Date of Award
Master of Science (MS)
School of Biological Sciences
Victoria A Borowicz
Globally, agriculture is strained by the unpredictable effects of climate change, as well as flooding, drought, erosion, and decreases in soil fertility. To meet these challenges, agricultural systems must develop new techniques while promoting sustainable intensification practices. Cover crops can provide farmers with an off-season cash crop, while also positively impacting the soil and reducing reliance on less sustainable conventional farming practices. The objective of this research was to evaluate the impact of different cover crops on soil microbial communities at varying depths. Soils were sampled in the fall and spring from experimental plots (ISU Farm, Lexington, IL) that contained pennycress; cereal rye; pea, clover, radish, oat mix; or fallow soil. EcoPlates™ were used to conduct community-level physiological profiling (CLPP) and test the hypothesis that cover crop type and soil depth are strong determinants of microbial community diversity and functioning in an agricultural field. I predicted: (a) the physiological soil profile of the microbial community, as measured by the rate and ability to metabolize a variety of carbon sources, would change across depths and differ among cover crop types, (b) shallower depths would contain microbial communities with greater functional diversity, (c) the overall functional diversity of the microbial community would be greater under cover crops than in unplanted (fallow) fields, and (d) microbial functional diversity would be greatest in soils where cover crops with higher C:N ratios were grown, as crop residues decompose more slowly and provide more carbon for microbial metabolism. I found that theCLPP of the microbial community changed both across depths and between cover crop treatments. In both the fall and spring, evenness, richness, and Shannon diversity declined with sampling depth. Although the overall functional diversity of the microbial community did not differ among cover crop treatments, some differences were found in how the communities associated with the different cover crops metabolized the 31 carbon sources. Finally, I did not find a connection between the C:N ratio of the cover crop and the functional diversity of the microbial community. Cover crops are only one potential component to sustainable intensification, and more work is needed to develop agricultural practices that minimize environmental harm.
Hansen, Emily N., "Effects of Depth and Cover Crop Treatment on the Functioning and Diversity of Soil Microbial Communities" (2022). Theses and Dissertations. 1635.