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Response of Soil Biological Properties to Crop Diversity, Residue Management and N Fertilization in Long-Term Maize (Zea mays L.) Cropping Systems of Eastern Nebraska
Soil microbial biomass (MB) and potential extracellular enzyme activity (EEA) are frequently used as biological indicators of soil quality (SQ) due to their sensitivity to common agronomic practices. The goal of this dissertation was to assess how common management strategies used in corn cropping systems of eastern Nebraska impact soil MB and potential EEA. Two long-term United States Department of Agriculture (USDA) field sites were sampled multiple times over two growing seasons for soil biological and chemical properties. The first study was conducted at the Resilient Economic Agricultural Practices (REAP) field site to evaluate the impact of corn stover removal level (none, medium, and high) under conventional tillage (CT) or no-till (NT) in an irrigated, continuous corn system on soil biological properties. In REAP, we demonstrate how harvesting stover decreases MB and potential EEA across tillage treatments, likely due to a reduction in microbial substrates and a loss of microbial niche. These results indicate that NT does not mitigate the negative impact of harvesting stover on soil microbial parameters. We also demonstrate how the impact of tillage and residue removal on MB and potential EEA is influenced by corn growth stage, indicating that caution must be exercised in the interpretation of microbial responses to management due to their dynamic nature. The Crop Rotation Study (CRS), a NT dryland system, was used to compare corn in rotation with continuous corn under three levels of nitrogen (N) fertilization. In CRS, we demonstrate how N fertilization drove microbial dynamics via crop productivity and the quality of crop residues. Furthermore, increasing rotation diversity promoted microbial nutrient cycling and fostered distinct bacterial communities, providing a potential belowground mechanism for how diversifying crop rotations stabilizes crop yields. Exploring these results in REAP and CRS can be used to design more resilient cropping systems, which can maintain or improve crop productivity while reducing how cropping systems negatively impact depletable soil resources.
Ramirez, Salvador, "Response of Soil Biological Properties to Crop Diversity, Residue Management and N Fertilization in Long-Term Maize (Zea mays L.) Cropping Systems of Eastern Nebraska" (2020). ETD collection for University of Nebraska - Lincoln. AAI28256228.