Effect of Residual Soil Nitrogen Management on Partitioning of Nitrogen in Wheat.

Maintaining adequate nitrogen (N) resources is integral to grain and forage yield, seed quality, pest management and maturity of wheat.  One strategy growers can use to address the numerous challenges of managing N is to credit residual or carryover N in the soil profile at the beginning of the wheat production season whether the end goal be grain, forage production or both.  Roots of winter wheat have been shown to surpass a depth of 1 m in previous studies and more recent data collected in Texas indicated that crediting N based on carryover amounts of N in the soil profile to 0.3 m results in improved N use efficiency and net return.  However, more information is needed about what effect N crediting may have on the partitioning of N and dry matter in above-ground stover and seed of wheat.  Field studies were initiated in the fall of 2015 and 2016 in the Central Texas Blackland to assess the response of wheat grain yield, seed quality (test weight and protein), and total N content in stover to residual soil nitrate-N to 0.6 m.  Two weeks before planting, deep profile sampling was used to identify amounts of residual soil nitrate-N to soil depth.  At Feekes stage five, supplemental N was top-dress applied  to achieve a representative yield goal and soil test recommendations based on residual nitrogen at 0 to 0.15-, 0 to 0.3-, and 0 to 0.6- m.  Experimental units were arranged in a randomized complete block design and replicated four times.  A summary of the results related to partitioning of N content and dry matter in above-ground biomass collected at final harvest will be presented.