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Microbial Communities in Agricultural Soil – Diversity, Abundance and Activity Impacted by Fertilization, Cropping and Tillage Practices

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Title: Microbial Communities in Agricultural Soil – Diversity, Abundance and Activity Impacted by Fertilization, Cropping and Tillage Practices
Author: Linton, Nicola
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Dunfield, Kari
Abstract: Soil is a complex ecosystem that supports diverse communities of microorganisms carrying out multiple biogeochemical cycles, which contribute to its health and functioning. Agricultural management practices such as nutrient inputs, tillage and crop rotations impact physiochemical and biological soil qualities, and the provision of multiple ecosystem services. The objectives of this thesis are to understand how management impacts soil bacterial functional groups involved in nitrogen cycling, as well as total bacterial and fungal diversity. We found that delayed release urea fertilizer increased nitrogen cycling gene abundance and decreased nitrous oxide emissions in a soil microcosm study. We further explored links between nitrogen cycling microbial communities and nitrous oxide emissions in a long-term field study with simple and diverse crop rotations under no till. Long-term no tillage and diversification of corn-soybean rotations with winter wheat and red clover cover increased total, nitrifying, and denitrifying (nirK and nosZ2) bacterial functional groups during the second-year corn phase. Nitrous oxide emissions occurred after urea ammonium nitrate fertilization and were higher in the diverse rotation, highlighting that agricultural management practices can improve soil health but also lead to alteration of nutrient cycling pathways as a tradeoff. The effects of long-term tillage and crop rotational diversity on total bacterial and fungal diversity were also explored through use of high throughput sequencing of soil sampled during the second-year corn phase. Tillage decreased bacterial and fungal diversity but increased community evenness. Alfalfa alone or in rotation with corn increased fungal diversity metrics but had less of an impact on bacterial diversity. Bacterial and fungal community composition was shaped by both tillage and crop rotational diversity. Tillage and crop rotational history were associated with bacterial and fungal taxonomic groups that were relatively more abundant in soils under each long-term management strategy. This thesis shows how a multitude of bacterial functional groups, as well as total bacterial and fungal communities can be shaped by agricultural management practices and influence the processes that provide many soil ecosystem benefits.
Date: 2020-01
Rights: Attribution-NonCommercial-NoDerivatives 4.0 International
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Attribution-NonCommercial-NoDerivatives 4.0 International Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivatives 4.0 International