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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)


Agronomy, Horticulture, and Plant Science

First Advisor

Sharon Clay


The continuous use of glyphosate-resistant crops has resulted in volunteer crops with the same herbicide resistance as the cash crop and an increasing weed problem. Volunteer corn reduces soybean yields however; little research has examined corn yield loss due to volunteer corn or volunteer soybean competition. These studies investigated yield loss and control of volunteer soybean in corn, and volunteer corn in soybean and corn. Using several densities of competitive plants, the yield loss was fit to a hyperbolic equation that indicated incremental yield loss (I value) to be 29.9 for volunteer corn in soybeans, 5.6 for volunteer corn in corn, and 3.2 for volunteer soybeans in corn. These data indicate that yield loss due to volunteer corn in soybean was six times greater than yield loss due to volunteer corn in corn and about ten times greater than yield loss due to volunteer soybean in corn. Reduced rates of clethodim resulted in partial control of volunteer corn in soybeans. Soybean yield loss was observed with 12.7 or 25.5 g a.i. ha-1 clethodim however, 51 g a.i. ha-1 clethodim showed minimal soybean yield loss. Glufosinate with a reduced rate of graminicide proved to be an option for excellent (>90%) to good (>80%

Library of Congress Subject Headings

Herbicide-resistant crops
Corn--Weed control
Soybean--Weed control


Includes bibliographical references (pages 70-75)



Number of Pages



South Dakota State University


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