Southwest Research-Extension Center Field Day 2020

Report of agricultural research from southwest Kansas, published 2020.


Wheat and Grain Sorghum in Four-Year Rotations
A. Schlegel, J. Holman, and A. Burnett Summary In 1996, an effort began to quantify soil water storage, crop water use, and crop productivity on dryland systems in western Kansas. Research on 4-year crop rotations with wheat and grain sorghum was initiated at the Southwest Research-Extension Center near Tribune, KS. Rotations were wheat-wheat-sorghum-fallow (WWSF), wheat-sorghum-sorghum-fallow (WSSF), and continuous wheat (WW). Soil water at wheat planting averaged about 9 in. following sorghum, which is about 3 in. more than the average for the second wheat crop in a WWSF rotation. Soil water at sorghum planting was only about 1.5 in. less for the second sorghum crop compared to sorghum following wheat. The 2019 grain yields of both wheat and grain sorghum in all rotations were much greater than the long-term average. Grain yield of recrop wheat averaged about 75% of the yield of wheat following sorghum. Grain yield of continuous wheat averaged about 60% of the yield of wheat grown in a 4-year rotation following sorghum. Generally, wheat yields were similar following one or two sorghum crops. Similarly, average sorghum yields were the same following one or two wheat crops. Yield of the second sorghum crop in a WSSF rotation averages ~65% of the yield of the first sorghum crop.

Introduction
In recent years, cropping intensity has increased in dryland systems in western Kansas. The traditional wheat-fallow system is being replaced by wheat-summer crop-fallow rotations. Research was conducted to better understand if more intensive cropping is feasible with concurrent increases in no-tillage. Objectives of this research were to quantify soil water storage, crop water use, and crop productivity of 4-year and continuous cropping systems.

Experimental Procedures
Research on 4-year crop rotations with wheat and grain sorghum was initiated in 1996 at the Tribune unit of the Southwest Research-Extension Center. Rotations were WWSF, WSSF, and WW. No-tillage was used for all rotations except for the first two years where reduced tillage was used for wheat following sorghum. Available water was measured in the soil profile (0 to 6 ft) at planting and harvest of each crop. The center of each plot was machine harvested after physiological maturity, and yields were adjusted to 12.5% moisture.

Soil Water
The amount of available water in the soil profile (0 to 6 ft) at wheat planting varied greatly from year to year ( Figure 1). In 2019, available soil water was greater for wheat following two sorghum crops than one sorghum crop, while normally they are similar. Soil water was less for WW than for the second wheat crop in WWSF. Available water at planting of the second wheat crop in a WWSF rotation was generally less than at planting of the first wheat crop, except in 1997 and 2003. Soil water for the second wheat crop averaged more than 3 in. (or about 40%) less than that for the first wheat crop in the rotation. Continuous wheat averaged approximately 0.8 in. less water at planting than the second wheat crop in a WWSF rotation.
Similar to wheat, the amount of available water in the soil profile at sorghum planting varied greatly from year to year (Figure 2), and available water at sorghum planting in 2019 was greater than the long-term average. Soil water was similar following one or two wheat crops. Water at planting of the second sorghum crop in a WSSF rotation was generally less than that at planting of the first sorghum crop. Averaged across the entire study period, the first sorghum crop had about 1.53 in. more available water at planting than the second crop.

Grain Yields
In 2019, wheat yields in all rotations were much greater than the long-term average (Table 1). Averaged across 23 years, recrop wheat (the second wheat crop in a WWSF rotation) yielded about 75% of first-year wheat crop in WWSF. Before 2003, recrop wheat yielded about 70% of first-year wheat. Wheat yields following two sorghum crops are 2 bu/a greater than following one sorghum crop. In many years, continuous wheat yields have been similar to recrop wheat yields. In other years (2003, 2007, 2009, 2014, and 2018), recrop wheat yields were considerably greater than continuous wheat yields.
In 2019, continuous wheat yields were 8 bu/a less than recrop wheat yields (63 vs. 71 bu/a) and averaged 6 bu/a less than recrop wheat.

Introduction
The change from conventional tillage to no-tillage cropping systems has allowed for greater intensification of cropping in semi-arid regions. In the central High Plains, wheat-fallow (1 crop in 2 years) has been a popular cropping system for many decades. This system is being replaced by more intensive wheat-summer crop-fallow rotations (2 crops in 3 years). There has also been increased interest in further intensifying the cropping systems by growing 3 crops in 4 years or continuous cropping. This project evaluates several multi-crop rotations that are feasible for the region, along with alternative systems that are more intensive than 2-or 3-year rotations. The objectives are to 1) enhance and stabilize production of rainfed cropping systems using 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.

Experimental Procedures
The crop rotations are 2-year (wheat-fallow [WF]); 3-year (wheat-grain sorghum-fallow [WSF] and wheat-corn-fallow [WCF]); 4-year (wheat-corn-sorghum-fallow [WCSF] and wheatsorghum-corn-fallow [WSCF]); and continuous sorghum [SS]. All rotations are grown using no-tillage (NT) practices except for WF, which is grown using reduced-tillage (RT). 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 with a weigh-wagon or combine yield monitor. Soil water was measured in 12-inch increments to 96 inches near planting and after harvest either gravimetrically (RT WF) or by neutron attenuation (NT plots).

