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The Power of Polyculture

Simon Johnson
Posts: 194
Location: S Ontario, Zone 6/7
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Here is my latest article from my blog all about the awesomeness of polyculture.


To start off, let's examine what a polyculture is not.

Currently the vast majority of our food is produced using monoculture techniques. That is, a large planting of only one type of plant, like a huge field of corn. This technique of food production has been optimized for maximum single crop yield and ease of mechanized harvest. This means one farmer is able to grow hundreds of acres of corn and harvest it all on his own with only the help of his heavy equipment and chemical inputs.

As it turns out, the farmer's dependency on equipment and chemicals is such that he would not be able to do anything without them. Without his heavy equipment the farmer wouldn't be able to plow his fields, sow his seeds, spray his chemicals, or harvest his crop. Without chemicals, the 'weeds' would take over his field, his crop would have no fertilizer to grow, and the insect 'pests' would eat any crop that did grow. Basically the farmer is fully dependent on these very expensive tools.

Year after year the farmer must continue to plow his fields, spray his poisons to kill the weeds, sow his seeds, spray his chemical fertilizer so his seeds will grow, spray his insect poison so his crops won't be damaged by 'pests', and harvest his crop, all the while driving some massive gas guzzling machine. If you go and add up all the energy that goes into producing each years crop, it will boggle your mind! Just thinking of the diesel fuel alone needed to run that tractor over those fields so many times each year is amazing. Now start throwing in the energy it takes to produce and ship all the chemicals year after year. How about the energy it takes to make a new tractor after the old one is broken?

These farmers are investing a very serious amount of energy and money into producing a single crop each year. The entire process is a constant battle against nature. Not one single part of the process is good for or works with nature! Not one.

Every year the soil quality goes down, thus requiring more chemical inputs to counter the effects. With a lower soil quality comes a decrease in the soils ability to hold water, making for a higher dependency on regular rainfall or irrigation. All the farmer can do is pray that this year won't be a drought year, because if it is, his crops will surely fail. If his crops fail, he will fail. Having invested the massive amount of money required to go about getting a crop this way, the farmer is in some serious trouble if nature decides not to cooperate.

Ok, so there are serious problems with growing crops in massive monocultures. Let's see if we can't address these problems with a polyculture approach. First, what is a polyculture?

A polyculture is a number of different plants, greater than one, planted and interacting together in an area. Even a planting consisting of only two types of plants can be considered a polyculture. Similarly, a grouping of 100 plants is also a polyculture.

So it would seem we need a scale to represent the level of polyculture we are talking about. Let's say then that a polyculture 2 garden has a measly diversity of only two types of plants growing and interacting with each other. Where a polyculture 50 garden is an awesome forest type garden consisting of 50 varieties of plants all interacting with each other.

Functional diversity breeds stability. This is the main thing when talking polycultures. The greater the number of varieties of useful plants you have working together in your system, the more stable the system will be. The system will be more drought, disease and pest resistant. In fact these problems will be nonexistent in the future with good design. It will also create it's own fertility and increase that fertility over time with good design. All the while producing a continual food harvest throughout the growing season for generations.

Well that sounds like a sweet deal! How does it all work?

Let's start off with one lonely row or lettuce in a tilled up garden bed of exposed soil. This single planting is extremely vulnerable here all on its own. Totally at the mercy of the elements and the local lettuce loving insects. One hot dry spell and the exposed soil drys up and the plants are dead. One group of lettuce chomping insects can move right on down the row and eat them all with no impedance. In order to plant that again next year, fertilizer will have to be added. All this adds up to a lot of work to keep that one row of food alive.

Now let's add a fragrant, flowering, insect attracting, deep rooted, shade casting, mulch producing plant like comfrey into the mix. We have a polyculture 2! Two plants interacting together. By simply adding this second plant, which was chosen for its functionality, we will greatly reduce the problems of above.

