Sometimes it’s funny how things turn out. I have not been a fan of the ‘garden polyculture’ strand within permaculture. I think that it’s ok on a small scale, or where there is a lot of free labour available for harvesting, but it has never struck me as a way to grow significant quantities of calories. Strangely I seem to be coming back to the idea. It all started with confirmation of the yield increase from a grain legume combination. Not really a true polyculture, more of an intercrop, but the basis of my small scale grain growing experiments. Things have moved on a bit since then. Please note that I’m not going to be giving details of all of the plants that I am using in my experiment, or references for the information that has got me to this point. I want to be sure that it works, before publishing the results. There will however be plenty of links to help you think about your own polycultures, or cover crop cocktails.
Multi -Species Cover Crops
Much of the research that I’ve been doing this winter has been to do with multi-species cover crops, or cover crop cocktails. It started with this video clip, called ‘under cover farmers’ cover crop cocktails. Really interesting, and there seems to be a lot of potential in their use within large scale agriculture. However three bits of information really struck home during my search. First was the realisation that many of the cover crops were food crops in their own right. Secondly, much of the soil building benefits of the cover crops were due to the root exudations, from actively growing plants. This suggests that growing these crops to harvest was likely to be as good for the soil as early incorporation/crimping. Finally there was the overlap between cover crops, food crops, and plants good at accessing phosphorus from the mineral fraction of the soil.
All in all there seems to be good reason to try and integrate the functions of food production and cover crop in a single mixture. In other words, a polyculture. However the harvesting issues still remain, so I’m planning to gow these crops in double rows, mixing cold season grass, cold season broadleaf, warm season grass, and warm season broadleaf as row crops.
A Grain Based Polyculture
Most of the world’s population eats grain, and although some root crops may produce more calories per acre, I suspect that we’re going to be eating grains for some time to come. So a polyculture with a high grain component makes a lot of sense. Luckily the advice given for growing cover crop cocktails is to use both cool and warm season grasses. Most grains grown are grasses, and so including grains in a productive polyculture makes a lot of sense. If you look at this cover crop chart, you can see some of the plants that are being recommended. There are plenty of grains listed in thischart too MCCP_Chart_2 cover crops .
A Phosphorous Scavenging Polyculture
This post is not the right place to discuss phosphorous availability in depth, but my reading has turned up a number of plants that are able to access or dissolve phosphorous that would not be available to other plants. What was surprising was how many of them were also food crops, or cover crops, or nitrogen fixers, or even all three. For example, one plant that was mentioned was white lupin. A common green manure or cover crop component, and one that I’m growing an edible version of.
Including it in a productive polyculture, I will get food, nitrogen fixation, a deep rooted plant to help with decompaction, make more phosphorous available, and a bee plant. This is only one example of many.
An all year round Polyculture
By carefully choosing plants, it should be possible to keep the soil covered, and have an actively growing plant in the soil at all times, all at the same time as producing food, and building soil. This is probably going to be the most difficult part of my experiment. I think that I’ve worked it all out, but it will take a season or two to iron out any glitches, and then perhaps another season or two before I test to see how my soil has been affected by the polyculture experiment.
I intend to keep drip feeding information, pictures, and blog posts as |I go along.