Southwest Research-Extension Center, Field Day 2013

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D. Bond and J. Slattery
In 2012, record-low annual precipitation of 7.49 in. was recorded, which is 10.41 in. below normal. The previous record of 7.76 in. was set in 1934. Ten months had belownormal precipitation. April (2.21 in.) was the wettest month. The largest single amount of precipitation was 1.12 in. on April 3. November, the driest month, recorded no precipitation. Snowfall for the year totaled 4.5 in.; February, March, and December had 0.2, 0.5, and 3.8 in., respectively, for a total of 12 days of snow cover. The longest consecutive period of snow cover, 5 days, occurred January 1 through 5.
Mean air temperature was above normal for 11 months. March had the greatest departure above normal (8.7°F), and October had the only departure below normal (-1.5°F). Temperatures were 100°F or higher on 39 days, which is 28 days above normal. Temperatures were 90°F or higher on 88 days, which is 25 days above normal. The latest spring freeze was April 16, which is 20 days earlier than normal; the earliest fall freeze was October 7, which is the normal date. This produced a frost-free period of 174 days, which is 20 days more than the normal of 154 days.
Open-pan evaporation from April through September totaled 84.01 in., which is 12.61 in. above normal. Wind speed for this period averaged 4.9 mph, which is 0.4 mph less than normal.
The 2012 climate information for Tribune is summarized in Table 1. Fallow Replacement Crops (Cover Crops, Annual Forages, and Grain Pea) Impact on Wheat Yield Introduction Interest in replacing fallow with a cash crop or cover crop has necessitated research on soil water and wheat yields following a shortened fallow period. Fallow stores moisture, which helps stabilize crop yields and reduce the risk of crop failure; however, only 25 to 30% of the precipitation received during the fallow period of a no-till wheat-fallow rotation is stored. The remaining 85 to 70% precipitation is lost, primarily to evaporation. Moisture storage in fallow is more efficient earlier in the fallow period, when the soil is dry, and during the winter months when the evaporation rate is lower. It may be possible to increase cropping intensity without reducing winter wheat yield. This study evaluated replacing part of the fallow period with a cover, annual forage, or short-season grain crop on plant-available water at wheat planting and winter wheat yield.

Procedures
Fallow replacement crops (cover, annual forage, or short-season grain crop) were grown during the fallow period of a no-till wheat-fallow cropping system every year from 2007 through 2011. Fallow replacement crops were either grown as cover, harvested for forage (annual forage crop), or harvested for grain. Both winter and spring crop species were evaluated. Winter species included yellow sweet clover (Melilotus officinalis (L.) Lam.) hairy vetch (Vicia villosa Roth ssp.), lentil (Lens culinaris Medik.), Austrian winter forage pea (Pisum sativum L. ssp.), Austrian winter grain pea (Pisum sativum L. ssp.), and triticale (×Triticosecale Wittm.). Spring species included lentil (Lens culinaris Medik.), forage pea (Pisum sativum L. ssp.), grain pea (Pisum sativum L. ssp.), and triticale (×Triticosecale Wittm.). Crops were grown in monoculture and in two-species mixtures of each legume plus triticale. Crops grown for grain were grown in monoculture only. Winter lentil was grown in place of yellow sweet clover beginning in 2008. Crops grown in place of fallow were compared with a wheat-fallow and continuous wheat rotation for a total of 16 treatments ( Table 1). The study design was a split-splitplot randomized complete block design with four replications; crop phase (wheatfallow) was the main plot, fallow replacement was the split-plot, and fallow replacement method (forage, grain, or cover) was the split-split-plot. The main plot was 480 ft wide and 120 ft long, the split-plot was 30 ft wide and 120 ft long, and the split-split plot was 15 ft wide and 120 ft long.
Winter crops were planted approximately October 1. Winter cover and forage crops were chemically terminated or forage-harvested approximately May 15. Spring crops were planted from the end of February through the middle of March. Spring cover and forage crops were chemically terminated or forage-harvested approximately June 1. Biomass yields for both cover crops and forage crops were determined from a 3-ft × 120-ft area cut 3 in. high using a small plot Carter forage harvester from within the split-split-plot managed for forage. Winter and spring grain peas and winter wheat were harvested with a small plot Wintersteiger combine from a 6.5-ft × 120-ft area at grain maturity, which occurred approximately the first week of July.
Volumetric soil moisture content was measured at cover crop and winter wheat planting and termination using a Giddings Soil Probe in 1-ft increments to a 6-ft soil depth. In addition, volumetric soil content was measured in the 0-3-in. soil depth at wheat planting to quantify moisture in the seed planting depth. Grain yield was adjusted to 13.5% moisture content, and test weight was measured using a grain analysis computer. Grain samples were analyzed for nitrogen content.

Winter Wheat Yield
In 2008, hail damaged the wheat crop 1 week before harvest; therefore, no statistical separation was made between treatments. Winter wheat yield following a fallow crop ranged from 21 through 26 bu/a, wheat yield following wheat was 13 bu/a, and wheat yield following fallow was 22 bu/a ( Figure 1).
In 2009, grain pea and winter clover/triticale yielded 7 and 9 bu/a less than fallow (83 bu/a), and spring pea yielded 7 bu/a more than fallow ( Figure 2). Continuous wheat yielded least of all (57 bu/a). All other treatments yielded similar to fallow.
In 2010, winter pea/triticale and winter triticale yielded 5 and 7 bu/a less than fallow (70 bu/a), and spring lentil/triticale and spring pea/triticale yielded 4 and 6 bu/a less than fallow (Figure 3). Continuous wheat yielded least of all (43 bu/a). All other treatments yielded similar to fallow. Wheat following cover crops yielded an average of 2.9 bu/a more than wheat following a hay crop.
In 2011, only 6.77 in. of precipitation occurred between October 1, 2010, and July 1, 2011. This drought resulted in low wheat yields and a greater impact of the preceding crop on wheat yield. Wheat grown following a winter cover or forage crop yielded less than fallow with the exception of winter lentil (22 bu/a), which yielded similar to fallow (23 bu/a) ( Figure 4). Wheat yield following all other winter crops was reduced by 4 to 10 bu/a. Wheat yield following spring cover or forage crops was not affected as much as winter crops. Wheat yield following spring lentil, triticale, and lentil/triticale was similar to fallow, and wheat following spring pea and pea/triticale was reduced 7 and 3 bu/a, respectively. Wheat following spring grain pea was reduced 11 bu/a, and wheat following wheat was reduced 16 bu/a compared with fallow.
In 2012, only 6.01 in. of precipitation occurred between October 1, 2011, and July 1, 2012. The normal precipitation during this period was 12.5 in. The second year of drought conditions resulted in low wheat yields and the preceding crop reducing wheat yield more than in previous years. Winter cover or forage crops reduced wheat yield 24 bu/a, and spring cover or forage crops reduced wheat yield 23 bu/a compared with fallow ( Figure 5). Continuous wheat yielded 20 bu/a less than wheat-fallow. Wheat grown following grain peas yielded the least with yields being reduced to 3 bu/a following winter grain pea and 5 bu/a following spring grain pea.
Averaged over years from 2009 through 2012 (2008 was excluded due to hail damage), there was no difference whether the previous crop was grown as forage or cover (P = 0.09). Wheat yields following a cover crop tended to yield more than a forage crop. This difference was due to slightly more soil moisture following a cover crop than a forage crop. With the exception of winter and spring lentil (53 bu/a) replacing fallow with a cover or grain crop reduced yield compared with fallow (56 bu/a) ( Figure 6). Winter crop treatments tended to reduce wheat yields more than spring crop treatments. Winter triticale and triticale/legume mixtures yielded 9 to 12 bu/a less than fallow. Winter legume monocultures yielded more than triticale/legume mixtures. Winter pea and hairy vetch yielded 6 and 4 bu/a less than fallow, respectively. Spring triticale, triticale/legume mixtures, and spring pea yielded between 6 and 8 bu/a less than fallow. Grain pea yielded 12 bu/a less than fallow, and continuous winter wheat yielded 23 bu/a less than fallow.

