Advances and prospects of closed-loop precision irrigation for synergistic water-salt-phosphorus regulation in saline-alkali soils

Saline-alkali soils are among the most challenging soil types in agricultural production owing to the intricate coupling relationships among water, salt, and nutrients. Precision irrigation offers a crucial means of enhancing water use efficiency, improving nutrient availability, and mitigating secondary salinization. This paper provides a comprehensive review of the research advancements in recent years on the integrated applications of precision irrigation monitoring technologies, intelligent control strategies, and terminal irrigation equipment in saline-alkali soil regions. Particular emphasis is placed on the construction and development trends of closed-loop precision irrigation systems. A "perception-decision-execution" ternary closed-loop regulation framework is proposed. The key mechanisms underlying its role in the coordinated regulation of water, salt, and phosphorus are explained in detail. Moreover, the coupling relationships between soil moisture, salinity, and phosphorus availability, along with the approaches for their coordinated regulation, are further explored. The potential of microbial fertilizers in promoting phosphorus activation and alleviating salt-alkali stress is also analyzed. The challenges faced include the absence of reliable models capable of capturing the dynamic phosphorus transformations under water-salt regulation, the lack of cost-effective real-time in-situ phosphorus monitoring tools, and issues related to equipment reliability. Additionally, the future development directions of an intelligent closed-loop irrigation system for the coordinated regulation of water, salt, and phosphorus are envisioned. This paper provides a theoretical reference and research foundation for the sustainable agricultural management of saline-alkali ecosystems. • A new closed-loop irrigation mechanism for water-salt balance in saline-alkali land. • Emphasis on multi-dimensional monitoring technology for saline-alkali land. • Underscores the role of biofertilizers in P mobilization and soil health. • Efficient synergy between irrigation and microbial fertilizers on saline-alkali land.