Ray,

I was using your PPM calculator yesterday. Thanks, it came in real handy.
I am used to measuring fertilizer by weight, not volume. I'm guessing that
your ppm calculator assumes the density of fertilizer (weight per volume) is
about the same for all fertilizers. Is that a good guess and if so, do you
have any feel how valid the assumption is?


Pat

First, keep in mind those calculators were developed for liquid fertilizers.

The values on a fertilizer label are in weight percentages, including the
modified ones for P & K. As water can be generally thought of as one gram
per ml, and as a milliliter is a volume measurement, the calculators work
with factors based upon grams of fertilizer per milliliter of water. As
such, they will vary depending on the minerals used to make up the
fertilizer, but I've not concerned myself with determining the degree of
difference. The mass of nutrients in solution is so small that when
measuring liquids, using the 1g/ml conversion is probably close enough.

As an example, Dyna-Gro "Grow" formula is around 18 weight percent
nutritional elements. For 100 ppm N, the calculation suggests that 1.41
ml/l is needed, so that means that a liter of solution contains:

0.18 x 1.41/1000 = 0.00025 grams of nutritional elements.

If my "concentrate" density is off by 5%, then my final solution will
contain between 0.00024 and 0.00027 grams, and insignificant difference, as
far as I'm concerned.

Obviously, those factors will vary greatly if you're using powders, and they
should be handled by weight, not volume, unless you know the bulk density of
the fertilizer powder you're using.

If you use the grams of fertilizer per liter of water calculation, and
actually weigh your fertilizer, you'll be much better off, in either case.

--

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


"Pat Brennan" wrote in message
...
Ray,

I was using your PPM calculator yesterday. Thanks, it came in real handy.
I am used to measuring fertilizer by weight, not volume. I'm guessing
that your ppm calculator assumes the density of fertilizer (weight per
volume) is about the same for all fertilizers. Is that a good guess and
if so, do you have any feel how valid the assumption is?


Pat

Pat,

You got me thinking about this one...

I was considering taking an example fertilizer and back-calculating the
makeup, throwing in the bulk densities of the components, and seeing where
that got us, but then I realized:

The bulk density of powders varies by not only what the material is, but how
finely it is ground, what shape those particles are, etc. As an example,
the bulk density of ordinary silica sand, with it's fairly uniform, quite
rounded particles, runs about 1.5 g/cc. If you have the fine particle size
silica used as a thickener in everything from paints to cosmetics to
ketchup, its bulk density is about 0.05 g/cc.

But now I'm on a quest.

I figure that most water soluble, powdered fertilizers contain more-or-less
the same chemicals, and they are probably similar in their ground properties
(there are a few exceptions), so the range of bulk densities is probably
reasonably narrow, but I'm going to do some digging and see what I can find
out...

FWIW, the bulk densities of most of the major components is about 1 g/cc,
according to some large-scale mineral suppliers I have already contacted,
suggesting that our volumetric approach might not be all that bad.

--

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


"Ray" wrote in message
...
First, keep in mind those calculators were developed for liquid
fertilizers.

The values on a fertilizer label are in weight percentages, including the
modified ones for P & K. As water can be generally thought of as one gram
per ml, and as a milliliter is a volume measurement, the calculators work
with factors based upon grams of fertilizer per milliliter of water. As
such, they will vary depending on the minerals used to make up the
fertilizer, but I've not concerned myself with determining the degree of
difference. The mass of nutrients in solution is so small that when
measuring liquids, using the 1g/ml conversion is probably close enough.

As an example, Dyna-Gro "Grow" formula is around 18 weight percent
nutritional elements. For 100 ppm N, the calculation suggests that 1.41
ml/l is needed, so that means that a liter of solution contains:

0.18 x 1.41/1000 = 0.00025 grams of nutritional elements.

If my "concentrate" density is off by 5%, then my final solution will
contain between 0.00024 and 0.00027 grams, and insignificant difference,
as far as I'm concerned.

Obviously, those factors will vary greatly if you're using powders, and
they should be handled by weight, not volume, unless you know the bulk
density of the fertilizer powder you're using.

