CHILLICOTHE, Mo. – From Alabama to North Dakota, U.S. researchers are growing crops only to run them down.
“You have to admit there is a certain, twisted appeal to running over a crop and flattening it for anybody in agriculture, farmers or researchers,” said Steve Shirtliffe of the University of Saskatchewan’s agriculture and bioresources college.
While rolling a crop flat onto the ground might make sense to begin the retting process to get flax fibre, knocking a crop down violently to kill the plants has few other applications in agriculture. That was the popular opinion until recently.
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In areas of the continent where the growing season is long enough to support a crop and a half, researchers have found significant success planting spring crops into flattened rye crops. They use them to control weeds without herbicides and prevent soil erosion. The rapidly growing, fall seeded crop outcompetes fall and spring weeds.
“It’s amazing to see these fields. The weed control is great and so are the soybeans,” said Shirtliffe.
Researchers at the U.S. Department of Agriculture are proving the strategy works.
Besides reducing soil lost through wind and water runoff, the single pass process helps the soil retain water.
Randy Raper of the National Soil Dynamics Laboratory in Auburn, Alabama, said rollers can save producers money on tillage and other inputs and provide them the one thing they can’t buy.
“Insufficient water lowers yields, it doesn’t matter where you are. So anything that stores water results in bigger crops,” he said.
“For organic growers, it means no-till is a real possibility. For conventional producers, it means fewer herbicide costs, reduced erosion and the chance to have a high biomass winter cover crop for no-till. Rolling is big,” he said.
Shirtliffe and colleagues at the University of Manitoba may not have a growing season and a half to play with, but for organic producers who regularly till a cover crop to enhance their soil nitrogen, rolling may provide an alternative.
“I think I probably said this in the past: ‘Zero tillage is impossible for organic production.’ I think I might have been wrong about that. We’ll see how the research up here goes,” Shirtliffe said.
He wasn’t alone in that opinion, until the rolling caught on.
For conventional or organic growers who face too much moisture, especially on heavy clay land, cover crops of fall-planted cereals may be appealing if they could also reduce the herbicide bill, say USDA researchers.
Shirtliffe said the Canadian season is likely still too short and water too scarce to have a fall rye crop flowering and ready to roll with time left to seed in spring.
“But as an alternative to tillage for plow-downs of cover crops like clover or peas, this could be very important technology,” he said.
USDA researchers said seeding into a mat of flattened cereals works out well providing the seeding takes place in the same direction of travel as the smashing.
Chris Lawrence, a USDA agrologist, has found that in working with American organic growers, the savings in tillage costs and labour more than made up for the yield reductions in soybeans seeded into rolled rye cover crops when compared to neighbouring heavily tilled crops. He said the savings were about $50 US per acre over tillage.
For conventional growers, the rolling reduced the cost of fuel, labour and herbicide, while yields were 25 percent less than conventional practices. Depending on crop prices, the practice can pay on a cash basis in some cases, say agrologists. The procedure requires more than running over the crop.
South American grain and oilseed growers have been using crop rollers for decades, but the technology there hasn’t been refined or heavily studied.
The USDA’s Agricultural Research Service has been evaluating roller design since 2001 and the use of rollers in terminating a cover crop since 1994. A sustainable agricultural production institution, the Rodale Institute, has also looked at crop rolling.
Both have come to conclusions and recommendations for design.
Rodale offers farmers free blueprints for a roller that incorporates crimping bars in a chevron pattern. The chevron lessens machine vibration and increases crop mulching more than either smooth rollers or those with straight bars that run perpendicular to the direction of travel.
USDA recently compared several roller designs and found three winners: a smooth roller with a crimper bar that ensures the crop is flattened; a traditional roller design with straight horizontal bars that run perpendicular to the direction of travel; and a roller with curved bars that twist along the roller. The latter is a design being patented by the USDA.
The three designs killed more than 90 percent of the rye by snapping off the stalks when it was in flower.
Each was pulled behind a tractor and mounted to a three-point hitch. Like the Rodale designs, they can be mounted in front, increased in size and gang mounted to a larger carrier frame with or without weights to create downward pressure.
The “crimp my rye” trials resulted in the discounting of the traditional flat bar unit because it has vibration problems that cause excessive mechanical wear and operator fatigue.
The curved bar unit, like the Rodale design, transfers the vibrations to the cover crop and performed just as well in killing the plants.
A smooth drum with a crimping bar performed best with the rye, snapping the stalks and leaving it flat in preparation for seeding.
However, it isn’t the choice for broad-leaf crops where a more violent mulching action is required.
“This exciting for organics,” said Brenda Frick, co-ordinator of organic research at the U of S. “Tillage is a major drawback and cost in the system and the erosion it causes is an unfortunate byproduct of the system that otherwise strives to be very sensitive to the environment.”
Shirtliffe said the chevron designs work well for prairie producers looking for an alternative method of terminating a cover crop. Nutrients from the terminated crop pass into the soil and the plant material is effective at retaining moisture and reducing weeds.
He said more research is needed to provide a recommendation that says, “yes, this is the way to go for organic no-till. But it looks very promising.”
To see more, visit www.newfarm.org/depts/notill/roller_gallery/index.shtml. Want free blueprints to build your own? Check rodaleinstitute.org/notill_plans.
