Optimum Preplant Nitrogen Rates for Sorghum (Sorghum bicolor).

Grain sorghum (Sorghum bicolor L.) production similar to Maize (Zea mays L.) needs to take place at a much higher level of nitrogen use efficiency (NUE) than is present today. In general, producers apply continuous flat rates of nitrogen (N) from one year to the next and often field to field. This study was initiated to determine the minimum pre-plant fertilizer N rates needed to improve mid-season fertilizer N use efficiencies, and determine periods of maximum N demand. Nitrogen application rates for both preplant and sidedress, need to be adjusted based on variables such as the environment, peak demand, and field to field variability which are known to change from one year to the next. Mid-season N management can help in reducing N loss from leaching, immobilization, and denitrification. These pathways have the potential to heighten ground water quality concerns and atmospheric contamination through the release of nitrous oxide (N₂O). This trial will analyze pre-plant N in conservation and conventional tillage cropping systems, and the influence of the environment on N response. These factors, in conjunction with the normalized difference vegetation index (NVDI), can assist producers in making better N management decisions.