Dicyandiamide as a nitrification inhibitor in crop production in the Southeastern USA

Abstract

The yield response to N with and without the use of the nitrification inhibitor, dicyandiamide (DCD), was determined on the field crops, sweet corn, cotton, wheat, and grain sorghum; and on the vegetable crops, bell peppers, potato, and tomato, on a large number of different soils in Alabama, Florida, Kentucky, Mississippi, and Virginia. In general, DCD inhibited nitrification for several weeks but inhibiting nitrate formation was not often reflected in crop yield response to N. Increase in yield resulting from DCD use were found for sweet corn in Florida, grain sorghum in Alabama, and potato in one of two years in Florida. Results with cotton were erratic, sometimes resulting in increased, sometimes in decreased, yields. Use of DCD for wheat production in the Southeast did not prove to be advantageous. Generally when DCD use benefitted yields, this occurred at the lower N rates, indicating that preventing loss of N at the lower end of the response curve resulted in a measurable positive effect. The studies reported indicate that consistent benefit from DCD use in the southeastern United States is unlikely.