U.S. Geological Survey Toxic Substances Hydrology Program--Proceedings
of the Technical Meeting, Colorado Springs, Colorado, September 20-24, 1993,
Water-Resources Investigations Report 94-4015
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Spatial Variability of Soil Properties Affecting Chemical Transport
at the Plains, Georgia, Research Site
by
R. K. Hubbard (U.S.Department of Agriculture, Agricultural Research
Service, Southeast Watershed Research Laboratory, P.O. Box 946, Tifton,
GA 31793), D. D. Bosch (U.S.Department of Agriculture, Agricultural Research
Service, Southeast Watershed Research Laboratory, P.O. Box 946, Tifton,
GA 31793), R. A. Leonard (U.S.Department of Agriculture, Agricultural Research
Service, Southeast Watershed Research Laboratory, P.O. Box 946, Tifton,
GA 31793), and D. W. Hicks (U.S. Geological Survey, 3039 Amwiler Road, Atlanta,
GA 30360-2824)
Abstract
A study was conducted on a 0.81-ha site near Plains, Georgia, to determine
transport rates of water and applied agricultural chemicals to ground water
in a recharge area of the Coastal Plain. As part of the study, soil cores
were collected from the root and vadose zone to a depth of 914 cm (30 ft).
Cores were collected from 12 locations within the site to determine spatial
variability of the soil physical properties. Measurements on core samples
were made of particle size distribution, vertical saturated hydraulic conductivity,
bulk density, and soil moisture retention. Measured soil moisture retention
was compared with soil moisture retention predicted from equations based
on particle size distribution and bulk density. Analyses of the soil samples
showed that the physical properties varied both vertically and laterally.
The soil has a sandy texture at the surface, has increased clay content
from 91 to 366 cm (3 to 12 ft) deep, and then is very sandy to a depth of
914 cm (30 ft). Laterally, the plot varies in clay content in the 91 to
366 cm (3 to 12 ft) depth interval from the east to the west side, with
the northeastern corner having the highest clay content. Lower vertical
saturated hydraulic conductivities and higher soil-moisture retention and
bulk densities are associated with increasing clay content. The comparisons
between measured and predicted volumetric-water content show that the equations
adequately predict the relative magnitude of the volumetric-water content,
but that absolute predictions lack precision.
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