Dissertation/Thesis Abstract

Soil organic matter, microbial community dynamics and the economics of diversified dryland winter wheat and irrigated sugar beet cropping systems in Wyoming
by Mukhwana, Eusebius Juma, Ph.D., University of Wyoming, 2011, 156; 3456403
Abstract (Summary)

Increasing costs, changing markets and, off-site environmental concerns have generated interest in the use of innovative tillage systems and crop rotations that improve soil quality and long term sustainability of local production systems. The Objectives of this study were to determine how alternative dryland winter wheat and irrigated sugar beet cropping systems impact (i) soil organic matter processes, (ii) microbial populations and diversity, and (ii) profitability.

On-farm field studies were conducted from 2007–2009 in Wyoming's southeastern wheat-producing region and in the Big Horn Basin. Soil, crop, and economic data were collected from non-irrigated fields under conventional wheat-fallow, organic, no-till, minimum till, and long-term grass in southeastern Wyoming. In the Big Horn Basin samples were collected from irrigated fields under five different crop rotations: sugar beet-barley, sugar beet-barley-bean, red clover-red clover-bean-bean, sugar beet-bean, and sugar beet-sugar beet-alfalfa-alfalfa.

In the wheat study, our results show that conservation tillage allows increased cropping intensity; reduced fallow periods while simultaneously increasing wheat grain and residue yield, and improving soil quality. Conservation tillage also increased both the cost of production and the profitability of dryland production systems, especially when coupled with higher precipitation. Data suggests that low adoption of conservation cropping systems in Southeastern Wyoming compared to surrounding states may be an extension issue, coupled with high conversion costs.

Results of the sugar beet study show that longer crop rotations that include legumes improved sugar beet root and top dry matter yield and soil quality, but not economic benefits. In this production system innovative crop rotations offered environmental benefits that extended beyond the farm gate, suggesting that there may be a rationale for public subsidies to support continued provision of these socially beneficial externalities.

Indexing (document details)
Advisor: Norton, Jay B.
Commitee: Kelleners, Thijs, Norton, Urzsula K., Peck, Dannele E., Thurow, Thomas L.
School: University of Wyoming
Department: Renewable Resources
School Location: United States -- Wyoming
Source: DAI-B 72/08, Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Microbiology, Soil sciences
Keywords: Dryland winter wheat, Irrigated sugar beet, Microbial community, Soil organic matters
Publication Number: 3456403
ISBN: 9781124657486
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