Foremost, is the large decrease in organic matter content, which probably explains the large increase in bulk density and modulus of rupture (crusting strength) between the uneroded and slightly eroded soils.
Progressive erosion created changes in the clay mineralogy of A horizons between the uneroded and severely eroded soils [ILLUSTRATION FOR FIGURE 3 OMITTED].
The productivity of the eroded phases, as a function of incremental soil depth [ILLUSTRATION FOR FIGURE 4 OMITTED], indicated that the greatest soybean yield restrictions occurred as ESD decreased from 60 to 40 cm (Rhoton, 1990).
Given the relatively small range in 1984 organic matter contents and the lowest yields occurring at the moderately eroded site, organic matter content does not explain yield differences, although a slight relationship occurs within site.
Minimum levels of runoff and soil loss occurred on the uneroded soil, but both increased substantially on the slightly eroded soil.
The failure of eroded soils to meet criteria for the taxonomic placement of the associated slightly eroded or uneroded Mollisols has also been reported by Lewis and Witte (1980), Jones et al.
To achieve this goal, some small areas, too small to map, of the eroded phases were included in this study.
Relative yield reduction for severely eroded Alfisols that were classified differently was 20% with a standard error of 4, whereas that for Alfisols that were not classified differently was 10 percent with a standard error of 2.
Increasing amounts of soil material had been eroded as erosion phase went from slight to moderate to severe erosion.