Grain sorghum (Sorghum bicolor L. Moench) fails to consistently respond to N-fertilizer when grown on a Tunica clay soil in the lower Mississippi River Valley, USA

Abstract

Information on producing grain sorghum (Sorghum bicolor L. Moench) on clay soils found in the Mississippi Delta and similar regions is comparatively limited to what is known for the crop in other environments, especially regarding nitrogen fertility. A study conducted in 2014 and 2015 on a Tunica clay soil (clayey over loamy, montmorillonitic, non-acid, thermic, Vertic Halaquept) examined the effects of three N-fertilizer rates (0.0, 112.0, and 224.0 kg N ha^-1) on yield and yield components of six commercially available hybrids. The 2014 seeding did not require irrigation while three irrigations were applied in 2015. No yield differences in hybrids or N-fertility treatments were observed in 2014 likely due to waterlogged soil, resulting in denitrification, but added N did increase yields in 2015. No consistent differences in yield or yield components occurred between hybrids either year. Yields in 2014 and at 0.0 or 112.0 kg ha^-1 added N-fertilizer in 2015 were sub-standard to regional variety trial data. Rates of N-fertilizer of at least 224.0 kg N ha^-1 appear necessary for grain sorghum grown on clay soils in the humid sub-tropics.