If you use the grams of fertilizer per liter of water calculation, and
actually weigh your fertilizer, you'll be much better off, in either case.

--

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


"Pat Brennan" wrote in message
...
Ray,

I was using your PPM calculator yesterday. Thanks, it came in real
handy. I am used to measuring fertilizer by weight, not volume. I'm
guessing that your ppm calculator assumes the density of fertilizer
(weight per volume) is about the same for all fertilizers. Is that a
good guess and if so, do you have any feel how valid the assumption is?


Pat

I spent some time this morning talking to technical folks at a number of
different fertilizer companies. While having come at the answer from
multiple directions, they all pretty much concluded the same.

Areas of absolute agreement:

1) The bulk density of a fertilizer depends upon the chemical components,
their percentages, their as-ground particle sizes, how much moisture they
have absorbed, et cetera.

2) Because of those issues, the bulk density of a ground product will vary
not only between products, but even lot-to-lot for an individual product, or
how long it traveled to get to you from the manufacturer (packing in
transit).

3) Fertilizers should be metered by weight, not by volume.

While that's fine for someone like me who used several pounds to make up 5
gallons of concentrate to be metered by a device into the water stream, it
is unlikely that most hobby growers have the capability of measuring out a
gram or two or a quarter of an ounce of powder to make up a gallon of
fertilizer.

There were basically three responses to that:

1) Use "kitchen conversions" gleaned from websites and cookbooks. That
is, a level 1/2 teaspoon is 2.4 g, a level teaspoon is 5 g, and a level
tablespoon is 14 grams. Volumetrically, if we "standardize" on the
teaspoon, they would be 2.5 g, 5 g, and 15 g, but that's pretty close,
either way. As a teaspoon is 4.9289 ml, 5 g gives us a density of 1.014
g/ml.

2) Use an average bulk density of 60 pounds per cubic foot, That's
0.961g/ml.

3) Use a standardized (but admittedly inaccurate) conversion for nitrogen
concentration per teaspoon: one teaspoon of powder to make up a gallon of
fertilizer contributes 12.5 ppm N for each percent in the formula, i.e.:
one teaspoon of a 20-20-20 fertilizer used in a gallon of solution will have
250 ppm N. If I back-calculate that, I get an apparent bulk density of 0.95
g/ml.

Considering the inaccuracy in measuring powders ("is that level or slightly
heaped?"), any other inaccuracies coming from metering devices like hose-end
sprayers or siphons, etc., and the very small concentrations of dissolved
minerals in out fertilizer solutions, it looks like a straight 1 g/ml
density is reasonable for both powders and liquids!

--

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


"Ray" wrote in message
...
Pat,

You got me thinking about this one...

I was considering taking an example fertilizer and back-calculating the
makeup, throwing in the bulk densities of the components, and seeing where
that got us, but then I realized:

The bulk density of powders varies by not only what the material is, but
how finely it is ground, what shape those particles are, etc. As an
example, the bulk density of ordinary silica sand, with it's fairly
uniform, quite rounded particles, runs about 1.5 g/cc. If you have the
fine particle size silica used as a thickener in everything from paints to
cosmetics to ketchup, its bulk density is about 0.05 g/cc.

But now I'm on a quest.

I figure that most water soluble, powdered fertilizers contain
more-or-less the same chemicals, and they are probably similar in their
ground properties (there are a few exceptions), so the range of bulk
densities is probably reasonably narrow, but I'm going to do some digging
and see what I can find out...

FWIW, the bulk densities of most of the major components is about 1 g/cc,
according to some large-scale mineral suppliers I have already contacted,
suggesting that our volumetric approach might not be all that bad.

--

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


"Ray" wrote in message
...
First, keep in mind those calculators were developed for liquid
fertilizers.

The values on a fertilizer label are in weight percentages, including the
modified ones for P & K. As water can be generally thought of as one
gram per ml, and as a milliliter is a volume measurement, the calculators
work with factors based upon grams of fertilizer per milliliter of water.
As such, they will vary depending on the minerals used to make up the
fertilizer, but I've not concerned myself with determining the degree of
difference. The mass of nutrients in solution is so small that when
measuring liquids, using the 1g/ml conversion is probably close enough.

