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Growing Food When The Oil Runs out

By Peter Goodchild

12 December, 2007

Most people in modern industrial society get their food mainly from supermarkets. As a result of declining hydrocarbon resources, however, it is unlikely that such food will always be available. The present world population is nearly 7 billion, but food supplies per capita have been shrinking for years. Food production will have to become more localized, and it will be necessary to reconsider less-advanced forms of technology that might be called "subsistence gardening."

The peak of world oil production ("peak oil") will be at some point in the early 21st century; it is quite possible that we are already past that event. The "peak" will be (or was) about 30 billion barrels of oil a year, but by 2030 annual production will be less than half that amount [2, 4]. Without oil and other hydrocarbons, there will be no fuel, no plastics, no chemical fertilizer. Alternative energy sources will do little to solve the problem [16]. Partly as a further consequence of declining oil supplies, electricity and metals will also be in short supply [8]. But in terms of daily life, the most important effect of oil depletion will be a shortage of food.

The effect of oil depletion on food is partly obscured by two separate but related issues: skyrocketing food prices and the great increase in biofuel production [6, 9, 10]. In the present chaos, however, to follow questions of money is to go on a wild-goose chase, while biofuel production can only be seen as a mad attempt to evade the problem of oil depletion while depriving the world of needed food.


Subsistence gardening might be defined as having three characteristics. In the first place, as much as possible it involves less-advanced technology; reliance on machinery and chemicals will not be possible without a global economic network to support them, whereas a shovel, a hoe, and a wheelbarrow (with a non-pneumatic tire!) are probably a once-only purchase.

Secondly, it is water-efficient. Without a municipal water supply or a motorized pump, water for agriculture will no longer be abundant.

Thirdly, subsistence gardening entails a largely vegetarian way of life: the growing of crops takes less land than raising animals (although some animals can make good use of less-fertile land), and it is less complicated. With a largely vegetarian diet, of course, there can be a danger of deficiencies in vitamins A and B12, iron, calcium, and fat, all of which can be found in animal food. Most of these deficiencies are covered by an occasional taste of meat; daily portions of beef and pork are really not necessary. Animal husbandry does not have to be large-scale; in sparsely populated areas, even fishing, trapping, and hunting can be useful skills.


New land should be broken with a plow, a device that generally requires either a tractor or a draft animal, but a fair amount can be done with hand tools. Much depends on the time of year and the weather. In the spring after a good rain, it is possible to dig up 50 m2 in a day, even if one is not especially muscular. In August after a long drought, however, digging even 5 m2 in a day might be hard. But there are ways to the task easier: if the grass is long, it can be cut with a scythe before the digging begins, and hot weather can be avoided by starting work at sunrise. When the sod has been dug up, it can be shaken thoroughly to release the soil, and then piled up and burned.

Actually many of the native North Americans preferred forest, rather than grassland, as sites for agriculture. The forest land was more fertile, and digging up heavy sod would have been arduous with the available tools. The native people girdled the trees (i.e., cut a ring of bark from around each tree) to kill them, and then felled the trees much later, with fire and axes.


Besides grains and fruits, the most useful food plants in temperate climates belong to about nine families, including the Amaryllidaceae (garlic, leeks, onions), Chenopodiaceae (beets, chard), Brassicaceae (broccoli, Brussels sprouts, cabbage, collards, kale, kohlrabi, rutabagas, turnips), Leguminosae (beans, peanuts, peas), Umbelliferae (carrots, parsnips), Convulvulaceae (sweet potatoes), Solanaceae (peppers, potatoes, tomatoes), Cucurbitaceae (squash), and Compositae (sunflowers).

A good general rule is to choose old-fashioned (including "heirloom" or "heritage") varieties rather than modern, big plants rather than small (but small fruit rather than big), pole or vine rather than bush. Popular varieties over the last several decades, unfortunately, have been heading in the opposite direction. Commercial growers want faster varieties, urban gardeners want small ones. Choosing varieties that are hardy and drought- resistant means going in the opposite direction. The rule does not always work — bush beans are not necessarily worse than pole beans, for example — but it serves as a guide. A somewhat similar guide is to look for something that closely resembles a wild plant, or is roughly the same thing as a wild plant — dandelions, mustard, or purslane, for example.

