2.3. Method applied to determine the erosion threshold
Knowledge of the influence of erodibility factors on soil erosion
(both environmental and related to agricultural management) can
be used to determine erosion thresholds, defined as the value (of
the erodibility factor) above which the reduction in erosion is
statistically significant. The erosion threshold approach is intended
to facilitate decision making with a view to improving the planning
of agricultural activity from the standpoint of soil conservation and
avoiding possible arbitrary decisions arising from the use of
empirical methods.
To establish the erosion threshold, we consider the hypothesis
that water erosion does not increase at a constant rate with respect
to erodibility factors. The conditions under which a research study
is conducted are of crucial importance in this respect; research
conditions in the field (agricultural plots) differ greatly from those
in the laboratory and can make it difficult to isolate the influence of
each erodibility factor on the overall erosion. For example, Roose
and Ndayizigiye (1997) showed that erosion did not increase
linearly with the slope gradient, due to the existence of a stonier
soil and less crusting on the steeper slopes, which reduced the
degree of erosion. That is, the erosion trend observed with respect
to a particular factor may be influenced by other factors, the
interference from which is difficult to isolate, given the working
conditions in the field plots. Nevertheless, these are the actual