Image credit: Susty
My post on why soil is not dirt, and to a lesser degree my subsequent backtracking on why dirt may be soil after all, drew a passionate and divided response. It seems many folks really do care about the dirt/soil we depend on after all. But as email responses from friends and fellow soil geeks keep trickling in, one friend brought up an interesting analogy. Maybe conventional "soil based" agriculture isn't even soil based at all. Maybe it's just hydroponics. I've long been aware that many people, many farmers included, consider soil as an inert substance that is used for keeping plants upright. The real nutrients coming from sprays and other products applied to that soil. But I hadn't thought of the full implications of that attitude—that conventional agriculture often has more in common with hydroponics and other soil-less growing systems that supply all plant nutrients in the form of plant food. But what does it matter?
Aside from the obvious biodiversity and carbon sequestration implications—not to mention storm-water buffering and other 'services' provided by healthy soil—some people claim that conventional and hydroponically grown foods are lacking the benefit of the countless microorganisms found in soil.
The idea comes in another article on the wonderfully named PermacultureAndSanity.com discussing the idea of soil as opposed to lifeless dirt sent to me by a friend. They make some pretty strong claims that nutrient values are indeed decreasing due to unhealthy soils:
"Our nation's agricultural areas long ago became devoid of 'soil'--our food is now hydroponically-grown (i.e., fed by solutions of petro-chemicals in water). In response to the removal of micronutrients from our farms and the food they produce, the USDA--rather than directly addressing the cause of this crisis (dead 'soil' due to our system's failure to return organic wastes to farmlands)--simply lowered vegetables' stated nutritional value to keep in line with the impoverished realities of modern chemical farming. "
Sadly, no reference is given. But it's a provocative statement. Of course there have been plenty of headlines on Treehugger and elsewhere about some studies showing organic foods have no nutritional benefit over non-organic, and others who claim that soil-less agriculture can never be organic because of the lack of microorganisms, so the debate remains open. What interests me as we start talking about micronutrients and trace elements in the soil, is really how much do we know about their effects on plants—and the subsequent benefits, or indeed negative effects, on humans.
It seems obvious to me that if plant nutrition is about much more than simple ratios of nitrogen, potassium and phosphorous, then so too that will have an effect on the humans who ingest them. But I'd love to hear from folks who know more. A quick search of "hydroponics and nutrition" gives me plenty of advice on how to grow good marijuana (remembering of course that marijuana can be a gateway drug to farming)—but very little on the impact of hydroponic techniques on the food we eat.
If anyone has any references on this, I would love to see them.