SCSB# 395
MLRA 136: Southern Piedmont
D.E. Radcliffe and L.T. West
University of Georgia-Athens

Chapter Contents:

Location, Extent, and Landuse
The Southern Piedmont region extends from northern Virginia to eastern Alabama and includes large parts of North Carolina, South Carolina, and Georgia, as well as a small part of Tennessee with a total land area of 16,698,600 ha. Most of this area is in small farms, but a sizable acreage is controlled by woodland companies. Land adjacent to major cities is used for residences and associated urban development. Although most of the land was once cultivated, much has reverted to mixed stands of pine and hardwoods. Most of the open land is pasture, but some crops, such as soybeans, small grain, corn, cotton, wheat, and, to a lesser extent, tobacco, are grown. Dairy cattle and poultry are important locally (USDA, 1981).

Climate, Physiography, and Geology
Average annual precipitation varies from 1,150 to 1,400 mm. Precipitation is evenly distributed throughout the year, but the lowest is in autumn; snowfall is light. Average annual temperature varies from 14 to 18°C. The average freeze-free period varies from 205 to 235 days (USDA, 1981).

The majority of the Piedmont major land resource area (MLRA 136) is underlain by metamorphic and igneous rocks ranging in age from Precambrian to late Paleozoic (Hack, 1989). Over most of the region, these rocks have been weathered to saprolite. Both grade of metamorphism and rock composition vary considerably across the region. The area is dominantly felsic (light-colored, acid, high in silica) igneous and metamorphic rocks (granite, granite gneiss, mica gneiss, mica schist), but large areas of intermediate and mafic (dark-colored, basic, magnesium- and iron-rich, low in silica) rocks occur. In addition, mafic dykes often occur in regions of more acid rocks which alter parent material composition and complicate soil patterns.

There are two minor areas within the Piedmont with considerably different geology and thus, soils than the rest of the region. The first is a series of down-faulted basins containing sedimentary sandstones, siltstones, mudstones, and shales of Triassic and Jurassic age (Hack, 1989). The second is generally referred to as the Carolina Slate Belt which is an area of low relief containing Cambrian and Precambrian low-grade metamorphic rocks of volcanic origin (slate, acid and basic tuff, breccia, and flows) (Hack, 1989). Because these rock types are different than most of the Piedmont, different soils occur in these regions.

The Piedmont is generally well dissected with commonly accordant summits constituting a broad plateau-like surface. Maximum relief in the region is generally less than 350 m though higher isolated peaks occur (Murray, 1961). The region slopes to the east and south with general surface slope being about 4 m km-1. The lack of topographic expression on the interfluves has been used as evidence that the Piedmont is a peneplain (Thornbury, 1965; Holmes, 1964). An alternate hypothesis is that this surface is the result of long-term weathering and uplift in the region. Mineralogy and water chemistry in the region suggest that 1 m of saprolite will form in about 250,000 years (Pavich, 1986). This rate of saprolite formation is within a factor of two of the estimated rates of erosion and uplift for the region (Pavich, 1985). Thus, as saprolite and soil form from the underlying rock and mass is lost to solution, stream divides are lowered and flattened. As this process continues, the surface rebounds in response to lowered overburden pressure, and the result is the broad plateau-like surface observed in the Piedmont.

The high stream gradient in the region results in relatively narrow floodplains and deeply incised streams. Flooding in the region, though common, is generally of short duration (3 to 7 days), and the strong gradient from the floodplain to the incised stream results in a large portion of the soils in floodplains being well or moderately-well drained. These level, well-drained floodplains were the sites of choice for settlement when European man came to the region in the mid to late 1700s. Only after the floodplains were completely settled did these settlers venture into the more rolling (and erodible) uplands (Trimble, 1974).

Fig. 1. STATSGO soils of the Southern Piedmont in MLRA 136.

Because the region is characterized by rolling summits and relatively steep backslopes, most soils are well drained and at least moderately permeable (> 0.036 cm h-1 , Table 1 and Fig. 1). Thus, differences among soils are more often related to nature of the saprolite parent material and landscape position than to major differences in permeability and internal drainage. Historically, the soils have been considered to have developed in residual parent materials, but recent evidence suggests that many of the soils on lower slope positions have, at least in part, developed in colluvial parent materials (Stolt et al., 1993). However, other than limited mixing of acid and mafic rocks, the composition of the colluvium is similar to that of the residuum, and it is difficult to separate colluvial materials from residual saprolite unless a stone line or other readily observable marker is available (Daniels et al., 1984). Thus, few soil distinctions have been made based on this difference in parent material.

For purposes of the remainder of this discussion, soils in the Piedmont will be divided into four broad groups based on parent material composition: 1) soils developed from felsic igneous and metamorphic parent materials, 2) soils developed from intermediate to mafic igneous and metamorphic parent materials, 3) soils developed from fine-grained sedimentary and metamorphic parent materials, and 4) soils developed from alluvium from mixed crystalline rocks.

Soils Developed from Felsic Igneous and Metamorphic Parent Materials
The majority of the Piedmont is underlain by felsic igneous and metamorphic rocks such as granite, granite gneiss, mica gneiss, and mica schist. Soils associated with these bedrock types comprise about 51% of the soils that have been mapped in the Piedmont and include Appling, Cecil, Helena, Louisa, Louisburg, Madison, Pacolet, Tallapoosa, Vance, and Wedowee (Table 1). These soils generally have sandy loam surface horizons overlying clayey argillic horizons. The soils are acid, have low base saturation, and kaolinite is the dominant clay mineral. The abundance of low activity clays in these soils results in low cation exchange capacity (CEC), low shrink-swell potential, and moderate rates of water movement through the soil. Because of their low pH, low base saturation, and kaolinitic mineralogy, these soils have often been considered to be old and highly weathered. Granted, many of the soils and landscapes in the Piedmont are quite old, but similar chemical and mineralogical characteristics are found in relatively young soils developed in these acid crystalline rocks. Free movement of water through the coarse-textured saprolite results in rapid transformation of K-feldspars and biotite to kaolinite and rapid leaching of the limited amounts of basic cations contained in the parent rock. Thus, the characteristics of these soils are related to the nature of the parent rock as much as, if not more than, age and degree of soil development.

Most of the differentiating criteria among soils associated with acid crystalline rocks in the Piedmont are based on solum thickness and color of the Bt horizon. Cecil, Appling, Helena, and Vance soils have sola thicker than 1 m. Appling soils have Bt horizons with hues of 5YR to 5Y while Cecil soils have Bt horizons with a hue of 2.5YR or redder. These soils occur on a variety of landscape positions but are more commonly found on more gently sloping landscapes. Vance and Helena soils are developed from a mixture of felsic and mafic rock or from a slightly more mafic residuum than Appling and Cecil. The presence of iron (Fe) and magnesium (Mg) bearing minerals in the parent materials for the Vance and Helena soils results in their having mixed mineralogy (more than 10% 2:1 expandable clay minerals) and slower permeability than Appling and Cecil. Vance soils occur on the same landscapes as Appling and Cecil, and separation of Vance and Appling can be difficult. Helena soils commonly occupy concave areas along intermittent streams and heads of drains and have a seasonal water table within the upper Bt horizon.

Louisburg, Madison, Pacolet, and Wedowee soils have sola from 0.5 to 1 m thick. Pacolet and Wedowee soils are analogous to Cecil and Appling with Pacolet soils having red Bt horizons and Wedowee soils having yellowish brown Bt horizons. Pacolet and Wedowee commonly are found on steeper slopes than Cecil and Appling. Madison soils have red Bt horizons and common or many mica flakes in the upper part of the Bt horizon. These soils commonly occur on more broken topography than Cecil. Louisburg soils have discontinuous, coarse-loamy Bt horizons and are commonly formed in saprolite from granite or granitic gneiss. Louisa and Tallapoosa soils have soft rock (Cr horizons) within 0.5 m, loamy Bt horizons, and abundant mica within the solum.

