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Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

First Advisor

Shannon Osborne


Kochia (Kochia scoparia) is getting difficult to manage in central South Dakota as biotypes resistant to glyphosate and ALS-inhibiting herbicides are becoming common. To effectively address the issue of resistant kochia in crop fields, we carried out studies to understand the biology of kochia in different crop environments. The goal of this study was to quantify the effect of crop canopies, tillage and residue on kochia germination, survival and seed production in order to develop integrated weed management recommendations that account for crop competition. Field and greenhouse studies were carried out in 2010, 2011 and 2012 in Brookings SD. The first experiment, sort to quantify the effect of crop canopies on kochia germination, survival and fecundity. Corn, soybean, field pea, spring wheat and fallow plots were established at the University farming Brookings. The magnitude of kochia shoot and seed reduction was similar among the different crop canopies. Relative to the fallow treatment, all crop canopies reduced (P2= 0.98). Generally crop presence had no effect on kochia germination and survival numbers but greatly reduced biomass accumulation and consequently seed production. A second experiment was established to simulate kochia seed survival in no-till, conventional tillage, or in a perennial crop like alfalfa. Tillage influences kochia seed placement in the soil which in turn determines the ability and timing of the seed to germinate or emerge. Timing and abundance of kochia germination or emergence was linearly related to the depth of kochia seed placement in the soil. Deep tillage reduced the number of total kochia seedlings that emerged and caused a slight delay in emergence when compared to emergence of no-till simulation. Each tillage system has pros and cons when managing kochia populations.

Library of Congress Subject Headings

Plant canopies
Weeds -- Control


Includes bibliographical references



Number of Pages



South Dakota State University


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