Soil microbial and physicochemical responses to ecovoltaic systems with Noccaea caerulescens

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Abstract
Achieving the EU 2050 net-zero target requires rapid PV deployment, yet ground-mounted PV systems raise land-use concerns. Ecovoltaics (EPV) aim to co-optimize PV electrical production and ecosystem functions, but soil and especially microbial communities under PV modules remain under-characterized. In this study, PV-induced shading was hypothesised to modify plant development and the soil parameters that would structure bacterial communities. An EPV experiment was conducted with the hyperaccumulator Noccaea caerulescens cultivated in culture trays placed under three PV module technologies and different sun exposures (shade, sun and shade) and in unshaded controls. Soil physicochemical parameters, plant parameters and microbial enzyme activities were measured. The structure and diversity of the bacterial community was also characterized. In this study, plant parameters were affected by growth conditions: plant biomass and leaf C and N contents were higher under PV modules than without PV module shade, while N. caerulescens hyperaccumulation of Cd, Ni and Zn across all culture trays was maintained. Arylsulfatase, β-glucosidase, and alkaline phosphatase activities were lower under full sun conditions. Bacterial alpha-diversity was higher under both shaded and, sun and shade conditions than under unshaded controls. Furthermore, soil parameters were the primary drivers of soil bacterial community variation, with plant parameters being secondary drivers. Moreover, RDA analysis showed that soil Mn content, CEC, plant biomass, and plant C content contributed significantly to total bacterial community variation. These results suggest that PV shading has a direct effect on plant development and an indirect effect on the soil physicochemical parameters and bacterial communities.

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