First of all, TDS meters are rarely correct. I have two, and at a known
125 ppm N solution of the Greencare MSU RO formula, one tells me the TDS
is 475, the other 600 ppm. How are we to trust either of them for
absolute readings? Here’s a bit from my “EC & TDS” article:

A TDS meter is really just an electrical conductivity (EC) meter that
has a built-in conversion factor that displays the output in parts per
million (ppm) of total dissolved solids (TDS). The trouble is that the
relationship between the conductivity of a solution and its content
varies not only by the concentration of the dissolved ions, but is also
based upon the charge and mobility of the dissolved ionic species.
As a very simplified explanation of that, imagine a small ion and a
large ion having the same electrical charge. The small ion will find it
easier to move in the solution, so "conducts" that charge faster, so
gives a higher EC for the same concentration (TDS) in the solution.
Likewise, if two ions have the same size, but one has a higher charge
than the other, it too will show a higher EC.
A commercial fertilizer can be made up of dozens of different chemicals,
each of which ionizes and contributes to the EC of the solution, and
different brands of fertilizer can use different chemicals to make up
the total formula. With all of that variability, how can a single
"constant" conversion factor be valid?

That said, as you recognize, my online calculator only gives the ppm of
the N, P, & K.

If you use the Greencare published chemistry, and calculate the
contribution of the cations only, for 125 ppm N, the calculated TDS is
for N+P+K is 265 ppm, and adding the minor elements brings the total up
to about 355 ppm. However, we know that some of the anionic components
contribute to the TDS, but which do and which don’t? Also, some
fertilizer minerals have chemically-bound water in them, so when
dissolved that water comes free but does not contribute to the
conductivity or dissolved solids content.

Let’s look at it from the other end of the spectrum: according to the
Greencare label, one must add 3.55g of powder to a US gallon of pure
water to attain the 125 ppm N level. As a part-per-million is a
milligram per kilogram, and a US gallon is 3.785 liters @ 1 kg/L, for
125 ppm N, we are actually adding 3550mg/3.785kg or 938 ppm of solids.

So now we have a calculated cation contribution of 355 ppm at one end,
and a gross contribution of 938 ppm at the other. The REAL answer is
somewhere in between, but I’ll be damned if I have any idea what it is,
and I will not trust ANY TDS meter to tell me a true level anyway.
(With the exception of orchid growers, professional nurserymen rely on
EC of the solution, as it is directly measurable.)

Here’s the best advice you can get:

1) Trust the manufacturer.
2) Know your units.
3) Mix the recommended amount.
4) Don’t fret any longer.

If you want to use your TDS meter, do as I, and only use it as a guide.
Using 1, 2, & 3 above, I measure the TDS with one of my meters – let’s
use the 600 one in this example – and from then on, if I check my
solution and it’s between 550 and 650, I’m happy. The actual number is
meaningless, but it does allow me to measure repeatability.

Can we move on now, please?

Ray Barkalow - First Rays LLC - http://www.firstrays.com
www.firstrays.com
Orchid Plants, Supplies, Equipment, Books
Artwork, Free Services & Lots of Info!

From: keith kent ]
Posted At: Tuesday, September 01, 2009 5:02 AM
Posted To: rec.gardens.orchids
Conversation: Jungle Feed
Subject: Jungle Feed

Sorry Ray , i am getting on my own nerves now !!
Your calculator & MSU comes out at 0.73 teaspoons per gallon or 0.95 m/l
per litre to achieve 125 ppm N.

This seems high still as when i added 0.75 teaspoons per gallon the TDS
was approx 650 ppm why ? as the calculator says it should be 258 ppm ,i
no this doesn`t include the other elements ,but surely they don`t add up
to 392 ppm
This is using RO @ 6ppm
Or is this TDS usually about right ?
I will try again 0.73 in a gallon again and see what i get
Thanks for the below i have printed it off & Cheers
Keith
"Ray B" wrote in message
news:000c01ca2a7a$091888e0$0201a8c0@fro...
Keith,

A US gallon is 3.785 liters
A US teaspoon is 4.93 milliliters

An Imperial gallon is 4.546 liters
An Imperial teaspoon is 5.92 milliliters

1 US teaspoon per US gallon is 4.93ml/3.785L = 1.302 ml/L

1 Imperial teaspoon per Imperial gallon is 5.92ml/4.546L = 1.302ml/L

The ratio being identical means that 10 divided by the %N gives you the
teaspoons per gallon to use for 125 ppm N, whether US or Imperial units.

