Research of Phosphorus Balance in Rotation System of Winter Wheat and Summer Maize

The experiment was carried out to study the origin,utilization and accumulation of phosphorus in soil of high-production grain field with the rotation system of winter wheat and summer maize.The conclusions were as followed.Chemical phosphate fertilization and straw returning were the main sources of phosphorus,and that from fertilization accounted for 63.01% ~77.77%,while that from straw returning accounted for 12.83%~20.75%.The output of phosphorus to grains was about 55% of the total output.Under the condition of all straw returning,fertilizing 56 kg/hm2 phosphorus every year could maintain the phosphorus balance in soil,while 86 kg/hm2 phosphorus fertilizer was needed under the condition of without straw returning.