Rainfall Simulation On Erosion Abatement Measures for Louisiana Roadsides.

In this study we evaluated the impact of compost/mulch thickness (no or 0 as control, 5 cm, and 10 cm) and tillage practices on runoff flow rate, total suspended sediment (TSS) losses and phosphorous (P) using in-situ rainfall simulation. Four sites with eight plots (side-by-side) were studied in two locations in West Feliciana and Rapides Parishes, LA. The former location was in an active highway construction area while the latter location was in an established area plagued by continual rill and sheet erosion. A Tlaloc 3000 rainfall simulator at an intensity of 70-80 mm/h was used. Two pulses of 30 min durations were applied to each plot. The second pulse was applied as soon as runoff from the first pulse ceased. Runoff was observed after 5 and 10 min for the 5cm and 10cm compost/mulch plots, respectively and after 2 min for the control plots. Furthermore, the compost/mulch resulted in reduction of the flow rate from 1.3 mm/min to 0.4 – 1.0 mm/min. Tillage incorporation of the compost/mulch reduced its effectiveness and increased the flow rate for the 5 and 10 cm compost/mulch plots. One way analysis of variance (ANOVA) indicated significant differences between the first and second pulses. The cumulative flow as a percentage of that applied using the rainfall simulator was high for the control plots (90%) and was reduced to 28% for the 10 cm compost/mulch plots. The TSS results revealed that compost/mulch significantly decreased sediment concentration in the runoff. Total P in the runoff was <1 ppm for all treatments. The presence of compost/mulch on the soil surface decreased runoff, flow rate, and TSS and is recommended for erosion control in Louisiana’s roadsides.