Research advances in the mechanisms of nitrogen-phosphorus synergy mediated by root exudates and mycorrhizal networks in cereal-legume intercropping systems.

The cereal-legume intercropping system achieves efficient utilization of nitrogen and phosphorus through interactions between roots and soil organisms, making it a key practice in sustainable agriculture. We systematically summarized the nitrogen and phosphorus mutual promotion mechanism mediated by root exudates and mycorrhizal networks in the cereal-legume intercropping system, and proposed future research directions. Cereal plants mobilize phosphorus in rhizosphere by secreting organic acids and phosphatases. The released phosphorus is then transferred to the rhizosphere of legumes via the common mycorrhizal network (CMN), alleviating phosphorus limitations, activating energy metabolism, initiating nodule formation, and promoting nitrogen fixation in legumes. Root exudates of cereal plants can directly enhance biological nitrogen fixation in legumes by stimulating the expression of key nodulation genes. The CMN transport nitrogen fixed by legumes to cereal plants in the form of amino acids and other compounds, thereby promoting root development and exudate release in cereal plants, and enhancing phosphorus mobilization capacity. Root exudates and CMN work together to form "nitrogen-phosphorus synergy" cycle, significantly enhancing nutrient use efficiency and productivity in cereal-legume intercropping systems. In the future, technologies such as metabolomics, metagenomics, rhizosphere in situ imaging, and artificial intelligence should be integrated to elucidate the multi-interface coupling mechanisms among roots, mycorrhizae, and microorganisms. This will enable the precise prediction and regulation of nitrogen-phosphorus synergy in intercropping systems, thereby providing a theoretical foundation for the development of green and smart agriculture.