Abstract:To evaluate the applying effects of milk vetch and different organic materials on soil amelioration and chemical fertilizer decrement, a 11-year fertilization experiment was conducted since 2009 in thered paddy field in Fuzhou City, Fujian Province. Six fertilization treatments were designed, including T0(CK, without fertilization), T1(chemical fertilizer), T2 (milk vetch alone), T3(milk vetch combining straw), T4(milk vetch combining cow dung) and T5(milk vetch combining straw plus 40% chemical fertilizer). The effects of different fertilization on soil nutrients, rice yield, nutritional quality and soil fertility were investigated. The results showed that compared with CK, rice grain and straw yields in fertilization were significantly increased by 11.4%-21.0% and 17.1%-40.2% respectively, especially for the T5, which were significantly increased by 3.4% and 6.6% respectively compared with T1. Effective panicle was an important character factor responsible for yield variation. In addition, compared with CK at mature stage, fertilization increased N, P and K uptake by 14.3%-30.6%, 8.9%-32.7% and 2.9%-47.2% respectively in rice aboveground plants. The highest absorption of N and P were found in T4, and the highest absorption of K was in T5. Total and essential amino acid contents in rice grains under fertilization in the 10th year were increased by 11.5%-20.6% and 11.1%-19.8% respectively, compared with CK. Furthermore, compared with T1, essential and total amino acid contents in T5 were significantly increased by 5.7% and 6.5% respectively. Meanwhile, soil fertility was improved by applying different organic matters, especially for T5, compared with T1, soil microbial biomass carbon (SMBC) and nitrogen (SMBN) concentrations in T5 at the peak of tillering stage were significantly increased by 15.2% and 42.3% respectively. Additionally, soil organic matter and total nitrogen contents at mature stage were increased by 9.7%-16.7% and 10.9%-14.8% respectively in organic treatments compared with T1, and T5 with the highest increment. In addition, available potassium contents in T4 and T5 were significantly higher than that of T1. Correlation analysis revealed that the contents of soil organic matter, total nitrogen, available potassium, SMBC and SMBN were significantly positively correlated with rice yield, total and essential amino acid contents, respectively. In conclusion, continuous return of milk vetch and organic materials could ameliorate soil properties, increase nutrient uptake and rice yield. For 11 consecutive years, the combination of Chinese milk vetch and straw or cow dung could replace chemical fertilizer application in yellow-mud paddy field, T5 was the best fertilization in increasing rice yield and amino acid quality of rice grains as well as soil fertility. Soil organic matter, total nitrogen, available potassium, SMBC and SMBN are important fertility factors affecting rice yield and amino acid of rice grains.