Compost Incorporation: A Solution to Soil Erosion and Stormwater Management in Urban Soils?

The construction of roads, buildings, and other structures can result in highly compacted soils causing greater surface runoff and soil erosion. Compost tilled into these soils may alleviate compaction and facilitate stormwater movement and storage. To test this, soil columns (15×7.5 cm2) were prepared by mixing coarser and finer composts with sandy loam and clay loam soils at 0, 15, 30 and 50 % rates on a v/v basis. About 500 ml of ponded deionized water was passed through the columns every 15 days for 6 months. Infiltration rates increased from initial days to 60 days, then gradually decreased and became almost stable after 90 days in sandy loam (~ 90 cm/h) and after 75 days in clay loam soil (~36 cm/h) possibly due to compost decomposition and stabilization in soils. No significant variation was observed between compost types. To assess the effects of compost on vegetation cover establishment at field level, we tilled soil with/without 30% compost in the upper 15 cm soil and planted plots to grass, wildflower and grass-wildflower mixture. A significantly higher average vegetation cover (55%) was observed in compost plots than non-compost plots (37 %) after 45 days of plot establishment. The highest vegetation cover in Compost-Grass-Wildflowers plots indicating grass-wildflower mixtures can be an alternative to grass cover in roadside soil erosion control. Our study also suggested that compost application eliminates the necessity of chemical fertilizers application for vegetation cover establishment in urban soils. In addition, hydro-mulch and excelsior increased the moisture content in upper 5 cm and 12 cm soil and reduced temperature in 5 cm depth compared to bare plots. However, no significant differences between hydro-mulch and excelsior were found. This experiment will continue for two years to assess the long-term effects of compost incorporation on stormwater infiltration, erosion control and vegetation establishment.