Date of Graduation

5-2021

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Kristofor R. Brye

Committee Member

Larry T. West

Second Committee Member

Lisa S. Wood

Third Committee Member

David M. Miller

Keywords

Arkansas, Expansive, Hydrology, Ozark Highlands, Red-Soil Exception, Rural, Soil, Wastewater

Abstract

Distinguishing between red-clay soils that are non-expansive and can reduce and red-clay soils developing in problematic red parent material, which are expansive, but also non-reducing, is key for proper on-site wastewater system placement. The Arkansas Department of Health allows for the placement of on-site wastewater systems in certain red-clay soils that have the potential to reduce, but only in the Ozark Highlands [Major Land Resource Area (MLRA) 116A], which is referred to as the red-soil exception. There is currently little scientific data to support the geographic restriction of the red-soil exception. The objectives of this study were to: i) confirm the non-expansiveness and reducibility of select soils in the Ozark Highlands that meet the criteria for the red-soil exception for determining soil suitability for on-site wastewater system placement, and ii) compare the expansiveness and reducibility of the residual and colluvial, red-clay soils of the Ozark Highlands to those in other MLRA region groupings in Arkansas. Fresh soil samples were collected in conjunction with archived soil samples to create a 50-sample data set from the 38- to 50-cm soil depth interval for analyses. The alluvial soils of the Red and Arkansas Rivers region, which are known to be expansive and non-reducing, had a mean coefficient of linear extensibility (COLE) of 0.116 mm mm-1, whereas soils from the other four MLRA regions evaluated, including the Ozark Highlands, had significantly lower (P < 0.01) COLE values. Based on a 1-hr reduction test, soils from the Red and Arkansas Rivers region changed red color the least (∆A of -8.6 in the LAB color scheme; P < 0.01) compared to soil from all four other MLRA regions evaluated, including the Ozark Highlands. As an often-used indicator of expansiveness, the Mehlich-3-estimated cation exchange capacity (CEC-M), excluding any contribution from soil organic matter, was larger (24.5 cmolc kg-1; P < 0.01) for soils from the Red and Arkansas Rivers region than for soils from all four other regions evaluated. The CEC-M:clay ratio was also larger (0.46; P < 0.01) for soils from the Red and Arkansas Rivers region than for soils from all four other regions, which did not differ. Results of this study indicate the red-soil exception, used by the Arkansas Department of Health for determining on-site wastewater system suitability, could be expanded to include several additional MLRAs in Arkansas, excluding the alluvial, red-clay soils of the Arkansas and Red River valleys due to their expansive and reduction-resistant characteristics.

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