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Title:Carbon and nitrogen cycling and soil quality under long-term crop rotation and tillage
Author(s):Zuber, Stacy M
Director of Research:Villamil, Maria B
Doctoral Committee Chair(s):Villamil, Maria B
Doctoral Committee Member(s):Nafziger, Emerson D; Darmody, Robert; Lee, D.K.
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):soil quality
meta-analysis
crop rotation
tillage
microbial biomass
soil organic matter
Abstract:Crop rotation and tillage can have substantial impact on the soil environment, the microbial community, and the cycling of C and N. Understanding the relationship between soil organic matter dynamics and the agronomic practices of crop rotation and tillage is key to identifying management that has the potential to enhance the production of the soils of the Midwest. In order to evaluate how tillage influences soil biology, a global meta-analysis was conducted to compare the effect of conventional tillage on microbial properties to that of no-till. Overall, greater microbial biomass and enzyme activities were found under no-till compared to conventional tillage; however, the metabolic quotient was greater in conventional tillage. This indicates that individual microbes in tilled soil are more active compared to those in no-till soils. Despite these results, a large amount of variability remained that was not able to be explained, possibly as a result of the highly variable nature of the biological measures. While a meta-analysis provides a greater inference space, field research can provide greater understanding of the impact of agronomic practices on soil processes and soil quality within a region. Long-term crop rotation and tillage experimental sites were evaluated to assess the influence of both crop rotation and tillage on highly fertile Illinois soils. Using univariate analysis, the second chapter assesses the impact of these agronomic practices on C and N within soil organic matter and microbial biomass. Crop rotations with higher C:N residues and no-till led to greater soil organic carbon and total nitrogen; however, despite the role of microbes in C and N cycling, microbial biomass was not affected by these agronomic practices as expected based on the results of the meta-analysis. The final chapter evaluates how effective these and several other properties are to serve as indicators of soil quality. The results of a principal component analysis indicated that for both crop rotation and tillage, soil parameters related to C and N cycling were very influential and have great potential as soil quality indicators. Different usage of nitrogenous fertilizers among crop rotations and the stratification of these fertilizers under no-till are other significant aspects of these agronomic practices that were highlighted by the multivariate analysis.
Issue Date:2016-12-22
Type:Thesis
URI:http://hdl.handle.net/2142/97241
Rights Information:Copyright 2017 Stacy Zuber
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05


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