Impacts of compost blankets on erosion control, revegetation, and water quality at highway construction sites in Iowa

Compost blanket applications from three sources in Iowa were compared to two conventional soil treatments on a highway embankment. Composts were applied as blankets over the existing subsoil at 5- and 10-cm depths. A topsoil treatment, a conventional Iowa Department of Transportation method, was applied at a depth of 15-cm. Rainfall was applied using a rainfall simulator at a target intensity of 100 mm/hr. Plots were measured for performance based on runoff, interrill and rill erosion, cover crop production, and water quality for two different conditions. Plots were sampled shortly after construction to simulate construction activities at startup, and six weeks after cover crop establishment.; Compost applied as a surface layer or mulch has been compared with topsoil and subsoil as a media for crop growth and weed suppression during revegetation of a highway right-of-way. In this study compost was shown to be as effective as topsoil and subsoil controls for crop growth, while significantly reducing growth of weed species. There were no significant differences between 5- and 10-cm depths of composts, indicating that the shallower depth would be an adequate depth for establishing a cover crop and achieving weed suppression. Compost mulches offer promising opportunities for crop and weed management during revegetation of roadsides and other disturbed landscapes.; Interrill runoff samples were collected on all treatments for the 1 st hour after runoff began. Compost application depth was not an important factor in measured interrill erosion rates. Compost treatments had significantly lower interrill erosion rates compared to topsoil and control treatments on un-vegetated plots.; Rill erosion was measured on treatments using rainfall simulation at a target rate of 100 mm/hr and adding 5 inflows at the top of the rill on both vegetated and un-vegetated plots. Rill erodibility and critical shear values were calculated for all treatments using the shear stress model, but R-squared values were lower on composts compared to the two soils.; Runoff from compost and soil treatments resulted in one or more of the composts containing significantly higher concentrations of N, P, K, and nine heavy metals than the control soil or the topsoil. Similarly, soluble and adsorbed concentrations of nutrients and metals contained in runoff and erosion products exported from the compost-treated test plots were generally much higher than those from the topsoil and control plots.; The Water Erosion Prediction Project (WEPP) model was used to evaluate solids loss and runoff from the application of composts and two conventional soil treatments on a backslope and foreslope application at four different slopes (5%, 10%, 20%, and 30%). The results of calculated solids loss and runoff were coupled with water quality data to determine the environmental impacts of applying composts. (Abstract shortened by UMI.)...