Soil surface structure stabilization by municipal waste compost application

Loess-derived soils of the northern Paris basin are prone to surface structure degradation leading to erosion, flooding, and pollution. Concomitantly, recycling of municipal solid waste (MSW) has been recognized as an important environmental issue. The aim of this study was to test the impact of compost application on soil surface structure degradation and on the resulting runoff and erosion processes. Aggregates (0-30 mm) from a silty loam Typic Hapludalf were mixed with a MSW compost at a rate of 15 g kg(-1) (dry matter). Repacked seedbeds were exposed to a 19 mm h(-1) simulated rainfall for 60 min. Morphological evolution of the soil surface was monitored using sequential photographs. Crust and seedbed microstructures were studied after 4, 15, and 60 min of rainfall. using thin sections from resin-impregnated replicates. Runoff was measured every five minutes, and aliquots were sampled for sediment concentration. In control seedbeds, surface crusts quickly developed and the whole seedbed slumped because of aggregate coalescence through deformation in a viscous state. Compost application delayed crust formation and prevented seedbed slumping. This, in turn, delayed runoff from 2.5 to 9.2 mm of cumulative rainfall. Sediment concentration in the incipient runoff was decreased from 36.4 to 11 g L-1.This could be ascribed to the stabilization of the aggregate framework. which allowed the particles detached from the top of surface aggregates to illuviate a few millimeters deeper. In a highly unstable soil, MSW compost application was efficient in combating soil surface structure degradation and its consequences on runoff and erosion.