Modern-day city-dwellers who live sedentary lives are likely to focus on low-calory food. Those concerned about subsistence gardening, however, will want to do the opposite: country living requires substantial meals. Subsistence gardening means the production of a large number of calories with a small amount of labor and a small amount of risk, and perhaps with not much land. With these factors in mind, one could say that there are not so many crops worthy of attention. There is no such thing as a perfect type of food to grow, because there are advantages and disadvantages to every type. Reliance on a single crop would be dangerous, and variety is essential. We never know exactly what will happen, and no rules are absolute. The following notes are based on a North American perspective, but they can be applied more generally to conditions in other parts of the world.

Many of what might seem obvious choices may be questionable. Potatoes are highly susceptible to Colorado potato beetles, blight, and several other pests and diseases. Most grains might be difficult to grow without a plow (with a horse or tractor) and other specialized equipment. The brassicas are excellent for vitamins and minerals, but some of them are bothered by pests and diseases; kale is perhaps the least trouble-prone.

A good starting point might be to focus on corn (maize), beans, and squash, the main crops grown by the native peoples of North America. These three crops are easy to grow, and they require little or no watering if the plants are well spaced. Corn and beans, eaten together, provide excellent protein.

Corn has the scientific name of Zea mays and several confusing common names. There are basically two types of corn, sweet corn and field (grain) corn, although these are not botanical distinctions. The former is the type that is usually eaten as "corn on the cob." Sweet corn, unfortunately, is unsuitable for drying, and it has more problems with diseases and insects. Field corn, on the other hand, is definitely worth growing. It has a higher yield per hectare than any other temperate-climate grain, and unlike other grains it requires no complicated threshing or winnowing.

It is essential to grow only open-pollinated varieties of corn; hybrid types do not reproduce properly. In modern times, however, one is unlikely to find varieties of corn that qualify as both "field corn" and "open-pollinated," with the exception of those colorful varieties that are generally known as "Indian" or "ornamental" corn. Of those, the hard ("flint") types do better in areas where spring or fall frosts may be a danger.

Beans (e.g., Phaseolus vulgaris) and other legumes are another important part of the diet, especially for people on a vegetarian or largely vegetarian diet. Beans are high in protein, they are not demanding in terms of soil or climate, and they need little or no irrigation, at least after they have produced a few leaves. Unlike most other plants, legumes actually add nitrogen to the soil; traditional agriculture has always relied on their vital service.

Squash can be divided informally into the soft-skinned "summer" types and the hard-skinned "winter" types. Summer squash, however, provide only 167 kcal/kg, as opposed to 475 kcal for winter squash, so it is the latter that are more important. All squash are members of the genus Cucurbita, and of these the three main species are C. maxima, C. pepo, and C. moschata. C. maxima includes Buttercup, Hubbard, and Delicious, all of which are drought-resistant. C. pepo winter squash worth growing are Acorn, Spaghetti, and the "true" pumpkin (a lot of so-called pumpkins are a type of C. maxima); these are also drought-resistant, but Acorn squash is not especially good for storing. Of the C. moschata types, the most familiar is Butternut; while it is not noteworthy for being drought-resistant, it is one of the best squash for storing. In general, vining squashes are more drought- resistant than bush types.

For green vegetables and fruit, one can sometimes even supplement the diet with wild plants. There over a dozen species of wild fruit to be found within a 10-minute walk from my own house here in central Ontario, and this is a rather infertile part of the world.


The amount of land needed for subsistence gardening depends on several factors, including the type of soil, the climate, and the kinds of crops to be grown. The following, however, may provide some rough figures.

