Thursday, April 3, 2014

Survival Gardening: Taking Care of the Soil

Intensive Versus Extensive Gardening

Survival gardening requires the "wide spacing" method, in contrast with the far-more-fashionable "intensive" gardening, because under truly survivalist conditions you would generally not use any water other than what falls from the sky. You might water brassica seeds until they sprout, and you should water tomato and pepper plants until you take them outside, but you will be unlikely to water anything once it has grown for a few weeks in the garden. Your rows will therefore be about 3 feet (1 m) apart, although in turn that means you will not be able to plant a huge amount of seed in each unit of land.

I have been told, by practitioners of intensive gardening, that by packing vegetables close together, and covering the soil with mulch, they end up using about ¼ or ½ as much water, in terms of the final yield of vegetables, as if they were planting the way I do, with single rows placed far apart.

I'm sure there is some truth to the claims of intensive gardeners. But it is also true that I get results that seem to contradict their claims. For example, I can remember that several years ago, when I had gone on a trip and been forced to abandon a garden during a long dry summer, the results were quite interesting: for one species after another, what had happened is that the closely spaced plants died and the widely spaced plants survived. (I tended to stuff plants into the garden rather haphazardly, so there was great variety in the spacing.) There seemed to be some sort of paradox: How could I be getting results that were the opposite of those of intensive gardeners?

First, let's clear up a small problem of definitions. Intensive gardening is also known as "wide-row" gardening, but that's a rather confusing term, because the word "row" might refer either to the plants themselves or to the spaces between them. With intensive gardening, the "row" is "wide" in the sense that there are there are many plants side by side. "Extensive" gardening, on the other hand, uses widely spaced rows -- in the sense that if we walk at right angles to those rows we cross a good deal of bare ground between one row and another. So let's not get confused: "wide spacing" is not the same as what are commonly called "wide rows." And now let's get back to that paradox.

A quick general answer to the "intensive-extensive" paradox is that we are really dealing with two things that have little in common. What I'm talking about is the survival or non survival of plants with irrigation and non irrigation. Practitioners of intensive gardening, on the other hand, are talking about crop yield and about varying amounts of irrigation -- and not about non irrigation. A second but relevant point is that wider spacing (i.e. plenty of bare ground) does in fact produce somewhat lower yields than closer spacing, so to that extent we're debating a non issue -- since the main purpose of wider spacing is to ensure survival, not to maximize yield.

But the precise answer involves some rather interesting arithmetic. It would be possible, I suppose, to create a chart showing all the different variables, and then the above paradox would fully resolve itself. Unfortunately there are an awful lot of those variables. But roughly speaking, one would have to show only two. The first would be the annual amount of water added to each unit of land; whether that water came from irrigation or from precipitation wouldn't really matter, since both types of water have the same effect. The second variable would show the density of planting (not the yield), or in other words the number of plants that were growing on a unit of land. Other variables could be ignored; the mulching is a separate issue, for example, and in order to show results clearly one would have to stick to one type of vegetable.

The greatest value of such a hypothetical chart is that one could draw a line across it, showing the optimum for the two variables. Too much water would result in wasted water, whereas excess spacing would result in wasted land. Too little water would result in dead plants, and too little spacing would also result in dead plants. There would, I suppose, be some interesting lumps and bumps on the chart, but I think the "paradox" would vanish.

Some of the findings of both "intensive" and "extensive" gardeners would be verified. Yes, it's true that "intensive" gardeners, using a garden hose, can reduce their water bill by packing their vegetables closer together. After all, what's the point in watering bare ground? But it is equally true that "extensive" gardeners, who are working with a far more limited amount of water -- only that which falls from the sky -- are going to have to keep their plants far apart and let them develop roots spreading out in all directions and far below the ground.

I suppose one could also say that "extensive" gardening is that of the desert, while "intensive" gardening is that of the jungle. A desert is less dense than a jungle, mainly because there is less water in a desert. So if you're concerned about available water, think in terms of a desert rather than a jungle.

As a final note (or to add further confusion?): yes, it's true that some arid-land plants grow in dense clusters, but their density per unit of land is still low. For example, there is a common plant called poverty grass or wild oats, Danthonia spicata, found on dry or barren land where no other grass can survive. It grows as clumps of short narrow blades from which arise long wiry stems. But from one clump to another there is always a good deal of bare ground.

