LAUSR

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 (N0); (2) 50% CF (CF50), (3) 100% CF (CF100); 50% CF + 50% EMN from (4) PM or (5) CM or (6) CP. Compared with CF100, the CF50PM50 (total N ≥ 4%) accumulated higher N, P and K content in leaf, sheath, panicle and seeds, resulting in greater growth and yield. The CF50PM50 increased yield by 8.69% and 9.70%, dry matter by 4.76% and 5.27% over CF100 in both years. The continuous application of CF50CM50 (total N < 4%) and CF50CP50 (total N < 4%) treatments led to similar NPK contents but higher yields than those of CF100 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.