Intercropping has been demonstrated to benefit producers by reducing the need for chemical pesticides through exhibiting biological control of weed pressure, disease incidence, and grain quality and by mitigating crop failure risks through adding diversity to a system. Intercrops have also been demonstrated to out-yield monocrop systems grown on the same area of land, increasing potential economic returns for producers. Intercropping systems have the potential to increase residual soil nitrogen if a legume is used in the system, therefore reducing a producer’s reliance on synthetic nitrogen application and decreasing environmental harm caused by synthetic fertilizers. The success of various pea intercrop systems was evaluated over three consecutive years by establishing two intercrop trials in Manitoba: a multi-crop trial to evaluate the agronomic and economic success of either flax, oat, wheat, mustard and canola intercropped with peas at three trial sites; and a pea-Brassica intercrop trial which aimed to understand the seeding rate dynamics of intercropping peas with Brassica family crops and to examine the potential effects of intercropping on Aphanomyces root rot incidence, weed pressure, grain yield, and pea grain quality.

The multi-crop trial was established near Melita, Reston, and Roblin, Manitoba from 2019-2021. Yield, weed biomass, and disease incidence data was collected over three growing seasons at each trial location and data was combined prior to analysis for each site. Three-year average total land equivalence ratio (TLER) of all intercrop combinations except the pea-flax intercrop was above 1, indicating consistent out-yielding from each of these intercrop combinations at all sites. TLER of pea-oat and pea-canola intercrops was significantly greater than that of the pea monocrop at both the Reston and Roblin sites, while TLER of pea-wheat and pea-mustard intercrops was significantly greater than that of the pea monocrop only at the Roblin site. While no significant net revenue differences were observed among intercrop treatments at the Melita site, net revenue of pea-oat, pea-canola, and pea-mustard intercrops was significantly greater than that of the pea monocrop at the Reston and Roblin sites. No weed pressure, pea grain quality, or disease pressure differences were observed between pea monocrops and intercrops in the multi-crop trial over three years.

In the pea-Brassica intercrop trial, pea-mustard and pea-canola intercrops seeded at various densities were established near Reston, Manitoba in 2019 and 2020, with pea-camelina intercrops replacing pea-canola intercrops in 2021. Weed biomass was lesser in pea-mustard intercrops with high mustard density than in the pea monocrop, highlighting a potential weed suppression effect of mustard at these densities. Pea-mustard intercrops demonstrated consistent out-yielding as TLERs were greater than 1 for all pea-mustard intercrop treatments. No significant LER, yield, or pea grain quality differences were observed between pea-canola intercrops and pea monocrops. PCR quantification of Aphanomyces euteiches DNA copies present in pea roots revealed that pea-canola intercrops grown at 70% normal pea density and 30% normal canola density had significantly (p = 0.081) less A. euteiches DNA present in root samples than the pea monocrop, highlighting a potential disease control effect of intercropping pea with canola at these densities. All pea-camelina intercrop treatments had greater average TLERs than the pea monocrop, and pea yields in pea-camelina intercrop treatments with peas seeded at 70% and 50% the normal seeding rate were not significantly lower than that of the pea monocrop.

Results from these intercrop trials highlight the ability of pea intercrops to out-yield pea monocrops and potentially provide an economic advantage to producers. The pea-Brassica trial also highlighted the potential weed and disease suppression benefits of intercropping peas with Brassica crops. These results expand on existing intercrop research and contribute to providing pea producers with insight into the revenue potential of various pea intercrop systems in Manitoba.