Effect of Urban Waste Compost Application on Soil Near-Saturated Hydraulic Conductivity

Compost application tends to increase soil fertility and is likely to modify soil hydrodynamic properties by acting on soil structural porosity. Two composts, a municipal solid waste compost (MSW) and a co-compost of green wastes and sewage sludge (SGW), have been applied every other year for 6 yr to cultivated plots located on a silt loam soil in the Parisian Basin, France. Four soil zones were defined in the topsoil after plowing: the plowpan located at the base of the plowed layer, compacted (delta) or noncompacted (gamma) zones located within the plowed layer, and interfurrows created by plowing and containing a large quantity of crop residues together with the recently-applied compost. To assess the effect of compost application on the near-saturated soil hydraulic conductivity, infiltration rates were measured using a tension disc infiltrometer at three water pressure potentials -0.6, -0.2, and -0.05 kPa in the various zones of the soil profile. Compost addition decreased K(sat) in the interfurrows after plowing by almost one order of magnitude with average values of 5.6 x 10-5 m.s-1 in the MSW plot and 4.1 x 10-5 m.s-1 in the SGW plot, against 2.2 x 10-4 m.s-1 in the control plot. This effect had disappeared 6 mo after plowing when the average K(sat) in the control plot had decreased to 1.9 x 10-5 m.s-1 while that in the compost-amended plots remained stable.