Subject: Re: deep-rooted plants' P & K extraction?
From: [email-masked] (LodiCraig)
Date: 23 Jul 1994 20:05:04 -0400
Newsgroups: alt.sustainable.agriculture

In article <[email-masked]>, [email-masked] (Tero
Laakkonen) writes:

>i would like to know (quantitatively) what kind of potential deep-rooted
>field plants (eg vicia villosa) have to bring P & K into the surface
>layer. i would like to know if i can realistically grow other field
>plants after this plant without fertilization ... and if i can, for how
many
>years would this be feasible?

>i'm sorry if my question is simplistic but i am an outsider to this
>field.

Great question!  I wish I had the answer, but I am going to watch this
thread to see if someone else does.

As a grape grower, I am especially concerned with K.  Quite a lot is
'mined' by grape vines and we 'export' it from the field in the grapes ...
thus wine is a wonderful source of vitamin K.

In our case, P & K availablity are more a function of soil chemistry.  We
have plenty there, it just happens to release very slowly ... and adding K
in concentrated bands makes it more available.  Other things help to, like
adding Ca to 'stir things up'.

You could estimate it by getting some tissue analysis of the plants on the
specific site ... estimate the approximate dry weight of plant material
dropped each year and extrapolate a rough estimate of the amount of K and
P mined from the deep.  You may find, though, that like my situation, the
soil chemistry that makes existing K and P available to plants will far
overshadow the absolute values of those nutrients present in your soil. 

It may be helpful to post your soil types, and anything else you know
about the soil and your climate that may effect these things.

I'll be watching.

Craig, a farmer in California