Date of Award

12-2007

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Fred L. Allen

Committee Members

Arnold M. Saxton, Donald D. Tyler, Dennis R. West

Abstract

No-till acreage is increasing in the United States as producers begin to recognize the environmental and economic benefits of this management system. Although the potential to receive carbon credits or payments for maintaining or initiating no-till may encourage producers to employ these practices, crop yields will be a factor in management decisions. Our objective was to examine the effects of combinations of cropping sequences and winter biocovers upon glyphosate-tolerant corn, cotton, and soybean yields under long-term no-tillage at two locations in Tennessee. Research was conducted during the first four-year phase (2002-2005) of a two-phase agronomic systems study (2002-2009) at the Research and Education Center at Milan (RECM) in Milan, Tennessee, and the Middle Tennessee Research and Education Center (MTREC) in Spring Hill, Tennessee. The experiment was a randomized complete block design with split block treatments, with the main plots consisting of 13 different cropping sequences of corn, cotton, and soybean at RECM and eight different cropping sequences of corn and soybean at MTREC. The subplots consisted of hairy vetch, wheat, poultry litter and fallow biocovers applied perpendicular to the sequences. Rotated corn and soybean yields were comparable to or higher than their respective monoculture sequences at both locations. At RECM, cotton yields took longer to respond to rotation as rotated cotton yields only outperformed continuous cotton in the final year. At both sites, corn and soybean yields were highest under fallow and poultry litter biocovers, respectively. Cotton yields were highest under poultry litter at RECM. Interaction effects of cropping sequence x biocovers were inconsistent as interaction effects were only observed on corn yields at MTREC in 2004 and 2005. Hairy vetch, wheat, and poultry increased yields when changing from continuous corn to rotated corn. The presence of some cropping sequence x biocover interaction effects is encouraging and perhaps suggests a longer time period may be needed for the combined effects of crop sequence and biocovers upon crop yields to become apparent. Results from the next four years of the experiment will provide more information on the long-term effects of crop sequence and biocovers on corn, soybean, and cotton yields.

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