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N-P-K Their roles in the life cycle of marijuana and how it pertains to my feeding

Discussion in 'Hydroponics / Aeroponics' started by MYWhat?, Dec 26, 2011.


    MYWhat? Active Member

    N-P-K Their roles in the life cycle of marijuana and how it pertains to my feeding schedule.

    I'm going to paste a few descriptions of what N-P-K are used for in a plants life cycle and compare it to my nutrient line. (General Hydroponics 3 part Flora series.)

    Nitrogen is primarily responsible for vegetative growth. Nitrogen assimilation into amino acids is the building block for protein in the plant. It is a component of chlorophyll and is required for several enzyme reactions.

    Phosphorus is a major component in plant DNA and RNA. Phosphorus is also critical in root development, crop maturity and seed production.

    The role of potassium in the plant is indirect, meaning that it does not make up any plant part. Potassium is required for the activation of over 80 enzymes throughout the plant. It's important for a plant's ability to withstand extreme cold and hot temperatures, drought and pests. Potassium increases water use efficiency and transforms sugars to starch in the grain-filling process.

    Flora Grow: 2-1-6 (why would the grow hold the majority of K?)

    Flora Micro: 5-0-1 (notice the micro holds the majority of N.)

    Flora Bloom: 0-5-4 (the bloom looks to be ok)

    During veg their feeding schedule calls for 12.5 ml grow, 7.5 ml micro, 5 ml bloom per gallon of water.

    During bloom their feeding schedule calls for 5 ml grow, 10 ml micro, 15 ml bloom per gallon of water.

    Why are they calling for so much N during the bloom phase ?

    I'm looking to phase out the N during the last month or so of bloom. Any suggestions are welcome.

    frettfreak Well-Known Member

    good thing to keep in mind is that the GH schedule is FULL STRENGTH. You will probably never use that much. I would start at half strength and move up from there. important part would be to make sure your PPM's are in line with where they are supposed to be for your phase of growth.

    My suggestion would be to not over think it too much. The GH nutes (which i use as well) have been around for a VERY long time and there is a reason for that. I can tell you that i had a N toxicity in veg and bloom a few times, but that was because i was simply feeding them too often.

    However, if you are really concerned about phasing out the N during the last month (again, i would probably just follow the feeding schedule as they have scientists that develop the formula) maybe look at doing more of a lucas formula (google it) and see how that goes for you. The mix is different and actually cuts out the grow, but the reasoning behind that is that the micro contains enough N and everything else. :)

    MYWhat? Active Member

    Ya I started off (my first hydro grow) with the lucas formula. Now I use all 3, mostly because grow holds the majority of K and bumps the P up 1. I'm thinking of maybe backing off on the Micro during the last month or so of flowering. I know that the Micro holds most of the micro's though so I wasn't sure if that would work.

    This round I have run into a small issue. At week 5 of flower my plants stopped taking up nutrients. But they have shown absolutely no signs of any deficiency. No yellowing leaves, root rot or anything. I'm sure most folks will say I have locked out my nutes. But how can you lock out every nutrient? I'm starting to wounder if they were just full, unable to hold anymore nutrients? Is that possible , without burning the plant? (Nutrient levels were maintained at 1200-1300 ppm)

    So I flushed them with final phase for 3 days. Then loaded the reservoir back up with PHed water let it run for the night cycle. Then reloaded it again with fresh nutrients. I'm running at 1000 ppm now and it seems to be staying there despite the fact that the water is being used. So they are taking up nutrients now, just not like crazy like before. Before I would set it at 1300 and 2 hrs later it would be down to 1100.

    So now I have been reading up on nutrient uptake and whats used during different phases.

    I know this is a touchy subject, but I'll ask anyways. Should I be staying green all the way through or should I find a way to go somewhat deficient on N ? I do plan on flushing for the last week of my grows in the future.

    Thanks frett and whom ever else would be kind enough to share their views !

    frettfreak Well-Known Member

    Hmmm.. very odd. I top water, so i dont have much knowledge of nutrient levels in an ebb and flow res, but definitely seems odd.

    as far as "making them" go N deficient, i wouldn't try to give your plants a deficiency. They will usually naturally go a little N deficient the last couple weeks, but I wouldn't create that deficiency. If its available and your plants need it, it will use it.

    As a side note, i always flush the last 10 days of my flower cycle and love the results. You can see it in the way it burns, tastes and smells (IMO). I can always tell when sampling other product that hasnt been flushed enough.

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