In conclusion, the overall effect of these coal-derived humic acids on the treated soils
is enhanced resistance of the soils to erosion from simulated rainfall,
which from the results of this study was substantially achieved at relatively low rates (100 to 200 kg/ha).
The reduction in soil loss was due to slightly improved water retention capacity of the soils following HA treatment (which delayed the onset of runoff and favoured water entry through the stable interaggregate pore spaces within the soil beds) as well as to enhanced stability of the HA-treated aggregates which prevented them from collapsing easily upon contact with the impacting raindrops.
The practical significance of these
results is that amending erosion-susceptible soils with coal-derived humic substances
represents a potentially important soil conservation/management practice that we intend
to explore further using large-scale field studies.