MLRA 116A Ozark Highlands H.D. Scott1 and L.B. Ward2 1University of Arkansas and 2USDA-NRCS, Little Rock
Location The Ozark Highlands major land resource area (MLRA 116A) covers approximately 69,810 km 2 in northern Arkansas, southern Missouri, and northeastern Oklahoma (USDA-SCS, 1981). According to the digital MLRA data the Ozark Highlands covers about 24,566 km2 or 6.07 million acres in Arkansas.
Climate The annual precipitation in MLRA 116A ranges from 1,025 to 1,225 mm. Maximum rainfall occurs in the spring and early summer, while minimum rainfall occurs in midsummer. The average annual air temperature is between 13oC and 16oC. Average freeze-free period is 180 to 200 days. Rainfall during the summer is usually inadequate which leads to drought-stressed crops and pastures. Domestic water supplies are found in shallow wells and springs. Deep wells supply larger, yet hard quantities of water. Large reservoirs provide a source of drinking water, flood control, and recreation. Small farm ponds supply livestock with water.
Geology, Elevation and Topography The Ozark Highlands consist of dissected plateaus and narrow valleys with steep gradients. It is part of the Ozark Plateau, which is a portion of the Ozark dome centered in southeastern Missouri, where Precambrian igneous rocks have been pushed upward (Guccione, 1993). It is surrounded by Paleozoic sedimentary rocks that dip gently toward the southwest. The lithology of the Ozark Plateau is characterized mostly by horizontal bedding of the lithologic units with minor folding and faulting. The Springfield Plateau portion is mostly composed of Mississippian-age sandstones, limestones, and shales. The Salem Plateau portion is a mixture of Devonian-age sandstone and shale and Ordovician-age sandstone and dolomite. Elevation ranges from approximately 200 m to about 500 m.
The topography and dendritic drainage that resulted from weathering and erosion are due to the horizontal bedding of the rocks. The Salem Plateau is relatively flat to dissected and is underlain by the nearly horizontal Ordovician-age carbonate rocks and is mostly in north-central Arkansas. The Springfield Plateau is relatively flat to highly dissected and is underlain by nearly horizontal Mississippian-age carbonates and occurs in northwestern and north-central Arkansas. Both of these plateaus are separated from the adjacent plateau by a steep slope.
Landuse Approximately 20% of the Ozark Highlands is used for pasture, 10% for cropland and 70% is forestland. Crops grown in this area include corn, feed grains, and hay for livestock and dairy cattle. Dominant natural vegetation includes oak-hickory and oak-hickory-pine forests. Dominant vegetation in the glades include mainly indian grass, little bluestem, and dropseed. Major landuse problems are attributed to summer droughts, steep slopes, and shallow soils.
The temporal and spatial changes in landuse from 1965 to 1992 in the Buffalo National River Watershed were quantified by Scott and Udouj (1999) using GIS techniques. The Buffalo River was established as the first national river in 1972. During this 27-year period, approximately 40,000 ha of forest were lost and converted primarily to pasture. The average rate of loss of forest was 1480 ha/year. During this same period, the average rate of gain of pasture was 1381 ha/yr. Buffer analyses showed that pasture increased at a higher percentage rate in the buffer zone surrounding the Buffalo River than in the tributaries, and a large proportion of the increase occurred on higher slopes. The cleared forest lands were mostly near older pastures and along streams. The reforested lands tended to occur in the more isolated areas. These dynamic changes in landuse have had impact on the water quality of some of the streams in the watershed (Mott and Steele, 1991; Mott, 1997).
Soils The soils of the Ozark Highlands developed mainly from limestone and dolomite and range from very deep to shallow in depth. The most productive soils occur on nearly level to gently sloping plateaus and along narrow stream valleys and are used for orchards, pasture, and small areas of row crops. The more mountainous areas have slopes that range from moderately sloping to very steep. Some of the less sloping areas are used for pasture production with steeper areas remaining in hardwood timber. STATSGO soils for this MLRA are provided in Fig. 1. Selected characteristics of dominant soils are given in Table 1. Descriptions of the dominant soil associations in Arkansas are given on the following pages.