Results and Discussion
Precipitation averaged 102% of normal (17.90 in.) across the 12-yr study period and was near normal (+/-15%) in 8 out of 12 years with three wet years (>20% above normal) and one exceptionally dry year (42% of normal) (Figure 1). Fallow accumulation, fallow efficiency, and profile available water at wheat planting were greater with WF than all other wheat rotations ( Table 1). The fallow efficiencies of the 3-and 4-yr NT rotations were only 54-68% of WF under RT. With more water available, crop water use was also greater with WF than with wheat in other rotations. There were no differences in available water at wheat planting or crop water use among the 3-and 4-yr rotations.
Fallow accumulation prior to corn planting and profile available soil water at planting was greater following wheat (WCF or WCSF) than following grain sorghum (WSCF) (Table 1). However, the fallow period following wheat was longer, resulting in low fallow efficiencies (~18%) following wheat and only 22% following sorghum. Similar to wheat, corn water use was greater with greater available soil water at planting. Grain sorghum responded similarly to corn, with greater fallow accumulation and soil water at planting (and greater crop water use) when following wheat than following corn or sorghum. Again, fallow efficiencies prior to grain sorghum were low (16-22%).
Wheat yields were greatly above normal in 2019 with yields exceeding 100 bu/a in the 3-yr rotations ( Figure 2). The effect of cropping systems was not consistent across years, with WF sometimes in the highest yielding group and sometimes in the lowest yielding group. Averaged across the 12 years, cropping system had little effect (5 bu/a or less) on wheat yields.
Grain sorghum yields were very good in 2019 with yields greater than 100 bu/a when following wheat ( Figure 3). Sorghum following corn produced 36 bu/a less yield than following wheat, and continuous sorghum yields were 14 bu/a greater than following corn. Average grain sorghum yields following wheat were approximately 50% greater than following corn or sorghum.
Similar to grain sorghum, corn yields were very good in 2019 ( Figure 4) with all rotations yielding 90 bu/a or more. Corn yields following wheat in either the 3-or 4-yr rotations were always greater than corn yields following grain sorghum, except in 2015 where corn yields following sorghum (wsCf) were greater than wCf. On average, corn yields following wheat were about 45% greater than following grain sorghum.

Summary
This study was initiated in 1991 at the Kansas State University Southwest Research-Extension Center near Tribune, KS. The purpose of the study was to identify the effects of tillage intensity on precipitation capture, soil water storage, and grain yield in a wheat-sorghum-fallow rotation. Grain yields of wheat and grain sorghum increased with decreased tillage intensity in a wheat-sorghum-fallow (WSF) rotation. In 2019, available soil water at sorghum planting was greater for no-tillage (NT) than reduced tillage (RT) which was greater than conventional tillage (CT). For wheat there was a similar pattern as sorghum, with available soil water at wheat planting being in the order of NT>RT>CT. Averaged across the 19-yr study, available soil water at wheat planting was similar for NT and RT and approximately 1 inch greater than CT. Average available soil water at sorghum planting was greater in the order RT≥NT>CT. Averaged across the past 19 years, NT wheat yields were 5 bu/a greater than RT and 9 bu/a greater than CT. Grain sorghum yields in 2019 were 50% greater in long-term NT compared to short-term NT with the lowest yields with CT. Averaged across the past 19 years, sorghum yields with long-term NT have been 58% greater than with short-term NT (79 vs. 50 bu/a).

Experimental Procedures
Research on different tillage intensities in a WSF rotation at the Tribune, KS, unit of the Southwest Research-Extension Center was initiated in 1991. The three tillage intensities in this study are conventional (CT), reduced (RT), and no-tillage (NT). The CT system was tilled as needed to control weed growth during the fallow period. On average, this resulted in 4 to 5 tillage operations per year, usually with a blade plow or field cultivator. The RT system originally used a combination of herbicides (1 to 2 spray operations) and tillage (2 to 3 tillage operations) to control weed growth during the fallow period; however, in 2001, the RT system was changed to using NT from wheat harvest through sorghum planting (short-term NT) and CT from sorghum harvest through wheat planting. The NT system exclusively used herbicides to control weed growth during the fallow period. All tillage systems used herbicides for in-crop weed control.

Soil Water
The amount of available water in the soil profile (0-8 ft) at wheat planting varied greatly from year to year ( Figure 1). In 2019, available soil water at wheat planting was greater with NT than RT and least with CT. Averaged across the 19-yr study, available soil water at wheat planting was similar for RT and NT (~ 8 inches) and approximately 1 inch greater than CT. Similar to wheat, the amount of available water in the soil profile at sorghum planting varied greatly from year to year ( Figure 2). In 2019, available soil water at sorghum planting was greater with NT than RT and least with CT. On average, available soil water at sorghum planting was similar for NT and RT and about 1.5 inches greater than CT.

