Objective Saline-alkali lands provide substantial land resources for photovoltaic (PV) development. While PV infrastructure may alter subsurface hydrothermal conditions and offer new pathways for land reclamation, the spatiotemporal effects of PV arrays on soil salinity-alkalinity dynamics remain inadequately studied. This study addresses the critical knowledge gap regarding PV-driven microclimate-soil interactions in soda saline-alkali ecosystems.

Methods Field monitoring was conducted at the National PV and Energy Storage Empirical Platform (Daqing Base) in the Songnen Plain during the dry season (May) and rainy season (August) to quantify local climatic variables, soil hydrothermal parameters (temperature, moisture, and heat flux), and soil properties (pH, electrical conductivity (EC), exchangeable cations K⁺, Na⁺, Ca²⁺, Mg²⁺). Measurements were stratified under photovoltaic arrays and between photovoltaic arrays during the dry and rainy seasons. Data were analyzed via ANOVA and random forest modeling to identify key drivers of soil salinity-alkalinity patterns.

Results 1) Microclimate restructuring: under photovoltaic panels, wind speed decreased by 48.46% (dry season) and 69.53% (rainy season) (P < 0.05), soil temperature reduced by 3.10 ℃ (dry season) and 1.62 ℃ (rainy season) (P < 0.05), while soil moisture increased by 11.44% (dry season) and 8.46% (rainy season) (P < 0.05) compared to conditions between photovoltaic arrays. 2) Spatiotemporal salinity-alkalinity dynamics: soil pH and EC were consistently lower in the dry season and under photovoltaic panels. EC between photovoltaic arrays exceeded values under photovoltaic panels by 31.92% during the dry season (P = 0.005), and the EC under the panels increased sharply by 138.17% compared to the between photovoltaic arrays during the rainy season. 3) Sodium-specific responsiveness: Na⁺ decreased significantly by 13.14% (under photovoltaic panels) and 12.79% (between photovoltaic arrays) (P < 0.01) during the rainy season compared to the dry season, with lower concentrations persistently observed under panels. The K⁺/Na⁺, Ca²⁺/Na⁺, and Mg²⁺/Na⁺ ratios consistently exhibited a spatiotemporal pattern of higher values during the rainy season than during the dry season, and under photovoltaic panels than between photovoltaic arrays. 4) Driving mechanisms: random forest modeling revealed that soil pH was mainly affected by soil temperature, position (under panels and between arrays), and air humidity, while EC was mainly affected by soil temperature, season, and Na⁺ content. Soil temperature was the key factor regulating both soil pH and EC.

Conclusions In summary, photovoltaic shading exerts wind-breaking, cooling, and humidifying effects under panels, ameliorating soil alkalinity and enhancing structural stability in the plough layer, as well as reducing soil Na⁺ content. This study provides a theoretical foundation for developing spatial utilization strategies featuring vegetation cultivation between photovoltaic arrays and drainage systems under photovoltaic panels to address rising pH and EC levels.