Cover vs. Annual Forage
Across years (2009)(2010)(2011)(2012), there was no difference in wheat yield whether the previous crop was left as cover or harvested for forage. This indicates the previous crop can be harvested for forage rather than left standing as a cover crop without negatively affecting wheat yield.

Conclusions
Fallow helps stabilize crops in dry years. Annual precipitation in this study ranged from 12.1 to 21.7 in. In the dry years (2011 and 2012), growing a crop during the fallow period reduced wheat yields, but in wet years (2008, 2009, and 2010), growing a crop during the fallow period had little impact on wheat yield. The length of the fallow period also affected yields of the following wheat crop. Growing a cover or hay crop until June 1 affected wheat less than if continuous wheat or grain peas were grown until grain harvest, which was approximately the first week of July.
After the first year, winter lentil was grown in place of yellow sweet clover because the growth of yellow sweet clover was too slow to fit this cropping system. Winter peas and hairy vetch often winter-killed when grown in monoculture, but when grown in combination with triticale, they survived the winter better. Winter lentil grown in monoculture or with triticale survived the winter well. Cover crops did not improve wheat yield. Winter and spring lentil had the least negative impact on wheat yield, and averaged across years yielded similar to fallow. Winter crop treatments tended to reduce yield more than spring crop treatments, which was due to more moisture available in the spring crop treatments at wheat planting.
Forages provided an economic return, whereas cover crops were an expense to grow.
The cropping system can be intensified by replacing part of the fallow period with annual forages or spring grain pea to increase profit and improve soil quality; however, in semiarid environments, wheat yields will be reduced slightly. This yield reduction was compensated for by the value of a forage or grain crop, but not cover crop. The negative impacts on wheat yields might be minimized with flex-fallow. Flex-fallow is the concept of only planting forage or grain pea when soil moisture levels are adequate and the precipitation outlook is favorable. Under drought conditions such as 2011 and 2012, using flex-fallow, a crop would have not been grown in place of fallow. Implementing flex-fallow may minimize the negative impacts of reduced fallow. Future research needs to evaluate replacing fallow with forage or spring grain pea in a wheat-summer cropfallow rotation. Wheat yield, bu/a, 13.5% moisture W h e a t L e n t i l P e a T r i t i c a l e P e a / t r i t i c a l e V e t c h H a i r y v e t c h / t r i t i c a l e P e a / t r i t i c a l e P e a ( g r a i n ) T r i t i c a l e   100  90  80  70  60  50  40  30  20  10  0 Wheat yield, bu/a, 13.5% moisture W h e a t L e n t i l P e a P e a / t r i t i c a l e L e n t i l / t r i t i c a l e H a i r y v e t c h P e a / t r i t i c a l e H a i r y v e t c h / t r i t i c a l e P e a ( g r a i n ) T r i t i c a l e F a l l o w P e a T r i t i c a l e H a i r y v e t c h L e n t i l / t r i t i c a l e P e a / t r i t i c a l e L e n t i l P e a H a i r y v e t c h / t r i t i c a l e L e n t i l / t r i t i c a l e P e a / t r i t i c a l e P e a ( g r a i n ) F a l l o w T r i t i c a l e L e n t i l Spring None Wheat yield, bu/a, 13.5% moisture W h e a t L e n t i l / t r i t i c a l e P e a ( g r a i n ) P e a / t r i t i c a l e P e a L e n t i l T r i t i c a l e H a i r y v e t c h / t r i t i c a l e L e n t i l / t r i t i c a l e P e a H a i r y v e t c h F a l l o w T r i t i c a l e L e n t i l Spring None Figure 4. 2011 winter wheat yield following 2010 cover crops.
Letters within a column represent differences at LSD 0.05. Wheat yield, bu/a, 13.5% moisture P e a ( g r a i n ) P e a L e n t i l P e a / t r i t i c a l e P e a ( g r a i n ) Cover Crop, Annual Forages, and Grain Pea Effects on Soil Water in Wheat-Fallow and Wheat-Sorghum-Fallow Cropping Systems Introduction Interest in replacing fallow with a cash crop or cover crop has necessitated research on soil water and wheat yields following a shortened fallow period. Fallow stores moisture, which helps stabilize crop yields and reduce the risk of crop failure; however, only 25 to 30% of the precipitation received during the fallow period of a no-till wheat-fallow rotation is stored. The remaining 75 to 70% precipitation is lost, primarily to evaporation. Moisture storage in fallow is more efficient earlier in the fallow period, when the soil is dry, and during the winter months when the evaporation rate is lower. It may be possible to increase cropping intensity without reducing winter wheat yield. This study evaluated replacing part of the fallow period with a cover, annual forage, or short-season grain crop on plant-available water at wheat planting and winter wheat yield.

Wheat-Fallow
See "Fallow Replacement Crops (Cover Crops, Annual Forages, and Grain Pea) Impact on Wheat Yield" (page 5) for treatments (Table 1) and study methods.

Wheat-Sorghum-Fallow
Beginning in 2011, the wheat-fallow (WF) crop rotation was modified to a wheatsorghum-fallow (WSF) crop rotation. Fallow replacement crops (cover, forage, and grain) were grown during the spring of the fallow year. The study design was a split-split-plot randomized complete block design with 4 replications; crop phase (wheatsorghum-fallow) was the main plot, fallow replacement was the split-plot, and fallow replacement method (forage, grain, or cover) was the split-split-plot. The main plot was 450 ft wide and 120 ft long, the split-plot was 30 ft wide and 120 ft long, and the split-split plot was 15 ft wide and 120 ft long. Spring cover crop and forage crop treatments included forage pea (Pisum sativum L. ssp.), triticale (×Triticosecale Wittm.), oat (Avena sativa L.), a mixture of forage pea plus triticale, a mixture of forage pea plus oat, and a cocktail mixture of oat, triticale, pea, buckwheat var. Mancan (Fagopyrum esculentum M.), purple top turnip (Brassica campestris L.), and forage radish (Raphanus sativus L.). In addition, spring grain pea (Pisum sativum L. ssp.) and safflower (Carthamus tinctorius L.) were grown for grain. Spring cover crop treatments were grown in 2011, and winter wheat was planted in the fall of 2012. First-year plant-available soil water results at wheat planting in 2012 are reported. Because only one year of data for the WSF rotation is available, caution must be used in drawing conclusions.

