X. Sort et Jm. Alcaniz, CONTRIBUTION OF SEWAGE-SLUDGE TO EROSION CONTROL IN THE REHABILITATION OF LIMESTONE QUARRIES, LAND DEGRADATION & DEVELOPMENT, 7(1), 1996, pp. 69-76
The aim of this study was to evaluate the effects of high doses of mun
icipal sludge on soil aggregation and to assess its value for soil ero
sion reduction, both under natural and in simulated rainfall condition
s. Doses of 200 and 400 Mg ha(-1) sewage sludge (dry weight) were appl
ied to the soil of experimental plots situated on a 28 degree slope. T
wo sludge application procedures were tested: pre-mixing into the soil
before disposal on the slope, and direct application on the soil surf
ace. Sheet erosion was measured by collecting the sediment carried dow
n to a Gerlach trough situated at the base of the plots. Simulated rai
nfall, with an intensity of 64 mm h(-1), was applied to evaluate soil
erodibility. When the soil had no vegetation, the erosion measured on
plots treated with sludge represented less than 10 per cent of the ero
sion from the control plot. Even when the vegetation was well develope
d, the erosion was also lower in the plots where sludge had been appli
ed. In simulated rainfall, the soil loss was inversely proportional to
the sludge dose, and when sludge was applied directly on the soil sur
face the erosion rates and particle mobilization caused by raindrop im
pact were minimal. Sludge amendments increase infiltration rates and i
mprove soil structure, increasing the mean weight diameter of aggregat
es and their water resistance.