Use of humic substances as soil conditioners to increase aggregate stability.

In many agricultural soils in the semi-arid and arid mediterranean climates: exposure to cyclic wetting and drying (WD) can reduce aggregate stability. The extent to which soil pretreatment with coal-derived humic substances (HS) can increase aggregate stability in soils exposed to cyclic wetting and drying (WD) was evaluated in this study. The soils studied are an Acireale silty clay loam from Sicily, a Principina silt loam from Tuscany and a Bovolone loam from Venetia in Italy. On each soil right rates of the HS (0, 0.001, 0.01, 0.05, 0.10, 0.50, 1.00 and 10.00 g/kg of soil) and four WD cycles (0, 3, 6 and 9) were used to assess any changes in Stability.