Nitrogen is applied to crops usually in one of two forms: ammonium or nitrate. Ammonium is the majority form, with common fertilizer sources of nitrogen. With manure, the form will generally be organic nitrogen or
ammonium depending on the livestock species and the conditions under which the manure was stored. Ammonium nitrogen is able to attach to the soil colloids and be stabilized, but it is in high demand by soil organisms that
convert ammonium to nitrate forms (nitrification). At the end of the growing season, nitrate will be the dominate soil nitrogen form. Nitrates are not soilstable. Nitrates will leach with rainfall or denitrify if saturated soil conditions exist. Nitrogen left over at the end of the crop season is lost, and those losses occur primarily through field tile.
- If using organic nitrogen sources, refer to the “Nitrogen: Evaluate Rate to Account for Organic and Inorganic Nitrogen Sources Applied” chapter of this publication.
- Time nitrogen applications close to crop need.
- Use a maximum return to nitrogen rate of nitrogen as a starting point to determine the nitrogen need for corn. If wheat, use the yield goal rate from the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa as a starting point. Use appropriate recommendations for other crops.
- During the growing season, account for all applications of nitrogen, such as starter or pre-emergence application of commercial fertilizer or previous manure applications. Do not exceed the total recommended rate when accounting for all nitrogen sources applied.
- Use drainage water management structures or other practices that either reduce the amount of water leaving the field or treat the water to reduce nitrogen concentration.
- If residual nitrogen is expected due to low crop yields, use cover crops to retain the nitrogen in the field.
Best Management Practices