Polycultures v Monocultures — The Great GROW Experiment 2018

GROW Observatory
Mar 23, 2018 · 5 min read
Polycultures in my garden: Peas and mixed lettuce

by Dr Naomi van der Velden, Permaculture Association of Britain

Imagine if those of us who grow at a smaller scale could join together to share our knowledge and investigate practices. Well, through citizen science, we can!

Here Dr. Naomi van der Velden tells us about mixing crop plants together in a single space — polycultures — and about the related GROW Experiment 2018, which you can join.

I like to grow food by mixing my crop plants together into complementary groupings that make good use of space and help each crop species grow well. In contrast to monocultures where a single crop is grown, polycultures of two or more crops grown together can have many benefits. Scientific studies have shown that growing in polycultures can:

  • Mean crops are less susceptible to pest and diseases
  • Give greater productivity and economic profitability
  • Enhance ecosystems, biodiversity, nutrient cycling, soil and water conservation and carbon sequestration.

There is good logic behind this too:

  • A mix of plants means you don’t offer pests a “feast” of a favourite food or host plant.
  • Polycultures can allow more efficient use of space (by stacking crops vertically), of time (land can be productive for longer with several crops), and by giving a greater diversity of food so lessening impacts of failure of any one crop.
  • Greater plant diversity supports greater insect diversity and more diverse food webs; soils can be covered for longer; evaporation can be lower; plants with different nutrient requirements can complement nutrient use or, in the case of legumes, add nutrients to the soil.
Polycultures in my garden: Runner beans, squash and sunflowers (with volunteer poppy)

It all sounds good, but….

It all sounds good, but there are lots of “can do” and “might be” in there and not so many “will do” and “always”. Whether or not it is worth growing in polycultures will depend a lot on the crops you choose. Your climate, soils, how adept you are at recognising crop seedlings from weed seedlings, and many other factors can also influence success.

Another key aspect to consider is that much of the scientific research focuses on large farm-scales where the use of machinery, fertilisers, pesticides and more might be routine. Most studies we found have looked at two crops but few have looked at more than that. Two crop research is most often into “row intercropping” where alternate rows (or strips of several rows) of each crop are planted across a field. There is usually a “main” crop (e.g. a cereal like wheat) and a “second” crop (e.g. a legume like field beans) that is grown to enhance the conditions for that main crop rather than be a true harvest itself.

So, if the research is in such different conditions to how I grow, how do I know what will work for me?

Lots of people grow polycultures. Compared to a large farm field of a single crop, an allotment plot or kitchen garden is a polyculture! Many growers have experimented with companion planting or even tried mixing together lots of seeds and scattering them on a vegetable bed. There’s a lot of knowledge and experience out there. Imagine if those of us who grow at the smaller scale could join together to share our knowledge and investigate practices. Well, through citizen science, we can!

One of the aims of the GROW Observatory is to gain a better understanding of if, how, and where regenerative practices work at the smaller scale. Regenerative practices are those approaches that can help improve, or ‘regenerate’, soils and ecosystems while also growing food plants. Through conversations with people who have done courses with us, and through reviewing scientific literature and key information, we know that companion planting and growing polycultures is an area where there is a lot of interest but also a lot of conflicting information and uncertainty.

Join in! The great GROW experiment 2018 — Polycultures vs Monocultures

We want to address this with an experiment in which you can take part — an experiment that will compare three crops (green beans, spinach and radish) grown together in a polyculture with those same three crops grown separately as monocultures. Join us and find answers for your own growing space, while contributing to building up a wider understanding of this key practice at the scales of our growing.

There are two ways to join in:

  • Join the free GROW Citizen Science: Living Soils, Growing Food online course to learn more about regenerative practices and how to experiment in, and better understand, your own growing space. Some of the first measurements needed for the experiment will also be introduced on this course, so you can get a head start (first link below).
  • Join the GROW Polyculture v. Monoculture Experiment directly. We’ll give you all the information you need to discover which, if either, works better for you, and to compare your results with those of other participants (second link below).

Whichever way you join, we’ll give you on-going support over summer 2018 and help you to understand and use your results. All experimenters in Europe will be eligible to receive free kits for testing soil nitrogen (N), phosphorus (P), Potassium (K) and pH.

Citizen Science: Living Soils, Growing Food starts 16th April 2018 — click below to join.

Find out more and register for the experiment. It opens on the 1st May 2018 and you can get planting any time from then until about the end of June (depending on the growing season in your location).

I look forward to learning and growing with you!

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