Estimating the Water‐Dispersible Clay Content of Soils

Abstract

Soil erodibility is influenced by several soil properties including the extent to which the clay fraction will disperse in water. Because early methods for estimating soil erosion were empirical methods and did not utilize water‐dispersible clay as a parameter, few data have been collected. The recent development of the Water Erosion Prediction Project (WEPP) model, a process‐based model for predicting water erosion that uses water‐dispersible clay in the algorithm for computing interrill erodibility, resulted in an increased demand for these data. In order to accommodate this and similar models, a method for estimating the water‐dispersible clay content of soils based on existing information is needed. Data collected by the National Soil Survey Laboratory in support of the WEPP were used to identify soil properties that were significantly correlated with water‐dispersible clay and to develop equations to estimate the water‐dispersible clay content of soils based on those properties. The property most strongly correlated with water‐dispersible clay is total clay. Other properties significantly correlated with water‐dispersible clay are the water content at 1.5 MPa, dithionite‐citrate‐extractable Fe and Al, the coefficient of linear extensibility, Wischmeier's M, the very‐fine‐sand content, the ratio of cation‐exchange capacity (CEC) to total clay, Bouyoucos' clay ratio, and the CEC. A simple linear regression of water‐dispersible clay vs. total clay revealed that, for the soils included in this study, approximately one‐third of the total clay was water dispersible. However, the model only had an R2 of 0.604. When the ratio of the CEC corrected for organic carbon (CCEC) to total clay was included in the model, the R2 improved to 0.723. However, sorting the data by the ratio of CCEC to total clay instead of including it in the model improved the overall fit of the model and increased the R2 to 0.879.

Efeitos de sistemas de cultivo na densidade e macroporosidade do solo e no desenvolvimento radicular do milho em latossolo roxo

“…Nos dois primeiros casos, evita-se a ação da água da chuva sobre o solo exposto, principalmente sobre os agregados menores, menos estáveis. O aumento no teor de matéria orgânica aumenta a atividade bioló-gica (Ehlers, 1975;Roth et al, 1986;Winter et al, 1990), possibilitando a formação de ácidos húmicos e de complexos argilo-orgânicos (Castro Filho, 1988), que diminuem a dispersibilidade da argila (Fuller et al, 1986;Brubaker et al, 1992;Fuller & Goh, 1995) e possibilitam a formação de microagregados de maior estabilidade. Esse aumento foi mais efetivo na linha da cultura, em virtude das operações de plantio, pressões exercidas pelo sistema radicular e presença maior de raízes.…”

Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media

“…Besides the well-documented effects of clay mineralogy (e.g. Seta and Karathanasi [34]) and solution ionic strength and pH [27,41] on colloid dispersion, total clay content [94], soil moisture conditions [95], soil management [96] and interactions among these properties have also been shown to affect colloid dispersibility. Actually, interparticle forces such as vander Waals attraction and electrolytic repulsion determine colloidal fines stability.…”

Mechanical dispersion of clay from soil into water: readily-dispersed and spontaneously-dispersed clay

“…When wet, soil in which much of the clay is RDC may collapse with the loss of larger pores and homogenization of the soil structure. This can result in a range of agricultural and environmental problems which include anaerobic soil which is not suitable for plant growth and reduced water infiltration rates which can result in increased water runoff, erosion and flooding (Brubaker et al, 1992). When dry, soils containing dispersible clay can form surface crusts or can 'hard-set' which can prevent crop emergence and which can increase the energy requirement for tillage.…”