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From tigereyes@dclink.com Wed Aug 7 20:51:42 1996
Subject: <none>
To: ahicks@mailhost.nmt.edu
<<< This message is part 2 of a previous message >>>
also the proportions of the various salts that make up the total. All of
this information is readily available from the local water authority and the
results are given as Parts per Million (PPM)=(milligrams per litre (mgm.L).
Providing its members with this information should be a prime function of an
orchid society. In many areas, the water is very hard, meaning that it has a
high content of salts most often of Calcium and Magnesium and in the form
of carbonate. If one is forced to use this water, it may be that the water
supply already contains a sufficiently high level of these two salts for
orchids and the further addition of them in the fertilizer is not necessary
and could be toxic. Needless to say with a low salt content in the water to
start with you are able to have complete control of what the plants receive.
FERTILIZER:
We are slowly ascertaining the fertilizer needs of orchid plants,
although
there are many on which we do not yet have certain information. All plants
need Hydrogen, Oxygen and Carbon, as well as 12 or 14 other nutrients. They
obtain the first three from the atmosphere, but the other nutrients are
largely absorbed by the roots. Table 3 shows in PPM at an EC of 600 uS the
macro nutrient levels used These figures are given assuming the natural
water supply level to be zero.
The problem in supplying all of the nutrients is that if the Calcium
of
Calcium Nitrate, and the Sulphate, of Magnesium Sulphate meet in a
concentrated solution, Calcium Sulphate will rapidly precipitate out.
Hence, it is important that these salts only come in contact when they are
diluted so that this reaction is slowed. ( The commonly available
fertilizers such as 20-20-20 and 30-10-10 contain neither Magnesium Sulphate
nor Calcium, and thus are incomplete and, by themselves, are unsuitable for
hydroponic growing.) Thus, the salts may be divided into two groups, the
group containing the Calcium (usually Calcium Nitrate), and the remaining
salts including the Magnesium Sulphate. These salts may be put together
either by:
1. diluting them in a suitably large volume of water to give the EC
required and then using a pump to water the plants.
2. diluting concentrated solutions of the two groups of salts with
in-line
injectors in the watering mechanism. Two Dosmatic units may be used in
series and they give accurate dilutions at varying pressures. We use ours at
a dilution of 1/100. Two Hozon units may be used in parallel but the EC at
the nozzle will vary according to the water pressure, making it vital that
the EC of the final outflow be monitored. For example, raising the end of
the nozzle 4 or 5' (1.5 m.) may result in a decrease of fertilizer
concentration of 30 or 40 %.
Table 4 shows the tentative EC values suggested for a number of commonly
grown orchids.
pH:
Perlite is neutral and therefore the fertilizer solution determines the pH.
The pH may be measured by a meter similar to the EC meter (same source)
although it requires more frequent calibration. The pH meter also corrects
for temperature even though the reading is only minimally affected by the
temperature of the solution.
Our management of fertilizing at present consists of the use of one
part
Calcium Nitrate by weight and two parts of 7-11-27 (PLANT PROD) (Peters
5-11-26 would probably be equally good). These are diluted in-line as
described above and applied at an EC of about 550 uS at each watering and
at ambient temperature. During the ensuing week, the EC usually rises to a
little over 600 uS in the pots, but less in the beds. A careful check on
the EC of random pots is made to make sure that the EC does not go over
600uS. Our water supply has an EC of 10 to 30 uS and a pH of 6.4. Using
the above fertilizers at an EC of 550 the nozzle pH is 5.7 to 5.8. The pH
goes down in the reservoir water over a period of months, and a similar
fall occurs in other media and with other fertilizers. Plants seem to
thrive even with a pH as low as 4. We currently have this observation under
review.
A small quantity of fertilizer may be made up by thoroughly dissolving 1/2
tsp.(2.5 ml.) of 7-11-27 and 1/3 tsp(2 ml.) of calcium nitrate in a 2
gallon (10 L) bucket and using it immediately. If you have no access to an
EC meter you should leach out the pots with plain water every 4 - 6 weeks.
There are a number of fertilizers now available that contain all the
necessary nutrients in one salt mixture. The liquid product, DYNA-GRO, is
currently being used by many orchid fanciers and a comparison of its salt
composition is given in Tables 2 and 3. We used this product in a small
trial of seedlings over a period of nearly a year. Growth compared
favorably with our regular fertilizer. For a small quantity use 3/4
tsp.(3-4 ml.) 7-9-5 in 2 gal. (10 L). Check the 7-9-5-container from time
to time to make sure that the salts have not crystalized out.
