Nitrogn release pattern of urea and coated nitrogen fertilizers in soils

摘要

Mineralization of prilled urea, (PU) lac-coated urea (LCU) and sulphur-coated urea (SCU) was studied in these soils - Hapludalfs, Paleudalfs and Udifluvents under two soil moisture regimes viz, saturated and 1:2 soil water ratio. The hydrolysis of urea was completed in case of PU and LCU in 4 days after their application. In case of SCU, the granules contained 19.34% urea-N even after 56 days period. The hydrolysis of urea from LCU was significantly higher in 1:2 soil water ratio than in saturated condition but reverse was true for SCU, which behaved like PU after 48 hours in releasing urea-N and accumulating NH_4-N. The NH_4-N in PU and LCU remained significantly higher upto 28 days and later on lower as compared to SCU, the NH_4-N increased significantly with decrease in pH from 4 to 28 days and vice versa later on. The NO_3-N formation started after seven days. The NO_3-N was lower at pH 5.3 and 6.3 than at pH 7.3 upto 14 days. Later on, the NO_3-N at pH 5.3 was higher than that at pH 6.3 and 7.3.