Integrated photovoltaic-agriculture systems enhance soil health in desert ecosystems: evidence from microbial biomass and nutrient synergies.

This study systematically evaluated the effects of three typical desert restoration models in the Hobq Desert-the integrated photovoltaic-agriculture model (PV-Ag), the artificial shrub aerial seeding model (ASS), and the bare sand with photovoltaic panels model (BS-PV)-on soil physicochemical properties, microbial characteristics, and vegetation recovery. The results indicated that the PV-Ag model performed most prominently in improving soil structure, increasing nutrient content, and enhancing microbial activity. The fine particle content in the soil reached 92.9%, while organic matter and total nitrogen content increased by 388.9-544.4% and 476.7-551.8%, respectively, compared to those in shifting sand dune (LS). Under PV-Ag model, the total soil microbial count increased more than 10 times, and microbial biomass carbon and nitrogen rose by 10.8-13.9 times and 13.4-17.1 times, respectively. The shade provided by photovoltaic panels in the PV-Ag model effectively optimized the soil hydrothermal environment, with humidity (0.043 m3/m3) and temperature (11.75 °C) being significantly better than those under the ASS and LS models, thereby promoting root biomass (1.8 g/kg) and the accumulation of available nitrogen and potassium (average increases of 188.7% and 258.5%). Correlation analysis revealed that species richness was significantly positively correlated with soil organic matter, total nitrogen, and microbial biomass carbon (r ≥ 0.96), and significantly negatively correlated with pH (r = - 0.95). Root biomass showed stronger correlations with total phosphorus, available phosphorus, and fungal abundance (r ≥ 0.80), indicating differentiated driving mechanisms of soil nutrients and microbial communities on vegetation restoration. The comprehensive soil quality index (SQI) evaluation demonstrated that the SQI value under the PV-Ag model was 810-1185 times higher than that of LS, significantly exceeding the values under the ASS (2.5-3.9 times) and BS-PV (11.3 times) models. The study demonstrates that the integrated photovoltaic-agriculture model can significantly improve desert soil quality and ecological function, offering an effective pathway for synergizing ecological restoration and renewable energy development in arid regions of the Hobq Desert.