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Do you use the lucas formula for your nutrient level?

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    #16
    Originally posted by nelson420 View Post
    Douglas, I remember reading a post where you tell your general guidelines for harvest, regarding feeding strength. I remember you give 5 days of water only before harvest. Am I right?

    If you do give them 5 days or so of RO water before harvesting, do you taper the feeding strenght gradually or go "cold turkey"?

    In my case, for example, using GH 2 part, do you recommend using only the bloom for a few days before going to water only? I am in coco.

    Thanks for all your valuable information
    Always glad to help more quality cannabis enter the world. You're most welcome. Coco is a bit different, but I'll still answer from a drip/dwc standpoint using inert media for reference.

    When physical flower bulking quits, (around 30'ish days for the average 60 day strains), the feed demands of the plants change. Historically I've done my best to time my nutrient add-backs so the solution is weakest when the plants reach this point. Too hot of a solution at this time can cause root damage and a pH drop, and will definitely have a negative impact on flower quality.

    So once they're on the downslope to harvest I'm only adding water each day. 5 days before harvest the nute solution is usually between 300-400. (raise your lights a bit each day the last 10 days. ) This is the solution I like pumping into a garden or my flower beds or around trees and other plants I care about.

    5 days before harvest I pump out as much of the nute solution as I can from the res and replace with pure r/o. With drip through media I'll even run a few gallons of clean water through the drip system, dump it again, then fill with fresh r/o. I try to reach 50ppm or less from residues on the roots and such.
    The ppm is usually back to around 300'ish on harvest day.
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      #17
      I'm using Lucas and feed 600-800ppm under HPS. It bumps up to 850-950ppm if I add Mg/Cal under LEDs.
      Specs for the New Growroom

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        #18
        I have not got it right yet, but thought lucas a bit high on K for coco. The idea is 100-100-200 but coco provides maybe 60ppm more K itself. I ran some for a few days without K and the runoff still contained 90ppm of K. The older it gets the more it provides, as it decays quicker. Mine was about 18 months old.

        If we look at h3ads, he started out with something like lucas but N was lacking. He tried more N but it wasn't right. He then put his N back and stopped antagonising it's uptake by dropping K. That is the h3ads formula. As a byproduct he lowered P and got away with it, and lowered Mg, which he put back with epsom. His underlying problem was almost certainly the 60-90ppm of K he couldn't see. Coming from the coco.

        Many people are using all-round feeds in coco, well under dose, with the Ca+Mg raised back again. In effect this gives less N and P but these go largely unnoticed. Only yield is effected, not plant health.

        I have seen people approach 200ppm K but with P and Ca numbers that heavily suppress it. One working example is 190P 165K 280Ca which with the coco's input looks more like 190-250-280 which starts to make sense.

        I will leave off where I started. I have not got it right yet. I'm still using about 100K which isn't offsetting the sodium the coco also supplies. It seems K must be reasonable to keep the sodium ratio low. But can't be high so needs suppressing.

        Don't know what I'm doing yet... but if you use Lucas ratio's you will probably have to feed low.

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          #19
          Originally posted by f-e View Post
          I have not got it right yet, but thought lucas a bit high on K for coco. The idea is 100-100-200 but coco provides maybe 60ppm more K itself. I ran some for a few days without K and the runoff still contained 90ppm of K. The older it gets the more it provides, as it decays quicker. Mine was about 18 months old.

          If we look at h3ads, he started out with something like lucas but N was lacking. He tried more N but it wasn't right. He then put his N back and stopped antagonising it's uptake by dropping K. That is the h3ads formula. As a byproduct he lowered P and got away with it, and lowered Mg, which he put back with epsom. His underlying problem was almost certainly the 60-90ppm of K he couldn't see. Coming from the coco.

          Many people are using all-round feeds in coco, well under dose, with the Ca+Mg raised back again. In effect this gives less N and P but these go largely unnoticed. Only yield is effected, not plant health.

          I have seen people approach 200ppm K but with P and Ca numbers that heavily suppress it. One working example is 190P 165K 280Ca which with the coco's input looks more like 190-250-280 which starts to make sense.

          I will leave off where I started. I have not got it right yet. I'm still using about 100K which isn't offsetting the sodium the coco also supplies. It seems K must be reasonable to keep the sodium ratio low. But can't be high so needs suppressing.

          Don't know what I'm doing yet... but if you use Lucas ratio's you will probably have to feed low.
          What is your pH at? Are you using RO water or tap water? I've been using h3ads formula for 10 years in coco.

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            #20
            H3ads and Lucas are two different people. They both used the same two bottles of feed, but differently. Lucas was first, and he used the bottles to target Mel Franks NPK ratios. This became know as the Lucas formula. A bottle mixing practice to get Mel's numbers. It was later in coco that H3ad lowered K to account for coco making it's own. Though I'm not sure he knew that. He was watching the effect K levels were having on his N.

            My pH and water have been everything. I have a thread about my troubles https://www.icmag.com/forum/marijuan...3#post17869215
            It's getting too long to keep it going.

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