Intensive Management Strategies to Close Wheat Yield Gaps in Central Kansas

Winter wheat is the most widely sown crop in Kansas, and yields had not surpassed 50 bushels per acre until 2015-16, when average state wheat yield was 57 bushels per acre. However, recent estimates of the long-term winter wheat yield potential in central Kansas indicate that it lies around 75 bushels per acre. A particular crop’s yield gap in a given region is determined by the difference between potential and actual yields. The long-term yield gap in Kansas is approximately 45 bushels per acre, which corresponds to more than 50% of the yield potential. Yield gaps have the potential to be economically reduced to approximately 30%. The two possible ways to reduce yield gaps are through improved agronomic management or increasing yield potential through improved genetics. Our hypothesis is that improved management can largely contribute to closing wheat yield gaps in central Kansas. Our objectives were to quantify the partial contribution of different management strategies toward closing the wheat yield gap in central Kansas, including fertilization, plant population density, fungicide, and growth regulator applications, all individually or in combination

Wheat Grain Yield and Protein Response to Nitrogen and Sulfur Rates

Winter wheat is often double-cropped after soybeans in no-tillage systems. The soybean crop removes large quantities of sulfur (S), which might unbalance ratios of nitrogen (N) to S for the following wheat crop. Our objective was to evaluate the responses of two wheat varieties to three N and four S rates representing a range of N:S ratios. The experiment was arranged as a complete factorial with a split-split-plot design. Variety was the whole-plot, N the sub-plot, and S the sub-sub plot. Nitrogen rates were 50, 100, and 150% of the recommended rate for 60 bu/a, which corresponded to ~45, 87, and 130 lb N/a. Sulfur rates were 0, 10, 20, and 40 lb S. The two locations (Manhattan and Belleville) were conducted under no-till and data were pooled for the statistical analysis. Nitrogen by S interactions occurred for grain yield and protein. The 45 lb N/a with 0, 10, or 40 lb S yielded similarly, while 20 lb S reduced yield by 4 bu/a. The 87 lb N/a increased yield by 9 bu/a from the 45 lb N/a with all S rates yielding similarly. The 130 lb N/a increased yield by 18 bu/a from the 45 lb N/a with 10 lb S resulting in the lowest yield, with 0 and 20 lb S yielding the highest. Zero and 40 lb S resulted in similar yields across all N rates. The 45 and 130 lb N/a with 10 lb S produced protein of 10.9% and 11.9%, respectively. However, 130 lb N/a with 0 or 10 lb S increased protein to 12.6–12.8%. This research will be continued for two more years at three locations per year to better explore the interactive effects of N, S, and variety

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Wheat Variety Response to Seeding Rate Across a Range of Kansas Environments in 2019–2020

Due to the inconsistencies of wheat response to seeding rate, we conducted an experiment in seven Kansas locations during the 2019–2020 winter wheat growing season with the objectives of determining whether higher yielding environments warrant lower seeding rates than lower yielding environments, and whether this response depends on wheat variety. The wheat varieties ‘Larry,’ ‘SY Monument,’ ‘Tatanka,’ and ‘WB4303’ were seeded at 200,000, 400,000, 800,000, and 1,600,000 seeds per acre at Ashland Bottoms, Belleville, Conway Springs, Great Bend, Hutchinson, Leoti, and Manhattan. Growing season rainfall in the studied locations ranged from 6.7 to 24.2 inches, which corresponded to anywhere from 16 to 80% of the reference evapotranspiration. Stand count increased with increases in seeding rate but final population was dependent on the location: in Great Bend, the range in population evaluated was only from 248,270 to 464,590 due to an extremely dry period following wheat sowing; while at the other locations there was a larger range in populations evaluated. Regarding grain yield, plant population also interacted with location: grain yield increased linearly with increases in seeding rate in the five lowest yielding environments, and plateaued at 800,000 seeds/a in the two highest yielding environments. Likewise, varieties interacted with the location so that in two locations there were no varietal effects; while in five locations the difference between the lowest and highest yielding varieties ranged from 5.2 to 9.9 bushels per acre. These results suggested that wheat grain yield responses to seeding rate were dependent on location, and that varieties yielded differently by location but the response of the different varieties to seeding rate was similar

Plant Population and Fungicide Treatment Reduce Winter Wheat Yield Gap in Kansas

Despite the large winter wheat yield gap in Kansas, limited research is available on integrated agronomic practices to increase grain yield. Our objective was to quantify the contribution of individual and combined management practices to reduce wheat yield gap. An incomplete factorial treatment structure established in a randomized complete block design was conducted in three locations in Kansas during 2016–2017 to evaluate the impacts of 14 treatments on yield and grain protein concentration of the modern wheat variety ‘Everest.’ We individually added six treatments to a low-input standard control or removed from a high-input intensive control, which received all treatments. Treatments were: additional nitrogen, sulfur or chloride, increased plant population, foliar fungicide, and plant growth regulator. In Manhattan, the intensive control increased grain yield by 6 bu/a as compared to the standard control, mostly led by additional nitrogen, sulfur, increased population, and fungicide (3–6 bu/a). In Belleville and Hutchinson, foliar fungicide increased grain yield on average by 19 bu/a. Additional nitrogen was the only treatment that increased grain protein concentration across all locations. Our results suggest that integrated pest management should be preferred over an intensive program with prophylactic pesticide application

