[permaculture] food forest productivity
raincascadia at yahoo.com
Wed Mar 11 13:48:00 EDT 2009
The following applies to a complete diet in a Mediterranean climate. If you are only wanting what is usually (in the US) referred to as "produce," then the area would be much smaller. Chestnuts are often treated as a vegetable, but most nuts and legumes are treated as grains, which are the staple of most people's diets. Since grain is so important as food and grain cultivation takes up so much space and is so unsustainable, we should be trying to grow these, or substitutes for these, as well as fruits and vegetables. On the other hand, fruits and vegetables require more fossil fuel for shipping, due to their weight, lose more vitamins in transport, and cost more, so it is probably a good idea to start with these.
My friend was growing enough food for himself and his small son on 4000 square feet, following the recommendations of John Jeavons, in northern California. He spent a lot of time weeding, due to the sunlight that was being wasted by the short annual plants he was growing. We speculated that yields would be higher if food trees and other perennials were integrated into the garden, requiring less space to feed the same number of people.
The amount of food a given area is able to produce is dependent on many factors: the fertility of the soil, the amount of irrigation water available, the climate (particularly the length of the growing season for the intended crops), the species mix, the amount of work put into it, and the willingness or ability of the people eating from the garden to eat what is produced. You also need to determine whether you are measuring yield in pounds of food, calories, or dollars. If you take average production numbers for orchard monocultures of the species you are interested in as your baseline, this will give you a yield below that of any food forest you could design. Many nut trees can produce at levels similar to grain crops. I haven't done much research on it, but I feel confident that most fruit trees outcompete most annual vegetables. Root crops are pretty much the only ones that trees have a hard time comparing to, with potatoes being the miracle crop
(and these can even produce in the shade of a food forest). Root crops substantially reduce the area required to grow food for a specified number of people. These can be grown in the margins and open spots within food forests, if necessary.
So, if you included a diverse number of species that could produce a rounded diet, I would guess that 4000 square feet per person is probably a good place to start as an estimate. However, on a small scale, it might be difficult to grow enough species to produce a rounded diet, just because of the size of most trees. I would love to hear of any results that you come up with.
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