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University of Guelph paper- Flushing is a myth!

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    University of Guelph paper- Flushing is a myth!

    Here's a link to a PDF. I can't copy and paste from pdf.

    Basically they used 4 or 5 different flushing techniques.

    No major difference of nutrient levels between the bud samples.

    One pro from flushing is saving money on nutrients for last two weeks.

    https://atrium.lib.uoguelph.ca/xmlui...=8&isAllowed=y

    What does everyone think?
    "I have only read fragments of your posts. But I have read enough to know that you can grow some mean herb."
    --- CVH
    _____________________________
    "we growing.
    till the fucking zombies show."
    --- Useless.Gardens

    My current thread

    #2
    Irrigation Management Strategies for Medical Cannabis in Controlled Environments
    By
    Jonathan Stemeroff
    A Thesis
    presented to
    The University of Guelph
    In partial fulfilment of requirements
    for the degree of
    Master of Science
    in
    Environmental Science
    Guelph, Ontario, Canada
    © Jonathan Stemeroff, November, 2017
    Irrigation Management Strategies for Medical Cannabis in Controlled Environments
    J. Stemeroff, MSc
    Erratum Document for Previously Approved E-Thesis Submission
    A post-approval (re)-examination of the raw data discovered unrecoverable errors in the
    handling and reporting of the water potential data, with further issues regarding the nature of
    the treatment differences. The general errors are:
    1) Upon further review of the raw data logs it was discovered that the Control and Mild
    Stress treatments were in fact the same (ref. page 38). Both treatments had the same
    number of irrigation events (i.e. total water applied was the same) in all three trials.
    The irrigation events were offset by 1-day but they both occurred at 2-day intervals.
    a. Resolution – Any observed differences between the control and mild stress
    treatment should be disregarded. Detected differences in agronomic and
    metabolite production between the Control and Mild Stress treatments can only
    be attributed to random chance and variation in the growth facility, not a
    response to distinct irrigation regimes. Affected Figures – Disregard Control and
    Mild Stress treatment effects in Figures 4.11 (page 54) and 4.13 (page 55)
    2) Raw data was not properly filtered to remove erroneous readings (e.g., positive values
    of plant water potential; non-sinusoidal or flat line response) resulting from instrument
    fouling and condensation within the sensing chamber. The inclusion of erroneous data
    resulted in skewed relationships between cumulative plant water potential and
    cumulative vapour pressure deficit.
    a. Resolution – Disregard the relationships depicted in Figures 4.1 (page 44), 4.2
    (page 45), 4.3 (page 46), 4.4 (page 47), 4.5 (page 48), 4.6 (page 49), 4.7 (page
    50), 4.8 (page 51), and 4.9 (page 52).
    3) The apparent two-phase relationship between CWP and CVP shown in Figure 4.1 (page
    44) and subsequently highlighted and independently analysed in Figures 4.2 (page 45)
    and 4.3 (page 46), is the result of missing data (logger failure) during the middle phase
    of the first growth cycle; the missing data was not properly accommodated resulting in
    an apparent separation of the response relationship between early and late growth
    periods. The subsequent analysis of flower cycles 2 and 3 included an analysis of this
    artifact-based separation; as such, Figures 4.5 (page 48), 4.6 (page 49), 4.8 (page 51),
    and 4.9 (page 52) are not meaningful as there is no data to suggest or support treating
    the data as two distinct groups.
    Based on the above errors, any conclusions outlined in section 6.1 (page 62-65) should also be
    disregarded.
    3
    ABSTRACT
    Irrigation Management Strategies for Medical Cannabis in Controlled Environments
    Jonathan Stemeroff Advisor:
    University of Guelph, 2017 Professor M.A. Dixon
    Medical cannabis production is a new industry in Canada and represents a challenge
    for the production of a repeatable and standardized product for medical use. A reliable and
    reproducible environmental control strategy can contribute significantly to meeting this
    challenge. Irrigation management and control of plant water status is one of the key
    environmental control elements. To assess the effects of various irrigation management
    strategies this study deployed in situ stem psychrometers to measure the water status of
    plants. As a routine feedback device for irrigation control these devices are not ideal for
    large-scale production so correlation with the key environment variable representing the
    aerial demand for moisture (vapour pressure deficit) was assessed. By establishing a
    relationship between cumulative water potential (cWP) and cumulative vapour pressure
    deficit (cVPD) an irrigation management strategy that predicted plant water status based on
    measurements of cVPD could be employed. Three treatments; control (irrigation events every
    1-2 days), mild-stress (irrigation events every 2 days), and moderate-stress (irrigation events
    every 3 days) were tested. The effects of flushing were also investigated to determine
    whether it had the intended effect of reducing nutrient concentrations within the dried bud.
    Through the use of psychrometers, water status (cWP) thresholds were correlated with
    humidity (cVPD) thresholds and reduced irrigation frequency resulting in water use
    reductions up to 45.7% which had negligible impacts on yield and cannabinoid profile.
    Flushing was found to be ineffective in removing any significant amount of nutrient from the
    bud.
    Such is life ...

    Comment


      #3
      G `day CR

      Yep flushing is a myth !
      How did people flush , before hydro ? Kinda hard to remove all the nutes from soil ?

      Unflushed harsh weed ? BS !

      Thanks for sharin

      EB .
      Such is life ...

      Comment


        #4
        Thanks Elmer! . I was in process of typing it out on my phone.

        And wasn't being fast.