The production of corn can be used as the basis for calculations, if we pretend for the moment that someone is going to be living entirely on corn. A hardworking adult burns about 5,000 kcal/day, or 1.8 million kcal/year. With fairly primitive technology, corn yields about 2,000 kg/ha, or 6.9 million kcal [13]. One adult, therefore, would need about 0.26 ha of land; it would be safer, of course, to use twice that much land. (Incidentally, the world even now has a density of only 3.3 people per hectare of arable land, but that does not account for unevenness of distribution, or for other use of the arable land.)

Oddly enough, if other crops are substituted for corn, there is usually no enormous difference in the number of kcal produced per ha. Beans (as "dry beans") produce about half the yield of corn. Root crops (turnips, carrots, beets, etc.) are impressive in terms of their bulk — mass — per ha, yet they do not differ greatly from corn in kcal/ha.


Most of the world’s land is not suitable for agriculture. Either the soil is not fertile or the climate is too severe. Anyone intending to buy a piece of land should take a sample of the soil and have it tested by a government-approved laboratory, while that kind of service is still available. If the soil is really poor to begin with, and especially if it is very low in potassium or phosphorus, there is not a great deal that can be done about it, at least with the resources available in a survival situation.

If most of the trees are evergreens, the land is too acidic. Acidic soil may also be indicated by chamomile, garden sorrel, mayweed, or sheep sorrel. Land that is excessively wet due to poor drainage may be growing buttercup, cattail, ferns, ironweed, Joe-Pye weed, or loosestrife. Other weeds might be indicators of reasonably good soil: amaranth, burdock, lamb’s quarters, purslane, ragweed, or thistles

Soil used for the growing of crops must have adequate amounts of organic matter (humus), which can come directly from decomposed vegetation or from animal manure. Organic matter holds water and air in the soil, contains — often to a rather limited extent — some of the elements needed for plant growth, and provides an environment for small organisms that are essential to the fertility of the soil.

Farmland must also have adequate amounts of about 16 elements — naturally occurring or otherwise. Of these 16, the most critical are phosphorus (P), potassium (K), and especially nitrogen (N). Calcium and magnesium are probably next in importance. Some of the elements may be found in organic matter, but the quantities are generally insufficient. These elements might be abundant in the soil before any cultivation is done, but whenever crops are harvested a certain amount of the three critical elements is removed.

The problem of inadequate amounts of the 16 elements is generally remedied nowadays by adding fertilizer, which can be artificial or can come from such sources as rock dust — the latter a fashionable "soil amendment" that will no longer be available without hydrocarbon-based mining and transportation. Acidity can be counteracted by adding crushed limestone (again, not likely to be available) or wood ashes, which contain calcium. Nitrogen, however, can be provided by planting any legume, such as beans or peas, since bacteria in the roots take nitrogen from the air; the plants must be dug back into the soil, of course.

Primitive societies had a simple but imperfect solution to the problem of maintaining fertility: abandonment. No fertilizer was used, except for ashes; as a result, the soil became exhausted after a few years, so the fields were abandoned and new ones were dug.

A common response to the N-P-K problem, used in many countries for centuries, has been to turn crop waste into compost and put it back onto the land. The problem with that technique, however, is that one cannot create a perpetual-motion machine: every time the compost is recycled, a certain amount of N-P-K is lost, mainly in the form of human or animal excrement after the crops are eaten, but also as direct leaching and evaporation [11]. One can come closer to sustainability by recycling those human and animal wastes, but the recycling will always be less than perfect. After all, nitrogen, phosphorus, and potassium are elements, and by definition they cannot be created. Of the three main elements, nitrogen is by far the most subject to loss by leaching, but to some extent that can also happen with phosphorus and potassium.

There are partial solutions that are worth considering. Besides using vegetable compost and animal manure for increasing the sustainability of agricultural land, many societies have employed such related techniques as crop-rotation, fallowing (leaving land uncultivated for a year or so), cover-cropping, and green manuring. Such practices also replenish the humus content of the soil. Some of these practices can even partly replenish the phosphorus and potassium, since plants with deep roots can draw such elements to the surface. Some of these techniques are difficult with hand tools, however. In other countries, vegetation was brought in from the hills, or mud was taken from streams that ran down from the mountains [12].


