soybean rotation, sorghum yields increased with increasing N rate only up to 60 lb/a. When averaged over N rate, no-tillage grain sorghum rotated with soybeans reached mid-bloom 7 days sooner than continuous grain sorghum. Two knife-applied N sources (anhydrous ammonia and 285 UAN) were evaluated during [1982][1983][1984][1985][1986][1987][1988][1989]. No grain sorghum yield differences resulted from N source. The 17year soybean yield average was 36 bu/a. Soybean yields were not affected by N applied to the previous grain sorghum crop. In 1996, four additional N rates (120, 150, 180, and 210 lb/a) were added to the experiment. When averaged over the period 1996-1998, yields were greater in the rotated system than in the continuous sorghum at all levels of N. Yields in the continuous system continued to increase with increasing N rate up to 90 lb/a. Yields in the rotated system were maximized with application of 60 lb/a N.

Introduction
Crop rotations were necessary to maintain soil productivity before the advent of chemical fertilizers. Biological fixation of atmospheric N is a major source of N for plants in natural systems. Nitrogen fixation through legume-Rhizobium associations is utilized extensively in agricultural systems. Using a legume in a crop rotation system can reduce the N requirement for the following nonlegume crop. Other benefits of legume rotations include breaking disease and insect cycles, helping weed control programs, and decreasing the toxic effects of crop residues. This study evaluates N rates for continuous grain sorghum and grain sorghum grown in annual rotation with soybeans in a no-tillage production system.

Procedures
This study was established in 1980 at the North Central Kansas Experiment Field, located near Belleville, on a Crete silt loam soil. Data are reported starting in 1982. Treatments included cropping system (continuous grain sorghum and grain sorghum rotated with soybeans) and N rates (0, 30, 60, and 90 lb/a). In 1982-1989, the two N sources anhydrous ammonia and ureaammonium nitrate solution (28% UAN) were evaluated. Both N sources were knife applied in the middle of rows from the previous year's crop. After 1989, anhydrous ammonia was used as the sole N source. In each year, N was knife applied 7-14 days prior to planting. Grain sorghum was planted at the rate of 60,000 seed/a, and soybeans were planted at the rate of 10 seed/ft. in 30-inch rows. Soybean yields were not affected by N applied to the previous sorghum crop and, therefore, are averaged over all N rates. In 1996, four additional N rates (120, 150, 180, and 210 lb/a were added to the experiment in order to further define N response.

Summary
Field studies were conducted at the Irrigation Experiment Field, located near Scandia, on a Crete silt loam soil. Starter fertilizer (7-21-7) included two sources of potassium (K): sulfate of potassium (SOP) and potassium chloride KCL). The test also included two placement methods (in-furrow with the seed and 2 inches to the side and 2 inches below the seed at planting) and five application rates (50, 75, 100, 150, 200 lb/a of 7-21-7). A no-starter check plot also was included in the experiment. Sulfur rates were balanced so that all plots received the same amount, regardless of K source. Experiments were conducted with both corn and soybeans. For the corn experiment, nitrogen (N) as ureaammonium nitrate solution (28% UAN) was applied immediately after planting so that all plots received 200 lb/a N. Soybeans received no additional N. When liquid 7-21-7 starter fertilizer containing KCL was placed in-furrow, grain yield, plant stand, and early season dry matter were reduced in both the corn and soybean experiments. In the corn experiment, starter fertilizer containing KCL applied at the 100 lb/a rate reduced yield by 12 bu/a compared to the same rate applied 2 x 2. Corn yield was reduced 40 bu/a when starter fertilizer containing KCL was applied in-furrow at the 200 lb/a rate. When starter fertilizer containing SOP was placed infurrow, no yield reduction was seen except at the 200 lb/a rate. When starter fertilizer containing KCL as the K source was placed in-furrow with soybean seed, yields and plant populations were reduced regardless of rate. Yields and populations of soybean declined when in-furrow rates of 7-21-7 starter fertilizer containing SOP exceeded 100 lb/a.

Procedures
This irrigated ridge-tilled experiment was conducted at the Irrigation Experiment Field, near Scandia, on a Crete silt loam soil. Analysis by the KSU Soil Testing Lab showed that in the corn experimental area, initial soil pH was 6.4; organic matter content was 2.4%; and Bray-1 P and exchangeable K in the top 6 inches of soil were 43 and 380 ppm, respectively. In the soybean area, soil pH was 6.5, organic matter content was 2.2%, Bray-1 P was 45 ppm, and exchangeable K was 350 ppm in the top 6 inches of soil. The experimental design was a randomized complete block with three factors. Both the corn and soybean tests included starter fertilizer (7-21-7) made with two K sources applied either in-furrow or 2 x 2 at five different rates. A no-starter check also was included. The two sources of K were sulfate of potassium (SOP) and potassium chloride (KCL). A liquid 7-21-7 fertilizer was made using ammonium polyphosphate (10-34-0) and either SOP or KCL and was applied at 50, 75, 100, 150, and 200 lb/a. Sulfur was balanced so that all plots received the same amount. Nitrogen as 28% UAN also was balanced on all corn plots to give a total of 200 lb/a. The soybean experiment received no additional N. The corn hybrid Dekalb 632 was planted on 22 April at the rate of 31,000 seed/a. The soybean variety Dekalb CX370RR was planted on 12 May at the rate of 200,000 seed/a in 30-inch rows. Both the corn and soybeans were grown in a ridge-tillage production system. Stand counts were taken 3 weeks after emergence. Whole plant samples (20 plants/plot) were taken at the V-6 stage. The center two rows of each four row plot were harvested for yield determination.

Results
Corn grain yields were affected by a starter fertilizer x placement x rate interaction (Table 5). When SOP was used as the K source in the 7-21-7 starter fertilizer and placed in-furrow with the seed, grain yields were not different than those with fertilizer placed 2 x 2, except at the 200 lb/a rate. When 200 lb/a of 7-21-7 starter fertilizer was applied in-furrow, yields were 14 bu/a less than when the same rate was applied 2 x 2. Plant population and whole-plant dry weight at the V-6 stage were reduced by an in-furrow application of 200 lb/a 7-21-7 containing SOP. When KCL was used as the K source for 7-21-7 starter fertilizer placed in-furrow, yields were reduced at all application rates compared to the 2 x 2 placement. A 50 lb/a in-furrow application of 7-21-7 containing KCL reduced grain yield by 12 bu/a and plant population by 3,198 plants/a. At the 200 lb/a rate, yields were reduced by 40 bu/a with in-furrow application of starter fertilizer containing KCL.
When starter fertilizer containing KCL was placed in-furrow with the soybean seed, yield and plant population were reduced regardless of rate (Table 6). At the 50 lb/a rate of 7-21-7 containing KCL, yields were 9 bu/a less when fertilizer was placed in-furrow as compared to 2 x 2. At the 200 lb/a rate of 7-21-7 placed infurrow, yields were reduced 21 bu/a. Yields and population of soybean declined when in-furrow rate of 7-21-7 starter fertilizer containing SOP exceeded 100lb/a.
In both corn and soybean experiments, infurrow applications of starter fertilizer containing SOP resulted in less salt injury than those containing KCL. Even at low application rates, in-furrow applications of fertilizer containing KCL reduced plant population and yield.  *No-starter check plot was not included in statistical analysis. **7-21-7 Starter fertilizer made using sulfate of potassium (SOP) as the K source. ***7-21-7 Starter fertilizer made using potassium chloride (KCL) as the K source. **** Three-way interaction LSD (placement x rate x K source.

Summary
In previous research at the North Central Kansas Experiment Field, we found that some corn hybrids grown under reduced-tillage conditions responded to starter fertilizer containing nitrogen (N) and phosphorus (P) and others did not. Little information is available concerning variability in responsiveness among corn hybrids to starter fertilizer containing a complete complement of nutrients. This study evaluated the responses of four corn hybrids (Pioneer 3563, Pioneer 3346, Dekalb 591, and Dekalb 646) to starter fertilizer combinations containing N, P, potassium (K), sulfur (S), and zinc (Zn). The experiment was conducted on a Carr sandy loam soil located in the Republican River Valley near Scandia, KS. Starter fertilizer containing N and P increased V-6 stage dry weight compared to the no-starter check treatment for all corn hybrids tested. Grain yield of two of the corn hybrids (Pioneer 3563 and Dekalb 646) did not respond to starter fertilizer, regardless of elemental composition. Starter fertilizer containing N and P increased grain yield of Pioneer 3346 and Dekalb 591 by 24 and 15 bu/a, respectively, compared to the no-starter check. The addition of 10 lb/a S to the starter fertilizer mix resulted in further yield increases for Pioneer 3346 and Dekalb 591. Additions of K and Zn to the starter fertilizer mix did not increase yield benefit.

Procedures
The ridge-tilled, furrow-irrigated corn study was conducted on a farmer's field in the Republican River Valley near Scandia, KS on a Carr sandy loam soil. Analysis by the KSU Soil Testing Lab showed that initial soil pH was 7.2, organic matter content was 1%, Bray-1 P was 21 ppm, and exchangeable K was 280 in the surface 6 inches of soil. The site had been in ridge-tillage for 4 years prior to the establishment of this study. Corn hybrids used were: Pioneer 3563, Pioneer 3346, Dekalb 591, and Dekalb 646. The liquid starter fertilizer treatments used in both experiments are given in Table 7. Starter fertilizer was applied 2 inches to the side and 2 inches below the seed at planting. Corn was planted on 23 April at the rate of 30,000 seed/a. Immediately after planting, N was balanced on all plots to give a total of 200 lb/a. The N source used in the experiment was urea-ammonium nitrate solution (28% UAN), the P source was ammonium polyphosphate (10-34-0), the K source was KCL, the S source was ammonium thiosulfate, and the Zn source was a liquid Zn-NH 3 complex.

Results
Starter fertilizer containing N and P improved V-6 stage dry matter production of all hybrids tested (Table 8). Additional response was achieved when the starter fertilizer mix contained S. Additions of K and Zn did not result in any further dry matter increase.
Two hybrids (Pioneer 3563 and Dekalb 646 ) did not show any yield response to starter fertilizer (Table 9). This is consistent with the results of previous studies using these hybrids. Starter fertilizer containing N and P increased grain yield of Pioneer 3346 and Dekalb 591 by 24 and 15 bu/a, respectively. Addition of S to the starter fertilizer mix resulted in further yield increases of 12 bu/a for Pioneer 3346 and 11 bu/a for Dekalb 591.
Starter fertilizer improved early-season growth in all hybrids included in the experiment. However, this did not translate into increased grain yield for all hybrids. Results of this work suggest that responses to starter fertilizer can be economical for some hybrids even on soils not low in available nutrients, particularly when corn is planted in a high-residue production system.

Introduction
Increased marketing opportunities and profit potential have created interest among area farmers to convert acres to white food-corn production. White corn hybrids have distinctive genetic traits for specific end-use purposes. Dry millers grind food corn into a range of degermed corn products including flaking grits, corn flour, brewer grits, germ, and meal. These products are used for breakfast cereals and snack foods. The best quality dry-milling corn has large-sized kernels, low kernel-size variability, harder kernel texture, and higher protein content. Harder type dent is desired because dry millers prefer larger flaking grits vs. a kernel that is easily crumbled. Breakfast cereal manufacturers pay a premium for large pieces of unbroken corn endosperm that can produce larger corn flakes. Wet millers separate corn into basic components (starch, protein, fiber, and germ), with the principal component being starch. The general qualities for wet milling corn include low moisture, no mold or mycotoxins, minimum broken kernels, and low incidence of stress cracks. Masa millers cook the food corn with lime in order to soften the kernel and remove the pericarp. This process is known as nixtaamalization and the resulting corn is known as nixtamal. The nixtamal is ground with stones into masa which then is made into tortillas, tortilla chips, or other Mexican snack foods.
This test is one of 13 locations included in a regional white corn performance test conducted by Dr. L. L. Darrah with the USDA-ARS at the University of Missouri-Columbia. The 1998 test included 30 white corn hybrids and 3 yellow hybrid checks.

Procedures
Anhydrous ammonia was applied on 18 April at the rate of 200 lb/a. The test was planted on 22 April at the rate of 30,000 plants/a. Starter fertilizer ( 30 lb N + 30 lb P 2 O 5 /a) applied 2 inches to the side and 2 inches below the seed at planting. Furrow-irrigations were applied on 1 July, 8 July, and 20 July. Three inches of water were applied at each irrigation. The test was harvested on 20 October using a modified E Gleaner combine.

Results
Overall grain yield in this test was 171 bu/a and ranged from 138 to 199 bu/a (

Summary
Eighteen soybean varieties in maturity Groups I-IV were grown in rotation with grain sorghum. Yields of Group II soybeans were equal to yields of Group III and superior to yields of Group IV. Yields of Group I soybeans were not as good as those of Group III but still greater than those of Group IV. Late Group I and early Group II soybeans matured 25 and 19 days earlier, respectively, than Group IV soybeans, thus allowing for earlier harvest and a longer fall period of soil water recharge. Seed quality was poorer in Group I and Group II soybeans than in Groups III and IV.