Dry Farming

Strictly speaking, the term "dry farming" refers to farming without irrigation in areas of very low precipitation. West of the 100th meridian, from the Arctic all the way down to the southern tip of Mexico (but excluding the northwest), the continent is dry, receiving less than 20 inches (50 cm) of annual precipitation. But the problem of rainfall is a global one. Part of what makes dry farming practical in western North America is that the soil is often both deep and fertile -- at least where it remains in its natural state. The most successful crops are wheat, barley, sorghum, millets, legumes, and to a lesser extent corn. In all cases, only about half as much seed should be used as in the more humid areas of the continent.

Dry farming, in the strict sense of the word, requires fallowing: keeping part of your land tilled but unsown for a year. The only useful sort is "clean fallow," which means keeping the land entirely free from any form of vegetation, tilling it 3 or 4 times a year.

Organic Mulching

Dust mulching is not the only method of conserving water. An alternative to dust mulching is organic mulching -- applying a thick layer of straw, bark chips, wood chips, or some other fairly inert plant material. One big difference between dust mulching and organic mulching is that with the latter the plants might be grown very closely together rather than widely spaced. Dust mulching and organic mulching are therefore sometimes opposite means to the same end: conserving water. Organic mulches are usually not applied before vegetables have grown somewhat. They should also not be used in a cool damp climate, since they prevent the soil from warming up in spring, although they might be effective if applied in late spring. The soil must be well watered before the mulch is applied, or the mulch itself will prevent the vegetables from getting any water.

Organic mulches in turn can be classified as temporary or permanent. A temporary mulch is applied in the spring, usually on land that has been annually tilled. Permanent mulching is a more radical departure from standard gardening practice, since the soil is not tilled at all, except when the garden is first established. Several inches of material are applied to create the permanent mulch, and another inch or so are added each year, as the earlier material decomposes. Instead of tilling, the gardener simply pulls aside the mulch each year, adds the seeds or seedlings to a narrow trough, and then pulls the mulch back in place.

I should mention that organic mulching, either temporary or permanent, is of somewhat questionable value. Organic mulches help to retain moisture, but they can result in problems with bindweed, milkweed, bugs, and diseases. If you don't use chemicals, and if you always replant by saving your own seeds, then you're already taking a certain chance with diseases, even if you do everything else to keep your plants healthy, so why add to your troubles by leaving decaying mulch right next to your vegetables? The greatest problem, though, is that on any garden large enough to supply the bulk of the food (including grains) eaten by an average family, transporting enough mulching material would be rather difficult without several trips with a large vehicle, preferably motorized. Spreading the material would be a related problem. On the positive side, organic mulching might reduce erosion, particularly in windy areas. Whether dust mulching or organic mulching is better would also depend on the location: the type of soil, the climate, and so on. Organic mulches are no doubt worthy of further experimentation, particularly in more-southern areas with high temperatures and little rainfall, but their possible disadvantages must be considered.

Organic Matter

One way of analyzing soil is to say that it consists of inorganic and organic material. The inorganic material is the sand, silt, or clay. The organic material comes from the decay of plants and animals. When this organic material has decayed sufficiently, it mixes with inorganic material and forms a dark homogeneous layer toward the surface of the ground, whereas several feet below the surface there might be virtually no organic material. This dark material is known as humus. The organic material in cultivated land can be derived from animal manure, from a compost heap, from "green manure" (a crop grown to be turned under at a certain stage of growth), or from the turning over of sod when grassland is converted to farm land.

Organic matter has a number of effects on the ability of the soil to support plant life. The first effect is mechanical: organic matter holds both air and water in the soil. As a result, it can keep a loose soil from crumbling too readily, and conversely it can loosen up a sticky, clayey soil. The second effect is chemical: organic matter contains many of the elements needed for plant growth and is part of the process of recycling. The third effect is biological: countless organisms, mostly microscopic, live within the organic matter, and these organisms are essential to the fertility of the soil.

Sixteen Elements

Whether you use synthetic fertilizers or more "natural" sources, it is likely that your land will need certain nutriments added to it. Have a soil test done, or do your own, or learn to recognize the symptoms of deficiency. Calculate the amount of fertilizer you'll need, and till this into the ground before you start planting; synthetic fertilizer in particular will kill roots if it touches them without first being mixed into the soil.

