In the modern age, soil fertility in agriculture is managed through the use of highly soluble fertilizers. The sourcing, manufacture, and application of these fertilizers have large environmental footprints, however. To overcome reliance on finite raw materials and lessen the deterioration of the planet’s natural resources, more ecologically-sound nutrient management is needed. Simultaneously, simplified cropping systems with high disturbance contribute to degradation of soil biological diversity. Such decline in diversity carries the risk of losing functional capacity of soils to support life above ground into the future. Plant diversity management could be the key to turning the tide of these trends in agriculture. Plants are active agents in the agroecosystem with potential to stack many functions. This thesis explores the role of plant diversity in providing ecosystem services to crop production as introduced in the literature review chapter. The next chapter looks at the phosphorus cycling potential of cover crops in soils from Michigan corn-soy-wheat rotations. The objective of this experiment was to compare the relative contributions of cover crop species, arbuscular mycorrhizal fungi (AMF) colonization, and soil phosphorus distribution to cover crop phosphorus uptake. Hairy vetch (Vicia villosa) was more highly colonized by AMF than rye (Secale cereale). When grown in soil from an organically managed agronomic treatment, vetch responded with significantly higher biomass and phosphorus acquisition when AMF was present than without colonization. Such results can inform selection of cover crops for phosphorus cycling in agriculture, accounting for the context of soil nutrient and biological status that could influence plant performance. The final chapter utilizes a dataset from smallholder farms in Central Malawi to determine how environment and farmer practices shape differences in soil microbial communities. DNA sequence data revealed differences in sample fungal and prokaryote diversity driven not only by environment but also farm management factors. In particular, intercrop diversification and crop residue retention show promise for promoting soil microbial diversity on smallholder farms in Central Malawi. Further investigation could uncover whether such shifts in microbial diversity have functional implications for soil and plant health in these settings. These chapters illustrate how managing plant diversity in agriculture recouples essential cycles that contribute to thriving agroecosystems.
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