Effects of Organic Manure Application Combined with Chemical Fertilizers on Nutrients Absorption and Yield of Rice in Hunan of China

【Objective】To evaluate the effect of organic manure application on rice yield and soil fertility synthetically in double-rice cropping region in south China. 【Method】 Successive 6-year field experiments were conducted under quaternary red clay conditions in south Hunan of China. Four different treatments with mixed chemical and organic fertilizers, no nitrogen with chemical P and K (PK), swine manure only (M), N, P and K chemical fertilizers only (NPK; urea as N), and half chemical fertilizers, half swine manure (NPKM) with four replications were examined. Each N, P and K application rate was the same at all the treatments (except the N application rate at PK). All fertilizers applied to soil with once application as base fertilizers. The nutrients uptake rate, grain yield, nitrogen use efficiency and soil organic matter content at each treatment were measured/calculated for comparison. 【Result】 During the six years plantation, the NPKM treatment achieved a 12.2 t·ha-1 mean annual yield, (68% higher yield than that of PK). Higher dry matter accumulation and nutrients absorption were observed during the middle-later growth period in the NPKM treatment, with higher panicle number per unit and filled-grain number per panicle. Its average nitrogen use efficiency was 36.3% and soil organic matter increased by 18.5% during the five-year plantation in the NPKM, which were significantly higher than those in the NPK. 【Conclusion】 Organic manure application with chemical fertilizers increased the yield and nitrogen use efficiency of rice, reduced the risk of environmental pollution and improved soil fertility significantly. It could be said that this is a good practical technique that protects the environment of south China with keeping or raising the rice yield in this region.