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http://hdl.handle.net/10136/467
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| Title: | Agricultural chemical transport to shallow groundwater in a tile-drained, flood-irrigated field |
| Authors: | Roth, Tracy L. |
| Keywords: | t Irrigation farming -- New Mexico
Agricultural pollution -- New Mexico
Groundwater -- Pollution -- New Mexico |
| Issue Date: | 25-Aug-2009 |
| Abstract: | The Las Nutrias Groundwater Project was initiated in 1991 to address the impacts to shallow groundwater quality associated with agricultural practices typical of New Mexico. The field site is located on a commercial farm in the middle Rio Grande Valley and is characterized by alluvial floodplain soils with moderate drainage capabilities. A tile drain system is installed 4-6 ft below ground surface. Data collected over at least one growing season from this system is being used to validate a 2-dimensional, variably saturated water flow and solute transport model. The current study focuses on the mass loss of nitrogen fertilizers to the shallow groundwater as well as the development of a conceptual model to describe nutrient transport in the unsaturated zone.
In order to achieve the above objectives, extensive soil samples and tile drain groundwater samples were taken during a time period from August 1993 to May 1995. The soil samples were taken prior to the 1994 and 1995 growing seasons and were located along a transect going 38 m North and South from an instrumented tile drain line at varying depths down to the capillary fringe. These samples were analyzed for nitrate-nitrogen concentration to determine the mass loss of nitrate-nitrogen from the soil profile during the 1994 growing season. Tile drain line water samples were taken to accommodate water input events; water samples were also taken approximately twice per month from monitoring wells and piezometers located around the field site.
The soil sampling results revealed that an excessive amount (164 mg/l mean nitrate-nitrogen concentration) of soil water nitrate-nitrogen exited within the soil profile prior to the 1994 growing season. Twenty percent of this amount existed just prior to the 1995 growing season, During the 1994 irrigation season (1 March-31 October), water input events caused rapid transport of nitrate-nitrogen to the tile drain line, indicating the occurrence of preferential flow mechanisms. Electrical conductivity and chloride concentration measurements showed a similar response. Many times, the EPA maximum contaminant level of 10 mg/l nitrate-nitrogen was exceeded. From the evapotranspiration, a nitrate-nitrogen mass loss from the soil to the shallow groundwater of approximately 30-5o% was estimated to have occurred during the 1994 growing season. |
| URI: | http://hdl.handle.net/10136/467 |
| Appears in Collections: | Theses
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| Roth, Tracy L..pdf | | 6654Kb | Adobe PDF | View/Open |
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