1) CLARKSVILLE-NIXA-NOARK These soils occur on ridge tops and side slopes of the Springfield Plateau. The soils formed in residuum from cherty limestone. They tend to be very deep, somewhat excessively drained, moderately well drained, and well drained, moderately rapidly permeable, very slowly permeable and moderately permeable, gently sloping to very steep, very gravelly, loamy and clayey soils on uplands. Approximately 35% of this soil association is Clarksville soils; about 20% Nixa soils; about 20% Noark soils; and the remaining 25% is soils of minor extent. The minor soils in this unit include Britwater, Peridge, Captina, Tonti, Elsah, Razort, and Secesh. The soils of this association are used mainly for woodland and pasture.
The somewhat excessively drained, moderately rapidly permeable Clarksville soils typically have a grayish brown, very gravelly silt loam surface layer and a pale brown, very gravelly silt loam subsurface layer (Table 2). The upper part of the subsoil is light yellowish brown and strong brown, very gravelly silty clay loam and the lower part is yellowish red, very gravelly silty clay. The moderately well drained, very slowly permeable Nixa soils typically have a very dark grayish brown, very gravelly silt loam surface layer and a brown, very gravelly silt loam subsurface layer. The upper part of the subsoil is light yellowish brown, very gravelly silt loam and the middle part is a compact and brittle, yellowish brown very gravelly silt loam fragipan. The lower part is yellowish red, mottled very gravelly silty clay loam. The well drained, moderately permeable Noark soils typically have a dark grayish brown, very gravelly silt loam surface layer and a brown or pale brown, very gravelly silt loam subsurface layer. The upper part of the subsoil is yellowish red, very gravelly silty clay loam and the lower part is red and dark red, very gravelly clay.
2) GEPP-DONIPHAN-GASSVILLE-AGNOS These soils occur on ridges and side slopes of the Salem Plateau. The soils formed mainly in residuum from cherty dolomite. They tend to be very deep, deep and moderately deep, well drained, moderately permeable and very slowly permeable, gently sloping to steep, very gravelly, clayey soils on uplands. Approximately 30% of this unit is Gepp soils; about 15% Doniphan soils; about 10% Gassville soils; about 10% Agnos soils; and the remaining 35% is soils of minor extent. The minor soils in this unit include Arkana, Captina, Elsah, Healing, Moko, Nixa, Peridge, Razort, and Sturkie. The soils in this association are used mainly for woodland and pasture.
The very deep, moderately permeable Gepp soils typically have a brown very gravelly silt loam surface layer. The upper part of the subsoil is yellowish red, gravelly silty clay loam. The middle part is red clay and the lower part is red, mottled gravelly clay. The very deep, moderately permeable Doniphan soils typically have a dark grayish brown, very gravelly silt loam surface layer and light yellowish brown, very gravelly silt loam subsurface layer. The upper part of the subsoil is red, mottled clay and the lower part is red and brownish yellow clay. The moderately deep very slowly permeable Gassville soils typically have a dark brown, very gravelly silt loam surface layer and yellowish brown very gravelly silt loam subsurface layer. The upper part of the subsoil is strong brown, very gravelly silt loam and the middle part is yellowish red, gravelly clay and clay. The lower part is red and yellowish brown, clay underlain by soft dolomite bedrock. The deep, very slowly permeable Agnos soils typically have a very dark grayish brown, very gravelly silt loam surface layer and pale brown, gravelly silt loam subsurface layer. The upper part of the subsoil is strong brown clay and the lower part is yellowish brown, mottled clay. This is underlain by soft dolomite bedrock.
3) ARKANA-MOKO These soils occur on ridges and sideslopes of the Springfield and Salem Plateaus. The soils formed in residuum from cherty limestone and cherty dolomite. Moderately deep and shallow, well drained, very slowly permeable and moderately permeable, gently sloping to very steep, very gravelly and very stony, clayey and loamy soils on uplands. Approximately 35% of this unit Arkana soils; about 25% Moko soils; and the remaining 40% is soils of minor extent. The minor soils in this unit include Clarksville, Doniphan, Elsah, Gassville, Gepp, Nixa, Noark, Razort, and Ventris. The soils in this association are used mainly for woodland and range.
The moderately deep, very slowly permeable Arkana soils typically have a very dark grayish brown, very gravelly silt loam surface layer and dark brown and brown, very gravelly silt loam subsurface layers. The upper part of the subsoil is yellowish red, very gravelly silt loam and the middle part is yellowish red, gravelly clay. The lower part is dark yellowish brown, clay underlain by hard, dolomite bedrock. The shallow, moderately permeable Moko soils have a very dark brown, very stony silt loam surface layer and a very dark grayish brown, very stony silt loam subsurface layer. This is underlain by hard, limestone or dolomite bedrock.
4) CAPTINA-NIXA-TONTI These soils occur on broad uplands of the Springfield Plateau. The soils formed in residuum from cherty limestone. Very deep, moderately well drained, slowly permeable and very slowly permeable, nearly level to moderately sloping, gravelly, loamy soils on uplands. The minor soils in this association include Britwater, Cherokee, Clarksville, Elsah, Jay, Noark, Peridge, Razort, Secesh, and Taloka. The soils of this association are used mainly for pasture, vineyards, orchards, vegetable crops, and grains.
Approximately 30% of this unit is Captina soils; about 20% Nixa soils; and 15% Tonti soils; and the remaining 35% is soils of minor extent. The slowly permeable Captina soils typically have a brown silt loam surface layer. The upper part of the subsoil is yellowish brown silt loam and silty clay loam. The middle part is a compact and brittle, yellowish brown and yellowish red, mottled, silty clay loam and gravelly silty clay loam fragipan and the lower part is yellowish brown, mottled, extremely gravelly clay and dark red very gravelly clay. The very slowly permeable Nixa soils have a very dark grayish brown, very gravelly silt loam surface layer and a brown, very gravelly silt loam subsurface layer. The upper part of the subsoil is light yellowish brown, very gravelly silt loam and the middle part is a compact and brittle, yellowish brown, mottled, very gravelly silt loam fragipan. The lower part is yellowish red, mottled very gravelly silty clay loam. The slowly permeable Tonti soils typically have a brown, gravelly silt loam surface layer. The upper part of the subsoil is yellowish brown, gravelly silt loam and gravelly silty clay loam and the middle part is a compact and brittle light yellowish brown, mottled, very gravelly silt loam fragipan. The lower part is red and dark red, very gravelly clay.
5) CAPTINA-DONIPHAN-GEPP These soils occur on broad, rolling uplands of the Salem Plateau. The soils formed in residuum from cherty dolomite. They tend to be very deep, moderately well drained and well drained, slowly permeable and moderately permeable, nearly level to moderately steep, gravelly, loamy and clayey soils on uplands. Approximately 35% of this unit is Captina soils; about 25% Doniphan soils; about 25% Gepp soils; and the remaining 20% is soils of minor extent. The minor soils in this unit include Arkana, Brocket, Clarksville, Gassville, Moko, Nixa, Tonti, and Ventris. The soils in this association are used mainly for pasture, small grains, and woodland.
The moderately well drained, slowly permeable Captina soils typically have a brown, silt loam surface layer. The upper part of the subsoil is yellowish brown, silt loam and silty clay loam. The middle part is a compact and brittle, yellowish brown and yellowish red, mottled, silty clay loam and cherty, silty clay loam fragipan and the lower part is yellowish brown, mottled, extremely cherty clay and dark red, very cherty clay. The well drained, moderately permeable Doniphan soils typically have a dark grayish brown, very cherty silt loam surface layer and light yellowish brown very cherty silt loam subsurface layer. The upper part of the subsoil is yellowish red, cherty silty clay loam. The middle part is red clay and the lower part is red, mottled, cherty clay. The well drained, moderately permeable Gepp soils typically have a brown, very gravelly silt loam surface layer. The upper part of the subsoil is yellowish, red very gravelly silty clay loam and the lower part is red clay and gravelly clay.
6) EDEN-NEWNATA-MOKO These soils occur on sideslopes of the Boston Mountains escarpment and on adjacent valley floors. The soils formed in residuum from interbedded calcareous shale and limestone. These soils tend to be deep, moderately deep and shallow, well drained, slowly permeable and moderately permeable, gently sloping to very steep, flaggy and stony, loamy and clayey soils on uplands. Approximately 25% of this unit is Eden soils; about 20% Newnata soils; about 15% Moko soils; and the remaining 40% is soils of minor extent. The minor soils in this unit include Enders, Samba, and Summit. The soils of this association are used mainly for woodland and pasture.
