The contamination of ground water resources represents a serious
problem and a prominent threat to the health of our society. This study
focuses on the leaching of inorganic anions as a function of agricultural
practices under natural field conditions. In order to enhance the
understanding of such leaching processes, this thesis evaluates the spatial
variability of the leaching characteristics of a site, the factors controlling
percolation, and the use of a cereal rye cover crop to reduce nitrate leaching.
Thirty-two Passive Capillary Wick Samplers (PCAPS) and 32 suction
cups were installed at a depth of 120 cm under row crop produced in a
Woodburn Variant loam (fine-loamy mixed mesic Aquultic Argixeroll).
Significant correlation for the water flux was seen at the 2.0 m distance,
beyond which values were uncorrelated. No spatial correlation was seen in
hydrodynamic dispersion coefficients. Percolation was independent of field saturated
hydraulic conductivity, while the quantity of incident water was
strongly correlated with percolation. The occurrence of preferential flow
affected the leaching process as documented by solute breakthrough ahead of
the main solute peak. Rates of nitrogen fertilizer application were
proportional to observed nitrate leaching losses. The cover crop significantly
reduced the amount of nitrate leaching at all N fertilizer application rates. At
the recommended rate, nitrate-N concentrations were lowered on average
from 22.2 to 9.9 mg/l; cumulative N mass losses were cut by 62% due to plant
uptake by the cover crop. The study demonstrated the importance of
conducting long-term field experiments under natural conditions to
accurately assess leaching processes. / Graduation date: 1996
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/34891 |
| Date | 16 May 1995 |
| Creators | Hess, Mario |
| Contributors | Selker, John S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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