Ideal Rate and Timing of Nitrogen Fertilizer in Grain Sorghum Based on Starter Fertilizers.

Nitrogen (N) management is critical for producing high yielding grain sorghum. Many producers utilize planter options for starter fertilizer application, including in furrow or 2x2 placements of N and phosphorus (P). N and P applied with starter fertilizers could affect optimum timing, rate and nitrogen use efficiency (NUE) of N fertilizer in grain sorghum. Existing recommendations advise all nitrogen fertilizer be applied near panicle initiation. Applying small amounts of N with starter solutions could extend optimum timing for applying side-dress N fertilizer. Also N and P in starter solutions could affect yield potential and affect optimum N rates for grain sorghum. Two separate field studies were established over two years in Burleson County, Texas to determine the optimum rate and timing of N fertilizer in sorghum with starter solutions applied at planting. In 2016 we found the optimum side-dress N rate to be 168 kg N ha 1, but it was not affected by starter fertilizer practices. The N and P starter solution with higher rates placed 2x2 increased grain yield compared to the other practices. Grain yields were not different when side dress N was applied up to the 10-leaf growth stage and the starter practices did not affect the optimum N side dress timing.