Influences of consecutive 13-year long-term fertilization on yields of rice and wheat and soil fertility in Xihu Plain

The consecutive 13-year long-term fertilization trials with six fertilization treatments in Xihu plain were conducted to explore influences of long-term fertilization on the yields of single-cropping late rice and winter wheat and soil fertility. The results show that yields of wheat and rice are increased significantly under the application of chemical fertilizers combined with organic manure. The results of soil nutrient analysis show that contents of soil organic matter and total nitrogen are gradually increased with experimental time among the all treatments. The highest value of soil organic matter content is observed in the treatment of the application of manure plus chemical fertilizers, which is 25.8% more than that at the beginning of the trials. Among the six treatments, the content of soil organic matter are increased in the order of manure plus chemical fertilizers (NPK) straw mulching plus chemical fertilizers (NPK) chemical fertilizers (NPK) straw control. The results of soil physical analysis show that there are significant rising trends in soil water-stable granular structure and total soil porosity during 13 years in all fertiliation treatments, which is beneficial to the improvement of soil physical characteristics. Soil nutrient balance analysis on consecutive 13-year fixed-location fertilization indicate that NPK plus manure, NPK plus straw and NPK treatments have a surplus of nitrogen and phosphorus, while straw and control treatments show deficiencies of nitrogen and phosphorus. NPK plus manure and NPK plus straw show balances of input and output of potassium in soils, while NPK, straw, and control treatments show deficiencies of potassium in soils. The consecutive fixed-location fertilization suggests that the application of chemical fertilizer combined with organic manure could increase crop yield and improved soil fertility. The increasing application of potassium fertilizer would help the balances of nutrients in soils.