Research advance in the mechanism and agronomic regulation of high-efficient use of nitrogen in cereal-legume intercropping

Chemical fertilizer use is very common in agriculture for sustainable food production and food security. However, the excessive use of N fertilizer has often caused severe environmental and ecological problems. The existing issues regarding the over use of N fertilizers include groundwater pollution, greenhouse effect, biodiversity loss, etc. Cereal-legume intercropping is a yield-stable, high-efficient and sustainable cropping system compared to any monoculture. A favorable model of cereal-legume intercropping allows two distinct crops with different biological characteristics and nitrogen demand to grow together in the same field. With consideration of reasonable regulation of the differences between two crops, improvements can be achieved by taking advantage of biological N₂ fixation to reduce the use of chemical fertilizers and increase crop productivity. It is presently a hot research area to address issues on N transfer, alleviation of inhibitory effect on nodulation and N₂ fixation, and temporal-special distribution of N in cereal-legume intercropping systems. Addressing these topics will improve N₂ fixation in legume crops and reduce the heavy dependence of crop production on chemical fertilizers.Furthermore, clarifying the underlying mechanisms of the three issues will greatly enhance high-efficient use of N by the two distinct crops. Crop variety, N fertilizer management, special layout and planting density are the vital regulation measures of the interrelations between cereals and legumes. The optimization of the above measures will improve synergistic effect of competition and recovery, and enhance coordination of nitrogen use in cereal-legume intercropping systems, and thereby promote biological potential on high-efficient use of N. This paper summarized research advances in the major mechanisms of high-efficient use of N and the relevant regulatory factors in cereal-legume intercropping systems. The summary of the paper was based on the results of previous studies and the approaches of sustainable agricultural development. The objective was to provide scientific and theoretical basis for establishing a simple, high-yield, efficient and N-saving model for cereal-legume intercropping systems.