Managing Corn Sidedress Applications of Urea Ammonia Nitrate (UAN) with Nitrogen Stabilizers.

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%.   Corn farmers in the region use a number of best management practices (BMPs) to improve the use efficiency of applied fertilizer N.  One of those practices is to sidedress apply N just prior to rapid corn growth (V5-V8 growth stages).  However, even with the use of current BMPs to manage N, the United States Environmental Protection Agency (EPA) is planning to ratchet up the level of regulation for crop N use within the Chesapeake Bay region through establishment and implementation of Total Maximum Daily Loads (TMDLs) for the nutrient.  This has created the need to identify additional BMPs to help corn farmers comply with proposed TMDLs while producing corn profitably.  Nitrogen stabilizers are commercial products that are promoted to slow N loss through three major loss pathways; nitrification, denitrification, and volatilization.   A study was started in 2008 to evaluate N fertilizer application methods (all N pre-plant; sidedress N injected; sidedress N dribbled on soil surface) and four commercially available nitrogen stabilizer products (Agrotain International’s urease inhibitor, `Agrotain’ [NBPT]; Dow AgroScience’s nitrification inhibitor, `Instinct’ [nitrapyrin];  Agrotain International’s urease and nitrification inhibitor, `Agrotain Plus’ [NBPT and DCD ]; and Specialty Fertilizer Product’s urease and nitrification inhibitor, `Nutrisphere-N’ [maleic-itaconic co-polymer]). In addition, each of the application method/stabilizer product combinations has 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 stabilizer product use can optimize yield and profitability.   A summarization of corn yield and post-sidedress ammonia volatilization data will be presented.