Document Type

Thesis - Open Access

Award Date

2021

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

Dwayne Beck

Abstract

A major concern of farmers implementing cover crops into a crop rotation is a potential reduction in soil moisture and nutrients available for the following cash crop. If soil moisture or nutrients are limited, the following cash crop yield suffers. One option to conserve soil moisture is to terminate cover crops with herbicides prior to a killing freeze. The purpose of this study is to develop a better understanding of the impact of cover crops and termination timing to the water and nutrient cycles and furthermore, the agronomic impact to the following cash crop (corn). Field experiments were conducted in 2019 through 2020 at the Dakota Lakes Research Farm (Pierre, SD) and on a producer’s field near Canning, SD. Three different cover crop mixes (Grass-M1 (grass dominated blend), Brdlf-M2 (broadleaf dominated blend), and Blend-M3 (equally weighted by rate of grass and broadleaves)) were planted on 2019-07-25 at Dakota Lakes and 2019-08-08 at Canning. A chemical fallow treatment was implemented as a control. Cover crops were terminated with herbicides at different times in the fall of 2019. Plant available water (PAW) was calculated using field gravimetric soil moisture percentage measurements for the 0-90 cm soil profile. At Canning, on 2019-11-15 PAW was impacted by cover crop mixture (p=0.086) with Grass-M1 containing 62 mm, Blend-M3 containing 59 mm, and Brdlf-M2 containing 49 mm. This difference was not present in the spring. The Control treatment contained significantly more PAW than the cover cropped treatments at Dakota Lakes and Canning in the fall of 2019 and again in April 2020. By June, when the corn crop is starting to use a significant amount of soil water, the Control contained more PAW than all other cover cropped treatments at Canning, but not at Dakota Lakes. At Dakota Lakes, spring soil nitrate-nitrogen was numerically lower in the cover cropped treatments than the Control. At Canning, spring soil nitrate-nitrogen was significantly lower in the cover cropped treatments than the Control (p

Library of Congress Subject Headings

Cover crops -- South Dakota.
Crop rotation -- South Dakota.
Nutrient cycles.
Soil moisture.
Herbicides.
Crop yields.

Format

application/pdf

Number of Pages

151

Publisher

South Dakota State University

Rights

Copyright © 2021 the Author

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