Cultivated Williams loam (Typic Argiboroll, fine-loamy, mixed) soils in north-central South Dakota were sampled after pastures were established and 8 years later so that the effect of the pastures on soils could be studied from analysis in the laboratory. Pastures were seeded to Russian wildrye (Elymus junceus Fisch.), crested wheatgrass (Agropyron desertorum (Fisch.) Schult.), or a mixture smooth bromegrass (Bromus inermis Leyss.), intermediate wheatgrass (Agropyron intermedium (Host) Beauv.), a pasture alfalfa (Medicago sativa L.). Soil N and bulk densities increased as available P decreased in the 8 years. The soil organic matter increased under all pastures, but it was small. The increases in organic matter, decreases in available P, and increases in saturated-clod bulk densities were different in the various pastures. Total N and organic matter increased about 0.001 and 0.02% per year, respectively, which is slower than the rate of decrease caused by cultivating the original grassland soils.
