Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sandeep Kumar

Keywords

Cover Crops, Grazing, Integrated Crop-Livestock System, Soil Enzyme, Soil Health, South Dakota

Abstract

Cover crops and grazing under Integrated Crop-Livestock System (ICLS) can impact the rhizosphere nutrient cycling and may have potential to increase the long-term sustainability and economic profitability of agricultural production system. In South Dakota, crop production practices and livestock husbandry are both common which provide the opportunity for ICLS to be successful in this region. However, little is known about the impacts of the cover crops and grazing under ICLS on soil properties in this region. The present study was conducted at South Dakota State University Research Farm (44°20'34.8"N, 96°48'14.8"W), Brookings, SD, to quantify the impacts of cover crops and grazing on soil bulk density (BD), soil penetration resistance (SPR), soil water retention (SWR), pore size distribution (PSD), total nitrogen (TN), carbon and nitrogen fractions (labile, stable, and inert), microbial biomass carbon/nitrogen, urease and betaglucosidase enzyme activity. Study treatments included grass leaf and broad leaf dominated cover crop mixtures, both with and without grazing, and the cover crop control field with no cover crop or grazing. The experimental site was established on June 2016 by planting of cover crops and soil samples were collected three times i.e., pregrazing, post-grazing and summer phase at 0- to 5-cm for bulk density, SPR, SWR and PSD; 5- to 15-cm for soil microbial and enzymatic properties. The results showed that one year of cover crops did not significantly impact the soil bulk density, SPR, carbon and nitrogen fraction (labile, stable, and inert), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) or urease activity. However, beta-glucosidase enzyme activity significantly increased under broad leaf dominated cover crop mixtures as compared to grass leaf dominated cover crops and no cover crop (control) treatments at the 5- to 15-cm depth. Additionally, cold water extractable nitrogen (CWN) significantly increased under grass leaf dominated cover crops for the 0- to 5-cm depth. Broadleaf and grass leaf dominated cover crop mixtures had higher microbial and enzymatic activities as compared to the no cover crop (control) treatment, but, the differences were non-significant. Grazing treatment significantly impacted soil BD and SWR, PSD, carbon and nitrogen fraction (labile, stable, and inert), MBC, MBN, and urease but beta-glucosidase enzyme activity showed no significant differences at either depth. Sampling time significantly impacted the ρb, SWR, PSD, CWC, HWC, SMC, MBC, MBN, urease enzyme, and β-glucosidase enzyme activities. The present study concluded that one year of cover crops significantly impacted the selected soil properties i.e., CWN increased under grass leaf dominated cover crops and soil beta-glucosidase enzyme activity increased under broad leaf dominated cover crop mixtures as compare to grass leaf dominated cover crops and cover crop control treatments at 5- to 15-cm depth. One episode of grazing only significantly impacted only soil BD. Sampling time significantly impacted soil BD, SWR, PSD, CWC, HWC, CWN, HWN, OMN, SMN, MBC, MBN, urease and beta-glucosidase enzyme activity. Since most soil properties showed no significant differences by cover crop and grazing treatments during this short-term study, because they require longer timeframe to respond under different management practices, further long-term research may be required to detect impacts of cover crops and grazing management practices under ICLS on soil health.

Library of Congress Subject Headings

Integrated agricultural systems -- South Dakota.
Cropping systems -- South Dakota.
Soils -- Quality.
Cover crops.
Grazing.

Description

Includes bibliographical references (pages 51-62)

Format

application/pdf

Number of Pages

94

Publisher

South Dakota State University

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Rights Statement

In Copyright