Does the legacy of agricultural management determine the biodiversity and ecosystem functioning of soils?

Efforts to mitigate climate change through carbon sequestration have driven widespread inputs of organic amendments into agricultural soils, such as compost and cover crop residues. These practices rely on the ability of soil microbial communities to process carbon inputs efficiently. However, the functional and metabolic capacities of microbial communities in agricultural soils remain poorly understood, particularly in the context of agricultural management legacies. For example, historical reductions in organic carbon inputs may have shaped microbial communities with altered or constrained functions. Here, we investigate the question: Does the legacy of agricultural management alter how microbial communities respond to new carbon inputs? Specifically, in a microcosm experiment, soils from agricultural fields, ranging in crop diversification histories, were incubated with a low, medium, or high diversity of crop plant residues. Changes in microbial community composition and activities were determined. Results show that soils from polyculture systems exhibited significantly higher cumulative CO₂ respiration rates compared to monoculture soils, reflecting enhanced microbial carbon cycling activity. Additionally, microbial growth efficiency trends suggested functional distinctions in carbon utilization, with polyculture systems potentially supporting microbial communities that efficiently convert carbon inputs into biomass rather than respiring it as CO₂. These results highlight the critical role of agricultural management legacies in shaping microbial responses to organic amendments, highlighting the potential for diversified cropping systems to enhance soil carbon sequestration and ecosystem functioning.