A study of slow-release N-carrters on rice

Abstract

A field experiment was carried out to monitor the relative efficiency of urea, urea formaldehyde (UF), sulphur coated urea (SCU) and isobutylidene diurea (IBDU) each at the rate of 40, 80 and 120 kg N/ha on growth, yield and chemical composition of rice grown during aman season. Application of nitrogen caused a significant increase in number of tillers, height and yields of straw and grain irrespective of the sources. Among the chemical composition (N, P, K, Ca and Mg) of straw and grain only N content was significantly improved. All these components increased with nitrogen rate. The effectiveness of the N-carriers in increasing the parameters followed the order: SCU> Urea> IB DU > UF. Percent recovery of added nitrogen generally decreased with increasing amount of nitrogen. SCU was found to be superior to conventional urea whereas IBDU and UF were inferior due to slow release of nitrogen. Anaerobic incubation of urea, UF, SCU and IBDU for 4 weeks caused a significant release of NH4-N from 59.9 to 78.2%. An initial rapid production of NH4-N was followed by a gradual release with time. More than 75% urea and SCU decomposed to NH4-N within 2 and 4 weeks respectively. UF was more resistant to decomposition as compared to SCU and IBDU. However, the trend of degradation was similar for all the compounds. Accumulation of a small quantity of NO3-N disappeared rapidly within 2 weeks time.