Appling and Wedowee commonly occupy broad summits or lower backslope positions, and the yellowish brown color of their Bt horizons may be related to very short periods of saturation and reduction in these horizons (Macedo and Bryant, 1987). Hematite has been shown to be more easily reduced than Al-substituted geothite (Macedo and Bryant, 1989). Thus, short periods of saturation may be causing reduction and loss of hematite from these horizons. The residual geothite would give the horizons the yellowish brown color observed.

Soils Developed from Intermediate to Mafic Igneous and Metamorphic Parent Materials
Soils associated with intermediate to mafic crystalline rocks comprise about 10% of soils that have been mapped in the Piedmont and major soils include Davidson, Enon, Gwinett, Hiwassee, Mecklenburg, and Wilkes. The relationships among these soils and between soils and bedrock are complex. Felsic crystalline and more mafic rock are intimately associated which results in a very complex soil pattern. Alfisols and dark red Ultisols from residuum or locally derived alluvium or colluvium from mafic rock occur on the landscape with red and yellow Ultisols derived from felsic rock. In addition, all gradations of rock composition from ultra-mafic to acid granite occur.

Davidson, Gwinett, and Hiwassee are commonly considered to be associated with rocks or local alluvium with intermediate content of Fe and Mg bearing minerals (Daniels et al., 1984). These soils are well drained Ultisols, have sandy loam surface horizons overlying clayey Bt horizons, and the clay minerals are dominantly kaolinite. Thus, CEC and shrink-swell is low, and rate of water movement through the soil is considered to be moderate. Because of higher contents of Fe bearing minerals in the parent rock, these soils generally have higher contents of Fe and manganese (Mn) oxides than soils from felsic rocks. The increase Fe and Mn oxide content gives Bt horizons in these soils a dark or “dusky” red color (hue of 2.5YR or redder and value of 3 or less; Rhodic subgroup) and well-expressed fine structure (Daniels et al., 1984).

Differentia among the three soils are related to presence of this color and solum thickness. Davidson soils have thick sola, and Bt horizons are dark red throughout their thickness. Gwinett soils have similar colors, but solum thickness is 0.5 to 1 m. Hiwassee soils are also deep but lack the dark red color in the lower part of the Bt horizon and are often associated with old alluvium or colluvium.

Enon, Mecklenburg, and Wilkes soils are associated with mafic crystalline rock, and the higher content of basic cations in these rocks has resulted in these soils being classified as Alfisols. In addition, these soils have more than 10% 2:1 expandable clay minerals in Bt horizons and thus, mixed mineralogy. The two soils with thick sola, Enon and Mecklenburg, have tight, clayey Bt horizons, moderate shrink-swell, and slow rates of water movement through the soil. Even though the Bt horizon of the Wilkes soil has loamy texture, the presence of appreciable 2:1 clays in these horizons result in the soil having a moderately-slow permeability.

Soils Developed from Fine-Grained Sedimentary and Metamorphic Parent Materials
Soils associated with fine-grained rocks of the Carolina Slate Belt, the Triassic basin, and other isolated areas of fine-grained metamorphic rocks comprise about 12% of soils that have been mapped in the Piedmont. Major soils include Badin, Georgeville, Herndon, Mayodan, Nason, and Tatum. Within the Carolina Slate Belt, interfluves are irregular, and sharp topographic breaks are common. Deep soils generally occupy more gently sloping parts of the region, and shallow soils occur on convex parts of the landscape. Valley sides are short (Daniels et al., 1984).

The Triassic Basin is topographically lower than the bulk of the Piedmont landscapes that surround it, and local relief is generally less than most of the Piedmont. The Triassic rocks include shales, dark and light colored sandstones, mud-stones, siltstones, and conglomerates. These rock types are apparently easier to erode than the surrounding crystalline rocks which accounts for the topographic low nature of the basin (Daniels et al., 1984).

The fine grain size of the rocks associated with the Carolina Slate Belt results in soils with higher silt and very fine sand contents than the rest of the Piedmont. Surface textures are generally silt loam and Bt horizon textures range from silty clay loam to clay. As in other Piedmont soils, the dominant clay mineral in most of these soils is kaolinite. There are, however, more 2:1 clay minerals in these soils than is normally present in soils associated with felsic crystalline rocks. Thus, CEC is greater than the maximum allowed for placement as Kanhapludults or Kandiudults (16 cmol kg-1 clay), and many of the soils have mixed rather than kaolinitic mineralogy in upper Bt horizons (Table 1).

Another similarity with soils developed from felsic crystalline rocks is differentiation among the major soils based on soil depth and Bt horizon color. Georgeville soils are deep and have Bt horizons with hues of 5YR or redder. Herndon soils are also deep, but Bt horizons have yellower hues than Georgeville. Tatum soils have Bt horizons with red hues, and Nason soils have Bt horizons with yellower hues. These soils, however, have soft rock (Cr horizons) between 1.0 and 1.5 m below the soil surface. Badin soils have strong brown to red Bt horizons, but the Cr horizon occurs within a 1 m depth. In general, the deep soils associated with these fine-grained rocks occupy the more gently sloping parts of the landscape, and the soils with rock within 1.5 m are found on convex landscape components and in more dissected areas. As in soils associated with felsic rocks, the difference in Bt horizon color (brown or red) may be related to preferential reduction and solubilization of Fe in hematite under short periods of saturation or may be related to differences in the parent rock.

Mayodan soils have moderate permeability, are well drained, and occupy narrow interfluves and other better drained areas. Creedmore soils occur on smooth landscapes that are lower lying that Mayodan landscapes. This soil is moderately-well drained, has a slowly permeable Bt horizon, and has redox depletions within 60 cm of the upper boundary of the Bt horizon. White Store soils are somewhat-poorly drained Alfisols with mixed mineralogy. The Bt horizon of these soils has redox depletions and is slowly permeable.

Soils Developed from Alluvium from Mixed Crystalline Rocks
Soils developed in alluvium in the Piedmont comprise about 5% of soils that have been mapped in the Piedmont. Major soils include Chewacla, Toccoa, and Wehadkee. These soils occur on floodplains and terraces of streams in the region which represent the major area of nearly level land within the Piedmont. Broad floodplains and terraces only occur on major rivers. Because of high stream gradients, smaller streams have narrow floodplains and small discontinuous terrace remnants (Daniels et al., 1984). In most years, these soils will flood, but because of deep incision of the stream channels and high stream gradient, the floods are normally for only a few days.

Texture and composition of the alluvial soils greatly depend on the texture and composition of the soils and saprolite from which the parent sediments were derived and stream energy at the time the materials were deposited. Surface horizon textures range from sandy loam to silt loam. Subsoil horizons generally have a similar textural range. C horizons are texturally variable ranging from extremely gravelly sand to clay. Variation in drainage class among the floodplain soils is related to topographic position within the floodplain and addition of water from upland sources. Because of deep incision of the stream channel, the gradient for water movement is from the floodplain to the channel. Seeps are common along escarpments into the upland, and most water creating seasonal water tables in these soils is saturated return flow from upland sources.

Chewacla soils have a weakly-developed Bw horizon that is often thin but can be up to 1.5 m thick. Clay content in the Bw horizon ranges from 18 to 35%, and the soil has moderate permeability. Redox depletions and concentrations occur with 60 cm of the soil surface. Toccoa soils are moderately-well and well drained and have moderately-rapid permeability. The profile consists of a thin A horizon overlying a C horizon with less than 18% clay. Wehadkee soils are poorly or very-poorly drained and have moderate permeability. These soils are wet and redox depletions occur immediately below a thin A horizon. Clay content in the Bg horizons ranges from 18 to 35%.