The term "irrigation" refers to any use of water other than the direct use of rainfall or other natural precipitation. In a post-oil economy it will not be possible to used a motorized water supply for irrigation. Yet if one were to try using an old-fashioned hand pump to get the water out of the well, a good deal of manual labor would be involved. A garden needs about 2 or 3 cm of water a week. On a garden of 0.26 ha, that amounts to 66 m3 of water. That would mean carrying a bucket to the pump about 2,300 times a week, except when it rained. Not very practical.

What the North American native people and pioneers did was to give the plants plenty of space, and then just rely on the rain [14]. Almost any type of crop, given enough room, can be left to the mercy of the weather, although some crops need to be watered as seeds or seedlings. The essence of water-efficient gardening is to space the plants out so that the distance between them is greater than most modern gardening manuals recommend. That way the roots can spread out and explore in all directions to find the water that has been stored there over the previous months.

To keep that underground moisture from evaporating, a hoe must be used to remove all weeds, because most water vanishes through plant leaves. Hoeing also keeps the surface of the ground watertight by creating a "dust mulch": water does not easily pass through a layer of well disturbed dust, since the lack of water and the separation of particles prevent capillary action. ("Organic" mulches, such as wood chips or hay, are not much use on an entire garden; even if one could find enough material for so much land, there would be further trouble with bugs, weeds, and cold soil.)

If the garden has at least 1 meter of soil, and if there is also close to a meter of precipitation annually, with that moisture spread out fairly evenly over the 12 months, then it is possible to garden without irrigation.

On the other hand, if there is only about 30 cm of soil above the bedrock, or if there is less than about 50 cm of precipitation annually, gardening without irrigation is still possible, but the plants need to be spaced out far more.

Contrary to popular belief, in other words, "intensive" gardening is not practical without a garden hose and an unlimited supply of water. More plants per unit of land simply means using more water per unit. With such a method, the lack of bare ground between rows also means that it is not easy to get a hoe to the weeds; as L.H. Bailey said long ago, intensive gardening is just "cultivating the backache."


The following topics apply mainly to the control of insects, but roughly the same are relevant to the control of more primitive forms of life, such as fungi, viruses, and bacteria: (1) selection — choosing resistant species and varieties; (2) diversity — growing a fair number of species and varieties at the same time (avoiding monoculture); (3) rotation — not growing a crop in the same place in the following year; (4) health — keeping plants strong by providing good soil and enough water, light, and space; (5) sanitation — removing and burning any dead or dying plants, and avoiding contact with wet plants; (6) tillage — digging up the ground each year to destroy insects; (7) attack — fighting insects by handpicking; one might also want to experiment with sprinkling wood ashes or spraying solutions of garlic, hot pepper, or soap.


One way of storing vegetables for winter is to keep them in a root cellar or something similar. The basic idea is to keep the food just above freezing. In pioneer times a root cellar was often little more than a cave dug into a hillside and provided with a door. The earth provided the necessary coolness and humidity to keep the vegetables fresh all winter long. Nowadays a root cellar can be made by walling off a northern corner of a basement, including a window that can be opened to regulate temperature.

Rutabagas, carrots, beets, and parsnips require packing in damp hay, sand, or some other damp material to prevent shriveling. Turnips do not store as well as rutabagas. Potatoes and onions should be kept in loosely woven bags or at least open boxes, in a dark room. Winter squash need slightly warmer conditions than other stored crops.

Another simple method of storing is to build a clamp, which is an outdoor mound of vegetables placed on a 30-cm layer of dry vegetation (hay, leaves, or similar material), then covered with another 30-cm layer of dry vegetation, and finally covered with a layer of earth. Usually some sort of drainage is provided by digging a trench around the clamp, but that is easily done as the soil is dug to be put on top of the clamp. Clamping is simple and cheap, but it is not always successful: a winter might be extreme, freezing and ruining the food or solidifying the mound too much for it to be opened.

