Effect of Enhanced Efficiency N Fertilizers and Additives On Leaf N Concentration and Biomass N Content of Grain Sorghum.

Grain sorghum is widely grown in Texas and ranks the second most important crop grown for feed and bio-fuel feedstock in the United States.  Finding ways to improve the management of input costs of N fertilizer is critical for maintaining the economic viability of sorghum production when costs of conventional N sources remain high.  Properly managed, slow-release N fertilizers have the potential to enhance plant recovery, thus improving N use efficiency in grain sorghum and reducing N losses to water resources.  Field studies were initiated in the Central Texas Blackland Region with moderate residual N level as determined by soil sampling to 1.22 m.  Fertility treatments included a control or 0 N added, 34, 67, 101, and 134 kg of N per ha added using liquid urea ammonium nitrate (UAN) alone or in combination with a urease-nitrification inhibitor product surface and subsurface-band applied at planting to stage two.  Additional treatments included the application of 34, 67, and 101 kg per ha of granular urea and two slow-release N sources surface-band applied at planting to stage two.  Experimental units were arranged in a randomized complete block design and replicated five times.  Measurements of fully-expanded leaf N concentration at flowering and total N uptake in biomass and grain at grain maturity were collected during the season.  Grain yield, test weight and moisture were assessed at final harvest.