Integrating organic amendments and enhanced efficiency fertilizers for sustainable rice production——A case study in a tropic paddy system

Abstract

Rice production is critical for food security, yet China's paddy fields face declining soil quality and grain quality despite increased yields. Organic amendments and enhanced efficiency fertilizers (EEFs) can improve soil organic matter (SOM) and nutrient use efficiency, but their optimal combination for rice production is unclear. Through three seasons field experiments, this study explores the effects of integrating organic amendments, EEFs, and 4R nitrogen (N) management stewardship (Right rate, time, source, and place) on enhancing rice grain attributes, N use efficiency (NUE) and soil quality in tropical paddy system. It compared one conventional practice with seven ‘4Rplus’ treatments (4 R concept combined with EEFs and organic amendments), reducing N application from 180 kg N ha⁻¹ (conventional) to 140 kg N ha⁻¹. Results showed that 20 % and 40 % organic N substitution increased rice yield by 4 % and 5 %, respectively, under reduced N application, while a 60 % substitution decreased yield by 3 %. As the proportion of organic substitutes increased, the content of mineral nutrients such as magnesium, zinc, and iron increased, and the amino acid structure is improved. The 40 % organic substitution combined with controlled release fertilizer (40MC) treatment achieved the best performance on improving grain quality, with lower amylose content (16.3 %) and crude protein content (65.2 mg g⁻¹), higher head rice rate (64.2 %), and lower chalkiness (1.4 %). Controlled release fertilizer (CRF) was more effective than inhibitor-based EEFs in improving rice yields, quality and NUE. The 40MC treatment reduced N surplus to 60 kg N ha⁻¹ and achieved a NUE of 57 %. Inhibitor-based treatments (urease inhibitor and nitrification inhibitor) averaged an N surplus of 75 kg N ha⁻¹ with NUE of 46 %, with no significant differences in grain quality between inhibitors. Supplementing 40MC with amino acid powder further increased yield by 10 % and NUE to 60 %, while biochar application did not improve rice quality or yield but significantly enhanced soil fertility. These findings highlight that integrating organic amendments with EEFs is a promising strategy for achieving sustainable production in tropical paddy systems, synergistically enhancing rice yield, quality, and soil fertility while improving NUE and minimizing N losses.