Corn production on an eroded soil: effects of total rainfall and soil water storage

Soil erosion generally causes reduced crop productivity because of degraded soil physical and chemical properties. A long-term study was established in southwest Wisconsin, USA, in 1985 to investigate the effects of past soil erosion on corn (Zea mays L.) production. Three levels of erosion (slight, moderate, and severe) of a Dubuque silt loam (fine-silty, mixed, mesic, Typic Hapludalfs) were investigated, as defined by the percent of surface soil remaining. Corn was grown from 1985 to 1999 with small differences in grain yield among erosion levels, but with a long-term trend of decreasing yield with erosion. Average yields were 10.7, 10.3 and 10.3 Mg ha(-1) for slight, moderate and severe erosion levels, respectively. Based on the 15 years of research it appears differences in grain yields among erosion levels can be attributed mainly to soil water availability. When rainfall was below the 15-year average, grain yield was 12.8, 12.9 and 15.2% less than that of the 15-year average for slight, moderate and severe erosion levels, respectively. Soil water storage increased as erosion severity increased, however more stored water was needed to produce comparable yields with increasing erosion level. Thus, grain production differences among erosion levels from year-to-year can be attributed to weather differences, particularly rainfall.