Grazing Corn Stalks Does Not Compact Soil
for Future Crops
by Nancy Carver Singleton
Grazing cornstalks does not increase soil compaction or reduce yields,
according to a study by Iowa State University and the USDA National
Soil Tilth Laboratory.
"We have not seen any large difference in penetration resistance,
which is a measure of soil compaction. Similarly, we have not seen
any difference in soil bulk density," said Jim Russell, an ISU
beef cow-calf nutritionist. The study did show some surface roughness,
which researchers attributed to hoof prints.
But there were no effects on soybean yields, with the beans planted
using disking and no-till. "That (no-till) might be the biggest
surprise for people," Russell said. Many producers, he explained,
are skeptical about germination when soybeans are planted by no-till
on grazed corn ground.
Test plots were in a corn-soybean rotation. Since soybean yields were
unaffected the spring after cattle grazed, soil tilth lab researchers
elected to not test corn yields. "It is very unlikely there would
be any effects on corn yields two years after grazing," Russell
said.
His research arose from long-time producer concern about compaction
problems. An early 1990s study in central Iowa showing no compaction
was done in an area with deep top soil and very little clay. "This
conclusion led us to wonder what happens in other parts of the state
where soil types may not be as forgiving," he said.
The resulting three-year study is in its final year. One project site
at Atlantic in southwest Iowa has 24 inches of top soil and nearly
20 percent clay. The other at Chariton in south central Iowa has 11
inches of top soil and 30 percent "high amount" of clay.
Ground was divided into paddocks at each project site and ungrazed
paddocks served as controls. Cattle were moved every 28 days among
five paddocks of corn stalks.
He pointed out that producers may want to use strip grazing, which
is moving cows among several fields or dividing a field into paddocks.
Otherwise, cows tend to eat more desirable portions, such as the grain
and husks, and then skip the stalks. "By controlling access to
some extent, you still maintain high quality of corn stalks in the
winter, which is particularly important for spring calving cows,"
Russell said.
The compaction study was also initiated because corn stalk grazing
is one key to profitability. Russell cited results from ISU Integrated
Resource Management Standard Performance Analysis Records that show
there is a direct relationship between the number of corn stalk acres
grazed per cow and profitability of the cow-calf operation.
Russell estimates the cost of grazing corn stalks at 25 cents per
cow per day, which includes the cost of supplementation. In contrast,
the cost of feeding hay ranges from 75 cents to $1.25 per cow per
day, based on hay costs of $50 to $100 per ton. ISU researchers have
found "year in and year out" that the consistent rate of
corn stalk-to-hay savings is about 15 percent, he said.
"Corn stalks are just a tremendous resource in this state. If
you get dramatic, there are 12 million acres of corn in the state.
If we graze every cow on corn stalks and provide enough corn stalks
to feed no hay, which amounts to allocating 6 acres per cow, we would
still use only two-thirds of the corn stalks," Russell said.
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