Grain Sorghum Yield Response to Slow-Release Nitrogen Fertilizers and Additives.

Ongoing volatility in the fertilizer market place accentuates the need for careful management of nitrogen (N) fertility for grain sorghum production.  Growing concern regarding nutrient contamination of surface and groundwater resources has refocused attention on N management in grain sorghum and other crops.  Properly managed, slow-release N fertilizers have the potential to improve N use efficiency in grain sorghum and thus reduce 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 48 inches.  Fertility treatments included a control or 0 N added, 30, 60, and 90 pounds of N per acre 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 30, 60, and 90 pounds of granular urea and two slow-release N sources per acre surface-band applied at planting to stage two.  Experimental units were arranged in a randomized complete block design and replicated five times.  Measurements of total N uptake in biomass and grain were collected during the season.  Grain yield, test weight and moisture were collected at harvest.