Rock ‘n’ roll soybean fields before harvest
If you have rocks, should you roll?
Soybean ground rolling is a fairly new soil-finishing practice in Minnesota, but it’s been catching on rapidly all over the state. Many farmers are asking questions about it: What are the benefits and risks? How does rolling affect yields? And when is the best time to do it?
Ground rolling prepares soybean or dry bean fields for harvesting. Large rolling drums 30 to 60 feet wide are pulled across the field to push rocks down into the earth, break up corn root balls and crop residue, and level the soil. That allows the combine cutter bar to be set low to the ground with less risk of picking up damaging rocks and root balls. And there’s less stress and fatigue for the combine operator.
• The main benefit of ground rolling is harvest ease.
• There’s no significant damage if done before V-3 stage.
• Ground rolling does not affect soybean yields.
Other advantages include lower harvest losses and cleaner beans. Rolling may promote residue breakdown, too, says Doug Holen, University of Minnesota Extension crops specialist. “It pushes residue down into the soil and cracks it, so there may be faster decomposition of organic matter.”
How late can you roll?
Soybean ground rolling is generally done immediately before or after planting. But spring workloads or wet weather often delay this field operation. “Farmers were asking, ‘How late can I do it and not damage the crop?’” Holen says.
To answer growers’ questions, U-M researchers and cooperating farmers did replicated trials in western Minnesota in 2008 and 2009. The field-scale trials looked at timing and the effects of rolling on stand counts and yields.
Soybean plots were rolled before planting, immediately after planting, at emergence, at V1 and at V3. The control plots were not rolled. Fields were rolled in the afternoons, when plants were most flexible.
The two-year study found that there was no significant damage to plants from any of the treatments, Holen says. Stands were about the same, and there was no yield disadvantage with any treatment. Two years of ground rolling trials at North Dakota State University’s Carrington Research Extension Center found similar results.
Tractor wheels actually caused more visible plant damage than ground rolling, Holen notes.
Ground rolling does raise the risk of erosion and soil sealing, reports Jodi
DeJong-Hughes, a U-M Extension tillage specialist. Surface residue helps protect soybean plants from rolling damage, she adds.
What’s it worth?
The research also found that it was less stressful to harvest the rolled fields. Of course, it’s hard to put a precise dollar value on this benefit. Land rolling costs range from $4 to $12 per acre, according to Iowa State University’s 2009 custom rates survey.
Land rolling may make sense on certain fields or for certain crops, Holen says, but on every acre? No. You’re more likely to see a return to this practice on higher-value crops, he says, such as seed soybeans or dry edible beans, where you may be docked at the elevator for dirt or stained seeds.
If you decide to try rolling soybean ground, here are some tips:
• Roll in the afternoon, during the heat of the day. Soybeans are most rigid in the morning and evening when plant cells are filled with water.
• Control wheel damage. Configure tractor tires and roller width to minimize the number of plants that fall under wheels.
• Don’t roll when it is wet. Bean plants will stick to the toolbar and pull out of the soil. Wet soil is more apt to seal after rolling, too, Holen says.
• Avoid rolling when it’s windy. I have observed more soil blowing off rolled soybean fields, perhaps because the surface is smoother and the soil finer. University of Minnesota research is looking at the effects of ground rolling on water erosion.
• Don’t use rolling to level ruts. With the difficult conditions for spraying and combining this year, ruts were common, but rolling won’t solve that problem, Holen says.
Gatchell is agronomy manager at Equity Elevator and Trading Co., Wood Lake, Minn. Find information and links to Minnesota certified crop advisers on the Minnesota Crop Production Retailers Web site, .
This article published in the January, 2010 edition of THE FARMER.