Why mix and match?

Multi-species mixtures have become a popular approach to “cover cropping”. The question arises: What is the benefit in this approach?

According to research by Penn State University, planting a multi-species crop, as opposed to a mono-culture, provides multifunctionality. If you only have one plant, you only get one benefit. Combining species enables you to tick multiple boxes.
Multiple species improve the soil’s biological activities as they feed beneficial organisms.
Difference in plant size, type and growing behavior encourages better growth. The greatest competitor for a plant is another of the same plant – as they compete for the same space, nutrients, sunlight and moisture. With a mix of species – with plants vary in their requirements. These plants may grow at varying heights – absorbing sunlight at different levels. Their root systems may reach different depths – gathering water and nutrients. Further to this, different plant types may be able to benefit each other – for instance, some plants fix Nitrogen which is beneficial to a neighboring plant.
The majority of studies performed view plants in a monocrop scenario - and insights are drawn on the way they behave in isolation. However, when you view plants in mixes you see that they behave in a totally different manner.

On the other side of the coin, planting a mix requires some careful consideration and planning.

Certain species may not be complementary. Where plants compete for the same resources there is always a winner and a loser. Consider both the plant type and seed count in your planning.
Seeding multiple species (especially when faced with varying seed size) may result only one species being planted optimally. Here consider the machinery available to you, or a mix that includes similar seed sizes.

Andre McGuire, of the US Centre of Agriculture & Sustainable Resources, cautions that polycultures “aren’t the silver bullet”. When considering a cover crop, both monocrops and polycrops should be considered – each has its place, and this depends on your objectives.