Introduction
The resent passage of new farm legislation gives farmers the flexibility to plant the most profitable crop rather than plant to maintain base acres of a farm program crop. This encourages crop rotations. Opportunities exist for expanding soybean acres in central Kansas. Grain sorghum is grown on a large number of dryland acres in central Kansas. In the past, much of this sorghum was grown either in a continuous system or in occasional rotation with wheat.
A dryland grain sorghum-soybean rotational study was established at the North Central Kansas Experiment Field at Belleville in 1981. Results show that yield of grain sorghum was 25% greater when grown in annual rotation with soybeans. Nitrogen fertilizer required to achieve maximum sorghum yield was reduced by 30 lb/a by rotation with soybeans. Soybean yield averaged over the period 1982-1997 was 35 bu/a. Soybean yields ranged from a low of 12 bu/a to a high of 58 bu/a. Producer acceptance of soybean production in the 24-to 28-inch annual rainfall area of Kansas has been somewhat slow. This may be due to large yearto-year variation in soybean yields and the perception that sorghum following soybean may yield less because of water use by soybean during the preceding crop year. The traditional late Group III and early Group IV maturity soybeans grown in the area can use significant amounts of water in August and early September. Earlier maturing soybeans (late Group I through early Group III) use the maximum amount of water earlier in the growing season when it is more likely to be available, thus potentially providing greater year-to-year yield stability and leaving a longer period for soil water recharge for the following crop.
This research is designed to investigate the yield potential, seed quality, and water use of early maturing soybeans and to assess the effects of soybean maturity group on yield of a following grain sorghum crop.

Procedures
Research was conducted at the North Central Kansas Experiment Field located near Belleville on a Crete silt loam soil. The experiment consisted of 18 soybean varieties that range in maturity from late Group I to early Group IV. Soybean varieties included in the experiment are listed in Table 11. The soybeans were grown in rotation with grain sorghum. A continuous grain sorghum treatment also was included. Soybeans were planted on 15 May at the rate of 10 seed/ft into grain sorghum stubble without additional tillage. Group I and II soybeans were harvested on 28 September, and Groups III and IV were harvested on 14 October. At maturity, 10 plants from each plot were selected at random for yield component analysis and plant height measurements. Seed samples were tested for germination by the Kansas Crop Improvement Association Seed Testing Lab. Gravimetric soil water measurements were made at planting and again at maturity to a depth of 36 inches. The continuous sorghum and sorghum/soybean rotation blocks used in this experiment were established on the field in 1996.

Results
Rainfall in July was above average, but August and September were much drier than normal. Yields of all three Group I varieties were greater than yields of varieties in Group IV (Table 13). Seed yields of later maturing soybeans probably were reduced by the lateseason drought. When averaged over the three varieties in each category, yield of Group II soybeans was equal to yield in Group III (Table  14). Yield of Group I soybeans was not as good as that of Group III but was still better than that of Group IV. Late Group I and early Group II soybeans matured 25 and 19 days earlier than Group IV soybeans, respectively. Earlier soybean harvest allows producers to spread out fall harvest work load and plant wheat in a timely manner. Soybeans in Group II used 2 inches less water during the growing season than soybeans in Group IV. Soybeans in Group I were shorter in height than soybeans in latter groups. The short stature limited pod sites and reduced yields. Seed quality was poorer in Group I and II soybeans than in Group III and Group IV. Seed of early season varieties mature during a time when temperatures are still very warm, whereas seed of later maturing varieties matures in September when temperatures are normally cooler.

Summary
In 1997, yield of grain sorghum was reduced by 25 bu/a by delaying planting until late June. Yield of grain sorghum was improved by planting in narrow rows at a late planting date, but yields were not affected by row spacing at a normal planting date. In 1998, yield was not affected by planting date. Yield of the full-season hybrid Pioneer 8310 was reduced by narrower row spacing. Yields of early and mid-season hybrids were not affected by row spacing. When grain sorghum is planted in late May, yields are not improved by narrowing row spacing. When planting is delayed past the optimum time, yields can be improved in some years by planting in rows narrower than the conventional 30 inches.

Introduction
Crop density can be manipulated by varying row width or within-row density. Densities can be maintained, but the development of cover and the pattern of crop water use are altered by planting crops in wider rows. These effects operate through interaction between root systems within the soil volume available for rooting. Use of soil stored moisture by annual crops depends on the rate at which roots expand into the available soil volume. Planting pattern can be manipulated to control the time when the crop reaches moisture. Uniform spacing (narrow row width with longer intervals between plants in the same row) allows for the shortest time for roots to reach the perimeter of the available space. Crowding plants in wide rows restricts early water use and crop growth. Water use is distributed over longer periods. Spacing arrangements serve as a practical means for managing the performance of root systems.
Production strategies to efficiently use stored soil water and limited seasonal precipitation include choice of hybrid, planting date, plant population, and row width.

Procedures
A dryland experiment was initiated in 1997 at Scandia to determine the effect of planting date (mid-May and mid-June); row spacing (15 and 30 inches); and plant population (30,000, 60,000, and 90,000 plants/a) on grain sorghum yield. In 1997, planting dates were 20 May and 20 June. Plots in both row spacings were planted with a John Deere 71 unit planter. Plots were overplanted and thinned to desired populations. In 1998, the population variable was replaced by a hybrid maturity variable. The experiment consisted of two planting dates; two row spacings ( 15 and 30 inches); and three hybrids (Pioneer 8699, Pioneer 8500, and Pioneer 8310). Planting dates in 1998 were 21 May and 17 June. Plots were planted at the uniform rate of 60,000 seed/a.

Results
When averaged over row spacing and plant populations, grain sorghum yields in 1997 were 25 bu/a greater for the May planting than for the June planting (Table 15). Row spacing did not affect grain yield at the May planting date, but at the June planting date, yield in 15-inch rows was 29 bu/a greater than that in 30-inch rows. Temperatures in August were lower than normal, which slowed crop development. An earlier than normal frost also was recorded. Early-season crop growth rate is often greater in narrow rows than in wide rows because of more efficient light interception and greater soil water use. This early-season growth advantage in the 15-inch rows helped overcome some of the disadvantages of late planting.
The growing season in 1998 was warmer and longer than normal. Growing degree units in August and September were above normal. Grain sorghum yields were not affected by planting date (Table 16). Row spacing did not affect the yields of Pioneer 8699 or Pioneer 8500, but yield of Pioneer 8310 was reduced in narrow rows at both planting dates. Pioneer 8310 is a tall, late-maturing hybrid and may not be well suited to narrow-row production.

Summary
Studies were initiated to investigate the effects of row spacing and plant population on corn grain yield. Two sites (one dryland and one irrigated) were located in Republic County and one irrigated test was located at the Sandyland Experiment Field near St. John. The test consisted of three row spacings (30, 20, and 15 inches) and four plant populations (20,000, 26,000, 32,000, and 36,000 plants/a). Growing season rainfall was over 3 inches below normal at the Belleville site, but July rainfall was ideal. The test averaged 154 bu/acre. Yields were not affected by either row spacing or plant populations. Stands were erratic at the Larson Farm, and the test was abandoned at this site. At the St. John location, yield in the 15-and 20inch rows was 10 bu/a greater than that in 30inch rows. Response to plant population was inconsistent.

Introduction
Early in the century, corn was grown in rows spaced about 40 inches apart to accommodate horse-drawn equipment and later mechanized equipment and post-emergent cultivation practices. The development of effective chemical herbicides and narrow row equipment has given producers the option of reducing row spacing. With the development of corn headers for combines capable of harvesting 15-to 20-inch rows, interest in narrow-row corn spacing (less than 30 inches) is being renewed among producers in many regions. Recently published information on narrow row spacings is limited. Most narrow-row corn research has been conducted in the upper Midwest region and has compared only two row spacings (conventional 30 inch to one other narrower spacing). Information concerning narrow-row spacing effects on corn grain yields is needed under Kansas conditions. This research compares conventional 30-inch rows to 15 two narrower rows at four plant populations.

Procedures
Experiments were conducted at the North Central Kansas Experiment Field near Belleville, the Richard Larson Farm at Scandia (both sites were located in Republic County), and the Sandyland Experiment Field located at St. John. The soil at Belleville is a Crete silt loam, and the soil at the Larson Farm is a Carr sandy loam. The experiment at St. John was conducted on a Pratt loamy fine sand. The Belleville site was dryland. The Larson and St. John locations were both center-pivot irrigated. The experiment consisted of three row spacings (30-, 20-, and 15-inch rows) and four plant populations (20,000, 26,000, 32,000, and 36,000 plants/a). In addition, the experiments at Belleville and St. John included two corn hybrids (Pioneer 3394 and Pioneer 3325), but only Pioneer 3394 was used at the Larson Farm. A John Deere 71 Unit planter was used at all locations. Plots consisted of four 30-, six 20-, or eight 15-inch rows. All plots were overplanted and thinned to the desired populations.

Results
Growing season rainfall was below normal at the Belleville location, but July precipitation was above normal. Although yields were very good, there was no response to row spacing or plant population (Table 17). When averaged over the 3 years of the experiment, 30-inch rows yielded slightly better than narrower row spacings.
When averaged over the 2 years of the experiment at the Larson Farm, narrowing row spacing improved yields by 17 bu/a (Table 18). However, this represents less than a 10% increase in yield over the conventional 30-inch rows.
Yields at the Sandyland Expt. Field averaged 158 bu/a (Table 19). Yields in 15-inch and 20-inch rows were 10 bu/a greater than those in 30-inch rows. Little yield response was seen in populations above 26,000 plants/a.
Although at some locations in some years, yields were improved by planting in row spacings less than 30 inches, the responses have not been consistent or large in magnitude. Generally, yield responses to narrow row spacings have been 10% or less.

Summary
Individual operations and weather conditions in north central Kansas influence wheat planting dates. Increased double-cropping of wheat after a summer crop has resulted in an increase in the number of acres planted in mid to late October. A study was designed to assess the performance of two wheat varieties from Kansas State University, Jagger and 2137, at several planting rates and planting dates in 1995 and 1996 in north central Kansas. Seeding rates of 30, 60, 90, and 120 lbs of seed/a were used at three planting dates (approximately Sept. 20, Oct. 5, and Oct. 20). As planting was delayed, heads/a and yield decreased as the result of a dry winter. Several warm periods followed by extreme cold in February and March of 1996 damaged Jagger, which broke dormancy during this period. Jagger yields were 20 bu/a lower than those of 2137. Spring tillers accounted for a large portion of Jagger's yield. This resulted in lower test weights than 2137, because the grain from the late tillers developed during hotter temperatures in late June. These results illustrate the importance of planting winter wheat in north central Kansas so that adequate fall growth can be achieved. Such growth aids the plant in winter survival and spring regrowth.

Introduction
Planting date selection for wheat in north central Kansas often must be balanced between early planting to achieve better stands and fall growth and late planting to reduce the effects of Hessian fly, cheat, and take-all root rot. More intensive cropping systems have resulted in more acres of double-cropped wheat after a summer row crop. As a result, the number of wheat acres being planted in mid-to-late October also has increased.
Seeding rates for wheat vary less than planting dates. Recommended wheat-seeding rates for northeast Kansas are currently from 60 to 120 lbs/a. As wheat planting is delayed, plant growth and tiller production are reduced as a result of cooler temperatures. It is reasonable to assume that increasing seeding rates as planting is delayed should compensate for reduced full tiller production and increase yields.
The objectives of this study were to evaluate wheat yields at three planting dates and four seeding rates in north central Kansas.

Procedures
This study was conducted at the North Central Experiment Field at Belleville, KS. Treatments consisted of two varieties (Jagger and 2137); four seeding rates, 30, 60, 90, and 120 lbs/a; and three planting dates (listed in Table 20). A factorial arrangement of treatments in a randomized complete block design with three replications was used. All plots were 300 sq ft in size.
Grain yield, test weight, and moisture were determined in July in 1996 and 1998. Yields were adjusted to 12.5% moisture.

Results
As expected, all three main effects (planting date, seeding rate, and variety) affected grain yields (Table 21). Grain yields increased as seeding rates increased from 30 to 120 lbs/a, but yields at 90 and 120 lbs/a were not significantly different (Table 22).
Growing condition differences between the 2 years of the study affected grain yield differently each year as indicated by the significant planting date by year and variety by year interactions ( Table 21).
As planting was delayed in 1995, grain yields declined (Table 23). This response was the result of dry conditions during October through December reducing late-season growth. When planting was delayed from late September to early October in 1997, grain yields were not affected (Table 23). However, delaying planting until mid-October reduced yields by 38 bu/a.

