Effectiveness of ground cover depends on the potential for rill erosion relative to interrill erosion.
	Ground cover has a greater effect on rill erosion than on interrill erosion.
	The equation Eff = exp(-b %grdcov) used to compute effect of ground cover.
	The b value in this equations represents the relative effectiveness of ground cover—increased effectiveness means an increased b values.
	Values for b range from 0.025 where interriill erosion is the dominant erosion to over 0.05 where rill erosion is dominant.
	Example, b value is higher for steep slopes where rill erosion predominates than for flat slopes where interrill erosion predominates.
	Value b is greater where increasing ground cover significantly increases infiltration.
	Effectiveness of residue depends on contact between soil and ground cover.  RUSLE2 assumes less effectiveness for conditions where soil loss biomass is low.
	Effectiveness of residue on steep slopes is a function of type of residue.  Rocks get more credit because of their contact with the soil than long pieces of mulch like un-chopped wheat straw.