Bert Pressman said:
I have read all those heated discussions on EC & TDS and wondered if I was
experiencing a resurrection of medieval philosophers arguing about how many
angles can dance on the head of a pin. Do orchids possess EC meters that tell
them when to burn their roots? Can conductivity distinguish between good
guys, such as nitrate, potassium and calcium, and bad guys such as sodium? And
what about urea which has no conductivity at all? How do orchids decide how
to distinguish straight water washes from high TDS fertilizer solutions? It would be wonderful if there were a simple instrument that would predict with accuracy the response of orchids to a dousing, but wishing won't make it so.
I know from the municipal authorities what's in my water initially and I
know what I add to it. I do monitor its pH with a glass electrode. What more
do I need to know? Bert Pressman
Bert,
You are missing the point. You should monitor your fertilizer concentration. You can do this with an EC meter combined with the fertilizer manufacturer's data. You can't do it with a so-called TDS meter unless you know what factor was used to convert EC to TDS.
IMHO, this is much more important in an on-going basis than monitoring pH.
Martin Epstein
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