Yield of inbred rice and hybrid rice and soil nutrient balance under long-term fertilization

Two long-term NPK experiments were conducted in Jinhua Institute of Agricultural Sciences and Shimen Farm,Zhejiang province of China,separately.Six levels of fertilization and two cultivars were set up in both experiments.The results indicated that grain yield of rice significantly related with soil nutrient supplying capacity and nutrient uptake rate of rice.Soil nutrients status became poorer in the plots with manurial deficiency,while in the other treatments,accumulated N and P were observed.Under consecutive rice cropping,the rate of nutrient depletion in manorial deficiency plots depended on soil nutrient status before experiments and rice varieties cultivated.N and P balance were positive in all fertilization treatments except the treatments with manuurial deficiency,which were negative.Means of total grain yield and nutrient uptake(NPK) of hybrid rice were increased by 10.8%,5.2%,8.8% and 12.8 %,respectively,compared with inbred rice.Hybrid rice also had higher nutrient uptake capacity.Thus,the medium-and long-term effect of soil nutrient status before cropping and rice variety cultivated on soil nutrient balance should be fully considered in nutrient management for irrigated rice.