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nafex - Re: [NAFEX] leachy phosphorous

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  • From: Road's End Farm <organic87@frontiernet.net>
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] leachy phosphorous
  • Date: Thu, 25 Jun 2009 16:04:20 -0400


On Jun 25, 2009, at 3:32 PM, Mark Angermayer wrote:

Rivka wrote:
 
"c) during just about all of the evolutionary history of these plants humans were not applying P annually to supply them:
therefore, it's got to be made available by some process not involving human intervention."
 
That may be true, but evolution typically produces very low yields with the exclusive goal of survival of individual species.  The yields nowadays of many crops remove far more P than can be supplied without the aid of human intervention. 
 
Mark
KS

That's a very good point (though I'm not sure whether total biomass production of modern crops is different, or only production of the portion considered edible by humans). To amplify it, most of the yields in natural systems stay in the immediate area (though animals and wind do move some of them), while most of the yields in modern farming are removed from the site and sold long distances away. In any case in which the amount repeatedly removed from the field is more than it can renew for itself each year, amendments will eventually need to be brought in to replenish this amount (though nitrogen can be replaced in some cases by cover crops).

However, my main point was that P can't simply always become unavailable, with no natural mechanism to make it available again to plants. Whether that mechanism is sufficient, or even functional, in a specific farm situation is another question. But if we understood the natural function, we might be able to figure out how to better take advantage of it. -- I don't know whether it is understood, but hasn't been explained in this discussion; or whether this is one of the areas that modern soil science is still working on.



--Rivka
Finger Lakes NY; zone 5 mostly



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