Researchers studying ground rolling soybeans
By Jean Caspers-Simmet
simmet@agrinews.com
Date Modified: 07/15/2010 4:05 PM
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KANAWHA, Iowa —Several studies looking at the effect of ground rolling soybeans are under way at the Iowa State University's Northern Research Farm at Kanawha.
A Humboldt equipment dealer gave the research farm a 20-foot Degelman land roller to use. The roller has a 42-inch drum made of heavy steel.
"One of the big questions is when do you roll," said John Holmes, Iowa State University Extension field agronomist in describing the studies at last week's research farm field day. "Some say before planting because it helps with better depth control and seed placement and the planter unit runs more uniformly across the field. Some do it that way. Some do it after planting to push down the seed and maybe get better seed soil contact. Another question is how late can soybeans be rolled?"
One study is looking at soybeans rolled prior to planting. Another one looks at rolling after planting. They rolled soybeans immediately after planting, at the unifolioate, late V2 to V3 stage. After last week's field day, they rolled beans one last time. They are looking at yield, plant population, rate of residue decomposition and water infiltration.
Holmes shared information from Jodi DeJong-Hughes, a University of Minnesota Extension regional educator in crops, who has studied the economic and environmental impacts of ground rolling and timing on soybean yield at four locations in Minnesota.
DeJong found that yields from rolled soybeans were not significantly different at three of the four sites. One location had a slight increase in yield when rolling occurred near planting vs. rolling when the plants were at V1, V3 or not rolling at all. Protein, oil and moisture content weren't affected.
Overall, DeJong-Hughes found that rolling had little effect on yield, plant population and rate of residue decomposition. She noted that producers mainly use rolling to increase combine speeds and to reduce the risk of harvesting rocks and dirt-laden corn roots.
Many farmers are using land rollers, Holmes said. Some farmers prefer to roll prior to planting to provide a firm seedbed. Others roll after planting to push small rocks and corn root balls into the soil so the combine header can cut at a lower depth.
There isn't much research on land rollers, Holmes said. The consensus of agronomists he has visited is that harvesting efficiency probably is improved. Yield increases most likely do not occur due to rolling, but more efficient combining probably does increase yield.
It's not a good idea to roll emerged soybeans, Holmes said. University of Minnesota research showed a yield reduction when soybeans were rolled at V3. There was no yield advantage when V1 or V2 soybeans were rolled.
Mahdi Al-Kaisi, ISU Extension soil management specialist, has expressed concern that large land rollers can destroy soil structure and soil aggregation and reduce porosity and soil infiltration rate, Holmes said in his May 10 Crop Happenings newsletter.
The Clay County Growers Plot at Spencer has a replicated study of soybean rolling, said Paul Kassel, ISU Extension field agronomist. They will to do residue cover measurements, stand count, harvest loss and yield comparisons.