In the southern Piedmont region, the ground water system is an unconfined two-layer system composed of a zone of saprolite underlain by fractured bedrock (Le Grand, 1988). The saprolite layer consists of highly weathered crystalline rock and averages 20 m in thickness. Saprolite thickness up to 100 m has been reported, however (Hack, 1989). Recent studies have shown that the saprolite layer is an integral part of the ground water system and acts as an important water storage zone for the deeper fractures (Brackett et al., 1991; Cressler et al., 1983; Radtke et al., 1986; Rose, 1992). Recharge occurs throughout the uplands in this shallow groundwater system. Bracket et al. ( 1991) concluded “since almost all ground water in the Piedmont/Blue Ridge can be considered as being part of the surface or water table aquifer, it is quite prone to pollution from man-made sources.” Many rural older homes in the Piedmont region obtain their drinking water from dug or bored wells that draw water from the saprolite storage layer and do not penetrate the bedrock. Newer homes, commercial operations, and farms that require high yielding wells are likely to have deeper, more expensive drilled wells that are cased through the saprolite zone and penetrate bedrock to draw water from fractures. The depth to the water table may be as shallow as 2 to 6 m in upland areas during the winter and the water table elevation generally follows the surface topography (LeGrand, 1988).

Pavich et al. (1989) examined saprolite cores in three types of parent rock in the Piedmont of Virginia: felsic (quartzofeldspathic), mafic (diabase), and ultra-mafic (serpentine) rocks. Saprolite was thickest in the sites with felsic parent material (average of 15 to 30 m). This was attributed to a high content of quartz and muscovite that resists weathering. These minerals provide a stable, porous matrix through which water can move, dissolving away the less resistant minerals (such as plagioclase). The chemical dissolution front occurs near the base of the saprolite layer so that saprolite can be subdivided into a relatively inert upper half and a relatively reactive lower half. The mafic and ultra-mafic material have less resistant minerals so they form thinner saprolite layers (a few to 10 m in mafic rock and none in ultramafic rock).

Water and Solute Transport

Saturated Water Flow
Saturated hydraulic conductivity (Ks ) varies sharply among horizons in soils of the Southern Piedmont. Most studies have found that Ks is highest in the Ap and BA horizons and reaches a minimum near the bottom of the Bt and top of the BC or CB horizons where the transition between soil and saprolite occurs. Bruce et al. (1983) examined nine pedons of the Cecil soil and found that Ks in the Ap horizon was usually 10 cm h-1 or more, whereas Ks in the lower Bt and BC horizons were often 10-2 or 10-3 cm h-1 . Workers in North Carolina also found that the minimum Ks occurred in the lower B and BC or CB horizons (Schoeneberger and Amoozegar, 1990; Vepraskas et al., 1991; Williams et al., 1994) (Fig. 2). Radcliffe et al. (1990) measured steady state ponded infiltration rates in a series of adjacent Cecil and Pacolet soils and found that the infiltration rate was higher in the Cecil. This was attributed to the thicker Ap and BA horizons in the Cecil. Chiang et al. (1987) studied three soils (Cecil, Davidson, and Iredell) from the Southern Piedmont and showed that clay dispersion could significantly reduce topsoil Ks . Increasing the soil sodium adsorption ratio and pH and decreasing the soil solution electrolyte concentration reduced Ks . The soils derived from mafic rock (Davidson and Iredell) were less dispersive than the soil derived from felsic rock (Cecil).

Fig. 2. Vertical saturated hydraulic conductivity (Ks ) of Bt, B/C, and C horizons and the fitted curve for the ridge top geomorphic position. Horizontal bars indicate the range of standard deviations for the three horizons (from Schoeneberger and Amoozegar, 1990; 1 m s-1 = 3.6 x 105 cm h-1 ).

Unsaturated Water Flow
Bruce and coworkers measured water characteristic (q[h]) and unsaturated hydraulic conductivity (K[h]) functions in the A and B horizons of a Cecil and used numerical simulations and measurements of infiltration rates to estimate the effect of these horizons on unsaturated water flow. Bruce and Whisler (1973) and Bruce et al. (1976) compared predictions of a numerical model to measured infiltration rates in the Cecil. The model predicted that infiltration rates would decrease sharply as the wetting front moved through the upper B horizons and reach a relatively constant minimum rate as the wetting front reached and passed beyond the lower B horizons. The model also predicted positive pressure potentials would develop in the lower B horizons as the wetting front arrived. The model accurately predicted measured infiltration rates in sod plots but overestimated infiltration rates in tilled plots. This was attributed to surface sealing in the tilled plots which was not accounted for in the model.

Extensive information on water characteristic and unsaturated hydraulic conductivity functions for the Cecil soil are also contained in the report by Bruce et al. (1983). A total of 15 pedons in Alabama, Georgia, South Carolina, and Virginia are described. Cores were taken from each horizon and a water characteristic curve was developed. Saturated hydraulic conductivities for these cores were also reported so this data can be used to develop unsaturated hydraulic functions using indirect methods (van Genuchten and Leij, 1992; McVay and Radcliffe, 1998). They also used the instantaneous profile method (Cassel, 1972) to measure in situ K(h). Tensiometer data showed that during drainage pressure potentials increased in the lower B horizons where flow was restricted. The authors found that the water contents in the field associated with a given K(h) in the lower B horizons were less than the water content estimated from the laboratory water characteristic function, due perhaps to entrapped air. This was not the case for the A and upper B horizons.

Another source of information on water characteristic and unsaturated hydraulic conductivity functions is the Unsaturated Soil Hydraulic Database (UNSODA) of Leij et al. (1994). The database contains descriptions of soils from all over the world and includes 21 soils (all Cecil series) from the Piedmont region.

Few studies have been reported on water movement in the unsaturated zone below a couple of meters (vadose zone) in the Piedmont, despite the fact that this zone can be quite thick. One such report is that of Ligon and Wilson (1972). They installed neutron access tubes to a depth of 9.7 m near Clemson SC and monitored water contents for two years. The water table occurred at a depth of about 18 m. An extremely dry summer at the beginning of the study caused a depletion of water down to the deepest depth of measurement (9.7 m) as water drained to the water table under unsaturated conditions. The resumption of normal rainfall, supplemented by 20 cm of irrigation, produced a wetting front that moved to the deepest depth of measurement in 5.5 months. Wells showed that the wetting front arrived at the water table three weeks later, indicating faster movement at deeper depths. This may have been due to the higher water content near the water table and consequently, a higher K(q).

In bare soils, crusts or surface seals can sharply reduce infiltration rates. Peele et al. (1945) were the first to document crusting in Southern Piedmont soils noting that in two sandy loams and two sandy clay loams from South Carolina “compact, relatively impermeable surface layers formed on all soils types and these layers... were the determining factor in runoff and erosion.” Crusts form when soils are exposed to raindrop impact which disperses clay and allows a thin, dense layer to form at the surface. The clay in many of these soils will not disperse “spontaneously,” but it readily disperses with raindrop impact (Miller and Radcliffe, 1992). Water-dispersible clay was highly correlated with both runoff and soil loss in 15 agricultural topsoils of the region (Miller and Baharuddin, 1986). Surface applications of gypsum have been shown to reduce dispersion and crusting by raising the soil solution ion concentration (Miller and Scifres, 1988). Chiang et al (1993) measured crust Ks in six freshly tilled soils as they developed and found that Ks dropped sharply in the first 10 min of simulated rain (Fig. 3). After 45 minutes, Ks was less than 10 % of the initial value. Part of the effect of crusts in reducing infiltration rates is that the suction that develops beneath the crust keeps the soil in an unsaturated state.

