Respiration (CO2 flux) from urban and peri-urban soils amended with green waste compost

Abstract

Application of municipal green waste composts to urban land is encouraged by evidence of potential gains in soil carbon (c) storage but there is sparse reporting of C fluxes from urban soils. The CO2 efflux from an inner city soil was measured in response to experimental manipulation of temperature and moisture losses following the incorporation of green waste compost, in various volumes, in a controlled laboratory experiment. The results were compared to five peri-urban field sites having also received an amendment of green waste compost as part of their management for soil improvement.The mean and range of soil respiration rates were significantly increased by compost incorporation both in the field and in the laboratory (≤1.5 and ≤3.5μmol CO2m2s−1 respectively), due to increased substrate availability via compost; higher volumes of compost application increased respiration rates furthest. However the sensitivity of CO2 flux to temperature changes was both reduced and stabilised after compost additions (Q10~1.1), compared to the control without compost (Q10~2). Soil moisture correlated with respiration rates, confirming its regulatory effect.The present results demonstrate that compost addition to these urban soils, despite enhancing net CO2 emissions, may reduce the sensitivity of soils to CO2 losses due to urban warming. In this respect urban soil management using green waste compost could reduce the susceptibility of soils to C losses over longer terms whilst providing other soil quality benefits in the short to medium terms.