The plants we grow contain 16 elements of importance: boron, calcium, carbon, chlorine, copper, hydrogen, iron, magnesium, manganese, molybdenum, nitrogen, oxygen, phosphorus, potassium, sulfur, and zinc. Carbon, which is the main building material of plants, comes from the carbon dioxide in the atmosphere. Oxygen also comes from the air. Nitrogen is another element taken from the air, attaching itself to the bacteria in the root nodules of certain plants, particularly legumes.

Three of those elements, nitrogen, phosphorus, and potassium, are quite critical, not in the sense that they are the most important constituents of plants, but because they are the ones most likely to be inadequately supplied. Whenever plants are harvested, removed from the fields, and consumed by humans or livestock, a certain amount of these three elements is also removed from the fields, because they have been absorbed by the plants. If we harvest a crop of potatoes from an acre (0.5 ha) of land, about 150 pounds (70 kg) of potassium oxide (potash) might also be removed. The potatoes are eaten, and the potassium eventually ends up in the sewage system. Perhaps some of the potato peelings will be fed to animals, or be put on a compost heap, and a small portion of that potassium will thereby end up back in the soil.

Of those three elements, nitrogen is the most likely to be lacking, because it is highly soluble. Fortunately, a deficiency in nitrogen can easily be remedied by planting legumes.

When crops are fed to livestock, much of the nitrogen, phosphorus, and potassium ends up back on the soil as manure, but even some of this will be lost through leaching (the effect of rain). A fair amount of those minerals will go to form the bodies of the animals. When the animals are later slaughtered, perhaps some more of the nitrogen, phosphorus, and potassium will become fertilizer and go back into the soil. Most of the animal's meat and milk, however, will be consumed by humans and end up as unreclaimed sewage.

Whether it is plants or animals that become human food, the soil is always losing important minerals. In traditional Asian cultures, this loss was kept to a minimum by strict control of the recycling of human and animal waste, but even in a reclamation system of that sort there would always be losses. To offset the losses, farmers brought wild vegetation from the mountains, or they dredged mud from the mountain-fed waters of the canals. In western cultures, land was usually "fallowed" -- left to go wild for perhaps 1 year out of 3, so that the naturally occurring weeds might revitalize the land. Generally, however, western cultures have paid far less attention to the recycling of minerals. But one way or another, if land to is to keep producing, those essential minerals must be put back into the ground, whether we use "natural" fertilizers or "artificial" chemicals.

There is actually a fourth element that can be critical at times, and that is calcium. Most soil contains enough calcium for agricultural purposes, but in some areas there may be a lack, and the result is what we call acidic soil. One of the main purposes of calcium is to modify some of the complex chemicals that are naturally found in the soil. There are various mineral compounds containing potassium and phosphorus, and while some can be used directly by the plants, others need to be broken down by calcium.

Plants show various symptoms when these elements are lacking, although it is sometimes possible to mistake such symptoms for those caused by disease or bad weather. Generally, though, a lack of nitrogen makes a plant's foliage thin and yellow; the plant is also likely to be slow-growing and more susceptible to disease. A lack of potassium weakens the stems and branches, which are then are easily broken by the wind, and the underside of leaves may be reddish-purple. A lack of phosphorus makes fruit and seeds mature more slowly than usual; the leaves may be purple all over. When corn (maize) is lacking in phosphorus, however, the leaves are yellow, as if lacking in nitrogen; the ears may be missing some kernels, and the stalk may become brown or bronze. Calcium deficiency in most types of crops usually results in slow growth and thick woody stems; when corn is deficient in calcium, however, the tips of the leaves are stuck together as if with glue.

Many organic-gardening books seem to imply that you can grow amazing crops just by increasing the organic matter of your soil -- keeping a compost heap, for example, and turning that organic matter into your soil, or buying a few bags of cow manure. That's not true. If you're trying to grow crops on land that is fundamentally barren -- sand, rock, or swamp, for example -- then adding manure is only going to solve part of the problem, because a garden or farm needs both organic matter (humus) and the 16 elements that make up naturally fertile land: nitrogen, potassium, phosphorus, and all the rest.

The only thing you might be able to do with barren land is to invest in a lifetime supply of artificial fertilizer, before the price gets any higher. Get it from a farm-supply store; hardware stores will charge about 6 times as much. You would still need to find a source of humus for that land, either by growing grass or something else you could dig in when it had grown sufficiently, or by hauling in vegetation from somewhere else.