Fig. 3. Relative hydraulic conductivity (crust conductivity divided by initial conductivity) as a function of rainfall duration for four soils in Georgia (from Chiang et al., 1993).

Macropore Effects
Macropores are large, continuous voids in soil and include structural and tillage fractures, old root channels, and earthworm and insect burrows. Suggested lower limits for macropore diameters and widths are in the 0.03 to 3.00 mm range (Beven and Germann, 1982; Luxmoore, 1981; White, 1985). Macropores are important because they can increase infiltration and may result in bypass flow of water and solutes (Bouma, 1991). Schoeneberger and Amoozegar (1990) studied macropores in a Cecil-Pacolet series and identified five types: (1) inter-ped planar voids mostly in the B horizon, (2) old root channels in the B, B/C, and C that were either filled or partially filled with clay, (3) foliation or bed planes in the B/C and C, (4) fractured planar quartz veins in the B, B/C and C, and (5) oxide coated fracture faces. They found that the minimum Ks occurred in the bottom of the B and the B/C horizons despite the presence of macropores (Fig. 2). They concluded that foliation planes and quartz veins had little effect on water flow. This was attributed to plugging by iron and manganese oxides and clay (Vepraskas et al., 1991; Williams et al., 1994).

Gupte et al. (1996) examined macropores using computed tomography and dyes in 38 columns taken from the top 50 cm or so of a Cecil soil. They found that the number of macropores decreased in the B horizon compared to the Ap and BA. Like Schoeneberger and Amoozegar (1990), they observed old root channels or burrows filled with light-colored material, but it was not possible to determine if the material was topsoil, faunal secretions, or decayed organic matter. The presence of in-filled macropores has important hydrologic implications. Since these features were dye-stained, they apparently had a higher conductivity than the surrounding soil matrix. In contrast to open macropores, entry to filled macropores would not require a positive pressure potential. Thus macropore flow might occur under unsaturated conditions. Phillips et al. (1989) showed that water could continue to flow in open macropores under slightly negative pressure potentials, provided that a continuous water film had been established on the wall over the entire length of the macropore.

Bathke and Cassel (1991) measured macroporosity in horizons of a Cecil landscape as porosity minus the water content at a pressure potential of -6.9 kPa (equivalent diameter of 0.04 mm). They found that macroporosity was the factor that showed the highest correlation with Ks at all sites.

Solute Transport
One of the unique features of soils of this region is that, to a limited extent, anions such as nitrate are adsorbed and movement consequently is retarded. Thomas (1960) demonstrated Cl adsorption in three soils from the Southern Piedmont (Cecil, Davidson, and Lloyd), but not in a Yolo soil from California. Bellini et al. (1996) used packed columns to show that anion retardation was pH and concentration dependent. In an unlimed Cecil subsoil with pH 4.26, the retardation coefficient (R) for Cl was 2.39; liming the soil to a pH of 6.56 reduced R to 1.12 (Fig. 4). The anion exchange capacity (AEC) of the unlimed soil was 1.43 cmolc kg-1 compared to 0.70 cmolc kg-1 in the limed soil. Retardation rose more slowly as the anion concentration increased above the level required to saturate the soil AEC. Anion adsorption is due to the variable charge of kaolinitic and oxide surfaces in these soils.

Fig. 4. Relationship between retardation factor (R) and subsoil pH in 0.01 M CaCl 2 . Error bars indicate 95% confidence intervals (from Bellini et al., 1996).

Chemical movement can be affected by the timing of rainfall or irrigation events. Golabi et al. (1995) demonstrated that Cl leaching was reduced in intact columns of Cecil soil when a small rain was applied immediately after application. In this treatment Cl had an opportunity to diffuse into stagnant regions of the matrix and, as a result, was excluded from flow in macropores in subsequent large rainfall events. The same effect was demonstrated earlier by Shipitalo et al. (1990) using soils from Ohio.

Often there is a need to predict soil profile leaching losses of chemicals such as nitrate at the field or regional scale, but parameters used in transport models are usually measured at the pedon or local scale (Dagan, 1986). Radcliffe et al. (1996) measured Cl transport parameters in a Cecil soil under steady flow conditions at different scales in two irrigated 12.5 by 30.5 m plots. Tile drains were used to determine field-scale transport parameters. Most of the dispersion in the tile drain breakthrough curves (BTC) was caused by two-dimensional flow to the drains. Once this effect was removed, the field-scale dispersivities ()were relatively low (5.3 and 3.4 cm for the two plots) compared to other measurements of field-scale  in the literature (3-97 cm in Biggar and Nielsen [1976], 6-29 cm in Butters and Jury [1989], and 5 to 20 cm in Jury et al. [1991]).

Local-scale pore water velocity (V) and Ks measured on 38 columns (average length of 49 cm) from one of the irrigated plots were highly variable (CV’s of 77 and 74 %, respectively) and log-normally distributed (Gupte et al., 1996). The mean local-scale  was 6.6 cm. In spite of the large variation in V among columns, a deterministic approach based on the mean local-scale  adequately predicted the field-scale tile drain BTC. This may have been because flow was predominately unsaturated in the irrigation experiment and saturated in the column experiment. In a second study (Radcliffe et al., 1997), transport parameters were measured using time domain reflectometry (TDR) waveguides installed vertically at 80 locations on one of the irrigated plots studied earlier. Field-scale  were 5.3 and 11.4 cm in the 0-30 and 0-60 cm depth intervals. The increase in  with depth was attributed to saturated conditions (the water table was at 30 cm) which caused more macropore flow in the Bt horizon. Although the variability among local-scale V was large (CV of 35% and 46% in the 0 to 30 and 0 to 60 cm depth intervals, respectively), the variability in velocities within the local-scale caused by hydrodynamic dispersion (and quantified by ) was greater. As a result, a deterministic approach based on the mean local-scale parameters more accurately predicted the estimated field-scale breakthrough curve than a stochastic approach.

In a recent study, we measured Br transport (a conservative tracer for nitrate) in intact columns from the Ap/BA and Bt1 horizons of a Pacolet pedon that had been in Bermuda grass sod for over 10 years. The pedon is shown in Fig. 5 and a morphological description is given in Table 2. One set of five columns (15-cm diameter) were extracted from the surface. Since the columns were 30 cm in length, these columns encompassed the Ap and BA horizons. The top of the Bt1 horizon was then exposed in a pit and a second set of columns were extracted. These columns were also 30 cm in length and encompassed the Bt1 horizon and approximately 5 cm of the Bt2 horizon. The columns were taken to the lab and Ks  was measured. A Br BTC was conducted and transport parameters were determined using CXTFIT (Parker and van Genuchten, 1984). Finally the columns were leached with methylene blue dye and sectioned at two depths to determine the percent dyed area. Saturated hydraulic conductivities were quite high and similar in the two horizons (Table 3). Retardation coefficients for Br (which should be similar to that for NO3 ) were lower in the Bt1 due to an increase in pH at this site. Dispersivities were low for both horizons because the fractional mobile water (qm/q) was low in this soil. There was less mobile water in the Bt1 horizon than in the Ap/BA. The dye measurements indicated that a significant portion of the soil matrix was bypassed and that more stagnant regions existed in the Bt1 than in the Ap/BA horizon.

Fig. 5. Profile of Pacolet soil.

