Abstract: Experiments were carried out on different type of soils for 3 years. Results were as fellows:1. Half or more than half N should be applied for summer maize, followed by winter wheat, when 0.036-0.048kg/m²was applied every year. Applied N for previous crops had no significant residual effects on the following crops. The appropriate amoui.t of N fertillizer for winter wheat was 0.024 kg/m², or less than 0.030 kg/m², and for summer maize was more than 0.030 kg/m².To get higher yield and profit, more amount of N fertilizer should be applied to summer maize.2. P application both for winter wheat and for summer maize had double effects on yield: P -application had significant effects on winter wheat and summer maize, and the residual effects of P application to the previous crops on the yield and P-requirement of the subsequent crops were also significant.Applied P increased maize yield significantly. It was mainly determined by the available P content in soil, the rate of P applied to the previous winter wheat and the rate of applied N for maize.3. Summer maize was more sensitive to K than winter wheat. Applied K increased yield significantly on all experimental sites for maize, but only on sites when soil available K was bellow 90 ppm for winter wheat. Potassium application also had significant residual effects on the subsequent crops. It was suggested that more K fertilizer should be applied to summer maize.4. In view of the above, the principle of fertilizer application for wheat-maize double cropping system in Beijing suburbs should be: (1) For winter wheat, a stable amount of N should be applied and the rate of P application should be increased while K should be supplemented. (2) For summer maize, N rates should be increased while P and K should be applied.

Key words: Wheat-maize double cropping system, Nitrogen, Phosphorus, Potassium, Residual effects