Acidity and Alkalinity

The acidity or alkalinity of a soil depends partly on the type of rock that the soil comes from. If the rock is limestone, the soil will of course be alkaline. The way in which vegetation decomposes can also have an effect on the acidity: heavy rainfall, for example, can increase the acidity of the soil. The degree of acidity or alkalinity is usually expressed as a "pH" value; the term refers to hydrogen-ion activity. The pH scale runs from 0 to 14; the lower end is acidic, the upper alkaline. In North America, the "lime line" is nearly the same as the line dividing wet lands from dry lands -- roughly speaking, the 100th meridian. Soil in western North America, in other words, is often high in calcium (lime), while soil in the east may be deficient.

Most farm crops do best in soil that is close to neutral, or perhaps slightly acidic: a pH of 6.5 to 7.0 is usually ideal. Some crops can tolerate a fairly broad range of pH. Peanuts, potatoes, raspberries, and sweet potatoes do best in a slightly acidic soil. Other crops prefer or require somewhat alkaline soil: among the more important are asparagus, beans, beets, cabbages, onions, peas, rhubarb, and squash. Oats can do well on somewhat acidic soil, whereas barley and wheat prefer alkaline soil, and rye does well on either.

Soil can be made more acidic by adding plenty of compost. Anything that increases the level of organic matter is going to neutralize excess alkali in the soil.

Increasing the alkalinity of an acidic soil requires adding organic or inorganic material that contains calcium. Powered limestone is ideal if available. Even better is powdered dolomite, which contains both calcium and magnesium. Wood ashes can also be a good source of calcium, although the nature of the ash would depend on the type of trees and the soil on which they were grown. The shells of fresh or saltwater mollusks can supply calcium. Bonemeal is commonly used in "organic" gardening, although its environmental effect is ironic: a vegetarian diet allows a far greater yield of protein per acre than a diet of meat, so the conversion of animals into bone meal, and thence into vegetable food, is quite the opposite of "sustainable agriculture." Be careful: people often add calcium to their soil when it is not necessary. Not only is that additional calcium a waste of money, but it can actually decrease the yields of some crops.

From a practical point of view, the best thing you can do to maintain the correct pH of your soil is to keep it well supplied with compost. If your soil is naturally too acidic or too alkaline, you will need to bring in materials from outside the garden. You may need to do as the farmers in eastern Asia used to do: go off into the hills and bring back wild vegetation that can be turned into rich compost.

Cover Crops

Depending on the specific techniques you're using, the topics of "composting," "mulching," "green manures," and "cover crops" tend to overlap. Strictly speaking, however, cover crops are crops that protect the ground from erosion after food crops have been harvested. Cover crops are normally sown, therefore, in the fall. When spring arrives, they are left to grow again for a few weeks and then dug into the soil. Cover crops also add organic material to the soil, and bring nutrients up from underground. If legumes are used, a cover crop will also add nitrogen to the soil. A cover crop is normally sown quite thickly, so another useful effect is to prevent the growth of weeds. Some commonly used species are rye, wheat, rye grass, and buckwheat. One drawback to cover crops is that they can be labor-intensive, and you may need to cut the crop with a scythe before you start digging.

Green Manures

Green manures are crops that are grown solely for the purpose of turning them under to increase the organic matter content of the soil. They provide a method of adding fertilizer well below the surface, something you can't always accomplish by composting in the usual sense. In particular, green manures improve the soil by the decay of their roots, which may have reached many feet down into the soil. In addition, green manures provide organic material at the height of its usefulness: you can dig the plants into the soil at exactly the right stage of their maturation, and with none of the problems of leaching that can occur with ordinary compost heaps.

In order to take full advantage of green manures, turn them under and then leave them until they have just finished decaying. In warm weather, this period will be less than 3 weeks. Because they fix nitrogen, legumes such as beans, peas, clover, alfalfa, and vetch are often used as green manures. Rye, barley, and buckwheat are also commonly used. Even weeds can serve the same purpose, especially if they are turned under before they go to seed.

Except in terms of purpose, there is not much difference between cover crops and green manures. One possible disadvantage is the same: with hand tools, working a green manure into the ground can be a fair amount of work, although buckwheat is easier than others.


Peter Goodchild

Author of Tumbling Tide: Population, Petroleum, and Systemic Collapse (London, Ontario: Insomniac Press, 2014)