Study on nutrient supplying capacity of purple soil under long-term rice-wheat rotation

The N, P and K natural supplying capacities of purple soil and the basic productivity of purple soil and their varieties were studied with 10 years long-term fertilization experiment in the wheat-rice rotation system. The results of the experiment indicated that the contribution of the natural productivity of purple soil for the yields of wheat and rice were in 51% and 61%, respectively. The contributions of chemical fertilizers for the yield increases of rice and wheat were in 39% and 49%, respectively. The natural nutrient supplying capacities of purple soil to wheat were in 60% for N, 70% for P and 91% for K, and to rice were in 70% for N, 90% for P and 92% for K, respectively. The amount of nutrient demand in wheat was higher than that in rice. The average natural supplying amounts of N, P and K from purple soil with 10-year long-term experiment were 37.1, 5.4 and 46.0kg/(hm2·a) in wheat seasons, and were 81.8, 13.6 and 103.0 kg/(hm2·a) in rice seasons, respectively. In rice-wheat rotation system, the amounts of N, P, and K natural supplying by purple soil gradually decreased in wheat season year by year, while they were stable in rice seasons. That wheat crops gradually depleted the soil fertility was more distinct than rice. The nutrients input of the natural environment played an important role on keeping the stable paddy soil fertility. The natural productivity of purple soil could support some yields of crop, which were about 1.4 t/(hm2·a) for wheat and 3.5 t/(hm2·a) for rice.