Grain Yields
Wheat yields in 2019 were much greater than the long-term average (Table 1). Since 2001, wheat yields have been depressed in 11 of 19 years, primarily because of lack of precipitation, winterkill (2015), and disease (2017). Reduced tillage and NT increased wheat yields. On average, wheat yields were 9 bu/a higher for NT (30 bu/a) than CT (21 bu/a). Wheat yields for RT were 4 bu/a greater than CT even though both systems had tillage prior to wheat. Yields of NT were significantly less than CT or RT in only 1 of the 19 years.
Grain sorghum yields in 2019 were greater than the long-term average for NT and RT but not for CT (Table 2). Sorghum yields were 50% greater with NT than RT (127 vs. 85 bu/a) while CT yields were the least (23 bu/a). The yield benefit from reducing tillage is greater for grain sorghum than wheat. Grain sorghum yields for RT averaged 20 bu/a more than CT, whereas NT averaged 29 bu/a more than RT. For sorghum, both RT and NT used herbicides for weed control during fallow, so the difference in yield could be attributed to short-term compared with long-term NT. This yield benefit with long-term vs. short-term NT has been observed in most years since the RT system was changed in 2001. Averaged across the past 19 years, sorghum yields with long-term NT have been 58% greater than with short-term NT (79 vs. 50 bu/a). Tillage × year ----------------------bu/a ----------------------    . In 2019, corn yields were similar for all rotations, although averaged across the past 7 years, corn yields were greater following wheat than following corn. There were no significant differences in grain sorghum yields in 2019, which was similar to the multi-year average. Wheat yields were greater than the multiyear average.

Experimental Procedures
A crop rotation study under sprinkler irrigation at the Kansas State University Southwest Research-Extension Center near Tribune, KS, was initiated in the spring of 2012.
The study evaluates four different crop rotations with a limited irrigation allocation. The rotations include 1-and 2-year rotations. The crop rotations are 1) continuous corn; 2) corn-winter wheat; 3) corn-grain sorghum; and 4) continuous grain sorghum (a total of 6 treatments). All rotations are limited to 10 inches of irrigation water annually. All crops are grown no-till, while other cultural practices (hybrid selection, fertility practices, weed control, etc.) are selected to optimize production. All phases of each rotation are present each year and replicated four times. Irrigations are scheduled to supply water at the most critical stress periods for the specific crops and limited to 1.5 inches per week. Soil water is measured at planting, during the growing season, and at harvest in 1-ft increments to a depth of 8 ft. Grain yields are determined by machine harvest. Nitrogen fertilizer (UAN) was surface-applied (stream) in March to all crops (240 lb N/a for corn, 160 lb N/a for sorghum, and 120 lb N/a for wheat

Results and Discussion
Wheat yields in 2019 (74 bu/a) were greater than the long-term average (53 bu/a) (Tables 1 and 2). Precipitation was near normal from April through September (12.49 inches in 2019 vs. normal of 12.93 inches). Corn yields in 2019 were slightly greater than the long-term average with no differences among rotations. Grain sorghum yields were slightly below the long-term average with no differences among rotations. On average, corn yields are greatest following wheat and least following corn, with little differences in grain sorghum yields following corn or sorghum (Table 2).
Available soil water at corn and sorghum planting and harvest was similar for all rotations in 2019 (Table 3). Precipitation delayed sorghum harvest in 2018 resulting in greater available soil water at sorghum harvest, causing less fallow accumulation following sorghum than corn. Averaged across the 7-year period, fallow accumulation prior to corn was greater following wheat than following sorghum or corn; however, fallow efficiency was greatest following sorghum (shortest fallow period). There were no differences in fallow accumulation or efficiency for grain sorghum following corn or sorghum. There were no differences in crop water use due to rotation for either crop.

Acknowledgement
The project was funded in part by the Western Kansas Groundwater Management District No. 1. Table 1. Grain yield of three crops under limited irrigation as affected by rotation in 2019 ANOVA (P > F) System 0.037 ---0.320 LSD = least significant difference. ANOVA = analysis of variance.      Occasional Tillage in a Wheat-Sorghum-Fallow Rotation

Summary
Beginning in 2012, research was conducted in Garden City and Tribune, KS, to determine the effect of a single tillage operation every 3 years on grain yields in a wheat-sorghum-fallow (WSF) rotation. Grain yields of wheat and grain sorghum were generally not affected by a single tillage operation every 3 years in a WSF rotation. Grain yield varied greatly by year from 2014 to 2019. Wheat yields ranged across years from mid-20s to 90 bu/a at Tribune and less than 10 to near 100 bu/a at Garden City. Grain sorghum yields ranged from 40 to greater than 140 bu/a, depending upon year and location. In 2019, wheat yields at Garden City were less when tillage was implemented post-wheat in 2016. There were no other years or locations were grain yields were significantly affected by a single tillage operation. However, at Tribune, when averaged across the 6-year period, a single tillage after wheat harvest reduced grain sorghum yields compared to a complete no-till (NT) system. At Garden City, averaged across the 6-year period, wheat yields were greatest following a one-time tillage prior to wheat. This indicates that if a single tillage operation is needed to control troublesome weeds, tillage during fallow prior to wheat planting may be better than tillage after wheat harvest. Furthermore, if herbicide-resistant weed populations were high enough to cause yield reductions, then tillage might improve yields.

