Semester of Graduation

Summer 2021

Degree

Master of Agriculture (MAgr)

Department

School of Plant, Environmental, and Soil Sciences

Document Type

Thesis

Abstract

Perennial grass crops represent approximately 8 million hectares of the land area of the humid lower southeastern United States. These forage crops receive high rates of fertilizer, especially nitrogen (N), and near monoculture remains have often been treated with repeated applications of herbicides. Pasture management is crucial to improve soil properties in pasturelands. Common pasture management practices include introducing cool-season multispecies in warm-season pasture systems and forage harvest frequency of pasture systems. It is known that cool-season multispecies in warm-season pasture systems ensure cattle feeding during winter season and have beneficial effects on soil microbial biomass, soil organic matter (SOM), and enzymatic activity. Forage harvest frequency is needed in pasturelands to regenerate after intensive grazing, contributing to soil nutrient returns and reduce soil compaction. In this study three sites were evaluated, two in Louisiana and one in central Mississippi to determine whether soil health is enhanced by overseeding different species of cool-season annual treatments in two warm season pastures bermudagrass (Cynodon dactylon (L.) Pers.) and bahiagrass (Paspalum notatum). For this, the evaluation of microecological and chemical properties of soil were included to analyze the impact of pastureland management practices and the impact of species on soil health. Harvest frequency rates were including in plots to evaluate two harvest frequency rates at 4-week, at 8-week, and a cool-season annual mulch. Samples were collected at two depths, 0-10cm and 10-20cm to evaluate how soil properties fluctuate through soil profile. The methods used to analyze microecological properties incorporate fatty acid methyl ester (FAMEs), and enzyme assays (β-glucosaminidase and β-glucosidase). The chemical properties measured included pH, total carbo (TC), total nitrogen (TN), nutrient concentrations, SOM, and inorganic N. Significant changes over time were observed in several soil properties, one of these was SOM, which changed over time in all sites. Depth significantly influenced majority of soil properties in this study, normally soil properties decreased when soil depth increased. Absolute abundance of fungi to bacteria ratio significantly increased under an 8-week harvest frequency treatment in 2020 in one site. Overseeding legumes, annual ryegrass, and grass increased potential β-glucosaminidase in soil in Louisiana. Relative abundance of arbuscular mycorrhiza fungi and Gram-negative bacteria increase in bottom depth of soil. General responses to harvest frequency treatments suggest that 8-week harvest frequency is more beneficial for most soil properties than 4-week harvest frequency

Committee Chair

Fultz, Lisa M.

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