Nitrogen environmental endurance and economically-ecologically appropriate amount of nitrogen fertilizer in faba bean/maize intercropping system

The effects of nitrogen application rates on the productivity, nitrogen uptake and utilization，and soil inorganic nitrogen accumulation were investigated in faba bean/maize intercropping system through field experiment conducted in Hexi Corridor of Gansu Province. The economically-ecologically appropriate amount of nitrogen fertilizer applied was further studied on the basis of linear plus plateau model. The results showed that the correlations between the productivity and soil inorganic nitrogen accumulation and nitrogen fertilizer were significant by linear plus plateau model and quadratic curve model respectively. Compared with sole cropping system, intercropping significantly increased system productivity and nitrogen acquisition by 23% and 33%, respectively. The productivity, nitrogen uptake and utilization efficiency, and soil inorganic nitrogen accumulation of intercropping increased with the increase of nitrogen application rate, indicating that over abundant nitrogen uptake exited under high nitrogen fertilizer and intercropping. The optimized nitrogen application rate was 186 kg/hm2, considering both ecological and economic benefits. Under this nitrogen application rate condition, the intercropping productivity was 1.06×104 kg/hm2, increasing by 14%, saving 38% nitrogen input, and deceasing by 75% inorganic nitrogen accumulation, compared with sole cropping system.