Introduction
Previous research has shown lower dryland wheat and grain sorghum yields with reduced tillage compared with NT in a wheat-sorghum-fallow (WSF) rotation (Schlegel et al., 2018). The reduced tillage systems generally used four or more tillage operations in the 3-year rotation. With increased incidence of herbicide-resistant weeds, the use of a complete NT system may not be economical and tillage may be needed for effective control. The objective of this research project is to determine the effect of a single tillage operation every 3 years on grain yields in a WSF rotation.

Procedures
Research on occasional tillage intensities in a predominantly no-tillage WSF rotation at the Kansas State University Southwest Research-Extension Center research stations at Garden City and Tribune, KS, was initiated in 2012. The three tillage treatments in this study are a single tillage in May or June during fallow, a single tillage after wheat harvest, and a complete NT system. A sweep plow (Minimizer by Premier Tillage) was used for all tillage operations. When needed, herbicides were used to control weeds during fallow for all treatments. All treatments used herbicides for in-crop weed control. All other cultural practices (variety/hybrid, seeding rate, fertilization, etc.) were the same for all treatments.

Results and Discussion
Weeds were effectively controlled in all treatments and there were no visual differences in weed population across treatments.
At Tribune, wheat yields were much greater in 2019 (89 to 93 bu/a) compared with 49 to 51 bu/a for the 6-year average (Table 1). There were no significant yield differences among tillage treatments in any year or across years. Grain sorghum yields were very good in 2019 ranging from 129 to 132 bu/a (Table 2). Similar to wheat, there were no significant yield differences among tillage treatments in any year. However, averaged across years, no-till produced greater yields than tillage post-wheat harvest.
At Garden City, wheat yields in 2018 were very low at 2 to 7 bu/a (Table 3). Between November 1, 2017, and April 1, 2018, 0.4 inches of precipitation was received, compared to the long-term period average of 3.46 inches. Wheat yields in 2014 were severely reduced by hail. Wheat yield in 2019 was much greater (83 to 100 bu/a) compared with the 40 to 44 bu/a 6-year average (Table 1). Across the 6 years, wheat yields averaged greater with a single tillage ahead of wheat planting. At this location, winter triticale forage yields have been more with a single tillage compared to NT due to more plant available water at wheat planting with a single tillage (Holman et al., 2020). In 2019 wheat yields at Garden City were less when tillage was implemented post-wheat in 2016. It is possible the lower wheat yield in 2019 was a result of lower average grain sorghum yield in the post-wheat tillage treatment in 2017. However, grain sorghum yield was not affected by treatment in any year or across years. Grain sorghum yields in 2018 were good, with all yields near 90 bu/a or greater (Table 4). Grain sorghum yields were lower in 2019 averaging 40 bu/a. Across years, there were no differences in grain sorghum yields averaging 70 bu/a.
In other research (Schlegel et al., 2018), reduced tillage systems (with four tillage operations) produced lower yields than a complete no-tillage system in a WSF rotation. However, in this study, a single tillage operation during fallow prior to wheat planting in a 3-year WSF rotation generally had little effect on wheat or grain sorghum yields from 2014 to 2019 at Garden City or Tribune, KS.
There is a tendency for wheat yields at Garden City and grain sorghum yields at Tribune to be less following a single tillage post-wheat compared to no-till or single tillage prior to wheat. These results suggest if a single tillage is needed for weed control the best timing may be prior to wheat during the fallow year.      Year  Tillage  2014  2015  2016  2017  2018  2019 Average

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. Using 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.

Experimental Procedures
This study was conducted at the Southwest Research-Extension Center dryland station near Tribune, KS. From 2007 through 2019, corn and grain sorghum were planted into standing wheat stubble of three heights. Optimal (high) cutter-bar 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 cutter-bar height, and the third treatment was stubble remaining after stripper header harvest. For 2019, these heights were 16, 8, and 24 in. (cut after 2018 wheat harvest). In 2019, corn and grain sorghum were seeded at rates of 15,000 seeds/a and 45,000 seeds/a, respectively. Nitrogen was applied to all plots at a rate of 100 lb/a. Starter fertilizer (10-34-0 nitrogen-phosphorus-potassium (N-P-K)) was surface-dribbled offrow 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 mea-surements were obtained with neutron attenuation to a depth of 6 ft in 1-ft increments at seeding and harvest to determine water use and water use efficiency.

Results and Discussion
The 2019 growing season was generally normal or slightly above in precipitation (19.59 inch in 2019 vs. normal of 17.90 inch) and below normal in open pan evaporation (63.72 inch vs. normal of 71.40 inch). This produced above average yields for both corn and sorghum (Tables 1-4). With the good growing conditions, stubble height had little effect on corn yield or other parameters. When averaged across years 2007 to 2019, corn yields were 8-9 bu/a greater in high or strip-cut than low-cut wheat stubble ( Table 2). Biomass production and water use efficiency were also greater with the taller stubble.
Grain sorghum yields in 2019 were not affected by stubble height (Table 3). When averaged across years from 2007 through 2019, the highest yields were obtained in the high-cut stubble and the lowest yields in the low-cut stubble ( Table 4). None of the other measured parameters for grain sorghum were affected by wheat stubble height except for greater water use efficiency in high-cut vs. low-cut stubble.

