sometime in the recent past Korleone posted this:
Hello.

I have some simple questions about fertilizers.

For the last few days I've spent a lot of time figuring out ideal
profiles for fertilizers for indoor tomatoes.

I wrote a program that figures out how to mix seperate fertilizers
together to better match your custom fertilizer profile. Which is
great (and bloody genius), but..

.figuring out an ideal fertilizer profile for tomatoes is difficult.
Lots of info online is contradictory.

Typically, tomato fertilizers on the shelf are 3-2-5.

For instance, Phostrogen Plant Food and Chempak Tomato Food are close
to a 3-2-5, have trace elements and seem like great plant foods for
tomatoes.

But the fortnightly dose is 516ppm-328ppm-829ppm. So all at once, that
concentration is added to the soil. Why isn't that a problem?

(That was the first simple question. Here comes the second.)


Why is it better to feed a plant with emphasis on a particular
nutrient?

Isn't the plant going to take what it needs? In other words, if you
use a balance fertilizer, say, 6-6-6 at 100ppm, and the plant needs
more Potassium, couldn't you just increase the concentration of 6-6-6
to, say, 150ppm instead of changing to a fertilizer that's, say, 6-6-8?


Simply what I'm asking is: does a plant take only what it needs from
the soil, or does a plant eat everything it's given?

If the first is true, then we need only use a balanced fertilizer and
increase the ppm to suit. If the second is true, then altering the
ratio and the ppm would be necessary.

Btw, I know most of you are organic growers. This is just an exercise
for me, to figure this out. So please, you don't need to tell me of
the evils of non-organic fertilizers.




Not a word on pH. If it isn't right, nutrients can get locked up so they
aren't available to the plant at any ppm. Just 2 cents.