Nitrogen uptake, biomass yield and quality of intercropped spring- and summer-sown maize at different nitrogen levels in the North China Plain

Maize (Zea mays L.) is an important source of biomass and bioenergy in the North China Plain. In this area, which features a low amount of land per capita, more attention has been focused on producing biomass than on using agro-residues. As a result, diverse methods of maize cropping have been developed, including the maize intercropping system. This study analyzed the nitrogen uptake, biomass yield and quality of spring- and summer-sown maize grown using the intercropping system as opposed to sole cropping or double-cropping during the period 2008–2009 at two nitrogen levels of 150 kg ha−1 and 300 kg ha−1. The annual biomass, nitrogen uptake, gross energy and biomass composition (including protein, lipids, fiber, ash and nitrogen-free extract) of both spring- and summer-sown maize produced using intercropping were higher than those under sole cropping or even double-cropping. The land equivalent ratios for biomass, gross energy, and biomass composition varied from 1.39 to 1.98. Interspecific facilitation under intercropping was mainly possible because nitrogen utilization occurred at different times for the spring and summer crops and because of the increase in the nitrogen supply, which lessened the competition between them. The weather conditions during the growth stage affected the biomass and bioenergy yield of the intercrops. Regardless of the weather conditions, the advantages of intercropping relative to sole cropping were significant. The results indicate that intercropping of spring- and summer-sown maize can help farmers to produce more biomass and bioenergy in the North China Plain.