by Adam Fenderson -- June 2004
Holmgren: One of the biggest limiting resources in agricultural productivity is phosphorous. It's critical to plant nutrition and animal health, and it's in limited supply. All ecosystems work to maximize to hold phosphorous and recycle it. It's one of the non-renewable mineral resources that humans have dug out of the earth at a few key places around the world in the last hundred years with the aid of fossil fuels and have spread over large areas of agricultural land. Interestingly enough, it's one of the few elements that doesn't get leeched away readily. It's been estimated that in some parts of Australia's farmland that's been intensively farmed for potatoes in a cool climate, that there's enough phosphorous tied up in the soil, locked up, for a hundred years of farming�if you could actually make it available.
Now making it available requires the work of a healthy eco-system. Because nature is used to actually breaking apart this locked up phosphorous in the form of aluminium and iron phosphate. So permaculture systems--especially tree systems, as well as forms of organic agriculture that husband the soil micro-organisms can mine back out some of that resource. That's one of the positive stories agriculture hasn't just left a legacy of toxicity and degradation, it's left a legacy of unused abundance. It's been technically difficult to get at, so it's not just like people have pointlessly thrown away fertilizers: it requires more sophisticated soil ecosystems.
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