Building soil with the four-field rotation

One of the key things we have working for us as we go forward into a future where energy isn’t quite as abundantly cheap as we’re used to, where cash is hard to come by and where more needs to happen locally as a result, is that we have a lot of past knowledge we can draw upon.

Take, as an example, the study of Viscount Townshend in the early 18th century into agricultural production.

Mediaeval Europe had long known about the three-field rotation (or, if you prefer, rotating amongst three uses of the same field). Planting the same crop year after year in the same field depleted the soil, leading to lower yields. Fertilisers, in turn, could “restore” the soil, but only up to a point.

We, of course, chucked all of this knowledge on the ash-heap of history once we could crack petrochemicals to make fertilisers in abundance. Our farmers now crop the same thing year after year, destroying the soil but “enhancing” it back.

What Townshend found was that a four-field rotation actually raised the overall productivity of the land over the three-field rotation that had been used for centuries.

Each crop that’s planted offers the soil a different set of inputs thanks to its growing, while simultaneously drawing upon different elements from the soil to grow. The four-field process gives adequate replenishment to all the elements needed. Result: agriculture, at continued high productivity, without fertilisers.

The soil not only maintains itself: its fecundity increases.

In fact, it’s been estimated that if the United Kingdom returned to the four-field method — and ceased using land for animal husbandry (in other words, less meat in the diet: parts of the Scottish Highlands are suitable for little else other than grazing) — it would have no trouble feeding itself abundantly from its own resources, with no petrochemical inputs required (some farm animals would be kept for dairying, eggs and hauling things like ploughs and carts if they wanted to go completely oil-free).

Britain hasn’t been able to feed itself for over two centuries now. It’s why it became a naval power: to keep the food ships coming in.

There’s a lot of talk today about how chunks of derelict cities — Detroit comes immediately to mind — are turning back into agricultural zones as abandoned blocks are being re-tilled.

Fair enough. All cities — the healthy and the derelict — could do a lot more to feed themselves locally, just as a hundred years ago they used to provide a fair amount of their fruits and vegetables within the community.

But land that’s been built on has soil that’s in particularly rough shape. Peeling the buildings off a plot doesn’t suddenly “discover” good growing land, even if it was prime agricultural land before being built on (in New York City, for instance, as the street grid marched relentlessly north up Manhattan Island, farms were overrun — a memory of this remains in Central Park’s “Strawberry Fields”).

James Howard Kunstler, in Home from Nowhere, spends a chapter chronicling the story of a farmer who rehabilitates farmland in the Hudson Valley north of Albany. It takes him years to improve the soil — and it wasn’t built upon, merely overfarmed without attention to soil health in the past.

Anyone who’s seen people working assiduously in community gardens in a city — almost always on derelict land — see how many years of hard effort it takes to create viable, sustainable soil in such places. Backyard gardens after years of “lawns” — especially those kept “dandelion free and lush” with chemicals — take half a decade or more as well.

So it would make sense to think smart about this before diving into local food production.

Four neighbours could agree, for instance, to run a rotation between them. Year one, my yard is in clover, to help build the soil. Year two, my neighbour does clover, while I move on to a grain crop like wheat. Year three, my neighbour does wheat, his neighbour does clover, and I move on to barley. Year four, the last house is in clover, everything moves down the line, and I plant turnips. Year five, I’m back to clover again.

(That’s the rotation Townshend used. There are others that can be done that follow the same principles of “what this crop takes from the soil and what it puts back”.)

Closely coupled with this will be the need to shift back to varieties that are appropriate for the specific soils in an area, and the micro-climates involved.

The Fraser Valley in British Columbia, for instance, used to be intensely productive with its own wheat, a particular strain well-suited to the delta soils and micro-climate of the temperate west coast rain forest. It fell into disuse — and the valley shifted from wheat to other crops — as the triticale wheat strains used on the Prairies took over the market. But triticale isn’t as well suited to the Fraser Valley as its old Red Spring Wheat was.

In an era of less food being transported — one consequence of energy price constraints — crops that aren’t ideal will nevertheless have to be grown, or that foodstuff done without. (And people do like their breads!) So using the heirloom strains will matter.

Backyard gardeners looking to convert from lawns and flowers to a little local food, therefore, would do well to consider how to handle crop rotation to build up soils, and to use the heirloom strains suited to their area (and keep an eye on how changing climatic belts may change which heirlooms would suit a region better).


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: