Kansas Fertilizer Research 2006

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Introduction
Fertilizer companies continue to evaluate different products and processing technology for crop-nutrient production. For several years, Mosaic Company has been looking at several new formulations of P fertilizer products. Studies have been conducted in several states and on crops; we are helping evaluate these products for wheat in the central Great Plains. Studies were established in Saline County in central Kansas and Norton County in northwest Kansas to evaluate several granular fertilizer products containing various amounts of nitrogen, sulfur and zinc.

Procedures
Soil tests for these locations are presented in Table 1. Broadcast or incorporated nitrogen (N), nitrogen phosphorus (NP) or nitrogen phosphorus sulphur (NPS) applications were applied on September 22, 2006, and wheat was planted within two weeks. Both locations were top-dressed (80 lbs/a N) in late February 2006.

Results
The year 2006 was a difficult year for wheat in parts of Kansas with drought conditions and late freezes in the western part of the state severely limiting yields. However, Saline and Norton Counties weren't affected by spring freezes and both locations caught a very timely spring rain. As a result, yields were very good, although each location was very dry from winter through early spring.
Grain yields were not significantly increased by P application at the Norton County site. However, all P application treatments were higher yielding than the check. Grain P contents were significantly improved by P product application (Table  2).
Both grain yield and grain P content were significantly increased by P application at the Saline County site (Table 3). These studies will be continued in 2007.

Introduction
This study was initiated in 1961 to determine responses of continuous corn and grain sorghum grown under flood irrigation to N, P, and potassium (K) fertilization. The study was conducted on a Ulysses silt loam soil with an inherently high K content. No yield benefit to corn from K fertilization was observed in 30 years and soil K content remained high, so the K treatment was discontinued in 1992 and replaced with a higher P rate.

Procedures
Initial fertilizer treatments in 1961 were N rates of 0, 40, 80, 120, 160, and 200 lb/a N, without P and K; with 40 lb/a P 2 O 5 and zero K; and with 40 lb/a P 2 O 5 and 40 lb/a K 2 O. In 1992, the treatments were changed, with the K variable being replaced by a higher rate of P (80 lb/a P 2 O 5 ). All fertilizers were broadcast by hand in the spring and incorporated before planting. The corn hybrids were Pioneer 3225 (1997), Pioneer 3395IR (1998), Pioneer 33A14 (2000, Pioneer 33R93 (2001 and 2002), DeKalb C60-12 (2003C60-12 ( ), Pioneer 34N45 (2004C60-12 ( and 2005, and Pioneer 34N50 (2006), planted at about 30-32,000 seeds/a in late April or early May. Hail damaged the 2005 and2002 crop and destroyed the 1999 crop. The corn was irrigated to minimize water stress. Furrow irrigation was used through 2000 and sprinkler irrigation has been used since 2001. The center two rows of each plot were machine-harvested after physiological maturity. Grain yields were adjusted to 15.5% moisture.

Summary
Animal wastes are routinely applied to cropland to recycle nutrients, build soil quality, and increase crop productivity. This study evaluates established best management practices for land application of animal wastes on irrigated corn. Swine waste (effluent water from a lagoon) and cattle waste (solid manure from a beef feedlot) have been applied annually since 1999 at rates to meet estimated corn phosphorus (P) or nitrogen (N) requirements, along with a rate double the N requirement. Other treatments were N fertilizer (60, 120, and 180 lb/a N) and an untreated control. Corn yields were increased by application of animal wastes and N fertilizer. Over-application of cattle manure has not had a negative effect on corn yield. For swine effluent, over-application has not reduced corn yields except for 2004, when the effluent had much greater salt concentration than in previous years, causing reduced germination and poor early growth.

Introduction
This study was initiated in 1999 to determine the effect of land application of animal wastes on crop production and soil properties. The two most common animal wastes in western Kansas were evaluated: solid cattle manure from a commercial beef feedlot and effluent water from a lagoon on a commercial swine facility.

Procedures
The rate of waste application was based on the amount needed to meet estimated crop P requirement, crop N requirement, or twice the N requirement (Table 1). The Kansas Department of Agriculture Nutrient Utilization Plan Form was used to calculate animal waste application rates. Expected corn yield was 200 bu/a. The allowable P application rate for the P-based treatments was 105 lb/a P 2 O 5 because soil test P was less than 150 ppm Mehlich-3 P. The N recommendation model uses yield goal less credits for residual soil N and previous manure applications to estimate N requirements. For the N-based swine treatment, the residual soil N levels after harvest in 2001, 2002, and 2004 were great enough to eliminate the need for additional N the following year. No swine effluent was applied to the 1xN treatment in 2002, 2003, or 2005 or to the 2xN requirement treatment, because it is based on 1x treatment (Table 1). The same situation occurred for N-based treatments using cattle manure in 2003. Nutrient values used to calculate initial applications of animal wastes were 17.5 lb available N and 25.6 lb available P 2 O 5 per ton of cattle manure and 6.1 lb available N and 1.4 lb available P 2 O 5 per 1,000 gallons of swine effluent (actual analysis of animal wastes as applied varied somewhat from estimated values, Table 2). Subsequent applications were based on previous analyses. Other nutrient treatments were three rates of N fertilizer (60, 120, and 180 lb/a N), along with an untreated control. The N fertilizer treatments also received a uniform application of 50 lb/a P 2 O 5 . The experimental design was a randomized complete block with four replications. Plot size was 12 rows wide by 45 ft long.
The study was established in border basins to facilitate effluent application and flood irrigation. The swine effluent was floodapplied as part of a pre-plant irrigation each year. Plots not receiving swine effluent were also irrigated at the same time to balance water additions. Cattle manure was handbroadcast and incorporated. The N fertilizer (granular NH 4 NO 3 ) was applied with a 10-ft fertilizer applicator (Rogers Mfg.

Results
Corn yields increased with all animal waste and N fertilizer applications in 2006, as was the case for all years except 2002, when yields were greatly reduced by hail damage (Table 3). The type of animal waste affected yields in five of the seven years, with higher yields from cattle manure than from swine effluent. Averaged across the seven years, corn yields were 14 bu/a greater after application of cattle manure than swine effluent on an N application basis. Over-application (2xN) of cattle manure had no negative impact on grain yield in any year. Over-application of swine effluent reduced yields in 2004 because of considerably greater salt content (two to three times greater electrical conductivity than any previous year), causing germination damage and poor stands. No adverse residual effect from the overapplication has been observed.

