Long-term effect of application of different fertilizer on the crop production and soil fertility in rice fields

The experimental results of application of different fertilizers and their combinations in the rice field with triple-cropping system in 1991—2000 indicated that application of pig manure only, chemical fertilizers of NPK, and NPK + pig manure increased the yields by 13.6%,32.7%, and 42.5% compared with the control(CK), respectively. The application of N 315 kg·hm~(-2)·a~(-1) could keep N balance in the rice soil studied. The recovery rates of N fertilizer were 27.3%-37.3%.The recovery rate of P fertilizer was about 25%.Application of K_2O 329.3 kg·hm~(-2)·a~(-1) could not compensated the consume of K from crop absorption, which resulting in decrease in the total K content of the soil,but soil exchangeable K was significantly increased. Continuous application of pig manure improved some soil physical properties such as soil bulk density and soil porosity.