The impact of DCD and NBPT concentration on nitrification and volatilization

Abstract

Nitrification inhibitors are used in agriculture to slow the conversion of ammonium to nitrate by inhibiting ammonia monoxygenace (AMO), which is found within the Nitrosomonas bacteria. There are two ways to inhibit nitrification of the AMO enzyme, namely, (a) competitive inhibition: The inhibitor will compete to occupy AMO's active site; by blocking the active site, it slows the conversion of ammonium to nitrate preventing loss of nitrates, and, (b) non-competitive inhibition: The inhibitor can temporarily inactivate the AMO enzyme by altering the active site. Dicyandiamide (DCD) is a competitive inhibitor. The amount of DCD delivered by a product has a direct impact on how well a product will inhibit loss of nitrogen through nitrification. Research shows the concentration of DCD in the soil has a direct influence on the percent of nitrification. Higher concentrations of DCD equate to higher percentage of nitrification inhibition. The results of a two-year program that compares two products, one containing 8500 ppm and one 870ppm of DCD and approximately equal concentration of a volatilization inhibitor will be presented.