Biointensive Gardening

This article was written in 1991 and some of the remarks about cadmium are no longer applicable.


The Ecology Action Group in California has been developing a system of gardening based on selected aspects of the French-Intensive and Biodynamic gardening methods for 30 years. It consists of raised beds 1-1.5 metres wide and as long as required. The soil is very heavily composted, about 25 mm being added per crop, to allow much closer planting than is usual, without sacrificing yield. The high humus levels created reduce watering needs, due to the much higher water retention by the organic matter. As the beds are raised about 100- 150 mm, drainage Is never a problem.

The footpaths between the beds are about 300-450 mm wide and allow cultivation and weeding to take place without walking on the beds, reducing the amount of cultivation required. In conventional gardens, much of the cultivation is repairing the damage due to soil compaction caused by trampling the soil. Plants are grown in evenly spaced blocks rather than rows. While this barely affects the yield per unit area of large plants, such as brassicas, the yields of carrots, onions, and lettuce can be dramatically greater.

The increase in yield per unit area reduces the amount of time required for many garden operations, such as cultivating, weeding, watering and composting, since a smaller garden is required to satisfy a family's needs. The advantages of the system are so great that many commercial vegetable growers have adapted it to a mechanised system. The tractor tyres are confined to running in the between bed 'footpaths' and the grower benefits from the reduced amount of expensive cultivation, as well as the higher yields.

Since the garden becomes divided into clearly defined areas, planning rotations and crop requirements is greatly simplified. As an example, a temperate climate family might require an average of two carrots a day from early summer to early spring. The superb drainage of the raised beds enables the carrots to be harvested as needed, rather than lifted and stored. Two carrots per day for ten months is about 600 carrots. Each carrot requires about 60 square centimetres of growing space, so a 1.2 metre wide bed would need to be 3 metres long to accommodate this need. As the carrots are dug, the soil is raked smooth, composted and replaced by peas, lettuce, brassicas, or whatever suits the planned rotation of the gardener.

In a temperate climate, a 130 square metre garden (including paths between beds), is sufficient to grow the needs of a family of four in a six month growing season. In a harsher climate, a garden twice this size might be needed. Advantage is taken of the wide spaces between slow growing crops, such as cauliflowers, to grow quick maturing crops, such as lettuce and radish.

The method, as originally published by John Jeavons, requires double-digging. That is, the soil below spade depth is broken up with a garden fork. This extra labour may not be necessary , especially where deep frosts are prevalent. Unless the subsoil is particularly compacted, digging to a spade's depth should be all that is necessary , and that only once during the creation of the raised beds. Providing sufficient compost is applied, further deep cultivation will usually be unnecessary. Deep-rooting crops and a multitude of earthworms do much of the soil aeration required for plant health. After eight years, the writer's own garden was still increasing its yields without double-digging as the tilth of the rather heavy soil improved.

Weed growth in the footpaths can be utilised for compost and/or mulch. Just chip them off with a sharp spade. Due to compaction of the soil in the paths, this growth is minimal. Alternatively, lay down sheets of heavy cardboard and cover with sawdust, wood chips or pine-bark. This certainly makes a more pleasant sur face to walk on, especially in wet weather. Sawdust, lightly sprinkled with lime, breaks down within a year to the point where it can be shovelled onto the garden bed as a mulch.

What is Organic Gardening?

The use of the word "organic" to describe non- conventional agriculture, was chosen by Sir Albert Howard between the two World Wars. He wanted the word to convey the concept of organism. That is, the farm or garden needs to be viewed as a whole, not as the sum of a few, unrelated separate parts. Conventional agriculture sees the production of food and fibre as a factory, where imported raw ingredients are processed and sent out to the customer, along with toxic by-products, pollution and contaminants. This point of view is exemplified by battery systems of raising animals and wheat farms that lose several tonnes of topsoil for each tonne of harvested produce. This system relies heavily on a publicity campaign to persuade us that these pollutants and contaminants are harmless, but even if they are not, we must live with them, or die of starvation. The amount of tax payers' money being spent to grow food that is a glut on the world market, makes the latter proposition a little hard to believe.

