Polyculture | Sustainable Farming

January 04th, 2007 | Category: Organic Gardening

Groovy Green has an excellent article on the benefits of polyculture over monoculture.

Polyculture can be defined as agriculture using multiple crops in the same space, in imitation of the diversity of natural ecosystems, and avoiding large stands of single crops, or monoculture. It includes crop rotation, multi-cropping, intercropping, companion planting, beneficial weeds, and alley cropping.

Polyculture, though it often requires more labour, has several advantages over monoculture:

The diversity of crops avoids the susceptibility of monocultures to disease. For example, a study in China reported in Nature showed that planting several varieties of rice in the same field increased yields by 89%, largely because of a dramatic (94%) decrease in the incidence of disease, which made pesticides redundant.

The greater variety of crops provides habitat for more species, increasing local biodiversity. This is one example of Reconciliation Ecology, or accommodating biodiversity within human landscapes.

Polyculture is one of the principles of permaculture.

Groovy Green has this to say about polyculture:

Growing a hundred (or even a thousand) contiguous acres of a single crop is asking for trouble. Doubly so if that crop is vegetatively propagated, since the individual plants are genetically identical, and so, identically susceptible to any pest or disease that happens to infiltrate the defenses and infect the crop. (See: Irish Potato Famine.)

Modern large scale farming, to use an extreme example, essentially has to use tons of chemical fungicides and pesticides and antibiotics, because the plants and animals have lost all of their natural resistances. And unfortunately, at this moment, it may well be the only way to feed the many billions of inhabitants of Planet Earth.

The problem is not confined to large scale commercial farming though. Even open-pollinated vegetables can have some vulnerabilities, if the genetic base is too narrow, if it has lost some ancestral resistances, or if it is offered too much external protection from pathogens. Unfortunately, if natural resistance is not tested, it is essentially bred out of the line.

Horizontal resistance is achieved by the following low-tech means:

- Growing a large, diverse, non-hybrid population
- Encouraging cross-pollination
- Not discouraging pests or diseases
- Saving seed from the best performers, even if (especially if) conditions are stressful

This is pretty much accepted as standard practice for sustainable farming as well as organic farming. You can also implement these techniques on a smaller scale in your own garden as well as by following these organic gardening techniques.