A. Schlegel and H.D. Bond
Summary Long-term research shows that phosphorus (P) and nitrogen (N) fertilizer must be applied to optimize production of irrigated corn in western Kansas. In 2019, N applied alone increased yields by 71 bu/a, whereas P applied alone increased yields 10 bu/a. Nitrogen and P applied together increased yields up to 131 bu/a, which is 10 bu/a less than the 10-year average of 141 bu/a. Application of 120 lb N/a (with highest P rate) produced 97% of maximum yield in 2019, which is slightly greater than the 10-year average. Application of 80 instead of 40 lb P 2 O 5 /a increased average yields 4 bu/a. Average grain N content reached a maximum of 0.6 lb/bu while grain P content reached a maximum of 0.15 lb/bu (0.34 lb P 2 O 5 /bu). At the highest N and P rate, apparent fertilizer nitrogen recovery in the grain (AFNR g ) was 41% and apparent fertilizer phosphorus recovery in the grain (AFPR g ) was 60%.

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 Kansas State University 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 [Pioneer 1173H (2010, Pioneer 1151XR (2011) The corn is irrigated 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 15.5% moisture. Grain samples were collected at harvest, dried, ground, and analyzed for N and P concentrations. Grain N and P content (lb/bu) and removal (lb/a) were calculated. Apparent fertilizer N recovery in the grain (AFNR g ) was calculated as N uptake in treatments receiving N fertilizer minus N uptake in the unfertilized control divided by N rate. The same approach was used to calculate apparent fertilizer P recovery in the grain (AFPR g ). Grasshoppers were treated by aerial application of insecticide.

Results
Corn yields in 2019 were only 2% higher than the 10-year average (Table 1). Nitrogen alone increased yields 71 bu/a, whereas P alone increased yields 7-10 bu/a. However, N and P applied together increased corn yields up to 131 bu/a. Maximum yield was obtained with 200 lb/a N with 80 lb/a P 2 O 5 . Corn yields in 2019 (averaged across all N rates) were 4 bu/a greater with 80 than with 40 lb/a P 2 O 5 applied.
The 10-year average grain N concentration (%) increased with N rates but tended to decrease when P was also applied, presumably because of higher grain yields diluting N content (Table 2). Grain N content reached a maximum of 0.6 lb/bu. Nitrogen removal (lb/a) was greater at the higher yield levels. Maximum N removal (116 lb/a) was attained with 200 lb N and 80 lb P 2 O 5 /a. At the highest N and P rate, AFNR g was 41% and AFPRg was 60%. Similar to N, average P concentration increased with increased P rates but decreased with higher N rates. Grain P content (lb/bu) of about 0.15 lb P/bu (0.34 lb P 2 O 5 /bu) was greater at the highest P rate with low N rates. Grain P removal averaged 29 lb P/a at the highest yields.

Acknowledgment
The International Plant Nutrition Institute partially supported this research project.

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 Kansas State University 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. Grain sorghum (Pioneer 85G46 in 2010-2011, Pioneer 84G62 in 2012-2014, Pioneer 86G32 in 2015, Pioneer 84G62 in 2016-2017, and Pioneer 85P44 in 2018-2019) 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. Grain samples were collected at harvest, dried, ground, and analyzed for N, P, and K concentrations. Grain N, P, and K content (lb/bu) and removal (lb/a) were calculated. Apparent fertilizer N recovery in the grain (AFNR g ) was calculated as N uptake in treatments receiving N fertilizer minus N uptake in the unfertilized control divided by N rate. The same approach was used to calculate apparent fertilizer P recovery in the grain (AFPR g ) and apparent fertilizer K recovery (AFKR g ).

Results
Grain sorghum yields in 2019 were 3% lower than the 10-year average (Table 1). Nitrogen alone increased yields 66 bu/a while P alone increased yields 6 bu/a. However, N and P applied together increased yields up to 85 bu/a. Averaged across the past 10 years, N and P applied together increased yields up to 78 bu/a. In 2019, 40 lb/a N (with P) produced about 74% of maximum yield, which is less than the 10-year average of 83%. The 10-year average for 80 lb/a N (with P) and 120 lb/a N (with P) was 93 and 94% of maximum yield, respectively. Sorghum yields were not affected by K fertilization, which has been the case throughout the study period.
The 10-year average grain N concentration (%) increased with N rates but tended to decrease when P was also applied, presumably because of higher grain yields diluting N content (Table 2). Grain N content reached a maximum of ~0.7 lb/bu. Maximum N removal (lb/a) was obtained with 160 lb N/a or greater with P. Similar to N, average P concentration increased with P application but decreased with higher N rates. Grain P content (lb/bu) of ~0.15 lb P/bu (0.34 lb P 2 O 5 /bu) was similar for all N rates when P was applied. Grain P removal was similar for all N rates of 40 lb/a or greater with P removal ranging from 19 to 22 lb/a. Average K concentration (%) and content (lb/bu) tended to decrease with increased N rates. Similar to P, K removal was similar for all N rates of 40 lb/a or greater plus K ranging from 22 to 26 lb/a. At the highest N, P, and K rate, apparent fertilizer recovery in the grain was 31% for N, 65% for P, and 38% for K.

