Abstract: To address the issues of unstable crop yields, low fertilizer utilization efficiency, and environmental pollution caused by blind fertilization in double-cropping rice cultivation, a nutrient expert system based on yield response and agronomic efficiency was employed to conduct a 3-year multi-site field verification experiment across five counties in Jiangxi Province from 2023 to 2025. Four treatments were arranged including local farmers’ conventional fertilization practice (FP), soil testing-based formula fertilization (ST), rice nutrient expert system recommended fertilization (NE), and NE with 20% of chemical nitrogen replaced by organic fertilizer (NE_20%M). The results showed that compared with FP, NE reduced N, P₂O₅ and K₂O application rates by 15.0%, 50.0% and 52.5% on average, raised corresponding fertilizer use efficiency by 15.4, 10.8 and 49.5 percentage points, and increased grain yield by 3.2% and net profit by 3010 CNY per hectare. Compared with ST, NE decreased N, P₂O₅ and K₂O inputs by 7.0%, 37.8% and 44.7%, improved fertilizer use efficiency by 8.2, 8.5 and 43.7 percentage points, slightly decreased grain yield by 2.3%, while lifting net profit by 374 CNY per hectare. Despite higher fertilizer costs under NE_20%M, its net profit was 5946 CNY per hectare higher than that of sole NE. NE significantly elevated the contents of protein and free amino acids in rice grain, whereas its effects on amylose and reducing sugar were cultivar-dependent, with further improved grain quality under organic manure amendment. In conclusion, NE-based fertilization achieves fertilizer reduction, stable yield, improved grain quality and economic benefit, which is suitable for popularization in double-cropping rice regions of Jiangxi Province.