No, fertilizer concentrations are not standardized. The formulas are
expressed in weight percentages, and vary by formula and the raw materials
used to make them up.

Shultz general purpose plant food is 20-30-20, but if you dissolved a pound
of it in a pound of water and sold it as a liquid fertilizer concentrate, it
would be labeled as 10-15-10, meaning that you would need to add twice as
much by weight, to achieve the same nutrient concentration.

As to why you'd use more outdoors than in a houseplant, in your houseplant,
100% of what you add is in the pot for the plant to absorb, while outdoors,
it becomes available to essentially an infinite amount of soil.
Fortunately, diffusion into the soil isn't so fast that it pumps the
nutrition out instantly, so some is still available for the plants that were
intentionally fed. Then there's the light level...more light=more
photosynthesis=more nutrient demand. Light intensity outdoors is much great
than that coming through a window,
--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Books, Artwork, and Lots of Free Info!

.. . . . . . . . . . .
"Tanya" wrote in message
...
Ray wrote:

Most of you are aware of the JavaScript calculator I have on my website
for
determining the concentration of nitrogen, phosphorus, and potassium in
fertilizer solutions. You simply plug in the N, P, and K values from
the
label, and the number of teaspoons per gallon you use, and it tells you
the
concentrations in ppm, plus the N, P, & K contributions to the TDS.

After a lot of discussions with the folks at Blackmore (they made the
stuff
for MSU) and Peters, I have concluded that if your fertilizer has a wide
range of minor- and trace elements in it, you can manage your feeding
regimen by simply controlling the nitrogen loading. I have, therefore,
added another calculator to that page which allows one to simply enter
the
"N" value from the fertilizer label and the desired nitrogen loading in
ppm,
and it tells you how many teaspoons to add to a gallon of water (and
milliliters per liter).

http://www.firstrays.com/fertcalc.htm

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Books, Artwork, and Lots of Free Info!

. . . . . . . . . . .

i liked the other calculator too and haven't seen this one Y.E.T.
HOWEVER,
major confusion:
MANY food / fertilizer labels state such_and_such amount (ex: 1 tsp /
gallon)
for houseplants and a larger amount for outDoors.
(e.g.: 1 TBSP per gallon)
isn't the absolute concentration the same? for powder?
aren't these supposed to be standardized (at least minimally?)
thank you
sincerely
Tanya