Effect of Straw Potassium on Balance of Soil K in Wheat/Maize Rotation System

Effect of successive straw plus NP on soil K content in wheat/maize rotation system was studied according to the system methods from soil nutrition. The results showed that the effect of straw returning on available K and non-exchangeable K were more notable than mineral K and total K. Water soluble K,non-specifically absorbed K,specifically absorbed K and non-exchangeable K had positive correlation to amount of straw, but mineral K had opposite. In the exhausted condition -non-application of K-fertilizer for 14～18 years, straw plus NP could supply with available K timely, but speed up the natural release rate of mineral K. As straw application rate at the range of 2 250～6 750 kg hm-2, straw returning couldn't keep the balance of soil K, its combination to potash would slow down the decline of soil K content to some extent.