Effects on NPK Status, Growth, Dry Matter and Yield of Rice ( Oryza sativa ) by Organic Fertilizers Applied in Field Condition

The decline in rice yields as a result of excessive chemical fertilizer (CF) inputs is a matter of great concern in rice-growing regions of Asia. In two-year’s field experiments, the nitrogen, phosphorus, and potassium (NPK) status, growth characteristics and yield of rice were examined by application of poultry manure (PM), cow manure (CM) and compost (CP). Organic fertilizers were applied as EMN (estimated mineralizable N) based on their total N content. Six treatments were assigned in a randomized complete block design: (1) no-N fertilizer (N 0 ); (2) 50% CF (CF 50 ), (3) 100% CF (CF 100 ); 50% CF + 50% EMN from (4) PM or (5) CM or (6) CP. Compared with CF 100 , the CF 50 PM 50 (total N ≥ 4%) accumulated higher N, P and K content in leaf, sheath, panicle and seeds, resulting in greater growth and yield. The CF 50 PM 50 increased yield by 8.69% and 9.70%, dry matter by 4.76% and 5.27% over CF 100 in both years. The continuous application of CF 50 CM 50 (total N < 4%) and CF 50 CP 50 (total N < 4%) treatments led to similar NPK contents but higher yields than those of CF 100 treatment in 2018. In conclusion, the organic fertilizer (total N ≥ 4%) with the EMN method enhances higher N availability in each year. Continuous application of organic fertilizer (total N < 4%) over two years effectively increased N availability in the second year. The 50% organic fertilizer (total N ≥ 4%) and 50% CF led to increased NPK availability and rice yields over the 100% CF treatment, reducing CF usage and leading for sustainable agriculture.