Lucas formula at .5 conversion

Discussion in 'Hydroponic Growing' started by cadburry, Nov 18, 2011.

  1. #2 bhp70, Nov 19, 2011
    Last edited by a moderator: Nov 19, 2011
    What do you mean by "the target" 1300 ppm?....1300 is the Lucas formula target ppm for growing under HID lights bigger than 400W if one is using a 0.7 conversion meter. That's what you should be close to if going 0-8-16.

    Mix to full strength, stick your 0.5 meter in there, and you should read close to 947...the ppm system now tells you that this is equivalent to the 1326 ppm which would be read with a 0.7 meter. The whole ppm system is fucking stupid and is merely a speculation about what the total dissolved solid amount is. THE VAST MAJORITY OF ALL METERS GROWERS WILL USE READ EC AND CONVERT IT TO TDS.....IT'S A GUESSTIMATE OF WHAT THE AMOUNT OF SOLUTE PRESENT IS, PRETTY IMPRECISE.

    If you have a 0.5 meter, then mixing Lucas at full strength with RO water should theoretically give you 947 ppm.

    Sounds like you are treating the ppm conversions as interconvertible which they are not. I haven't been doing hydro that long, but I've fucked with it long enough and talked to enough people about ppm that this is why I think ppm sucks on the same level that the whole SAE measurment system sucks. Makes it damn near impossible to have a conversation with someone about numbers and know that the same quantity is being talked about with out a buch of converting and manipulation of numbers. Fucking stupid. My next meter is a straight EC meter and to hell with this ppm crap...I know it's the standard, but just cuz it's the standard in the US doesn't mean it's the most efficient way to communicate numbers.

    Anyway, there's my ppm rant....for what it's worth, I've been farting with the LF and the 0-5-10 standard for low lighting situations....I'm finding that too low for what I've got going on right now, so I'm bumping it up.

    Some vet will possibly correct me here, but I don't think the Lucas formula is necessarily intended to be an absolute, but rather a good starting point. In theory it provides everything the plant needs, but everything I've read Lucas say implies that it is fine to mess with numbers and additives...he just doesn't feel it's necessary.

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