Luke Struckman, PhD, Oat-Pea Intercropping Project Lead, South East Research Farm
DURING THE PAST decade, mixed grain intercropping has become a commercially significant practice for some farm operations on the Canadian and Northern U.S. prairies. Proven mixed grain intercrop combinations can provide significant agronomic and financial
benefits. In 2020, the South East Research Farm and General Mills conducted a study to investigate the commercial viability of the oat- pea intercrop combination. The study combined farmer interviews with on-farm oat-pea trials in order to provide starting points for farmers interested in adopting oat-pea intercropping.
MIXED INTERCROPPING ON THE CANADIAN AND NORTHERN U.S. PRAIRIES
Intercropping practices, such as interseeding wide-row grain corn with cover crops or small grain-soybean relay cropping, are being used successfully in some regions of North America. Similarly, mixed intercropping has been relatively common on the Canadian and Northern U.S. prairies through small grain-clover or pea-brassica combinations. However, seeding two or three grain, oilseed and
pulse cash crops at the same time, harvesting them together at the end of the growing season, separating the seed and marketing each cash crop for grain, is a relatively new practice. This is referred to as mixed grain intercropping.
Farmers practicing mixed grain intercropping have reported significant agronomic benefits, such as reduced fungal and insect pressure, overyielding and increased post-harvest residue. Some proven mixed grain intercrop combinations include canola-pea and chickpea-flax.
The oat-pea intercrop combination is typically used for greenfeed or hay. It has not been common for the oat-pea combination to be grown for grain oat and dry pea production for human consumption. As the study findings demonstrate, the oat-pea mixed grain combination can be commercially viable thanks to the agronomic benefits it provides, in addition to the relatively strong market demand for both grain oats and dry peas in recent years.
To better understand current oat-pea intercropping practices, twenty-five interviews were conducted with farmers in Canada, the U.S. and the U.K. on their experiences growing oat-pea intercrops. Interview questions focused on production methods, grain separation, obstacles and profitability.
The vast majority of farmers stated that synthetic nitrogen applications can be reduced or eliminated in oat-pea intercrops. Fungicides were shown to not be necessary. Herbicide use was significantly reduced, but a number of growers mentioned that this was due to a lack of available in-season herbicide options.
Seeding rates were informed by the experiences of other farmers and on-farm experimentation. There were a wide range of seeding rates provided, but growers tended to favour peas and reduce oat seeding rates to 60% or less of monocrop. Otherwise, oats tend to dominate peas as the growing season progresses. Several growers have selected lodge-prone pea varieties to intercrop because varieties such as 4010 forage peas or Austrian winter peas can be incredibly difficult to grow as monocrops, and oats help to keep them standing until harvest.
Grain cleaning and separation are typically done on-farm using a wide range of cleaning equipment, although rotary cleaners tend to be the most common. Growers cite higher quality grain samples, lower grain shipping costs, as well as significantly lower dockage, as benefits to cleaning and separating oat-pea mixed grain on farm. Additionally, screenings can be kept or sold as livestock feed. Grain separation costs can be offset by higher quality grain samples in addition to reduced input costs.
Although oat-pea intercropping does provide attractive benefits, there are significant obstacles to making oat-pea intercropping practical for cash crop production. Crop insurance was cited as one major obstacle to oat-pea intercropping (and mixed intercropping in general), since most insurance policies only allow for a limited acreage of novel cash crops each season. Weed control can be a serious issue since no herbicides are labelled for use with both crops in-season.
On-farm storage can be another obstacle. Mixed intercrops must be stored separately from monocrops. Oat-pea mixed grain takes up significantly more storage space than other mixed grain intercrops (such as canola-pea) due to the bulkiness of grain oats. Along the same lines, separation is more difficult in comparison to other intercrops due to the large size of oat and pea seeds and the possibility of peas splitting during cleaning and separation.
Marketing can pose an additional barrier, since some grain oat buyers will not purchase oats that have had peas separated out of them due to potential allergen cross contamination. Finally, a lack of information — both from other farmers and published research on the oat-pea combination — can make it difficult to implement.
Despite significant obstacles, oat-pea intercrops have the potential be more profitable than monocrop oats. This is due to a reduction in synthetic inputs, lower grain shipping costs, higher quality grain samples and the possibility of growing higher- value, lodge-prone pea varieties. At the same time, oat-pea intercrops provide benefits to farm cash crop rotations and soil health, such as producing large amounts of biomass, increasing cash crop diversity and helping to mitigate adverse weather conditions through combining two different cash crops that thrive in varying soil moisture conditions.
Twelve on-farm oat-pea trial sites were located in Saskatchewan, Manitoba and North Dakota during the 2020 growing season (see Figure 1). The trials placed 10-acre oat-pea plots adjacent to 10-acre monocrop oat plots, allowing for side-by-side comparisons of oat-pea intercrop production with monocrop oat production at each site. Appreciable variation exists across soil types and precipitation levels in the broad geographic area covered by the trial sites.
Participating farmers chose seeding rates along with fertility and herbicide treatments. The non-replicated, single-year nature of these trials does not provide enough data to make agronomic recommendations for oat-pea intercropping. However, some key findings can provide starting points for farm operations interested in oat-pea intercropping for grain oat and dry pea production.
Participating farmers provided information on seeding rates, input rates and yield. Across the 12 sites, the oat-pea intercrop trials yielded 3561 lbs/ac, on average, while the oat monocrop trials yielded 3907 lbs/ac, on average. Importantly, increased seeding rates did not lead to a linear increase in yield across sites.
General Mills conducted grain quality tests comparing intercropped oats to monocrop oats. Oat samples were tested for percentage of oat plumps and protein content. While the oat-pea intercrop plots scored consistently higher with regards to percentage of oat plumps and oat protein content versus the oat monocrop trials, the differences were not significant.
A cost/benefit analysis demonstrated that the oat-pea intercrop was more profitable than the oat monocrop at Deloraine, MB, Boissevain, MB and Melfort, SK. There were no significant differences in profitability when comparing oat-pea intercrop plots to oat monocrop plots at Arborg, MB, Noonan, ND and Sheho, SK. At the six remaining trial sites, oat-pea intercrop plots were significantly less profitable than oat monocrop plots.
As this study demonstrates, the oat-pea combination can be a viable means for improving farm profitability, increasing cash crop diversity and building soil health. At the same time, appropriate seeding rates, the lack of in-season herbicides, post- harvest storage and separation, and marketing, along with other issues, need to be given serious consideration. Growers interested in adopting the oat-pea combination should consult with experienced intercropping farmers and experiment at small scales on-farm for at least one year before adopting oat-pea intercropping at a production scale.
This project was a team effort among researchers from the South East Research Farm, General Mills and Agriculture and Agri-Food Canada.