Evaluation of nitrogen-loss prevention amendments in maize and wheat in North Carolina

Abstract

To reduce environmental losses of N and increase crop use, it is critical to optimize N fertilization rates and determine if N-loss prevention amendments increase yields. Research objectives were to: (i) determine N-release patterns of three N-loss amendments (urea ammonium nitrate [UAN] treated with NBPT+DCD, nitrapyrin, or an organo-Ca) and UAN through a laboratory incubation; (ii) determine effectiveness of these four products for maize (Zea mays L.) and winter wheat (Triticum aestivum L.) produced in two to three regions of North Carolina; and (iii) determine agronomic optimum N rate for wheat and corn compared to state-recommended rates. Nitrogen release was measured in three soils (coastal plain, piedmont, and moun-tains) during the incubation experiment. Field experiments were randomized complete block designs (four replications of six maize N rates and five wheat N rates), with each rate applied as one of four product treatments (UAN and UAN+ one of three N-loss prevention amendments). In the incubation experiment, soils treated with UAN+nitrapyrin or UAN+NBPT+DCD delayed nitrification longer than soils treated with UAN or UAN+organo-Ca. There was no significant effect of product on maize grain yield (coastal plain and mountains) and wheat yield (coastal plain and piedmont). A year × product interaction occurred for maize grain yield in the piedmont. Agronomic optimum N rates mostly aligned with current North Carolina N fertilizer recommendations. Despite positive laboratory results, N-loss amendments did not have a significant effect on yield in 9 of 10 site-years, indicating that proper N rates are a more effective nutrient management strategy.