Landscape Effects
Landscape position can have a significant effect on chemical movement in these soils. Bruce et al. (1985) applied KBr to the surface of a Cecil/Pacolet landscape at six different sites and followed the movement of Br in response to natural rainfall. Highest concentrations of Br were found in the upper Bt horizon and there appeared to be some lateral downslope movement of Br. Bathke and Cassel (1991) established sites on interfluve, shoulder, linear slope, and foot slope positions in a Cecil landscape. They measured Ks on cores sampled vertically and horizontally by horizon at each site. Horizontal Ks  were greater than vertical Ks  in most horizons in all but the foot slope position. In the footslope position, more horizons had vertical Ks greater than horizontal Ks . This implied that lateral movement of water and solute was likely in all positions except the footslope position.

Afyuni et al. (1994) surface applied Br in transects of Georgeville soil to study vertical and lateral movement under natural rainfall. Each transect included a footslope, linear slope, and interfluve landscape position. Lateral movement of Br occurred to some extent in all positions. Both vertical and lateral movement of Br were greatest in the footslope position. This was attributed to the lower clay content of the footslope position and the fact that this position received water for a longer period of time from the higher elevation positions.

Spatial Variability
Spatial variability of sorptivity was evaluated by van Es et al. (1991) in a cultivated 2.2-ha field of Georgeville soil in the Carolina Slate Belt in North Carolina. The topography of the field was complex and contained a summit, broad gently sloping interfluve with side slopes facing from north to southeast with gradients raging from 10 to 25%, and footslopes. Sorptivity (the ratio of cumulative infiltration to the square root of time during the early stage of infiltration) was measured at 290 sites in the field on three separate dates. Global semivariograms for each date had a large nugget value and a range of 12 m or less indicating a very short-range spatial dependence. Definite regions of higher and lower sorptivity were found. However, the overall variation within each region was large. Maps showing sorptivity on 5 June and 8 September 1986 as a function of the topography are shown in Fig. 6.

Fig. 6. Spatial distribution of sorptivity values on a 2.2 ha site on 5 June (dry) and 8 September (wet), 1986 (from van Es et al., 1991).

Management and Landuse Effects
Management can have a very significant effect on soil physical, chemical, and biological properties that affect water and chemical movement. Many studies on soils from other regions have shown that conservation tillage systems affect infiltration, evaporation, nutrient cycling, and chemical leaching (Bond and Willis, 1969; Edwards et al., 1988; Isensee et al., 1990; Kanwar, 1991; Triplett, et al., 1968). Conservation tillage systems have been promoted in the Piedmont region because they reduce erosion and increase water retention (Langdale et al., 1979a; Reicosky et al., 1977). Within the region, studies on Cecil and Pacolet soils have shown that infiltration rates are higher under conservation tillage because crop residues and more stable aggregates reduce crusting compared to conventional tillage (Radcliffe et al., 1988) and because there are more macropores in conservation tillage (Golabi et al., 1995). Freese et al. (1993) measured infiltration with a rainfall simulator in a Wedowee sandy clay loam in a long-term experiment with moldboard plow, disk, and no-tillage treatments. Measurements were made before tillage, immediately after tillage, two weeks after tillage, and after harvest. Infiltration was highest in the no-tillage and chisel plow treatments on all dates except immediately after tillage when the moldboard plow treatment had the highest infiltration rate.

The number of macropores is greater in conservation tillage systems than conventional systems because macropores in the tillage zone are not disrupted by annual tillage and faunal activity is greater due to the more favorable moisture and temperature regime. This has led to concern that macropores may cause accelerated leaching of groundwater contaminants such as pesticides and nitrates under conservation tillage. Some studies from other regions have found more rapid leaching of solutes in no-tillage compared to conventional tillage (Andreini and Steenhuis, 1990; Dalal, 1989; Germann et al., 1984; Isenesee et al., 1990; Zachman et al., 1987) but other studies found the reverse or no difference (Kanwar, 1991; Shipitalo and Edwards, 1993). Studies from other regions have also shown that nonlegumenous winter cover crops can reduce nitrate leaching due to their effect on nitrogen and water uptake (Meisinger et al., 1990). On a Cecil-Pacolet series, McCracken et al. (1995) found that nitrate leaching losses were not affected by tillage over a three-year period, except one summer when heavy rainfall occurred shortly after fertilization. In this case, leaching losses tended to be greater under no-tillage compared to conventional tillage. They also found that a winter cover of rye significantly reduced nitrate leaching losses.

Several studies have found that groundwater quality is affected by animal agriculture. Gould (1995) sampled 236 wells in the Little River/Rooty Creek watershed in North Georgia where there is a high concentration of dairy farms. Thirteen percent of the wells had NO3 -N concentrations above the EPA drinking standard of 10 mg L-1 . Thirty nine percent had NO3 -N concentrations above background (3 mg L-1 ). Drommerhausen et al. (1995) used ground electromagnetic conductivity measurements on nine dairies in this area to determine the source of the nitrate in the wells. They concluded that dairy loafing areas (the corrals and areas of fields where the herd stays when it is not being milked or on pasture) were the most likely source of contamination. These loafing areas were usually located close to the milking barns where the well was also located. Monitoring wells installed in the loafing areas at three of these dairies had NO3 -N concentrations between 60 and 138 mg L-1. There was evidence that NO3 -N was seeping from three of the six lagoons surveyed, but this was considered an unlikely source of the NO3 -N in the wells because the lagoons were a substantial distance down-gradient of the wells. A 15- county survey of domestic well water in Georgia in 1993 found that nitrate concentrations were higher near swine, dairy, and poultry operations (5.36, 4.12, and 3.69 mg NO3 -N  L-1 ) compared to irrigated agriculture and nonagricultural wells (2.21 and 1.44 mg NO3-N L-1 ) (Bush et al., 1997). The study included five counties in the Coastal Plain region.

Industrial landuse has also had an effect on contaminants in Piedmont soils and shallow groundwater. Christian et al. (1992) reported that as of 1989 there were eight CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act or “superfund”) sites, 49 RECRA (Resource Conservation Recovery Act) sites, and 841 contaminated sites in the Piedmont region of North Carolina. Two-thirds of these were underground storage tank (UST) leaks of petroleum products. Seventy percent of the sites were in urban settings, but on a per capita basis, rural residents were as likely as urban residents to be affected. Approximately three-quarters of the contaminated wells were residential supply wells. Various methods for remediating contaminated soil and shallow groundwater at sites in the Piedmont have been reported including in situ vapor extraction (Wisniewski, 1992; McClinton and Workentine, 1992), pump and treat (Furt, 1992; Kasper, 1992), and bioremediation (Moore, 1991).

Contamination of surface waters has received a large emphasis in recent years and several studies in the Piedmont have related contaminant levels to land use. In North Carolina, Simmons and Heath (1992) compared water quality of streams that had less than 10% of the watershed area in agriculture with that of streams with greater than 10% in agriculture. Phosphorus (P) levels were 2 to 13 times greater in storm runoff from the high agriculture watersheds. Total nitrogen (N) and P in storm runoff increased as the percent of the basin in agriculture increased. Kuykendall et al. (1996) measured soluble reactive phosphorus (SRP) in runoff from pastures in Georgia that received 10 Mg broiler litter per ha in split spring and fall applications. Concentrations of SRP reached values as high as 8 mg L-1 . This is significant considering that the EPA has established guidelines of 0.1 mg L-1 total P for streams and 0.05 mg L-1 total P for lakes. Jordan et al. (1997) compared N concentrations in 10 Piedmont and 17 Coastal Plain streams in the Chesapeake Bay area. They found that flow-weighted nitrate concentrations were consistently higher in Piedmont streams and speculated that the difference might be due to less effective filtering of nitrate in Piedmont forested riparian zones due to deep groundwater flow.

