The influence of nitrification inhibitors and slow release nitrogen materials on transformations of fertilizer nitrogen in soils of fluctuating moisture content

A laboratory study was made of nitrogen transformations in a sandy clay loam given either urea with and without nitrification inhibitors or slow-release nitrogen fertilizers. Moisture conditions were field capacity, continuous flooding, and alternate flooding and drying. Urea nitrogen was mineralized and fairly well conserved in soil either at field capacity or under continous flooding, but was rapidly lost under alternate flooding and drying. Denitrification losses were reduced with nitrification inhibitors. Oxamide, isobutylidene diurea, and sulfur-coated urea were as effective as the inhibitors in reducing losses under alternate flooding and drying.