        Much appreciated
        "I have only read fragments of your posts. But I have read enough to know that you can grow some mean herb."
        --- CVH
        _____________________________
        "we growing.
        till the fucking zombies show."
        --- Useless.Gardens

        My current thread

        Comment


          #5
          Originally posted by Elmer Bud View Post
          G `day CR

          Yep flushing is a myth !
          How did people flush , before hydro ? Kinda hard to remove all the nutes from soil ?

          Unflushed harsh weed ? BS !

          Thanks for sharin

          EB .
          I find it interesting that even fertigating till end showed no difference in nutrients.

          I wonder if those plants were in senescence and not taking up nutes. But did they fade?
          Plant is supposed to uptake what it wants.

          Like everything else, learning something new just leads to more questions.
          "I have only read fragments of your posts. But I have read enough to know that you can grow some mean herb."
          --- CVH
          _____________________________
          "we growing.
          till the fucking zombies show."
          --- Useless.Gardens

          My current thread

          Comment


            #6
            Yep read this one about a year back on Glows site. No surprises there.... The idea that you could starve a plant and force it to access stored nutrients was always totally out there.

            Comment


              #7
              .
              Last edited by SandyFantasyman; 08-17-2019, 14:07.

              Comment


                #8
                Originally posted by CannaRed View Post
                I find it interesting that even fertigating till end showed no difference in nutrients.

                I wonder if those plants were in senescence and not taking up nutes. But did they fade?
                Plant is supposed to uptake what it wants.

                Like everything else, learning something new just leads to more questions.
                G `day CR

                Mid to late flower the electrical charge of the roots decreases .
                Equals less up take of nutes .

                I hear you on the using up stored nutes angle .
                But the idea that the minerals would be rinsed on back out always baffled me .

                Flushed / unflushed , indoor / out door , organic / hydro .
                Proof of the pudding is in the eating .

                Thanks for sharin

                EB .
                Such is life ...

                Comment


                  #9
                  I never really thought it was flushing the plant itself. I thought it was to flush the media.
                  "I have only read fragments of your posts. But I have read enough to know that you can grow some mean herb."
                  --- CVH
                  _____________________________
                  "we growing.
                  till the fucking zombies show."
                  --- Useless.Gardens

                  My current thread

                  Comment


                    #10
                    I don't care for the metallic, nutrient taste on inhale/exhale.....I'll continue to flush.
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                    Comment


                      #11
                      I think the word has been used to mean at least two different things. Some people use it to mean withholding nutrients (N) past peak flowering to get flower that's lower in chlorophyll at harvest. Other people just mean running water through the soil mix to 'flush' the excess nutrients from the medium itself, usually to correct an over feeding mistake.

                      Combining the two concepts gets me a bit confused. So water is run through the mix in an attempt to achieve low chlorophyll at harvest? I don't think that will work. Even just withholding the N doesn't work very well unless you're using a container size that restricts roots at peak flower.

                      As to whether cannabis grown with restricted nutrients during flower tastes and smells better, I'm pretty sure it does. It's the same with grapes, more flavorful but smaller. Besides, N during flowering builds more vegetative mass in the bud itself, which if you think like I do that trichome count is genetic, is basically reducing potency by increasing leaf mass. That might be an even better reason to limit nutrients during flower.

                      Just my 2c, anyway cool discussion!
                      "I only grow to support my breeding habit." Mr. Greengenes

                      Comment


                        #12
                        Interesting, no doubt will challenge the folks who swear by the flush.

                        As I do salts in coco, low EC, 0.8, my reduction in nute strength to
                        0.4 EC the few days before chop is prepping the coco for re use.

                        The plants don't dissipate stored nutes through flushing anyway,
                        whatever is taken up stays there until its burned.


                        Good thread!
                        "So we're just done with phrasing, right, that's not a thing anymore?."

                        "He's like Jesus, just dumber and fatter, and holds the Bible upside down".


                        Comment


                          #13
                          many plant trials are laughable in comparison to the methods being used in cultivation and in comparison to methodology that grows the best smoke chem, transitional or organic
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                          What you may win, what you may lose
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                          For the wise men and the fools
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                          Comment


                            #14
                            Originally posted by Mr. Greengenes View Post
                            I think the word has been used to mean at least two different things. Some people use it to mean withholding nutrients (N) past peak flowering to get flower that's lower in chlorophyll at harvest. Other people just mean running water through the soil mix to 'flush' the excess nutrients from the medium itself, usually to correct an over feeding mistake.

                            Combining the two concepts gets me a bit confused. So water is run through the mix in an attempt to achieve low chlorophyll at harvest? I don't think that will work. Even just withholding the N doesn't work very well unless you're using a container size that restricts roots at peak flower.

                            As to whether cannabis grown with restricted nutrients during flower tastes and smells better, I'm pretty sure it does. It's the same with grapes, more flavorful but smaller. Besides, N during flowering builds more vegetative mass in the bud itself, which if you think like I do that trichome count is genetic, is basically reducing potency by increasing leaf mass. That might be an even better reason to limit nutrients during flower.

                            Just my 2c, anyway cool discussion!
                            Taste is a subjective thing. Everyones taste buds are different. The study found no yield losses occur by running water only for the last 14 days. This is because cell division is about nil towards the end of flower. The conclusion of the study being that running water only for the last two weeks is the go simply for saving money on inputs.

                            Comment


                              #15
                              Feed only enough to keep the leaves evenly green and cut back 1/2 way thru flowering.
                              Hope this Summer was over already.

                              Terpene Amplification

                              Comment

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