Limited research has been done on the effect of riparian buffers on stream water quality in the Piedmont. Daniels and Gilliam (1996) examined surface runoff from cultivated areas into riparian zones consisting of a grass buffer or a grass and forest buffer in North Carolina. Riparian buffers reduced total P by 50% but soluble P was reduced by only 20%. Forested ephemeral gullies transported nutrients through the riparian zone with little reduction in nutrient concentrations. Parsons et al. (1994) also examined surface runoff in grass and forested riparian zones in North Carolina. Nitrate and total N showed substantial reductions, but not soluble P. Verchot et al. (1997a and 1997b) used level spreaders that forced runoff out of ephemeral gullies in forested riparian zones, but N loads in runoff were not substantially reduced in the riparian zones. Nitrate concentrations in the subsoil dropped from 6-10 mg L-1at the edge of fields to less than 1 mg L-1 in the riparian zones. Sweeney (1993) examined a forested Piedmont watershed in Pennsylvania. The author reported limited data on N that showed springs and deep (>25 m) groundwater had relatively high NO3 -N concentrations (averaging > 7 mg L-1 ) compared to shallow (<3 m) groundwater (<0.1 mg L-1 ) and streamwater (3 mg L-1 ).

Water quality in urban streams of the Piedmont has received attention lately. Hippe and Garrett (1997) compared streamwater samples from groups of small watersheds representing the predominant land uses in the Appalachicola, Chattahoochee, and Flint river basin. Pesticides were detected most frequently and at highest concentrations in urban watersheds, followed by suburban, row crop agriculture, poultry and livestock production, and forested watersheds. Insecticides were detected at concentrations exceeding the maximum recommended level for aquatic life in urban and suburban watersheds. Pesticides with large runoff-potential ratings were the most commonly detected and had the highest concentrations. Pesticides having medium runoff potential were detected primarily in urban and suburban watersheds. This may have been due to over application or more impervious surfaces in these areas.

The Southern Piedmont is one of the larger MLRAs in the southeastern United States and we have considerable information on the major soils of this region. Parent material (felsic vs. mafic rock) is important in determining the properties of the soil and the thickness of the saprolite layer, which is an important storage zone for groundwater. Soil horizons differ sharply in texture and structure and this affects water and solute movement. Variable-charge mineralogy is common and this makes these soils dispersive at high pH and capable of adsorbing anions at low pH. Lateral movement of water and solute may occur in these soils depending on landscape position. Ground water and surface water contamination has been documented in association with livestock, industrial, and urban landuse. More information is needed on poorly drained soils that have not been important for agriculture production, but are important in urban/suburban landuse and on the transport properties of saprolite.

Literature Cited
Afyuni, M.M., D.K. Cassel, and W.P. Robarge. 1994. Lateral and vertical bromide ion transport in a Piedmont landscape. Soil Sci. Soc. Am. J. 58:967-974.

Andreini, M.S. and T.S. Steenhuis. 1990. Preferential paths of flow under conventional and conservation tillage. Geoderma 46:85-102.

Bathke, G.R. and D.K. Cassel. 1991. Anisotropic variation of profile characteristics and saturated hydraulic conductivity in an Ultisol landscape. Soil Sci. Soc. Am. J. 55:333-339.

Bellini, G., M.E. Sumner, D.E. Radcliffe, and N.P. Qafoku. 1996. Anion transport through columns of highly weathered acid soil: adsorption and retardation. Soil Sci. Soc. Am. J. 60:132-137.

Beven, K., and P. Germann. 1982. Macropores and water flow in soils. Water Resour. Res. 18:1311-1325.
Biggar, J.W. and D.R. Nielsen. 1976. Spatial variability of the leaching characteristics of a field soil. Water Resour. Res. 12:78-84.

Bond, J.J. and W.O. Willis. 1969. Soil water evaporation: surface residue rate and placement effects. Soil Sci. Soc. Am. Proc. 33:445-448.

Bouma, J. 1991. Influence of soil macroporosity on environmental quality. Adv. Agronomy. 46:1-37.

Brackett, D.A., W.M. Steele, T.J. Schmitt, R.L. Atkins, M.F. Kellam, and J.A. Lineback. 1991. Hydrogeologic data from selected sites in the Piedmont and Blue Ridge Provinces, Georgia. 86 ed. Dept. of Natural Resources, Atlanta Georgia.

Bruce, R.R., J.H. Dane, V.L. Quisenberry, N.L. Powell, and A.W. Thomas. 1983. Physical characteristics of soils in the Southern region: Cecil. Ga. Ag. Exp. Sta. Athens, Ga.

Bruce, R.R., R.A. Leonard, A.W. Thomas, and W.A. Jackson. 1985. Redistribution of bromide by rainfall infiltration into a Cecil sandy loam landscape. J. Environ. Qual. 14:439-445.

Bruce, R.R., A.W. Thomas, and F.D. Whisler. 1976. Prediction of infiltration into layered soils in relation to profile characteristics. Am. Soc. Ag. Eng. 19:693-698.

Bruce, R.R., and F.D. Whisler. 1973. Infiltration of water into layered field soils. pp. 77-89. In: A. Hadas et al. (eds.) Physical aspects of soil, water, and salts in ecosystems. Springer Publ., New York.

Bush, P.B., A.W. Tyson, R. Perkins, and W. Segars. 1997. Results of Georgia domestic well water testing program. pp. 358- 360. In: K.J. Hatcher (ed.) 1997 Georgia Water Resources Conference. University of Georgia. Athens.

Butters, G.L. and W.A. Jury. 1989. Field scale transport of bromide in an unsaturated soil 2. Dispersion modeling. Water Resour. Res. 25:1583-1589.

Cassel, D.K. 1972. In situ unsaturated hydraulic conductivity for selected North Dakota soils. North Dakota Ag. Exp. Sta. Bull. 494. Fargo.

Chiang, S.C., D.E. Radcliffe, and W.P. Miller. 1993. Hydraulic properties of surface seals in Georgia soils. Soil Sci. Soc. Am. J. 57:1418-1426.

Chiang, S.C., D.E. Radcliffe, W.P. Miller, and K.D. Newman. 1987. Hydraulic conductivity of three southeastern soils as affected by sodium, electrolyte concentration, and pH. Soil Sci. Soc. Am. J. 51:1293-1299.

Christian, B.S., E.F. Gloeckler, and S.J. Zimmerman. 1992. A survey of pollution incidents in the Piedmont of North Carolina. pp. 26-36. In: C.C. Daniel III and R.C. White (eds.). Ground water in the Piedmont. Clemson University. Clemson, South Carolina.

Cressler, C.W., C.J. Thurmond, and W.G. Hester. 1983. Ground water in the greater Atlanta region. Georgia. Dept. of Nat. Res. Atlanta.

Dagan, G. 1986. Statistical theory of groundwater flow and transport: Pore to laboratory, laboratory to formation, and formation to regional scale. Water Resour. Res. 22:120-134.

Dalal, R. 1989. Long-term effects of no-tillage, crop residue, and nitrogen application on properties of a vertisol. Soil Sci. Soc. Am. J. 53:1511-1515.

Daniels, R.B. and J.W. Gilliam. 1996. Sediment and chemical load reduction by grass and riparian filters. Soil Sci. Soc. Am. J. 60:246-251.

Daniels, R.B., J.J. Kleiss, S.W. Boul, H.J. Byrd, and J.A. Phillips. 1984. Soil systems in North Carolina. Bull. 467. North Carolina Agricultural Research Service, Raleigh.

Drommerhausen, D.J., D.E. Radcliffe, D.E. Brune, and H.D. Gunter (1995). Electromagnetic conductivity surveys of dairies for groundwater nitrate. J. Environ. Qual. 24:1083-1091.

Edwards, W.M., L.D. Norton, and C.E. Redmond. 1988. Characterizing macropores that affect infiltration into nontilled soil. Soil Sci. Scoc. Am. J. 2:483-487.

