Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
1/15/01
- Contacts:
Jim Russell, Department of Animal Science, (515) 294-4631, jrussell@iastate.edu - Wendy Miller, Iowa Beef Center, (515) 294-9124, wmiller@iastate.edu
ISU Study Tackles Grazing Compaction Issues
AMES, Iowa -- Soil compaction from cattle grazing cornstalks may not be as great a concern as once believed, according to preliminary results from an Iowa State University and USDA National Soil Tilth Laboratory study.
"Cornstalk grazing really is one key to profitability in Iowa's cow/calf operations," said Jim Russell, Iowa State University beef cow-calf nutritionist. "Feeding hay to cattle through the winter can cost upwards of $1.25 per animal per day. Allowing those same animals to graze cornstalks costs, at a maximum, 25 cents per animal per day. The savings are obvious.
"However, many producers are concerned about the soil compaction they believe grazing can cause," Russell continued. "Therefore, ISU and the Leopold Center decided to study grazing effects in conjunction with studies the university is already conducting."
Compaction has always been a question among beef producers. In the early 1990s, ISU and USDA-National Soil Tilth Laboratory researchers completed a study at the university's Beef Nutrition Research Center near Ames and found no compaction. However, the Soil Tilth Laboratory researchers concluded that the top soil studied was deep with very little clay -- a "forgiving" type of soil.
"This conclusion led us to wonder what happens in other parts of the state where soil types may not be as forgiving," Russell said. "We began our most recent study last winter at locations in Atlantic, Iowa, and Chariton, Iowa."
The top soil at the Atlantic site is about 24 inches deep and composed of nearly 20 percent clay. The Chariton site is 11 inches deep with 30 percent clay.
The project, funded by the Leopold Center, is a collaborative effort of researchers from the ISU Animal Science Department, ISU Extension, USDA National Soil Tilth Laboratory and USDA Natural Resources Conservation Service.
Researchers are measuring "penetration resistance" - the amount of pressure it takes to press a specialized instrument a pre-determined depth into the ground - surface roughness, crop yields following winter grazing, and other measurements
After the first year of studies, the results were quite interesting. "We found no difference in penetration resistance between the grazed and ungrazed paddocks in Atlantic, however, there was a higher amount of surface roughness in the grazed paddocks," Russell said. "Exactly the opposite was true in Chariton. While penetration resistance was higher there in paddocks grazed when the soil was not frozen, surface roughness was reduced."
Soybeans were planted using no-till and disking at both test sites last spring, and no effects of corn crop residue grazing on subsequent yields were detected at either location.
"Preliminary evidence shows that allowing cattle to graze cornstalks throughout the winter does not cause enough compaction to affect soybean yields," Russell said. "We will plant corn at the test sites this spring, and it will be interesting to see what, if any, affects grazing will have on subsequent corn yields."
ml: isufarm
Extension programs are available to all without regard to race, color, national origin, religion, sex, age, or disability.