College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Agricultural BMPs and Cost-Sharing(2014-12-16) Fleming, Patrick; Newburn, David A.This presentation was delivered at the 2014 Policy and Outlook Conference. The focus is on the impact of cost-sharing and the adoption of BMPs in Maryland.Item THE EFFECTS OF DRAINAGE DITCH FILTER COMPOSITION ON HYDRAULIC PROPERTIES AND P SORPTION(2014) Hamrum, David; Hill, Robert L; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Phosphorus (P) in agricultural runoff is considered a primary contributor to waterway eutrophication. Currently filters made with P-sorbing materials (PSMs) in drainage ditches have been shown to effectively remove P in some situations, but further optimization is necessary. Sorption isotherms were used to determine PSM and temperature effects on P sorption. No effect was found due to temperature, although significant differences were found among the materials used. The different mechanisms of P sorption suggest the retention time used was not suitable for this study. A mesocosm experiment was set up to maximize the flow through filters by mixing gypsum with sand to increase the hydraulic conductivity without sacrificing P sorption. The mixture containing 90% mined gypsum and 10% sand had the highest hydraulic conductivity without a reduction in total P sorption. The mixture containing 80% mined gypsum and 20% sand could have potential as an alternate mixture.Item Redox and Soil Manipulation Effects on Ditch Soil Phosphorus Processing(2012) Ruppert, David Emmanuel; Needelman, Brian A; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Ditches increase the connectivity of landscapes to open water systems, potentially facilitating the degradation of downstream waterways. A treatment and an observational experiment were conducted to identify processes behind phosphorus (P) cycling in ditch soils. If the ditch had not undergone recent dredging soils were observed in the treatment experiment to release P to surface water whether the soil system was iron (Fe)-oxidizing or Fe-reducing. Also in the treatment experiment, Fe was released to surface water in appreciable amounts only if the soil system was Fe-reducing. From the observational experiment P release due to mineralization was inferred due to a positive trend with temperature. Also in the observational experiment Fe-reducing conditions were weakly correlated with diminished P concentrations in the ditch water. It was inferred that emergent Fe(II) released from within the soil through reductive dissolution captures P from ditch surface water upon oxidation. In the treatment experiment dredging and saturated conditions resulted in similar effluent P concentrations as drained soils that were undredged. This may explain a lack of dredging effect that was observed in the field.Item Modeling Nitrogen, Phosphorus and Water Dynamics in Greenhouse and Nursery Production Systems(2011) Majsztrik, John Christopher; Lea-Cox, John D.; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nutrient and sediment runoff from the six states and Washington, DC that form the Chesapeake Bay watershed is a major cause of environmental degradation in the Bay and its tributaries. Agriculture contributes a substantial portion of these non-point source loads that reach the Bay from its tributaries. Research in this area has traditionally focused on agronomic farm contributions, with limited research on the nursery and greenhouse industry. This research presents the first known attempt to model operation-specific information, validated by published research data, where multiple variables are assessed simultaneously. This research provides growers and researchers with a tool to assess and understand the cultural and environmental impact of current practices, and predict the impact of improving those practices. Separate models were developed for greenhouse, container-nursery and field-nursery operations, since specific production variables and management practices vary. Each model allows for simple entry of production input variables, which interface with the Stella modeling layer. Each model was first calibrated with one published research study, and subsequently validated with another peer-reviewed study, with multiple independent runs for each model. Validation results for all three models showed consistent agreement between model outputs and published results, increasing confidence that models accurately process all input data. Verified models were then used to run a number of what-if scenarios, based upon a database of production practices that was gathered from 48 nursery and greenhouse operations in Maryland. This database provided a detailed analysis of current practices in Maryland, and adds significantly to our understanding of various operational practices in these horticultural industries. Results of the what-if scenarios highlighted model sensitivities and provided answers to hypotheses developed from the analysis of the management database. Some model functions, such as denitrification, would greatly benefit from additional research and further model modification. Models were designed to be easily adapted to local conditions for use throughout the U.S. and potentially other parts of the world.Item Genetic Variation in Nitrogen and Phosphorus Levels in Broiler Excreta: Opportunity for Improving both Birds and the Environment(2010) sasikala appukuttan, arun kirshna; Siewerdt, Frank; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The increase in poultry meat consumption has resulted in intensified poultry farming operations with consequent concentration of excreta in major production areas. The nutrient content in the soil surrounding the poultry farms has increased as a result of the high content of nitrogen (N) and phosphorus (P) in the poultry excreta. The current study aimed to propose a strategy to reduce the N and P content in excreta through genetic selection of broilers for efficient nutrient utilization. The traits measured (on a dry matter basis) were the percentage of N in the excreta (PNE) and the percentage of P in the excreta (PPE). Individual 24-hr excreta samples were collected from 6 wk old birds. Excreta samples were collected from a commercial breeding farm at two different time periods from line A and line B birds respectively, and analyzed for PNE and PPE. Analysis of excreta samples collected during the first period (197 bird samples belonging to 15 sire families) and second period (278 birds belonging to 25 sire families) suggested a heritability of 0.08, 0.16 for PNE and 0, 0.20 for PPE, respectively. Phenotypic and genetic correlations between the measured traits from the two lines were very low; however, phenotypic correlation analysis of PNE and PPE with other traits of commercial interest showed some favorable as well as neutral associations. Blood samples collected from the birds were used for an association study of the excreta traits with four candidate genes. The candidate genes were selected based on the results of previous research. Some of the SNPs from the candidate genes were found to have additive and dominance effect on the excreta and production traits and were usually favorably associated with mutations in higher frequency in the populations. The results suggest that genetic selection of birds for PNE and PPE could improve the environment and the market value of the birds.Item Utilizing Hybrid Poplar Trees to Phytoremediate Soils with Excess Phosphorus(2005-09-01) Neal, Amy; McIntosh, Marla S; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Phytoremediation, using plants to remove soil pollutants, has been suggested as a method to remove P from over-enriched soils. This research investigated the potential of utilizing hybrid poplar trees to remove excess P from soils associated with long-term poultry manure application. Hybrid poplar clones were planted in Snow Hill, MD, on three fields differing in previous poultry manure applications with Mehlich-3 soil-test P levels of 261, 478, and 982 mg P kg-1. During this two year study, soil P decreased on fields planted with hybrid poplar; the magnitude of the reduction was positively associated with initial soil-test P. Plant tissue P concentrations increased with soil P concentration. However, factors other than plant uptake were hypothesized to contribute to the soil-test P reductions. Results suggest that hybrid poplars have the potential to phytoremediate soils with excess P but that soil chemistry also impacts the fate of available P in the soil.