Written by Matt DiLeo
The September issue of CSA news has a nice (open access) article entitled: “Do polycultures have a role in modern agriculture?”
Some key caveats:
* While diverse plant mixtures have been associated with many benefits, high biomass yield (i.e. what farmers get paid for) is usually not one of them.
* It’s very difficult to maintain complex plant mixtures – usually a single species will come to dominate.
* Our crop monocultures represent those crops that are best adapted to a given region.
* Establishing, maintaing and harvesting polycultures will require significant effort, risk, investments and training for farmers.
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They conclude that polycultures are intriguing but definitely require more (agronomically realistic) research.
Thoughts?
Written by Guest Expert
Matt DiLeo has a PhD in Plant Pathology from UC, Davis. During his postdoctoral research at Boyce Thompson Institute, he researched unintentional effects of genetic engineering. Matt builds R&D teams and biotech platforms: genome editing, gene discovery, microbials, and controlled environment agriculture.
I think polycultures, both annual and perennial, have huge potential. Instead of knocking down other people’s research plots, why doesn’t Greenpeace spend some money on this?
This is a nice article.
I plant diverse pastures of about 8 species, in contrast to the typical recommendations of one grass and perhaps one legume.
This work explains the reasons for doing so very well. If you have a lot of fertility and know what will grow best in your location then you can get away with simple pastures. But if you have soil heterogeneity and are not going to throw on abundant, cheap fertilizer, than it really makes a lot of sense to diversify.
Some things I noticed this year, for example.
I planted four clover species and each one had a different peak of productivity, which really evened out productivity.
As the cool season grasses faded in some fields, the warm season forbes (chicory and plantain) took over.
Fields with heavier soils retained grass dominance over the forbes.
Annual clovers really grew well the first year, but biennial and perennial clovers take over in subsequent years. By having the annuals in the mix, we got the benefit of clovers growth in year one.
I do think this is a very important line of work and it is nice to see uptake within the university system. I haven’t been able to find any extension agronomist or forage seed salesperson that can give me much to go on as far as research goes. But I am well versed in biodiversity and ecosystem function research to apply it and it seems to pan out.
Resilience, environmental heterogeneity in space and time, and uncertainty, are real factors to appreciate and polycultures make a lot of sense when valuing those.
Plantain?
My chickens prefer ANYTHING else; I was assuming that the available nutrition was low (low content or excessive antinutrients).
I am using a variety bred for forage. Haven’t paid much attention to what the chickens think of specifically it but the sheep eat it up.
My observations suggest chickens tend to prefer, in this order: clovers, forbes, grasses.
Cichorieae: dandelions, hawkweeds, lettuce and associates: THAT’S what chickens like. I can verify that Crepis, Cichorium, Krigia, Lapsana, Hypochaeris, and Taraxacum are avidly taken.
How does intercropping differ? If the plants have different habits or lifecycles (peas and corn, corn, beans and pumpkins, amaranth and potatoes), does it count?
I think that counts. Doing work by hand makes this rather easy to accomplish. It is getting to field scale where difficulties arise, and going beyond vegetables that can work economically using had labor.
Still, I am aware of the use of polyculture intercropping in other countries and may adopt them here for seed crops that are mechanically harvested. For example, plant alternating rows of clover and grass seed. Use it as a simple pasture for part of the year but let it bolt and go to seed in spring/early summer. The key is to pick species with differing growth habits and phenologies (as you discuss) so that the job of seed cleaning is made easier. We can, for example, sow a tall growing grass with a low growing clover, or vice versa.
Point taken. With potatoes and amaranth, mechanical harvesting is trivial, but menial labour is essential for the others. (Except maybe peas, which can be mechanically harvested before the corn gets tall).
If polyculture worked well, farmers would instantly adopt the method without any prompting whatsoever. It would sweep North America as swiftly as GM crops. In fact, it would already have swept North America quite a few years ago.
Even so, Jason is doing the right thing with pasturage. Where I live, pastures are areas which are unsuitable for crops, for any number of reasons. They’re on marginal land. If you don’t polyculture, allowing grasses and forbs to flourish in the many ecological niches which are more common in pastures than in cropland, you’re foregoing quite a few benefits. Plants may not be smart, but they’re very good at winding up in places where they thrive.
Interestingly, in this neck of the woods, none of the farmers plant grass seeds in pastures. Agricultural animals are simply turned loose in the pasture, and things which flourish in the face of herbivore predation naturally prevail, to the benefit of everyone.
I take it you haven’t checked out the new movie Moneyball.