The moderately deep, slowly permeable Eden soils typically have a brown flaggy silty clay loam surface layer. The upper part of the subsoil is light olive brown silty clay and the lower part is light olive brown, flaggy or channery silty clay. This is underlain by soft, fractured interbedded calcareous shale and limestone. The deep, slowly permeable Newnata soils typically have a very dark grayish brown, stony silt loam surface layer. The upper part of the subsoil is dark yellowish brown flaggy clay loam and the middle part is strong brown, silty clay loam. The lower part is strong brown, mottled clay. The is underlain with soft, weathered platy shale and limestone. Below this is hard, limestone bedrock. The shallow, moderately permeable Moko soils typically have a very dark brown, very stony silty clay loam surface layer and a very dark grayish brown, very strong silty clay loam subsurface layer. This is underlain by hard, limestone or dolomite bedrock.
7) ESTATE-PORTIA-MOKO Very deep, deep and shallow, well drained, slowly permeable, and moderately permeable gently sloping to very steep, clayey and loamy soils on uplands. These soils are on sideslopes and footslopes of the Salem Plateau and were formed in residuum and colluvium form interbedded sandstone and limestone. Approximately 20% of this unit is Estate soils; about 20% Portia soils; about 15% Moko soils; and the remaining 45% is soils of minor extent. The minor soils in this unit include Arkana, Brockwell, Boden, Captina, Clarksville, Lily, Noark, Ramsey, Razort, Wallen, and Wideman. The soils in this unit are mainly used for woodland and pasture.
The deep, slowly permeable Estate soils typically have a dark grayish brown stony sandy loam surface layer and a yellowish brown stony sandy loam subsurface layer. The upper part of the subsoil is yellowish red sandy loam and clay loam and the lower part is red clay. This is underlain by hard, limestone or sandstone bedrock. The very deep, moderately permeable Portia soils typically have a brown sandy loam surface layer. The upper part of the subsoil is dark brown and reddish brown loam and the middle part is yellowish red and red loam. The lower part is red clay. The shallow, moderately permeable Moko soils typically have a very dark gray very stony loam surface layer and a very dark grayish brown very stony loam subsurface layer. This is underlain by hard, limestone bedrock.
8) BROCKWELL-BODEN-PORTIA Very deep, well drained, moderately and moderately slowly permeable, gently sloping to moderately steep, loamy soils on uplands. These soils are on broad uplands of the Salem Plateau and were formed in residuum dominantly from sandstone. Approximately 40% of this unit is Brockwell soils; about 25% Boden soils; about 15% Portia soils, and the remaining 20% is soils of minor extent. The minor soils include Agnos, Captina, Estate, Lily, Ramsey, and Wideman. The soils in this unit are mainly used for pasture and woodland.
The moderately permeable Brockwell soils typically have a grayish brown fine sandy loam or gravelly fine sandy loam surface layer and a brown sandy loam or gravelly sandy loam subsurface layer. The upper part of the subsoil is brown sandy loam and the middle part is strong brown and pale brown fine sandy loam. The lower part is mottled yellowish red, brown and red sandy clay loam. The moderately slowly permeable Boden soils typically have a brown sandy loam or gravelly sandy loam surface layer and a strong brown sandy loam or gravelly sandy loam subsurface layer. The upper part of the subsoil is yellowish red sandy clay loam and the middle part is red sandy clay. The lower part is red and yellowish brown sandy clay loam and mottled, red, yellowish red and yellowish brown fine sandy loam. This is underlain by hard, sandstone bedrock. The moderately permeable Portia soils typically have a brown sandy loam surface layer. The upper part of the subsoil is dark brown and reddish brown loam and the middle part is yellowish red and red loam. The lower part is red clay. Most soils in the Ozark Highlands region are somewhat excessively drained to well drained. Dominant soils belong to Udults and Udalfs (Table 1). These soils are very deep, to shallow to medium to fine textured, cherty soils that weathered from limestone, dolomite and sandstone. The Udults and Udalfs have mesic temperature regimes, an udic moisture regime, and a siliceous or mixed mineralogy. Other common soils are Paleudults, Paleudalfs, Fragiudults, Hapludolls, Udifluvents, Hapludalfs and Hapludults. Example pedon descriptions for the Nixa, Captina, and Clarksville soils are given in Tables 2, 3, and 4, respectively.
