Controlled-Release Urea Commingled with Rice Seeds Reduced Emission of Ammonia and Nitrous Oxide in Rice Paddy Soil

Reduction of ammonia (NH3) and nitrous oxide (N2O) emission and enhanced nitrogen (N) fertilizer use efficiency have been investigated with different N fertilizer management and application methods for irrigated rice production. Few studies have examined NH3 and N2O emissions from rice paddy soil when commingling controlled release urea with rice seeds. The objective of this study was to assess NH3 volatilization and N2O emission from a novel controlled-release urea formulation (CRU-180) when commingled at the full application rate with seeds in a single application during the preparation of plant plugs at the nursery stage. The experiment was conducted as a factorial design with two fertilizer sources (conventional urea and CRU-180), four rates (0, 100, 200, and 300 kg N ha(-1)), and three replicates. The entire amount of CRU-180 was incorporated into each plug with germinated seed. The conventional urea was split into four applications based on the standard practice for fertilizer application. The CRU-180 treatments reduced the NH4+ and NO3- concentration in the paddy flood water and paddy soil solution as compared with the conventional urea treatments. The percentage of applied N fertilizer emitted as NH3 volatilization and N2O emission in the CRU-180 treatments was only about 10% of that from the conventional urea treatments at the same N application rate. The application of CRU-180 with seeds offers a novel N fertilizer management technique, a method to reduce environmental impacts associated with rice production and the cost of rice production.