Effects of stubble on crop yield-increase efficiency,soil nutrient status,and contribution rate of fertilization under different fertilization systems

Based on the 12 years field experiments in 1991-2002,this paper studied the effects of stubble on crop yield-increase efficiency,soil nutrient status,and contribution rate of fertilization under different fertilization systems.The results showed that compared with continuous maize stubble,soybean stubble contributed more to the high and stable crop yield,but applying fertilizer N made this yield-increase efficiency lower.The more the fertilizer N applied,the lower the yield-increase efficiency was.The decrease of yield-increase efficiency was more obvious under the application of organic manure based on fertilizer N.As for soil nutrient status,soybean stubble could not only enhance the capacity of N-supply,but also improve the capacities of P-and K-supply.The improvement of fertilization system could increase crop yield,and enhance the contribution rate of fertilization though the extent of the enhancement declined gradually.With the development of fertilization system,the difference of the contribution rate of fertilization between soybean stubble and continuous maize stubble reduced gradually,and tended to be equal at last.