Impacts of Managed Grazing on Soil Health at Utility Scale Solar Energy Sites

The concept of agrivoltaics' or the co-location of photovoltaic (PV) arrays with agrarian land uses is emerging as a synergistic use of spatial resources for meeting global goals of carbon-neutral energy production. Among various agrivoltaic designs, the co-location of PV array sites with managed sheep grazing is emerging as a favorite, as it requires minimal modifications to the landscape and can contribute to the restoration of valuable soil resources. However, there has been a paucity of long-term field studies investigating impacts of managed sheep grazing on soil health. To address this knowledge gap, we investigated the changes in soil carbon and nitrogen content (0-30 cm), soil particle size distribution, bulk density, aggregate stability, microbial activity, and soil compaction at six solar energy sites in Minnesota, USA with native vegetation and managed grazing. The sites are all located on previously cultivated fields and are comparable in climate, ecoregion and management, but differ in soil texture and grazing history. The results indicate that managed sheep grazing significantly increased total carbon storage (10-80%), with the magnitude of change affected by soil texture at the study sites. The grazed sites showed a significant increase in available nutrients and microbial activity, indicating an overall improvement in soil quality. Negative impacts often associated with grazing, such as increased soil compaction and bulk density were not observed, a result possibly attributable to the lower intensity rotational grazing strategy. Solar grazing systems offer a promising approach to sustainable land management, combining renewable energy production with agricultural practices that enhance soil carbon sequestration, preserve land for future food production, promote biodiversity and diversify revenue streams. The findings from these assessments indicate an approach that optimizes the environmental and financial outcomes of integrating grazing at solar energy sites, that ultimately determines whether these agrivoltaics strategies are viable.