Utilization of MSW compost for organic matter conservation in agricultural soils of NW Spain

The recycling of the organic matter contained in municipal solid waste (MSW) as an amendment for agricultural soils after composting can be an option for conserving the organic matter levels in soil. In order to ascertain the amounts of compost needed for the conservation of soil organic matter, the mineralization rates of two MSW composts (obtained in the two main industrial composting facilities in Galicia, NW Spain), and three agricultural soils from different parent material (granite, schist, and gabbro) were determined in a laboratory study. A simple first-order kinetic model adequately described the mineralization of compost, whereas the mineralization of soil was best described by a two-compartment first-order model. The addition rate for each of the composts for maintaining the soil organic carbon (SOC) in the soils in targeted levels after 25 years was calculated from the mineralization data for two soil temperature scenarios. At the current mean soil temperature the compost doses would range from 4.0 to 7.2tha−1 (dry weight) to maintain the present SOC concentrations and from 8.5 to 15.6 to reach 3.5% SOC. An increment of 2°C in the mean soil temperature as a consequence of climate change would increase in a 10% the requirements of compost to maintain the targeted levels of SOC.