Agricultural soils are an important source of greenhouse gas nitrous oxide (N2O) emission. The comprehensive effects of nitrogen fertilizer management on N2O emission from paddy fields of India have not been evaluated under field conditions. A 2-year field study was conducted to evaluate the effect of different nitrogen fertilizers, namely, conventional fertilizer (NPK), starch-coated urea (SCU), neem-coated urea (NCU), and normal urea alone (NUA) on soil quality, grain yield, and N2O emission from rice field. Gas samples were collected from the field at weekly intervals by static chamber technique and analyzed in a gas chromatograph. During the crop-growing season, the application of NPK resulted in the highest cumulative N2O emission (2.49 kg N2O-N ha-1) followed by NUA (2.34 kg N2O-N ha-1), NCU (2.20 kg N2O-N ha-1), and SCU (1.97 kg N2O-N ha-1). As against the application of conventional fertilizer (NPK), the application of SCU and NCU reduced the total N2O emission by 21% and 12%, respectively (p < 0.05), during the rice-growing period. The results indicate a good correlation of N2O emissions with soil organic carbon, soil mineral nitrogen, and urease activity (p < 0.05) at different stages of crop growth. Application of SCU significantly increased the rice grain productivity by 12%, 10%, and 3% over NPK (control), NCU, and NUA respectively without affecting the soil quality and nutrient status. The use of SCU improved the nitrogen use efficiency (NUE) and was the effective substitute for conventional fertilizer in terms of reducing N2O emissions from tropical rice paddy.
Keywords: Nitrogen use efficiency; Nitrous oxide; Soil urease activity; Starch-coated urea.