Erodibility of a Sodic Soil Amended With Flue Gas Desulfurization Gypsum

Abstract

Sodic soils (Natraqualfs) represent a serious management problem in the lower Mississippi River Valley because of their dispersive nature. These soils are generally remediated with mined gypsum, but this is not economically feasible in the southeastern region. Instead, this study was conducted to determine if flue gas desulfurization (FGD) gypsum would effectively reduce the erodibility of these sodic soils. A-horizon samples (<2 mm) from a representative soil were characterized for basic physical and chemical properties. Additional subsamples (<8 mm) were amended with FGD gypsum at rates equivalent to 0, 3.36, 6.72, and 13.44 Mg ha−1, packed to a depth of 7.6 cm in plexiglass cylinders, and subjected to simulated rainfall at an intensity of 64 mm h−1 for 1 h. The erodibility data indicated that all amendment rates produced significant (P < 0.05) increases in percentage aggregation, aggregation index, and percentage transmission. These improvements in erodibility parameters led to a 71% increase in total infiltration, a 36% decrease in total runoff (RO), and a 77% decrease in soil loss at the 13.44-Mg ha−1 rate relative to the 0 treatment. Sediment size distributions between 53 μm and 500 μm increased an average of 38%, and the less-than-5-μm fraction decreased 21%. The results indicate that FGD gypsum will effectively increase infiltration and reduce RO and soil loss from sodic soils. The formation of larger sediment sizes also indicates that the quality of surface waters will be improved as the proportion of finer sediment in the RO is diminished.