Effects and Mechanisms of Green Manure’s Improvement in Saline-Alkali Soil: A Review

Soil salinization is a huge threat to global agricultural productivity, significantly compromising crop development and soil health. In China, the combined pressures of population growth and socioeconomic advancement have progressively diminished arable land area in recent decades, with total cultivated land nearing the threshold deemed essential for national food security. This trend has elevated saline-alkali lands to strategic importance as vital reserve resources for agricultural expansion. However, saline-alkali soils are usually characterized by elevated pH, soil salt content, structural destabilization, and persistent nutrient deficiencies. Thus, there is an urgent need for improving and remediating saline soil. Green manure emerges as an innovative and cost-effective remediation strategy for saline soils, demonstrating marked efficacy in reducing soil salinity, improving the soil structure and fertility. In this paper, a summary is given of the effects and mechanisms of green manure on saline soil properties, including PH, soil salt content, soil organic matter, soil aggregates, soil nutrients and microbial activity. Furthermore, we identify the future research directions in this field. These insights are valuable for providing theoretical foundations for establishing effective methods for applying green manure to improve saline soil.