A series of warm/cold cycles in February and
March 1996 reduced grain yields of Jagger in 1996 (Table 24). In 1998, both varieties produced similar grain yields.

Conclusions
Seeding rates of 90 and 120 lbs/a produced similar yields across two growing seasons. Delaying planting until mid-October reduced yields over 40% compared to an early October planting date. A late-September planting date produced the maximum yields when October and November received below average rainfall. Performances of Jagger and 2137 were similar under normal conditions.

Introduction
The Kansas River Valley Experiment Field was established to study how to manage and use irrigation resources effectively for crop production in the Kansas River Valley. The Paramore Unit consists of 80 acres located 3.5 miles east of Silver Lake on US 24, then 1 mile south of Kiro, and 1.5 miles east on 17th street. The Rossville Unit consists of 80 acres located 1 mile east of Rossville or 4 miles west of Silver Lake on US 24.

Soil Description
Soils on the two fields are predominately in the Eudora series. Small areas of soils in the Sarpy, Kimo, and Wabash series also occur. The soils are well drained, except for small areas of Kimo and Wabash soils in low areas. Soil texture varies from silt loam to sandy loam, and the soils are subject to wind erosion.
Most soils are deep, but texture and surface drainage vary widely.

Weather Information
The frost-free season was 33 days longer than the 173-day average. The last 32E F frosts in the spring were on April 18 at the Rossville Unit and on April 19 at the Paramore Unit (average, April 21), and the first frost in the fall was on November 11 (average, October 11). Precipitation was above normal in the fall of 1997; below normal from January through May and in August; and above normal in June, July, and September (Table 1). Precipitation totals for October, 1997 through September, 1998 were 7.59 and 7.46 inches below normal for the Paramore and Rossville Units, respectively. Corn and soybean yields were both lower than normal.

Summary
Sixteen herbicides were evaluated in a preemergence test (PRE) and 20 were evaluated in a postemergence test (POST). Slight injury was obtained with several POST treatments but had no effect on yield. All treatments, except one, in both tests gave greater than 80% control of large crabgrass, Palmer amaranth, and common sunflower. Untreated checks yielded only 65 and 85 bu/a in the PRE and POST tests, respectively.

Introduction
Weed competition can limit crop yields. Chemical weed control and cultivation have been used to control weeds in row crops. Two corn herbicide tests were conducted, a preemergence test (PRE) and a postemergence test (POST). These studies included several of the newer herbicides for use on corn. The major weeds were large crabgrass (Lacg), Palmer amaranth (Paam), and common sunflower (Cosf).

Procedures
Both tests were conducted on a Sarpy fine sandy loam soil previously cropped to soybeans with a pH of 6.8 and an organic matter content of 1.1%. Pioneer Brand 33R78 and Asgrow 701 IT corn hybrids were planted at 26,200 seeds/a in 30-inch rows on April 23 and May 4 for the PRE and POST tests, respectively. Anhydrous ammonia at 150 lbs N/a was applied preplant, and 10-34-0 fertilizer was banded at planting at 120 lbs/a. Herbicides were applied: preemergent (PRE) -May 4 and early postemergent (EP) -May 27 in the PRE test and preemergent (PRE) -April 24, early postemergent (EP) -May 22, and mid-postemergent (MP) -June 9 in the POST test. Plots were not cultivated. Reported crop injury ratings were made on May 27 for the PRE test and May 30 for the POST test. Ratings reported for weed control were made on June 11 for the PRE test and June 19 for the POST test. The first significant rainfall after PRE herbicide application was on May 11 (0.78 inches). Plots were harvested on September 25 using a modified Gleaner E combine.

Results
In the PRE test, the greatest corn injury was observed with the Balance + Axiom treatment ( Table 2). All treatments gave greater than 80% control of Lacg and Paam. All treatments except Axiom + Balance + Atrazine gave greater than 80% control of Cosf. This treatment had only 1.0 oz/a Balance and 1.11 lb/a Atrazine 90DF. The treatment of Balance + Atrazine, 1.25 oz/a + 1.39 lb/a, resulted in 95% Cosf control. The control plot yielded only 65 bu/a. The Axiom + Balance + Atrazine treatment had a yield of 126 bu/a, which was related to the poor Cosf control. Yields of the other treatments ranged from 142 to 204 bu/a.
Corn injury was observed with several of the POST treatments 7 days after application ( Table  3). The two treatments containing Aim had the greatest injury but did not seem to affect yield. Lacg control ranged from 72 -95%. All treatments did a good job of controlling Paam and Cosf. The untreated check yielded only 85 bu/a. Yields of the treatments were quite variable but ranged from 126 to 181 bu/a. Yields were not correlated well with weed control or injury. The high LSD of 41 bu/a indicates a large variability in yield in this experiment.

Summary
Herbicides were evaluated in two tests: (1) 12 treatments in a preplant incorporated, preemergence test (PPI/PRE) and (2) 20 treatments in a postemergence test (POST). The PPI and PRE treatments caused very little soybean injury, but most POST treatments caused some injury. The PPI treatments gave better control of large crabgrass and Palmer amaranth (Paam) than PRE treatments. Untreated checks had no grain yield. Paam control was poor with most treatments in the POST test.

Introduction
Chemical weed control and cultivation have been used commonly to control weeds in row crops. Weeds can seriously depress soybean yields. Two soybean herbicide tests were conducted: the PPI/PRE test included preplant incorporated and preemergence herbicides and the POST test included postemergence herbicides. The major weeds evaluated in these tests were large crabgrass (Lacg), Palmer amaranth (Paam), and common sunflower (Cosf).

Procedures
Both tests were conducted on a Sarpy fine sandy loam soil with a pH of 7.4 and organic matter content of 1.5% previously cropped to corn. Pioneer Brand 9362 SCN soybeans were planted on May 13 at 144,000 seeds in 30-inch rows. Fertilizer (10-34-0) was banded at 120 lbs/a at planting. The herbicides were applied as follows: PPI & PRE -May 13; early postemergent (EP) -June 10 in the PPI/PRE test and June 7 in the POST test; and late postemergent (LP) -June 13. Significant rainfalls after the PPI and PRE treatments were on May 15 (0.22 inch), May 29 (0.59 inch), and June 8 (1.63 inches). The plots were not cultivated. Ratings reported for crop injury were made on June 9 for the PPI/PRE test and on June 15 and June 24 for the POST test. Ratings reported for weed control were made on June 30 for the PPI/PRE test and on July 6 for the POST test. Harvest was on October 14 using a modified Gleaner E plot combine, although some plots were not harvested because of high infestations of Paam and Cosf.

Results
Significant soybean injury was observed with only one treatment, Python + Prowl, PRE + FirstRate, EP, in the PPI/PRE test (Table 4). Lacg and Paam control was much better with the PPI treatments than with the PRE treatments because of the lack of rainfall for activation. Control of Lacg and Paam was lowest with the Command + Authority, PRE treatments, possibly because Authority requires more moisture for activation. Only 0.22 inch rainfall was received during the first 16 days after treatment. Control of Cosf was excellent with all treatments except for the Command + the low rate of Authority. Authority is weak on Cosf. Yields were related closely to weed control, and the untreated check had no yield.
Most postemergence treatments had some injury (Table 5). Treatments containing Cobra, Flexstar, Stellar, Reflex, and Status gave the most injury. Very little injury was observed with Raptor, Expert, and FirstRate. The LP treatment of Select resulted in excellent control of Lacg. All treatments, except Cobra and Stellar alone, gave excellent control of Cosf, which indicates that none were ALS resistant. Paam control was generally lower than usual, with only six treatments providing greater than 80% control. This could have been related to the lack of rainfall prior to application (plant stress) and the heavy rainfall the day after application. Grain yields were low, mainly because of the lack of Paam control, and ranged from 9.6 to 31.6 bu/a with no yield for the untreated check.

Summary
The average yield of the 33 hybrids in the test was 172 bu/a, with a range from 143 to 202 bu/a. The LSD(.05) was 23 bu/a (two hybrids must differ in yield by 23 bu/a to be considered significantly different in yielding ability 95% of the time).

Introduction
This test at the Paramore Unit is one of the 13 locations of a regional fee test coordinated by Dr. L. L. Darrah with USDA-ARS at the University of Missouri. The 1998 test included 30 white hybrids and three yellow hybrid checks submitted by 13 commercial seed producers. Twelve white hybrids were new to the test in 1998.

Procedures
Anhydrous ammonia at 150 lbs N/a was applied on April 10. Atrazine 4L at 1.5 qt/a plus Lasso at 2.0 qt/a was incorporated with a field cultivator on April 14. The hybrids were planted on April 17 at 30,000 seeds/a in 30-inch rows on a silt loam soil following a previous crop of soybeans. Fertilizer (10-34-0) at 120 lb/a was banded at planting. The test was cultivated on May 21, furrowed for irrigation on June 1, and harvested on September 8 with a Gleaner E plot combine.

Results
Yields in this test averaged172 bu/a, with a range from 143 to 202 bu/a and an LSD(.05) of 23 bu/a (Table 6). Irrigated corn yields were lower than those in previous years. The yellow corn performance test (conducted at the Rossville Unit) had an average yield of 151 bu/a, with a range from 122 to 184 bu/a. The yellow check B73xMo17 yielded 180 bu/a and the other two yellow checks (Pioneer Brand 3245 and 3394) yielded 190 and 180 bu/a, respectively.

EFFECTS OF APPLICATION METHOD, TIME, AND RATE OF SUPPLEMENTAL NITROGEN ON IRRIGATED SOYBEANS Larry D. Maddux Summary
A study was initiated in 1996 to evaluate effects of nitrogen (N) application time and rate on irrigated soybeans. Soybean yields for the 0 N control plot were 71.8 bu/a in 1996, 65.7 bu/a in 1997, and 61.7 bu/a in 1998. Fertigation at the R3 growth stage resulted in slight yield increases of 2.0 and 3.0 bu/a in 1996 and 1998, but these yield increases were not statistically significant at the 5% probability level. Fertigation at R5 resulted in no significant yield difference. No significant difference in yield was observed in 1997 with any treatment.

Introduction
Irrigated soybean yields in Kansas commonly exceed 60 bu/a. Nitrogen (N) demand during grain fill is quite high at these yield levels. Some producers have been applying about 30 lbs/a supplemental N to soybean fields through irrigation systems at the R3 stage of growth based on research conducted using broadcast N fertilizer. This research was designed to determine the optimum N rate and time of application to provide maximum economic soybean yields.

Procedures
A sprinkler irrigated site on a Eudora silt loam soil at the Paramore Unit was used. Nitrogen rates included 0, 30, and 60 lbs N/a.
In 1996 and 1997, UAN was applied as a fertigation treatment at R1, R3 (beginning pod), and R5 (beginning seed). In 1998, the treatments were changed to apply UAN as fertigation treatments at R3, R5, and R3 + R5. However, because of wet weather during the R5 growth stage, the R5 fertigation treatments were not applied. The treatments were arranged in a randomized complete block design with four replications. A minimum of 0.5 inches of water was applied to all plots with each fertigation treatment. Grain yields were determined by machine harvesting.

Results
No significant differences in soybean yields because of N application time or N rate occurred in any of the 3 years, as shown in Table 7. However, in 1996, we observed a slight trend (2.0 bu/a) to increased yields with fertigation treatments at R1 and R3 growth stages. This same trend was apparent at the 30 lb N/a rate in 1998. No significant differences or trends were seen in the 1997 data. The trends observed in 1996 and 1998 support previous work at Kansas State University, which indicates that irrigated soybeans with high yield potential can benefit from a small amount of N (20 -40 lbs/a) applied at the R3 growth stage.

MACRONUTRIENT FERTILITY AND THE EFFECT OF STARTER FERTILIZER ON AN IRRIGATED CORN/SOYBEAN ROTATION Larry D. Maddux Summary
A corn-soybean cropping sequence was evaluated from 1983 through 1996 (7 years of corn; 7 years of soybeans) for the effects of N, P, and K fertilization on the corn crop. The 7year average showed a corn yield increase with increasing N rates up to 160 lbs N/a. Previously applied N at 160 lbs/a also resulted in an average soybean yield increase of 3.1 bu/a. Corn and soybeans both showed yield responses to P, but only soybean had significant 7-year average yield increases (3.3 and 4.5 bu/a for 30 and 60 lbs P 2 O 5 /a). Potassium fertilization increased average corn and soybean yields by 6 and 2.3 bu/a. In 1997, N increased V6 N content and yield of corn. No significant response to residual soil P was obtained, probably because of the almost 41 lbs P 2 O 5 /a applied in the starter to all plots. Plant K content at V6 was increased with K fertilization, but no yield response was obtained. In 1998, soybean had no significant yield responses to previously applied fertilizers.

