Review of techniques and case studies for saline-alkali land amelioration in the coastal regions of China

Soil salinization is one of the major challenges in agricultural production and ecological development. With the rapid development of China’s coastal areas, land resources are becoming increasingly scarce, creating an urgent need for the improvement and utilization of coastal saline-alkali land. Research findings in this area are continually expanding. However, most existing reviews of coastal saline-alkali land improvement technologies are classified based on disciplines such as physics and chemistry, which limits their guidance on technology selection and application in practical engineering. Therefore, this paper aims to systematically review current coastal saline-alkali land improvement technologies and summarize classification methods that are more practical for guiding real-world engineering applications. This paper systematically collected and screened relevant literature on the improvement of coastal saline-alkali land in China, comprehensively compared and summarized the advantages, disadvantages, and application scopes of various improvement technologies, categorized these technologies according to their regulatory and improvement objectives, and selected efficient improvement schemes under different conditions for case analysis. The findings indicate that: (1) The primary causes of coastal saline-alkali land are high soil salinity, poor physical and chemical properties of the soil, and strong capillary rise of salts. (2) Coastal saline-alkali land improvement technologies can be divided into four categories based on regulatory and improvement objectives: leaching and desalination technology, soil physical and chemical properties improvement technology, salt rise inhibition technology, and biological improvement technology. (3) Leaching and desalination, as well as soil physical and chemical properties improvement, are the most widely applied technologies in coastal areas. Salt rise inhibition technology is mainly used in areas with high salinity, while biological improvement technology involves selecting suitable plant varieties according to different salt levels. In mildly salinized soil, planting salt-tolerant crops can balance ecological and economic benefits. Based on the summary and analysis of improvement technologies, this paper proposes research directions for constructing targeted improvement technology systems for coastal saline-alkali land, ensuring efficient and safe utilization of water resources during the amelioration process, strengthening interdisciplinary research on improvement techniques, and establishing long-term management practices. These insights aim to provide basic information for efficient management and sustainable use of coastal saline-alkali land.