[Effects of slow/controlled release urea on annual CH and NO emissions in paddy field].

Present study examined the influence of different types of slow/controlled release urea on rice yield and annual greenhouse gas emissions in a paddy field, and assessed the greenhouse gas intensity (GHGI, equivalent to global warming potential GWP/rice yield). The results indicated that the optimized fertilization (OPT) treatment recorded the similar yield with reduced nitrogen fertilizer (21.4%) supply compared with the farmers' fertilizer practice (FFP) treatment, and decreased the annual emissions of CH (12.6%) and NO (12.5%) during the rice season, and NO emission (33.3%) during the fallow period. Application of controlled release urea (CRU) reduced CH emission by 28.9% during the rice-growing season with respect to OPT treatment, and showed negligible CH emission during the fallow season. However, nitrification inhibitor (DMPP) treatment was found to reduce the CH emissions by 41.6% and 76.9%, and NO emissions by 85.7% and 6.5%, during the rice growing season and fallow season, respectively, compared with OPT treatment. In the fallow season, the NO emissions accounted for 76.8%-94.9% of annual NO emissions, which was clearly a key point for evaluation of greenhouse gas emissions in paddy. The average values of GHGI in OPT, CRU and DMPP treatments were 0.50, 0.41 and 0.33 kg·kg, respectively. Considering the benefits of higher rice yield and lower annual greenhouse gas emissions, combined application of urea and nitrification inhibitor could be the best combination in paddy fields.