North American Fruit Explorers mailing list at ibiblio

[Road's End Farm <organic87@frontiernet.net>]

It's my understanding that some crops, in particular buckwheat, are capable of taking up P from the soil even when it's in a form not available to most plants; and that using such plants as a cover crop (tilling them back in) can then provide that P in a form available to other plants.

I did a very fast search and found a number of references to this; one, though it didn't go into any detail, sounded as if the buckwheat might be doing this along with fungal associations, though I hadn't heard of this aspect before. No time right now to look into it further.

--Rivka
Finger Lakes NY; zone 5 mostly

On Jun 20, 2009, at 11:36 AM, Alan Haigh wrote:

> Richard posted, "my county agents office has always taught that P was rather immobile. Now that doesn;t say anything about whether it is available for plant uptake or not. If very immobile, I would question its availability to plants to absorb it".
>  
> My answer is that it is estimated that on average, 15% of applied P is taken up by plants before becomming immobile in commercial agricultural application.  I've no idea if there is a wide range to that stat in relation to various crops. 
>  
> For trees it used to be suggested that P be applied into holes made by a crowbar to get P close to the roots.  Seems this wasn't actually helpful and the practice is no longer recommended.  I'm aware of no research that indicates an advantage to any kind of deep-root fertilization and at one point I made an effort to find such research.  But that was before the age of computors- google deep root fertilization, anyone?   
>  
> Tree spikes are a remnant of this misconception about trying to get fertilizer close to the roots. 
>  
> The greatest benefit of mychorizal associations is the ability of the fungi to deliver adequate P to trees in soils with deficient amounts in soluble form.  This has been discussed here in detail in recent exchanges.
>