(6)
where X is Ln [crushing energy (J
kg-1)] with lower limit 0.1.
The abrasion coefficient of aggregates and vertical abrasion flux
simulated by SWEEP as a function of aggregate crushing energy for the
four soil types are shown in Figure 9a and b. Both relationships
appeared to be nearly logarithmic. However, a linear function provided a
good fit to the data. The abrasion coefficient of aggregates and
vertical abrasion flux decreased with increasing aggregate crushing
energy. This trend was consistent with previous studies for a range of
crushing energies (e.g., Hagen et al,1993; Zobeck, 1991b). Nonetheless,
different regression coefficients suggest that the rate of change in
abrasion coefficient and abrasion flux with an increase in crushing
energy varied among soil types. The rate of change in simulated abrasion
coefficients and abrasion fluxes with crushing energy was higher for the
two sandy loams than two silt loams. These effects were consistent with
measured soil loss.
The abrasion coefficient of aggregates and vertical abrasion flux
simulated by SWEEP as a function of clay amendment for the four soil
types are shown in Figure 10a and b. Both relationships appeared to be
statistically significant except the relationship between vertical
abrasion flux and clay amendment for Farrell sandy loam (Figure 10b).
The SWEEP simulated abrasion flux for the four soil types was reduced at
least 29% relative to a surface devoid of clay amendment.