Erosion Down—Fingers Crossed

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The federal government’s latest assessment of how much soil is being washed and blown off our farmland contains some good news: between 1982 and 2007, erosion dropped 43 percent nationally.

The National Resources Inventory is conducted by the USDA’s Natural Resources Conservation Service and is probably the best gauge we have of soil erosion trends nationally. It combines field observations with remote sensing on non-federal land to develop its numbers.

According to the latest NRI, between 1982 and 2007, average water-caused erosion on cropland dropped from 4 tons per acre per year to 2.7 tons; annual wind erosion rates fell from 3.3 tons per acre to 2.1 tons.

Keep in mind soil scientists estimate that a soil erosion rate of around 5 tons per acre annually is “tolerable,” meaning a farmer can maintain crop productivity as long as the rate doesn’t rise higher. Whether it’s tolerable in the bigger scheme of things is another question.

A lot of factors can be credited for these nationwide drops in erosion rates. For one, farmers, some of the most innovative land managers around, have shown once again that when given the chance they can produce food in a way that doesn’t wreck future productivity. They adopted no-till, ridge till and other methods that reduce disturbance of the soil in droves, particularly during the 1990s.

And the USDA’s 1985  conservation compliance initiative, which required farmers to put in place certain measures if they wanted to keep receiving commodity program benefits, no doubt helped as well.

Finally, the Conservation Reserve Program deserves a big pat on the back. It was created by the 1985 Farm Bill, and by 2007 CRP had paid farmers not to crop some tens of millions of acres of environmentally sensitive land.

But—you knew that was coming—here are a few caveats to consider when looking over the NRI numbers:

• We have a little bit of the “low-hanging fruit syndrome” going on here. The bulk of the soil erosion reductions occurred between 1987 and 1997—erosion rates went from 2.79 billion tons annually to 1.89 billions tons during that 10-year period. According to the NRI, since 1997 we’ve seen those gains in erosion control flatten out somewhat (in 2007 we lost 1.73 billion tons of soil). But the trend lines are still headed in the right direction.

• New development took about 40 million acres of farmland during the 25-year period this NRI report covers. The acreage of prime farmland converted to other uses such as development is bigger than the area covered by Vermont and New Hampshire combined. It’s mighty hard to raise food on concrete—or to get precipitation to soak into that concrete and recharge aquifers.

•What will happen if farmers are tempted to switch more CRP acres back into crop production (as they have been doing recently) or if the federal government significantly cuts the program? What if CRP payment rates simply can’t compete with rising cash crop rental rates?

• One last caveat—and this is a big one: the latest NRI does not take into account what happened after 2007, when record crop prices made it even more attractive to plow up pastures and CRP land, and perhaps even drop a crop or two out of the rotation.

Anecdotal evidence is that in some localized areas at least, we’ve seen significant increases in erosion rates during the past two years. Weather events such as the 2007 and 2008 flooding in the blufflands and eastern Iowa, respectively, are the cause of some of that.

But raising corn-on-corn in intensive conditions may also be a factor. In fact, just a year ago some southwest Minnesota farmers were making troubling comparisons to the Dust Bowl when talking about wind erosion in area crop fields.

Let’s hope the latest NRI accomplishes two tasks: 1) allows farmers and conservationists to take pride in what they’ve accomplished; 2) puts us all on notice that we can’t take these gains for granted.

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