Water and Solute Movement The ability of the soils of the Ozark Highlands to transport water and solutes affects the renovation of domestic wastes and transport of contaminants in and through the soil profile. We discuss the results of several research studies conducted on soils found in MLRA 116A.
Soil physical properties are important factors in determining the proper design and operation of septic systems. Systems that function as designed allow for hydrologic recharge with renovated wastewater. Ransom et al. (1981) examined the suitability of soil survey criteria for soil evaluation for septic filter fields. The mapping units of Peridge silt loam, Nixa cherty silt loam and Clarksville cherty silt loam were chosen because they cover large areas in northwest Arkansas, are rapidly being developed for housing, and have either moderate or severe limitations for septic filter fields. A percolation test was made at each site according to the specifications of the Arkansas Department of Health (ADH) and the United States Public Health Service (USPHS). Of the Peridge unit pedons, 50% were rated moderate and 50% severe by Soil Conservation Service (SCS) criteria, 79% passed ADH criteria, and 86% passed USPHS criteria. All Nixa unit pedons were classified as Nixa and similar soils, all were rated severe by SCS criteria, and all failed ADH and USPHS criteria. The Clarksville unit contained 85% Clarksville and similar soils. All pedons in the Clarksville unit were rated severe by SCS criteria, and 62% failed ADH and USPHS criteria. Ransom et al. (1981) suggested that soil mapping units be evaluated by their range in soil properties and by their suitability for use and management in two independent steps.
Wilson (1986) examined two septic systems installed in a Captina silt loam having a fragipan at the 66 cm depth. The two systems were a single line source system with effluent applied by gravity and three parallel line source systems with effluent applied by pressure. Tensiometers were used to measure the temporal and spatial distributions of soil water pressure. The spatial dependence associated with both septic systems was anisotropic with the greatest semi-variance in the vertical direction and smallest in the horizontal direction. Perched ground water mounds were found above the fragipan underneath both septic systems. The height of the perched water mound was highest during the wetter spring months and dissipated during the dry summers. The mound was restricted to below the 110 cm depth and within 1 m lateral distance from the seepage bed center in the fall. For both septic systems, steady-state hydraulic conditions existed from the initiation of monitoring to the end of data collection.
Paetzold (1976) conducted batch studies in the laboratory to characterize sorption and field studies to determine the transport of the herbicide metribuzin in the Captina soil. An important feature of the soil at the site is the presence of a fragipan at depths ranging from 50 to 100 cm. Linear, Freundlich, and Langmuir equilibrium models were used to evaluate sorption of metribuzin under equilibrium conditions. The model constants were found from non-linear regression of the amount sorbed S vs. the equilibrium solution concentration C. The sorption distribution coefficients (Kd) of the linear sorption model, obtained from the slopes of the least-squares fitted lines, were 0.46 and 0.18 for the Captina Ap and B2t horizons, respectively (Table 5). These relatively low Kd values indicated that more metribuzin was present in the solution phase than in the adsorbed phase and suggested that metribuzin should be relatively mobile in the Captina soil. The Kd for the Ap horizon was 2.5 times larger than that for the B2t horizon, even though the latter horizon contained more clay and had a higher cation exchange capacity (CEC). However, the Ap horizon contained approximately twice as much organic matter as the B2t; values of Kd have been shown to be highly correlated with organic matter. The exponent N of the Freundlich equation was 1.04, and 0.85 for the Ap and B2t horizons of the Captina soil, respectively (Table 5). According to the Langmuir model the maximum sorption of metribuzin was -899, and 28.95 mg ml-1 in the Ap and B2t horizons, respectively. Since the negative value is physically impossible, the Langmuir sorption isotherm cannot be used to describe adequately the sorption data. Paetzold (1976) concluded that sorption of metribuzin at concentrations normally encountered in soils could be best described by the Freundlich equilibrium model.
In the field, the redistribution of water, chloride, and metribuzin, broadcast applied to the Captina soil under maximum leaching conditions and two soil water regimes was determined (Paetzold, 1976). The largest metribuzin concentrations were detected near the soil surface, however, significant quantities were found at the top of the fragipan. Metribuzin and chloride generally moved in the same direction as soil water but at considerably slower rates. Persistence of metribuzin within the soil profile was influenced by microbial degradation. Based upon mass balances, the half lives were 7.9 and 5.1 days in the grass vegetative and mulched plots, respectively. The differences in the half lives were attributed to differences in landuse and subsequent effects of soil temperature and soil water status.
