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Title:Targeting tillage intensity in Michigan soybean systems: On-farm observations and multivariate modeling of grower decision-making with implications for yield and soil carbon
Author(s):DeDecker, James J
Director of Research:Davis, Adam S
Doctoral Committee Chair(s):Davis, Adam S
Doctoral Committee Member(s):Juvik, John A; Czapar, George F; Snapp, Sieglinde S
Department / Program:Crop Sciences
Discipline:Crop Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):soybean
tillage
decision-making
yield
soil carbon
Abstract:Soybean growers must balance multiple, sometimes competing, economic and environmental objectives when deciding what level of tillage intensity is appropriate for a given field. Research has shown that decreasing soil disturbance can reduce the cost of soybean production, but the effects of conservation tillage on the soil environment and soybean performance are elusively site-specific, making precise tillage recommendations difficult. Moreover, grower decision-making regarding tillage intensity is a socio-psychological process whereby an individual’s attitude, beliefs, and social status augment their capacity for rational utility maximization. This study aims to illuminate how soybean growers in the State of Michigan select tillage technologies, and the effect of conservation tillage on key measures of agroecological performance in the field. Building on existing work in behavioral economics, human ecology, agricultural engineering, agronomy and soil science, it asks: What factors influence Michigan soybean growers’ selection of tillage technologies, and how do selected tillage technologies interact with variation in management history and the extant biophysical environment to affect soybean yield and soil organic carbon as integrated measures of agroecological function? In the context of three local ‘learning communities’ facilitated by Extension, thirty-five Michigan soybean growers were surveyed and on-farm observations of crop, soil and environmental variables collected from one hundred and thirty-three of their commercial soybean fields over a period of two growing seasons. Analysis of this large biophysical and social data set using a combination of behavioral, mixed and structural modeling demonstrated that the effects of a particular tillage system on soybean yield and soil carbon are indeed site-specific at the sub-field level, and that grower selection of tillage technologies is influenced by both economic and social factors. These results indicate that adapting tillage technologies to the environmental and social context in which they will be applied is critical to realizing the full potential of conservation tillage and its positive contributions to agricultural sustainability. On this basis, it is recommended that outreach promoting conservation tillage in Michigan target resource limited, experienced soybean growers with loose social network ties, and farms growing soybeans on poor quality soils in warmers areas of the State.
Issue Date:2019-07-10
Type:Text
URI:http://hdl.handle.net/2142/105667
Rights Information:Copyright 2019 James DeDecker
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08


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