Wheat Variety-Specific Response to Seeding Rate Under Intensive Management Conditions in Western Kansas in 2019–2020

Wheat response to seeding rate is variable and depends on resource availability during the growing season (e.g., fertility, moisture, and temperature). Our objective was to evaluate winter wheat population and grain yield responses to seeding rate and its interaction with variety in a highly-managed production system where manageable stresses were limited. One experiment evaluating the response of the wheat varieties Joe, WB-Grainfield, Langin, and LCS Revere to seeding rates ranging from 200,000 to 1,000,000 seeds per acre was established in a field managed by growers that consistently win state and national wheat yield contests near Leoti, KS. The trials were established on September 25, 2019, after a long fallow. The growing season was extremely dry, with only 6.3 inches of cumulative precipitation (corresponding only to 15% of atmospheric water demand). Stand count increased with increases in seeding rate but final population was closer to the target under low populations. Varieties differed statistically in grain yield but all varieties responded similarly to seeding rate. The lowest yield was recorded across varieties in the treatment with 200,000 seeds/a, with the treatments ranging from 400,000 to 1,000,000 seeds/a all resulting in the same yield level. The variety WB-Grainfield underperformed the other varieties, likely due to more damage from a spring freeze occurring in April 2020. These results suggest that wheat grain yield responses to seeding rate were not dependent on variety, with optimum seeding rates as low as 400,000 seeds/a. We note that increasing seeding rates past this point led to numerical, but not statistical, increases in yield

Integrated Wheat Management for Improved Wheat Yield and Protein in Kansas

In Kansas, seven to nine million acres of winter wheat are sown annually with grain yields averaging about 40 bu/a. Variety selection and management strategies are critical decisions to maximize wheat yield. Thus, the main objective of this experiment was to evaluate four wheat varieties and their response to six management strategies at three locations in Kansas. These strategies included a farmer practice, enhanced fertility, economical intensification, increased foliar protection, water-limited yield, and increased plant productivity. Locations were pooled based on tillage practice and envi­ronment within Kansas; conventional till in central (Hutchinson and Belleville), and no-till in western (Leoti). In the conventional till analysis, enhanced fertility increased grain yield from 63 bu/a in the farmer practice to 72 bu/a and no other manage­ment strategy further increased yields. Thus, WB4303, WB4458, and WB-Grainfield produced a similar grain yield of 72 bu/a; however, Zenda yield was less (68 bu/a). The water-limited yield treatment increased protein concentration from 11.7% in the farmer practice to 14.1%. Protein concentration was 13.1% and 13.6% for WB-Grain­field and WB4303, respectively. In the no-till analysis, the farmer practice and increased plant productivity yielded 51 bu/a and the enhanced fertility increased yields to 64 bu/a. Joe yielded 61 bu/a, which was significantly greater than WB4458 and Byrd (~57 bu/a). In the conventional till, farmer practice measured a protein concentration of 11.2%, which was increased to 12.8% and 13.2% by enhanced fertility and increased plant productivity, respectively. The wheat varieties WB-Grainfield, Joe, and Byrd all had a protein concentration of 12.4%, and WB4458 increased protein concentration to 13.3%. The grain yield and protein concentration of different varieties responded to increases in management input intensity depending on tillage practices and environ­ments. Improved agronomic management based on variety-specific characteristics can help increase wheat productivity in Kansas

Wheat Variety-Specific Grain Yield Response to Plant Density Under Intensive Management Conditions in Western Kansas

