Grain Sorghum Fails to Consistently Respond to N-Fertilizer When Grown on a Tunica Clay Soil.

Nitrogen fertilization of grain sorghum (Sorghum bicolor L. Moench) on clay soils in the Mississippi Delta and similar environments has not been extensively researched.  Six hybrids grown with 0.0, 112.0, and 224.0 kg N ha^-1 added fertilizer on a Tunica clay soil (clayey over loamy, montmorillonitic, non-acid, thermic, Vertic Halaquept) in 2014 and 2015 were evaluated for yield and yield components. The 2014 seeding did not require irrigation while three irrigations were applied in 2015. No yield differences occurred between N-treatments in 2014 but added N did increase yields in 2015.  No consistent differences in yield or yield components occurred between hybrids.  Yields were sub-standard to regional variety trial data probably due in part to the water and nutrient availability inherent to the clay soil.  Rates of N-fertilizer at 112.0 kg N ha^-1 probably will benefit grain sorghum yields from clay soils most years but higher levels most likely are not necessary.