Soluble Salt Concentrations in Runoff Waters from Soils Previously Cropped to Rice

Abstract

AbstractSoluble salt damage to rice in Arkansas has been evident in recent years. In order to adequately model salt balances for Crowley silt loam soil (Typic Aibaqualfs) cropped to rice (Oryza sativa L.) and soybean (Glycine max L. Merr.) in the Grand Prairie region of Arkansas, a description of soluble constituents in runoff water was needed. Three fields were monitored for soluble salts in runoff and irrigation water as well as runoff volume. As cumulative runoff increased, a logarithmic decline in the concentration ratio of runoff water salt concentration to irrigation water salt concentration was found for electrical conductivity (EC), Ca, Mg, Na, SO4, and Cl for the first 10 cm of runoff after removal of the rice floodwater. The equation in which the logarithm of the concentration ratio was the dependent variable and cumulative runoff was the independent variable had a common slope among fields for the solution variables studied. A common intercept was found for Ca and Na but not for EC, Mg, SO4, and Cl. A second linear relationship was developed where the intercept in the above for SO4 and Cl was found to be a function of irrigation water concentration. At one field where sufficient data were available the concentration ratio stabilized after 10 cm of runoff and could be predicted using the concentration ratio equation where cumulative runoff was set at 10 cm.