Soil erosion and compaction – Part 2


We talked about structure in that if you
do more and more tillage, you’ll break these aggregates apart into smaller and
smaller pieces. Clay, a single particle is actually microscopic and it can
blow away in the wind very easily. In western Minnesota and into the Dakotas
we have a real wind issue because we have very flat soils. We don’t have a lot
of trees around or shelterbelts and if you do more and more tillage
you’re going to have more of an erosion problem. I’ve been out in fields where
they’ve actually lost all of their topsoil and they are now farming what
they call the yellow clay knobs. We’re sitting where they had dug out the
pit and this is where the backhoe had scraped that soil. You see how smooth it
is and when it dries this is very hard for a root to penetrate. The organic
matter is gone in this soil. In our organic matter, you know, we have our
nitrogen, our phosphorus, our sulfur and we don’t have the structure in the soil
that we do when there’s organic matter. So this soil is great for holding water
but I don’t want to plant my plant into it. If you see those yellow clay
knobs out in your field, know that you have lost the topsoil and are now
farming the subsoil. The ARS in Morris, they went out and studied these fields that had the yellow clay knobs out there. They tracked how much soil had been
moving down a hill. Now this was a highly erodible hill and the farmer was doing
moldboard plow, so it’s kind of the worst of all situations there. What they
found is that the tillage moved soil down the hill faster than rain and
wind did. What they found is that 27 tons of soil were moved per acre per year
on this field. Then where they loosened up that soil, that’s where rain
could get ahold of these smaller particles and move them down the hill.
It was moving about nine tons of soil per acre per year, so in this highly
erodible field, they were losing 36 tons of soil per acre per year. When they
went out and did wheat yields out there, they found that on the clay knobs they
were getting about 43 to 45 bushel an acre. Where the soil
had accumulated at the bottom of the hill. they were getting 90 bushel an acre.
It was also different in pH, in the salts, in the nutrient content and in the
organic matter content. As a farmer or a crop consultant, how do you manage a
field that has that much variability?

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