Intercropping peas and canola revisited
By John Dietz
Research on an old idea, intercropping peas and canola, is underway at Melita, in southwest Manitoba, by the Westman Agricultural Diversification Organization (WADO). The old idea could be a new cropping option for grain and oilseed growers who already depend heavily on canola. “If you are used to straight cutting canola, you wouldn’t have any problem with this system,” says Scott Chalmers, diversification technician with Manitoba Agriculture, Food and Rural Initiatives in Melita. That is on the harvest-and-separate aspect, but there is much more. Intercropping is unfamiliar today, where virtually every field is in a monoculture situation with one seeded crop. Twenty years ago, peas and canola were being grown together and manufactured as the “peola chip” at a small factory in Kelvington, Saskatchewan. “Intercropping has been used probably for hundreds of years,” says Chalmers. “Lately, one or two farmers in Saskatchewan are actually using this concept with peas and canola, and have been talking about how well it’s been working for them. WADO wanted to put it to the test and see if there’s anything going on.
As well, Dr. Rene Van Acker and Tony Szumigalski, while working as researchers at the University of Manitoba in the mid-2000s, found the cropping tactic to be a promising one. Although Van Acker has since moved to the University of Guelph and Szumigalski is now with Manitoba Agriculture, Food and Rural Initiatives, their work on increasing efficiency in the use of soil, water and sunlight was published
A “last minute” WADO trial in 2009 found large yield benefits when peas and canola were planted together. For 2010, it was time to be more formal in looking at the benefits and barriers, Chalmers says. However, it also turned out that growing conditions were tough at Melita. “We weren’t too happy with the variability levels this year,” Chalmers says. “I think that came from our flooding damage. The plots looked good, but down in the root zones there was likely something going on that we couldn’t see. We’re going to run these trials next year and maybe go to a few more locations.”
The 2009 test was simple, using two bags of seed from the WADO storage shed. Some 71-45 Clearfield Canola was mixed with Striker field peas. Striker is a medium-tall, semi-leafless pea that produces large seed. The 71-45 Clearfield is an early-maturing canola. At harvest, the peas were past-ready before the desiccated canola was mature.
“We weren’t really expecting much,” Chalmers says. “The trial looked good in summer and it looked really good when we went out to combine. It harvested really well. We split up the crops with a cleaner, and they separated nicely. We ended up with some really nice clean canola that was black, large, and likely had quite a heavy seed weight. The peas looked very nice, too. They were relatively low in damage or splits, despite our cylinder speed being around 800 rpm.”
They straight-cut the mixed crop close to the ground to capture maximum pea yield. With that, they increased the harvest of canola stems. “The amount of material was phenomenal,” Chalmers says. “We had to go a little slower with the combine, and we had to deal with more biomass. There was probably five to 10 percent trash (canola pods) or dockage to deal with.”
The positive side was that the canola buffered the peas. Despite the increased threshing speed, about 200 rpm above normal, the peas came through with very few splits. Swathing probably is not a good idea. Allowing a heavy swath to dry down for a week or more without being anchored in stubble, they advised, would have posed a serious risk from wind-related damage.
WADO dumped all the seed down the same run in 2009. In 2010, they kept the seed separate in individual rows and had four treatments at their Melita testing site. They used Clearfield 41-45 canola and Golden peas. The treatments were replicated three times. A second site, at Hamiota, demonstrated many of the same options. “Our treatments last year were looking at competition versus yield, and we didn’t really catch much competition. This year we modified the system to look more closely at fertility, efficiency, row orientation and disease,” Chalmers says.
Each plot was about 20 metres square. There were check plots of canola with 80 pounds of nitrogen, canola with 45 pounds of nitrogen and inoculated peas without nitrogen.
For the first treatment, workers alternated double rows of canola and peas. In these, only the canola was fertilized. Alternating single rows of canola and peas were in the second treatment. Peas and canola were mixed in the third and fourth treatments. One treatment received a full rate of nitrogen; the other received a half-rate. “We’re trying to see if peas become lazy when they have nitrogen available,” Chalmers says. “We also want to see if we can push the intercrop system a little harder, still gaining that light-use efficiency, but trying to make those peas work a little harder for their fertilizer.”
Results in 2010
With a caution that these are only first-year results, and from a season that saw drowned and reseeded fields, Chalmers says: “The numbers aren’t too solid yet, but the data suggests that the peas in the mixed system were doing a little better than in the single rows or double rows. It also looked like the double rows did better than the single rows. We’re trying to use that nitrogen for canola a little more efficiently. We used the half-rate to see if there would be a response, to see if peas gobble up that nitrogen rather than fixing their own, stealing it from the canola.”
Shattering pods and lost seed actually decreased in the intercropped plots. Monocrop canola, harvested with a straight cutter, had a shatter rate of eight to 10 percent. Intercropped canola shatter losses were about three percent.
Canola yield in the plots was a big surprise. They expected some yield reduction due to competition from the peas. The first experience, in 2009, saw canola yields reduced by a quarter due to the competition. “This year, we found the canola yield was the same in the intercrop as in the monocrop, statistically,” Chalmers says. “This year, competition didn’t seem to bother the canola but the peas took the entire hit. They were down to about 50 or 30 percent of their normal yield. Basically, we got our normal canola crop and on top of that, about 1500 pounds of feed peas.”
Weed control was handled easily in the system, but was not evaluated. The plots of Clearfield canola and peas were sprayed with Odyssey herbicide for weed control. They also had an option to use Select for grassy weed control, but did not need it. With the amount of material growing in the intercropping system, he says, most weed seedlings are choked out.
Disease declined in the intercrop setting, as well, probably due to the different growing conditions. “We noticed a huge difference in the Mycospharrella disease damage on peas. When peas are in monocrop we see quite a significant increase in disease in comparison to when they were intercropped. “It looked like the peas fell down in the monocrop situation. Then with one rain after another in early fall, the pea pods picked up disease and transferred it to the seed. In the intercropping situation, canola helped keep the peas off the ground and, I’d assume, buffered a lot of the rain drops from hitting the ground and splashing up on to the leaves.”
Separating and storing the two crops also requires advance planning. Plan to clean and separate the two as soon as they arrive off the combine. “You could have a spoiled bin pretty quickly. If they go into storage together, the peas will contribute moisture to the canola, then the canola will start to heat in the bin.”
Intercropping also appears to have a positive impact for crop rotation, Chalmers says. “If you typically grow wheat, peas, canola, barley, I guess it would shorten up your rotation. If you grow wheat-canola-wheat-canola, having the peas involved might help the system and diversify the rotation,” he says.