Studies on the Mineralization of Urea, Coated Urea, and Nitrification Inhibitor Treated Urea in Soil

Summary A laboratory incubation study was conducted with a sandy clay loam soil (pH 7.8) at New Delhi to study the mineralization of urea, coated urea (sulphur‐coated urea, shellac‐coated urea), and urea treated with nitrification inhibitors (N‐Serve, sulphathiazole) a general purpose microbicide (coal tar), and neem (a non edible oil‐seed) cake. Coated fertilizers mineralized much slower than urea; urea‐N from these materials remaining in soil after z weeks of incubation being two to three times that from untreated urea. However, most N from coated fertilizers was mineralized after 4 weeks. Nitrification inhibitors were quite effective in retarding the nitrification of urea; N‐serve being much more effective than sulphathiazole. Neem cake and coal tar extract were less effective than sulphathiazole in controlling nitrification of urea but they did retard the nitrification of urea for z weeks.