Construction of roads exposes and compacts the subsoil, resulting in reduced stormwater infiltration, increased erosion, and problems with vegetation establishment. High infiltration rates are needed to manage runoff from adjacent roads, and good vegetation is needed for longterm erosion control and aesthetics. Research has demonstrated that tilling and compost can be used to improve soil function of disturbed soils. However, there has been minimal testing of different compost application methods and evaluation of compost screen size to optimize soil improvement. This project will determine the optimal compost application method (surface application verses incorporation into soil) and compost screen size to inform NCDOT BMP on compost application for vegetation establishment and stormwater management. A laboratoryscale experiment and hydrologic modeling will be used to test different compost sources, screen sizes, and compost rates on soil infiltration rate and water retention. A field-scale experiment will investigate different compost application methods on vegetation establishment, runoff quantity and quality, and soil infiltration rate. The results should provide improved guidance on the best compost application method and screen size to optimize compost application for vegetation establishment and stormwater management in post-construction and degraded soils.
In addition to compost, there are many other biological soil amendments such as biochar, biostimulants, and microbial inoculants. Much of the research on these amendments has been conducted in agricultural settings. Studies have found that bio-stimulants and microbial inoculants can speed up plant growth and increase drought tolerance, while soil improvements of biochar mimic that of compost (increased infiltration, water retention and plant growth). There has been a growing interest in using these amendments in degraded soil to improve soil physical and hydrological properties and vegetation establishment. This project will survey available biological amendments for availability and cost, and test the most promising of these amendments in comparison to compost for vegetation establishment and drought tolerance performance.
A greenhouse study will be used to test several biological soil amendments
(compost, biochar, bio-stimulants, and microbial inoculants) for grass germination, growth, and drought tolerance. The results should provide information on biological soil amendments that can enhance vegetation establishment and drought tolerance.
Together, these experiments on compost and other biological soil amendments will help to provide information to ensure that soil improvement BMPs are optimized for the lowest-cost, effective solution.
