Extension Ag Update
January/February 2007
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Erosion Rates in Illinois Holding Fast

Doug Peterson; dgpeters@uiuc.edu; (217) 333-9444

There is bad news and good news for soil erosion trends in Illinois.   The bad news is that the percentage of Illinois land with acceptable levels of soil erosion did not go up in 2006 and has been virtually unchanged since 1997. In 2006, 85.8 percent of the state’s cropland had acceptable levels of soil erosion.  The good news is that the vast majority of the remaining land with excessive erosion is very close to being brought in line, said Bob Frazee, University of Illinois Extension natural resources educator.

When land is kept within the soil-loss tolerance level, or T level, that means soil is being replenished faster than it is being lost through erosion. According to Frazee, about 10 percent of the cropland in Illinois exceeds tolerance levels by only one to three tons of eroded soil per acre annually.   “With some slight adjustments in management systems to retain more crop residue on this land, these acres could easily be brought to T or below,” Frazee said. If that should happen, the percentage of land with tolerable erosion levels would jump from 85.8 to nearly 96 percent.

The Illinois Department of Agriculture conducts the Soil Erosion and Crop Tillage Survey every two years, along with the Natural Resources Conservation Service and the state’s soil and water conservation districts. The 2006 survey also showed that soil-saving management systems, such as no-till, continued to dramatically increase in popularity. But this raises the question: Why haven’t these tillage changes translated into even more land coming within the tolerance level?

One reason is that a lot of the land shifting to no-till has come from mulch-till systems after corn, which also provide considerable erosion-control thanks to the heavy layer of stalks on the ground, Frazee said. Because erosion on most of the mulch-till land was already below the T level, the switch to no-till didn’t change the figure.  Although the 96-percent mark is clearly within reach, Frazee said the final four percent will be much tougher to bring within tolerable levels. This land has erosion rates that are more than twice the tolerable level.  But whatever the fate of the remaining land that still exceeds acceptable erosion levels, the current 85.8 percent mark is still far better than in 1982, when only 59 percent of the land had tolerable erosion rates.  And that, Frazee said, is ultimately good news.