Introduction
A study was initiated in 1972 at the Paramore Unit to evaluate the effects of nitrogen (N), phosphorus (P), and potassium (K) on irrigated soybeans. The study was changed to a corn and soybean cropping sequence and planted to corn in 1983. The objectives of the study are to evaluate the effects of applications of N, P, and K made to a corn crop on (a) grain yields of corn and the following soybean crop and (2) soil test values.

Procedures
The initial soil test in March, 1972 on this silt loam soil showed 47 lbs/a of available P and 312 lbs/a of exchangeable K in the top 6 in. of the soil profile. Rates of P were 50 and 100 lbs P 2 O 5 /a from 1971 -1975 and 30 and 60 lbs P 2 O 5 /a from 1976 -1995. In 1997, the broadcast rates of P were dropped, and a starter of 120 lbs/a of 10-34-0 (12 lbs N/a + 41 lbs P 2 O 5 /a) was applied to all plots (1997 & 1998). Rates of K were 100 lbs K 2 O/a from 1971 to 1975, 60 lbs K 2 O/a from 1976 to 1995, and 150 lbs K 2 O/a in 1997. Rates of N included a factorial arrangement of 0, 40, and 160 lbs of preplant N/a (with single treatments of 80 and 240 lbs N/a). The 40 lbs/a N rate was changed to 120 lbs N/a in 1997. N, P, and K treatments were applied every year to soybeans from 1971 to 1982 and every other year (odd years) to corn from 1983 through 1997.

Results
Average corn and soybean yields for the 14year period from 1983 through 1996 (7-year averages) are shown in Table 8. The 7-year average corn yield showed no significant response to P fertilization, although significant responses were obtained in 1985 and 1993. An average increase of 6 bu/a (significant at the 6% level of probability) was obtained over the 7 years for 60 lbs/a of applied K 2 O.
In 1997, corn yields of 194 bu/a were obtained for both the 120 and 160 lbs N/a treatments (Table 9). Corn yield obtained with starter fertilizer only (12 lbs N/a) was only 92 bu/a. No significant yield differences were observed with the previous P treatments, probably because of the almost 41 lbs P 2 O 5 /a applied in the starter to all plots. No corn yield response to K fertilization was observed.
However, a P x K interaction occurred. Higher yields generally were obtained when both P and K were applied than when only one was applied. The one exception was the 120-60-0 vs 120-60-150 treatments.
Previously applied N of 160 lbs/a resulted in an average soybean yield increase of 3.1 bu/a (Table 8). Soybeans responded to P fertilization with average yield increases of 3.3 and 4.5 bu/a with 30 and 60 lbs P 2 O 5 /a. Potassium fertilization of soybeans resulted in an average yield increase of 2.3 bu/a. However, in 1998, no significant yield responses to previously applied N, P, or K were observed.
These results indicate the importance of soil testing and maintaining a balanced fertility program.  1983, 1985, 1987, 1989, 1991, 1993, and 1995 and to soybeans for 11 years prior to 1983. 2 Significant at the 6% level of probability.  1 Fertilizer applied to corn in 19831 Fertilizer applied to corn in , 19851 Fertilizer applied to corn in , 19871 Fertilizer applied to corn in , 19891 Fertilizer applied to corn in , 19911 Fertilizer applied to corn in , 19931 Fertilizer applied to corn in , and 1995 and to soybeans for 11 years prior to 1983. N & K treatments applied to corn in 1997 2 P treatments not applied in 1997. Starter fertilizer of 10 gal/a of 10-34-0 was applied to all treatments in 1997 & 1998.

SANDYLAND EXPERIMENT FIELD Introduction
The Sandyland Experiment Field was established in 1952 to address the problems of dryland agriculture on the sandy soils of the Great Bend Prairie of SC Kansas. In 1966, an irrigated quarter was added to demonstrate how producers might use water resources more efficiently and determine proper management practices for, and adaptability of, crops under irrigation on sandy soils.
Research at the field has help define adapted varieties/hybrids of wheat, soybeans, alfalfa, grain sorghum, and corn. As irrigated corn, soybean, wheat, and alfalfa production grew in importance, research determined proper management strategies for irrigation, fertilizer, pest control, and related cultural practices. Presently, research focuses on variety/hybrid evaluation; the evaluation of new pesticides for the area; the practicality of dryland crop rotations vs. continuous wheat; corn nitrogen fertilizer requirements; reexamining accepted cultural practices for corn and grain sorghum; and the long-term effects of cropping systems on yield, soil conditions, and residue cover. A long-term study was initiated in 1996 to determine cultural practices to maximize the efficiency of irrigation inputs from both engineering and agronomic standpoints. Also of interest to irrigated corn producers, 1998 was the third year of a study determining the effects of narrower corn rows and plant population on corn yield.

Soil Description
Soil surface horizons range from Pratt, Carwile, and Naron loamy fine sands to Farnum, Naron, and Tabler fine sandy loams. Subsoils are much more varied, ranging from loamy fine sand to clay. These soils are productive under dryland conditions with intensive management and favorable precipitation patterns. Under irrigation, these soils are extremely productive, and high quality corn, soybean, and alfalfa are important cash crops.

Weather Information
The weather pattern characterizing 1998 differed markedly from 1996 and 1997 and resulted in much below-normal precipitation throughout the growing season, with the exception of July (Table 1).
Wheat yields, overall, were well above average. Dryland sorghum and corn grain yields were below those of the last several years because of a lack of timely moisture and severe heat and moisture stress during critical growth stages. Irrigated corn grain yield was affected negatively by late June heat stress that followed cool conditions in May and early June and delayed anthesis. Then the extremely hot, dry conditions in August resulted in a compressed grain fill period and further hurt yields. Irrigated soybean production was impacted severely by severe heat in late August to September, during peak pod fill.
Soil moisture conditions were poor for establishment of the 1999 wheat crop through September; however, early October rains provided excellent moisture for planting. This rain did result in some replanting and further replanting was necessary when over 6 inches of rain fell at the end of October.
Total precipitation for 1998 was slightly above normal because of the excessively wet period at the end of October (Table 1). Total 1998 precipitation measured 26.7 inches compared to the long-term average of 25.9 inches. Unlike 1996 and 1997, precipitation from May through September was much lower than normal, only 72.5% of the long-term average. If July is not considered, rainfall was only 40% of normal. As of Jan. 1, 1999, topsoil and subsoil moisture contents were adequate to surplus over much of the area.
The low temperature for 1998 occurred in December, temperatures below 0 o F on 4 days. Overall, the winter of 1998 was relatively mild with little snowfall; however, a heavy wet snow followed by a severe ice storm occurred in March. The yearly high was 106 o F, occurring on September 6. During the period from May 1 to September 30, temperatures were 90 o F or higher on 83 days and 100 o or higher on 16 days. Temperatures in August were 90 o F or higher on 24 days and 100 o or higher on 3 days. In September, temperatures were 90 o F or higher on 21 days and 100 o or higher on 4 days. The storm season was much quieter than normal.
The frost-free season lasted from April 18 until November 10, resulting in a growing season of 206 days, approximately 21 days more than the long-term average.

Introduction
Weed control is a major problem in irrigated corn production, especially when postemergence cultivation is eliminated, is. This problem is accentuated on sandy soils low in organic matter. Additionally, there is concern involving the use of atrazine, a common herbicide in SC Kansas and the potential for its movement into groundwater. Atrazine is one of the best, most cost-effective herbicides for season-long broadleaf control on the sandy soils of the Great Bend Prairie. Problems with atrazine do exist, especially when corn is grown continuously, because populations of atrazine-resistant weeds develop. This study was initiated to determine the effectiveness of alternatives to herbicide programs containing preemergence atrazine applications on sandy soils in SC Kansas and to compare newly labeled, not yet labeled, and nonresidual compounds for use in Kansas to more conventional programs.

Procedures
A loamy fine sand (Pratt and Naron) was used for this study, which was cropped to soybeans in 1997 and corn in 1996. The entire site was tandem disked once and packed in the spring of 1998 prior to planting. Fertilization included 100 lb/a 18-46-0 and 125 lb/a N applied as urea (46-0-0) prior to spring tillage and 100 lb/a N at V-6. A 113-day corn hybrid NC+ 4616, was planted on May 3 at 32,500 seeds/acre at a depth of 1.5 inches. No soil insecticides were used. Plots were 20 ft long and 10 ft (four 30-inch rows) wide with four replications in a randomized complete block.
A total of 17 treatments was used. Preemergence (PRE) treatments were applied on May 6 and postemergence (POST) treatments on May 29. Treatments were applied using a tractor-mounted compressed-air sprayer at 30 psi and 20 gal/a water. Crop injury and weed pressure were monitored throughout the growing season and examined extensively immediately prior to and 2 weeks after POST treatments. Plots were irrigated as necessary from May 28 until August 30 with a total of 12 inches of water applied in 19 irrigations. Corn was hand-harvested in mid-October and mechanically shelled. Yields were adjusted to 15.5% moisture.

Results
Treatments are listed in order of descending yield (Table 2). No significant crop injury was noted for any treatment. As in most years, the only grass present was crabgrass. All herbicide combinations provided good to excellent crabgrass control.
The two predominant broadleaf species were puncture vine and pigweed species, predominantly Palmer amaranth, although some lambsquarter, carpet weed, and cocklebur were present. Broadleaf control was fair to excellent, with the weakest treatments being 3 and 10. Number 3 was Dual II only and number 10 was a total POST treatment involving Accent Gold and Banvel. The single weed species that appeared to determine yield was Palmer amaranth. As pressure from this species increased, yields decreased. The yield decrease in treatment number 12 appeared to be due to crop damage caused by the dicamba in the Marksman. The PRE application of Basis (treatment numbers 6 and 15) provided greater crabgrass suppression than expected with an early application.
Of the seven top-yielding treatments, all involved a combination of a PRE herbicide for initial control followed by a POST application. The high rate of Axiom in combination with atrazine injured the crop and appeared to somewhat negatively affect yields. On these light textured, low organic matter soils, the lower 8 oz rate of this product appeared quite effective in controlling crabgrass.
One of the main purposes of this study is to determine the effectiveness of herbicide programs not involving PRE atrazine. As in previous years, treatments involving POST atrazine performed well. Small amounts of atrazine when added to newer products such as Aim, Basis, and Axiom greatly increase their effectiveness, while reducing the risk of or surface groundwater contamination from atrazine.
Herbicide programs combining PRE and POST applications provide the best most consistent weed control and minimize producer risk.
This study will continue to examine weed control options for corn on sandy soils, however, after 7 years, we can safely state that effective weed control is indeed possible without high use rates of PRE atrazine. The difficulty is comparing cost effectiveness, but with the advent of very low use rate SU compounds and price reductions by manufacturers over the last 18 months, this appears to be less of a problem than in the past.  LSD(0.05) 1 6 7.6 15 1 Two treatments must differ by more than the LSD to be different. * Crabgrass at mouse ear stage ** Crabgrass 0.5 -1 in. tall

Introduction
Corn is the most important cash crop in SC Kansas produced under irrigation, with 13% of the state's crop produced in the nine county area of the Great Bend Prairie. The sandy soils and climate of the region in combination with irrigation result in average yields of 150 to 160 bu/a in most years. Under intensive management with favorable weather, producers expect yields of 190 to 200+ bu/a on their "better" ground. Typically, corn is planted from mid-April to mid-May with populations averaging 24,000 to 30,000 plants/a. Normally, producers plant a full-season hybrid (112 days or greater to black layer), although hybrids of shorter maturity are increasing in popularity.
Though irrigated corn production has been an economic boom to Kansas, it has not been without problems, especially in western Kansas where aquifer depletion is a major concern. Although vast improvements have been and are being made in irrigation technology, many questions remain.
Decreases in water levels of the aquifer in SC Kansas in the region of the Great Bend Prairie have not been as dramatic as those in western Kansas. The structure of the aquifer and the soils of the region have allowed for lesser decreases, and years of high rainfall such as the mid-1970's, 1992, 1993, 1996, and 1997 have resulted in significant recharge of the aquifer in much of the region. Thus, groundwater can be viewed as a sustainable resource, especially with careful management of irrigation and agronomic systems to maximize water use efficiency.
Another factor complicates the view of sustainable irrigation, especially in the Rattlesnake Creek Watershed, where the Quivira National Wildlife Refuge is located and from which it receives its water. Although groundwater is viewed as renewable for irrigators, the lowering of water table levels by irrigation has diminished stream flow into Quivira and resulted in less water than needed to maintain the refuge during periods of below-normal precipitation, especially in the fall during the peak migration period. Strategies are needed not only for managing irrigation to sustain it, but for developing practices to ensure adequate surface waters to maintain the refuge. Although switching hardware on pivots and using irrigation scheduling can help decrease irrigation inputs, the selection of proper agronomic practices (planting date, tillage, hybrid maturity) is potentially as or more important in reducing water usage.
The primary objective of this study is to determine the effects of no-tillage vs. conventional tillage, hybrid maturity, planting date, level of irrigation inputs, and their interactions on the yield, water usage, and economic return for corn produced on the sandy soils of SC Kansas. This is the third year of a multiyear study. The study involves the departments of Agronomy, Biological and Agricultural Engineering, and Agricultural Economics. Support for this project is provided by the Kansas Corn Commission.

