Hydraulic Conductivity of Three Southeastern Soils as Affected by Sodium, Electrolyte Concentration, and pH

Abstract

In the humid southeastern USA, little attention is given to the effect of electrolyte concentration or low levels of Na on clay dispersion, although dispersion‐related phenomenon such as surface crusting and erosion are common. Our objective was to determine the effect of electrolyte concentration, sodium absorption ratio (SAR), and soil pH on saturated hydraulic conductivity of three soils that differed in parent material. Cores packed with sieved soil at different pHs were leached with 10 pore volumes of solution at varying SAR and electrolyte concentrations. The relative decrease in conductivity during leaching was recorded as a measure of clay dispersion and subsequent clogging of pores. The Cecil soil (Typic Hapludult), which is derived from granitic parent material, was easily dispersed and hydraulic conductivity was sensitive to small changes in electrolyte concentration, SAR, or pH. The Davidson (Rhodic Paleudult) and Iredell (Typic Hapludalf) soils, derived from mafic parent material, were flocculated and insensitive to changes in electrolyte concentration and pH except at very high SAR. The implications are that southeastern soils may differ greatly in structural stability and this may be related to parent material. Dispersive soils need to be identified and managed in an appropriate manner.

Flocculation of Illite/Kaolinite and Illite/Montmorillonite Mixtures as Affected by Sodium Adsorption Ratio and pH

“…Suarez et al (1984) found that, at constant sodium adsorption ratio (SAR) and electrolyte concentration and at solution pHs of 6, 7, 8, and 9, hydraulic conductivity decreased and clay dispersion increased with increasing pH for two arid zone soils, one predominantly kaolinitic and one predominantly montmorillonitic. In a similar experiment on three soils from Georgia, Chiang et aL (1987) found the hydraulic conductivity of one soil to be sensitive and that of two others to be nonsensitive to pH changes from 4.5 to 8.5. They did not relate these differences to clay mineralogy.…”

“…hydraulic conductivity (Suarez et al, 1984;Chiang et al, 1987) and clay dispersion of soils (Suarez et aL, 1984;Gupta et al, 1984). Suarez et al (1984) found that, at constant sodium adsorption ratio (SAR) and electrolyte concentration and at solution pHs of 6, 7, 8, and 9, hydraulic conductivity decreased and clay dispersion increased with increasing pH for two arid zone soils, one predominantly kaolinitic and one predominantly montmorillonitic.…”

Salinity and Sodicity Interactions of Weathered Minesoils in the Four Corners Region

“…Elevated SAR values ( >13.0 mmol 1/2 L -1/2 ) do not cause physical degradation of soil if the system also contains high levels of soluble salts (Quirk and Schofield, 1955;McNeal et al, 1968;Frenkel et al, 1978;Shainberg et al, 1981;Abu-Sharar et al, 1987;Chiang et al, 1987;Lima et al, 1990;Malik et al, 1992;Curtin et al, 1994;Mace and Amrhein, 2001;Quirk, 2001). Conversely, physical degradation has been observed in soils with SAR levels below 13.0 mmol 1/2 L -1/2 when combined with low EC (Sumner, 1993).…”

Ion Transport and Permeability in an Allophanic Andisol at Low pH

“…However, few studies on the effects of solution pH on miscible displacement experiment for exchanging ions have been reported (Chan et al 1978(Chan et al , 1980aNielsen et al 1986;Ishiguro et al 1992). Studies on permeability change influenced by pH have also been few (Suarez et al 1984;Chiang et al 1987;Nakagawa and Ishiguro 1994;Ishiguro et al 2001). Allophanic Andisols, typical volcanic ash soils, have much amount of pH dependent charge (Okamura and Wada 1983;Iimura 1966).…”