UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2010 - 20162

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    NITROUS OXIDE EMISSIONS IN COVER CROP-BASED CORN PRODUCTION SYSTEMS
    (2016) Davis, Brian Wesley; Needelman, Brian A; Mirsky, Steven B; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Nitrous oxide (N2O) is a potent greenhouse gas; the majority of N2O emissions are the result of agricultural management, particularly the application of N fertilizers to soils. The relationship of N2O emissions to varying sources of N (manures, mineral fertilizers, and cover crops) has not been well-evaluated. Here we discussed a novel methodology for estimating precipitation-induced pulses of N2O using flux measurements; results indicated that short-term intensive time-series sampling methods can adequately describe the magnitude of these pulses. We also evaluated the annual N2O emissions from corn-cover crop (Zea mays; cereal rye [Secale cereale], hairy vetch [Vicia villosa], or biculture) production systems when fertilized with multiple rates of subsurface banded poultry litter, as compared with tillage incorporation or mineral fertilizer. N2O emissions increased exponentially with total N rate; tillage decreased emissions following cover crops with legume components, while the effect of mineral fertilizer was mixed across cover crops.
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    Steriod Hormones in Biosolids and Poultry Litter: A Comparison of Potential Environmental Inputs
    (2010) Bevacqua, Christine Elizabeth; Torrents, Alba; Rice, Clifford; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Steroid hormones can act as potent endocrine disruptors when released into the environment. The main sources of these chemicals are thought to be wastewater treatment plant discharges and waste from animal feeding operations. While these compounds have frequently been found in wastewater effluents, few studies have investigated biosolids or manure, which are routinely land applied, as potential sources. This study assessed the relative environmental contribution of steroid hormones from biosolids and chicken litter. Samples of limed biosolids collected over a four year period and chicken litter from 12 mid-Atlantic farms were analyzed for 17β-estradiol (E2), estrone (E1), estriol (E3), 17α-ethinylestradiol (EE2), progesterone, and testosterone, and the conjugated hormones E1-sulfate (E1-S), E2-3-sulfate (E2-3-S), and E2-17-sulfate (E2-17-3). Results showed that E1 and progesterone were the most prevalent compounds in both of these materials, with E1-S also present in chicken litter.