The objective of this project was to evaluate winter wheat grain yield and grain protein concentration responses to nitrogen (N) rate in the state of Kansas during the 2018-2019 growing season. Experiments evaluating the response of the wheat variety Zenda to four nitrogen rates (0, 50, 100, and 150 lb N/a) were established at four locations. In-season measurements included flag leaf N concentration, grain yield, yield components, and grain protein concentration. Flag leaf N concentration ranged from 2.4 to 4.1% across all environments and treatments, and increases in N rates increased flag leaf N concentration linearly. Grain yield ranged from 36.3 to 94.4 bu/a and increased with increases in N rate usually following quadratic relationships at all locations except for Belleville, where no response was observed, likely due to the high organic matter levels. Grain protein concentration ranged from 11 to 15% across all locations and treatments and increases in N rates increased grain protein concentration following a usually linear relationship; however, the quadratic yield response to N rate, coupled to the linear protein response to N rate, indicated that greater N rates might be needed to maximize protein as compared to maximizing yields. Both relative grain yield and relative grain protein concentration variables calculated relative to the maximum in each respective environment, were related to flag leaf N concentration in a linear-plateau way, suggesting that flag leaf N concentration could be used as a diagnostic tool for crop N status.
The objective of this project was to evaluate winter wheat stand count and grain yield responses to the interactions among seeding rate, seed cleaning, and seed treatment in the state of Kansas during the 2018-2019 growing season. Experiments evaluating the response of the wheat variety "SY Monument" to three seeding rates (600,000, 900,000, and 1,200,000 seeds per acre), three seed cleaning intensities (none, air screen, and gravity table), and two seed treatments (none and insecticide + fungicide) were established in a split-split plot design conducted in a complete factorial experiment at seven Kansas locations. In-season measurements included stand count, grain yield, grain test weight, and grain protein concentration, though this report only shows stand count and grain yield. Stand count increased with increases in seeding rate at all locations, with improvements in seed cleaning in five locations, and by seed treatment in one location. Grain yield increased with increases in seeding rate in five locations, with improvements in seed cleaning in four locations, and with seed treatment in one location. Significant interactions on grain yield occurred between seeding rate and seed cleaning (one location) and seeding rate and seed treatment (two locations), usually suggesting an advantage for seed cleaning or seed treatment at low seeding rates. The combined analysis across locations suggested that seeding rate and seed cleaning improved stand count (~140,000 and ~35,000 more plants established for each level of seeding rate and seed cleaning improvement) and grain yield (about 5 and 2 more bushels per acre for each improvement in seeding rate and seed cleaning, respectively). This research is an initial step in evaluating the value of the seed certification process; it does not compare certified seed versus bin-run seed. The seed used in this study derived from commercial seed production fields (i.e., high quality seed) and not from commercial grain production fields, which usually provide bin-run seed.
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.
Yield improvements to wheat can result both from variety selection and adoption of improved management practices. However, the yield response to improved management practices can be varietyspecific and can result in decreases in protein concentration. Our objectives were to evaluate the yield and protein responses of different commercial winter wheat varieties to increased nitrogen (N) rates and application of foliar fungicides. We conducted a trial combining 20 winter wheat varieties and two management level intensities. The standard management consisted of N applied for a 75 bushel per acre yield goal and no fungicide; and intensive management consisted of an additional 40 pounds of N per acre and two fungicide applications-the first at jointing and the second at flag leaf emergence. The study was conducted at two Kansas locations (Great Bend, following a terminated cover crop; and Ashland Bottoms, following a previous soybean crop) during the 2018-2019 growing season. Grain yield ranged from 18-103 bushels per acre, with greatest yields recorded in the intensive management treatment in Great Bend and the lowest yields recorded in the standard management treatment in Ashland Bottoms. While there were no statistical differences in the varieties' responses to intensive management, both the ranking of varieties and the yield increase from intensive management depended on location. Grain protein concentration ranged from 10.5-17.7% across all treatments, and the intensive management increased grain protein concentration from 12.7-13.9% in Ashland Bottoms and from 14.1-14.5% in Great Bend. The intensive management concomitantly increased grain yield and grain protein concentration at Ashland Bottoms, and increased grain yield while sustaining grain protein concentration at Great Bend, suggesting that total N removal in the grain increased with intensive management. While we did not investigate the net profits from the intensive management, these results suggest that intensifying management on wheat could add income from additional yield produced and protein premiums, as long as these are available.
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