Results and Discussion
Wheat -Fallow (2007-Fallow ( -2012 Year. Fallow and growing-season precipitation varied greatly during the course of this study. Average precipitation during the fallow period (July-December plus January-September) was 25.97 in., and growing season precipitation (October-June) was 12.51 in. Cover vs. Annual Forage. Plant-available soil water in the 0-3-in. soil depth averaged 0.03 in. greater among cover crop treatments (0.09 in.) than hay treatments (0.06 in.) (Table 3). In the 0-6-ft profile, plant-available soil water averaged 0.8 in. more following cover crops (5.76 in.) than hay crops (4.96 in.). More surface residue in the cover crop treatments compared with hay treatments likely reduced evaporation near the soil surface and might have reduced water runoff.
Fallow Crop (0-3-in. soil depth). Soil moisture in the top 0-3 in. is important for seed germination and seedling establishment. Plant-available soil water varied among treatments. Those treatments with winter triticale (hairy vetch/winter triticale, winter pea/winter triticale, winter lentil/winter triticale, and winter triticale) had the most soil moisture (Table 4). Legume monocultures, mixtures with spring triticale, spring triticale, and fallow had the second highest amount of soil moisture. There was a tendency for more soil moisture with increased amounts of biomass (Figure 1), and winter triticale produced the most amount of biomass. Increased levels of biomass likely reduced soil water evaporation. Thus, those treatments with winter triticale had more soil moisture than lower biomass treatments. Continuous winter wheat and grain pea had the least amount of surface soil moisture. Continuous winter wheat and grain pea also had the least amount of soil moisture at deeper depths, which likely kept soil near the surface dry.
Fallow Crop (0-6-ft soil depth). Moisture in the 0-6-ft soil profile is important for growing a crop, particularly in semiarid climates. Fallow had the greatest amount of soil moisture, and all other treatments had less (Table 5). Those treatments that produced less biomass (hairy vetch, spring pea, winter lentil, spring lentil, spring triticale, and winter pea) had more available soil moisture than the other treatments. Also, winter triticale and winter triticale mixtures had less soil moisture than spring triticale and spring triticale mixtures. Soil moisture was affected by both the amount of biomass and length of time the cover crop was grown. More soil water was used to grow cover crops that produced large amounts of biomass and had a long growing season. Grain pea and continuous wheat had the least amount of soil moisture, which was due to their longer growing season and shorter fallow period.

Wheat-Sorghum-Fallow (2012)
Cover vs. Annual Forage. Plant-available soil water in the 0-3-in. soil depth was 0.09 in. greater among cover crop treatments (0.17 in.) than hay treatments (0.08 in.) at wheat planting in 2012. There was no difference in available soil water between cover and hay treatments in the 0-6-ft profile. More surface residue in the cover crop treatments compared with hay treatments likely reduced evaporation near the soil surface and might have reduced water runoff.
Fallow Crop (0-6-ft soil depth). These results are similar to the findings from the 5-year WF rotation study. Fallow had 6.38 in. of plant-available soil water in the 0-6-ft profile at wheat planting, which was greater than all other treatments (Table 6). Of the fallow replacement crops, grain pea (3.26 in.) and forage pea (3.04 in.) had more plant-available soil water than safflower (1.11 in.). All other fallow replacement treatments had plant-available soil water similar to pea or safflower. Of all the cover or hay treatments, the cocktail had the least amount of stored soil water. The combination of species in the cocktail had different rooting architecture and maturities, which likely helped to increase soil water use more than a single-or two-species crop. Compared with previous years in the WF study, grain pea had more soil moisture at wheat planting than expected. The drought and heat in 2012 resulted in low grain pea yield (12.4 bu/a) and an early harvest. The early harvest resulted in a longer fallow period and more time for moisture storage than normal. Safflower matures later than grain pea and had the shortest fallow period of any treatment. The short fallow period resulted in less soil moisture storage ahead of wheat planting.

Conclusions
Fallow is important for storing precipitation and stabilizing crop yields, particularly in semiarid climates such as the central Great Plains. Growing a cover, hay, or grain crop in place of fallow reduced the amount of stored soil moisture at wheat planting. On average, cover crops stored 0.08 in. more moisture than hay crops, but this soil moisture difference did affect wheat yield. Soil moisture following grain crops was less than cover or hay crops, and this difference resulted in reduced wheat yield. Increasing surface residue tended to increase the amount of soil moisture in soil surface (0-3 in.), which could help improve stand establishment in dry years. Stored soil moisture was lowest among winter crops that produced a lot of biomass or a cover crop cocktail (six-species mixture). Spring crops and low-biomass crops had the least negative effect on stored soil moisture. Crops grown in place of fallow must compensate for the expense of growing the crop plus the reduction in soil moisture for the following crop.  Table 2. Plant-available soil water in the 0-3-in. and 0-6-ft soil depth at wheat planting, growing season precipitation, and fallow precipitation at Garden City, KS, 2007KS, -2012 Growing season  Table 3. Cover crop method (cover crop or hay harvest) effects on plant-available soil water in the 0-3-in. and 0-6-ft soil depth at wheat planting Cover crop method Plant-available water (0-3 in.) Plant-available water (0-6 ft)  Table 4. Fallow, cover crop, and grain crop effects on plant-available soil water in the 0-3-in. soil depth at wheat planting Fallow method Plant-available water (0-3 in.)  Table 5. Fallow, cover crop, and grain crop effects on plant-available soil water in the 0-6-ft soil depth profile and the difference in soil moisture compared with fallow at wheat planting

Fallow method
Plant-available water (0-6 ft)  Table 6. Fallow, cover crop, and grain crop effects on plant-available soil water in the 0-6-ft soil profile and the difference in soil moisture compared with fallow at wheat planting in a wheat-sorghum-fallow rotation in 2012 Fallow method Plant-available water (0-6 ft)

Summary
Due to the warm and dry conditions during the 2011 growing season, the dryland corn crop prematurely quit growing mid-season (VT stage) due to drought stress. Irrigated corn produced grain, with accumulation consistently increasing from early R3 through R6 with a final yield of 191.5 bu/a. Both grain and cob moisture content decreased throughout the season, ending up at 147.6 and 461.3 g/kg, respectively. This information can be used to estimate corn yield or help make determinations for when to harvest corn for silage.

Introduction
A field experiment was conducted at the Kansas State University Southwest Research-Extension Center at Garden City, KS, to compare the grain fill rates of a corn hybrid under irrigation and dryland (rainfed) cropping conditions. Understanding the rate of grain yield development and change in moisture content is important for making management decisions about when to plan and implement silage harvest and for determining grain yield potential. This experiment evaluated grain yield and moisture throughout the reproductive growth stages of a corn crop grown under both irrigated and dryland conditions.