The comfrey will help shade the soil around the lettuce, reducing evaporation and need for water. The deep roots of the comfrey will bring up water and nutrients from deep in the sub soil and make them available near the surface, further reducing water need. The fragrant flowers will attract predatory insects which will eat other 'pest' insects as well as mask the smell of the tasty lettuce leaf, further reducing insect damage. The large leaves of the comfrey plant can also be chopped and dropped to cover the soil to reduce moisture evaporation and add fertility back to the soil. Holy smokes, all that from just adding one extra plant to the mix!

How about we try adding in a nitrogen fixing, ground covering, flowering plant, like white clover now? Polyculture 3! We are slowly moving up the scale to an awesome, self sustaining polyculture. But first let's see what adding the clover does.

By scattering clover seed and letting it grow up around our other two plants, we are creating a ground cover to protect the soil from the harsh evaporating power of the sun. The less bare soil exposed, the slower the evaporation of moisture from the soil, the longer plants can go without needing more water. The clover also has a relationship with bacteria on its roots which take nitrogen from the atmosphere and turn it into a usable form for surrounding plants to use. Thereby reducing the need for added fertilizer. Add on the insect attracting flowers and you have another excellent addition to the growing polyculture.

Simply by going from a monoculture to a polyculture 3 we have greatly reduced the work needed to keep that initial lettuce planting alive. While polyculture 3 is way way better than a monocrop, it is still far down the scale in terms of being a regenerative, abundance producing masterpiece of a polyculture 50-ish, that is an edible forest garden.

Let's jump to a polyculture 50-ish type system that has been maturing for a number of years and examine how awesome it is.

The first thing you would notice when observing one of these systems is the sheer density of plants. Monoculture uses just one spacial plane to plant on, where a forest garden polyculture uses multiple layers for maximum benefit. Here are the main seven layers that can be used:

Tall canopy tree layer
Lower layer of trees
Shrub layer
Herb layer
Ground cover layer
Climbing vine layer
Root layer

Instead of just picking one of those layers and planting one crop of that layer, the forest garden polyculture seeks to utilize each spacial layer and within each layer many varieties of plants. You will see tall over story trees widely spaced to allow plenty of light to the lower layers. Between these large trees will be a variety of smaller trees, some shade loving and some in full sun. Under and between these two layers of trees will be shrub type plants like raspberries. Some of these will also enjoy shadier spots, while some will enjoy it sunnier. Next comes the herb layer filling in the spaces around trees and shrubs where there is light to be had. The ground cover layer prevents weeds from growing in areas where there is sun and protects the soil from exposure. Climbing up the large trees will be different vine plants like hardy kiwi. Just another place for plants to grow. Finally there is the root layer. Here you get your root crops like potatoes or jerusalem artichokes. So much space to work with when you start to look at all the different layers.

By utilizing all the layers of a forest garden, there is massive potential for production in a relatively small area when comparing to a single crop. So we could call this the first benefit of polyculture: the huge diversity of productive elements makes for a continual harvest throughout the growing season, from spring asparagus, to summer raspberries, to fall apples, and winter root crops. You are not 'putting all your eggs in one basket' and betting all your work on a single crop harvest at the end of the season. If one crop fails one year, there are a multitude of other crops you will still be harvesting over the season.

Another excellent benefit of planting all the layers of forest polyculture, is the nonexistence of weeds. By taking each layer into account and planting so that all niches are filled by chosen, functional plants, there is no space for weeds to move in. This eliminates the need for weeding or herbicides to fight the weeds that would normally plague a garden. Even if one or two 'weed' type plants move in on your forest garden, they won't cause any harm because there won't be much room for them to grow. You can then observe the 'weed' growing there, decide on a plant you would rather have fill that niche, take out the 'weed' and plant your desired plant there. No more problem.

So far we have eliminated the time, money and energy required in keeping a cropped area weed free and the gamble of betting each years hard work and money on a single harvest. Things are looking pretty good for the forest garden polyculture!

How else can we make our lives and the lives of future generations easier using polycultures on the order of forest gardens? How about through eliminating the need for chemical fertilizers and pesticides? Sounds good to me! Let's see how it works.