Seeding rate determines the first yield component of field crops, which is the plant population. However, wheat is less responsive to plant populations than other crops due to the high plasticity in tillering potential, and this responsiveness depends on resource availability. The objective of this project was to evaluate winter wheat popu­lation, grain yield, and grain test weight responses to seeding rate and its interaction with variety in a highly managed production system where manageable stresses were limited. Experiments evaluating the response of the wheat varieties ‘Joe,’ ‘WB-Grain­field,’ ‘Langin,’ and ‘LCS Revere’ to seeding rates ranging from 200,000–1,000,000 seeds per acre were established in a field managed by growers who consistently win state and national wheat yield contests near Leoti, KS. Trials were established at a relatively late date in 2017–2018 (delayed by pre-sowing rainfall), and at the optimal timing during 2018–2019. Growing seasons contrasted in that 2017–2018 was dry (approximately 6 inches in-season precipitation) and had warm grain filling condi­tions, and 2018–2019 was cool and moist (appx. 13 inches in-season precipitation). Stand count increased with increases in seeding rate both years but final population was closer to the target population during 2017–2018. Grain yield response to seeding rate and to variety depended on year, but all varieties responded similarly to seeding rate. In 2017–2018, grain yield increased linearly from appx. 40–60 bushels per acre with increases in seeding rate from 200,000–400,000 seeds per acre. During 2018–2019, the lowest yield was recorded across varieties in the plots with 200,000 seeds per acre, with the treatments ranging from 400,000–1,000,000 seeds per acre all resulting in the same yield level. Grain yield as affected by emerged plant population (instead of seeding rate) showed similar trends, though quadratic relationships indicated a maximum yield at about 500,000–580,000 plants per acre in 2018–2019. Grain test weight was impacted by the interaction of variety, seeding rate, and year. Greatest test weight values resulted in 2017–2018, when the test weight of all varieties responded in a quadratic way to seeding rates. In 2018–2019, there was no clear trend in varieties’ test weight responses to population. These results suggest that wheat grain yield responses to seeding rate (and to plant population) are more dependent on sowing date and weather conditions than on variety, with optimum sowing times and a warm fall allowing for seeding rate as low as 400,000 seeds per acre without yield penalty. Meanwhile, later sowing dates and cooler fall conditions required seeding rates of up to 1,000,000 seeds per acre to maxi­mize grain yield

Intensive Wheat Management for Yield and Quality: The Role of Variety, Environment, and Management Practices

Management (M), variety (V), and environment (E) greatly influence wheat yield and quality. With the objective of determining the partial influence of V, E, and M, we conducted a field experiment where we imposed four management intensities to five wheat varieties during six site-years in Kansas and Oklahoma. Management intensities were 1) low-input (N fertility for a yield goal of 60 bu/a); 2) high-input (foliar fungi­cide, sulfur and chloride fertilizers, growth regulator, and nitrogen (N) fertility for a yield goal of 100 bu/a); 3) high-input minus fungicide; and 4) high-input minus addi­tional N. We selected commonly grown wheat varieties with contrasting yield potential and quality characteristics. We used a split-plot design with M as whole-plots (estab­lished in randomized complete block design), and V as sub-plot (completely random­ized within whole-plot). Variance component analyses suggested that E accounted for 63% of the variability in wheat yield and 55% of the variability in grain test weight; G accounted for 1 and 23% of the variability in yield and test weight, and M accounted for 1% of the variability of both. The interactions V × G and E × M accounted for 4 and 9% of the variability in yield, and 10 and 1% of the variability in test weight, respectively. Analysis of variance pooled across the entire dataset considering V and M fixed and E random suggested a significant G × M interaction on yield, which ranged from 49–61 bu/a. Meanwhile, both V and M affected test weight, which ranged from 52–58 lb/bu for the different V and from 55–57 lb/bu for the different M. These results suggest that E has the greatest impact in yield and quality, but there is room for yield improvement through V-specific M, and for quality improvement through V and M separately

Winter Wheat Response to Different Fungicide Management (Products and Timing of Application) During the 2019-2020 Growing Season

Foliar fungicides can improve wheat grain yield in Kansas, but there is limited information on the efficacy of different products as well as the timing of application. We conducted a field study in five Kansas locations to evaluate the yield, test weight, and protein responses of WB-Grainfield to different commercial fungicides applied at different times during the growing season. The trial was conducted in a randomized complete block design to evaluate (1) a non-treated control; Topguard applied at 5 ounces per acre at (2) jointing, (3) heading, and (4) jointing plus heading; (5) Delaro applied at 6 oz/a at jointing; (6) Absolute Maxx applied at 5 ounces per acre at heading; (7) Delaro at jointing plus Absolute Maxx at heading at the rates previously specified; and (8) Nexicor applied at 13 oz/a at heading. The study was conducted near Conway Springs, Great Bend, two sites near Hutchinson (optimum- and late-sowing date), and Leoti. Grain yield across locations ranged from 36 to 72.9 bushels per acre. A significant fungicide by location interaction on grain yield resulted from two locations showing no response to fungicide; two locations resulting in the highest yield when fungicide at heading was presented in the evaluated treatment; and one location showing all fungicide treatments outyielding the control. Similar results were obtained for test weight, where fungicides at heading seemed to benefit test weight at all locations except at the driest one. There were no consistent effects of foliar fungicide management on wheat grain protein concentration. This research is an initial step in determining the benefits of foliar fungicide to winter wheat yield and to date, a preliminary conclusion highlights the usefulness of a heading fungicide application when precipitation is not a limiting factor to yields, without consistent differences among the evaluated products