Evaluation of seven mulch treatments for erosion control and vegetation establishment on steep slopes

Abstract

Soil erosion and sediment pollution in and around construction sites can result from land disturbing activities that leave areas of unprotected soil during construction. This study evaluated different types of hydromulch for erosion control and grass establishment in comparison to straw alone or straw plus an application of polyacrylamide (PAM) on steep slopes at five construction sites in North Carolina. One site was located in the Coastal Plain (CP) region, and another in the Mountain (M) region, with the remaining three in the Piedmont (P1 through P3). At each site, 20 plots (3 m [10 ft] wide by 6 to 9 m [20 to 30 ft] long) were established on a contiguous area. After applying grass seed, the erosion control treatments were as follows: wheat straw (Triticum aestivum) and wheat straw + 22.4 kg ha⁻¹ (20 lb ac⁻¹) of granular, linear, anionic PAM on all five sites; and hydromulches including flexible growth medium (FGM), stabilized mulch matrix (SMM), bonded fiber matrix (BFM), wood fiber/cellulosic blend (WCB), and wood fiber mulch (WFM) applied at three sites each. Runoff volumes, turbidity, eroded sediment, and nutrient concentration data were collected after natural rain events; grass growth and cover were also evaluated. At both the CP and M sites, there were no differences between treatments, most likely due to the sandy soil texture at CP and a combination of sandy soil texture and relatively light rainfall events at M. At P1, there was a trend of straw cover producing higher runoff volume, turbidity, total suspended solids (TSS), and in general higher concentrations and amount of nutrient loss compared to all hydromulch treatments. In contrast, at P2 and P3, hydromulches tended to have greater runoff volumes, turbidity, and TSS compared to straw. Also, on these sites, straw + PAM treatment had lower concentrations of total phosphorus (P) in runoff compared to WCB. The addition of PAM did not have an effect on runoff volumes at any site, but it reduced average turbidity on P2. Overall, there was no clear pattern of hydromulch advantages over straw as a mulch for reducing erosion or establishing grass on steep slopes.