Abstract:A key issue to raise nutrient utilization efficiency and to mitigate environmental impact of fertilization is to balance the supplies of nutrients for crop growth.Techniques for balanced fertilization have been well developed,for(instance),soil testing and plant analyses.The aims of balanced fertilization are not only to balance nutrient input into and output from soil,but also to balance nutrient supplies for crop growth.However,indicators have not been developed to diagnose whether supplied nutrients are balanced or not for crop growth. We analyzed the N,P,K contents in grain and straw of wheat and maize harvested from a long-term fertilizer experiment located at the Fengqiu Ecological Experimental Station,Chinese Academy of Sciences.The results showed that the contents of N,P,and K in grain and straw of wheat and maize well reflected the balance status of N,P,and K supplies.Thus the analyses of nutrient contents would be able to diagnose whether the fertilization was balanced or not and to recommend fertilizer application rates and ratios of N,P,and K for the next same crop.The method for establishing relative criteria was also proposed.