Study on balance of phosphorus and potassium in winter wheat and summer maize rotation system

The effects of a great deal of P and K fertilizers on crop yield,P,K uptake and balance and the dynamics of available P and K of soil in winter wheat/summer maize rotation system were studied The results indicated that grain yields of winter wheat and summer maize had no significant differences between with or without straw treatments and also no significant differences between conventional N fertilization and optimized N fertilization treatments The uptakes by winter wheat and summer maize were P 22～25,18～19kg/hm2 and K 147～166,96～112 kg/hm2,respectively The available P and K in soil almost had no change after a rotation period Available P and available K in soil were above 30 and 148mg/kg in soil The balance of P in with and without straw treatment had surplus 46～47 and 36～37kg/hm2 when the P application rate was 79 kg/hm2 (P),and K had surplus 22～31 kg/hm2 in with straw treatment and had deficit 168 ～201 kg/hm2 in without straw treatment when the K application rate was K 75 kg/hm2 It was suggested that straw return to the field had great effects on balance of P and K,especially K