Drying is a good technique for preserving almost any crop. Grains and beans are very easy to dry. Squash can be peeled and cut into strips or spirals 1 or 2 cm wide, then hung up to dry in the sun. Beets, turnips, rutabagas, and carrots can be dried the same way. Fruits can also be spread out in the sun. Leafy vegetables can be tied in bunches and hung in the shade to dry for a few days before being packed into jars; in winter, these dried leaves can be crumbled and added to soup.


Producing one’s own supply of seeds means keeping an eye on the more-desirable plants, and earmarking those for the next year’s crop. The best plants should be chosen, not the earliest; contrary to popular belief, seeds that appear late in the season do not produce slower plants the next year. Hybrid vegetables should always be avoided, of course, because they do not reproduce properly.

There are two methods for producing seed, although they overlap considerably. For the first method, crops are just be left in the ground until they to go to seed. Annuals are the simplest crops to deal with, since they go to seed in the first year, and often the seed is precisely what is eaten; grains and beans are obvious examples. Biennials (two-year plants) — most brassicas, for example — are also possible candidates for this method. The main question is whether the biennials can be left in the ground over the winter, and the answer to that depends on the species or variety, on the climate, and perhaps on whether the selected plants are covered in winter with something such as leaves, grass, straw, or even twigs.

The second method is to dig up the plants at the end of the first summer, store them carefully over the winter, and then replant them. This second method requires more work, but it is safer, and it also allows one to "rogue out" (remove) stunted or deformed plants.

In most cases it is best not to grow more than one variety of a vegetable for seed, because varieties will cross and produce offspring with uncertain qualities. Growing more than one variety is possible, however, if they are allowed to go to seed in alternate years, or if the varieties are planted several weeks apart so that they do not blossom at the same time.

Seeds need proper care if they are to stay viable. The longevity of seeds can be a single year or it can be many years, depending on the species, but that longevity can be increased by careful storage. Most seeds need to be kept very dry, and most also need to be kept away from light, so they should not be stored in glass jars, and it is important that they be sealed against insects or larger creatures.


1. Ashworth, Suzanne. Seed to Seed. Decorah, Iowa: Seed Saver, 1991.

2. BP Global Statistical Review of World Energy, annual.

3. Bradley, Fern Marshall, and Barbara W. Ellis, eds. Rodale’s All-New Encyclopedia of Organic Gardening. Emmaus, Pennyslvania: Rodale, 1992.

4. Campbell, Colin J. and Jean H. Laherrère. The End of Cheap Oil. Scientific American, March 1998.

5. Duncan, Richard C. The Peak of World Oil Production and the Road to the Olduvai Gorge.

6. Earth Policy Institute. Earth Policy Indicators.

7. Emery, Carla A. The Encyclopedia of Country Living. 9th ed. Seattle, Washington: Sasquash, 1994.

8. Gever, John, et al. Beyond Oil: The Threat to Food and Fuel in the Coming Decades. Cambridge, Massachusetts: Ballinger, 1986.

9. Food and Agriculture Organization of the United Nations. Food Outlook: Global Market Analysis, November 2007.

10. Heinberg, Richard. What Will We Eat as the Food Runs Out?

11. Hopkins, Donald P. Chemicals, Humus, and the Soil. London: Faber & Faber, 1957.

12. King, F.H. Farmers of Forty Centuries. Emmaus, Pennsylvania: Organic Gardening, n.d.

13. Pimentel, David, and Carl W. Hall, eds. Food and Energy Resources. Orlando: Academic, 1984.

14. Solomon, Steve. Water-Wise Vegetables. Seattle: Sasquatch, 1993.

15. Weatherwax, Paul. Indian Corn in Old America. New York: Macmillan, 1954.

16. Walter Youngquist, "Alternative Energy Sources."

Peter Goodchild is the author of Skills of the North American Indians, published by Chicago Review Press. He can be reached at

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