Nature is intelligent. In nature, plants have evolved and coevolved without any human assistance. Through the soil, microbes, insects, animals, and climate, these plants developed relationships with their environment, creating an efficient system of survival. The soils develop signals from the ecosystem we refer to as soil, triggering different plants to grow and thrive.

One of the keys of intercropping is the use of synergetic plants, meaning plants that play nice with each other.

Most native stands that are properly managed will consist of each of the functional plant groups, but each have their own ecological advantage, so they will grow in specific areas or conditions.

Legumes are dominant in a stand early in the soil developmental stages. They provide nitrogen to the system and once the nitrogen cycle has started, natural soil-borne nitrogen fixers are established, and mycorrhizae fungi are established legumes that move to background levels. When the natural nitrogen cycle falters, legumes jump back into the plant mix to get nitrogen produced for the ecosystem. Once the system is back to “normal” the legumes then slip back to background levels.

Brassicas like to grow in disturbed areas with high levels of free nutrients, normally in a soil that is bacteria-dominated. As a rule, they are competitors in the system, tying up nutrients. They require a plant that will feed them, such as a legume. Grasses and forbs in a system dominated by brassicas will struggle to get nutrients. Brassicas have an acidic root system so rely less on mycorrhizal fungi.

Non-brassica species are a very diverse group, and this includes plants like beets, sunflowers, flax, and buckwheat. Many of the plants in the non-brassica group are mycorrhizal fungi-friendly so tend to play nice in mixes. Most crop rotations are missing adding some of these crops into their rotation or blends.

There are some inherent issues with some of the species. Sunflowers and flax can be later maturing, and buckwheat is very early maturing. Research is now showing that some of these non-Brassica plants are able to control the available boron for some plants, so their maturity is sped up or slowed down to match maturities of other species in the mix.

When looking at synergies by growing more than one functional plant group, one needs to understand what each group does. When growing blends, observe what plants are thriving — this is how our soils and microbes talk to us. If the legumes are very strong it is an indication that the nitrogen supply in the soil is low. As the nitrogen level increases, the legumes lose their ecological advantage. Conversely, if grasses are producing poorly, it may be due to low nitrogen so adding more legumes might correct it.

Plant Mix Design

When designing a plant mix, goals are very important, as is knowing where your soils are health-wise. For intercropping with a goal of low or no synthetic inputs, an easy button is to grow a grass with a legume like oats and peas. To take it to the next level, flax and Phacelia can be added. All species are mycorrhizal fungi-friendly, and oat, flax and Phacelia are all relatively low nitrogen users.

Adding a Brassica to a mix would require a higher nitrogen supply rate. Remember, Brassicas are nutrient scavengers so will compete with your grasses, non-Brassicas and forbs. Pea-ola, peas and canola, has been grown in Western Canada for 40 years and is an easy way to grow canola without a large fertilizer invoice. Recent work by Lana Shaw with flax and chickpeas has shown some great promise.

Seed size is the other key, unless the plan is to feed the mixture. For selling individual species from the mix, they need to be able to be separated. The least expensive way to separate is by seed size, but separation can also be done by seed weight density. Before doing any mixes, grain buyers should be contacted to see what their pain tolerance is of grain contamination with other crop types or dockage.

More producers are using a stripper header which allows taller species to be used, like Persian clover. Flax is another crop where adding lower growing species helps with suppressing weeds and a legume will help supply more nitrogen. Adding a winter cereal along with subterranean clover creates ground cover in the flax.

Care needs to be taken with fall rye if using other cereal cash crops. It can overwinter, creating grain contamination, plus it produces allelopathy, chemicals which will prevent other plants from growing if it gets established before the other plants.

When we are looking at mixing plants together, we need to think of how and where they occur in nature. In most cases it is a legume and a grass that thrive. Adding a forb or non-Brassica broadleaf helps with adding diversity both aboveground and within root systems.

Having a grass species that stays in the vegetative stage helps to leak root exudates all season long. Brassicas are nutrient scavengers, so care needs to be taken when including them in a blend as they will continue to accumulate nutrients competing with the other species.

Then, care must be taken in keeping the plant densities in the right ratios that match what the soil can supply in terms of nutrients and water. Remember to work with nature’s intelligence.

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