Charles Schmidt knows it takes time and money to do deep tillage — or “subsoiling” — on his eastern Alberta farm, but he says the treatment makes a big difference. It determines whether a field is worth farming.
He can put the time, effort and expense into growing a 15-bushel-per-acre wheat crop, or he can deep till and at least have the potential of getting a 40-bushel crop.
“I know there are no guarantees when it comes to farming,” says Schmidt, who farms about 9,500 acres at Chinook, in a noted dry-land region about four hours east of Calgary. “The weather plays a huge factor, but I figure we might as well do what we can and aim for a 40-bushel crop.”
Schmidt estimates the deep tillage, which is done with a modified Kello-bilt deep ripping tool, costs him about $40 to $45 per acre just to rip the hardpan or solonetzic soil to a depth of about two feet. After that he needs to cultivate the field once or twice to get it fairly level and he also has to pick rocks. The treatment should have a lasting benefit for 12 to 15 years.
“My goal is eventually to do the whole farm,” he says. “I see it as just an ongoing process. We try to do 300 to 400 acres per year, as time permits — because it does take time — and just keep it as part of our farming practices.”
Schmidt follows roughly a 50-50 cropping and summerfallow rotation. In 2008, he cropped about 5,200 acres with about 4,300 acres in chemfallow. He was able to deep till about 300 acres in 2008.
He farms in an area with solonetzic soils — which are prone to form a hardpan. Schmidt, who has cut through some areas of solonetzic soil with an earth mover, says it has the consistency of “goose eggs.” The soil can set up to form an impervious layer. “You get a nice one inch rainfall, and you end up with two-and three-acre lakes in your fields which drown out anything that was growing,” he says.
In some fields he has only a two-or three-inch layer of top soil before he hits the hardpan, and he doesn’t know how deep the hardpan layer is. With the Kellobilt tool, he can rip the layer to a depth of 24 inches, but doesn’t get through it or below it.
Schmidt says solonetzic soils have an imbalance of calcium and magnesium (too much magnesium). Adding compounds such as gypsum or flyash from coal and woodburning industrial operations — all high calcium sources — is an option, but may not be economical.
“So he uses deep tillage, which mixes the soil and helps change the chemical composition of the soil,” he says. Deep plowing is a soil mixing process whereby calcium in the deeper lime-salt layer is mixed with the hardpan allowing for an exchange reaction to occur. Calcium replaces the sodium on the clay particles, thus improving the soil structure and preventing the reformation of the hardpan. In addition to improving soil structure, lime (calcium carbonate) brought to the surface will raise the topsoil pH, which will further improve soil productivity, particularly for acid-sensitive crops such as the legumes and barley.
Schmidt began using the Kellobilt deep ripping tool about 10 years ago. It’s 11-feet wide with five shanks on two-foot spacing. Each shank has a three-inch wide hard-surface tip. Schmidt welded a two-foot long section of grader blade to face of each shank to increase shank strength and soil disturbance.
Each shank requires about 100 horsepower of tractor power. With an optimum operating speed of about five miles per hour, he pulls the deep ripping tool with a John Deere 9620 tractor.
Schmidt, whose crop rotation includes mustard, barley, wheat and sometimes peas, says the deep tillage makes the difference between getting an economical yield or not. In a reasonable growing season, barley yields on deep tilled soils can be as high as 75 bushels per acre, compared to untreated areas where it might average 35 bushels per acre, he says.
Similarly with wheat, yields on treated acres can average about 40 bushels per acre compared to about 15 to 20 bushels per acre on untreated soils.
Lee Hart is field editor of Grainews, based in Calgary. Contact him at 403-592-1964 or by email at [email protected]