Freese, R.C., D.K. Cassel, and H.P. Denton. 1998. Infiltration in a Piedmont soil under three tillage systems. J. Soil Water Conserv. 48:214-218.

Furt III, T. 1992. Health/environmental risk analysis and in situ pilot recovery test, tools in remedial action plan development, a case study. pp. 193-205. In: C.C. Daniel III and R.C. White (eds.). Ground water in the Piedmont. Clemson University. Clemson, South Carolina.

Germann, P.F., W.M. Edwards, and L.B. Owens. 1984. Profiles of bromide and increased soil moisture after infiltration into soils with macropores. Soil Sci. Soc. Am. J. 48:237-244.

Golabi, M.H., D.E. Radcliffe, W.L. Hargrove, and E.W. Tollner. 1995. Macropore effects in conventional tillage and no-tillage soils. J. Soil and Water Conserv. 50:215-220.

Gould, M.C. 1995. Nitrate-nitrogen levels in well water in the Little River / Rooty Creek agricultural non-point source hydrological unit area. pp. 251-255. In: K. Steele (ed.). Animal waste and the land-water interface. Lewis Pub. Boca Raton, Florida.

Gupte, S.M., D.E. Radcliffe, D.H. Franklin, L.T. West, E.W. Tollner, and P.F. Hendrix. 1996. Anion transport in a Piedmont Ultisol: 2. Local-scale parameters. Soil Sci. Soc. Am. J. (In press).

Hack, J.T. 1989. Geomorphology of the Appalachian highlands. pp. 459-470. In: R.D. Hatcher, Jr., W.A. Thomas, and G.W. Viele (eds.) The Appalachian-Ouachita Orogen. Vol. F-2, The Geology of North America, Geological Society of America, Boulder, Colorado.

Holmes, C.D. 1964. Equlibrium in humid-climate physiographic processes. Am. J. Sci. 262:436-445.

Hippe, D.J. and J.W. Garret. 1997. The spatial distribution of dissolved pesticides in surface water of the Apalachicola-Chattahoochee- Flint River basin in relation to landuse and pesticide runoff-potential ratings. pp. 410-419. In: K.J. Hatcher (ed.). Georgia Water Resources Conference. 20 - 22 March 1997. University of Georgia. Athens.

Isensee, A.R., R.G. Nash, and C.S. Helling. 1990. Effect of conventional vs. no-tillage on pesticide leaching to shallow groundwater. J. Environ. Qual. 19:434-440.

Jordan, T.E., D.E. Correl, and D.E. Weller. 1997. Relating nutrient discharges from watersheds to landuse and stream flow variability. Water Resour. Res. 33:2579-2590.

Jury, W.A., W.R. Gardner, and W. H. Gardner. 1991. Soil Physics. John Wiley and Sons, Inc. New York.

Kanwar, R.S. 1991. Preferential movement of nitrate and herbicides to shallow groundwater as affected by tillage and crop production. pp. 328-335. In: T.J. Gish and A. Shirmohammadi (eds). Preferential flow. Proceedings of the National Symposium. ASAE. St. Joseph, Missouri.

Kasper, J.G. 1992. Ground water monitoring and recovery system design in a low-yield crystaline rock aquifer in western North Carolina. pp. 229-249. In C.C. Daniel III and R.C. White (eds.). Groundwater in the Piedmont. Clemson University. Clemson, South Carolina.

Kuykendall, H.A., M.L. Cabrera, C.S. Hoveland, M.A. McCann, L.T. West, D.D. Radcliffe, and D.V. McCracken. 1996. Nutrient utilization and runoff in pastures fertilized with broiler litter. p. 338. Agronomy Abstracts. American Society of Agronomy. Madison Wisconsin.

Langdale, G.W., A.P. Barnett, R.A. Leonard, and W.G. Fleming. 1979a. Reduction of soil erosion by the no-till system in the southern Piedmont. Transactions of the ASAE 22:82-86.

LeGrand, H.E. 1988. Region 21, Piedmont and Blue Ridge. pp. 201-208. In: W. Back, J.S. Rosenshein and P.R. Seaber (eds.). Hydrogeology. Geological Society of America, Boulder, Colorado.

Leij, F.J., W.J. Alves, M.Th. van Genuchten, and J.R. Williams. 1994. Unsaturated soil hydraulic database UNSODA 1.0 user’s manual. R.S. Kerr Environmental Research Laboratory. U.S. EPA. Ada, Oklahoma.

Ligon, J.T. and T.V. Wilson. 1972. Deep seepage on Piedmont watersheds. Water Resources Research Institute. Clemson University. Clemson, South Carolina.

Luxmoore, R.J. 1981. Micro-, meso-, and macroporosity of soil. Soil Sci. Soc. Am. J. 45:671.

Macedo, R. and R.B. Bryant. 1987. Morphology, mineralogy, and genesis of a hydrosequence of Oxisols in Brazil. Soil Sci. Soc. Am. J. 51:690-698.

Macedo, R. and R.B. Bryant. 1989. Preferential microbial reduction of hematite over goethite in a Brazilian Oxisol. Soil Sci. Soc. Am. J. 53:1114-1118.

McClinton, R.G. and R.A. Workentine. 1992. Retrofitting new and existing ground water recovery wells to expedite removal of petroleum products trapped in the unsaturated zone. pp. 206-215. In: C.C. Daniel III and R.C. White (eds.). Ground water in the Piedmont. Clemson University. Clemson, South Carolina.

McCracken, D.V., J.E. Box, Jr., W.L. Hargrove, M.L. Cabrera, J.W. Johnson, P.L. Raymer, A.D. Johnson, and G.W. Harbers. 1995. Nitrate leaching as affected by tillage and winter cover cropping. pp. 26-30. In: Proc. 1995 Southern Conservation Tillage Conference for Sustainable Agriculture. 26-28 June 1995. Mississippi State University. Jackson.

McVay, K.A. and D.E. Radcliffe. 1998. Comparison of indirect and instantaneous profile methods for estimating unsaturated hydraulic conductivity. In: F.J. Leij and M.Th. van Genuchten (ed.). Workshop on characterization and measurement of the hydraulic properties of unsaturated porous media. 27 - 31 October 1997. U.S. Salinity Laboratory. Riverside, California. (In press).

Meisinger, J.J., P.R. Shipley, and A.M. Decker. 1990. Using winter cover crops to recycle nitrogen and reduce leaching. pp. 3-7. In: J.P. Mueller (ed.). Proc. southern conservation tillage conference. North Carolina State Univ. Raleigh.

Miller, W.P. and D.E. Radcliffe. 1992. Soil crusting in the southeastern United States. pp. 233-266. In: M.E. Sumner and B.A. Stewart (eds.). Soil crusting: Chemical and physical processes. Lewis Publishers. Boca Raton, Florida.

Miller, W.P. and J. Scifres. 1988. Effect of sodium nitrate and gypsum on infiltration and erosion of a highly weathered soil Soil Sci. 145:304-309.

Miller, W.P. and M.K. Baharuddin. 1986. Relationship of soil dispersibility to infiltration and erosion of southeastern soils. Soil Sci. 142:235-240.

Moore, R.E. 1991. Construction and operation of a biotreatment facility for remediation of hydrocarbon contaminated soil. pp. 333-336. In: K.J. Hatcher (ed.). 1991 Georgia Water Resources Conference Proceedings. University of Georgia. Athens.

Murray, G.E. 1961. Geology of the Atlantic and Gulf Coastal province of North America. Harper and Brothers NY.

Parker, J.C. and M.Th. van Genuchten. 1984. Determining transport parameters from laboratory and field tracer experiments. Virginia Ag. Exp. Sta. Bull. 84-3. Blacksburg.

