By Treena Hein
By Treena Hein
In the summer of 2009, brothers Ivan and Brian DeJong decided to move about three inches of topsoil up an eroded sidehill on an experimental basis. Using a Reynolds scraper/earth mover, these owners of Youngfield Farms Ltd. (a cash crop and poultry farm north of Bowmanville, Ontario, east of Toronto) were able to boost the crop yield on an affected one-acre area in 2010 to 95 percent of the field average. “The yield increase was dramatic, as the area had historically averaged 50 percent of the field average,” says Ivan. “We also maintained the historical average on the flat area of the field where the topsoil was removed. We realized that by bringing the topsoil up the slope, we can grow a better crop, with more root mass and crop material to hold the soil.”
This is exactly the type of activity, known as mitigation or remediation of tillage erosion that Dr. David Lobb has been studying for more than 20 years. “Our analysis has shown there’s a three- to six-year payback period for all of the costs associated with putting the soil back on a hilltop,” says Lobb, a University of Manitoba soil scientist based in Winnipeg, who coined the term “tillage erosion.”
What matters most when cost-return is achieved is crop value. “Even if your yield on the slopes that you’ve worked on goes up, which it will, if you’re not getting a profit for your crops, then it is difficult to pay for any form of land improvement,” Lobb notes. “Obviously, the market value of crops is very important.”
Economic return also has much to do with what happens on the slope after the soil is moved back. “If you follow with conventional tillage, you’ll have to repeat the process after a while and that’s not economically wise,” Lobb notes. “To turn this practice into profit, you need to sustain the yield increases beyond the three to six years for payback. To keep the soil and the yields up on the hilltops for a few decades rather than a few years, you need to use no-till or reduced till.”
In their crop rotation, the DeJongs plant no-till soybeans into corn stalks, no-till winter wheat into soybean residue, and use spring tillage to plant corn. “We use vertical tillage with a coulter implement,” says DeJong. “Instead of moving the dirt from one place to another, it lifts dirt and puts it back on the same place.” He notes that the farm’s subsoil is more prone to erosion than its topsoil. “If we mix topsoil and subsoil together, which is what we do when we till eroded areas, it’s not as erosion-resistant as just having top soil and it’s also not as good to grow your crop,” he says.
In Lobb’s view, smooth and ripple coulters are preferable to wavy coulters. “Use a moderate, constant speed,” he advises, “and also avoid terrace-type efforts because every break in the field slope increases tillage erosion.”
That is, if a grower puts three breaks into a long slope, there may be a decrease in water erosion by as much as 50 percent, but now there is four times the tillage erosion.
One-pass seeding and fall harrowing is not a guaranteed method of eliminating tillage erosion. “Some zero-till is low disturbance, and some zero-till is high disturbance,” Lobb says. “We’ve compared and concluded that high disturbance seeders cause as much tillage erosion as a moldboard plow through moving a little soil a long way away and with a lot of variability.”
In other words, with high disturbance seeding, a grower can remove so much topsoil that he may never recover the productivity on an eroded hilltop, even when using zero-till for 20 years
Water and wind and tillage
In January 2011, DeJong attended Lobb’s presentation at the Southwest Agricultural Conference in Ridgetown, Ontario. “Lobb confirmed our view that in rolling ground, the primary form of erosion is tillage,” DeJong says. “It moves the most dirt. It’s obviously been happening over a long time period, but big equipment and higher speeds are making it worse. Also, there’s more row cropping now, whereas long ago, there used to be mixed fields where sod would be left.”
Lobb says that on the Prairies, loss of topsoil is almost completely due to tillage erosion. “Here, the soil is readily available to put it back on top of hills,” he observes. “In Ontario, at least in some areas, gullies are more prevalent, and in these cases, the soil that’s been moved to the bottom of a hill can be flushed away with water so there’s less available to put back on top.”
The good news for farmers is that while wind and water erosion actually degrade the soil structure, tillage erosion simply moves soil downhill like a conveyor belt. “You really don’t lose much in terms of quality,” Lobb says. The bad news is that tillage erosion is not confined to hills. “Many farms have flat or wet areas that need surface drains, and tillage erosion can fill in these small areas quickly,” he says. “While tillage erosion happens on every piece of farmland, farmers must strike a balance between how much to remove from the base and how much to add to the top.”
This is work for the fall, Lobb asserts, after all other field operations, are finished and could take many years to complete on a large farm.
“It’s great that farmers are realizing they can repair damage from tillage erosion, but I’d advise them to talk to a specialist about how much soil to place on knolls and where to take it from,” says Adam Hayes, the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) field crops soil management specialist. “We’ve included it in OMAFRA publications for about 10 years, and it’s also part of the soil management section of the Environmental Farm Plan, he says. “David’s research is helping us to raise awareness of the issue and how to address it.”
For more information: Read about tillage erosion in the Manitoba Agriculture, Food and Rural Initiatives Soil Management Guide at www.gov.mb.ca/agriculture/soilwater/soilmgmt/fsm01s00.html .