Wood et al. (1987) measured the spatial variability of Kd for the herbicide metolachlor and correlated these Kd values to soil properties. This study was conducted in a 3 ha field on Captina and Johnsburg silt loams. The area used for this study was established on a grid coordinate system resulting in 135 sampling locations. Soil analyses were conducted to characterize the variability of pH, particle size analysis, organic matter content, and water retention. The values of Kd were divided by the organic carbon content to calculate the adsorption parameter Koc. Multiple linear regression analyses were also performed to determine the correlations between Kd and the soil properties. The soil physical properties for the Captina study area are summarized in Table 6. The least variable soil property was pH with CV values of 10.2, 11.2, and 12.1% for the Ap, Bt, and Btx horizons, respectively. Organic matter content was the most variable soil property with CV values of 37.5, 44.6, and 49.6% for the Ap, Bt, and Btx horizons, respectively. The metolachlor adsorption parameters Kd and Koc for the three soil horizons are also summarized in Table 6. Mean values of Kd were 1.75 m3 kg-1 for the Ap horizon and 0.76 m3 kg-1 for the Bt and Btx horizons. Mean values of Koc were 211, 320, and 467 m3 kg-1 for the Ap, Bt, and Btx horizons, respectively. Soil organic matter content was the soil characteristic most highly correlated with the sorption of metolachlor. For the Ap horizon, the correlation coefficient between these two properties was 0.925. Sorption of metolachor in the Ap horizon was also positively correlated to water retained at 1500 kPa and textural composition. Multiple regression analysis yielded an R2 of 0.856 for the model containing organic matter alone and only 0.861 for the model containing all soil physical properties. These results suggest that organic matter is the soil property most responsible for the adsorption of metolachlor in the Ap horizon of the Captina soil. For the Bt horizon, the highest correlation coefficient was also organic matter content, R2 = 0.52. Kd was negatively correlated with pH and water retention at 1500 kPa. Multiple regression did not significantly improve the R2 when all properties were considered over the R2 with organic matter alone.
Thiesse (1984) conducted a detailed soil hydraulic characterization study on six in situ hydraulic conductivity plots on a Captina silt loam. Some of the results are reported in Southern Regional Bulletin 264 (Romkens et al., 1986). Changes in hydraulic conductivity with soil water content were greater in the fragipan than in non-fragipan horizons. This variability in the Bx horizon was attributed to the wavy boundary, structure, and thickness of the fragipan and not to textural composition. The statistical variability of the 18 soil physical properties of Captina soils was quantified using a mixed model with depth within the profile, plots within area, and area (or location) as the components of the model. At the 5% probability level, all soil properties were significantly variable for plots within an area. No additional significant variability was found due to area.
Sauer et al. (1998) characterized several soil surface properties at varying landscape positions in the Ozark Highlands. Sampling transects were established from a riparian forest to an adjacent ridge top in five soil mapping units at 3-m intervals. Using multi-linear regression techniques the CEC was related to as follows: CEC = -1.43 + 0.68(% clay) + 1.34 (% carbon) with an R2 = 0.60. Soil samples taken from each transect had similar silt contents but the soil in the riparian forest had more clay and significantly less sand and coarse fragments. The ponded infiltration rates decreased with distance from the river. Infiltration for the Razort soil in the riparian forest was not significantly higher than either of the upland soils (Captina and Nixa), which was attributed to the large variations in filtration due to rodent and earthworm burrows. Coefficients of determination of the regressions of infiltration rate vs. soil physical properties were low. The soils with higher percentages of coarse fragments had higher saturated hydraulic conductivities (Ksat) but coefficients of determinations of the regressions of Ksat with coarse fragments were low.
Scott et al. (1995) examined the fate of nitrogen (N) and phosphorus (P) after broadcast applications of poultry litter to tall fescue grown on a Captina silt loam. In a two-year study they found that plant uptake was the largest sink for N and accounted for about 60% of the total amount applied. Runoff accounted for about 1% of the applied N. Concentrations of NO3 -N in the soil solution at the 2-m depth in the treated plots increased with continual application of broiler litter and were twice as high as in the control plots at the end of the study. Although increasing over time, the aqueous solution concentrations were below 10-mg L-1 on NO3 -N.
