By Teshome Regassa and Madhav Bhatta
Fine-tuning wheat production practices, such as seeding rate and nitrogen application timing, and selecting a mix of varieties for a location could significantly improve yield and end-use quality of winter wheat in Nebraska, based on results of University of Nebraska research.
Studies conducted on rain-fed wheat at the Agronomy Research Farm (ARF) near Lincoln and at the High Plains Agricultural Laboratory (HPAL) near Sidney in 2014 and 2015 found that increasing wheat seeding rate up to twice the local recommended rate and applying N fertilizer in season at the flag-leaf stage increased grain yield and net return, and improved multiple grain quality parameters of six widely grown Nebraska wheat varieties.
The research was conducted in 2013-14 and 2014-15 to determine the effects of three seeding rates, and flag-leaf top-dressed N on the yield and end-use quality of six widely grown winter wheat varieties in Nebraska. The six winter wheat varieties — Freeman, Millennium, Overland, Pronghorn, Robidoux and Settler CL — were tested at half, standard and twice the recommended seeding rates for each site. The standard seeding rates are 60 pounds (1.02 million seeds) per acre at the ARF and 44 pounds (753,000 seeds) per acre at HPAL. ARF plots were planted in October with 30, 60, or 120 pounds (510,000; 1.02 million; or 2.04 million seeds) per acre. Plots at HPAL were planted in September with 22, 44, or 88 pounds (376,000; 753,000; or 1.50 million seeds) per acre. Moreover, half of the research plots received only 50 pounds per acre of nitrogen applied at planting (current recommendation); the other half received an additional 30 pounds per acre of nitrogen top-dressed at the flag leaf stage.
It is vital to mention that the stage of growth when N was applied is not the key point; rather, it is applying N when plants need it most (during late stem elongation) so as to effect increased canopy area and possibly extend the flag leaf area. Flag leaf area is known to significantly affect wheat grain fill and the length of the grain-filling period.
Doubling wheat seeding rate
Grain yield increased with increased seeding rates during both years at both test locations. In 2014, doubling the seeding rate increased grain yield by 5% at ARF and 9% at HPAL. Estimated net return increases in 2014 were, respectively, $7 per acre at ARF and $33 per acre at HPAL. In 2015, doubling the seeding rate increased grain yield 13% at ARF; the net return increase was $8 per acre. Doubling the seeding rate at HPAL in 2015 did not result in increased yield, but did result in a net loss of $4 per acre. This loss is attributed to an unusually high leaf disease severity at HPAL that resulted in almost a 50% drop in yield.
Effect of seeding rate and environment on grain yield in 2014 and 2015 at the University of Nebraska High Plains Research Lab near Sidney (left) and the Agronomy Research Farm near Lincoln (right).
Reducing the seeding rate below the current recommendation resulted in decreased grain yield and a loss of net returns at both locations and years.
Applying in-season N fertilizer
Applying N fertilizer at the flag leaf stage increased grain yield and improved end-use quality characteristics of the grain.
In 2014 wheat yield increased by 9% both at the ARF and HPAL. The value of this increase to net returns was estimated to be $41 per acre at the ARF and $39 at HPAL. In 2015, yields were reduced significantly due to severe disease incidence at both sites, irrespective of whether in-season N was applied at the flag leaf stage.
Grain protein dropped in response to applying N at the flag leaf stage, contrary to researcher expectations; however, most baking quality characteristics were improved.
Regassa is a research assistant professor, and Bhatta is an agronomy graduate research assistant. This report comes from UNL CropWatch.