A
long term field experiment with winter wheat summer maize→spring maize rotation system was used to study the effect of
mineral fertilizer application on
energy efficiency in a fluvoaquic soil in Beijing suburb from 1985 to 1997. The parameter "net energy output" and "the ratio of net energy output and input" were used to express the energy efficiency. The results showed that both of the net energy output and the ratio of net energy output and input in higher mineral N application treatment(N 270 kg·hm -2 )were lower than that in lower mineral N application treatment (N 135 kg·hm -2 )in each crop growing season. A rate of P 2O 5 67 5 kg·hm -2 ·a -1 as mineral P fertilizer application obtained a higher net energy output and a higher the ratio of net energy output and input compared with higher P application treatment(P 2O 5 135 kg·hm -2 ·a -1 ). The energy efficiency by K fertilization was spring maize>summer maize>winter wheat, and was affected by weather in different years. The energy efficiency analysis could be a useful tool for the evaluation of mineral fertilizer application, and sustainability of agricultural production system.