Tuesday, November 14, 2006 - 10:15 AM

Predicting Runoff Sediment Losses from Selected Louisiana Soils Using a Suspension Turbidity Test.

Jim Wang1, Theophilus Udeigwe1, and Hailin Zhang2. (1) Louisiana State Univ, Dept of Agronomy and Environment Mgmnt, 313 Sturgis Hall, Baton Rouge, LA 70803, (2) Oklahoma State Univ, Dept of Plant and Soil Sciences, 368 Agriculture Hall, Stillwater, OK 74078

Runoff sediment loss from soils is one of main causes for water quality impairment. In addition, runoff of nutrients especially phosphorus is heavily associated with the runoff of sediments. Therefore understanding the relationship between sediments in runoff and soil properties is very important in order to minimize erosion with proper management. In this study, nine Louisiana soils of different textures were subjected to a runoff experiment under simulated rainfall events.  The runoff samples were collected and analyzed. Among runoff parameters, highly significant and positive linear correlations existed between total suspended solids (TSS) and turbidity (R2 = 0.98) as well as between TSS and particulate phosphorus (PP) and between turbidity and PP (R2 ≥ 0.95). Relating runoff parameters to soil properties, higher clay contents clearly resulted in higher sediment concentrations in runoff and their relationship could be best described by an exponential relationship (TSS = 0.10e0.14(Clay), R2=0.91) for these loam to silty clay soils. Soil EC inversely related to runoff TSS (R2 = 0.70). The SST test, a measure of soil suspendability in 1:200 soil to water suspension, best described runoff TSS (y = 0.06x - 4.38, R2 = 0.82), turbidity (y = 73.73x - 5442.53, R2 = 0.84), and PP (y = 0.04x + 2.68, R2 = 0.85).  The good linear relationships between soil SST and runoff TSS, turbidity or PP suggests that the SST test could be used to indirectly predict the potential loss of sediment and PP through surface runoff from cultivated soils.