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. ©