Procedures
A field with center pivot irrigation was selected for the irrigated plot area, and the nonirrigated corner of the field was selected for the dryland plot area. Corn in both areas was grown following wheat. The soil type was a Ulysses Silt Loam.
On May 5, 2011, Pioneer 33B54 (113-day comparative relative maturity, or CRM) was planted in both the irrigated and dryland portions of the field at seeding rates of 34,300 and 18,000 seeds/a, respectively, on 30-in. row spacing. A preplant application of nitrogen (N) was applied at a rate of 200 lb/a N as urea in the irrigated field and 80 lb/a N as urea in the dryland field. An area consisting of 4 50-ft-long rows was marked in both the irrigated and dryland areas adjacent to each other to be used for sample collections.
On August 3, the irrigated corn was at the milk stage (R3) ( Table 1). Beginning at this time interval, 5 ears were hand-harvested on a weekly basis at random from the sample collection area through physiological maturity (R6) and grain harvest. Observations of husk greenness, crop canopy color, and intactness were recorded at each time interval (Table 2). On August 3, plants in the dryland plots were in the mid-tassel (VT) stage of growth and showing drought stress. At each time interval, 5 ears were collected at random, weighed wet, photographed, broken in half to check the progression of the starch line, and the starch line was recorded with a photograph. The ears were then placed in a drying oven and dried at 104ºF for 96 or more hours until dry. Dried ears were then shelled and a weight of the grain, cob, and 250 kernels were measured. When the corn reached the R5 stage, the ears were shelled before drying so a wet weight of the grain and cob could be measured separately; dry weights were measured after drying. These measurements were then used to obtain the change in moisture of the grain and cob.

Growing Conditions
The 2011 growing season was exceptionally warmer and dryer than normal. The amount of precipitation received from wheat harvest in 2010 to corn planting in 2011 was 6.64 in., which is 4.89 in. below average and resulted in planting into dry soils with very little profile moisture. During the 2011 corn growing season (May 1-Oct. 1), precipitation was 55% of the 30-year average (14.57 in.) and temperatures averaged 2.5º warmer than the 30-year average of 68.3 (Table 3). These conditions led to a failed crop in the dryland field and reduced yield in the irrigated field even with supplemental irrigation.

Results
The warm, dry weather conditions from the previous wheat harvest through the corn growing season resulted in conditions that kept the corn crop stressed throughout the growing season. These conditions caused the dryland corn crop to prematurely quit growing at tassel (VT) and not produce any ears. The stressful environmental conditions also reduced the yield potential of the irrigated corn.
Grain yield development was linear from early milk (R3) on August 3 until physiological maturity (R6) on September 21. The last sampling period showed a slight decrease in yield, which was likely due to the random chance of collecting shorter ears at the last sampling period than in earlier sampling periods (based on photographs). Yields started at 31.4 bu/a during the first sample collection and increased to 191.5 bu/a at maturity, with an average daily grain accumulation of 2.9 bu/a per day ( Figure 1). Grain and cob moisture showed a linear trend of decreasing moisture content from early sampling until maturity ( Figure 2). Grain moisture decreased from 431 g/kg on August 24 to 148 g/kg on September 28, a decrease of 8 g/kg per day. Cob moisture decreased from 653 g/kg to 461 g/kg, a decrease of 5 g/kg per day. Blister: kernels are white and resemble a blister in shape R3 Milk: kernels are yellow on the outside with a milky inner fluid R4 Dough: milky inner fluid thickens to pasty consistency R5 Dent: nearly all kernels are denting R6 Physiological maturity: black abscission layer has formed   Summary 2012 was the second growing season of extreme heat and drought conditions in Southwest Kansas. Despite the poor conditions, a corn crop was grown under both irrigated and dryland conditions. The previous year, dryland corn died due to heat and drought stress prior to producing any ears. The stressful environmental conditions in 2012 reduced grain yield potential, particularly in dryland. Dryland yields reached a yield potential of 93.4 bu/a early in physiological maturity (R5-R6), but by grain harvest yield was 50 bu/a. Irrigated corn reached a yield potential of 135 bu/a early in physiological maturity and maintained this yield level until harvest. The moisture content of grain and cob showed similar declines for both the dryland and irrigated corn. From August 1 to September 13, dryland grain moisture decreased from 558.8 to 27.6 g/kg, a decrease of 15.5 g/kg per day, and irrigated grain moisture decreased from 581.3 to 53.4 g/kg, a decrease of 13.6 g/kg per day. During this same time period, dryland cob moisture decreased from 685.5 to 55.0 g/kg, a decrease of 21.3 g/kg per day, and irrigated cob moisture decreased from 695.5 to 63.9 g/kg, a decrease of 15.7 g/kg per day. This information can be used to estimate corn yield or help make determinations about when to harvest corn for silage.

Introduction
A field experiment was conducted at the Kansas State University Southwest Research-Extension Center at Garden City, KS, to compare the grain fill rates of a corn hybrid under irrigated and dryland cropping conditions. Understanding rate of grain yield development and change in moisture content is important for making management decisions about when to plan and implement silage harvest and for determining grain yield potential. This experiment evaluated grain yield and moisture content throughout the reproductive growth stages of a corn crop grown under both irrigated and dryland conditions.

Materials and Methods
A field with center-pivot irrigation was selected for the irrigated plot area, and the nonirrigated corner of the field was selected for the dryland plot area. Corn in both areas was grown following wheat. The soil type was a Ulysses Silt Loam.
On April 27, 2012, Dekalb DKC52-59 (102-day comparative relative maturity, or CRM) was planted in both the irrigated and dryland portions of the field at seeding rates of 34,300 and 18,000 seeds/a, respectively, on 30-in. row spacing. A preplant application of nitrogen (N) was applied at a rate of 160 lb/a N as urea in the irrigated field and 40 lb/a N as urea in the dryland field. An area consisting of 4 50-ft-long rows was marked out in the irrigated and dryland areas adjacent to each other to be used for sample collections.
On July 18, the irrigated corn was at an early milk stage (R3) and the dryland corn was at the R2 Stage (Table 1). Beginning at this time interval, 5 ears were collected at random from the sampling areas on a weekly basis through physiological maturity (R6) and grain harvest. Observations of husk greenness, crop canopy color, and intactness were recorded at each time interval (Table 2). At each time interval, 5 ears were collected at random, weighed wet, photographed, broken in half to check the progression of the starch line, and the starch line was recorded with a photograph. The ears were then placed in a drying oven and dried at 104ºF for 96 or more hours until dry. Dried ears were then shelled and a weight of the grain, cob, and 250 kernels were measured. When the corn reached the R5 stage, the ears were shelled before drying so a wet weight of the grain and cob could be measured separately; dry weights were measured after drying. These measurements were then used to obtain the change in moisture of the grain and cob.

Growing Conditions
Even though the drought from 2011 continued through the 2012 growing season, corn yields were higher in 2012 than 2011, in part due to some precipitation that occurred during the spring of 2012. From the preceding wheat crop harvest until corn planting (July 2011-April 2012) precipitation was 10.5 in., which was near the normal amount of 13.1 in., allowing an accumulation of moisture in the soil profile. This allowed the corn to be planted into good field conditions. After planting, the weather turned drier and warmer than average during the growing season, with precipitation at 54% of the 30-year average (14.57 in.), and temperature averaged 3.3º warmer than the 30-year average (68.3ºF) ( Table 3). These conditions resulted in corn developing fairly normally until August 16, but after that date both the dryland and irrigated corn began showing signs of stress and decreased yield potential.

Results
Grain development for both dryland and irrigated corn followed a linear pattern for grain accumulation from early milk stage (R3) through mid to late dent (R5); after this stage, grain yield potential leveled in irrigated and decreased in dryland. Early in the season, from July 18 through August 16, dryland corn accumulated an average of 2.9 bu/a per day up to a yield potential of 93.4 bu/a at R5. After this point, yield potential decreased to around 50 bu/a at harvest. Irrigated corn accumulated an average of 4.2 bu/a per day from early milk stage (R3) through mid to late dent (R5), reaching a yield potential of 135 bu/a ( Figure 1). After R5, the yield potential of irrigated corn leveled off, unlike dryland corn which decreased until harvest. Yield potential was decreased after R5 due to heat and moisture stress.
Grain and cob moisture showed a linear trend of decreasing moisture content from early sampling until maturity for both the dryland and irrigated corn ( Figure 2). From August 1 through September 13, dryland grain moisture decreased from 558.8 to 27.6 g/kg, a decrease of 15.5 g/kg per day, and irrigated grain moisture decreased from 581.3 to 53.4 g/kg, a decrease of 13.6 g/kg per day. During this same time period, dryland cob moisture decreased from 685.5 to 55.0 g/kg, a decrease of 21.3 g/kg per day, and irrigated cob moisture decreased from 695.5 to 63.9 g/kg, a decrease of 15.7 g/kg per day.    Management practices were identified that improved establishment, winter survival, and grain yield (Holman et al., 2011), but information is still needed on how to best grow winter canola in the region.
Canola varieties Griffin and Wichita were grown with and without a companion crop (spring triticale, winter triticale, Daikon radish, and Shogoin turnip) and were managed with and without fall simulated grazing (hay). Treatment effects (variety, companion crop, and fall grazing) on winter canola fall plant density, fall vigor, winter survival, spring plant density, spring vigor, grain yield, forage yield, forage quality, and grain oil content were quantified.
Grazing or haying canola in the fall reduced grain yield 30-50% and decreased the yield of a more upright growth variety (Wichita) more than a prostrate growth variety (Griffin). Companion cropping decreased canola fall stand, winter survival, spring stand, and grain yield. Companion crops can improve fall forage production. The results from this study indicate canola grown for grain should not be grown with a companion crop or in a dual-purpose system.

Introduction
Growing a companion crop or grazing canola in the fall might affect winter survival and grain yield of canola, but it might also provide more options and economic incentive to growing the crop if winter survival or forage production are increased. This study evaluated the effects of companion cropping and fall grazing on winter canola survival, forage yield, and grain yield.
The southern Great Plains has sufficient growing degree days to produce 120 to 150 days of grazable wheat pasture that can be either grazed out in the spring or harvested for grain after grazing in a dual-purpose system. Producing winter wheat in a dualpurpose system is a unique and economically important resource. Winter wheat provides economical, high-quality forage at a time of the year when few other quality forage sources are available. It is estimated that 3.2 million ha (7.9 million acres) of winter wheat in the southern Great Plains are grazed annually in a dual-purpose system (Carver et al., 2001). Winter wheat that is harvested for grain can be grazed in the late fall and early spring without reducing grain production as long as cattle are removed before wheat development reaches first hollow stem, soil moisture is adequate, and recommended growing practices are implemented (Khalil et al., 2002;Redmon et al., 1996;Virgona et al., 2006). Grazing occasionally increased yield of tall winter wheat varieties by reducing plant height, which resulted in less plant lodging (Redmon et al., 1995). Insufficient information is available on the effects of grazing canola, yet producers need this information. Previous research found companion-cropping winter annual legumes with winter triticale increased survival of the winter legume. Growing a companion crop with winter canola might affect its winter survival and forage yield.

Procedures
Field studies were conducted at the Kansas State University Southwest Research-Extension Center in Garden City, KS (37°59'7"N, 100°48'52"W, elevation 2,862 ft). Average annual precipitation was 19.3 in. Soil type was a Ulysses silt loam soil (fine-silty, mixed, superactive, mesic Aridic Haplustolls) with pH 7.8 and 1.8% organic matter in the top 6 in. of soil.
The experimental design was a randomized split-plot with four replications. Main plot treatment was canola variety (Griffin or Wichita) and companion crop treatment (none, spring triticale, winter triticale, radish, and turnip), and split-plot treatment was managed with or without simulated fall grazing (haying Irrigation was applied with an overhead sprinkler throughout the growing season using an irrigation scheduling program with irrigation applied at 50% available soil water (Clark et al., 2002), with 12.68 in. applied in 2010-2011 and 14.58 in. applied in 2011-2012 (Figure 1). Fertilizer was applied based on soil test recommendations.
Within each plot, four permanently marked 3-ft rows were used for fall and spring plant density to determine winter survival. Fall plant density and vigor were quantified in mid-November, and spring plant density and vigor were quantified in early April. Plant vigor was visually determined using a scale of 1 to 10 (0 = dead and 10 = robust plant). Canola was harvested July 7, 2011, and June 19, 2012, from a 6.5-ft-wide by 30-ft-long area using a plot combine (Delta, Wintersteiger Inc., Salt Lake City, UT). A seed subsample was collected at harvest, and moisture content was measured with a grain analysis computer (GAC 2100, Dickey John, Auburn, IL). Data were analyzed with PROC MIXED, residual maximum likelihood method, in SAS (SAS Institute Inc., Cary, NC). Replication and replication × year were considered random effects, and all other effects including year were considered fixed in the model. Treatment effects were considered significant at P ≤ 0.05, and least squares means were separated by independent pairwise t-tests at a significance level of P ≤ 0.05 (PDIFF option).

Growing Season
The 30-year average cumulative precipitation from September 1 through July 1 (typical growing season) was 13.95 in., and the average total annual precipitation was 19.19 in.  (Table 1). Grain yield was greater in 2011 than 2012, and test weight and 1,000seed weight were greater in 2012 than 2011. Grain yield was likely greater in 2011 than 2012 due to a longer growing season in 2011. In 2012, temperatures increased early in the spring and canola was harvested about 3 weeks earlier than normal (canola was harvested July 7, 2011, and June 19, 2012). Temperature during grain fill was lower in 2012 than 2011, which created more favorable conditions for grain fill, resulting in greater test weight and seed weight in 2012.

Variety
Griffin grows more prostrate than Wichita, but both varieties are well adapted to being grown in Kansas. Griffin and Wichita had similar fall and spring stand densities, plant vigor, winter survival, test weight, and forage yield. Averaged across 2011 and 2012, Griffin yielded 162 lb/a more grain than Wichita (Table 2).

Simulated Grazing (Haying)
Haying reduced the yield of both varieties (Table 3), but the yield of Wichita was reduced more than Griffin. Haying reduced the yield of Griffin 34% and Wichita 48% (Table 2). Griffin's prostrate growth likely protected the plant more from the damage of haying than the more upright growth of Wichita. The apical meristem of canola is elevated above the ground, whereas in wheat it remains in the crown until it begins to elongate at first hollow stem. This difference in growth allows the growing point in wheat to be protected from fall grazing but makes canola susceptible to injury. Haying canola reduced fall stand density, winter survival, spring stand density, and grain yield (Table 3).

