Nitrogen Management in Corn: Influences of Urea Ammonium Nitrate (UAN) Applications with and without Nitrogen Stabilizer Products.

Corn (Zea maize, L.) is a major crop produced in the nutrient sensitive Mid-Atlantic region.  Nitrogen (N) use efficiency for corn is considered sub-optimal; it has been estimated by various investigators to range between 30 and 60%.  Urea Ammonium Nitrate (UAN) is the most commonly used nitrogen fertilizer source in the state of Maryland.  Corn farmers in the region use a number of best management practices (BMPs) to improve the use efficiency of applied synthetic Nitrogen fertilizer.  One of those practices is to sidedress N just prior to rapid corn growth (V5-V8 growth stages).   The United States Environmental Protection Agency (EPA) established and is in the process of implementing Total Maximum Daily Loads (TMDL’s) for nitrogen, phosphorus, and sediment. The region’s state agriculture departments are proposing regulations that will bring them into compliance with the TMDL’s.  Farmers are searching for ways to comply with the proposed regulations for N loading in their region, while remaining profitable.

Nitrogen loss occurs through three major loss pathways; nitrification, denitrification, and volatilization.  In 2008, a field study was started to evaluate two N fertilizer application methods and four commercially available nitrogen stabilizer products in corn production. In addition, each application method and stabilizer product was applied at three N rates (160 lb N a^-1, 120 lb N a^-1, and 80 lb N a^-1) to assess if rate reduction in combination with a stabilizer product can manage N while optimizing yield and profitability. Dependent variables evaluated include soil nitrogen both pre–plant and post-harvest to a 2’ depth, ammonia volatilization loss utilizing gas collection chambers, in season soil urea concentrations to a 1’ depth which coincided with the ammonia loss sampling dates, total plant nitrogen, and grain yield. A review of the data over four years will be presented.