Evaluation of Nitrogen‐Loss Prevention Amendments in Maize and Wheat in North Carolina

CORE IDEAS: Fertilizer additives to decrease N losses did not provide consistent yield advantages. Plots treated with N‐loss products did not increase N use efficiency or N uptake. Agronomic optimum N rates observed in the field aligned with North Carolina recommendations. 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 mountains) 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.