Acknowledgment
The International Plant Nutrition Institute partially supported this research project.

Introduction
Annual forage crops are grown for a shorter time and require less moisture than traditional grain crops. Including annual forages in the cropping system might enable increased cropping intensity and opportunistic cropping. "Opportunistic cropping," or "flex cropping," is the planting of a crop when conditions (soil water and precipitation outlook) are favorable and fallowing when unfavorable. Forage producers in the region commonly grow winter triticale, forage sorghum, or spring triticale/oat. Producers are interested in forage crop rotations that enable increased pest management control options, spread out equipment and labor resources over the year, reduce weather risk, and increase profitability. Growing forages throughout the year greatly reduces the risk of crop failure. Understanding the yield relationship to PAW and GSP would help producers better meet their forage needs.

Study Objectives
1. Quantify yield relationship of winter, spring, and summer forages with PAW and GSP. 2. Determine water use efficiency of winter, spring, and summer forages.

Experimental Procedures
Annual forages were grown as part of several different rotation experiments near Garden City, KS. Plant available water, growing season precipitation, and forage yield were measured annually. Data for winter triticale and forage sorghum were available from 2008 through 2019, and spring triticale from 2012 through 2019.
Annually, winter triticale was planted at the end of September, spring triticale was planted at the beginning of March, and forage sorghum was planted at the beginning of June. Crops were harvested at early heading to optimize forage yield and quality (Feekes 10.1) (Large 1954). Annually, winter triticale was harvested approximately May 15, spring oat was harvested approximately June 1, and forage sorghum was harvested approximately the end of August. Forage yields were determined from a 3-× 30-ft area cut 3 in. high using a small plot Carter forage harvester for each plot. Forage yield was measured at each harvest. Gravimetric soil moisture content was measured at planting and harvest to a depth of 6 ft using 1-ft increments. Precipitation storage efficiency (percent of precipitation stored during the fallow period) was quantified for each fallow period, and crop water use efficiency (forage yield divided by soil water used plus precipitation) was determined for each crop harvest. Crop yield response to plant available water at planting was regressed to estimate yield. These yield data will eventually be used to develop a yield prediction model based on historical or expected weather conditions when sufficient years of data are obtained.
Data produced by this study will be used to evaluate the economics of forage rotations and tillage. Production costs and returns will be calculated using typical values for the region. The implication of using forages on crop insurance dynamics and risk exposure is a critical component of a producer's decision-making process and will be evaluated at the conclusion of this study.

Winter Triticale
Winter triticale forage yield was correlated to PAW and GSP, although yield response was highly variable. Plant available water explained 26% and GSP explained 29% of the variability in forage yield (Figures 1 and 2). Together, PAW and GSP explained 57% of the variability in forage yield (Figure 3). For every inch of water used (soil water plus GSP), yield was increased by 540 lb/a. Averaged across the study period, yield was 3,900 lb/a.

Spring Triticale
Spring triticale forage yield was significantly correlated to PAW and GSP, and yield response was variable. Plant available water explained 12% and GSP explained 8% of the variability in forage yield (Figures 4 and 5). Together, PAW and GSP explained 22% of the yield variability; suggesting something other than moisture, most likely temperature greatly impacts yield ( Figure 6). For every inch of water used (soil water plus GSP), yield was increased by 214 lb/a. Averaged across the study period, yield was 1,500 lb/a.

Forage Sorghum
Forage sorghum forage yield was correlated to PAW and GSP, and yield response was variable. Plant available water explained approximately 20% and GSP explained 7% of the variability in forage yield (Figures 7 and 8). Together, PAW and GSP explained 30% of the variability in forage yield (Figure 9). For every inch of water used (soil water plus GSP), yield was increased by 460 lb/a. Averaged across the study period, yield was 5,600 lb/a.   Inches water use, ASW + GS Figure 6. Spring triticale yield response to water use (soil water plus growing season precipitation) and average yield (bold line) across the study period.     Figure 9. Forage sorghum yield response to water use (soil water plus growing season precipitation) and average yield (bold line) across the study period.

Introduction
Historically, herbicides such as Acuron, Degree Xtra, Resicore, and Warrant were applied preemergence to corn to provide residual weed control until the crop became established and competitive with the weeds. As resistance issues to postemergence herbicides have increased, applying reduced rates of these residual herbicides preemergence and as part of a planned postemergence application has become increasingly popular. Applying these herbicides in a sequential program not only extends the residual weed control but also increases the modes of action used in the postemergence component. The objective of this study was to compare residual herbicides applied sequentially at split rates for efficacy in corn.

Experimental Procedures
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, to compare various herbicides applied preemergence (PRE) followed by postemergence (POST) or early postemergence (EPOST) for weed control in corn. All herbicides were applied using a tractor-mounted, compressed CO 2 sprayer delivering 19.4 GPA at 4.1 mph and 30 psi. Application, environmental, and weed information are shown in Table 1. Plots were 10 by 35 feet and arranged in a randomized complete block design with four replications. Soil was a Beeler silt loam with 2.4% organic matter and pH of 7.6. Visual estimates of weed control were taken on June 17, July 8, and July 22, 2019. These dates were 7, 28, and 42 days after the POST applications (DA-C), respectively. Corn injury ratings were determined on June 7, June 17, and June 27, 2019, and these dates were 4 days after the EPOST applications (DA-B) and 7 or 17 DA-C. Yields were determined on September 19, 2019, by mechanically harvesting the center two rows of each plot and adjusting grain weights to 15.5% moisture.

Results and Discussion
All herbicides controlled Russian thistle, quinoa, and green foxtail 96% or more regardless of rating date, and did not differ between treatments (data not shown). Kochia control at 7 and 42 DA-C was slightly less with Capreno (thiencarbazone/tembotrione) plus Degree Xtra (acetochlor/atrazine), Clarity (dicamba), and glyphosate applied EPOST compared to the other herbicides and with Diflexx Duo (dicamba/ tembotrione) plus Degree Xtra and glyphosate applied EPOST at 42 DA-C (Table 2). All herbicides except Acuron (atrazine/S-metolachlor/mesotrione/bicyclopyrone) PRE followed by Acuron plus glyphosate POST controlled Palmer amaranth 98% or more at 7 and 28 DA-C. By 42 DA-C, no differences occurred among herbicides for Palmer amaranth control. Corn chlorosis was 6 to 11% with the EPOST herbicides at 4 DA-B but did not persist (Table 3). All POST treatments containing mesotrione (Acuron, Harness Max, and Resicore) caused 11 to 19% corn chlorosis at 7 DA-C, but visible corn injury at 17 DA-C was 5% or less regardless of herbicide treatment. Grain yields were 38 to 52 bu/a more from herbicide-treated corn than from the nontreated controls. However, corn yields did not differ between herbicide treatments.
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.        Table 3. Crop response to sequential and early postemergence herbicides applied in corn  continued Table 3. Crop response to sequential and early postemergence herbicides applied in corn

Introduction
Residual weed control is important in any summer annual crop, and particularly important in grain sorghum. Postemergence weed control options in sorghum are limited compared to other crops, especially for grass weeds. Therefore, maximizing the length of the time the crop can grow without weed competition is critical. The objective of this study was to compare preemergence herbicides for efficacy in grain sorghum.

Experimental Procedures
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, to compare various preemergence herbicides for residual weed control in grain sorghum. All herbicides were applied using a tractor-mounted, compressed CO 2 sprayer delivering 19.4 GPA at 4.1 mph and 30 psi. Application, environmental, and weed information are shown in Table 1. Plots were 10 by 35 feet and arranged in a randomized complete block design with four replications. Soil was a Ulysses silt loam with pH of 7.9 and organic matter of 3.4%. Visual weed control estimates were made on July 16 and August 9, 2019. These dates were 7 and 31 days after the postemergence treatment (DA-B), respectively. Sorghum yields were determined on October 15, 2019, by mechanically harvesting the center two rows of each plot and adjusting grain weights to 14.0% moisture.

Results and Discussion
All herbicides controlled quinoa 88% or more at 7 DA-B and 95% or more at 50 DA-B, and did not differ between treatments. Similarly, crabgrass control was 95% or more regardless of herbicide treatment or rating date (data not shown). Kochia control at 7 DA-B was 93% or more with all herbicides except Halex GT (S-metolachlor/glyphosate/mesotrione) at 64 oz/a plus atrazine PRE or Degree Xtra (acetochlor/atrazine) PRE (Table 2). These treatments, along with Halex GT at 80 oz/a plus atrazine PRE and Bicep Lite II Magnum (atrazine/S-metolachlor) PRE controlled kochia less than 90% at 50 DA-B. Lumax EZ and Lexar EZ (both S-metolachlor/atrazine/mesotrione) PRE were the only treatments to control Russian thistle more than 80% at 7 DA-B. However, no differences between herbicide treatments occurred for Russian thistle control at 50 DA-B. Palmer amaranth control was similar among herbicides at 7 DA-B.
At 50 DA-B, Halex GT at 64 or 80 oz/a plus atrazine PRE and Bicep Lite II Magnum PRE provided less than 90% Palmer amaranth control. Grain yields were 88 to 106 bu/a from herbicide-treated sorghum plots, but did not differ from sorghum receiving no herbicide treatment (83 bu/a) (data not shown).
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer. ------

Summary
In this study, herbicides were tested to compare application of single and sequential treatments for weed control in corn. Quinoa and Russian thistle control was 95% or more regardless of herbicide treatment. Anthem Maxx, Resicore, and Corvus followed by Harness Max provided good control of Palmer amaranth. Acuron applied preemergence and Anthem Maxx plus Callisto and atrazine early postemergence were less effective on kochia than other herbicides, whereas Anthem Maxx plus Callisto and atrazine applied preemergence and Halex GT applied early postemergence were less effective on green foxtail. Grain yields from all herbicide-treated corn were substantially greater than for the nontreated control plots.

Introduction
As of 2019, 28 weed species have been reported to have herbicide resistance in Kansas. Use of herbicides with multiple modes of action and sequential applications of herbicides are two effective strategies to combat the development of herbicide-resistant weed species. The objective of this study was to compare single applications of herbicides with multiple modes of action to sequential applications for efficacy in corn.

Experimental Procedures
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, to compare preemergence (PRE), early postemergence (EPOST), or PRE followed by postemergence (POST) herbicides for weed control in corn. All herbicides were applied using a tractor-mounted, compressed CO 2 sprayer delivering 19.4 GPA at 4.1 mph and 30 psi. Application, environmental, and weed information are shown in Table 1. Plots were 10 by 35 feet and arranged in a randomized complete block design with four replications. Soil was a Beeler silt loam with 2.4% organic matter and pH of 7.6. Visual weed control ratings were taken on June 27 and July 23, 2019. These dates were 1 and 27 days after the POST treatment (DA-C), respectively. Corn yields were determined on September 19, 2019, by mechanically harvesting the center two rows of each plot and adjusting grain weights to 15.5% moisture.

Results and Discussion
Quinoa and Russian thistle control was essentially complete with all herbicides regardless of rating date (data not shown). All herbicide treatments containing Anthem Maxx (pyroxasulfone/fluthiacet) PRE controlled Palmer amaranth 95 to 100% at 1 and 27 DA-C, as did the treatment of Resicore (acetochlor/mesotrione/clopyralid) PRE (Table 2). Corvus (isoxaflutole/thiencarbazone) plus atrazine PRE followed by Harness Max (acetochlor/mesotrione) plus atrazine and glyphosate POST also controlled Palmer amaranth 95% at 27 DA-C. Kochia control at 1 and 27 DA-C was slightly less with Acuron (S-metolachlor/atrazine/mesotrione/bicyclopyrone) PRE or Anthem Maxx plus Callisto (mesotrione) and atrazine EPOST, compared to the most efficacious treat-ments. Green foxtail control was 95% or more with all herbicides except Anthem Maxx plus Callisto and atrazine PRE and Halex GT (S-metolachlor/glyphosate/mesotrione) plus atrazine EPOST at 27 DA-C. Yields of herbicide-treated corn plots ranged from 99.8 to 115.4 bu/a, which was 61 to 77 bu/a more than nontreated corn.
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer. ---2 ---Green foxtail Height (inch) 0 1 to 2 2 to 3 Density (plants/10 ft 2 ) ---10 1   all herbicides except Coyote PRE followed by KFD-356-02 POST or KFD-365-02 at 6 oz/a plus atrazine PRE followed by 2,4-D POST. No visible crop injury was observed from any treatment, and grain yields could not be determined due to the intense Palmer amaranth pressure.
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.

Introduction
Terbuthylazine is a photosynthesis-inhibiting herbicide similar to atrazine. In areas where atrazine use is restricted, such as Europe, terbuthylazine is used for preemergence weed control in corn. In the United States, terbuthylazine is not currently marketed as an herbicide. This study was conducted to compare terbuthylazine with atrazine for weed control in grain sorghum.

Experimental Procedures
An experiment was conducted at the Kansas State University Southwest Research-Extension Center near Garden City, KS, to compare terbuthylazine and atrazine alone and in combinations for preemergence weed control in grain sorghum. All herbicides were applied using a tractor-mounted, compressed CO 2 sprayer delivering 19.4 GPA at 4.1 mph and 30 psi. Application, environmental, and weed information are shown in Table 1. Plots were 10 by 35 feet and arranged in a randomized complete block design with four replications. Soil was a Ulysses silt loam with pH of 7.9 and 3.4% organic matter. Visual estimates of weed control were determined on July 16 and July 29, 2019. These dates were 28 and 41 days after herbicide treatment (DAT). Sorghum yields were determined by mechanically harvesting the center two rows of each plot and adjusting grain weights to 14.0% moisture.

Results and Discussion
Quinoa and crabgrass control with all herbicides was 95% or more regardless of evaluation date and did not differ (data not shown). At 28 DAT, kochia and Palmer amaranth control was 80% or more with all herbicides except terbuthylazine at 23 oz/a or atrazine at 24 oz/a (Table 2). By 41 DAT, control of each of these species was best (85%) when Bicep II Magnum (S-metolachlor/atrazine) at 64 oz/a was applied. All herbicides controlled Russian thistle similarly at 28 DAT. Bicep II Magnum provided the best Russian thistle control at 41 DAT (88%), and only terbuthylazine at 23 oz/a and atrazine at 24 oz/a were less efficacious. No visible sorghum injury was observed from any of the herbicides tested. Grain yields were increased 31 to 54% by most herbicide treatments compared to nontreated sorghum. However, sorghum treated with atrazine at 24 oz/a yielded similarly to the nontreated controls.
Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Persons using such products assume responsibility for their use in accordance with current label directions of the manufacturer.  Amy began her role as Area 4-H Specialist in early 2016. She provides leadership and resources to 24 counties in the area of 4-H youth development, including community clubs, school enrichment, camping and afterschool programs. She is passionate about teaching young people of all backgrounds valuable life skills so that they can reach their fullest potential in adulthood.

Sarah Zukoff
Extension Specialist, Entomologist B.S. and M.S., Georgia Southern University Ph.D., University of Missouri Sarah has a joint research and extension appointment. Her work focuses on arthropods in field and forage crops as well as rangeland systems.