SUMMARY:
Perlite has many advantages as a media for growing orchids. The most
important features are total fertilizer control, ease of potting, simplicity
of management, maintainence of excellent aeration for one cannot overwater.
The roots are easily washed clean for scientific examination and analysis or
for agricultural inspection. No other media encompasses so many outstanding
qualities. We are currently investigating the effect of watering frequency,
additives to simplify fertilizing methods and ways to control long term pH
levels.
In addition to our excellent growth with this technique we have
reports
of excellent results from a number of fanciers covering all of the major
orchid genera.
References
1. Hall, D.A. et al. 1988 Perlite Culture, ISOSC Proc. p177.
2.Pierce, J.W. 1983 Perlite Culture of Orchids, Amer. Orchid Soc.
Bull 52 :(8) p806.
Feb.1996--We now use pots such as Yogurt comes in say 5" high and varying
size to suite the plant -- we drill two holes in the side about one inch
from the bottom..The holes should be 3/8"(1 CM.) inch in diameter --this is
very important. Any pot that will give you about 1"(2.5 CM.) or a bit
more, of water in the bottom and is 5 to 7 "(12.5-18 CM.) tall will do.
We continue to be very pleased with perlite --it is very forgiving and easy
to manage -- be sure to FLUSH WATER when you water so that it pours out
the bottom and leaves much fresh solution -- we fertilize every watering..
TABLE 1
BARK PEAT ROCKWOOL PERLITE
pH OF MEDIUM SL ACID ACID SL ALK NEUT
FERT. CONTROL GOOD GOOD GOOD v-GOOD
LEACHING EASY FAIR FAIR v-EASY
AERATION GOOD FAIR FAIR v-GOOD
DISPOSAL EASY EASY PROBLEMS EASY
HEALTH HAZARD CARE CARE CARE CARE
STERILITY NO NO YES YES
ENVIRONMENT - - OVERUSE DISPOSAL --------
MANAGEMENT f-EASY f-EASY f-EASY v-EASY
SIMPLICITY FAIR FAIR FAIR V-SIMPLE
WEEDING f-EASY f-EASY f-EASY V-EASY
AVAILABILITY GOOD v-GOOD FAIR v-GOOD
COST VAR VAR VAR COMPETITIVE
EASE OF POTTING GOOD GOOD GOOD v-GOOD
REPOTTING TIME 1-2 yr. 1-2 yr. 1-2 yr. 2 yr. +
NUTRIENT MIN. MIN. NIL NIL
OVERWATERING YES YES YES NO
REWETTING FAIR FAIR POOR EASY
CATION EXCHANGE YES YES NO NO
BUFFERING SL ACID NO NO
TABLE 2
WATER ASSESMENT FOR FERTILIZING
under 50 uS excellent
50-100 uS good
100-200 uS fair
over 200 uS poor
TABLE 3
Chemical makeup of fertilizer solution
at EC of 600 micro Siemens
N 54 ppm Fe 0.37 ppm
P 18 ppm Cu 0.0165 ppm
K 84 ppm Mo 0.033 ppm
Ca 48 ppm Zn 0.11 ppm
Mg 14 ppm Mn 0.33 ppm
SO4 18 ppm B 0.10 ppm
These levels may be achieved by using by weight one part Ca(NO3)2 to 2
parts 7-11-27 (Plant Prod) or to 2 parts 5-11-26 (Grace), diluted according
to your proportioner to yield an E.C. of 600 micro-Siemens.
DYNA-GRO 7-9-5 at an E.C. of 600, although low in calcium and magnesium,
gives quite satisfactory growth.
As of 1996 we are using a ratio , by weight of 3 parts 7-11-27 to 2
parts CaNO3 and currently have a trial on of 400,,600 and 800 uS with
Odonts.
Combining information from the Eric Young Foundation, Grodan and
Naaldwijk and our own experience a TENTATIVE list of EC in uS for few
genera would be as follows. ( I do not know how to get the true symbol for
Micro an my printer)
TABLE 4
TENTATIVE VALUES FOR E.C. LEVELS
400uS Cattleya ?
Paph group ?
600uS Odontoglots & Oncidiums
Miltonias
Masdevallias
Lycaste
Coelogyne
800uS Phalaenopsis
Cymbidium
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