By Treena Hein
Over the past two decades, Ontario farmers have been doing less tillage, resulting in reduced water, wind and tillage erosion, and better general soil health. Recently, however, many growers are reverting back to tillage, especially after corn and before soybeans.
According to Adam Hayes, Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) field crops soil management specialist, fewer farmers are growing wheat and other cereals in the rotation. “A two-crop rotation of corn-soybeans is becoming more common, [but] this doesn’t support soil life very well.”
In any given year there can be challenges with no till or minimum till as with any tillage system, and the impact depends on the year, in Hayes’s view.
No matter what degree of tillage growers use, Hayes says they need to be conscious of having at least half their soil covered over the winter, using cover crops, residue or a winter cereal crop. “In the spring, a minimum 30 per cent cover after planting is essential to prevent soil erosion,” he notes. “In addition, putting aside the fact that we’ve had several wet springs recently, in years where it’s a bit drier, cover on fields helps soil retain moisture.”
Hayes has been doing trials with cover crops planted after winter cereals to try and get a handle on how much biomass they produce. “At this point, we still encourage farmers to interseed red clover with winter wheat, but if you haven’t had great success with that, there are many cover crops that will cover the soil and provide many other benefits,” he says.
Is minimum till sufficient?
On the subject of minimum till versus no till, Hayes believes minimum till done right can protect the soil very well from erosion and keep it healthy and productive, if there is a good rotation and organic matter is added. “But I like no till because there is very little soil disturbance, and the increase in organic matter is greater,” he says. “With no till, the earthworms are pulling the residue into the soil, crop roots aren’t being disturbed and the organic matter is broken down more slowly. But if 100 per cent no till is not going to work for somebody, I’m open to a minimum of tillage if the soil is kept covered.”
Hayes says there are many reasons farmers don’t want to try less tillage. Some just want to stay with what they have always done. Often the concerns are not justified. Minimum or no till (done right) can produce the most economical yields. “To encourage a farmer to try no-till or minimum till, I will point out the benefits, and also point out the provincial trials,” he says. “There have been a lot of studies and to be frank, it’s not a focus anymore as the results have been replicated many times. OMAFRA soybean specialist Horst Bohner has proven that no till is the best way to go with the bottom line for soybeans. Former OMAFRA wheat specialist Peter Johnson also [likes] no till for winter wheat and former OMAFRA corn specialist Greg Stewart [feels] strip till was a good option for corn.”
Hayes also points out the risk of erosion to farmers who haven’t yet tried reduced tillage. “Tillage increases the loss of organic matter and nutrients,” he says. We need to keep our soils in place and keep phosphorus in place. There is more and more pressure on growers to reduce phosphorus going into streams and rivers and then into the Great Lakes. There have been algal blooms a couple of times in the last few years and that’s a very bad thing.”
Hayes encourages farmers to try no till or minimum till on 25 to 50 acres, and to find a mentor in the vicinity. “Try it in the best-drained fields, fields with good fertility and to do it within a good rotation.”
Along with tillage, new Ontario research has found short crop rotations to negatively impact soil health and crop productivity. “The most common crop rotation in the U.S. Midwest is currently a corn-soybean rotation, and crop rotations in Ontario are following the same trend,” says Dave Hooker, a field crop agronomist and assistant professor at the University of Guelph, Ridgetown Campus. Hooker lists many reasons for shorter rotations, including technological innovations, economies of scale and government policies, but says most decisions on crop rotation are based in the short term. “However, long-term effects need to be factored into the decision, and until just recently, little information was known on the impact of short crop rotations on crop productivity,” he notes. “The long-term trials at Elora and Ridgetown have quantified the negative impact of short rotations and intensive tillage, and much of the impact is directly related to differences in soil health.”
At both the Ridgetown and Elora sites (two different soil types and environments), Hooker, along with Bill Deen and Laura Van Eerd, found that soil health tended to be the poorest in corn-soybean rotations, and similar to continuous corn or soybeans. “Although corn and soybean yields were relatively high or ‘satisfactory’ in the corn-soybean rotation, they tended to be much lower than yields in more complex rotations,” he says. “When wheat was included in the rotation, corn and soybean yields were five to 10 per cent higher, and the crops were more resilient during periods of excessively wet or dry weather.”
Hooker says analysis of the Ridgetown soil data with Laura Van Eerd also shows higher soil health scores where wheat was grown in rotation (compared to a corn-soybean or continuous corn or soybean system). “Soil response to cropping practices tend to be gradual,” Hooker notes
Hooker adds many growers make crop rotation decisions based on crop performance only, but that he and his colleagues are trying to encourage growers to perform an enterprise analysis using a multi-year systems approach. “Many growers do not credit the wheat enterprise with higher returns in the corn and soybean years,” he says. “When the wheat enterprise is credited with the higher returns in corn and soybean, the profitability of the wheat enterprise is much more competitive with soybean and corn.”
Hooker says reliance of nitrogen (N) fertilizer is less for corn following wheat alone (no red clover), and that N for corn can be reduced further by 70 kg N/ha if the wheat is underseeded to red clover. He says all of these “perks” for corn (and soybean) need to be credited to the wheat enterprise, because they would not exist without wheat. Hooker adds the inclusion of wheat also allows the opportunity for planting cover crops in the rotation, whereas limited opportunities exist for cover crop inputs in a corn-soybean rotation.
Hayes strongly believes if two-crop rotation use continues on a farm, soil health will decline significantly on those fields. “Smart farmers are putting together the pieces and seeing it for themselves,” he says. “If you are doing corn-soybean rotation, and you move to including cereals in a three-crop rotation, soil health gets better. It gets better still when you go to a six-year rotation and add a perennial crop like hay for a few years. It’s better still when you use minimum till or no till, and better yet when you add a cover crop after soybeans or cereals. The addition of organic material from manure and/or compost (grain bin waste, livestock and poultry bedding) will also improve nutrient cycling and soil health.”
“Try to do all that you can to improve your soil,” he concludes. “Long-term yields depend on it.”
Photo: A panorama of the long-term trial at Ridgetown showing wheat that is close to maturity. Photo courtesy of Adam Hayes, OMAFRA.