A large majority of farmers in Western Canada have adopted zero-till systems — with the exception of those in the Red River Valley who are dealing with heavy, wet clay soils where tillage is just a fact of life. Most farmers understand the many benefits of zero till, such as prevention of soil erosion, better moisture retention and improved soil structure and soil organic matter content.
But tillage has been suggested as a partial solution to some disease issues and management of some weed species.
Does some kind of tillage operation — for a specific reason such as disease management or weed control — have a place in a no-till system in Western Canada?
Yield and disease
The last study that specifically looked at the impact of tillage on crop yields, weed numbers, foliar disease and nutrient availability in a long term, zero-till system was done from 1999 to 2002 by Byron Irvine, Alan Moulin and others at Agriculture and Agri-Food Canada’s Brandon Research Centre.
The study found that a tillage operation in one year of a three-year rotation, which included canola, did not reduce disease levels or yield. “If you really wanted to have an impact on disease you’d probably have to till with some sort of a plow and get full inversion, and that’s not realistic in our environment,” says Byron Irvine, director of research development at AAFC’s Brandon’s Research and Development Centre. “We were doing stuff that was realistic for people to do in our environment and the impact was really negligible.”
Weed numbers increased by up to 30 per cent in the tillage year and were higher the subsequent year, but returned to previous levels the second year after tillage, indicating that a single tillage operation won’t have a long-term negative effect on weed pressure or yields.
”We came to the conclusion that the world didn’t fall apart when you went back to doing a little bit of tillage when people are doing it because they really had a need for it,” says Irvine. “That was the premise of the work in the first place.”
An individual decision
“Where we have seen people using tillage more over the last decade — especially across the Eastern Prairies — is where due to wet springs and wetter periods, they’ve rutted up fields with high clearance sprayers,” says Irvine. “I know of at least a few committed zero tillers who have gone out and tilled their fields once or maybe more times in year just to try and level it out so they could actually traffic the fields again and then return to zero tillage.”
No studies have been done to show the long-term effects of shifting from a zero-till system to a conventional system, because it’s simply not something that happens in Western Canada, and isn’t likely to happen in the near future. “The tillage study that we did was very short term and it didn’t reduce the amount of mineralizable nitrogen which can affect soil organic matter accumulation,” says AAFC researcher, Alan Moulin. “To put this into context, because we started with land that had been in a long term zero tillage, there was a considerable pool of mineralizable nitrogen to start with. So the proportion of mineralizable nitrogen that was lost by that one tillage operation related to that large pool was not significant.”
“Our data suggests you can make decisions about tillage without fear of destroying your field ecosystem,” says Irvine, who adds that the decision of whether to till or not comes down to each individual farmer’s situation and needs. “Tillage of soils which are very prone to wind or water erosion should be approached with a great deal of caution.”
It all comes down to managing risk, says Moulin. “One of the most obvious things that happens with a tillage operation is that there’s a flush of weeds that producers have to be prepared to deal with,” he says. Irvine adds that “We already have good, herbicide tolerant material, so there are good opportunities to control those weeds, but when you have 30 to 40 per cent more weeds coming, and you already have a lot of them, it’s even more critical to control weeds early.”
“There isn’t a single answer to whether you should till or not,” says Irvine. “It depends how it fits into your farming operation and why you are doing it? If you can’t answer that question with a solid ‘I’m doing this because I want to solve a particular problem,’ then you’ve got to ask yourself, ‘Is this right for me?’ It may or may not be. We’ve got a lot of very capable agronomists and farmers out there, and they’ll have to think this one through for themselves because it’s so different depending on your agro-climatic area, and your soils, and the crops you’re growing and your equipment base.”