Parsons, J.E., J.W. Gilliam, R. Munoz-Carpena, R.B. Daniels, and T.A. Dillaha. 1994. Nutrient and sediment removal by grass and riparian buffers. In: F.K. Campbell, W.D. Graham and A.B. Bottcher (eds.). Environmentally sound agriculture. Proc. of the second conference. 20-22 April 1994. Orlando, Florida.

Pavich, M.J. 1985. Appalachian Piedmont morphogenesis: Weathering, erosion, and Cenozic uplift. pp. 299-319. In: M. Morisawa and J.T. Hack (eds.). Tetonic geomorphology. Proc. 15th Annual Binghamton Geomorphology Symp., Boston.

Pavich. M.J. 1986. Processes and rates of saprolite production and erosion on a foliated granitic rock of the Virginia Piedmont. pp. 551-590. In: S.M. Coleman and D.P. Dethier (eds.). Rates of chemical weathering of rocks and minerals. Academic Press, New York.

Pavich, M.J., G.W. Leo, S.F. Obermeier, and J.R. Estabrook. 1989. Investigations of the characteristics, origin, and residence time of the upland residual mantle of the Piedmont of Fairfax County, Virginia. USGS professional paper 1352, U.S. Govt. Print. Off., Washington, DC.

Peele, T.C., E.E. Latham, and O.W. Beale. 1945. Relation of the physical properties of different soil types to erodibility. S.C. Agric. Exp. Stn. Bull. 357. Clemson University, Clemson, South Carolina.

Phillips, R.E., V.L. Quisenberry, J.M. Zeleznik, and G.H. Dunn. 1989. Mechanism of water entry into simulated macropores. Soil Sci. Soc. Am. J. 53L:1629-1635.

Radcliffe, D.E., S.M. Gupte, and J.E. Box. 1997. Solute transport at the pedon and polypedon scales. Nutrient cycling in agroecosystems. (In press).

Radcliffe, D.E., P.M. Tillotson, P.F. Hendrix, L.T. West, J.E. Box, and E.W. Tollner. 1996. Anion transport in a Piedmont Ultisol: 1. Field-scale parameters. Soil Sci. Soc. Am. J. 60:755-761.

Radcliffe, D.E.., E.W. Tollner, W.L. Hargrove, R.L. Clark, and M.H. Golabi. 1988. Effect of tillage practices on infiltration and soil strength of a Typic Hapludult soil after 10 years. Soil Sci. Soc. Am. J. 52:798-804.

Radcliffe, D.E., L.T. West, G.O. Ware, and R.R. Bruce. 1990. Infiltration in adjacent Cecil and Pacolet soils. Soil Sci. Soc. Am. J. 54:1739-1743.

Radtke, D.B., C.W. Cressler, H.A. Perlman, H.W. Blanchard, Jr., K.W. McFadden, and R. Brooks. 1986. Occurence and availability of ground water in the Athens region, northeastern Georgia. U.S. Geological Survey. Doraville, Georgia.

Reicosky, D.C., D.K. Cassel, R.L. Blevins, W.R. Gill, and G.C. Naderman. 1977. Conservation tillage in the Southeast. J. Soil and Water Conserv. 32:13-19.

Rose, S. 1992. Tritium in ground water of the Georgia Piedmont: Implications for recharge and flow paths. Hydrological Processes. 6:67-78.

Schoeneberger, P. And A. Amoozegar. 1990. Directional saturated hydraulic conductivity and macropore morphology of a soil-saprolite sequence. Geoderma 46:31-49.

Shipitalo, M.J. and W.M. Edwards. 1993. Seasonal patterns of water and chemical movement in tilled and no-till column lysimeters. Soil Sci. Soc. Am. J. 57:218-223.

Shipitalo, M.J., W.M. Edwards, W.A. Dick, and L.B. Owens. 1990. Initial storm effects on macropore transport of surface-applied chemicals in no-till soil. Soil Sci. Soc. Am. J. 54:1530-1536.

Simmons, C.E. and R.C. Heath. 1992. Water-quality characteristics of streams of forested and rural areas of North Carolina. Geological Survey Water-Supply Paper 2185.

Stolt, M.H., J.C. Backer, and T.W. Simpson. 1993. Soil-landscape relationships in Virginia: II. Reconstruction analysis and soil genesis. Soil Sci. Soc. Am. J. 57:422-428.

Sweeney, B.W. 1993. Effects of streamside vegetation on macroinvertebrate communities of White Clay Creek in Eastern North America. Proc. of the Academy of Natural Sciences of Philadelphia. 144:291-340.

Thomas, G.W. 1960. Effects of electrolyte imbibition upon cation-exchange behavior of soils. Soil Sci. Soc. Am. P. 24:329- 332.

Thornbury, W.D. 1965. Regional geomorphology of the United States. John Wiley and Sons, Inc., New York.

Trimble, S.W. 1974. Man-induced soil erosion on the Southern Piedmont. Soil and Water Conservation Society, Ankeny, Iowa.

Triplett, G.B., Jr., D.M. van Doren, Jr., and B.L. Schmidt. 1968. Effect of corn (Zea Mays L.) stover mulch on no-tillage corn yield and water infiltration. Agronomy J. 60:236-239.

USDA. 1981. Land Resource Regions and Major Land Resource Areas of the United States. p. 98. United States Department of Agriculture Soil Conservation Service Handbook 296. Dec. 1981.

van Es, H.M., D.K. Cassel, and R.B. Daniels. 1991. Infiltration variability and correlations with surface soil properties for an eroded Hapludult. Soil Sci. Soc. Am. J. 55:386-392.

van Genuchten, M.Th. and F.J. Leij. 1992. On estimating the hydraulic properties of unsaturated soils. pp. 3-14. In: M. Th. van Genuchten and F.J. Leij (eds.). Indirect methods for estimating the hydraulic properties of unsaturated soils. U.S. Salinity Laboratory. Riverside, California.

Vepraskas, M.J., M.T. Hoover, and J. Bouma. 1991. Sampling strategies for assessing hydraulic conductivity and water conducting voids in saprolite. Soil Sci. Soc. Am. J. 55:165-170.

Vepraskas, M.J., A.G. Jongmans, M.T. Hoover, J. Bouma. 1991. Hydraulic conductivity of sparolite as determined by channels and porous groundmass. Soil Sci. Soc. Am. J. 55:932-938.

Verchot, L.V., E.C. Franklin, and J.W. Gilliam. 1997a. Nitrogen cycling in Piedmont vegetated filter zones: I. Surface soil processes. J. Environ. Qual. 26:327-336.

Verchot, L.V., E.C. Franklin, and J.W. Gilliam. 1997b. Nitrogen cycling in Piedmont vegetated filter zones: II. Subsurface nitrate removal. J. Environ. Qual. 26:337-347.

White, R.E. 1985. The influence of macropores on the transport of dissolved and suspended matter through soil. Adv. Soil Sci. 2:95-119.

Williams, J.P., M.J. Vepraskas, and M.T. Hoover. 1994. Quartz vein impact on hydraulic conductivity and solute transport through quartz-phylitte saprolite. J. Environ. Qual. 23:202-207.

Wisniewski, R.D. 1992. Using in situ soil vapor extraction to remediate vadose zone soil contamination. pp. 185-192. In: C.C. Daniel III and R.C. White (eds.). Ground water in the Piedmont. Clemson University. Clemson, South Carolina.

Zachman, J.E., D.R. Linden, and C.E. Clapp. 1987. Macroporous infiltration and redistribution as affected by earthworms, tillage, and residue. Soil Sci. Soc. Am. J. 51:1580-1586.

Return to Home Page
Home Page SAAESD
Electronic document prepared by:
D.L. Nofziger, Oklahoma State University
Email address: