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.

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    Nitrogen dynamics in cover crop-based no-till corn
    (2014) Poffenbarger, Hanna Jane; Weil, Ray R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Legume/grass cover crop mixtures and sidedress subsurface band manure application are two approaches to improving nitrogen (N) use efficiency in a cover crop-based no-till corn (Zea mays L.) system. The objectives of this study were to: 1) quantify cover crop biomass and N content in response to different hairy vetch (Vicia villosa Roth)/cereal rye (Secale cereale L.) sown proportions, 2) evaluate the effects of cover crop species proportions and pelletized poultry litter (PPL) application method on residue decomposition, and 3) model the spatio-temporal dynamics of soil inorganic N as influenced by different cover crop residues and subsurface band-applied PPL. Results suggest that cover crop mixtures can accumulate as much biomass as a cereal rye monoculture and as much N as a hairy vetch monoculture, and have decomposition patterns intermediate between those of monocultures. Subsurface band PPL application provided a localized N source that did not influence decomposition of surface mulches.
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    EVALUATING THE IMPACTS OF CROTOLARIA JUNCEA, SUNN HEMP, ON ARTHROPOD POPULATIONS AND PLANT GROWTH AND DEVELOPMENT IN A ZUCCHINI INTER-CROPPED AGROECOSYSTEM
    (2012) Hinds, Jermaine Leabert; Hooks, Cerruti R.R; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Recently, studies have shown that crop diversification strategies can be effective and sustainable means of suppressing pests, improving crop growth and enhancing beneficial soil organisms. Experiments were conducted in 2009, 2010 and 2011 to investigate the impacts of the tropical cover crop sunn hemp (SH), Crotalaria juncea, utilized as a living mulch and green manure on insect populations, crop growth and the nematode community. When inter-planted as a living mulch, SH reduced populations of cucumber beetles (Acalymma spp. and Diabrotica spp.) compared to monoculture zucchini, Cucurbita pepo, plots. When SH was utilized as an organic mulch, SH treatment plots resulted in significantly larger zucchini plant biomass and yield than monoculture plots. In 2011 when SH was strip-tilled, this resulted in a more nutrient enriched soil as indicated by nematode abundances and calculated soil health indices compared to monoculture plots. Organic fertilizer application resulted in late-season increases in bacteria feeding nematodes
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    Forage Radish Cover Crop Effects on Mycorrhizal Colonization and Soil Test Phosphorus
    (2009) White, Charles Macaulay; Weil, Ray R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Forage radish (Raphanus sativus L. var. longipinnatus) and cereal rye (Secale cereale L.) cover crops were examined for their effects on arbuscular mycorrhizal colonization and P acquisition of a subsequent corn (Zea mays L.) silage crop. Soil test P following these cover crops was also measured in bulk soil collected at three depths in the surface soil and in soil sampled within 3 cm of forage radish tap root holes. Forage radish never decreased mycorrhizal colonization and rye sometimes increased colonization of the subsequent crop compared to growing no cover crop. The extent of colonization of corn roots by arbuscular mycorrhizal fungi was positively correlated with corn shoot tissue P concentrations. Slight vertical soil test P stratification in the bulk soil occurred following both forage radish and rye cover crops at some sites. A large increase in soil test P occurred within 3 cm of forage radish tap root holes.