Summary
Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated grain sorghum in western Kansas. In 2006, N and P applied alone increased yields about 50 bu/a and 18 bu/a, respectively, but N and P applied together increased yields more than 65 bu/a. Averaged across the past 10 years, sorghum yields were increased more than 50 bu/a by N and P fertilization. Application of 40 lb/a N (with P) was sufficient to produce greater than 90% of maximum yield in 2006 and for the 10-year average. Application of potassium (K) had no effect on sorghum yield throughout the study period.

Introduction
This study was initiated in 1961 to determine responses of continuous grain sorghum grown under flood irrigation to N, P, and K fertilization. The study was conducted on a Ulysses silt loam soil with an inherently high K content. The irrigation system was changed from flood to sprinkler in 2001.

Procedures
Fertilizer treatments initiated in 1961 were N rates of 0, 40, 80, 120, 160, and 200 lb/a N without P and K; with 40 lb/a P 2 O 5 and zero K; and with 40 lb/a P 2 O 5 and 40 lb/a K 2 O. All fertilizers were broadcast by hand in the spring and incorporated before planting. Sorghum (Pioneer 8414 in 1997, and Pioneer 8500/8505 from 1998to 2006 was planted in late May or early June. Irrigation was used to minimize water stress. Furrow irrigation was used through 2000 and sprinkler irrigation has been used since 2001. The center two rows of each plot were machine harvested after physiological maturity. Grain yields were adjusted to 12.5% moisture.

Results
Grain sorghum yields were very good in 2006 and were greater than the 10-year average (Table 1). Nitrogen alone increased yields up to 50 bu/a, whereas P alone increased yields up to 18 bu/a. Nitrogen and P applied together increased yields as much as 60 bu/a. Averaged across the past 10 years, N and P applied together increased yields as much as 55 bu/a. In 2006, 40 lb/a N (with P) produced more than 90% of maximum yields which is similar to the 10year average. Sorghum yields were not affected by K fertilization, which has been true throughout the study period.

Summary
Clean seed yield of endophyte-free tall fescue was greater with late fall nitrogen (N) application than with late winter application and increased with N rates up to 100 lb/a. Forage aftermath was increased with increasing N rates up to 200 lb/a and when all N was applied in late winter. Endophyte infection had no effect on yields of clean seed or aftermath forage.

Introduction
Nitrogen fertilization is important for fescue and other cool-season grasses, but management of N for seed production is less defined, especially because endophyte-free tall fescue may need better management than infected stands. Nitrogen fertilization has been shown to affect forage yields, but data are lacking regarding the yield and quality of the aftermath remaining after seed harvest. The objective of this study was to determine the effects of timing and rate of N applied to endophyte-free and endophyte-infected tall fescue for seed and aftermath forage production.

Procedures
The experiment was established as a split-plot arrangement of a randomized block design with three replications. Whole plots were endophyte-free and endophyte-infected tall fescue. The subplots were a 3×5 factorial arrangement of N fertilizer timing and rate.

Results
Averaged across years and endophyteinfected stands, application of all N fertilizer in late fall resulted in more than 15% greater clean seed yield compared with all N applied in late winter, with the split (50% late fall -50% late winter) application being intermediate ( Figure 1). Clean seed yield increased with increasing rates to 100 lb/a N, but did not seem to benefit from higher N rates. Endophyte infection had no effect on clean seed yield.
Averaged across years and endophyteinfected stands, yield of the forage aftermath left after seed harvest was increased by applying N fertilizer in late winter, compared with late fall, with the split application being intermediate ( Figure 2). Increasing N rates up to 200 lb/a increased forage yield, but the amount of increase diminished with each additional N increment. Endophyte infection had no effect on yield of aftermath forage.

Summary
Corn yield response to tillage selection varied with year. In the second and third years, reduced tillage resulted in greater yields than with no-till and usually with either strip-tillage system. Across years, early spring fertilization and knife (subsurface band) applications of nitrogen (N) and phosphorus (P) solutions resulted in greater yield than N-P fertilizer application in late fall or dribble application.

Introduction
The use of conservation-tillage systems is promoted to reduce the potential for sediment and nutrient losses. In the claypan soils of southeastern Kansas, crops grown with no tillage may yield less than in systems involving some tillage operation. But strip tillage provides a tilled seed-bed zone where early spring soil temperatures might be greater, while leaving residues intact between the rows as a conservation measure similar to no tillage.

Procedures
The experiment was established on a Parsons silt loam in late fall 2002. The experimental design was a split-plot arrangement of a randomized complete block with three replications. The four tillage systems constituting the whole plots were: 1) strip tillage in late fall, 2) strip tillage in early spring, 3) reduced tillage (one pass with tandem disk in late fall and one pass in early spring), and 4) no tillage. The subplots were a 2×2 factorial arrangement of fertilizer timing and fertilizer placement. Fertilizer application timing was targeted for late fall or early spring. Fertilizer placement was dribble [surface band] or knife [subsurface band at 4 in-depth]. Fertilizer rates of 120 lb/a N and 40 lb/a P 2 O 5 were applied in each fluid-fertilizer scheme. Fertilization was done on Dec. 17, 2002, and

Results
Short-season corn yields were affected by a year × tillage interaction. In 2003, there were no differences in short-season corn yields as affected by tillage ( Figure 1). In 2004, however, reduced tillage resulted in greater yield than with no-till or with strip tillage done in the spring. By 2005, reduced tillage resulted in 50% greater yield than with no tillage or either strip tillage system. Averaged across years, knife (subsurface band) applications resulted in nearly 11% greater yield than dribble (surface band) applications did ( Figure 2). Fertilization done in early spring resulted in significantly greater corn yields (118 bu/a) than with late fall fertilization (107 bu/a).

Summary
In 2005, corn yields were lower with no tillage, likely due to reduced plant stand. There were no yield differences due to nitrogen (N) fertilizer placement in the conventional or reduced tillage systems, but knifed fertilizer N increased yields compared with broadcast and dribble application methods in no tillage.

Introduction
Many rotational systems are employed in southeastern Kansas. This experiment was designed to determine the long-term effect of selected tillage and N fertilizer placement options on the yields of short-season corn, wheat, and doublecrop soybean in rotation.

Procedures
A split-plot design with four replications was initiated in 1983, with tillage system as the whole plot and N treatment as the subplot. After 22 years, the rotation was changed in 2005 to begin a short-season corn-wheat-doublecrop soybean sequence.
The three tillage systems were conventional, reduced, and no tillage and were continued in the same areas as during the previous years.
The conventional system consisted of chiseling, disking, and field cultivation. The reduced-tillage system consisted of disking and field cultivation. Glyphosate (Roundup®) was applied to the no tillage areas. The four N treatments for the crop were: a) no N (check), b) broadcast urea-ammonium nitrate (UAN -28% N) solution, c) dribble UAN solution, and d) knife UAN solution at 4 in. deep. Nitrogen rate for corn was 125 lb/a.

Results
In 2005, adding N fertilizer, in general, nearly doubled yields, compared with yields in the no-N control ( Figure 1). There were no differences in yield due to placement method in the conventional and reduced-tillage systems. In the no tillage system, however, knife applications resulted in about 40 bu/a greater yield than with broadcast or dribble applications. The overall lower corn yields with no tillage were likely caused by lower plant stands than in conventional or reducedtillage systems.

Summary
The predominant cropping systems in south central Kansas have been continuous wheat and wheat-grain sorghum-fallow. With continuous wheat, tillage is performed to control diseases and weeds. In the wheatsorghum-fallow system only two crops are produced every three years. Other crops (corn, soybean, sunflower, winter cover crops and canola) can be placed in these cropping systems. To determine how winter wheat (and alternative crop) yields are affected by these alternative cropping systems, winter wheat was planted in rotations following the alternative crops. Yields were compared with yields 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. Over time, however, wheat yields following soybean have increased, reflecting the effects of reduced weed and disease pressure and increased soil nitrogen. But CT continuous winter wheat seems to out-yield 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 predominant dry-land 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. NT systems often increase soil moisture by increasing infiltration and decreasing evaporation. But higher grain yields associated with increased soil water in NT have not always been observed.
Cropping systems with winter wheat following several alternative crops would provide improved weed control (through additional herbicide options) and reduced disease incidence (by interrupting disease cycles). It would also allow producers several options under the 1995 Farm Bill. But the fertilizer nitrogen (N) requirement for many crops is often greater under NT than under 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 and was restructured to include a tillage factor in 1987. The first of the alternative cropping systems, in which wheat follows short-season corn, was established in 1986 and modified in 1996 to a wheat-cover crop-grain sorghum rotation. The second cropping system (established in 1990) has winter wheat following soybean. Both cropping systems use NT seeding into the previous crop's residue. All three systems have the same N rate treatments.

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

Continuous Wheat
These plots were established in 1979. The conventional tillage treatments are plowed immediately after harvest then worked with a disk as necessary to control weed growth. The fertilizer is applied with a Barber metered screw spreader before the last tillage (field cultivation) on the CT and before seeding of the NT plots. The plots are cross-seeded in mid-October to winter wheat. Because of an infestation of cheat in the 1993 crop, the plots were planted to oat in the spring of 1994. The fertility rates were maintained, and the oat was harvested in July. Winter wheat has been planted in mid-October each year since the fall of 1994. New herbicides have aided in the control of cheat in the NT treatments. In the fall of 2005, these plots were seeded to canola. The nitrogen rates and tillage treatments were retained. It is hoped that doing this will give us some field data on the effects of canola on wheat yields in a continuous-wheat cropping system.

Wheat after Corn/Grain Sorghum Fallow
In this cropping system, winter wheat was planted after short-season corn had 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) before planting of winter wheat in mid-October. Fertilizer rates were applied with the Barber metered screw spreader in the same manner as for the continuous wheat. In 1996, the corn crop in this rotation was dropped, and three legumes (winter peas, hairy vetch, and yellow sweet clover) were added as winter cover crops. Thus, the rotation became a wheat-cover crop-grain sorghum-fallow rotation. The cover crops replaced the 25, 75, and 125 N treatments in the grain sorghum portion of the rotation. Yield data can be found in Field Research 2000 KSU Report of Progress SRP 854.

Wheat after Soybean
Winter wheat is planted after the soybean has been harvested in early-to mid-September in this cropping system. As with the continuous-wheat plots, these plots are planted to winter wheat in mid-October. Fertilizer rates are applied with the Barber metered screw spreader in the same manner as for the continuous wheat. Since 1999, a group III soybean has been used. This delays harvest from late August to early October. In some years, this effectively eliminates the potential recharge time before wheat planting.

Wheat after Grain Sorghum in Cover Crop/Fallow-Grain Sorghum-Wheat
Winter wheat is planted into grain sorghum stubble harvested the previous fall. Thus, the soil-profile water has had 11 months to be recharged before planting of winter wheat in mid-October. Nitrogen fertilizer is applied at a uniform rate of 75 lb/a with the Barber metered screw spreader in the same manner as for the continuous wheat. This rotation will be terminated after the harvest of each crop in 2006. For the 2007 harvest year, canola will be introduced into this rotation where the cover crops had been.
Winter wheat is also planted after canola and sunflower to evaluate the effects of these two crops on the yield of winter wheat. Uniform nitrogen fertility is used; therefore, the data is not presented. The yield for wheat after these two crops is comparable to wheat after soybean.

Continuous Wheat
Grain yield data from plots in continuous winter wheat are summarized by tillage and N rate in Table 3. Data for years before 1996 can be found in Field Research 2000 KSU Report of Progress SRP 854. Conditions in 1996 and1997 proved to be excellent for winter wheat production in spite of the dry fall of 1995 and the late-spring freezes in both years. Excellent moisture and temperatures during the grain-filling period resulted in decreased grain-yield differences between the conventional and no-till treatments within N rates. Conditions in the spring of 1998 and 1999 were excellent for grain filling in wheat.
However, the differences in yield between conventional and no-till wheat still expressed themselves (Table 3). In 2000, the differences were wider, up to the 100 lb/a N rate. At that point, the differences were similar to those of previous years. The wet winter and late spring of the 2003-2004 harvest year allowed for excellent tillering and grain fill and yields (Table 2). In 2005, the dry period in April and May seemed to affect the yields in the plots with 0 and 25 lb/a N rates.

Wheat after Soybean
Wheat yields after soybean also reflect the differences in N rate. When comparing the wheat yields from this cropping system with those where wheat followed corn, however, the effects of residual N from soybean production in the previous year can be seen. This is especially true for N rates between 0 and 75 lb in 1993 and between 0 and 125 lb in 1994 (Table 3). 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 for spring wheat reflect the lack of response to nitrogen fertilizer for the spring wheat. Yields for 1997 and 1998 both show the leveling off after the first four increments of N. As with the wheat in the other rotations in 1999, the ideal moisture and temperature conditions allowed the wheat yields after soybean to express the differences in N rate up to 100 lb N/a. In the past, those differences stopped at the 75 lb N/a treatment. When compared with the yields in the continuous wheat, the yield of rotational wheat is starting to reflect the presence of the third crop (grain sorghum) in the rotation. Wheat yields were lower in 2000 than in 1999. This is attributed to the lack of timely moisture in April and May and the hot days at the end of May. This heat caused the plants to mature early and also caused low test weights. In 2004, there was not as much cheat as in 2003; thus, the yields were much improved (Table 3). Yields in 2004 indicate that the wheat is showing a 50-to 75-lb N credit from the soybean and rotational effects. As with the continuous wheat cropping system, the yields in plots with the 0 and 25 lb/a N rate were less than in 2004. 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 lb/a where wheat follows soybean.

Wheat after Grain Sorghum/Cover Crop
The first year that wheat was harvested after a cover-crop grain sorghum planting was 1997. Data for the 1997-2005 wheat yields are in Table 4. Over these nine years, there does not seem to be a definite effect of the cover crop (CC) on yield. This is most likely due to the variance in CC growth within a given year. In years like 1998 and 1999, in which sufficient moisture and warm winter temperatures produced good CC growth, the additional N from the CC seems to carry through to the wheat yields. With the fallow period after the sorghum in this rotation, the wheat crop has a moisture advantage over the wheat after soybean. Cheat was the limiting factor in this rotation in 2003. A more aggressive herbicide control of cheat in the cover crops was started, and the 2004 yields reflect the control of cheat. Management of the grasses in the cover-crop portion of this rotation seems to be the key factor in controlling the cheat grass and increasing yields. This can be seen in the yields for 2005 when compared with the wheat yields, either continuous wheat or in rotation with soybean.

Other Observations
Nitrogen application significantly increased grain N contents in all crops. Grain phosphate content 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 wheat after soybean. 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 and soybean yields can occur. The major weedcontrol problem in the wheat-after-corn system is with grasses. Work is being done to determine the best herbicides and time of application to control grasses.

Soybean and Grain Sorghum in Rotations
Soybean was added to intensify the cropping system in the South Central area of Kansas. Being a legume, soybean also has the ability to add nitrogen to the soil system. For this reason, nitrogen is not applied during the time when soybean is planted in the plots for the rotation. This gives the following crops the opportunity to use the added N and allows checking the yields against the yields for the crop in other production systems. Yield data for soybean following grain sorghum in the rotation are given in Table 5. Soybean yields are affected more by the weather for the given year than by the previous crop. In three out of the nine years, there was no effect of N rates applied to wheat and grain sorghum in the rotation. In the two years that N application rate did affect yield, it was only at the lesser N rates. This is a similar effect that is seen in a given crop. The yield data for grain sorghum after wheat in the soybean-wheatgrain sorghum rotation are in Table 6. As with the soybean, weather is the main factor affecting yield. The addition of a cash crop (soybean), which intensifies the rotation (cropping system), will reduce the yield of grain sorghum in the rotation; compare soybean-wheat-grain sorghum vs. wheatcover crop-grain sorghum in Tables 6 and 7. More uniform yields are obtained in the soybean-wheat-grain sorghum rotation (Table  6) than in the wheat-cover crop-grain sorghum rotation (Table 7).
Other systems studies at the field are a wheat-cover crop (winter pea)-grain sorghum rotation with N rates, and a date of planting, date of termination cover-crop rotation with small grains (oat) and grain sorghum.   1991 1992 1993 1994 1995 1996 2 1997 1998 1999 2000 2001 2002  C V ( % ) 2 6 1 4 6 1 6 6 2 0 7 0 1 2 6 * Unless two yields in the same column differ by at least the least significant difference (LSD), there can be little confidence in one being greater than the other. 1 Nitrogen rate in lb/a. 2 HV hairy vetch, WP winter pea, SC sweet clover. 3 Yields severely reduced by hail. CV (%) 5 18 10 9 10 58 11 24 4 7 * Unless two yields in the same column differ by at least the least significant difference (LSD), there can be little confidence in one being greater than the other. 1 Nitrogen rate in lb/a. 10 * Unless two yields in the same column differ by at least the least significant difference (LSD), there can be little confidence in one being greater than the other. 1 Nitrogen rate in lb/a. 2 HV hairy vetch, WP winter pea, SC sweet clover. 3 Yields affected by hot dry conditions in July and bird damage.

Summary
The effects of the cover crop most likely were not expressed in the first year (1996) grain sorghum harvest (Table 1). Limited growth of the cover crop (winter peas), due to weather conditions, produced limited amounts of organic nitrogen (N). Therefore, the effects of the cover crop were limited and varied compared with those of fertilizer N. The wheat crop for 1998 was harvested in June. The winter pea plots were then planted and were terminated the following spring before 1999 grain sorghum plots were planted. The N rate treatments were applied and grain sorghum was planted on June 11, 1999. Winter wheat was again planted on the plots in October  Table 1, and were planted to grain sorghum in June 2005.

Introduction
There has been a renewed interest in the use of winter cover crops as a means of soil and water conservation, as a substitute for commercial fertilizer, and for the maintenance of soil quality. One of the winter cover crops that may be a good candidate is winter pea. Winter pea is established in the fall, overwinters, produces sufficient spring foliage, and is returned to the soil before planting of a summer annual. Because it is a legume, there is a potential for adding nitrogen to the soil system. With this in mind, research projects were established at the South Central Experiment Field to evaluate the effect of winter pea and its ability to supply N to the succeeding grain sorghum crop, compared with commercial fertilizer N, in a winter wheat-winter peagrain sorghum rotation.

Procedures
The research is being conducted at the KSU Research and Extension South Central Experiment Field, Hutchinson. The soil in the experimental area is an Ost loam. The site had been in wheat before starting the covercrop cropping system. The research used a randomized block design and was replicated four times. Cover-crop treatments consist of fall-planted winter peas with projected termination dates in April and May and no cover crop (fallow). The winter peas are planted into wheat stubble in early September at a rate of 35 lb/a in 10-inch rows with a double disk opener grain drill. Before termination of the cover crop, above-ground biomass samples are taken from a one-square-meter area. These samples are used to determine forage yield (winter pea and other) and forage nitrogen and phosphate content for the winter pea portion. Fertilizer treatments consist of four fertilizer N rates (0, 30, 60, and 90 lb/a N). Nitrogen treatments are broadcast applied as NH 4 NO 3 (34-0-0) before planting of grain sorghum. Phosphate is applied at a rate of 40 lb P 2 O 5 in the row at planting. Grain sorghum plots are harvested to determine grain yield, moisture, test weight, and grain nitrogen and phosphate content. The sorghum plots are fallowed until the plot area is planted to wheat in the fall of the following year. The fertilizer treatments are also applied before planting wheat.

Winter Pea/Grain Sorghum
Results for winter pea cover crop and grain sorghum were summarized in the Field Research 2000 Report of Progress SRP 854 pages 139-142. The grain sorghum yields by N rate (Table 1) were similar to the wheat yields in the long-term N-rate study. The first increment of N resulted in the greatest change in yield, and the yields tended to peak at the 60 lb N rate treatment, regardless of the presence or lack of winter pea.

Winter Wheat
The fall of 2000 was wet, after a very hot, dry August and September. Thus, the planting of wheat was delayed. Fall temperatures were warm, allowing the wheat to tiller into late December. January and February both had above-normal precipitation. April, May, and June were slightly below normal in both precipitation and temperature. Wheat yields reflected the presence of the winter pea treatments, as well as the reduced yields in the grain sorghum for the no-pea treatment plots. Test weight of the grain was not affected by pea or fertilizer treatment, but was affected by the rainfall at harvest time. This was also true for the percentage of nitrogen in the seed at harvest. A concern with the rotation is weed pressure. The treatment with April-termination pea plus 90 lb/a N had significantly more weeds in it than any of the other treatments. Except for this treatment, there were no differences noted for weed pressure. Grain yield data are presented in Table 2. With the earlier planting for the 2004 crop, the wheat should have had a better chance to tiller, but the fall was wet and cold, limiting fall growth.
As this rotation continues and the soil system adjusts, it will reveal the true effects of the winter cover crop in the rotation. It is important to remember that in the dry (normal) years, the soil water (precipitation) during the growing season most likely will not be as favorable as it was in 1999, and the water use by the cover crop will be the main influence on the yield of succeeding crop.

Summary
Wheat and grain sorghum were grown in three no-till crop rotations, two of which included either a late-maturing Roundup Ready® soybean or a sunn hemp cover crop established following wheat harvest. Nitrogen (N) fertilizer was applied to both grain crops at rates of 0, 30, 60, and 90 lb/a. Experiments were conducted on adjacent sites where different phases of the same rotations were established.
On the first site, late-maturing soybean and sunn hemp cover crops grown for the second time in the rotations (2004) contained 90 and 125 lb/a of N, respectively. Residual effects of soybean on wheat were similar to those of sunn hemp. In the very dry wheat growing season of 2005 and 2006, plant heights and N levels showed no response to cover crop, but increased significantly with N rate. Wheat yield increases of 4.4 and 6.3 bu/a, respectively, in rotations with soybean and sunn hemp occurred only at 60 lb/a N. Grain test weight was not meaningfully affected by either cover crop or N rate.
On a second site, grain sorghum followed cover crops grown for the first time in the rotations. Soybean and sunn hemp produced an average of 2.42 and 4.14 ton/a of aboveground dry matter. Corresponding nitrogen (N) yields of 103 and138 lb/a were potentially available to the succeeding grain sorghum crop. In the rotation without a cover crop, grain sorghum leaf N concentrations were significantly higher only at the two highest rates of fertilizer N. A similar trend in leaf N occurred in grain sorghum following soybean. On the other hand, sorghum leaf N was higher at all rates of N and showed no response to N rate in the rotation with sunn hemp. When averaged across N fertilizer rates, soybean and sunn hemp significantly increased sorghum leaf nutrient levels by 0.12% N and 0.20% N, respectively.
Cover crops did not affect grain sorghum plant population or grain test weight and tended to shorten only slightly the length of time to reach half bloom stage. At zero fertilizer N, soybean and sunn hemp increased sorghum yields by 30.9 and 34.7 bu/a. Averaged over N rate, these respective yield increases were 12.5 and 17.8 bu/a . Without a cover crop in the rotation, sorghum yields increased with N rate and reached a maximum of 100.6 bu/a at 60 lb/a. N rate did not affect yield of sorghum after soybean and increased yield of sorghum following sunn hemp significantly only at 60 lb/a N with a maximum of 109 bu/a.

Introduction
Research at the KSU Harvey County Experiment Field over an 8-year period explored the use of hairy vetch as a winter cover crop following wheat in a winter wheatsorghum rotation. Results of long-term experiments showed that, between September and May, hairy vetch can produce a large amount of dry matter with an N content on the order of 100 lb/a. But significant disadvantages also exist in the use of hairy vetch as a cover crop. These include the cost and availability of seed, interference with the control of volunteer wheat and winter annual weeds, and the possibility of hairy vetch becoming a weed in wheat after sorghum.
New interest in cover crops has been generated by research in other areas showing the positive effect these crops can have on the overall productivity of no-till systems.
In the current experiment, late-maturing soybean and sunn hemp, a tropical legume, were evaluated as summer cover crops for their impact on no-till sorghum grown in the spring following wheat harvest as well as for residual effect on double-crop no-till wheat after grain sorghum. In 2002 and2004, in the first two cycles of these rotations at the initial experiment location, the two cover crops produced average N yields of 118 and 122 lb/a, respectively. When averaged over N rates, soybean and sunn hemp resulted in two-year average grain sorghum yield increases of 6.3 and 12 bu/a. Residual effects of cover crops on wheat averaged over N rates at the beginning of the second cycle were evidenced by yield increases of 4.0 and 2.3 bu/a.

Procedures
The experiments were established on adjacent Geary silt loam sites which had been utilized for hairy vetch cover crop research in a wheat-sorghum rotation from 1995 to 2001. In keeping with the previous experimental design, soybean and sunn hemp were assigned to plots where vetch had been grown, and the remaining plots retained the treatment with no cover crop. The existing factorial arrangement of N rates on each cropping system also was retained. In 2006, wheat was produced on site 1 at the beginning of the third cycle of the rotations. Grain sorghum was grown on the second site in the first cycle of the rotations.

Wheat
Weeds in wheat stubble were controlled with Roundup Ultra Max II® herbicide applied nine days before planting the cover crop. Asgrow AG701 Roundup Ready® soybean and sunn hemp seed were treated with respective rhizobium inoculants and no-till planted in 8-inch rows with a CrustBuster stubble drill on July 9, 2004, at 60 lb/a and 10 lb/a, respectively. Sunn hemp began flowering in mid-September and was terminated at that time by a combination of rolling with a crop roller and applying 22 oz/a of Roundup Ultra Max II®. Soybean was rolled after initial frost in early October. Forage yield of each cover crop was determined by harvesting a 3.28 feet 2 area in each plot just before termination. Samples subsequently were analyzed for N content.
Weeds were controlled during the fallow period after cover crops with Roundup Ultra Max II®, 2,4-D LVE and Clarity. Pioneer 8500 grain sorghum treated with Concept® safener and Cruiser® insecticide was planted at approximately 42,000 seeds/a on May 23, 2005. Atrazine and Dual II Magnum® were applied pre-emergence for residual weed control shortly after sorghum planting.
All plots received 37 lb/a of P 2 O 5 banded as 0-46-0 at planting. Nitrogen fertilizer treatments were applied as 28-0-0 injected at 10 inches from the row on June 27, 2005. Grain sorghum was combine harvested on September 15. Nitrogen rates were reapplied as broadcast 34-0-0 on October 25, 2005. Jagger winter wheat was then no-till planted at 90 lb/a with 32 lb/a P 2 O 5 fertilizer banded as 0-46-0 in the furrow. Wheat was harvested on June 15, 2006.

Grain Sorghum
Weeds were controlled and cover crops managed with procedures similar to those previously noted for site 1. Soybean and sunn hemp seed were no-till planted on July 9, 2005 and terminated in late September. Pioneer 8505 grain sorghum treated with Concept® safener and Cruiser® insecticide was planted at approximately 40,000 seeds/a on July 1, 2006. Atrazine and Dual II Magnum® were preplant applied for residual weed control. The entire site received 37 lb/a of P 2 O 5 banded as 0-46-0 at planting. Nitrogen fertilizer treatments were applied as 28-0-0 injected at 10 inches from the row on July 19, 2006. Grain sorghum was combineharvested on November 9.

Wheat
During the nine days preceding cover crop planting in 2004, rainfall totaled 1.82 inches. The next rains occurred about two weeks after planting, when 4 inches were received over a three day period. Stand establishment was good with both soybean and sunn hemp. Although July rainfall was above normal, August and September were drier than usual. Late-maturing soybean reached an average height of 24 inches, showed limited pod development, and produced 2.11 ton/a of above-ground dry matter with an N content of 2.11% or 90 lb/a (Table 1). Sunn hemp averaged 72 inches in height and produced 3.19 ton/a with 1.95% N or 125 lb/a of N. Soybean and sunn hemp suppressed volunteer wheat to some extent, but failed to give the desired level of latesummer control.
In 2005, soybean increased sorghum yields at all but the 90 lb/a N rate, while sunn hemp in the rotation improved yields at all N rates. The positive effect of soybean and sunn hemp cover crops was seen in respective sorghum yield improvements of 9.7 and 13.4 bu/a when averaged over N rate. Yields averaged over cropping systems increased significantly with each 30 lb/a increment of fertilizer N.
The residual effect of cover crops in 2006 on winter wheat plant height was generally minor and, across cropping systems, increased by 4 to 7 inches with the first increment of N fertilizer. Plant N in wheat at early heading indicated that there was no residual N contribution from cover crops. Fertilizer significantly increased plant N incrementally with 60 and 90 lb/a of N. Wheat yields tended to be slightly greater in rotations with a cover crop. In the case of sunn hemp, the yield advantage of 3.2 bu/a was significant when averaged over N rates. But, most of the rotation effect on yield was observed at N rates less than 90 lb/a. Cover crops had a minor but positive effect on grain test weight, mainly at low N rates. Test weight tended to increase slightly with 30 and 60 lb/a of N.

Grain Sorghum
During the week preceding cover crop planting in 2005, rainfall totaled 1.89 inches. A 1-inch rain fell three days after planting, but the remainder of July had a total of only 0.58 inch. Stand establishment was good with both soybean and sunn hemp. August rainfall was well above normal. September was much drier than usual.
Late-maturing soybean reached an average height of 27 inches, had minor pod development, and produced 2.42 ton/a of above-ground dry matter with an N content of 2.11% or 103 lb/a (Table 2). Sunn hemp averaged 86 inches in height and produced 4.14 ton/a with 1.67% N or 138 lb/a of N. Soybean and sunn hemp gave partial suppression of volunteer wheat, but did not eliminate the need for herbicide control ahead of the wheat planting season.
Grain sorghum final stands averaged 26,717 plants/a. In 2006, July and August had a total of 31 days with temperatures of 95 degrees or higher, and 13 days with temperatures of 100 to 108 degrees F. July was dryer than usual. Above-normal rainfall in August, coupled with more moderate temperatures during the second half of the month, greatly benefitted the sorghum crop. Mean temperatures in September and October were 5.4 and 2.6 degrees F below normal. September rainfall was 1.8 inches below the long-term average, and October also was dryer than usual. The first freezing temperatures of fall arrived on October 18. This and subsequent freezes hastened sorghum grain maturation to some extent.
Where no cover crop was used in the rotation, grain sorghum leaf N concentration increased with each increment of N fertilizer, reaching significantly higher levels with 60 and 90 lb/a N. Similarly, where sorghum followed soybean, leaf N increased significantly only at the 60 and 90 lb/a rates, but without an incremental relationship to N rate. However, in the rotation with sunn hemp, sorghum leaf N tended to be higher at all rates of fertilizer and had no meaningful response to N rate. The main effect of soybean and sunn hemp, averaged across N fertilizer rates, significantly increased sorghum leaf nutrient levels by 0.12% N and 0.20% N, respectively.
Cover crops did not affect grain sorghum plant population or grain test weight. On average, sorghum following sunn hemp tended to reach half-bloom stage slightly earlier than in the other rotations. The number of heads/plant increased with both cover crops and N rates. At zero fertilizer N, sorghum after soybean and sunn hemp produced yields of 92.0 and 95.8 bu/a, representing increases of 30.9 and 34.7 bu/a. The main effects of cover crops averaged over all N rates were evidenced by respective yield increases of 12.5 and 17.8 bu/a . Without a cover crop in the rotation, sorghum yields increased with fertilizer rate and reached a maximum of 100.6 bu/a at 60 lb/a N. Sorghum following soybean averaged 96.1 bu/a and did not respond significantly to N rate. In the rotation with sunn hemp, sorghum grain production increased significantly only at 60 lb/a N, with the high of 109 bu/a.    2005. 4 Days from planting to half bloom. 5 Flag leaf at late boot to early heading.

Introduction
Corn producers in East Central and Southeast Kansas need to offset rising fuel and fertilizer costs and must also reduce sediment and nutrient losses via crop land runoff. Cutting back on tillage and subsurface banding fertilizers are possible management strategies. However, that can be a challenge for corn producers in these areas because of an abundance of imperfectly drained soils and frequent spring rains. The extra residue and slower soil drying associated with no-till can keep no-till fields cool and wet longer in the spring and can delay planting and slow early-season corn growth. Application of pop-up or besidethe-row starter banded fertilizers can offset most of the slowed early-season corn growth with no-till, but delayed planting, reduced plant stands, and the inconvenience of applying starter fertilizers at planting continue to be a deterrent to no-till acceptance.
Strip-tillage is a compromise conservation tillage system. It is a system that includes some tillage, but only where the seed rows are to be planted. Row middles are left untilled. The tilled in-the-row strips provide a raised, loosened seed bed, which improves drainage, warming, and drying. Strip-tillage also allows fertilizers to be precision applied under the row in the same tillage pass, which can offset the need for starter fertilizer application at planting. Strip-tillage with fertilizers banded under the row would seem to be a good fit for growing corn in East Central Kansas.
The objectives of this study were 1) to evaluate the performance of strip-till and notill systems for corn in East Central Kansas using different nitrogen (N) fertilizer rates, timing and placement methods, and 2) to assess if there is any yield drag from applying strip-till nitrogen (N)-phosphorus (P)potassium (K)-sulphur (S) fertilizers in the fall versus all fertilizers banded at planting.

Procedures
This study was conducted from 2003 to 2005 at the East Central Kansas Experiment Field near Ottawa, on a somewhat poorly drained Woodson silt loam soil. The field site had been managed no-till for five years prior to starting this study. The experiment design was a randomized complete block with four replications. Tillage and fertilizer treatments and dates that the tillage and fertilization operations were performed are shown in Table 1. The crop preceding the 2003 corn crop was corn and the crops preceding the 2004 and 2005 corn crops were soybean. The herbicides applied for pre-plant weed control were 1qt/a atrazine 4L + 0.66pt/a 2,4-D LVE + 1 qt/a COC. Corn planting was on April 10, 2003, April 15, 2004, and April 13, 2005. Pioneer 35P12 corn was planted all years. Seed-drop was 23,500 seeds/a. After planting, pre-emergence herbicides were applied which included 0.5 qt/a atrazine 4L and1.33 pt/a Dual II Magnum. Plant stand counts, early-season corn growth, and grain yields were taken to evaluate the tillage and fertilization systems. Plant stands were measured by counting all plants in the center two rows of each plot. Early-season corn growth was determined by harvesting, drying and weighing plant tissue from six randomly selected corn plants from each plot at the six-leaf corn growth stage. Grain yields were measured by machine harvesting and weighing the corn from the center two rows of each four-row, 10-ft wide x 40-ft long plots. Harvest was on August 23, 2003, July 10, 2004, and July 8, 2005.

Results
The 2003 corn growing season was hot and dry. Rainfall during April, May, and June was normal, but July and most of August were very hot and dry.

Plant Populations and Early Corn Growth
Tillage and fertilization systems produced statistically significant differences in plant populations and early-season corn growth (Table 1, Figure 1). Plant populations, overall, tended to be better and emergence was more uniform for corn planted using strip-tillage than with no-till. When averaged across all fertilizer treatments, plant populations for 2003 were 15% greater with strip-till compared to no-till. In 2004, strip-till stands increased 7%, and in 2005 plant stands increased 10% with strip-till compared to notill. The fertilizer N rates and the placement and timing of the fertilizer applications had no effect on plant stands (Figure 1).
In addition to increasing plant stands, Strip-till also increased early-season plant growth compared to no-till. In 2003, V6 plant dry-weights, when averaged across all rates of N (0, 40, 80, and 120 lb/a N), were 25% greater with strip-till and fall-applied fertilizer and 39% greater with strip-till and planter banded fertilizer, compared to no-till (Table  1). Overall, the strip-till system with all the fertilizer applied at planting produced the most early-season corn growth. In 2004, both the strip-till and no-till systems with fertilizers banded at planting produced more earlyseason growth than strip-till with all fertilizers banded below the row. In 2005, the treatment effects were similar to 2003. Averaged across all growing seasons, most early-season growth occurred when strip tilled corn received 40 lb/a N plus P, K, and S at planting. As the rate of N in the planting time fertilizer bands increased above 40 lb/a, early-season corn growth tended to decline, suggesting possible sensitivity to fertilizer salts or free ammonia with high rates of N and planter-banded fertilizers ( Figure 2).

Yield
Strip-tillage, overall, produced better yields compared to no-till (Table 1). In 2003, strip-tillage by itself increased corn yield 12 bu/a compared to no-till. In 2004 and 2005, yields were increased 9 and 10 bu/a, respectively. Yield increases were most likely the result of increased plant stands. There was no evidence that N-P-K-S fertilizers striptill applied in the fall performed worse than fertilizers applied at planting time, suggesting a possible wide window for strip-till fertilizer applications (Figure 3). Splitting the strip-till fertilizer application (80-15-2.5-2.5 fall + 40-15-2.5-2.5 at planting) produced a significantly higher yield one year (Table 1). From a grower's perspective, that may not be sufficient enough to justify the application of fertilizers at planting time. The standard striptill fertilization method, with all of the fertilizer injected below the row in the same tillage pass, would seem to be the most practical system. This system should eliminate many of the production concerns associated with notill and also afford many of the environmental and moisture conservation benefits of no-till.

Summary
A series of corn and grain sorghum studies were conducted across the state over the past several years to help refine the information needed for crop nutrient recommendations. As part of this project, a long-term grain sorghum study was established at the Tribune Experiment Station. This location is irrigated in order to maximize the probability of obtaining meaningful information each crop year. Since 2004, this study has had annual phosphate application treatments of 0, 20, 40, 80, and 120 lb/a of P 2 O 5 . Grain yields have generally increased with increasing phosphate rates of up to 80 lb/a of P 2 O 5 .

