Soil organic matter can supply a crop with large amounts of nitrogen (N) through a process called N mineralization, which converts N into a plant available form. This can reduce the amount of chemical fertilizer needed to be applied to a crop, however, this portion of N is difficult to accurately predict. Research conducted in Pennsylvania by Dr. Charles White has led to a new N rate recommendation tool for corn that predicts N mineralization and integrates it into N recommendations. This tool adds a component for N available from a cover crop, as cover crops have become more widely adopted. The tool was designed to use soil and cover crop measurements that are accessible to farmers and their nutrient management planners. It uses soil texture, soil organic matter, cover crop biomass and its Carbon to Nitrogen ratio, and corn prices to determine the economic optimum N rate.
Since this tool accounts for N mineralization, the goal is to allow producers to apply less N while still maintaining economic optimum yields. As this tool was calibrated in Pennsylvania, it is currently only useful for Pennsylvania producers. Recent research conducted in Virginia has shown that this tool shows potential for future use in Virginia; however, further calibration and fine-tuning will be needed before it is used to make widespread N fertilizer recommendations here. While no N mineralization prediction tool is currently available in Virginia, recent updates were made to Pre-Sidedress Nitrate Test recommendations to account for N supplied by cover crops.
Penn State N rate recommendation tool: https://extension.psu.edu/graphical-analysis-tool
Virginia Tech N mineralization research: https://vtechworks.lib.vt.edu/handle/10919/115653
Virginia Tech PSNT recommendations: https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/418/418-016/SPES-484.pdf
Further information on how the Penn State N rate recommendation tool was developed: https://acsess.onlinelibrary.wiley.com/doi/full/10.1002/agj2.20474