Energy Efficiency Of Fertilization In The Production Of Wheat And Maize In The Northern China Plain

A four-year N fertilization experiment with winter wheat-summer maize rotation and a long-term fertilization experiment with winter wheat-summer maize -"spring maize rotation were conducted in Beijing suburb to study the effect of mineral and organic fertilizer application on energy efficiency. The parameters "net energy output" and "the ratio of net energy output and input" were used to express the energy efficiency. The main results are followed:In winter wheat-summer maize rotation system, the net energy output by N fertilization in the optimized N fertilization treatment, which is based on soil Nmin test and plant tissue nitrate test, was same as that in the conventional N fertilization treatments, but N rate was less than one third of the conventional N fertilization treatments. In continuous three winter wheat growing seasons, the net energy output by N fertilization in the optimized N fertilization treatment was 31.1, 26.4 and 56.0 GJ-hm"2, respectively, and in the conventional N fertilization treatments, it was 23.3, 19.6 and 43.6 GJ-hm"2, respectively. In four summer maize seasons, there was no significance the difference of the energy efficiency by N fertilization between two N treatments.In winter wheat-summer maize - spring maize rotation system, the results showed that both of the net energy output and the ratio of net energy output and input by mineral fertilizer application 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 67.5 P2O5 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 (P2O5 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.In winter wheat-summer maize - spring maize rotation system, both of the net energy output and the ratio of net energy output and input by organic fertilizer application in no mineral fertilizer application and only N or only P mineral fertilizer application treatments were higher than that in with mineral N and P together or with mineral N, P and K together fertilization treatments. In continuous eight winter wheat seasons, the energy efficiency by organic fertilizer application in no mineral fertilizer application and only N or only P mineral fertilizer application treatments increased with year and year.