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 (Δ) or noncompacted (Γ) 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 × 10 −5 m.s −1 in the MSW plot and 4.1 × 10 −5 m.s −1 in the SGW plot, against 2.2 × 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 × 10 −5 m.s −1 while that in the compost‐amended plots remained stable.