Relation of T Values to Rill and Gully Erosion
If nothing else, rills and gullies are major nuisances. Whereas rills routinely can be obliterated by tillage on cropland, deep, incised gullies cannot be filled easily (Chapter 3). Although gullies can develop independent of rills, land management that controls rill erosion also reduces the likelihood of gully formation. The rule of thumb is that soil-loss tolerance values are set below about 7 tons/acre (15 metric tons/ha) per year, the interrill and rill erosion rate at which rills begin to form.