For most of us, the word "farm" conjures up a very different picture than that of the factory. We see a country house, surrounded by fields, sheep in some and cattle In others. There are ducks on the pond, chickens in the yard and a vegetable garden near the house. On such a farm, the manure from the animals is not a waste product, but the basis of fertility in the garden and fields. The hens run In the orchard, helping to control pests. There is no waste and no pollution. The by-products of the system, animal manure and straw, are inputs for another part of the system. The produce sold removes only a small percentage of the bank of fertility, and this is cheaply replaced with unprocessed, crushed rocks, rather than expensive, manufactured fertilisers.

The sheer ecological diversity mitigates against massive pest and disease outbreaks, and the few that occur are often readily controlled by gentler approaches than the use of excessively toxic, and often persistent biocides. The bulk of output achieved is rarely equal to that of a conventional system, at least in a good year. When growing conditions are difficult, it is not unusual to see output fall dramatically on a conventional farm, but change little on the organic. One organic wheat farmer said in a radio interview, that while his neighbours were suffering from a bad drought, he hardly knew there was one.

Another point of view is food quality. Much conventionally grown wheat has declined from around 15% protein to 10% and less; organic wheat is claimed to be at the higher level. Some 10% of wheat from Australia has a cadmium content in excess of the maximum residue limit accepted as safe for human consumption. The major source of this contaminant is probably superphosphate made from phosphate rock mined from deposits high in heavy metals. Sheep and cattle kidneys routinely contain more cadmium than is safe, in some places, so their sale has been banned.

Food quality, from the supermarket's point of view, is cosmetic. Are the carrots all blemish-free and exactly 200 mm long, so that they will fit the polystyrene tray? A farm magazine article about chick peas (garbanzos) informs us that the nutritional content is irrelevant, since they are for human consumption. While the conventional grower is obsessed with the superficial, the organic grower looks to the soil for answers to problems. He, or she, realises that from the soil comes everything we eat, our clothes and our shelter. They treat it as the living organism that it is, remedy its mineral deficiencies with powdered rocks, where glacial action was too long ago to have done this, return the plant and animal residues, keep it covered as much as possible with living plants and sheltered by nearby trees. Herbicides are not used, because of an innate suspicion that, like previously "safe" chemicals, they will eventually be discovered unsafe. Scientifically informed growers are probably already aware that new research is uncovering an unlooked for side-effect of their use, trace element lock-up. Some trace elements are essential for animal and human health, some for plant health. Who wants to create a whole host of new problems in return for the solution to one problem?

Conversion to Organics

As the introduction suggested, organic growing is not the substitution of naturally occurring biodegradable insecticides for synthetic chemicals. The first step is to increase the health of the soil. This is achieved by several means. firstly, organic matter is incorporated, either by spreading a thick layer on the surface, allowing the earthworms to dig it in, or by making a compost heap. The latter option was advocated by Sir Albert Howard for a number of reasons. It accelerates the creation of humus, the breakdown product of the combination of animal manure, weeds, vegetable scraps, straw, hay, leaves, sawdust etc. It also increases the content of nitrogen, one of the many elements plants use to grow. Where animal manure is included, the compost appears to impart particular disease resistance in the plants it is used to feed.

The elevation of humus level of the soil to 5% or more makes tillage easier, reduces nutrient leaching during rain or irrigation, increases water holding capacity, and improves drainage. Aeration of the soil is improved, allowing free gas exchange with the atmosphere, a prime requisite for plant root health. In this condition, soil micro organisms go to work. Bacteria release minerals from the particles of silt, convert atmospheric nitrogen to plant food and fungi exchange phosphorus for carbohydrate with plant roots, In a mutually beneficial relationship. Add some nitrate fertiliser (or too-strong manure tea) to get the spectacular yields that conventional growers are so proud of and the whole system falls apart. That beneficial root fungus may become a pathogen. The sap stream of the plants becomes filled with free amino acids instead of whole proteins. Aphids love this and will respond eagerly to the feast you have provided them.

If you are plagued by pest and disease, keep heart. This will pass. To build pets and disease-resistance, choose older, open-pollinated varieties where possible. Most modern strains of food plant have been bred for toughness in transport, resistance to particular herbicides, response to artificial fertilisers and almost never for flavour. Mix flowers and herbs with vegetables, it might look all wrong, but it confuses the insects more than critical conventional gardeners. Add seaweed or seaweed meal to the compost. It contains a host of trace elements and nobody really knows how many are essential to your plants' health. Try to grow as many different sorts of plants as you have room for. A diverse ecology is much more resistant to pest outbreaks.


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Jonathan Sturm 1991 - 2011

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