Using Compost in Post Construction Soils: Compost Source and Rate Alter Soil Improvements

Urban development can degrade the natural function of soil through stripping of topsoil and compaction by heavy equipment. This creates a soil environment that is highly compacted with reduced infiltration and is unfavorable for vegetation establishment. Poor performance of vegetation in these areas generally leads to long-term aesthetics and erosion problems. Research has demonstrated that compost incorporation, tilling compost into the soil, can be used to improve soil conditions. A greenhouse and a field study were used in conjunction to examine compost incorporation as a method for soil improvement. The greenhouse study investigated the effects of a sandy loam soil on two sources of compost at 0%, 10%, 30%, 50%, and 100% compost by volume on vegetation germination, quantity, and quality. The two sources of compost preformed similarly and had no differences in germination and vegetation quantity or quality. Higher rates of compost lead to better germination and increased vegetation quantity. For the field study, the effects of compost incorporation on runoff volume, runoff quality, and vegetation production were evaluated for one year in Raleigh, NC. Two sources of compost were used (1) McGill SportsTurf® at 10%, 30% and 50%, and (2) Campus compost at 30% by volume compared to a tilled control with no compost. Tilling the soil alone was enough to increase the infiltration and reduce runoff volumes. Compost additionally did not alter the runoff quality for all treatments. However, increased vegetation mass was measured for treatments with McGill Compost likely due to its ideal nutrient profile. Together, these studies demonstrate that higher rates of compost may not inhibit germination, but the compost nutrient profile may play an important role for longer-term vegetation establishment. Additionally, tilling the soil may be a viable way to improve infiltration in post construction soils.