Diversity of perennial forage species influences soil quality in Northwestern Alberta

This study evaluated the short-term effects of 15 perennial forage production systems, including three monoculture grasses, two simple mixtures (one grass and one legume), and 10 complex mixtures (i.e., one grasses-only, one legumes-only, and eight grass–legume) on physical (penetration resistance, infiltration, bulk density), chemical (ammonium, nitrate, total nitrogen, total carbon (C), total organic C, C and N stocks) and biological (CO 2 production) properties of an Eluviated Black Chernozem soil (also classified as Luvic Chernozem under the World Reference Base, WRB) in Fairview, Alberta, Canada. We collected soil samples as a baseline just before seeding in June 2020, and also in June 2023 immediately after the final forage harvest. Complex grass-legume mixtures had greater CO 2 production (laboratory-measured) in the 0–15 cm topsoil than monoculture grasses ( P= 0.039), whereas the opposite effect was found in the subsurface soil (15–30 cm) ( P = 0.003). All the forage systems assessed in the study increased soil C stocks, but monoculture grasses were the most effective at sequestering C. When considering the 0–30 cm soil profile, Fleet meadow bromegrass (MB) monoculture resulted in the highest soil C stock and C sequestration rate (71.0 Mg C ha –1 and 10.0 Mg C ha –1 yr –1 , respectively). Conversely, complex grass–legume mixtures consistently alleviated soil penetration resistance and enhanced water infiltration rates, indicating that diverse mixtures improved overall soil physical quality. Bolstering these multiple effects provides stability and functionality to soils under perennial forage production systems. • Forage diversity alleviates soil penetration resistance and enhances infiltration rates. • All the perennial forage systems assessed in this 3-yr study increased soil C stocks. • Monoculture grasses increased soil C stocks even more than diverse forage mixtures. • In a short assay, mixtures showed higher topsoil CO 2 production than monocultures. • In the subsurface soil, mixtures had lower CO 2 production than monoculture grasses.