Procedures
The soil for this study is predominantly loamy fine sand with some fine sandy loam. The site was cropped to grain sorghum in 1994 and 1995 and to wheat in the prior 2 years. Fertilization consisted of 100 lb/a 18-46-0 each year in March. Nitrogen was applied as granular urea (46-0-0) and was split in two 125 lb N/a increments, preplant and V6. Plots at all planting dates received 1 qt/a Dual II + 1 pt/a atrazine preemergence followed by 1 qt/a Marksman postemergence. Plots at the first two planting dates also received 2/3 oz/a Accent to control crabgrass and volunteer grain sorghum in 1996. All plots were planted at 34,000 seeds/a with a John Deere no-till row planter.
Treatments were as follows: Plots were arranged in a randomized complete block with four replications. Irrigation level differences were achieved by replacing the overhead system with drops, pressure regulators, and three different nozzles that allowed us to apply differential irrigation rates.
Measurements included final plant population, dates of 50% emergence and silking, grain yield, and grain moisture.

Results
As the data show, part of the site where the medium irrigation rate was applied contained large variations in corn grain yield, most likely related to soil compaction. The differences were larger for 1996 than 1997. This resulted in wide yield variation and lower than expected yields.
Growing season precipitation was much above normal during both 1996 and 1997 and resulted in the need for less irrigation than normal ( Figure 1 and Table 3). In 1998, except July, precipitation was much below normal, especially during August. The maximum differences in water applied were 2 inches in 1996, 2.1 inches in 1997, and 4.8 inches in 1998.
Mid-May planting significantly decreased yields overall. Increasing irrigation levels slightly increased yields in 1996, had no effect in 1997, and increased yields for the two later planting dates in 1998 (Figure 2). Extreme heat and low humidity, particularly in late June and August, severely decreased yields for all treatments. No-tillage resulted in lower yields in 1996, had no significant effect in 1997, and significantly decreased yields overall in 1998 (Figure 2). The 108-and 103-day hybrids were competitive with the 118-day hybrid in 1996 and 1997; however, the 118-day hybrid was damaged significantly by growing season conditions in 1998 ( Figure 2).
Overall, the two early hybrid yields were less affected by planting date, and yields decreased with increasing maturity and planting date ( Figure  3). All three hybrid yields were lower overall with the no-tillage system in 1996, unaffected by tillage in 1997, and lower without tillage in 1998 (Figure 4). Figures 5, 6, and 7 are presented as an overview of all treatment variables. Three years into the study, several trends are becoming evident.
Planting date has been the single most important variable in determining yields. As planting became later, yields decreased significantly. This was true in spite of the cold conditions. Overall, eliminating tillage did not result in significant yield reductions during good years, but significantly decreased yields in a hot, dry years. Of note, the negative effect of eliminating tillage increased as planting date was moved later. This is partly contradictory to conventional wisdom. Earlier maturing hybrids were competitive with a fullseason hybrid and were less sensitive to planting date. Finally, during the two mild, wet years, decreasing irrigation did not adversely affect yields. Even in a dry, hot year, as in 1998, the low irrigation rate did not adversely affect yields for earlier planting, but did negatively impact yields for later planting.
The fourth and final year of this study is 1999. Then we will conduct an economic analysis of the relative income of each system and determine the cost. We will be able to discuss the agronomic consequences of the planting date, irrigation level, tillage and hybrid maturity interactions and make recommendations.     . Corn grain yield by hybrid maturity using planting date X irrigation level X tillage interaction, Sandyland, 1998.

CROP PERFORMANCE TESTING AND NEW PROJECTS Victor L. Martin
During the 1998 cropping season, performance tests were conducted on dryland wheat and grain sorghum, as well as irrigated wheat, standard and Roundup Ready soybeans, grain sorghum, and both full-and short-season corn hybrids. Great variability rendered the irrigated wheat performance test unusable. The dryland grain sorghum performance test also contained high variability. Information from the crop performance tests is summarized in the respective crop performance test publications available at local county extension offices.
Alfalfa variety trial data will be available in the fall of 1999. A new test was initiated in September 1997 and had excellent emergence and fall growth; however, severe weed pressure rendered the data unusable. For information concerning previous alfalfa variety tests, please contact the Sandyland Experiment Field.
Bt corn studies are continuing, as are several fertilizer studies, both dryland and irrigated. This information can be found in the Kansas Fertilizer Research report (SRP 829) and the Southwest Research-Extension Center Field Day reports (SRP 814).
In 1999, several new studies will be initiated. One study will determine the potential for dryland soybean production on the sandy soils of the area. Roundup Ready soybeans will be used across a range of maturities with tillage and planting date variables. A study furthering work previously done on narrow-row corn will focus on optimum plant populations for 15-inch rows. With the increased drought tolerance and yield potential of grain sorghum hybrids, the effect of population and planting date will be reexamined.
You may contact the Sandyland Experiment Field if your local extension office does not have information concerning existing and new projects.

Summary
Water application patterns from LDN type sprinklers can result in nonuniform water distributions and low coefficients for uniformity for certain spacing and operating pressure arrangements. Increasing the number of deflector plates may help to break up water patterns and improve uniformity.
Similarly, increased operating pressure also can improve application uniformity. However, this work measured only a 10-ft sprinkler spacing and a limited number of orifice/pressure combinations.
Additional research is being conducted to improve this database and to evaluate these effects on crop yield.

Introduction
Irrigation systems and nozzle packages should be designed to apply water uniformly to all areas of the irrigated field. Nonuniform applications of water occur when areas of the irrigation system apply more or less water than other areas. These application differences may occur regularly throughout all of the system or just within portions of the system because of nozzle application problems, or they may occur at specific locations within the system as a result of improper nozzle sizing or improper pressure distribution. All irrigation systems will have some nonuniform water applications at levels that are acceptable. Because irrigation events are scheduled to provide "just-in-time" water to the crop, effects of irrigation uniformity on yield can become substantial. This work was conducted to evaluate the uniformity of water applications from low drift type nozzles (LDN).

Procedures
These studies were conducted at the Sandyland Experiment Field, St. John, Kansas.
The irrigation system was a T-L linear with four, 160-ft long spans. Each span had 16 nozzle outlets outfitted with gooseneck pipes, flexible hose drops, and poly weights. On the end of each flexible drop pipe was a pressure regulator and an LDN. The resultant nozzle drops were on a 10-ft spacing.
Three of the spans were arranged with #16 (16/64-in., low rate), #18 (18/64-in., medium rate), or #20 (20/64-in., high rate) nozzle orifices on Senninger, fixed-plate, LDN sprinklers. These were all pressure regulated to 6 psi. The fourth span was arranged with two groups of eight LDN sprinklers. One group had #14 (14/64-in.) orifice nozzles with 15 psi regulators, and the other group had #16 (16/64-in.) orifice nozzles with 10 psi regulators. The resultant water application rates from these two combinations and the #18 orifice at 6 psi sprinkler were similar. This comparison was used to evaluate the effect of operating pressure on water distribution patterns.
Large-diameter catch pans (17-in.-diameter plastic pans) were placed on 4 foot centers parallel to the direction of travel of each span. The system was operated at a speed that would apply approximately 0.80 inches of water to the zones of medium application rate. Collected water was weighed, and data were statistically analyzed and plotted.

Results
Water application distribution patterns from the #16, #18, and #20 orifice size LDN sprinklers at 6 psi of pressure are shown in Figures 8, 9, and 10, respectively. The Christiansen coefficients of uniformity (CU) for each of these patterns were 71%, 71%, and 79%, respectively.
The #16 and #18 orifice sprinklers had two deflector plates, whereas the #20 sprinkler had three deflector plates. The third plate aided in breaking up the water application pattern. and improving the uniformity. Figure  11 shows the distributions for the medium water application rate from the LDN sprinklers with the #18 orifice size at 6 psi, the #16 orifice size at 10 psi, and the #14 orifice size at 15 psi. The resultant CU values for these patterns were 78%, 88%, and 93%. These results suggest that for this flow rate and spacing requirement, the higher pressure arrangement resulted in a more uniform water distribution. However, this result may not occur consistently for other spacing and flow arrangements and is being studied currently using laboratory data and computer simulations.
This work was supported in part by the State Water Fund of the Kansas Water Office and the Kansas Corn Commission  Figure 11. Water application distribution patterns from LDN sprinklers on a 10-ft spacing and a 7-ft height. Three patterns are shown: #18 (18/64-in.) orifice with two deflector plates and operated at 6 psi (solid line); a #16 (16/64-in.) orifice with two deflector plates and operated at 10 psi (bold solid line with triangles); and a #14 (14/64-in.) orifice with a single deflector plate and operated at 15 psi (bold solid line with diamonds). The coefficients of uniformity for these patterns are 78%, 88%, and 93%, respectively. Sandyland Experiment Field, St. John, KS.

Summary
Studies were conducted to evaluate the effects of variable irrigation rates and nonuniform irrigation distributions on crop yield. Corn yield increased with increased applied water and with increased water application uniformity on a loamy sandy site. Soybean yield also increased with increased irrigation on a sandy loam site. Commercial corn yield on one silt loam sites was highest at the lowest irrigation rate of 6.9 inches. Corn yield on the other silt loam site was more variable, and yield from the irrigation rates of 4.9 to 10.7 inches did not vary by more than 12 bu/a.

Introduction
Irrigation systems are used to provide water to crops when rainfall is not sufficient to meet their evaporative demands. Variable application rates of irrigation water can occur within fields that are irrigated by systems that have nonuniform water distributions. However, improper irrigation scheduling results in water application rates that vary from the optimum by either applying too much water, too little water, or poor timing. This work was conducted to initiate field evaluations of variable water application amounts and the effects on crop yield.

Procedures
These studies were conducted at the Sandyland Experiment Field, St. John, Kansas and on three commercial farm sites. The Sandyland irrigation system was a T-L linear irrigation machine with four, 160-ft long spans. Each span had 16 nozzle outlets outfitted with gooseneck pipes, flexible hose drops, and poly line weights. On the end of each flexible drop pipe was a pressure regulator and a low drift nozzle (LDN) type fixed-plate sprinkler. The sprinkler drops were on a 10-ft spacing. Soil at the site was a loamy fine sand.
Three of the spans were each arranged with #16 (16/64-in., low rate), #18 (18/64-in., medium rate), or #20 (20/64-in., high rate) nozzle orifices on Senninger, fixed-plate, LDN sprinklers. These were all pressure regulated to 6 psi. The fourth span was arranged with two groups of eight LDN sprinklers. One group had #14 (14/64-in.) orifice nozzles with 15 psi regulators, and the other group had #16 (16/64in.) orifice nozzles with 10 psi regulators. The resultant water application rates from these two combinations and the #18 orifice at 6 psi sprinkler were similar. This comparison was used to evaluate the effect of operating pressure on water distribution patterns.
Corn was planted on May 8 in rows that were parallel to the direction of travel and on a 30-in. spacing. The irrigation system was scheduled to apply water in response to crop need. A summary of the sprinkler characteristics and applied water is provided in Table 4. Corn was hand harvested by row on September 15, 1998. Harvest plots included 20 ft of row and 12 rows per water treatment.
Commercial field studies were conducted on three center-pivot-irrigated fields with systems that irrigated 110-130 acres. These fields were designated as Sites 5, 6, and 8. Sites 5 and 6 had silt loam soils, and Site 8 had a sandy loam soil. Sprinklers on each of these center pivot systems were modified to provide three different application depth zones. Each modified zone consisted of five sprinklers that were pressure regulated at 25 psi and had preselected nozzle orifice inserts to provide the desired application rate. Water from the center sprinkler drop of each zone was measured throughout the season using an in-line, precision flow meter. These modified zones were located on the second and third spans of the center pivot systems. Plots from each of these systems were hand harvested at crop maturity. A summary of the three systems is provided in Table 5.

