Compost for Permanent Vegetation Establishment and Erosion Control along Highway Embankments

Abstract

Erosion management is a major environmental challenge facing highway construction. A research study was undertaken to analyze possible sustainable improvements to current standard procedures for final grade turfgrass establishment on disturbed lands at both field and greenhouse scale. Pure compost, biosolids and greenwaste, and two topsoil/compost blends were compared with a topsoil standard (with additional straw and fertilizer application) in their ability to reduce sediment and nutrient runoff and improve green vegetation (GV) establishment. Differences in field GV rates were only observed during initial establishment (biosolids and topsoil had 11%–35% greater GV). This period coincided with an initial flush of nutrients and sediment that was 3- to 17-fold greater than later phase runoff. After this initial runoff phase, tested materials exported largely comparable nutrient and sediment runoff. In the controlled greenhouse studies, only the biosolids treatment reduced runoff volume, by 40%–98%, compared to the standard practice. Evidence of soil sealing from rainfall impact was seen for topsoil/compost mixtures, resulting in 20- to 28-fold greater total runoff volume and 28- to 224-fold greater sediment export than topsoil. Compost addition increased nutrient export 1.5- to 51-fold and 2.2- to 3.3-fold for phosphorus and nitrogen, respectively, due to increased runoff concentrations (pure compost) or volume (topsoil/compost mixtures). It was hypothesized that the additional straw mulch layer for the standard topsoil offered increased surface resistance and physical protection from rainfall impact and surface flow compared to the nonmulched compost treatments. Inclusion of a straw mulch layer with compost may provide similar, or better, slope stability performance.