Effects of Straw Mulching, Compost Percentage, and Slope Ratio on Green Vegetation Establishment and Runoff Quality Control

Soil erosion prevention and management represents a major environmental challenge faced by many highway construction projects. This study analyzed sustainable improvements to current standard procedures for final grade turfgrass establishment on disturbed soils. Using a series of greenhouse studies, compost and compost–topsoil blends with and without straw mulching were compared with a standard topsoil–straw–fertilizer practice in terms of their ability to reduce soil and nutrient loss and improve the rate of green vegetation (GV) establishment at a variety of slope ratios. Straw mulching significantly improved GV establishment ($64\%–93\%$), reduced runoff volume ($22\%–99\%$), and reduced sediment and nutrient mass export ($71\%–99\%$ for sediment, $71\%–92\%$ for nitrogen, and $66\%–99\%$ for phosphorus). These reductions and improvements were attributed largely to the physical barrier offered by the straw mulch layer. This layer improved soil water storage through reduced evaporation, reduced rainfall impact, and increased media surface roughness, which resulted in reduced runoff velocity, soil splash, and compaction, and increased available water for plant uptake. Compost amendment to the topsoil standard material with straw mulching in general increased hydraulic conductivity and improved soil aggregation and stability, which reduced the total runoff volume ($13\%–59\%$), sediment mass ($64\%–98\%$), and nutrient mass export ($6\%–82\%$ nitrogen and $4\%–76\%$ phosphorus). As slope ratio increased, export of runoff volume, sediment, and nutrients statistically increased, whereas GV decreased.