By Erika Mathieu
Dr. Maryse Bourgault shared her expertise on the subject of cover crops during Farming Smarter’s Field School on June 15.
Cover crops are traditionally fast-growing plants that offer benefits to farms through enhanced soil health, and as a strategy to improve biodiversity, control pests, and prevent or mitigate erosion. They differ from a farm’s cash crops insofar as cover crops are a strategy in farm management used to increase the conditions for more profitable cash crops.
Dr. Maryse Bourgault is an assistant professor and WGRF Chair in Integrated Agronomy at the University of Saskatchewan’s department of Plant Soil and Science. She also previously worked for Montana State University before relocating to Saskatoon in 2020 where she now focuses much of her efforts into researching cover crops in Western Canada. Currently Bourgault is one of the leading researchers on a multi-site cover crop experiment in collaboration with Dr. Yvonne Lawley at the University of Manitoba and Dr. Linda Gorim at the University of Alberta.
Bourgault said the experiments have so far led to some interesting questions on the topic of cover crops.
“What we are finding (is) after just one year of data in conversations about the kind of measurements that we want to take, is that the cover crops are behaving differently between these three sites. We are finding that there is a lot of interest right now in cover crops, but the advice we need to find for people needs to be locally relevant; the prairies are not uniform things.”
Bourgault said there is a growing interest in cover crops, and said just a few years ago this wasn’t the case when presenting at various roadshows such as the Hy-Line roadshow and events in Montana, “no one was interested,” and that was, “even with the U.S. providing some financial incentives for people to try. Things can change quite fast,” noting at least half of the students and farmers in attendance at the Field School expressed interest in cover crops.
Bourgault said with respect to ongoing research, “what we’re finding is that there are two challenges that we have with cover crops. (…) One: they are hard to establish, and two: then we have problems with weeds. These (issues) are sort of related as well because if you’re having trouble establishing your cover crops and they’re not competing against the weeds, then you are trying to encourage the cover crops to grow, you don’t necessarily want to use herbicides that are going to kill them.”
Bourgault said work is ongoing to examine the shoulder season where cover crop seeding is done immediately after harvest, “so that you have that cover and hopefully you still have some of that residue in the spring. We are finding that in some places, you just don’t have that time and space,” particularly on dry land such as the Saskatoon region. Bourgault added they are experimenting with timing and said strategies and timing of seeding should be calibrated toward, “what your season actually looks like.”
The ongoing research project between the three universities is also looking at the outcome of individual species as cover crops.
“We’re looking at clover mixtures, some of them annual, some of them biannual, we also are looking at alfalfa as well in Italian rye grass. So we have annual clovers and the Italian ryegrass that we know are going to die over the winter, but we also have some of those clovers and alfalfa that we know will survive that winter and come back next year. So we’re thinking maybe we need to establish some of those cover crops in the first year to get the benefits in the second year.”
The research will provide better insight into what some of the trade-offs and benefits are when employing different strategies.
“We focused a little bit more on having clovers in alfalfa because of their ability to fix nitrogen from the atmosphere and hopefully have some of that nitrogen in the system. Italian rye grass actually looked pretty good last year, so if you’re looking for cover, our Italian rye grass was the one that was the best for that.”
“We looked at phacelia in the wheat. It didn’t look like much at the beginning of the season but once it is flowering, it gets to a fair size and said the intent was not to kill the phacelia either as it was basically dead by the time the wheat was ready to harvest. It wasn’t too much of a problem but we do see that there are now phacelia seeds around these plots as well so part of the problem now is (deciding) do we want to keep the phacelia or do we want to kill the weeds?”
She explained the experiments are also looking into the application of different herbicides, and said the team of researchers are, “also hoping that maybe if the cover crop is established well enough (…) maybe some of that herbicide can just knock it off just a little bit so that you can still have a good competition from your cash crop and reduce that composition a little bit without actually killing it so that you can still have some of those benefits of having that cover later.”
There are often limitations to the duration of the experiments due to academic timelines for graduate students, who have a limited time to work on any given project.
“I am really interested in improving soil organic matter but that is the kind of thing that takes maybe 10-20 years before (you) can actually get a good measurement of change in soil organic matter, so it takes a while,” and said the question of, “how much of the short-term indicators will actually lead to long-term desirable changes. That is really up in the air. It’s really difficult. We tend to focus on things that are a little bit more immediate.”
Areas of more short-term study include studying nitrogen in the nitrate in the soil which can provide potential insights into how different cover crops may impact soil health in the long-term.
“We’re looking at if the decomposition of clover (cover crops) do actually result in more nitrogen. So it is not the soil health as a whole, but it is some indicators that maybe some of this is happening.”
“There is just so little scientific studies that have been published on cover crops in Western Canada that these are all questions that we all have and we don’t really have good answers to it. But biomass is a big part of that, too, so if we can actually find a way of getting good biomass in our cover crop without hurting yields of the cash crop too much then that would good.”
“I think there is a lot of interest and a lot of us are going, ‘we need to figure this out’.”
Bourgault encouraged students and farmers to stay connected with Farming Smarter and said much of the research effort between herself and the partnering universities has been seeking to fill some of the gaps in available data on the topic.
Follow the team’s research findings on Twitter @IntegratedAgUofS.