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This is a discussion on UPDATE Phals and Oncidium orchid in semi-hydro within the Semi Hydro / Lights / Greenhouses / Accessories forums, part of the Orchid Culture category; Originally Posted by empiref Dorstman, I clean my hydroton with a pressure hose to remove ...
TDS and EC and the relationship between them are often misunderstood. Much of what I say here can be found on the web-site of the Hanna Company byw, who make an awful lot of meters. TDS cannot be measured directly. EC can be measured ( or to be more precise, electrical resistance is easily measured) using a bridge circuit, and as it happens, EC ( electrical conductivity) is the precise reciprocal of electrical resistance. As one falls, the other rises and so on. So the meter takes that reading and expresses it as EC.
Then if it is a TDS meter, it uses a constant K to multiply the EC reading and calls the answer TDS .
The problem is that some meters use a constant of 1.2, others 1.5, and so on. I had a Dutch meter which used 2.0 ; currently I have a Hanna HI9813 which I think uses 1.5 and another Hanna HI98129 which uses 1.6. ( I can tell you why, but its irrelevant to this matter).
If I were to tell you what TDS I use for my nutrients I would have to add which meter – and when am writing for a publication, editors think that is being pedantic ! But if I quote EC, it doesn’t matter what meter you use, the reading is the same.
The required EC depends upon the compost ; inorganic need higher for obvious reasons. Summer need higher too . So my ranges vary from EC 250 to 750 ( these are in microSiemens or it may be milliSiemens – I forget which – but most recommended orchid fertilisers mixed up to makers instructions in pure,i.e. rain water or good RO water will give about 500 or 600. If giving 50 or 60 the reading is in the other one of the two. Both are fractions of Siemens – one is thousandths, the other hundredths.)
Btw – there are exceptions to these figures – very thin leaved orchids like Eulophia guineense will show leaf burn at these strengths , and often I just use rain water alone.
Looks good! I have an Onc. hybrid I bought & transferred straight to s/h. I don't think it could be happier!
hows everything going with this johnny? I have also put some of my oncidium alliance and Phalaenopsis into semi-hydro. My Beallara's are doing well but i seem to have problems with my phals. I have to keep the hydroton on the drier side by drilling holes in the very bottom of my container. Just wondering on a update. thanks