Rain we really didn’t need and the erosion it brings…

In the fall of 2012 our creek was completely dry. If I am not mistaken, that was the first time since 1982 when we moved to the country, that was that dry. (1988 might have been that dry but I don't remember.)

In the fall of 2012 our creek was completely dry; if I am not mistaken, it has not been dry since before 1982. (1988 was very dry too.)

My rain gauge on May 27. We just got another 1.4 inches of rain this morning. Since May 19 we have received 4.9 inches of rain in our neighborhood.

My rain gauge on May 27. We just got another 1.4 inches of rain this morning. Since May 19 we have received 4.9 inches of rain in our neighborhood. Notice the young corn in standing water.

Last fall and winter the Four Mile creek tributary nearby was completely dry. Just now when I went out to check our rain gauges, I found 1.4 inches of rain from this morning and water behind the terraces. In six months we have gone from one extreme to another.

One of the ways we prepare for these extremes is to integrate soil conservation into our farms: waterways (natural swales within fields that are permanent grass valleys for the excess surface water to flow through),  filter strips (strips of permanent grass along creeks and streams that help slow the flow of surface water into those creeks and help hold any top soil that might be in that surface run-off), and terraces (low soil dams built across areas in fields that stop water flow and allow that surface run-off to recede slowly through underground drainage tile). The federal and Iowa state governments both have programs to share the cost of these soil conservation measures with the land owners. They often, if funding is available, have about 50% funding available. Land owners must apply for funding, but there are not always sufficient funds to meet the demand.

Very important also are tillage practices. Most farm operators in our area chisel plow their corn stubble after harvest so that the soil is loose and partially exposed over the winter. This allows for more water and wind erosion than in fields that are not tilled in the fall. Soybean ground usually is left alone over the winter, though, most farmers do inject anydrous ammonia in late fall which does the disturb the soil a certain amount. Moldboard plowing was the most common tillage practice from the time our European immigrant ancestors first started breaking the prairie sod here in Iowa with horse or ox power, beginning about 1850, until about 25 years ago. With moldboard plowing the soil was completely turned over burying the stubble. With chisel plowing, the soil is shattered into clods with vertical knives and a certain amount of stubble is left on top. Other tillage methods which do not disturb the soil at all after harvest include no-till and strip-till (although with strip-till farmers sometimes create the strip they will plant into in the fall so that they are ready for planting in the spring). Another option is to mix in a cover crop with a no-till system (a crop that is planted in the fall after harvest which holds the soil and improves the health of the soil). In this vidoe, Dan Forgey at Cronin Farms near Gettysburg, South Dakota speaks about his experience with no-till plus cover crop.

Wind erosion of our Iowa top soil is not as common a topic of conversation as water erosion is. That is partly because the effects of water erosion are more easily identifiable when we drive through the countryside after a storm. However, there are two clear indications that we also suffer from wind erosion. One is that in the winter when we have snow and wind, we often see black topsoil on the snowdrifts in the ditches. I was reminded of the other indication just now when Cindy was on the house roof cleaning out the roof gutters. I watched her throw handfuls of spruce needles and muck down from the roof. The only way that topsoil could have gotten into the roof gutters is from the wind blowing it up there in one way or another. This Iowa data from 1997 shows that we lose less topsoil to wind erosion than water erosion.

This lost top soil is a serious matter, although we do not often figure it into our balance sheets. Mike Duffy, an Iowa State University extension economist has recently written about the value of Iowa topsoil in an article titled Value of Soil Erosion to the Land Owner.

In June a nearby field showed the effects of heavy rains and row-cropped hillsides. This is serious erosion. The topsoil lost here will likely never be recovered.

In June a nearby field showed the effects of heavy rains and row-cropped hillsides. This is serious erosion. The topsoil lost here will likely never be recovered.

When we discuss soil erosion, we must also acknowledge the role it plays in water quality. Why are these two phenomena connected? The reason is that eroded topsoil finds its way into our creeks, streams, and rivers and not only contributes to the silt content of the water, but soil particles also contain other substances, both natural and synthetic, which can degrade the water quality for wildlife and human life. Water treatment plants such as the one that supplies the city of Des Moines and surrounding areas, spend a lot of money on advanced equipment and processes to make the water fit for human use. Our farming and conservation practices in the watersheds of Iowa (both rural and urban practices) do influence that quality of the water we drink.

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