Results
Yield results from the Sandyland site are summarized in Figures 12 and 13. Seasonal rainfall (May through August) totaled 10.4 inches. However, 6.1 inches was measured in July, and only 3.6 inches of this was estimated as effective. Therefore, effective seasonal rainfall was estimated to be 7.9 inches. Figure 12 shows yield and water use efficiency responses to applied irrigation. Yield increased as applied water increased. Water use efficiency (WUE) was calculated as the ratio of yield to total water (irrigation plus rainfall). Higher values of WUE occurred in plots that had higher irrigation coefficient of uniformity (CU) values. The most uniform plot (#14 orifice at 15 psi) had the lowest yield variation (CV) determined as the ratio of the standard deviation to the mean yield from the 12 rows in a plot.
Yield and water use efficiency data from commercial field sites 5, 6, and 8 are shown in Figures 14, 15, and 16, respectively. Total water (irrigation plus rain) for site 5 ranged from 14.9 to 21.7 inches. Corn yield ranged from 141 to 153 bu/a with the highest WUE of 10.0 bu/inch ( Figure 14). Total water for site 6 ranged from 15.2 to 20.6 inches. Corn yield ranged from 150 to 186 bu/a with the highest yield and highest WUE (12.2 bu/in.) occurring at the lowest applied irrigation depth of 6.9 in. (Figure 15). Soybean yield increased with increased irrigation (Figure 16), but the highest WUE of 2.9 bu/in. occurred at the medium irrigation rate of 9.2 inches.
This work was supported in part by the State Water Plan Fund of the Kansas Water Office, and the Kansas Corn Commission.

Summary
Twenty-six corn hybrids (15 Bt and 11 non-Bt) were evaluated for corn borer resistance and grain yield. The yield losses to girdling by southwestern corn borers averaged 16.6 bu/a for the unsprayed non-Bt hybrids, 0.7 bu/a for sprayed non-Bt hybrids, and 10.9 bu/a for hybrids with event 176. Hybrids with Bt11, MON810, and CBH351 had virtually no yield loss. Grain yields averaged 127.4 bu/a across all hybrids in the sprayed block and 116.8 bu/a in the unsprayed block.

Procedures
Corn hybrid plots were machine-planted on 8 May at 26,000 seeds/a at the Sandyland Experiment Field near St. John, KS. Spot replanting was done as necessary. Preemergence herbicides applied on 12 May were 1 qt. Dual and 1 qt. atrazine/a. The soil was a sandy-loam. The field was sprinkler irrigated six times in June, four times in July, and twice in Aug. with totals of 5.4, 4.0 and 1.7 inches of water, respectively. The sprinkler broke down in Aug., so irrigation was inadequate for this critical period. The monthly rainfalls at Pratt for April, May, June, July, and Aug. were 1.1, 2.5, 0.5, 4.8, and 1.8 inches, respectively. The plots were four rows wide (10 ft) by 30 ft long. Two rows (5 ft) of Bt corn were planted between the plots as border rows, and 10-ft alleyways at the end of each plot were left bare. The border rows, and alleyways were included to reduce larval migration between plots. The experimental design was a split-plot with three replications. The main plots were insecticide-protected versus insecticide unprotected, and the subplots were the corn hybrids. The protected blocks were sprayed on 22 July with Capture (bifenthrin) at 0.08 lb. AI/a. The study included 26 hybrids with relative maturity ratings of 110 to 118 days. An attempt was made to pair each non-Bt hybrid with its Bt sister line or another related hybrid. Pioneer 3162IR was included as the standard commonly used hybrid.
All corn borers were native infestations. First generation corn borer damage was rated on 22 July using the 1 to 9 Guthrie scale. Data for second generation corn borers were taken from five plants chosen at random from the two center rows of each plot. The plants were dissected to record corn borers and tunneling. Kernel damage was recorded as the number of kernels damaged at the tip and at the base or side of the ear (mostly corn earworm damage). Yield was determined by hand harvesting the two middle rows of each plot in late October. Ears from standing plants and those from fallen plants were harvested separately. Grain yield was calculated separately for standing and fallen corn and corrected to 15.5% moisture.
Across the Bt hybrids (with no corn borer damage), the yield difference between sprayed and unsprayed was 8.1 bu/a. This yield loss could have been due to spider mite damage, but spider mite data were not collected. The plots were treated with Capture, a good miticide.
Corn earworm damage to kernels in the ear tip was moderate, averaging 23.3 kernels damaged per ear in the unsprayed non-Bt corn (Tables 7). Hybrids with Bt11, Mon810, and CBH351 and sprayed non-Bt hybrids averaged 76, 30, 42 and 45% reductions in kernel damage, respectively (Fig 20). Hybrids with Bt176 had little reduction in kernel damage.
Grain yield averaged 127.4 bu/a across all hybrids in the sprayed block, and 116.8 bu/a in the unsprayed block (Tables 7 & 8, Fig. 21). The standard hybrid, Pioneer 3162IR, yielded only 96.0 bu/a in the sprayed blocks and 89.5 bu/a in the unsprayed blocks, which were uncharacteristically low. Although gray leaf spot is sometimes a problem for this hybrid, we observed no unusual levels of disease infection. A number of Bt and non-Bt hybrids were among the top yielders.
Note: This research was supported by Kansas Corn Commission Check-off Funds through the Kansas Department of Agriculture.

SOUTH CENTRAL KANSAS EXPERIMENT FIELD Introduction
The South Central Kansas Experiment Field was established in 1951 on the US Coast Guard Radio Receiving Station located southwest of Hutchinson. The first research data were collected with the harvest of 1952. Prior to this, data for the South Central area of Kansas were collected at three locations (Kingman, Wichita, and Hutchinson). The current South Central Field location is approximately 3/4 miles south and east of the old Hutchinson location on the Walter Peirce farm.
Research at the South Central Kansas Experiment Field is designed to help the area's agriculture develop to its full agronomic potential using sound environmental practices. The principal objective is achieved through investigations of fertilizer use, weed and insect control, tillage methods, seeding techniques, cover crop and crop rotation, variety improvement, and selection of hybrids and varieties adapted to the area. Experiments deal with problems related to production of wheat, grain and forage sorghum, oats, alfalfa, corn, soybeans, rapeseed/canola, and sunflower and soil tilth. Breeder and foundation seed of wheat and oat varieties are produced to improve seed stocks available to farmers. A large portion of the research program at the field is dedicated to wheat breeding and germplasm development.

Soil Description
The soil survey for the South Central Field has approximately 120 acres classified as nearly level to gently sloping Clark/Ost loams with calcareous subsoils. This soil requires adequate inputs of phosphate and nitrogen fertilizers for maximum crop production. The Clark soils are well drained and have good water-holding ca-pacity. They are more calcareous at the surface and less clayey in the subsurface than the Ost. The Ost soils are shallower than the Clark, having an average surface layer of only 9 inches. Both soils are excellent for wheat and grain sorghum production. Large areas of these soils are found in southwest and southeast Reno County and in western Kingman County. The Clark soils are associated with the Ladysmith and Kaski soils common in Harvey County but are less clayey and contain more calcium carbonate. Approximately 30 acres of Ost Natrustolls Complex, with associated alkali slick spots, occur on the north edge of the Field. This soil requires special management and timely tillage, because it puddles when wet and forms a hard crust when dry. A 10-acre depression on the south edge of the Field is a Tabler-Natrustolls Complex (Tabler slick spot complex). This area is unsuited for cultivated crop production and has been seeded to switchgrass. Small pockets of the Tabler-Natrustolls are found throughout the Field.

1997-98 Weather Information
Precipitation in 1998 totaled 32.04 inches, 2.55 inches above the 30-year average of 29.49 inches ( Table 1). As in previous years, precipitation in 1998 was not distributed evenly through the year or within a given month. The highest monthly total was recorded in November (5.29 inches). When the monthly totals were high (March, September, October, and November), most of the precipitation was received in one or two high-rainfall events. However, most of the water received did not run off and was considered beneficial to crop production until the November rains. The soil conditions at planting of the 1998 winter wheat crop (October 1997) were good because of the above-normal rainfall received in August and September of 1997. After planting, precipitation was considerably below the longterm average for November, but the high soil moisture carried the wheat through until abovenormal rainfall occurred through March. These conditions resulted in excellent wheat growth and a considerable number of fall tillers. Even though moisture was below normal during the grain filling period, it was timely and the temperatures were not extreme. These conditions allowed for nearnormal to above-normal wheat yields.
The summer annuals (grain sorghum sunflowers, and soybeans) also yielded well considering the precipitation and temperatures during the growing season. August was dry and extremely hot. September precipitation was above normal, but temperatures were again above normal. Soil moisture at wheat seeding time for the 1999 crop was considered excellent. A frost-free growing season of 207 days (April 18 -November 11, 1998) was recorded. This is 24 days more than the average frost-free season of 183 days (April 19 -October 17).

Introduction
Oats are utilized not only for grain but also as a forage. Most of the time, oats planted for forage are utilized as a hay crop to feed livestock. The performance test for spring cereals did not report grain yields from oat varieties this year.

Procedures
The oat plots for grain yield were planted on 25 March and the plots for forage yield on 26 March 1998 using the same plot drill and seeding rate. Soil conditions at planting were ideal. The forage oat plots were harvested when the majority of the varieties were in the hard dough stage (15 June 1998) using a Carter Forage harvester. The grain yield plots were harvested on 27 June 1998 with the Gleaner E plot combine. This harvest date was slightly earlier than usual because of the warmer than normal weather conditions.

Results
Oat varieties need to be evaluated for both grain and forage production, because a variety that has high grain yield potential may not have a high forage yield potential. The 1998 growing season was less than ideal for the production of oat grain. The early months were somewhat wet (Table 1) and cool, followed by hot dry weather in April and May. Precipitation in June was near normal, but the temperatures were higher than normal. Thus, the major factor affecting yields (Table 2) in 1998 was the unusual weather during the entire growing season. Another factor that affected both forage and grain yielsd was the amount of barley yellow dwarf infection in some of the varieties. Weather conditions did not have as great an influence on the forage results as they did on the grain yields. The data for forage dry matter from 1995, 1996, and 1998 are summarized in Table 3. 6. Unless two varieties differ by more than the LSD, little confidence can be placed in one being superior to the other.

Summary
The predominant cropping systems in South Central Kansas have been continuous wheat and wheat-grain sorghum-fallow. With continuous wheat, tillage is preformed to control diseases and weeds. In the wheat-sorghum-fallow system, only two crops are produced every 3 years. Other crops (corn, soybean, sunflower, winter cover crops, and canola) can be placed in the above cropping systems. To determine how winter wheat yields are affected by these crops, winter wheat was planted in rotations following them. Yields were compared to those of continuous winter wheat under conventional (CT) and no-till (NT) practices.
Initially, the CT continuous wheat yields were greater than those from the other systems. However, over time, wheat yields following soybeans have increased, reflecting the effects of reduced weed and disease pressure and increased soil nitrogen. However, continuous CT winter wheat seems to outyield NT winter wheat regardless of the previous crop.

Introduction
In South Central Kansas, continuous hard red winter wheat and winter wheat -grain sorghum -fallow are the predominate cropping systems. The summer-fallow period following sorghum is required, because the sorghum crop is harvested in late fall, after the optimum planting date for wheat in this region. Average annual rainfall is only 29 inch/yr, with 60 to 70% occurring between March and July. Therefore, soil moisture is often not sufficient for optimum wheat growth in the fall. No-tillage (NT) systems often increase soil moisture by increasing infiltration and decreasing evaporation. However, higher grain yields associated with increased soil water in NT have not always been observed. Cropping systems with winter wheat following one of several alternative crops would provide improved weed control through additional herbicide options and reduced disease incidence by interrupting disease cycles as well as allow producers several options under the 1995 Farm Bill. However, fertilizer nitrogen (N) requirement for many crops is often greater under NT than CT. Increased immobilization and denitrification of inorganic soil N and decreased mineralization of organic soil N have been related to the increased N requirements under NT. Therefore, evaluation of N rates on hard red winter wheat in continuous wheat and in cropping systems involving alternative crops for the area have been evaluated at the South Central Field. The continuous winter wheat study was established in 1979. The first of the alternative cropping systems where wheat follows short-season corn was established in 1986. The second (established in 1990) has winter wheat following soybeans. Both cropping systems use NT seeding into the previous crop's residue. All three systems have the same N rate treatments.

Procedures
The research was conducted at the KSU South Central Experiment Field, Hutchinson. Soil was an Ost loam. The sites had been in wheat previous to the starting of the cropping systems. The research was replicated five times using a randomized block design with a split-plot arrangement. The main plot was crop and the subplots were six N levels (0, 25, 50, 75, 100, and 125 lbs/a).
Nitrogen treatments were broadcast applied as NH 4 NO 3 prior to planting. Phosphate was applied in the row at planting. All crops were produced each year of the study. Crops are planted at the normal time for the area. Plots are harvested at maturity to determine grain yield, moisture, and test weight.

Continuous Wheat
These plots were established in 1987. The conventional tillage treatments are plowed immediately after harvest then disked as necessary to control weed growth. The fertilizer rates are applied with a Barber metered screw spreader prior to the last tillage on the CT and seeding of the NT plots. The plots are cross-seeded to winter wheat. As a result of an infestation of cheat in the 1993 crop, the plots were planted to oats in the spring of 1994. The fertility rates were maintained, and the oats were harvested in July. Winter wheat has been planted in the plots since the fall of 1994.

