Mechanical Deep Placement of Fertilizer in Puddled Soils

Evaluation of Nitrogen Losses and Yield of Transplanted and Direct-Seeded Rice

Abstract

To determine parameters for effective mechanical placement of nitrogen (N) into puddled soil, a study on deep placement devices for prill, briquette, and liquid N was conducted with transplanted and direct-seeded rice. Results showed that placement of any N material with simultaneous soil cover was effective in minimizing floodwater ammoniacal-N losses and ammonia volatilization. Deep placement in transplanted rice at 40-60% less N rate outyielded and doubled the N use efficiency of split broadcast. In direct-seeded rice, agronomic performances of deep placement and split broadcast were similar. Despite of metering performance problems, deep placement showed pronounced effects on rice yield and N use efficiency. Based on these results, an improved system of mechanical deep placement for wetland rice is recommended.