As an example, Dyna-Gro "Grow" formula is around 18 weight percent
nutritional elements. For 100 ppm N, the calculation suggests that 1.41
ml/l is needed, so that means that a liter of solution contains:

0.18 x 1.41/1000 = 0.00025 grams of nutritional elements.

If my "concentrate" density is off by 5%, then my final solution will
contain between 0.00024 and 0.00027 grams, and insignificant difference,
as far as I'm concerned.

Obviously, those factors will vary greatly if you're using powders, and
they should be handled by weight, not volume, unless you know the bulk
density of the fertilizer powder you're using.

If you use the grams of fertilizer per liter of water calculation, and
actually weigh your fertilizer, you'll be much better off, in either
case.

--

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


"Pat Brennan" wrote in message
...
Ray,

I was using your PPM calculator yesterday. Thanks, it came in real
handy. I am used to measuring fertilizer by weight, not volume. I'm
guessing that your ppm calculator assumes the density of fertilizer
(weight per volume) is about the same for all fertilizers. Is that a
good guess and if so, do you have any feel how valid the assumption is?


Pat

Ray,

When the computer said I was to use .49 teaspoons per gallon, who was I to
question.

I have weighed some of the stuff around here and here are the results.

..78 g/ml Peters 20-20-20 powder
..84 g/ml Excel 15-5-15 cal mag powder
1.05 g/ml 15.5-0-0 calcium nitrate powder
1.12 g/ml 13.75-0-46 potassium nitrate prill
1.18 g/ml Dyna-Grow 7-7-7 liquid
1.21 g/ml Jacks 10-30-20 powder
1.52 g/ml 0-54-0 phosphoric acid liquid

Pat


"Ray" wrote in message
...
Pat,

You got me thinking about this one...

I was considering taking an example fertilizer and back-calculating the
makeup, throwing in the bulk densities of the components, and seeing where
that got us, but then I realized:

The bulk density of powders varies by not only what the material is, but
how finely it is ground, what shape those particles are, etc. As an
example, the bulk density of ordinary silica sand, with it's fairly
uniform, quite rounded particles, runs about 1.5 g/cc. If you have the
fine particle size silica used as a thickener in everything from paints to
cosmetics to ketchup, its bulk density is about 0.05 g/cc.

But now I'm on a quest.

I figure that most water soluble, powdered fertilizers contain
more-or-less the same chemicals, and they are probably similar in their
ground properties (there are a few exceptions), so the range of bulk
densities is probably reasonably narrow, but I'm going to do some digging
and see what I can find out...

FWIW, the bulk densities of most of the major components is about 1 g/cc,
according to some large-scale mineral suppliers I have already contacted,
suggesting that our volumetric approach might not be all that bad.

--

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


"Ray" wrote in message
...
First, keep in mind those calculators were developed for liquid
fertilizers.

The values on a fertilizer label are in weight percentages, including the
modified ones for P & K. As water can be generally thought of as one
gram per ml, and as a milliliter is a volume measurement, the calculators
work with factors based upon grams of fertilizer per milliliter of water.
As such, they will vary depending on the minerals used to make up the
fertilizer, but I've not concerned myself with determining the degree of
difference. The mass of nutrients in solution is so small that when
measuring liquids, using the 1g/ml conversion is probably close enough.

As an example, Dyna-Gro "Grow" formula is around 18 weight percent
nutritional elements. For 100 ppm N, the calculation suggests that 1.41
ml/l is needed, so that means that a liter of solution contains:

0.18 x 1.41/1000 = 0.00025 grams of nutritional elements.

If my "concentrate" density is off by 5%, then my final solution will
contain between 0.00024 and 0.00027 grams, and insignificant difference,
as far as I'm concerned.

Obviously, those factors will vary greatly if you're using powders, and
they should be handled by weight, not volume, unless you know the bulk
density of the fertilizer powder you're using.

