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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Item INTEGRATED ECONOMIC DECISION SUPPORT SYSTEM MODEL FOR DETERMINING IRRIGATION APPLICATION AND PROJECTED AGRICULTURAL WATER DEMAND ON A WATERSHED SCALE(2006-11-27) Hanna, Kalim; Shirmohammadi, Adel; Biological Resources Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study involves the development of an irrigation economic model used to determine the estimated net benefit of various irrigation systems when used in temperate zones. The model processes SWAT (Soil and Water Assessment Tool) output data together with user supplied economic data as a basis for identifying agricultural fields likely to result in the greatest economic return for irrigation installations, based on irrigation installation costs, water costs, and the expected revenue from increased yields due to applied water. The model is capable of not only identifying those agricultural fields within the area of interest likely to result in the greatest net benefit, but is able to prescribe the most profitable irrigation system from an array of possible systems, based on user supplied economic and performance data. The model can also be used to determine the optimal average monthly irrigation volume to be applied to a given field, by balancing the expected revenue due to the estimated yield increase as a result of irrigation application verses the cost of water. The model is applied in this study to a range of water cost levels and crop types from which general conclusions about the use of irrigation in temperate zones are made. The primary product of this study is an irrigation economic tool capable of determining the profitability of irrigation installations verses non-irrigated systems for a wide range of hydrological and environmental conditions. The project included the collection and compilation of required data on land-use, topography, and soil properties, into a GIS project, used as a data input basis for the SWAT model. For demonstration purposes the model is applied to the Pocomoke River basin located in the Coastal Plain of Maryland's Eastern Shore. Input data for the model is taken from multiple SWAT simulations for various crops, modeled with a statistically generated artificial weather pattern typical of the region. Further analysis is conducted on the environmental impact of irrigation, using SWAT model simulations over a range of irrigation application levels. General conclusions are drawn on the effects of irrigation on water quality parameters and the nutrient/sediment transport processes involved.Item WATER AND NUTRIENT DYNAMICS IN CONTAINER-NURSERY PRODUCTION SYSTEMS(2004-04-30) Ristvey, Andrew George; Lea-Cox, John D; Plant Science and Landscape Architecture (PSLA)Water quality remains a predominant issue within the Chesapeake Bay watershed, and nutrient loading continues to undermine the progressive recovery of this ecosystem. Until recently, the ornamental plant industry has had little information to develop better management practices to increase the efficiency of water and nutrient applications. This research used an integrated approach to examine container- production systems, to develop recommendations to increase nutrient uptake efficiency and reduce runoff. A 40-month field study examined the effects of various cultural practices on irrigation and nutrient uptake efficiencies. Under cyclic scheduling, drip irrigation applied 3 to 4.5 times less water than overhead irrigation and had significantly less runoff when plants were spaced at low densities. While drip irrigation is significantly more efficient, overhead irrigation is more practical and economically feasible for most small container-nursery stock. Time Domain Reflectometry (TDR) was examined as an alternative to cyclic scheduling and when used with overhead irrigation, water applications were half that of cyclic irrigation scheduling. . This research simultaneously documented nitrogen (N) and phosphorus (P) dynamics by examining nutrient applications, uptake and leaching over the forty months. In most cases, N and P uptake efficiency and runoff was negatively affected by overhead irrigation, particularly when soluble nutrients were applied via fertigation and at low plant densities. Nitrogen and P efficiencies ranged between 10 and 30% and were dependent upon methods of irrigation and fertilization, plant density and water use. The use of both drip and TDR-scheduled overhead irrigation reduced nutrient runoff to half that of the overhead irrigation program Intensive spring nutrient uptake studies showed that N influences the total growth of Rhododendron (azalea) and P uptake is a function of P fertilization rate and growth, influenced by N rate. Moderate N rates maintained optimal growth, while total P was only required at 1/20 of this N rate. Periodicity in nutrient uptake suggests seasonal timing of fertilizers may increase N and P uptake efficiency. Novel management strategies in the area of irrigation, fertilization, and cultural practices should be adopted by the ornamental industry to improve upon low efficiencies and reduce nutrient pollution in our watersheds.