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Soils produce plants to feed humans and animals and are
critical for our hydrologic cycles and water quality. Soils
hold rainwater, decrease flooding and store water for use by
plants. Sunlight is converted to heat at the soil surface,
so soil serves as a regulator of climate. Soils that are
rich in organic matter and certain clay minerals (like those
of Iowa) serve as the earth’s filters and remove many of
pollutants.
The most recent average erosion estimate for Iowa is 5 tons
per acre. That means every year, on average, 10,000 pounds
of soil per acre move from one location to another. So, for
an average corn crop of 200 bushels per acre, about a pound
of soil moves for each pound of corn produced. For an
average soybean crop of 50 bushels per acre, this means
about 2 pounds of soil moves for each pound of soybeans
produced.
Iowa soils are geologically young, having only recently been
disturbed by human activities. Today, many of Iowa’s soils
remain incredibly productive, thanks largely to the organic
matter they contain. This organic matter was created and
stored over several millennia by Iowa’s tall grass prairies.
Although the organic matter in Iowa soils is no more than 50
percent of what it was when the soils were first tilled, an
average acre of Iowa soil will still mineralize 150 pounds
of nitrogen through the decomposition of organic matter.
Corn production requires about 275 pounds of nitrogen per
acre. Only about half of that nitrogen comes from fertilizer
or manure; the rest comes from nitrogen mineralized in the
soil. Soil organic matter provides an unseen nutrient source
for Iowa farmers and allows them to use the crop production
practices they currently employ.
We believe there is nothing more important to Iowa and its
future than our soil and have begun discussing creation of a
Soil Science Institute to better focus our science for
managing and maintaining Iowa’s most valuable resource.
— Kendall Lamkey, chair,
ISU Department of Agronomy
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