If you use the grams of fertilizer per liter of water calculation, and
actually weigh your fertilizer, you'll be much better off, in either
case.

--

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


"Pat Brennan" wrote in message
...
Ray,

I was using your PPM calculator yesterday. Thanks, it came in real
handy. I am used to measuring fertilizer by weight, not volume. I'm
guessing that your ppm calculator assumes the density of fertilizer
(weight per volume) is about the same for all fertilizers. Is that a
good guess and if so, do you have any feel how valid the assumption is?


Pat

I know part of the problem with weighing powders is just how much moisture
they absorb, as that affects both the apparent weight and how the powders
pack, which both affect density, and that changes over time.

By the way, I put the summary of my "diggings" in a page on my website so I
won't lose the info:

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

--

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


"Pat Brennan" wrote in message
...
Ray,

When the computer said I was to use .49 teaspoons per gallon, who was I to
question.

I have weighed some of the stuff around here and here are the results.

.78 g/ml Peters 20-20-20 powder
.84 g/ml Excel 15-5-15 cal mag powder
1.05 g/ml 15.5-0-0 calcium nitrate powder
1.12 g/ml 13.75-0-46 potassium nitrate prill
1.18 g/ml Dyna-Grow 7-7-7 liquid
1.21 g/ml Jacks 10-30-20 powder
1.52 g/ml 0-54-0 phosphoric acid liquid

Pat


"Ray" wrote in message
...
Pat,

You got me thinking about this one...

I was considering taking an example fertilizer and back-calculating the
makeup, throwing in the bulk densities of the components, and seeing
where that got us, but then I realized:

The bulk density of powders varies by not only what the material is, but
how finely it is ground, what shape those particles are, etc. As an
example, the bulk density of ordinary silica sand, with it's fairly
uniform, quite rounded particles, runs about 1.5 g/cc. If you have the
fine particle size silica used as a thickener in everything from paints
to cosmetics to ketchup, its bulk density is about 0.05 g/cc.

But now I'm on a quest.

I figure that most water soluble, powdered fertilizers contain
more-or-less the same chemicals, and they are probably similar in their
ground properties (there are a few exceptions), so the range of bulk
densities is probably reasonably narrow, but I'm going to do some digging
and see what I can find out...

FWIW, the bulk densities of most of the major components is about 1 g/cc,
according to some large-scale mineral suppliers I have already contacted,
suggesting that our volumetric approach might not be all that bad.

--

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


"Ray" wrote in message
...
First, keep in mind those calculators were developed for liquid
fertilizers.

The values on a fertilizer label are in weight percentages, including
the modified ones for P & K. As water can be generally thought of as
one gram per ml, and as a milliliter is a volume measurement, the
calculators work with factors based upon grams of fertilizer per
milliliter of water. As such, they will vary depending on the minerals
used to make up the fertilizer, but I've not concerned myself with
determining the degree of difference. The mass of nutrients in solution
is so small that when measuring liquids, using the 1g/ml conversion is
probably close enough.

As an example, Dyna-Gro "Grow" formula is around 18 weight percent
nutritional elements. For 100 ppm N, the calculation suggests that 1.41
ml/l is needed, so that means that a liter of solution contains:

0.18 x 1.41/1000 = 0.00025 grams of nutritional elements.

If my "concentrate" density is off by 5%, then my final solution will
contain between 0.00024 and 0.00027 grams, and insignificant difference,
as far as I'm concerned.

Obviously, those factors will vary greatly if you're using powders, and
they should be handled by weight, not volume, unless you know the bulk
density of the fertilizer powder you're using.

If you use the grams of fertilizer per liter of water calculation, and
actually weigh your fertilizer, you'll be much better off, in either
case.

--

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


"Pat Brennan" wrote in message
...
Ray,

I was using your PPM calculator yesterday. Thanks, it came in real
handy. I am used to measuring fertilizer by weight, not volume. I'm
guessing that your ppm calculator assumes the density of fertilizer
(weight per volume) is about the same for all fertilizers. Is that a
good guess and if so, do you have any feel how valid the assumption is?


Pat