Intercropping is an ancient farming practice. Farmers in Meso-america thousands of years ago started growing “the three sisters” — corn, beans and squash — together in the same fields, letting the symbiotic nature of their biologies provide an overall better result than growing them separately. Strong cornstalks provided a “pole” for the climbing beans. Beans fixed nitrogen. Squash provided ground cover to reduce weed competition. All three were important parts of the diet. The practice eventually spread about as far as the climate would allow.
These days, intercrops are common in tame pastures, with grasses and legumes grown together, and lately we’ve seen increased interest in intercropping of annual crops. For this article, arranged in a question-and-answer style, we talk to two Canadian farmers with experience in growing canola and peas together.
- Read more: Two research projects looking at intercrops
Colin Rosengren started growing intercrops in 2004 on his farm at Midale, in the dark brown soil zone of southeast Saskatchewan. Intercrops now account for about two-thirds of his acres each year. “Back in 2004, economics were getting tough. Canola and pea prices were terrible and fertilizer prices were high. I didn’t like spending money on products that didn’t provide an incremental gain,” Rosengren says. So he tried intercropping as a test to see if it could reduce costs and increase returns by working on a notion that one plus one might equal three.
The idea was driven by observations on his farm. “Single volunteer plants growing in another crop were always exceptional,” Rosengren says, noting their size and vigour. And while checking cows over the years, Rosengren often noticed how native and tame pasture would tend to find a balance with a mix of plants. “Intercropping is not a new idea,” he says, but in 2004 he was one of the few farmers in Western Canada who had revived this old practice. After 15 years, Rosengren has built his farming system around intercrops.
Jennifer and Michael Doelman farm in the Ottawa River Valley at Renfrew, Ont., and have been growing a pea-canola or “pea-ola” intercrop for two years. Jennifer describes their area as the “Western Canada” of Ontario, with a shorter, drier growing season than southwestern Ontario. The area produces a lot of forage, dairy and beef, so local demand for feed grains is high. The Doelmans continue a minimum tillage approach that Jennifer’s father adopted at a time “when soil structure was really failing,” she says. They are also beekeepers, so know the value of canola and overall plant diversity for bees and honey. “We’re not intercropping experts in any way,” Jennifer says, but she’s an agronomist and adds: “I’m a total geek and I like the idea of not having total monoculture.”
Here are the questions and their answers.
1. Why grow pea-ola?
Colin Rosengren: The main reason is higher net return. Pulses and the microbes they stimulate can accelerate the cycling of nutrients and increase productive capacity in the soil, and the benefit this provides to other crops like canola can be that much greater when the two crops are growing at the same time. I grow peas and lentils along with canola or mustard in a three-way intercrop. I generally use older open-pollinated canola varieties when intercropping, although this year I will look at some of the newer varieties with higher yield potential. I will swap in other brassica crops like mustard as a replacement for canola based on the markets and my sense of the year. In a drier year, I bias more to higher value and lower productivity, and if I feel it will be wetter, I will sway more toward higher yield options to take advantage of the water.
Jennifer and Michael Doelman: We have been growing 4010-type forage peas, but you lose your religion trying to harvest them because they fall over so easily. The main hook for pea-ola was to use canola to improve the standability of the peas. For canola, we use InVigor 233P for straight cutting and yield potential, but we obviously can’t use the Liberty herbicide. If we had familiarity with Clearfield, we might try that.
2. How did you seed the intercrop?
Doelmans: We use a John Deere 1890 air drill with 1910 tank on 7.5-inch row spacing. Canola seed goes in the starter fertilizer tank and peas in the other, and they both go into the same seed row. We have had a hard time getting the canola seed rate as low as we’d like it. In 2019, we seeded canola at 3.75 lb./ac., but would like to be at 3.0. We might try adding monoammonium phosphate with canola in the same tank to improve metering and provide the fertilizer in the seed row.
Ideally, you would put them in the same row but with canola shallow and peas deeper, but I put peas and canola together at one inch deep. I tried alternating rows but that didn’t really work, even at 10-inch spacing. The peas fall over, then grow up the canola. You want the peas to grow up with the canola plants so the peas stand up, but when they grow sideways first, it leaves wide gaps of 20 inches and the podding starts closer to the ground. I use CropPro SWAT maps to set variable-rate seeding prescriptions. Canola seeding rate is basically the same across the board, which would be about a two-thirds rate, although I will go with higher seeding rates in saline areas because canola grows better there than anything else. Pea rates go from 30 lbs./ac. on hilltops to 150 lbs./ac. in low areas. Lentil rates are 45 lbs./ac. on hills and five lbs./ac. in low areas.
3. How do yield and profitability of the intercrop compare to growing the crops separately, all things considered?
Rosengren: Average total yield is about one-third higher than you’d get with a monocrop on the same land. This is based on trials I used to run comparing intercrop to monocrop strips in the same fields. I haven’t run comparison trials in a while, but I think variable-rate seeding has probably pushed the yield gain higher. On the other hand, monocrop canola yields have also increased since I ran my trials, which is why we’ll try new varieties in 2020.
Doelmans: Canola allows the peas to stand up, which is the big advantage for the intercrop. Peas lie flat if alone, which slows down harvest and increases the amount of stones put through the combine (and downtime to fix anything that gets broken). The intercrop also avoids the family strife that comes from harvesting a flat pea crop. As for economics, the intercrop improves the profitability of our winter wheat, which follows the intercrop and is our most profitable crop. The pea-ola crop also makes our corn and soybeans more profitable. We’ve had droughts for the past two years, so canola actually helps because of its deep taproots. In 2018, our first year with the intercrop, we had pea yields of 0.5 tonnes per acre and canola yields of 0.35 tonnes per acre. We made money but it wasn’t worth the extra effort. In 2019, we cut back the canola seeding rate and had 0.91 tonnes of peas and 0.18 tonnes of canola per acre. This is the better situation. Canola is the loss leader, but it makes the peas way more profitable. If you tried to make both profitable, neither might be profitable.
4. Does the fertilizer make peas lazy? Do you get the N fixation you might expect?
Doelmans: We struggle with this. In 2018, we applied more nitrogen and got better canola yields. In 2019, we cut back and applied 29-0-0-14 — a combination of ammonium sulphate and urea — to get the crop going. If things are slow out of the gate, they’re always slow. Our clay soils have 3.5 to four per cent organic matter (OM) and fairly high cation exchange capacity, so we usually get 30 lbs./ac. more mineralized nitrogen than the rest of Ontario.
Rosengren: That may be true for peas grown in fields with higher residual nitrogen fertility. For my area, peas in a monocrop often benefit from 20 to 30 lbs./ac. of nitrogen fertilizer, otherwise they go yellow from nitrogen deficiency early in the season before nodulation kicks in. For the intercrop, I like to have 40 to 50 lbs./ac. of nitrogen available to the crop. This keeps everything green until peas start producing nitrogen. This will change for other areas. We’ve heard of farmers in low-OM soils finding their crop short of nutrients and likely need to put on more fertility. Basically your soil is the engine and intercropping pushes the throttle higher. If the engine is large, you will feel the difference. If you’ve got a lawnmower engine, you won’t pull much no matter how hard you push the throttle.
5. What pest management issues were made better or worse with the intercrop?
Rosengren: I use Edge herbicide and will use Group 2 post-emergence if I have to. The weed situation is hard to compare to a monocrop of herbicide-tolerant canola, which would be very clean. Architecture of the intercrop helps with disease management. We’re not in a high disease area, but upright peas will have less disease and with peas growing with the canola, the pea plants capture some of the falling petals that might otherwise cause sclerotinia infection in canola.
Doelmans: The best weed control is a good thick crop. We use pre-seed and post-harvest glyphosate burnoff, and because we’re seed producers and in a droughty area, our fields are clean. We seed winter wheat right afterward to keep up the weed competition, and we follow a rotation with three years between canola crops. We don’t really see insect issues and haven’t seen clubroot yet, but it is in Ontario. We used Priaxor fungicide on the pea-ola in 2019. (“It probably didn’t need it, but I slept better knowing the crop was protected,” Jennifer says.)
6. How do you harvest the crop?
Doelmans: We have a heavy cereal rotation, so the intercrop is ready when we get to it. We tried swathing the first year but saw no benefit at all. The intercrop is far easier to straight cut. In fact, the crop is a dream to combine compared to peas alone. We have a MF9790 rotary combine and for the intercrop use the soybeans settings but with a fan speed suitable for canola. Both crops are easy to thresh, but you need to be willing to look behind once in a while.
Rosengren: Logistical challenges are like puzzles and a hobby for me, and with intercrop, harvest and cleaning have been fun challenges. Harvest is generally easier since the pulses are standing up. Peas and canola are both easy to thresh. We open the sieves a bit to move more air through without having to increase the fan speed. In a monocrop, small-seeded crops like canola have to get sifted out of the chaff. Peas actually help because they shake out a lot better and take the small seeds with them. As for staging, we choose varieties that mature at the same time. We’ve been using maple peas, which have maturity about a week longer than other peas, and shorter-season canola so the harvest timing matches up. In our experience, some yellow peas would pop as soon as the sun shines on them. And with green peas, you have the increased risk of colour loss if you have to leave them out too long. Harvest is the easier part. Logistics of cleaning is what holds most people back, in my opinion.
7. How do you separate the harvested grain?
Rosengren: A rotary drum cleaner is gentle and fast. The challenge is that you need three augers all working at the same time, one to load the cleaner and two to handle the output. It can be a tangled mess. Because we’ve been doing this since 2004, we have set up a separating plant.
Doelmans: We separate the peas and canola with a dual-screen Farm King 480. We put canola onto the truck for delivery and peas go to the seed cleaner. Separation is fairly easy but time-consuming. Both crops were harvested dry in 2019, but if they’re tough, there’s no storing them together. They will separate somewhat in the bin and the air will travel the path of least resistance through the peas.
8. What do you do for crop insurance?
Doelmans: Dry peas aren’t even covered in Ontario, so we’re self-insured.
Rosengren: We don’t carry crop insurance.
9. What are the rotation challenges caused when you grow two rotation crops at the same time?
Rosengren: We grow about 12 crops every year, including cereals on their own and a corn-soybean intercrop, so rotation happens naturally to some degree. I do need to read up more about clubroot so I can make sure I’m managing for that disease.
Doelmans: We have a four-year rotation for canola and we work ahead on crop plans. Our 2021 crop plan is done and the year after is partly done.
10. Any benefits that you didn’t expect?
Doelmans: We didn’t expect the amount of conversation that the intercrop inspired. We have met interesting people and had good discussions. Neither peas nor canola are big crops in Ontario, so this has been a good way for us to shake things up a bit.
Rosengren: The soil health benefits are more than I expected, but I’m still trying to learn how to more accurately measure that.
11. Any challenges that you didn’t expect?
Rosengren: One thing I learned is to clean everything right away. If peas are tough and canola is dry, for example, I wouldn’t want to store it for long.
Doelmans: We have to be careful to double-check on residual herbicides. We kind of throttled back on where and how we use residual herbicides.
12. Would you do it again?
Doelmans: Absolutely. We have about 100 acres of pea-ola planned for 2020, with it going on some of our harder, more compacted ground. We’re throwing it out on our biggest problem fields.
Rosengren: I have been growing intercrops for 15 years; it is the way I farm.
13. What will you do differently?
Rosengren: I will try a few acres with a new Clearfield hybrid. I will also try a Roundup Ready canola and Roundup Ready soybeans intercrop, which is a new mix for us.
Doelmans: We’ll put MAP in the tank with canola to see if we can achieve a lower seeding rate. We would also like to find a Clearfield canola variety that works so we have an in-crop herbicide option, if needed.
Jay Whetter is communications manager with the Canola Council of Canada.