The information from the Iowa Daily Erosion Project paints a grimmer picture than a recent assessment by federal officials. The U.S.D.A’s 2007 National Resources Inventory, released last year, estimated that erosion in Iowa averaged 5.2 tons an acre each year. That was slightly higher than the five tons per acre that the department estimated was a tolerable annual rate of erosion for most Iowa soils. (Soils “regenerate” 0.5 tons per year, so even our “acceptable” levels lead to a net loss of 4.5 tons per acre per year.)
While the federal report estimates average rates of erosion for states and regions over a full year, the Erosion Project uses detailed information on rainfall and field conditions to estimate soil loss in 1,581 Iowa townships — nearly all of them — after each storm. Last year, according to Erosion Project data analyzed by the Environmental Working Group, the average estimated rate of erosion exceeded the sustainable level in 133 townships. In 2009, an estimated 641 townships exceeded the sustainable rate, including nearly 400 that had double or more that rate.
The project also provides a picture of the erosion caused by severe storms, like the one that dumped more than seven inches of rain in parts of southwest Iowa in May 2007. In a single day, the figures show, 69 townships had average estimated soil losses of more than 10 tons an acre. Of those, 14 townships were estimated to have an average loss between 20 tons and nearly 40 tons per acre. The 2007 storm was exceptionally damaging, but severe storms are becoming more frequent, according to a state report on climate change submitted in January to the Iowa Legislature and governor. (Around here, it pains me to see after every 2-3 inch downpour in the growing season when the crop canopy isn’t full (Oct-June) to see the gullies deepen. Finally, when it gets hard to get equipment across the gullies, the farmers get out blades and push surrounding soil into the gullies, so it can wash out again during the next big storm. These farmers don’t ever plant grassy waterways – and they are getting your tax dollars!)
But agronomists say that heavy erosion in unprotected areas can significantly diminish crop yields, and, over time, land that is not well cared for can become depleted. That means farmers must use more fertilizer to increase yields. (On our farm, there is a noticeable drop from our land to the adjacent crop field – most people estimate that half the original topsoil is already gone.)
More than anything else this year, farmers are making decisions based on how they can best take advantage of corn and soybean prices, which have soared in recent months. Dr. Cruse said that creates a paradox. When crop prices are low and farmers are scraping by, many say they cannot afford to take steps to protect their fields from erosion. Now, he said, they say they still cannot afford it because there is too much profit to be made from farming every bit of land. The same incentives have landowners clearing steep hillsides or converting pasture to cropland to cultivate or rent out. (Last year 17 acres of steep pasture adjacent to our farm was plowed up into cropland.)
Seeing the richest soil in the world washed away by careless practices is one of the hardest parts about driving home. It might not affect the current generation much, but it can’t continue if we are to maintain the ability of the land to produce crops for those that follow us. It also pains me to know that many (in this county alone) of those farmers have received millions of dollars out of the public treasury.
Maybe tomorrow we can return to prancing lambs or budding branches.
(From an article in NY Times, italics mine)