A potential stormwater management intervention: Compost incorporation improves infiltration rate and associated soil hydro-physical properties

Urbanization associated construction operations, while necessary for infrastructure development, can result in highly disturbed and intentionally, or inadvertently, compacted soils. Compost incorporation into these disturbed soils is a relatively simple intervention that may alleviate compaction and increase important post-construction soil physical properties such as water infiltration capacity. Results in the literature about compost amendment effects on soil hydraulic properties are mixed, and compost experiments rarely test more than a single amendment rate or type concurrently, often without incorporation. To address this research gap, we conducted a laboratory study using soil columns filled with either woodchips-food waste (Compost 1) or poultry manure-food waste (Compost 2) compost mixed with silt loam or clay loam soils at 0, 15, 30, and 50% rates (by volume). Water (10 cm depth) was infiltrated into the columns at 15-day intervals over six months to assess the effects of compost incorporation on soil hydraulic properties. After six months, bulk and particle densities decreased, while porosity, field capacity, and plant available water increased at 30 and 50% compost rates. Magnitudes of effects differed by soil type, but compost type had no effect. Infiltration rates gradually stabilized after two months, possibly due to reduced compost decomposition and consolidation over time. Infiltration rates were highest for 50% compost, followed by 30% and 15%, and lowest for the 0% treatments. Infiltration rates were about 10, 5, and 1.5X that of the 0% compost (control) treatment, respectively. Results suggested that a minimum of 30% compost incorporation may be required for improving stormwater infiltration-related soil properties, and that peak infiltration rates observed after initial compost addition may decline, but compost amendment leads to sustained improvement in infiltration rates for at least several months after incorporation.