Wheat after Corn
In this cropping system, winter wheat is planted after a short-season corn has been harvested in late August to early September . This early harvest of short-season corn allows the soil profile water to be recharged (by normal late summer and early fall rains) prior to planting of winter wheat in mid October. Fertilizer rates are applied with the Barber metered screw spreader in the same manner as for the continuous wheat.

Wheat after Soybeans
Winter wheat planted after a maturity group I soybean has been harvested in early to mid-September in this cropping system. As with the corn, this early harvest again allows the soil profile water to be recharged prior to planting of winter wheat in mid-October. Fertilizer rates are applied with the Barber metered screw spreader in the same manner as for the continuous wheat.
Winter wheat also is planted after canola and sunflowers to evaluate the effects of these two crops on yield. Uniform N is use; therefore, the data are not presented.

Continuous wheat
Grain yield data for continuous winter wheat are summarized by tillage and N rate in Table 4. Wheat yields in the CT and NT treatments were comparable for the first 4 years. In the fifth year (1992), cheat started to become a serious yieldlimiting factor in the NT treatments. By 1993, it had almost completely taken over the NT treatments. As a result of the cheat problem, the plots were planted to oats in the spring of 1994. This resulted in a significant reduction in cheat. The results for 1995 were not affected by cheat but more by the climatic conditions of the year. The cool wet winter with lush growth was followed by a warm period. This then was followed by cold wet weather during seed setting and grain filling. The yield data reflect these conditions. The yield increases that occurred with increasing N rate did not materialize that year. These weather conditions contributed to the NT treatments having greater yield reductions than the CT treatments. Conditions in 1996 and 1997 proved to be excellent for winter wheat production in spite of the dry fall of 1995 and the late spring freezes in both years. Yields in 1998 generally were higher than those in 1996 and 1997 and increased with higher N rates up to 75 lb/a.

Wheat after Corn
Wheat yield increases with increasing N rates were observed in wheat following corn in 1988 and 1990 (Table 5). The extremely dry conditions from planting through early May of 1989 caused the complete loss of the wheat crop in the rotation for this year. In 1988year. In , 1990year. In , 1991year. In , 1992year. In , and 1993, when timely precipitation occurred in both germination and spring regrowth periods, wheat yields following corn were comparable to those of continuous wheat. Though not as apparent with sorghum, the effect of reduction in soil N in the 0 N plots also can be seen in the yields. Wheat yields in 1994 showed the benefits of the cool wet April and early June. Had it not been for these conditions occurring at the right time of the plants' development, yields would have been considerably less. Weather conditions were quite different for the 1995 wheat crop in the rotation. These conditions caused considerable variability and reductions in yields compared to 1994. However, the yields in the rotation were higher than those of continuous wheat. Also, the test weights for the wheat in the rotation averaged 60 lb/bu, whereas the average for the continuous wheat was only 53 lb/bu. This points out the necessity of using some type of rotation in the farming operation to produce high quality crops. In 1996, the corn prior to wheat was dropped, and cover crops were added to this cropping system.

Wheat after Soybeans
Wheat yields after soybeans also reflect the differences in N rate. However, a comparison of the wheat yields from this cropping system with those of wheat following corn shows the effects of residual N from soybean production in the previous year. This is especially true for the 0 to 75 lb N rates in 1993 and the 0 to 125 lb rate in 1994 (Table 6). Yields in 1995 reflect the added N from the previous soybean crop, with yield by N rate increases similar to those of 1994. The 1996 yields with spring wheat reflect the lack of response to N fertilizer. Yields for 1997 and 1998 both show the leveling off after the first four increments of N. In comparison to yields in the continuous wheat, yields of rotational wheat are starting to reflect the presence of the third crop (grain sorghum) in the rotation. As the rotation continues to cycle, the differences at each N rate will probably stabilize after four to five cycles, with a potential to reduce fertilizer N applications by 25 to 50 lbs/a where wheat follows soybeans.

Other Observations
Nitrogen application significantly increased grain N contents in all crops. Grain phosphate levels did not seem to be affected by increased N rate.
Loss of the wheat crop after corn can occur in years when fall and winter moisture is limited. This loss has not occurred in continuous winter wheat regardless of tillage or in the wheat after soybeans. Corn will have the potential to produce grain in favorable years (cool and moist) and silage in nonfavorable (hot and dry) years. In extremely dry summers, extremely low grain sorghum yields can occur. The major weed control problem in the wheat after corn system is with the grasses. This was expected, and work is being done to determine the best herbicides and time of application to control grasses.

Introduction
Several new seed treatments are being tested for their effects on winter wheat in the Great Plains region. This study evaluated effects of 12 seed treatments (3 controls and 9 chemical applications) on wheat emergence (fall stand), fall and spring growth, and grain yield.

Procedures
The experiment was done in 1997-98 at the Hutchinson Experiment Field. The site was in the second year of continuous wheat in Clark-Ost clay loam soil. Cultivar 2137 foundation seed was used. It has moderate resistance to most foliar diseases. Each company applied treatments in water. Rates are listed in Table 11. The design was a randomized complete block with 10 replications and 12 treatments, including untreated controls from each company. Seed was planted at 60 lb/a on Oct. 3, 1997 with a six-row cone seeder set to a depth of 1.5 in. Plots were 5 ft by 20 ft and then trimmed to 13 ft long for final yield. Stand counts were taken from a 1-m section of an inner row in each plot on Oct. 17, 1997 at the zero-to onetiller stage of development. Harvest with a small plot combine was done on June 23, 1998. Seed yields were adjusted to 13.5% moisture and 60 lb/bu.

Results
The three controls were similar, so they were combined for analysis. Each treatment was compared to the combined control with SAS GLM/ least squares means with the Dunnett's test, which is designed to optimize comparisons with a control. Experiment-wise error rate was set at α=0.05. Results of the data analysis are presented in Table 7.
Planting was about 1 week before the recommended time. Soil moisture was good at planting. No significant root diseases, insect pressure, or barley yellow dwarf were noted. Some leaf rust developed late, but no obvious differences were noted among treatments. Plots matured early because of heat and dry conditions.
Although the overall F-test for stand count was not significant, the Dunnett's test indicated that the RTU Vitavax-thiram treatment significantly increased the stand count (P≤0.01) over the untreated control. The F-test for test weight was significant. The LS082+LS004 treatment appeared to significantly decrease test weight. However, it had no significant effects on stand or yield, so this may not be a real effect. The F-test for yield differences was not significant. The Dunnett's minimum significant difference for yield was 3.2 bushels per acre. The LSD, which does not control experiment-wise error rates, was 2.8. In either case, no significant yield differences occurred among treatments. NOTE: The study of tillage and nitrogen fertilization for alfalfa was terminated after 1997. No new data were collected in 1998 on the study of Austrian winter pea as a cover crop with grain sorghum.

Introduction
Interest in performance of high-oil corn has increased in northeast Kansas. Dupont Optimum Quality Grains estimated that approximately 1 million acres of high-oil corn was produced in the U.S. in 1997, with approximately 70% being used as livestock feed and the remainder for cash sales. Because of isolation requirements and small market areas, these hybrids are not entered routinely into university performance trials. The objective of this study was to evaluate the performance of several high-oil corn hybrids and compare them to their non-high-oil counterparts.

Procedures
Eleven high-oil corn hybrids were evaluated in 1998 under irrigation at the Rossville Unit of the Kansas River Valley Experiment Field and under dryland at the Paramore Unit of the Kansas River Valley Experiment Field and the North Central Experiment Field. All hybrids utilized ATop Cross@ pollinators to achieve elevated oil levels. For each high-oil hybrid used, its normal yellow corn counterpart also was included. Appropriate isolation was utilized between the grain parent hybrid block and each high-oil hybrid group of the same pollinator. All plots at Rossville and Paramore Units were planted on April 24, 1998, and all plots at the North Central Field were planted on May 6, 1998. Irrigation amounts of approximately 1.5 acre/inch were applied on July 20 and August 21.
Statistical analyses of these hybrids pose a unique problem in that isolation groups have a set of unique treatments. Variances were compared between each high-oil hybrid group. Because variances were different, the high-oil corn hybrids were analyzed within each company only. The normal corn hybrids also were analyzed as a complete group as a randomized block design.

Results
Grain yields were average to below average for both dryland and irrigated conditions. Yields of dryland high-oil corn yields ranged from 104 to 149 bu/a (Tables 1 and 3). Grain yields for the grain parent followed a similar pattern, ranging from 108 to 181 bu/a (Tables 1 and 3).
Previous research with high-oil corn at other universities and at Kansas State indicated an 8 to 15% yield decline compared to conventional yellow corn. These results indicate differences of approximately 12 bu/a or 8%.
Under irrigation at the Rossville Unit, the high-oil hybrids produced grain yields that averaged over 23 bu/a higher than those of the grain parents: 131 to 163 bu/a versus 107 to 130 bu/a. This large difference is difficult to explain. Possibly, soil conditions were not uniform across the plot area. However, because of the blocking of the high-oil hybrids and grain parents for isolation, we could not determine if that was the case. Such a difference between high-oil and grain parent corn hybrids has never been reported previously.
These results also indicated differences among the high-oil hybrids as well as between the high-oil and conventional hybrids in many of the grain quality components measured. In the highoil hybrids, oil contents ranged from 5.8 to 7.7%, which were approximately 2.9 percentage points higher than oil contents of the conventional hybrids. Lysine levels in the high-oil hybrids ranged from 0.29 to 0.32%, which were 0.029 percentage points higher than lysine levels of the conventional corn hybrids. The high-oil hybrids were 0.159 percentage points higher in protein and 662 Mcal/a higher in energy than their conventional counterparts. Price premiums averaged $0.19/bu for the high-oil corn hybrids.

Summary
Thirteen upland cotton varieties were grown at four locations in South Central Kansas. yield and fiber quality varied among locations and varieties.

Introduction
Cotton production has grown steadily in Kansas during the past several years. In 1991 Kansas Agricultural Statistics reported 2,000 acres of cotton in Kansas. By 1998, cotton acres had increased to approximately 10 times that amount. Interest in cotton continues to increase in the South Central part of the state, largely because of the crop's ability to withstand drought and relatively low grain prices.
All cotton varieties that are currently available to producers in Kansas were adapted for growing regions to the south. Although many of the upland cotton varieties currently used on the High Plains of Texas and Oklahoma may be suitable, extensive variety testing has not been done. The objective of this study was to evaluate several upland cotton varieties for lint yield and quality in South Central Kansas.

Procedures
Four locations were selected to represent the cotton-growing region of Kansas.

Results
The 1998 growing season had aboveaverage temperatures and below-average precipitation. Precipitation was timely, with the majority of it occurring in July and early August. Early-season temperature stress resulted in late fruit development, but the heat in August and September quickly moved the crop to maturity before a freeze occurred.
At the Harvey County irrigated site, lint yields averaged 996 lb/a for the entire plot (Table 7). Lint yields at the Marion County site averaged 278 lb/a (Table 8). At the Sumner County site, lint yields averaged 514 lb/a (Table 9). Hail on June 22, 1998 set the crop back at this site.
Lint quality was influenced primarily by location and somewhat by variety (Tables 10-12). Overall, the above-average temperatures during the growing season resulted in average to above-average levels of fiber maturity, length, and strength. Location differences were apparent in average fiber length and strength as well as color grade between the Marion County site and the other two sites. The average length and strength were lower at Marion County, however, the average micronaire was higher. The Marion County site also had lower color grades, averaging a 61. These can be attributed to the later planting date and the fact that several inches of rain fell from October 31 to November 12.   seeds/a at all sites and thinned to a final stand of 21,000 plants/a, if necessary. Plants were monitored for sunflower head moth beginning at ray petal appearance. At 10 and 100% bloom, head moth control plots were sprayed with Warrior® or Asana® at 0.03 or 0.05 pounds ai/a, respectively, in 20 gallons of water. Larvae counts were taken at 3 weeks after 100% bloom. The center two rows of each four-row plot were harvested for yield as they reached "combine" maturity. Harvest dates at Hesston were 15 Sept. (mid-April planting), 17 Sept. (mid-May planting) and 16 Nov. (mid-June and mid-July plantings). Yields were adjusted to 10% moisture.