Contamination of the ground water in a 100-sq mile area of the Ozark Highlands of northwest Arkansas was examined by MacDonald et al. (1976). This area is underlain by carbonate topography, which usually contains ground water in solution channels developed along fracture zones. They mapped the natural surface fracture patterns or linears in the study area by interpolation of arial photographs to locate surface expressions of major subsurface fracture zones. Springs and wells were then selected on the basis on being either on or off the mapped linears and analyzed for several water quality parameters. They found that 80% of the 76 wells, springs, and ponds analyzed were contaminated with bacteria and the groundwater was relatively free of inorganic chemical pollution. These authors developed a map of the pollution susceptibility of the study area that showed that approximately 90% of the area is susceptible to one or more of the pollutants. Sites located along the mapped airphoto linears had a greater tendency to be polluted but contamination of off linear wells was also high. The authors pointed out the important role of the soil in retaining and degrading the pollutants before the pollutant contaminates the groundwater. Any property of a soil that prevents the movement of water through it or allows water to pass through too rapidly for purification makes that soil unsuitable for contaminant remediation. They concluded that in the Ozark Highlands, susceptibility of the groundwater to pollution depends on geologic, soil pollution-susceptibility characteristics and fracture maps.
Literature Cited Guccione, M.J. 1993. Geologic history of Arkansas through time and space. The Arkansas Regional Studies Center, University of Arkansas, Fayetteville.
MacDonald, H.C., H.M. Jeffus, K.F. Steele, T.L. Coughlin, K.M. Kerr, and G.H. Wagner. 1976. Groundwater pollution in northwest Arkansas. Arkansas Agricultural Experiment Station Special Report 25.
Mott, D.N. 1997. Water Quality Report. 1990-1995. p 36. National Park Service, Buffalo National River.
Mott, D.N. and K.F. Steele. 1991. Effects of pasture runoff on water chemistry, Buffalo National River. pp. 229-238. In:N.E. Peters and D. E. Walling (eds.). Sediment and Stream Water Quality in a Changing Environment: Trends and Explanation. Proc. 20th General Assembly of the International Union of Geodesy and Geophysics. Vienna, Austria.
Paetzold, R.F. 1976. Transport of water and solutes in Captina silt loam. Ph.D. Dissertation. Department of Agronomy. University of Arkansas, Fayetteville.
Ransom, M.D., W.W. Phillips, and E.M. Rutledge. 1981. Suitability for septic tank filter fields and taxonomic composition of three soil mapping units in Arkansas. Soil Sci. Soc. Am. J. 45:357-361.
Romkens, M.J.M., H.M. Selim, H.D. Scott, R.E. Phillips, and F.D. Whisler. 1986. Physical characteristics of soils in the southern region. Captina, Gigger, Grenada, Loring, Olivier and Sharkey Series. Southern Cooperative Series Bulletin No. 264.
Sauer, T.J., P.A. Moore, Jr., K.P. Coffey, and E.M. Rutledge. 1998. Characterizing the surface properties of soils at varying landscape positions in the Ozark Highlands. Soil Sci. 163:907-915.
Scott, H.D., J.T. Gilmour, and A. Mauromoustakos. 1995. Fate of inorganic nitrogen and phosphorus in broiler litter applied to tall fescue. Arkansas Agricultural Experiment Station Bulletin 947.
Scott, H.D. and T.H. Udouj. 1999. Spatial and temporal characterization of land-use in the Buffalo National River Watershed. Environ. Conserv. 26(2):94-101.
Thiesse, B.R. 1984. Variability of the physical properties of Captina soils. M.S. Thesis. Department of Arkansas, Fayetteville.
USDA-SCS. 1981. Landuse regions and major land resource areas of the United States. Agriculture Handbook 296. Washington, D.C.
Wilson, G.V. 1986. Characterization and modeling of the dynamics of ground water mounds underneath septic tank filter fields. Ph.D. Dissertation. Department of Agronomy, University of Arkansas, Fayetteville.
Wood, L.S., H.D. Scott, D.B. Marx, and T.L. Lavy. 1987. Variability of sorption coefficients of metolachlor on a Captina silt loam. J. Environ. Qual. 16:251-256.
Return to Home Page Home Page SAAESD Electronic document prepared by: D.L. Nofziger, Oklahoma State University Email address: david.nofziger@okstate.edu