Companion Crop
Companion cropping reduced canola yield in 2011, so companion crops were planted in alternate rows with canola in 2012 to attempt reducing the negative impact of companion cropping on grain yield; however, both planting methods (planted within row or alternate row) reduced yield equally (Table 4). Spring triticale had the least negative effect on yield, and turnip had the most negative impact on yield. Spring triticale was terminated early in the fall with freezing temperatures plus herbicide applications. Some turnip and radish overwintered in 2012 due to the mild winter conditions and competed with canola. Turnip and radish reduced canola fall stand, winter survival, spring stand, and test weight (Table 4). Companion crops increased fall forage yield and varied by canola variety (Tables 2 and 4). Radish and turnip planted with Griffin produced more forage yield than radish or turnip planted with Wichita, and spring triticale and winter triticale planted with Griffin or Wichita produced similar forage yield ( Table 2). The prostrate growth of Griffin might have allowed more growth of turnip and radish, resulting in greater forage yield.

Conclusions
This study found that grazing or haying canola in the fall would reduce grain yield at least 30% with currently grown varieties. Varieties with prostrate growth were affected less by grazing than varieties with more upright growth, yet grain yield of a prostrate growth variety was still reduced. At this time, growing canola in a dual-purpose system is not recommended unless a 30-50% decrease in crop yield is acceptable. If growing canola in a dual-purpose system, producers should select a variety with the most prostrate growth available. Companion cropping did not increase winter survival as it had with winter annual legumes and tended to decrease canola fall stand, winter survival, spring stand, and grain yield. Companion crops can improve fall forage production. Spring triticale had the least negative impact on grain yield, yet had some positive impact on fall forage production. Turnip and radish had the most negative impact on grain yield, but also increased fall forage production the most. Companion crops should not be grown with canola if the primary intent is to harvest canola for grain. The results of this study indicate canola grown for grain should not be grown with a companion crop or in a dual-purpose system.

A. Schlegel
Summary A large-scale rainfed cropping systems research and demonstration project evaluated two summer crops (corn and grain sorghum) along with winter wheat in crop rotations varying in length from 1 to 4 years. The crop rotations were continuous grain sorghum, wheat-fallow, wheat-corn-fallow, wheat-sorghum-fallow, wheat-corn-sorghum-fallow, and wheat-sorghum-corn-fallow. The objective of the study is to identify cropping systems that enhance and stabilize production in rainfed cropping systems to optimize economic crop production. Lack of precipitation during 2012 depressed grain yields of all crops. Averaged across the past five years, wheat yields tended to be less in four-year rotations than in two-and three-year rotations. Corn and grain sorghum yields (fiveyear average) were about twice as great when following wheat than when following corn or grain sorghum.

Introduction
The purpose of this project is to research and demonstrate several multicrop rotations that are feasible for the region along with several alternative systems that are more intensive than two-or three-year rotations. The objectives are to (1) enhance and stabilize production of rainfed cropping systems through the use of multiple crops and rotations using best management practices to optimize capture and utilization of precipitation for economic crop production, and (2) enhance adoption of alternative rainfed cropping systems that provide optimal profitability.

Procedures
The crop rotations are two-year (wheat-fallow [WF]), three-year (wheat-grain sorghumfallow [WSF] and wheat-corn-fallow [WCF]), and four-year rotations (wheat-cornsorghum-fallow [WCSF] and wheat-sorghum-corn-fallow [WSCF]) and continuous sorghum (SS). All rotations are grown using no-till practices except for WF, which is grown using reduced-tillage. All phases of each rotation are present each year. Plot size is a minimum of 100 × 450 ft. In most instances, grain yields were determined by harvesting the center 60 ft (by entire length) of each plot with a commercial combine and determining grain weight in a weigh-wagon or combine yield monitor.

Results and Discussion
Grain yields of all crops were below average in 2012 because of lack of precipitation (Table 1). Total precipitation for 2012 was 7.49 in., setting a new record for the driest year on record. Wheat yields were less than 15 bu/a and were not affected by crop rotation. Corn yields were less than 10 bu/a for all rotations. Grain sorghum yields were greater following wheat (33-39 bu/a) than following corn or sorghum (less than 10 bu/a).
Wheat yields averaged across the past five years (2008)(2009)(2010)(2011)(2012) tended to be slightly greater in two-and three-year rotations than in four-year rotations (Table 2). Corn yields following wheat averaged about twice as much than following sorghum. Similarly, sorghum yields following wheat were about twice as much than following corn or sorghum.

Acknowledgements
This research project received support from the Ogallala Aquifer Initiative.  Effects of Wheat Stubble Height on Subsequent

Introduction
Seeding of summer row crops throughout the west-central Great Plains often occurs following wheat in a 3-year rotation (wheat-summer crop-fallow). Wheat residue provides numerous benefits including evaporation suppression, delayed weed growth, improved capture of winter snowfall, and soil erosion reductions. Stubble height affects wind velocity profile, surface radiation interception, and surface temperatures, all of which affect evaporation suppression and winter snow catch. Taller wheat stubble is also beneficial to pheasants in postharvest and overwinter fallow periods. Use of stripper headers increases harvest capacity and provides taller wheat stubble than previously attainable with conventional small grains platforms. Increasing wheat cutting heights or using a stripper header should further improve the effectiveness of standing wheat stubble. The purpose of this study is to evaluate the effect of wheat stubble height on subsequent summer row crop yields.

Procedures
This study was conducted at the Southwest Research-Extension Center dryland station near Tribune, KS. From 2007 through 2012, corn and grain sorghum were planted into standing wheat stubble of three heights. Optimal (high) cutterbar height is the height necessary to maximize both grain harvested and standing stubble remaining (typically around two-thirds of total plant height), the short cut treatment was half of optimal cutterbar height, and the third treatment was stubble remaining after stripper header harvest. In 2012, these heights were 7, 14, and 21 in. Average stubble heights from 2007-2012 were 9, 18, and 27 in. In 2012, corn and grain sorghum were seeded at rates of 15,000 seeds/a and 50,000 seeds/a, respectively. Nitrogen was applied to all plots at a rate of 100 lb/a. Starter fertilizer (10-34-0 N-P-K) was applied in-row at a rate of 7 gal/a. Plots were 40 × 60 ft with treatments arranged in a randomized complete block design with six replications. Two rows from the center of each plot were harvested with a plot combine for yield and yield component analysis. Soil water measurements were obtained with neutron attenuation to a depth of 6 ft in1-ft increments at seeding and harvest to determine water use and water use efficiency.

Results and Discussion
The 2012 growing season had above-normal temperatures and below-normal precipitation, which negatively affected grain yield. Corn grain yields were about 50 bu/a lower than the average yields from 2007-2012 (Tables 1 and 2). Stubble height did not affect grain yield or any of the other measured parameters in 2012; however, average corn yields from 2007-2012 were 11 bu/a greater when planted into high-or strip-cut stubble. This was primarily due to greater number of kernels per ear. Residue production and water use efficiency was also greater with the taller stubble.
Grain sorghum yields were similar to corn yields in 2012 and were not affected by stubble height (Table 3). When averaged across years from 2007-2012, the highest yields were obtained in the high-cut stubble but were not significantly greater than the other stubble heights. None of the other measured parameters for grain sorghum were affected by stubble height (Table 4).

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 is 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 levels remained high, so the K treatment was discontinued in 1992 and replaced with a higher P rate.

Procedures
This field study is conducted at the Tribune Unit of the Southwest Research-Extension Center. Fertilizer treatments initiated in 1961 are N rates of 0, 40, 80, 120, 160, and 200 lb/a 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. The treatments were changed in 1992; the K variable was 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 soil is a Ulysses silt loam. The corn hybrids [DeKalb C60-12 (2003), Pioneer 34N45 (2004and 2005, Pioneer 34N50 (2006)

Results
Corn yields in 2012 were much greater than the 10-year average (Table 1). Nitrogen alone increased yields 84 bu/a, whereas P alone increased yields less than 10 bu/a; however, N and P applied together increased corn yields up to 174 bu/a. Maximum yield was obtained with 200 lb/a N with 80 lb/a P 2 O 5 . Reducing N or P rates reduced yields by at least 8%, which is greater than the 10-year average of 4%. Corn yields in 2012 (averaged across all N rates) were 8 bu/a greater with 80 than with 40 lb/a P 2 O 5 , which is slightly greater than the 10-year average of 5 bu/a.  O 5  2003  2004  2005  2006  2007  2008  2009  2010  2011  2012  Mean  ----------

A. Schlegel
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 2012, N applied alone increased yields almost 70 bu/a, whereas N and P applied together increased yields up to 100 bu/a. Averaged across the past 10 years, N and P fertilization increased sorghum yields more than 65 bu/a. Application of 40 lb/a N (with P) was sufficient to produce about 80% of maximum yield in 2012, which was slightly less than the 10-year average. Application of potassium (K) has 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 is 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
This field study is conducted at the Tribune Unit of the Southwest Research-Extension Center. Fertilizer treatments initiated in 1961 are 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 are broadcast by hand in the spring and incorporated before planting. The soil is a Ulysses silt loam. Sorghum (Pioneer 8500/8505 from 2003-2007, Pioneer 85G46 in 2008-2011, and Pioneer 84G62 in 2012 was planted in late May or early June. Irrigation is used to minimize water stress. Sprinkler irrigation has been used since 2001. The center two rows of each plot are machine-harvested after physiological maturity. Grain yields are adjusted to 12.5% moisture.

Results
Grain sorghum yields in 2012 were 24% greater than the 10-year average yields (Table  1). Nitrogen alone increased yields 69 bu/a, whereas P alone increased yields 12 bu/a; however, N and P applied together increased yields up to 100 bu/a. Averaged across the past 10 years, N and P applied together increased yields more than 65 bu/a. In 2012, 40 lb/a N (with P) produced about 79% of maximum yields, which is slightly less than the 10-year average of 86%. Sorghum yields were not affected by K fertilization, which has been the case throughout the study period.

Introduction
The growing resistance of kochia to glyphosate has led many producers to consider returning to tillage options for weed control in Western Kansas dryland crop rotations. Regardless of the path chosen, profitability will be decreased compared with the period prior to the advent of weed resistance. Long-term data from the Kansas State University Research Center in Tribune, KS, has indicated a significant economic advantage to incorporating no-till practices in a wheat-sorghum-fallow (WSF) rotation. With the growing difficulty of controlling kochia with a glyphosate-oriented herbicide program, the natural question becomes how much can be spent on herbicides for kochia control to maintain the economic advantage of no-till. Consequently, an example herbicide budget for kochia control was developed with the assistance of weed scientists at Kansas State University to compare the relative profitability of tillage systems in a WSF rotation to that of an herbicide program that used glyphosate as the primary herbicide option. The results indicate that although herbicide costs nearly double for the kochia control program, returns for the no-till rotation were nearly $50/a greater than reduced-till and $55/a greater than conventional-till; however, the profitability of the no-till rotation decreased by $30/a compared with cropping systems without glyphosate resistance.

Long-Term Tillage Intensity Study
A long-term tillage intensity study was established at the Kansas State University Research Center in Tribune, KS, in 1991 (see "Benefits of Long-Term No-Till in a Wheat-Sorghum-Fallow Rotation," SRP 1070, Southwest Research-Extension Center Field Day 2012, p. 5-6). The study compared three weed control regimes in a wheatsorghum-fallow (WSF) rotation. The weed control options included conventional tillage, reduced tillage, and no-till. Conventional tillage typically required 4 to 5 tillage operations per year to control weeds prior to planting. Reduced-till used a combination of herbicides (1 to 2 spray operations) and tillage (2 to 3 operations) to control weeds prior to planting. No-till exclusively used herbicides for weed control. In 2001, the reduced-till component of the study was modified. Instead of including tillage operations prior to both wheat and sorghum, wheat was planted using conventional-till, whereas sorghum incorporated no-till. Thus, the rotation became a reduced-till rotation by including conventional-till and no-till components. Table 1 shows the annual yields of the tillage intensity study for wheat and sorghum. From 2001-2011, no-till wheat and sorghum yields were approximately 8 bu/a and 43 bu/a higher, respectively, than with conventional-till. Similarly, no-till wheat and sorghum yields were 5 bu/a and 30 bu/a higher, respectively, than in a reduced-till rotation (conventional-till prior to wheat and no-till prior to sorghum). Average production costs for the three tillage scenarios are shown in Table 2. Without including harvest costs, reduced-till costs are approximately $26/a higher than conventional-till, whereas no-till costs are about $21 higher than reduced-till. Using market year average prices for 2011 of $7.02 for wheat and $5.99 for sorghum, the higher yields associated with no-till resulted in a $63/a advantage for no-till over reduced-till and an $83/a advantage for no-till over conventional-till ( Figure 1).

Glyphosate-Resistant Kochia
Controlling kochia in no-till systems with glyphosate-oriented treatments has become problematic for many farmers in western Kansas; consequently, no-till crop producers have been considering alternative herbicide strategies or even using tillage as means to control kochia. Tables 3 and 4 show typical glyphosate-based herbicide treatments for no-till wheat and sorghum, respectively. Tables 5 and 6 show alternative herbicide treatments for wheat and sorghum to manage glyphosate-resistant kochia. As seen in the tables, herbicide expenses increase from $44/a to $82/a for wheat, whereas sorghum expenses increase from $56/a to $105/a. The question facing producers dealing with glyphosate-resistant kochia is whether the higher yields associated with no-till will outweigh the higher kochia-related herbicide costs. Figure 1 indicates that although the higher kochia-related herbicide costs decrease the profitability of the WSF rotation by nearly $30/a, the no-till rotation is still more profitable by nearly $50/a vs. the reducedtill rotation, and $55/a more than the conventional-till rotation.      Monocot control at 96 DAP was between 85 and 95%. The highest control was found in treatments 7 and 8. Due to extreme heat and drought, weed pressure was very low, and corn yields in the control plots were not different from the herbicide-treated plots. This makes comparisons of these weed control products difficult, but it clearly demonstrates that even at high rates, these herbicides have very little potential to injure corn. In 2010, in response to an emerging threat of glyphosate-resistant kochia, a regional task force tested 9 preemergence and 14 postemergence non-glyphosate herbicide tank mixes for kochia control at six to nine locations (Stahlman et al., 2012). None of these tank mixes consistently provided 100% control of kochia, but preemergent applications of dicamba provided the best and most consistent preemergence control. It was unclear, however, what rate would provide the optimal level and duration of control. Among the postemergence applications, Paraquat and Atrazine tank mixes provided the highest and most consistent level of control. Therefore, the objective of this study was to measure the dose response relationship of several preemergence dicamba rates followed by postemergence tank mixes of Paraquat and Atrazine.

Procedures
Within the first week of March, a split-plot experiment with 0, 0.25, 0.5, 0.75, and 1 lb/a of dicamba as the main plot was established. During May, the main plot treatments began to fail. Subplots of Paraquat and Atrazine at 0.75 and 1 lb/a within the main plot were then applied. To reduce the possible interference of grassy weeds, 2 lb/a of S-metolachlor was included. These treatments were repeated at Hays and Tribune, KS.
To expand the inference of this experiment to a wheat-fallow-wheat rotation at the Tribune location, an additional set of subplots were included in a tank mix of Paraquat + metribuzin at 0.75 and 0.5 lb/a.

Results
Control 30 DAT (days after treatment) ranged from 100% to 94% with 1 lb/a dicamba across all locations (Figures 1, 2, and 3). At this rate, control declined at 60 DAT from 94% to 83% across all locations. With 0.5 lb/a dicamba, control declined from 85% to 70% across all locations. At all but the Garden City location, a logistic model explained the dose response relationship with R-squares greater than 0.90 at all rating dates from 33 to 94 DAT. At the Garden City location, this was true until 47 DAT; however, from 68 to 110 DAT the rate of control at the Garden City location was best described by simple linear models with R-square values greater than 0.90 at all rating dates. At all rating dates, the rate of diminishing returns was seen at 0.5 lb/a dicamba. At this rate, control declined linearly with time at all three locations with R-squares ranging from 0.90 to 0.97 (Figures 4, 5, and 6). The slopes of these lines predicted from 0.56% to 0.86% decline in control per day during the first 60 days. At the Tribune and Hays locations, tank mixes with Paraquat and Atrazine or Metribuzin augmented control of dicamba-treated plots elevating control from 93% to 100% for greater than 88 DAT. Record heat and drought at the application at Garden City, coupled with beginning kochia populations of greater than 250 plants/in. 2 , made coverage of postemergence treatments poor and led to atypically poor control compared with previous work. There was substantial kochia mortality in the control plots due to drought, and remaining plants were stunted and failed to reach a height of 12 in. at the end of the growing season. This limits inference of the later season postemergence treatments at this location. All locations support the early March application of 0.5 lb/a of dicamba for early season preemergence control of kochia, but additional postemergence treatments are needed. At two of the three locations, preemergence dicamba treatments followed by postemergence applications of Paraquat and Atrazine or Metribuzin provided excellent season-long control.

Summary
No herbicide tank mix produced visual injury or depressed corn yield. Due to extreme heat and drought, weed pressure was very low. All herbicide treatments provided greater than 96% control of all weed species 68 days after treatment (DAT).

Introduction
With the advent of glyphosate-resistant weed species, herbicide tank mix partners with multiple modes of actions are needed to augment glyphosate's weed control. The objective of this study was to test such tank mixes.

Procedures
Broadleaf and grassy weed control was evaluated in irrigated corn at the Kansas State University Research-Extension Center in Garden City, KS. Corn was planted on May 9, 2012, with preemergence herbicides applied within 24 hours of planting. Preemergent application conditions of air temperature, soil temperature, wind speed, relative humidity, and soil moisture were 78ºF, 71ºF, 3 mph, 46%, and inadequate, respectively. Soil was Ulysses silt loam, and organic matter, soil pH, and cation exchange capacity (CEC) were 1.4%, 8, and 18.4, respectively. All herbicide treatments were applied with a tractor-mounted CO 2 -pressurized windshield sprayer calibrated to deliver 20 gal/a at 30 psi and 4.1 mph. Adjuvant and ammonium sulfate (AMS) were added per manufacturer recommendations. Postemergence herbicide applications were made on June 20, 2012. The conditions of air temperature, soil temperature, wind speed, relative humidity, and soil moisture were 91ºF, 86ºF, 11 mph, 34%, and adequate. The trial was established as a randomized complete block design with four replications, and plots were 10 × 30 feet. Crop injury and percentage weed control were visually rated.

Results
No crop injury was observed. Due to inconsistent distribution of weeds, percentage weed control was rated as overall grassy (monocot) and broadleaf (dicot) control (Table  1). Monocot species observed were Cenchrus longispinus (Hack.) Fernald, Digitaria sp. L., and Setaria veridis (L.) P. Beauv. Dicot species observed were Abutilon theophrasti Medik., Amaranthus palmeri S. Watson, Euphorbia maculata L., Kochia scoparia L. Schrad., Proboscidea louisianica (Mill.) Thell, Salsola kali L., Solanum rostratum Dunal, and Xanthium strumarium L. Due to extreme heat and drought, weed pressure was very low. All herbicide treatments provided greater than 96% control of all weed species 68 DAT. Although control of grassy weeds declined by 96 DAT to 88% in the poorest treatment, overall control remained excellent. The degree of broadleaf weed control seen at 68 DAT was maintained at or above 96%.

Procedures
Broadleaf and grassy weed controls were evaluated in irrigated corn at the Kansas State University Research-Extension Center in Garden City, KS. Corn was planted on May 15, 2012, with preemergence herbicides applied within 24 hours of planting. Preemergent application conditions of air temperature, soil temperature, wind speed, relative humidity, and soil moisture were 83ºF, 70ºF, 3 mph, 49%, and adequate, respectively. Soil was Ulysses silt loam, and organic matter, soil pH, and cation exchange capacity (CEC) were 1.4%, 8, and 18.4, respectively. All herbicide treatments were applied with a tractor-mounted CO 2 pressurized windshield sprayer calibrated to deliver 20 gal/a at 30 psi and 4.1 mph. Adjuvant and AMS were added per manufacturer recommendation. The first postemergence herbicide application was made on June 21, 2012. The first post-application conditions of air temperature, soil temperature, wind speed, relative humidity and soil moisture were 73ºF, 73ºF, 4 mph, 38%, and adequate, respectively. The second post-application was made on June 25, 2012. Second postapplication conditions of air temperature, soil temperature, wind speed, relative humidity, and soil moisture were 85ºF, 80ºF, 2 mph, 30%, and adequate, respectively. The trial was established as a randomized complete block design with four replications, and plots were 10 × 30 feet.

Results
Crop injury and percentage weed control were both visually rated. No crop injury was observed. Due to inconsistent distribution of weeds, percentage weed control was rated as overall grassy (monocot) and broadleaf (dicot) control (Table 1). Monocot species observed were Cenchrus longispinus (Hack.) Fernald, Digitaria sp. L., and Setaria veridis (L.) P. Beauv. Dicot species observed were Abutilon theophrasti Medik., Amaranthus palmeri S. Watson, Euphorbia maculata L., Kochia scoparia L. Schrad., Proboscidea louisianica (Mill.) Thell, Salsola kali L., Solanum rostratum Dunal, and Xanthium strumarium L. Treatments that produced greater than 91.4% control 62 days after treatment (DAT) were not statistically superior to the best treatments. There were no differences between products for broadleaf control 62 and 83 DAT. Treatments providing greater than 79.8% grass control were not statistically superior to the best treatment 83 DAT.