This simplicity also means that each individual plant in the field not only requires the same resources, but has the same properties. A monoculture is therefore like a cloned football team made entirely of strikers; they all stand in one half and score goals but none of them really make any attempt at defending. This means that monocultures only work when the resources and conditions for the culture are optimally prepared via external input, and pests are controlled – namely when they are looked after and “defended”. This makes chemical and biological fertilisers and pesticides indispensable for monocultures.
A combination of complementary strengths
I think that polycultures could provide a remedy here. In Switzerland, mixed grasslands are already widespread, as are barley-pea mixes for feed crops and winter wheat mixes as bread grain.
The benefits of polycultures lie in the complementarity of their components. For example, barley provides a prop for the otherwise low-lying peas, which simplifies mechanical harvesting, while the peas provide the barley with fixed nitrogen from the air. With wheat mixes, species with various kinds of disease resistance can be combined, which enables a high and stable good-quality yield using significantly fewer pesticides. In short, plant teams are also highly attractive from an ecological point of view.
Targeted breeding for polycultures
To utilise this potential, I believe that the agricultural sector needs to rethink its approach. Together with a colleague from the University of Zurich, I was able to prove that the yield-increasing positive interactions between plant species can only fully develop when the plants are cultivated over generations in polycultures
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. That means that targeted breeding programmes are required for mixed crop plant cultures.
As our survey of farmers as part of the EU project DIVERSify
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showed, there are also many other barriers to widespread mixture cropping. Above all, these relate to a lack of knowledge about how we can adapt our methods designed for monocultures to polycultures – whether in terms of planting, crop protection, harvesting, subsequent processing or marketing.
There is a real need for action here, but I am convinced that it will be worthwhile. The effects of biodiversity do not stop at the gates of farms, any more than the monocultural risks do. So let’s use diversity to make agricultural production sustainable without losing productivity!
