Compressibility and Hydraulic Conductivity of Reconstituted Soil-Compost Mixtures for Urban Horticulture

Abstract : The aim of our study was to evaluate the efficiency of compost application to reduce the soil susceptibility to compaction and to improve the circulation of water. To this purpose, we studied several soil/compost mixtures differing by compost type, compost particle size, and amount of compost introduced, after an accelerated ageing. Density, porosity and saturated hydraulic conductivity were measured before and after a compaction of 100 kPa which is equivalent to the weight of a car. The main factor inducing difference between the mixtures was the introduced amount of compost: the mixtures with 40% v/v of compost were less dense compared with 20% v/v and the control soil, before and after compression. Ageing did not affect the compression results. The study suggests that the most promising results occurred in the treatment with the largest proportion of compost (40% v/v). The benefits of compost on the soil properties were relatively small with the 20% v/v mixture. The particle size of the compost had a relatively small effect on properties and was apparent only for the 40% v/v mixtures. These results suggest compost addition to soil at 40% may improve physical properties in urban soils. The use of stable compost is likely to provide long term positive effect on the soil agronomic properties and benefit plant growth.