18-07-2003, 07:02 PM
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Problems with size of fruits.
(Pat Kiewicz) wrote in message ...
simy1 said:
crops,
really? I know you are one of the most knowledgeable posters here, but
from my irregular readings I was under the impression that K matters
with fruits and P with roots (and N with greens). Indeed the USDA
nutrient profiles show that P is higher in roots (and potatoes, and
seeds, like nuts or corn) and K in fruits (including of course
tomatoes and squashes).
When I started growing in my Plymouth garden, I hadn't done a soil test
but immediately realized something was wrong. My root crops were horrible;
my corn fell over. Tomatoes, peppers, and squash grew fine.
In the fall, I had a soil test done. My native soil was high in P and abysmally
low in K. While P might be important for new root growth (and thus found in
abundance in 'transplant fertilizer' formulations, K is essential for strength and
expansion of roots.
FWIW, the quick summary on hgtv's website pretty much agrees with what
I have learned:
'Nitrogen is essential for leaf growth and green leaves. Phosphorus is good for
flower and fruit development, and potassium helps to maintain strong roots.'
A Canadian website had a more thorough summary:
Nitrogen: Promotes leafy growth and green colour; organic sources are blood meal,
fishmeal
Phosphorus: Aids root health and seed development; organic sources are bone meal,
rock phosphates
Potassium: For strong stems and roots, proper water balance and disease
resistance; organic sources are kelp and wood ash.
OK, so P and K are both "structural". That much I knew because I knew
that wood chips typically have the same (about 200 ppm) P and K
content. But on my own I had also computed that the K taken out of a
given bed every year was close to the K supply in that bed. Here goes:
assume a bed, 1ftX4ftX20ft=80 cft (some 7 Tons of soil, assuming good
organic content). at 100ppm (fertile soil), that is 700 g of K. One
Big Boy tomato is 0.7 g K. Harvesting 1000 tomatoes from that bed will
completely exhaust the supply (that could be 3 or 4 summers).
Ultimately I figured that N (for greens) and K (for fruits) need to be
resupplied continuously (I do it every two years). Not so for P, since
the P content of crops is much lower (or rather, my underground crops
are a lot less than my aerial crops).
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