Effects of Organic-Manure Application on Growth, Grain Yield, and Nitrogen, Phosphorus, and Potassium Recoveries of Rice Variety Manawthuka in Paddy Soils of Differing Fertility

A 2-year pot experiment (2005–2006) was conducted in a greenhouse using rice variety Manawthuka on high-fertility Kasuya soil and low-fertility Futsukaichi soil. Fermented cow manure (CM) and poultry manure (PM) were applied as organic nitrogen (N) sources. In every manure application, 20 kg urea ha–1 was also applied at basal. Dry matter, grain yield, and nitrogen uptake were greater in PM than CM and significantly greater in Kasuya soil. In 2006, they increased in Futsukaichi soil but decreased in Kasuya soil. Apparent nitrogen recovery was greater in PM than in CM and increased in both soils in 2006 because of residual benefits from manure application. The apparent phosphorus recovery was greater in CM than in PM; however, large plant phosphorus accumulation was observed in PM. In both soils, the efficiency of CM is very low, and CM-only application is unlikely to achieve an optimal rice yield in the short term.