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Thread: Lucas Formula

  1. #1

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    Default Lucas Formula

    The Lucas Formula was popular about 6-8 years ago, I thought it might be fun to resurrect for any Talkers who wan't to try it.

    Lucas Formula

    General Hydroponics Flora Series Feeding Strategy - Lucas Formula

    G-M-B (Grow-Micro-Bloom)
    0-5-10 - For Vegetative cycle (18/6)
    0-8-16 - For Flowering cycle (12/12)

    The numbers above indicate the number of milliliters (ml) of Flora Grow, Micro or Bloom formulas that I use in one gallon (US Liquid) of nutrients.
    You will notice I don’t use any of the Flora Grow formula, do not need to, the Flora “Micro” provides plenty of Nitrogen.

    There are two ways to work with this formula:
    1. Top off the reservoir daily using a pH corrected water solution as required to maintain full reservoir level. After adding back an amount of water equal to the amount of your reservoir capacity you should change the reservoir and put in fresh solution.
    2. Top off the reservoir daily using a pH corrected 100% strength nutrient solution as required to maintain full reservoir level. Continue to use this nutrient solution without dumping the tank unless the PPM rises above acceptable levels.

    Between vegetative and flowering cycles you should dump your nutrients, then flush (possibly with Clearex) to remove salt buildups, then change to the other feeding program. Always shake your GH nutrient bottles before using them!

    For young plants, just transplanted into the hydro setup, give them 50% strength nutrient mix to prevent overfeeding them while their young. Gradually bring up the mix to full strength as they grow over the next few weeks or so.

    The lucas formula is normally intended for use with RO or near 0 PPM water.
    NOTE: The Lucas formula eliminates the need for Epsom salts to correct (Magnesium) Mg deficiencies in most normal feeding programs recommended by manufacturers. Cannabis needs a lot of Magnesium to thrive.

    The Flora Micro is providing the Nitrogen and the Magnesium in the proper balance, thus there is no need for the Grow formula and little or no room under the maximum acceptable ppm limit of 1600 @ 0.7 conversion.

    Calculated EC/TDS levels:

    EC microsiemen:
    0-4-8: 946 S
    0-5-10: 1184 S
    0-8-16: 1894 S

    TDS @ 0.5 conversion:
    0-4-8 = 473 ppm
    0-5-10 = 592 ppm
    0-8-16 = 947 ppm

    TDS @ 0.7 conversion:
    0-4-8 = 663 ppm
    0-5-10 = 829 ppm
    0-8-16 = 1326 ppm

    Addback Calculator - (For Advanced Users)

    Say you were running the 0-8-16 formula, at 0.7 conversion with a 22 gallon res. When you first fill it up, your ppm will be around 1330.

    Now you have been growing for a week, and some of the water has been taken up by the plants, some has evaporated, and now your res is at 947 ppm. You need to get your ppm from 947 to 1330. Here is the equation:

    ((target - current) / target) * 8 ml per gallon * res gallons = Flora Micro (ml) double this figure to get Flora Bloom (ml)

    Example:
    ((1330 - 947) / 1330) * 8 * 22
    (383 / 1330) * 8 * 22
    0.3 * 8 * 22 = 53 ml Flora Micro

    53 ml Flora Micro, double that and you get 106 ml Flora Bloom. So 53 ml Flora Micro and 106 ml Flora Bloom to add back to your 22 gallon res to get you from 947 to 1330.

    Using Hard Water GH Micro

    I had been experimenting with using the Hard water Micro as a substitute for the normal Flora Micro, this to account for my hard 350 PPM water and the lack of a large enough RO filter at the time. It has worked well for me. I just kept my reservoir below 1150 PPM @ .5 conversion and its all good.
    One tip - do not pH down this stuff, the hard water micro will drop pH gradually over the next 24 hours, for example I mix up a batch, it is at like 6.2, the next day, its at 5.6-5.8 after running in the system for a while. If I pH downed that to 5.7 before putting it in the system, it ended up as low as 4.8-5.2 by the next day.

    My conclusion, the hard water micro was buffering the alkaline crud in my water, it just doesnot do it ASAP fast like the phosphoric acid.

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  3. #2

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    Default

    Good to know,looks like if I can't get my hands on Ionic and have to use GH again I can skip buying the grow

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    Jingo, is citric acid a viable substitute?
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    Quote Originally Posted by Valentina View Post
    Jingo, is citric acid a viable substitute?
    I've never felt citric acid was a good way to go at least not for pH down. so much easier to get good stable results with phosphoric acid. I buy 75% tech grade phosphoric acid and dilute it by half with reverse osmosis water.



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  9. #5

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    This is the thread that sold me on joining the forum. I used to be on the same forum as lucas. He initially said 0/5/10 was for newly rooted clones only. Later he changed that to include vegging under weak light, eg. strip lights. He also advocated using the same wattage lighting for veg and flower. I have been using 0/8/16 for new seedlings for over a decade without problems. No such thing as a picky feeder with the lucas formula. Photos that is. My last grow was autos and they showed a hint of leaf tip burn on 0/8/16.

    The main advantage of using the lucas formula is that never again will you need to bother with additives or supplements.

    The main disadvantage of using the lucas formula is that never again do you get to try out various additives or supplements. Because if you do, it's not the lucas formula any more.

    Valentina, if you are doing drain to waste/passive hydro, the lucas formula is usually ready to go with tap water, no pH adjusters needed. If the pH test drops gives a pale straw colour, it's as close to pH 6.0 as makes no difference.

    Something I noticed about Micro and Bloom: I ended up using 3 mixes on my last grow, 0/8/16, 0/5/10 and 0/6/9. The latter is lucas for coco.

    0/8/16 and 0/6/9 both gave a pale straw colour. When seeing a hint of leaf tip burn on the autos in p/v, I switched to 0/5/10. The pH test drops showed a light green. Wishful thinking had me call it pH 6.2. The discoloured leaves said otherwise.

    So 1ml less Micro and 1ml more Bloom has a higher pH than 0/6/9. Looks like Micro lowers pH and Bloom raises pH.

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