Long-term tillage and crop rotation
By Trudy Kelly Forsythe
Dr. Laura Van Eerd in front of a winter wheat plot from the long-term tillage system and crop rotation study at Ridgetown, Ont. Photo courtesy of Micah Shearer-Kudel, FARM & FOOD Care Ontario.
December 2, 2014 - Using winter wheat in crop rotations has long been known to benefit soil quality and crop production. It provides good coverage to prevent erosion, it holds moisture and it helps with weed management. Researchers in Ontario wondered how different tillage systems might impact the equation, so they conducted experiments at the University of Guelph’s Ridgetown campus to evaluate the effect of tillage systems and crop rotations on soil quality.
Their recently published paper, Long-term tillage and crop rotation effects on soil quality, organic carbon and total nitrogen, concludes that if farmers in southwestern Ontario incorporate no-till practices and winter wheat into their crop rotations, it will benefit production and soil quality over the long term.
“Other studies in Ontario have shown similar results with winter wheat, but this showed we can see higher carbon sequestration with no-till and adding winter wheat to the rotation to the three foot soil depth,” says Dr. Laura Van Eerd, associate professor of soil fertility and cover crops at the University of Guelph.
Van Eerd is co-author of the research paper, along with Dr. Katelyn Congreves and Dr. David Hooker, also from the University of Guelph, Ridgetown campus; and Adam Hayes and Anne Verhallen from the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).
“Soil health is more than just fertility and the ability of soil to do its job to produce crops,” says Van Eerd. “It has to hold water, filter water, hold life, have biodiversity and be resilient. A good quality soil will still produce a good crop, even in a stressful season, such as too dry or too wet, so soil’s organic matter is important.”
One of the challenges for researchers, and farmers, is that soil quality is difficult to measure. For this reason, Cornell University developed the Cornell Soil Health Assessment (CSHA), which measures the biological, chemical and physical properties of soil and assigns a score represented by a single number out of 100. “The higher the number, the better the quality,” explains Van Eerd.
Verhallen and Hayes wanted to see if the assessment would work in Ontario so they used it to quantify the soil quality of samples from field trials established by Dr. Tony Vyn and Doug Young in 1995 and maintained since 2008 by Hooker and Scott Jay. The long-term tillage system and crop rotation trial is on a Brookston clay loam soil. Each crop rotation – continuous corn, soybean-corn, continuous soybean, soybean-winter wheat and corn-soybean-winter wheat – was done under no-till and conventional tillage with the conventional tillage being fall plowed with spring cultivation.
“The trial was sampled 14 years later for the CSHA, soil organic carbon and total nitrogen,” says Van Eerd. “We collected soil up to three feet depth in five, 10 and 20 centimetre increments, took different sections of soil, and analyzed them for soil health.”
The researchers found that there was better soil quality with the no-till system than the conventional tillage system.
“That was true whether we used CSHA, soil organic carbon or total nitrogen as the test of soil health,” says Van Eerd, adding that, “in scientific literature, Cornell University found similar results with no-till using the CSHA.”
“The part that was surprising was with soil organic carbon,” she adds. “We are the first ones in Ontario to demonstrate higher soil organic carbon in no-till versus conventional to the three-foot depth.”
Van Eerd cites an Indiana study out of Purdue University which found similar results with higher organic carbon and nitrogen under no-till to the three-foot depth, but adds other Ontario researchers have found no difference with depth.
“It could be just our site’s soil texture, a clay loam soil; it could be our environment,” she says. “Now we need to look at more locations to see if there is also an increase in soil health with no-till and crop rotation.”
As for the crop rotation side of the equation, the researchers found they had better soil quality with winter wheat in rotation than without in terms of CSHA, soil organic carbon and total nitrogen.
Verhallen and Hayes also collected soil samples from four long-term trials in Woodslee, Elora, Ottawa and Delhi. Thanks to funding from the Water Adaptation Management and Quality Initiative through Farm & Food Care Ontario, Van Eerd and Congreves are now working with that data set to see how CSHA works with rest of Ontario.
Print this page