Results
Sunflower head moth numbers were high for the April, May, and June plantings, but control was good with either treatment (Table 13). Unexpectedly, however, seed yield was not affected. Larval infestation levels experienced in these tests certainly would be expected to cause significant economic loss in producers' fields if left untreated.
Seed yields were greatest from the mid-May planting and least from the mid-June and mid-July plantings, with mid-April yields being intermediate but acceptable (Table 14). As expected, the 2-year yield averages show a seed yield advantage to mid-April and mid-May planting vs traditional and double-cropped planting dates. However, mid-April stand establishment was not nearly as consistent as that from mid-May-planted sunflowers in either year. Mid-June sunflowers were seeded into a dry seedbed and experienced above-normal temperatures and less than adequate rainfall for uniform establishment. When precipitation did occur, the intensity of the rainfall packed the soil surface and kept stands erratic.
Only in the mid-May planting did Cavalry, the fuller season hybrid, produce higher yields than those of Comet (Table 14). Yields of Comet sunflowers were significantly higher only in the mid-April seeding, though the shorter season hybrid showed a trend to yield better in mid-June and mid-July plantings, too. Over 2 years, the fuller season hybrid tended to yield higher when planted in mid-May, and the early season hybrid produced higher seed yields when planted later in the season.
Other research has shown that oil percentage also tends to decline with delayed sunflower planting. A premium of 2% of market price is paid or penalty is assessed for every percentage point above or below 40% oil content, respectively, of the sunflowers. Oil yields for both hybrids were of premium levels for all but the mid-June planting (Table 14). For the mid-July planting, oil yields were enhanced by excellent growing conditions and a longer than normal fill period in September (>200 GDD above normal). Oil percentages for the mid-June planting reflected the stresses of untimely rainfall and extreme heat during flower and fill.
Within planting dates, Cavalry tended to produce seed with higher oil content than Comet, though the only significant difference occurred in the mid-May planting. Comet's oil level was greater than that of Cavalry in the mid-Aprilplanted plots. Mid-July planting may produce a higher-oil seed (2 yr avg.) than mid-June planting, but mid-June yields are more likely to provide a greater gross return because of the advantage of a longer growing season.

Summary
Grain sorghum hybrids responded differently to planting date, depending on location, and obviously were influenced by timely rainfall. May-planted plots were harvested 34 and 61 days earlier than June-planted plots at Wellington and Isabel, respectively. Earlier harvest allows for potentially easier double-cropped wheat planting or fall tillage operations. No-tillage improved crop yields compared to conventional tillage, most likely as a result of water conservation and utilization. For the second year in a row, row width did not influence yield in this study. Two years of results from Wellington with two different types of growing season suggest that yields tend to be more consistent when grain sorghum is planted in May vs June, regardless of hybrid maturity or row width. This was the final year of this study.

Introduction
The 1995 Farm Bill has played a major role in the stabilization and increase of grain sorghum acres in central Kansas. Grain sorghum in the south central area of Kansas is planted traditionally in early June or as a double crop after wheat harvest. Research results from the 1990's at the Harvey County Experiment Field near Hesston and the Sandyland Experiment Field near St. John have shown a consistent yield increase attributed to planting sorghum 3 to 4 weeks earlier than traditional planting dates for the area. In years when crop yields from traditional planting dates were greater, the earlier-planted crop yields were still very acceptable. In addition, harvest dates are generally 3 to 4 weeks earlier with earlier plantings.
This experiment, funded in part by the Kansas Grain Sorghum Commission, evaluates the yield response of two different maturity hybrids planted in two different row spacings at two planting dates (early to mid May and early to mid June) at intervals of approximately 28 days. This is the second, and final, year of the study.

Procedures
Locations were on the Farmers COOP Equity farm at Isabel, in Barber County (Farnum loam) and on the Wellington Area Test Farm near Wellington, in Sumner County (Bethany silt loam). Grain sorghum was seeded on May 19 and June 25 at Wellington and May 22 and June 10 at Isabel in 10-in. and 30-in. rows. Early (Pioneer 87G57) and medium early (Pioneer 8500) hybrids were planted at rates to achieve final stands of 32,000 plants/a. Appropriate grass and weed control herbicides and 100 lb N/a were broadcast applied preemergence. The Isabel field had a conventional vs no-tillage treatment, and Wellington plots were no-till. At harvest maturity, the center two rows (30-in. rows) or the center 5 feet (10-in. rows) of each plot were combine harvested. Harvest dates at Wellington were September 10 for the May 19 planting and October 14 for the June 25 planting. Harvest dates at Isabel were September 10 for May 22 planting and November 10 for June 10 planting. Yields were adjusted to 12.5% moisture.

Results
Untimely rains in early May delayed planting of both sites by 10-14 days. Rainfall at Wellington also delayed the June planting to 10 days later than desired, but still coincided with potential double-cropped planting dates. All plots received adequate rainfall until June. Monthly rainfall totals and 30-year average precipitation are shown in Table 15. The Wellington plots received average precipitation amounts in the month of July, but very little timely precipitation in August and September, during critical growth stages for June-planted sorghum. The sparse rainfall received at Willowdale, the nearest weather station to Isabel, was evidently timely. Above-normal rainfall during July was reflected in final yields.
Results from previous studies in north central and northeastern Kansas have shown a trend towards higher grain yields in narrower rows when growing season precipitation is average to above normal. Row width did not affect grain yields at either site (Table 16). At Wellington, in spite of being no-tilled, a high intensity rain the night after planting prevented desirable emergence and stand establishment in the 10-in. row plots, which were not harvested for yield. Sorghum planted in 30-in. rows emerged and established stands in spite of the crusted soil surface, demonstrating an advantage of wider rows under adverse conditions. Experiment field research has consistently shown a yield advantage to fuller maturity hybrids with earlier planting dates. As planting date is pushed back into June, this advantage gradually will disappear, and often reverse, with the yield advantage going to the earlier maturing hybrid. At Wellington, no yield difference existed between hybrids, regardless of planting date, though yields were reduced greatly in the Juneplanted plots (Table 17). The 2-year averages from Wellington show that differences did exist in 1997, a year with favorable conditions throughout the growing season (Table 17). The 2-year average also indicates the stability of yields from one year to the next when sorghum is planted in early to mid-May vs mid to late June. Planting in June vs May did not significantly reduce the yield of Pioneer 87G57 at Isabel, but Pioneer 8500 planted in June suffered significant yield reductions when compared to the May plantings (Table 17).
Apparently, high temperatures, possibly in combination with moisture stress, coincided with the onset of bloom for June-planted Pioneer 8500 and resulted in reduced seed set and seed yields. The top ½ to a of many heads was affected. This condition was most apparent in the conventionally tilled plots, where the grain yield of Pioneer 8500 plots was reduced nearly 40% compared to May-planted plots, even though no significant differences in yield were recorded in either hybrid (Table 18). If the conventional till plots were analyzed separately, the yields of June-planted Pioneer 8500 plots were significantly lower than those of any other conventional-till plantings at Isabel.
Tillage practices significantly affected yields in the Isabel plots. No-till sorghum yields were 20% higher than those of conventionally tilled sorghum (Table 18). Though the tillage x hybrid interaction was not significant, conventional tilled, June (6/10)-planted sorghum did poorly, especially the fuller maturity hybrid. LSD (0.10) NS NS † May, 1998, 10-in. row plots with never were established because of a hard rain and are not included in the 2-year average at Wellington. The reported 2-year average yield for 10-in. rows planted in May is actually only from the 1997 study. Based on this and other research, however, no significant yield difference would be expected between 10-and 30-in. row plantings in May or June. LSD (0.10) 8.8 12.6 † May, 1998, 10-in. row plots with never were established because of a hard rain, and are not included in the 2 year average at Wellington. The reported 2-year average yield for 10-in. rows planted in May is actually only from the 1997 study. Based on this and other research, however, no significant yield difference would be expected between 10-and 30-in. row plantings in May or June. ‡ Yields at a location must differ by more than the LSD to be considered significantly different.

Summary
The MGIII and MGIV cultivars performed better than MGV soybeans when planted in May. When planted in June, however, no difference existed between cultivars. At only one of seven locations did a yield difference occur as the result of row width, and the 10-in. row yields were better than those from 30-in. rows. Under these low-yielding conditions, row spacing did not have an effect. Weeds must be controlled, especially in a dry year such as 1998, to allow crops to survive and potentially produce profitable seed yields. The MgIII and MgIV cultivars were harvested a minimum of 20 days earlier when planted in May than when planted in June. May planting would allow for potentially easier and more timely double-cropped wheat planting or fall tillage. The MGV soybeans generally did not yield well or reach harvest maturity before November.
For May plantings, no differences were evident between tillage systems, but in a dry year, the only harvestable stands planted in June were no-till. Because funding was discontinued, this will be the last year of this study.

Introduction
The 1995 Farm Bill and the release of Roundup® Ready Soybeans have played a major role in the dramatic increase of soybean acres in central Kansas. Acreage has increased by 500% and over 300% since 1995 in the South Central (SC) and Central Crop Reporting Districts, respectively. Traditionally, in the SC district, very few acres were planted to soybeans as a full-season crop unless the field was irrigated. Most of the dryland soybean acreage was planted as an opportunity double crop after wheat harvest. The dryland acres usually were seeded in the first 2 weeks of June. Research results from the 1990's at the Harvey County Experiment Field near Hesston showed consistently decreasing yields as soybean planting was delayed from the first week of May to mid-June. That work also showed that maturity group IV (MGIV) soybeans outyielded maturity group III (MGIII) and maturity group II (MGII) when planted in the first 2 weeks of May. After mid-May, the MGIII soybeans significantly outyielded cultivars in the other two maturity groups. Maturity group II soybeans were always the lowest yielding. In a rotational study at the South Central Experiment Field near Hutchinson, MGII soybeans planted in late April have yielded erratically (0-40+ bu/a) but have averaged 25 bu/a for 7 years. In addition, a delay in planting from early May to mid-June will delay physiological maturity approximately 1 day for every 3 days delayed. Consequently, harvest dates are generally up to 2 weeks earlier with earlier plantings. This experiment, funded in part by the Kansas Soybean Commission, evaluated the yield response of three different maturity groups of soybeans planted in two different row spacings at two planting dates (early to mid May and early to mid June) at intervals of approximately 28 days. This was the first, and final, year of the study.
(weedy and 4.75 in. rainfall) may have led to earlier infestations of charcoal rot in the MGIII plots, which could have resulted in lower seed yields. At the Coady, Cox, and conventionaltilled Isabel sites (Table 21), MGIII soybeans significantly outyielded MGIV soybeans, similar to results from Hesston when both groups were planted in mid May and later. May-planted MGV soybeans yielded the lowest at these four sites. The MGV plants were green and functioning all summer, but extreme heat and drought resulted in very low pod set and seed fill.
May-planted soybeans tended to have higher yields than those planted in June (Table 22). No difference existed in yields of conventionally tilled, May-planted MGIV and MGIII soybeans at the Duncan farm, but the MGIV soybeans produced greater yields than the May planted MGV soybeans and all June planted plots. However, May-planted MGIII soybeans did not significantly outyield plots of MGIII or MGIV soybeans planted in June. Conventional-tilled MGV soybean yields were not affected by planting date and were very low, but not significantly lower than those of June-planted MGIII and MGIV soybeans. All MGV and June MGIII and MGIV plantings on the Duncan farm were heat and/or drought stressed during the critical reproductive stages from bloom through pod fill, which lowered yields. At Wellington, May-planted MGIII and MGIV soybeans outyielded all other treatments (Table 22). Yields did not vary between May-and June-planted MGV plots, reflecting the same conditions as those at the Duncan farm. No differences in yield between maturity groups were detected in Juneplanted plots. Less than 60% of the normal precipitation fell at Wellington from June through September, and when coupled with extremely high temperatures, resulted in very low soybean yields. May plantings were favored. Timely and above-normal July precipitation resulted in acceptable no-till soybean yields at Isabel, regardless of planting date or maturity group (Table 22). May-and June-planted MGIV yields were similar and no greater than yields of Mayplanted MGIII soybeans. Yields of June-planted MGIII soybeans were less than those of Mayplanted MGIV plots and no greater than those of MGV plots planted in June. As was the case at the Duncan farm and Wellington, MGV soybeans were the lowest yielding at the site; however, no yield differences existed in the June planting dates among maturity groups.
The improved performance of the MGV soybeans with June planting and adequate rainfall is similar to results from southeast Kansas where MGV cultivars are planted frequently in June and into early July in double-cropped systems after wheat.
Conventional vs no-till systems were compared at the Duncan farm and at Isabel, but only for the May planting dates (Table 23). The difference in tillage significantly affected yields on the Duncan farm, but not at Isabel. Yields of notill soybeans at the Duncan farm were only ½ and b of yields of conventionally tilled soybeans when MGV yields were included and excluded, respectively, from the analysis. No-till MGV plots had no harvestable yield at the Duncan farm. Weed control was not achieved in the no-till plots at planting, and season-long weed pressure took a heavy toll on soybean plants, especially on the MGV soybeans, which was reflected in the yield. Conversely, conventional-tilled plots were weed free at planting, and a light shower within 24 hours of planting activated the preemergent herbicides, which resulted in good weed control throughout the season. The lack of significant precipitation and surface moisture throughout the growing season did not favor later germination and establishment of weeds. At Isabel, yields of no-till and conventional-tilled plots yields were similar within maturity groups and between MGIII and MGIV (Table 23). However, MGV soybean yields were the lowest in the study.   LSD (0.10) 6.5 2.2 7.5 † Yields at a location must differ by more than the LSD to be considered significantly different.