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Document Type

Thesis - University Access Only

Award Date

2015

Degree Name

Master of Science (MS)

Department

Natural Resource Management

First Advisor

Alexander J. Smart

Abstract

Mob grazing is a type of management intensive grazing system that mimics natural grazing systems where high stocking densities are placed on the land for a short period of time. One way producers measure their success with this system is by the amount of trampled vegetation present after grazing. Producers who have mob grazed for multiple seasons believe this technique improves nutrient cycling through increased trampling, which “feeds the soil bugs”. In order to quantify the effects this trampled vegetation has on ecosystem processes, we observed litter decomposition, soil moisture, and soil temperature in mob grazed areas compared to the extremes of the spectrum: Ungrazed and Bare ground plots. This study was conducted at four producer locations in South Dakota, near Quinn, Chamberlain, Eureka, and Volga in 2013 and 2014. Each study site had different stocking densities at various times of the growing season and differed in vegetation composition as well as climate conditions. Three treatments with 2 replicates were set up at each location: Ungrazed vegetation, Bare ground (litter removed), and Mob grazed. In order to measure soil moisture and soil temperature, soil sensors connected to automated data loggers were installed below each treatment. Litter bags were installed on the treatments post grazing. Two types of litter with two replicates were installed on every treatment. Types of litter were classified as: old and new. Litter bags were removed at first frost to determine overall decomposition of each treatment at each site. Litter quality was analyzed in the lab for pre-incubation and post-incubation litter. Litter quality components analyzed included C, N, acid detergent fiber (ADF), neutral detergent fiber (NDF), and hemicellulose. Soil temperature and soil moisture varied significantly between treatments at certain sites in certain years (p<0.05), and varied significantly by days (p<0.01) in both years for most sites. There were significant treatment × day interactions (p<0.05) depending on the site, year, and measured metric. In 2013, litter decomposed fastest in the Ungrazed treatment across all sites (p=0.01) and decomposed the slowest in the Bare ground treatment. There were no differences between treatments in 2014. New litter decomposed faster than old litter in both years. Litter quality components N, C, and C:N ratio were not significantly different between treatments and had mixed results between initial and final litter. Significant treatment effects were localized on specific sites in specific years for hemicellulose, ADF, and NDF. Results from this study can be used to quantify ecosystem processes in a high density “mob” grazing system. Compared to the other extremes of all litter, all vegetation (Ungrazed treatment) and the no litter, no vegetation (Bare ground treatment), mob grazing shows little difference between these for soil temperature, moisture, or nutrient cycling. Further studies could compare mob grazing to other rotational grazing schemes to determine how different nutrient cycling is between those management systems.

Description

Includes bibliographical references (pages 55-62)

Format

application/pdf

Number of Pages

73

Publisher

South Dakota State University

Rights

Copyright © 2015 Emily R. Helms

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