Have you ever noticed how a forest keeps on growing without any human input? No fertilizer needed here to keep all these plants and trees growing year after year. Since a forest is the model we are basing our polyculture forest garden on, self fertilization is a key component to success. This doesn't happen randomly and must be taken into account when planning good design. The key lies in the nitrogen fixing plants. There are many and they come in all shapes and sizes, from annual ground covers and herbs, to perennial shrubs and trees. Most of the nitrogen fixing plants fall under the category of the legume family. The peas and beans.

The forest garden polyculture needs to have a certain percentage of these nitrogen fixing plants included in order for it to grow without input. Early on in the maturation of the garden, this percentage needs to be pretty high, but as the garden grows over the years and the main trees begin reaching climax, this percentage goes down a lot. When planning the percentage of nitrogen fixing plants in the garden, the time aspect needs to be taken into consideration. To start, there might be many annual nitrogen fixers. As the shrubs grow up, they will take over the space of the annuals and as the trees grow up, they will take over the space of the shrubs. Through succession you can plan on eliminating many of the initial nitrogen fixing plants over the years as the garden matures. As the garden matures, the amount of organic matter returned to the soil each year through such things as leaf drop and bird manures increases, further reducing the need for nitrogen fixing plants.

As the polyculture garden grows and matures, so does the soil life. These systems are perennial no till polycultures and because of this the soil life is not disturbed by tilling. Every time you till, about 30% of the organic matter in the soil is lost to the atmosphere. A major reason for the degrading soils of monocultures. By not tilling, the top soil becomes thicker each year with the added leaf litter and other organic matter breaking down. The deeper the topsoil, the more moisture it can hold and the longer plants growing in that soil can go without water. Deeper topsoil also means many more earthworms and microorganisms which deposit nutrients and make the soil even more fertile. All these factors add up to needing less nitrogen fixing plants as the garden matures.

Another super important benefit of a forest polyculture with no tilling is the growth of mycorrhizal fungi. This is a vast and not totally understood subject, but we will cover the basics here. Basically, when the soil life is not disturbed mycorrhizas grow around plant roots. These fungi create a network growing out from plant roots and interacting with other plant roots. This fungi net has a symbiotic relationship with the plant roots, by trading sugars from the plant for other micro nutrients the fungi web come across. So over time the entire underground soil area can be covered in this web of mycorrhizal fungi, connecting each plant to every other plant. Through this fungi web information and nutrients can be exchanged between plants over large distances. Information about fighting off a pest invasion can be transferred from plant to plant. If certain areas of the garden don't have the required nutrients, but another area does, these nutrients can be transferred via the mycorrhizal fungi web. Again, this is a super deep and amazing topic which I strongly encourage you to go and research further, but it's all we have time for now. Suffice it to say, mycorrhizal fungi are spectacularly awesome and tilling destroys them!

So many amazing benefits to polycultures! How about we look at the pest management aspect now.

Again we look to the forest as our mentor and it doesn't have any insect pest problems. Why? Functional diversity. Having a diverse polyculture means there will be a diverse selection of insects and other insect predators like birds. Certain insects are attracted to certain plants and situations. Increase the plant diversity and habitat and you increase the insect diversity and insect predator diversity. This leads to a balancing out. No one insect can reach a population level where it becomes a major threat to the garden because it is always being prayed upon by other insects and predators. If one insect level does reach large numbers, you can be sure there will be a similar increase in a particular predator right behind, levelling off the population. By creating habitat for birds, wasps, frogs, snakes, bats, and any other known predator of insects, your garden will have natural built in pest control. No insecticide required!

Wow! Just by setting things up properly and using a diverse polyculture, you can eliminate nearly all of the work and money the monoculture farmer has to invest year after year. No big tractor expense, no chemical fertilizers, pesticides, herbicides, no betting it all on one crop each year, and no irrigation.

Best of all it lasts for generations!
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