As you put one Imperial teaspoon in an Imperial gallon, you used
1/0.75=1.333, or one-third more than necessary, meaning that the
solution you now have is about 125 x 1.333=167 ppm N, so all you have to
do is dilute it to ¾ of its current concentration for use. You could
take a quart of solution out and replace it with a quart of water, or if
your mixing container is large enough, add a quart plus a cup of water
to the gallon.

Ray Barkalow - First Rays LLC - http://www.firstrays.com
www.firstrays.com
Orchid Plants, Supplies, Equipment, Books
Artwork, Free Services & Lots of Info!

From: keith kent ]
Posted At: Monday, August 31, 2009 2:32 PM
Posted To: rec.gardens.orchids
Conversation: Jungle Feed
Subject: Jungle Feed

Ray is it as simple as converting 0.75 us teaspoon to uk teaspoon which
is 1.0408427308 ( which is as good as 1 teaspoon yeh ?) then add this to
a uk Gallon which is 4.5 UK litres
What do you think ?,if i can get this right from the start then it will
be easy from here .Phew !
Keith
"keith kent" wrote in message
...
Hi RAY ,i am using a online conversion would you convert US gallon dry
as the feed is powder form ?
Thanks Keith
"Ray B" wrote in message
news:000001ca2a33$5dd8fa00$0201a8c0@fro...
You are correct that you would add 1ml of a 13%N fertilizer to one liter
(litre) of water. I’ll leave the conversion to imperial gallons to you.

Ray Barkalow - First Rays LLC - http://www.firstrays.com
www.firstrays.com
Orchid Plants, Supplies, Equipment, Books
Artwork, Free Services & Lots of Info!

From: keith kent ]
Posted At: Sunday, August 30, 2009 4:24 PM
Posted To: rec.gardens.orchids
Conversation: Jungle Feed
Subject: Jungle Feed

Hi Ray , for ml/L msu is 13 % N divide x 13 is obviously 1 ml ? is this
per litre so it is 4.5 ml per gallon water? it surely cannot be 1 ml a
gallon .
Cheers Keith
"Ray B" wrote in message
news:000401ca2115$50f47bb0$0201a8c0@fro...
What I have learned is that most professional growers (not just
orchids), control their feeding by managing the ppm N in the solution,
and letting the rest of the nutrients “tag along” in the ratios of the
preferred formula.

I shoot for 125 ppm N in my fertilizer solution at all times. It’s easy
to determine the amount to use – just divide 10 by the %N on the label,
and the result is teaspoons to add per gallon. For you sophisticated,
metricated folks, divide 13 by the %N to get the ml/L.

Ray Barkalow - First Rays LLC - http://www.firstrays.com
www.firstrays.com
Orchid Plants, Supplies, Equipment, Books
Artwork, Free Services & Lots of Info!

From: keith kent ]
Posted At: Wednesday, August 19, 2009 12:11 PM
Posted To: rec.gardens.orchids
Conversation: Jungle Feed
Subject: Jungle Feed

Thanks for that Ray , i did see the orchidboard post after doing a
search.
I am going to buy the Akerne orchids feed which is basically the MSU i
think http://www.akerne-orchids.com/index.htm as it is the only one
available in the EU .
As the feed is 13 -3- 15 does this mean that less feed will be required
compared to the 1-0-1 .
If so this is just what i am looking for ,as i mix up at 160lts a time
sometimes and liquid feeds ,i just use too much of the stuff even to get
the mix to 350ppm .
Regards Keith
"Ray B" wrote in message
news:000001ca2000$023fe0b0$0202fea9@fro...
Dilute it about 12:1 or 13:1
12.8/12=1.07
4.8/12=0.4
14.5/12=1.21
Rounding to the nearest whole number, that's 1-0-1
Ray Barkalow - First Rays LLC - www.firstrays.com
Plants, Supplies, Equipment, Books, Artwork
Free Services & Lots of Info!

-----Original Message-----
From: keith kent ]
Posted At: Monday, August 17, 2009 6:33 PM
Posted To: rec.gardens.orchids
Conversation: Jungle Feed
Subject: Jungle Feed
Hi , Any thoughts on Jungle feed and can anyone point me in the
direction to
finding out what is in jungle feed ?
It is 1-0-1 , i have found out it is from a stock solution of 12.8- 4.8
-
14.5 so how do they get 1-0-1 ?
Regards Keith