Hello
all,
A
lot of discussion has been going on on rec.gardens.orchids lately concerning our
“RAIN MIX” and the amount to use per litre.
I
thought the group here would benefit as well from our answer we typed as a
response to some questions received directly.
The
recommended dosage for RAIN MIX is as follows:
0,5
g/l = ~ 520 µS/cm = ~ pH 6,1
A
little note concerning TDS measurements:
A
TDS meter measures the conductivity of a saltsolution and gives, through a
conversionfactor, a reading of the amount of disolved salts expressed in ppm.
Most
TDS meters have a conversionfactor of 0,50 and are therefore correct for
measuring NaCl-saltsolution.
0,01
mole/l solution of NaCl contains 585 mg NaCl/l and gives an EC value of 1155
µS/cm.
585
mg NaCl/l = 585 ppm TDS
585 /
1155 = 0,506
Unfortunately
we are not measuring a saltsolution of NaCl, but a NPK fertilizer saltsolution.
Every salt in that mixture has a different conductivity.
In
a mix of salts one must take into account the contribution of conductivity of
each individual ion and also the interactions between these ions. Therefore one
must use a different conversionfactor for each different combination.
On
regular TDS meters the conversionfactor cannot be adjusted/changed, on more
expensive, professional meters this can however be done.
Test:
Put
1000 mg of RAIN MIX in beaker of 1000 ml. Add demineralised water and shake
until all salts are disolved.
Measure
the amount of salt with your TDS meter. You would expect to obtain 1000 ppm
TDS, however this is not the case!
For
this reason in professional horticulture µS of mS is used and not TDS.
Likewise
the amount of N is expressed in mmole/l and not ppm.
How
much ppm N does a solution contain with 0,5 gr RAIN MIX / liter?
-
NPK RAIN MIX = 13-3-15
-
amount of N = 13%
-
130 g N per kilo RAIN MIX
-
per 0,5 g RAIN MIX you have 130 g / 1000 g * 0,5 g = 0,065 g or 65 mg N
present
-
this 65 mg N is in 1 l of water = 1000 ml = 1000 gr or 1000000 mg water
-
65 mg/ 1000000 mg = 65 ppm N
In
order to give you extra information have a look at the following (source: http://los.lon.imag.net/MiscFiles/fert1.htm
)
With
our recommended dosage (0,5 g/l to obtain a conductivity of 520 µS/cm) we are
closer to the 50 ppm N in the below charts to make it easier for you all.
Our
recommended dosage caters for all orchids be they salt sensitive plants like
Disa, Pleurothallids in general over to Paphiopedilums to the really big eaters
like Cattleya and Cymbidium and requires NO flushing with pure water.
Hence our dosage is a good value for all type of orchids and has been tested
for over 2 years on our orchids (no exclusion) and the mixed orchid collections
of a few selected orchid amateurs!
If
you look at the 125 ppm N column, recommended by a US grower, than you will see
that the conductivity is 1000 µS/cm… this means you will run into
problems with salt sensitive orchids and you MAY need to flush with pure water
every x time!
A
complete waste of fertilizer… and money ;-)
If
you cannot see the below charts properly then please visit the page mentioned
above and go the section on the 13-3-15 fertilizer!
EC chart
|
ppm N |
50 |
100 |
125 |
150 |
200 |
|
EC |
0.4 |
0.8 |
1.0 |
1.2 |
1.6 |
Mixing Instructions
|
|
50 ppm N |
100 ppm N |
125 ppm N |
150 ppm N |
200 ppm N |
|
Per U.S. gallon of fertilizer |
0.05 oz. (1.4 grams) |
0.10 oz. (2.8 grams) |
0.12 oz. (3.6 grams) |
0.15 oz. (4.3 grams) |
0.20 oz. (5.7 grams) |
|
Per U.S. gallon of stock solution for 1:15
injector |
0.7 oz. (21 grams) |
1.5 oz. (42 grams) |
1.9 oz. (54 grams) |
2.3 oz. (65 grams) |
3.0 oz. (86 grams) |
|
Per U.S. gallon of stock solution for
1:100 injector |
4.9 oz. (140 grams) |
9.9 oz. (280 grams) |
12.7 oz. (360 grams) |
15.1 oz. (430 grams) |
20.0 oz. (570 grams) |
Mixing Instructions -Imperial Gallon
|
|
50 ppm N |
100 ppm N |
125 ppm N |
150 ppm N |
200 ppm N |
|
Per Imp. gallon of fertilizer |
0.06 oz. (1.68 grams) (0.299 tsp.) |
0.12 oz. (3.36 grams) (0.597 tsp.) |
0.14 oz. (4.32 grams) (0.768 tsp.) |
0.18 oz. (5.16 grams) (0.917 tsp.) |
0.24 oz. (6.9 grams) (1.218 tsp.) |
|
Per Imp. gallon of stock solution for 1:15
injector |
0.84 oz. (25.2 grams) (4.48 tsp.) |
1.8 oz. (50.4 grams) (8.97 tsp.) |
2.28 oz. (64.9 grams) (11.53 tsp.) |
2.76 oz. (78.1 grams) (13.88 tsp.) |
3.60 oz. (103 grams) (18.36 tsp.) |
|
Per Imp. gallon of stock solution for
1:100 injector |
5.9 oz. (168 grams) (29.89 tsp.) |
11.89 oz. (336 grams) 59.78 tsp.) |
15.25 oz. (432 grams) (76.86 tsp.) |
18.13 oz. (516 grams) (91.80 tsp.) |
24.02 oz. (685 grams) (121.7 tsp.) |
kind
regards,
Kenneth.
Akerne
Orchids
Laarsebeekdreef 4,
B-2900 Schoten, Belgium
tel. +32 (0)3 651 40
36 fax +32 (0)3 653 06 76
See us at the
following shows and events in 2009:
·
Gentse Orchideeėndagen, Ghent, Belgium
(October 9-11)
Looking for orchid
books and magazines? Visit www.orchidbooks.eu