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Interesting Paper On Vpd And Flushing

Discussion in 'General Indoor Growing' started by OldManRiver, Dec 10, 2018.

  1. https://atrium.lib.uoguelph.ca/xmlu...t7iPF94NGG4A_2cPXI9GnkmgAesrtDw5YMCDKp9u7kgS4

    The abstract, emphasis mine:

    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.
     

  2. This substantiates what I have been saying for some time. Great information. Thank you for sharing
     
    Madmax, testiclees and madgrower like this.
  3. This interests me very much

    FUTURE STUDY
    With the use of irrigation thresholds measured in cWP or cVPD there are many other
    areas of research that can be studied. Specifically, for cannabis, there is the potential to investigate the impacts of further drought stress on the yield and concentrations of cannabinoids. This experiment did not push the plants too far with respect to water stress, and through the use of higher thresholds there could be increased production of certain cannabinoids that would be the target of use for certain medical treatments. Drought stresses could also be used to change the overall composition of cannabinoids produced and could allow producers to create irrigation thresholds for specific cannabis cultivars to produce target cannabinoids. This research can also be applied to any other medicinal plant so that producers can create irrigation thresholds that produce higher levels of medicinal compounds. It could also be used in the production of herbal plants to increase the production of target secondary metabolites to create plants with the desired physical characteristics such as a desirable culinary compound within a basil plant.
     
  4. CrimsonEcho

    CrimsonEcho Premium Member Supporter

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  5. JWM2

    JWM2 Premium Member Supporter

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    Why publish a report if the conclusion should be disregarded?
     
  6. CrimsonEcho

    CrimsonEcho Premium Member Supporter

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    Lots of it should be disregarded it seems :)
     
  7. Flushing is still relevant
     
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  8. JWM2

    JWM2 Premium Member Supporter

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    Oh absolutely and they should start with that report ;-)
     
  9. CrimsonEcho

    CrimsonEcho Premium Member Supporter

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    I was already sure on that :)
     
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  10. I've used drought stress training to promote faster flower setting for years. It's an old Tomato growers trick.
     
  11. I don't understand how they came up with there findings to me flushing is a crucial part
    of the whole process . Just as drying and curing are also crucial to the process .
     
  12. They flushed and measured the levels of nutrients remaining in the bud, compared to unflushed bud, and found that flushing doesn't have the effect you think it does. It appears to not have any effect on nutrient concentrations in the dried bud.
     
  13. CrimsonEcho

    CrimsonEcho Premium Member Supporter

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    There is a real confusion based on the name of the flushing. I think it is better to say fading. The only thing that would make the buds cleaner is, imo, letting it fade. Flushing is something else. We call last 2 weeks flushing but its better to call it fading. Just plain water so plant uses whats left inside.
     
    gwheels, Therighthigh, jammie and 6 others like this.

  14. Actually fading forces the plant to relocate any nutrients it needs to flower production so it is all the same effect.

    Only difference in final product is there is less chlorophyll if the bud leaves are yellow.
     
  15. CrimsonEcho

    CrimsonEcho Premium Member Supporter

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    Same effect with what exactly? Running copious amounts of water thru medium and hoping the plant will regurgitate ions back into the soil is different then letting the plant incorporate the last bits of nutrients into making new cells. In one you’re just wasting water because the cec will not let you strip much nutrients from the soil itself and plant doesn’t give back what it already has.

    On the other hand, the fade, is the natural process that gives a clean smoke by letting chlorophyll to degrade and plant to senescence. Ergo, its better to use the term fade rather than flush since we don’t flush anything.

    Ps; not overfeeding is the only real flush imo.
     
  16. I second this
    You can’t really undo what you’ve toasted. I be found in my grows, a smooth clean smoke results from fading. I can tell the difference big time. Flushing shitloads of water through all at once not so much
     

  17. Call it what you want. But in gardening the term for what pot growers call flushing is leaching. And many things will cause the plant to fade.

    It’s pretty much the same effect to the plant. Underfeed to harvest a deficient plant. (Faded) or run a lot of water through the pot which washes nutrients out of the medium and messes up the cation exchange which can lock up the roots. (Flushed and faded)

    And I agree proper feeding is the only answer.
     
  18. The mistake I made on latest grow was cutting off nutrients to sharply and to soon. They hadnt even gone 7 and I was feeding water only with 10-15 % run off. C99 finished ok but I could have had more weight and color. But my blueberry is still standing halfway through week 10 and all my leaves are showing me it’s begging for more. I’m now going to try instead is slowly easing off the ppms in my water until it looks like a week left. Only Then just run 0ec filtered lukewarm with slight runoff every time . Here’s what I’m on about with that blueberry
     
    AD1FBFB6-092E-4780-BBBB-72DB0E50BA60.jpeg
    greencraft, PharmHand and MIMedGrower like this.

  19. The “when to flush” thing messed me up on my first grow. So much stress on a seed grow about timing that doesn’t matter.

    Since I have learned to always feed what they look like they need. Which is more going through stretch and peak bud production and less through ripening.

    I mix separate gallons for each individual plant. They are all different strains or crosses and at all different stages like you have.
     
  20. I have to agree not overfeeding is the key, I guess the term flushing can be misleading
    to some . If your running bottled or powdered nutes it is generally a good idea to go with plain water
    at the end of the cycle at least in my garden.