November 20, 2015
When you live in the Red River Valley like I do, it’s sometimes hard to imagine why conservationists and soil experts are sounding the alarm about the loss of topsoil.
When I’m digging a post hole or a foundation footing by hand on my farmstead, I get tired long before I get to the clay subsoils. In some places on my property there is three or four feet of black soil before I get to the sticky yellow clay.
Sure, I notice some wind erosion in the winter -- the black snowdrifts in ditches next to bare fields are clear evidence. But if the ditch fills up with silt, can’t you scoop up the soil up and put it back in the field? It’s not a big deal, right? At least that’s what I thought.
Snow drifts across a road in the Red River Valley.
But then I came across the following article from David Franzen, North Dakota State University Extension soil specialist, in the May 2015 North Dakota Crop and Pest Report:
“My colleague, David Hopkins, and his graduate student Brandon Montgomery worked on a project where they visited the exact locations of several soils characterized in about 1960 by the Soil Conservation Service … One soil in Walsh County, N.D., had 34 inches of soil above the C horizon [unadulterated, little changed parent material]. When they visited it in 2014, there was 15 inches of soil above the C; a loss in 50 years of 19 inches of soil.”
So where did the soil go? Why didn’t the farmer just put it back?
“Last winter, we had the unhappy reminder that we live in a very windy place. The Fargo radio was abuzz with calls about ‘black snow’ and some suggested that it was from oil-field flaring. The real reason was that the fall favored tillage, and many acres were tilled; and many were tilled to excess. Particularly at risk were fields of prevent plant from 2014 that were not seeded to cover crops in the fall, but were tilled several times. Snow did not stick to these fields and soil blowing was particularly bad. Nearly all fields that were tilled lost soil.
“Many farmers think that the only soil that moves is what they see in the ditch. Wind erosion of soil is always three-dimensional. Soil moves with surface creep (usually larger particles that start to move), followed by saltation (particles hitting particles, combining particle energy with wind energy to move the larger particles into the air) and suspension (usually small clay/silt-sized particles, at least with winds less than 50 mph). Soil moving by surface creep moves into the ditch and into the neighbors fields. This is what we see.
“Suspended soil is the real soil loss, estimated at about 10 times what you see in the ditch. Suspended soil does not land in the ditch, it lands in the Atlantic Ocean, or Ohio, or Pennsylvania, or New York, or London. It is lost forever.
“Can you really call it topsoil anymore? The ‘topsoil’ is a weak blend of a small amount of the original topsoil mixed with a large amount of subsoil. Farmers seldom see the effect of soil loss, because they mask the effects with tillage. There is no check to show what the soil could have looked like without soil loss. Go out with a chisel plow, blow black smoke out of the top of the mega hp tractor and mixed what’s left with stuff underneath and when you finish it still looks black to you. But it’s not as black as it used to be. In most places of the Valley, original top soil depths were 18 inches to 2 feet. Now, about a foot to about 6 inches is all that’s left. In 50 years, most Valley top soil will have about 3% organic matter. It used to be 7-8%. I visited with sugarbeet growers from Kazakhstan a couple years ago. During our interpreter exchange back and forth, they commented that they used 200 pounds N per acre on their sugarbeets. I told them that if our growers used 200 pounds of N on their beets, they would grow very large, low quality beets. They related they had to use 200 pounds of N per acre to achieve over 20 ton yields with 17-18 percent sugar. What they were telling me was that their organic matter went away over the past 1,000 years, and they have to apply everything the plant needs, whereas right now our growers use about 130 pounds of N to achieve similar yields/quality as our Kazakhstan counterparts. Our Kazakhstan competitors have to use 50% higher N rates than our farmers do because their organic matter went away.
“I had a grower from Minnesota email me after a wind erosion presentation in that state and write that he had to till to have a good seed bed and deal with residue. He told me that he knew he was losing some soil and organic matter, but his fields had a lot and what did it matter? The statement shocked me, but I replied that farmers often state that they are ‘Stewards of the Soil’. I asked if he knew what a Steward was. A Steward is someone entrusted with something with the understanding that it will be returned in the same or better condition than when it was given. I asked him how his statement of ‘what did it matter’ jive with being a Steward. I received no reply.
“The answer to soil loss is no-till or modified no-till, such as strip-tillage. ‘Minimum tillage’ will eventually result in the same thing as tillage, it just takes longer. There are successful farmers in every corner of the state that are using no-till or modified no-till systems. It is important that conventional till farmers pay attention to what the neighborhood no-tillers are doing, attend conservation educational events and field days and change their thinking from ‘No-till equals No-farm’ to ‘No-no-till equals my kids will work somewhere else.’”
By my rough calculation, unless something different was done on the Walsh County field, it will lose another .38 inches of soil this winter. After another 50 winters, the black topsoil on that field may all be gone.
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