Effect of Different Methods and Timing of Nitrogen (N) Application on Sorghum (Sorghum bicolor L) Grain Yield

Sorghum (Sorghum bicolor) is rapidly becoming a needed crop due to its drought tolerance. High production levels of this crop could assist in fulfilling the intense growing food demands. This study was conducted to determine the effect of different methods and timing of nitrogen (N) application on sorghum grain yield. Data was collected in 2018 at two locations in Oklahoma. Urea was used as the N source where three different rates (0, 30, 60 kg N ha-1) were applied either as a pre-plant application, a side-dress application, or both. Three different N application methods (broadcast, dribble surface band, and the OSU hand planter) were used in this study to see if they had an effect on grain yields. Normalized difference vegetation index (NDVI) readings were taken biweekly throughout the growing season. When no N or low rates were applied with the seed, a loss in yields were recorded. This loss could have different causes, from soil fertility issues to the abnormal amount of rainfall, or other environmental issues beyond human control. When comparing applied N with the seed to a surface pre-plant and midseason application, a distinct advantage was present for applying N in split applications. This work showed that as much as 30 kg N ha-1 can be applied in-furrow with the sorghum seed without significant yield reductions.