Impact of Fertilizer, Corn Residue, and Cover Crops on Mycorrhizal Inoculum Potential and Arbuscular Mycorrhizal Fungi Associations

Arbuscular Mycorrhizal Fungi (AMF) can associate with roots of most land plants, helping to take up water and nutrients. Intensive agricultural practices like fallow treatments and adding inorganic nutrients reduce soil AMF. The purpose of my research was to examine whether three factors influenced AMF-crop associations: 1) fertilizer type and application rate 2) inclusion of cover crops that do or do not associate with AMF, and 3) impacts of corn residue. Soil Mycorrhizal Inoculum Potential (MIP) was measured to test treatment differences. MIP is the ability for soil AMF to infect roots. Roots grown in soil from the different treatments were evaluated in a MIP bioassay. In situ AMF colonization data for roots of field-grown plants was assessed. In the fertilizer experiment, MIP was significantly greater in the no-fertilizer and manure fertilizer treatments, indicating more AMF associations. Adding full, or half the amount of fertilizer had lower MIP, showing that increased nutrients reduced plant-AMF associations. Forage radish does not form AMF associations while annual ryegrass does, but in the cover crop experiment, no significant differences between these cover crops and fallow treatments occurred. Corn residue removal was expected to reduce soil health and reduce AMF associations; however, there were no significant differences compared to the residue retention treatment. Overall, fertilizer type and amount influenced AMF, but certain cover crops and residue did not.