Introduction
Over the past four years, several corn and grain sorghum studies have been conducted across the state in order to improve crop nutrient phosphorus (P) and potassium (K) recommendations. In order to meet this objective, the following information is being gathered from various studies conducted across the state of Kansas; 1) crop response to various rates of P and/or K application at various soil test levels, 2) percent sufficiency (for maximum yield) at various soil test levels, 3) amounts of P and K nutrient application/ crop removal to change soil test levels, 4) amounts of P and K removed in the harvested grain, and, 5) relationship among common P soil test methods used in Kansas (Bray P1, Mehlich 3 and Olsen P).
This project was initiated for the 2003 crop and continued through the 2005 crop year -while this particular study was initiated in 2004 and will continue into the future. After a wide range of P soil tests are established with these treatments, the study treatments will change to fit evolving grain sorghum fertilization issues.

Procedures
Soil samples from the 0-to 6-inch depth were collected from individual plots. Phosphorus rates of 0, 20, 40, 80, and 120 lbs/a P 2 O 5 were preplant broadcast applied in late winter and incorporated with subsequent tillage. Grain yields were obtained by harvesting the center two rows of each plot. The treatments were replicated six times.

Results
Grain yields for the 2004, 2005, and 2006 crop years are reported in Table 1. Harvested grain sorghum yield responded to P fertilizer application each year and were optimized with about 80 lb/a P 2 O 5 per year. At this location, current Kansas State University P sufficiency recommendations would suggest about 45 lb/a P 2 O 5 each year. This is a bit lower than the optimum rate for this study in these crop years. a grain sorghum yield potential of 120 bu/a and a Mehlich-3 P soil test value of 7 ppm P, Soil samples from the 0-6 inch depth were collected from individual plots at some locations and from individual replications at others. For phosphorus, Bray P1 and Mehlich-3 soil test procedures were run on individual samples. While some of the plots were calcareous (contained free calcium carbonate), the Bray P1 soil test extractant was highly correlated to the Mehlich-3 and Olsen P soil test procedures (Figure 1).

Summary
A series of corn and grain sorghum studies have been conducted across the state over the past several years to help refine the information needed for crop nutrient recommendations. As part of this project, a long-term irrigated corn study was established at the Tribune Experiment Station. Since 2004, this study has had annual phosphate application treatments of 0, 20, 40, 80, and 120 lb/a P 2 O 5 . Grain yields generally increased with increasing phosphate rates up to 80-120 lb/a P 2 O 5 .

Introduction
Over the past four years, several corn and grain sorghum studies have been conducted across the state in order to improve crop nutrient phosphorus (P) and potassium (K) recommendations. In order to meet this objective, the following information is being compiled from various studies conducted across the state of Kansas; 1) crop response to various rates of P and/or K application at various soil test levels, 2) percent sufficiency (for maximum yield) at various soil test levels, 3) amount of P and K nutrient application/crop removal to change soil test levels, 4) amounts of P and K removed in the harvested grain, and, 5) relationship among common P soil test methods used in Kansas (Bray P1, Mehlich-3 and Olsen P).
This project was initiated in 2003 and continued through 2005. This particular study started in 2004 and will continue into the future. After a wide range of P soil tests are established with these treatments, the study treatments will change to fit evolving corn fertilization issues.

Procedures
Soil samples from the 0-to 6-inch depth were collected from individual plots. Phosphorus rates of 0, 20, 40, 80, and 120 lb/a P 2 O 5 were preplant broadcast applied in late winter and incorporated with subsequent tillage. Grain yields were obtained by harvesting the center two rows of each plot.The treatments were replicated six times.

Results
Grain yields for the 2004, 2005 and 2006 crop years are reported in Table 1. Harvested corn grain yield responded to P fertilizer application each year and were optimized with about 80 to 120 lb/a P 2 O 5 per year. At this location, current Kansas State University P sufficiency recommendations would suggest about 55 lbs/a of P 2 O 5 each year for a 200 bu/a yield goal for corn. This is lower than the 80 lb/a to 120 lb/a P 2 O 5 rate required for optimum production for this study in these years.
Soil samples from the 0-to 6-inch depth were collected from individual plots at some locations and from individual replications at others. For phosphorus, Bray P1 and Mehlich-3 soil test procedures were run on individual samples. While some of the plots were calcareous (contained free calcium carbonate), the Bray P1 soil test extractant was highly correlated to the Mehlich-3 and Olsen P soil test procedures (Figure 1).

Summary
While relatively low potassium (K) soil test values are found on some coarsely textured soils in southwest Kansas, it is generally thought that these soils would not be as responsive to K application as eastern Kansas soils with similar soil test values. Corn grain yields were significantly increased with K application at one site (15% level) and were not affected at another nearby site.

Introduction
Relatively low K soil test levels can be found on coarsely textured soils in much of south central and southwest Kansas. However, these soils do not seem to be as responsive to applied fertilizer K as medium-fine textured soils in the eastern part of Kansas. The number of fields exhibiting K deficiency of corn in the eastern part of the state on soils testing greater than commonly accepted critical values are increasing. As a result, there is more interest in determining if the commonly used K soil test and critical values are useful in western Kansas. With this in mind, a simple application study with and without fertilizer K was conducted on low K soil test, irrigated sandy soils in Stevens county.

Procedures
Soil samples from the 0-to 6-inch soil depth were collected from two fields and analyzed for exchangeable soil test potassium. The west location was located on the top of a hill within a field and was finer textured than the east location. The east location was in a low spot within an irrigated field.
Potassium application rates of 0 and 120 lb/a K 2 O were broadcast applied to these sprinkler irrigated fields and replicated four times in each of two studies. Corn grain was hand harvested from 20 feet of row in the center of each plot.

Results
Corn yields were somewhat variable within the studies and random variability relatively high. This is largely due to the variability in soils within these rather sandy fields.
Grain yields were significantly increased at the lower testing west location (p > f = 0.15), but were not significantly different at the east site (only trended higher). While no firm conclusions can be drawn from these efforts, it seems that these irrigated, coarsely textured soils may respond to fertilizer K but may be less responsive than eastern Kansas soils. The east location had soil test values higher than expected critical K soil test values, while the west location was precisely at the established critical K soil test value.
These sites were both initially thought to be lower in soil test potassium than what they were ultimately shown to be. At least part of this difference may be related to sampling depth. It seems that 0-to 6-inch soil samples do not provide as low of K soil test results as samples collected to a deeper depth. Initial samples were collected to a depth of about 10 to 12 inches.