Theses and Dissertations

Advisor

Dodds, Darrin M.

Committee Member

Avila, Luis

Committee Member

Krutz, Larry J.

Committee Member

Crow, Whitney D.

Committee Member

Spencer, Gene D.

Date of Degree

5-16-2025

Original embargo terms

Immediate Worldwide Access

Document Type

Graduate Thesis - Open Access

Major

Plant and Soil Sciences (Weed Science)

Degree Name

Master of Science (M.S.)

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Cover crops provide soybean producers with multiple benefits; however, cover crop residue can impose a physical barrier for herbicide spray droplets and hinder the deposition and performance of soil-applied residual herbicides. Adjuvants are routinely mixed with herbicides to improve weed control performance and may provide a way to help the spray droplets overcome the barrier that the cover crops impose. This research evaluated the effectiveness of several soil applied herbicide-adjuvant combinations to control Amaranthus spp. L., Sida spinosa L., and [Echinochloa crus-galli (L.) P. Beauv.] in soybean and the effectiveness of two surfactants for improving preemergence herbicide efficacy in a cover crop system. Generally, the herbicide/adjuvant combinations evaluated did not affect weed control; however, weed control differences due to herbicide were observed. Additionally, using an NIS adjuvant with herbicides generally improved soil deposition; however, soil deposition of herbicides was not improved by adding an OS adjuvant. A correlation was observed between treatment solutions that produced a higher proportion of droplets smaller than 100 μm in diameter and increased deposition at the soil surface. These data suggest that optimizing soil deposition and herbicide efficacy requires considering factors such as droplet size, rather than exclusively relying on adding adjuvants.

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