Agriculture and Environment: Corn (Maize)
Environmental Impacts of Production: Soil Erosion and Degradation
Studies in the United States have shown that environmental susceptibility to erosion may or may not be related to overall productivity (Larson et al. 1988).
In corn producing areas of Minnesota, soils vulnerable to erosion and those low in productivity were often not the same lands. In fact, these two types of land were not correlated. However, land that is vulnerable to erosion eventually losses productivity.A study of soil erosion in the corn belt areas of lowa, Minnesota, Wisconsin, and Illinois indicates that erosion rates have declined. In 1932 erosion rates were more than 37 metric tons per hectare per year when corn production amounted to only 2.75 metric tons per hectare per year.
By 1982 average erosion rates were down to 19.5 metric tons per hectare per year. By 1992, after 18% of all arable cropland had been taken out of production (including the most highly erodible areas) through the Conservation Reserve Program (CRP), erosion in the United States was estimated at 14 metric tons per hectare per year while corn production was about 8.6 metric tons per hectare per year (Runge and Stuart 1998).
Just as there is no correlation between a soil's susceptibility to erosion and its fertility, there is no correlation between row crop cultivation and erosion. Row crops have increased considerably in the United States, for example, from 1930 to the present, precisely when erosion declined. The correlation is between mechanical row crop cultivation and erosion. No-till and conservation tillage row crops have reduced erosion dramatically. Erosion rates, however, still appear to be beyond replacement values and consequently are unacceptably high.
Declines in soil erosion result primarily from investments in conservation measures that include terraces, strip cropping, crop rotations, windbreaks, and switching to conservation tillage (reduced tillage and no-till cultivation). By 1994 no-till farming techniques were practiced on about 12% of row crop production.
Mulch tillage (in which crop residue is left on the soil surface) and ridge tillage (in which crop residue is collected in valleys alongside ridges of soil that are planted) were practiced on another 26% of planted crops in the United States. This compared with 3% in 1984 and zero in 1930. Yet not all reductions in erosion result from producers' practices.
Between 1985 and 1992 the U.S. government's CRP program paid producers not to cultivate the most highly degradable areas (Runge and Stuart 1998). This is probably the most important cause for declining soil erosion. There have not been widely accepted studies on global soil erosion rates. Anecdotal evidence suggests that erosion is increasing in many areas though producers that it will destroy their ability to produce over time. For many, there is no other option. They do not know any alternatives.
