Watering needs for Cannabis, what is your point of view?

Dear all,

I am working on a lot of cannabis projects about designing and quoting irrigation systems but the demand about water needs for cannabis is always changing from a grower to another. To be more pertinent with your demands I am looking for the best capacity of irrigation you want in your facility.

Could you tell me how many liters of water you want to give to your plant under extreme conditions per plant and per hour (liter/plant/hour)?

May you have an average data about your watering management about watering needs in liter/pot/day?

In this way, we could give you our best proposals and be closer to your personnal needs.

Let’s discuss about it

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Calling our Water and Irrigation GN Mentors @JoeGrow and @Jess. Can you provide some insight here for our friend @richelgroup?

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Thanks for connecting us Nick :slight_smile:

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Happy to help!

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There must be a cannabis cultivation aphorism related to “herding cats”. That said, for a single feeding of any size pot up to about 5 gallons I would say that your guidance could be simply the amount of nutrient rnecessary to achieve the targeted amount of runoff required to avoid salt build-up and nutrient lockout.

But, herding cats again, that could be anywhere between 10% and 30% depending on the grower.

It seems to me that in commercial indoor hydroponic cultivation with 12 hours of light as opposed to greenhouse growing, the watering “demand” has been adapted to limitations in the irrigation systems resulting from the chosen design based on readily available equipment. Hence the popularity of micro-dosing.

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It is hard to say how many liters you need per plant each day seeing as it is heavily dependent on your growing media. Different growing media will need different watering amounts. For example, when growing in rockwool, it makes sense to water 4 - 6 times a day, whereas when growing in coco coir, 2 or 3 shots a day would suffice.

I very much agree with what Joe said: " It seems to me that in commercial indoor hydroponic cultivation with 12 hours of light as opposed to greenhouse growing, the watering “demand” has been adapted to limitations in the irrigation systems. "
In my experience, this is very much the case.

On a 12/12 cycle, growing hydroponically in 3 gallon pots using coco or peat based substrates, I usually look for a total of 3-4 liters a day on average. If I’m watering heavy after dry down days, it could be closer to 4-4.5 due to the need for runoff in a hydroponic set up, whereas there are other days where pots simply don’t need water. Again, this is often dependent on the set up and any limitations that a system may have.

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I definitely agree with Jess on the above, but have a different experience wrt the quote below:

Every top-feed grower that I encountered in the Los Angeles area were either feeding once a day in rockwool or coco with runoff, or trying to but hampered by practical irrigation limits (mostly in their irrigation engineering knowledge base).

I guess it all comes down to the likelihood that there is room for scientific evaluation of the different irrigation methodologies and schedules as well as room for leadership and innovation. Perhaps @richelgroup could lead the way.

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Water through and let dry in super soil or coco. Cannabis can go low when it comes to actual moisture percentage in the soil. I’ve tested with a tool I use all the way down to 6% .
Deep infrequent watering

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Agreed. And, with quick-dry rockwool cubes and one watering when the lights come on, they are at the right moisture after 12 hours for lights-off with minimal chance of mold or pm, you gain complete control over the nutrients for maximum yield, and can replant (other plants, not cannabis) in the used media or shred it into a compost. No soil clean-up.

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The answer will be enough to saturate the media and have a proper run off from the pot. There is so many factors that contribute in determining how often and how many liters/gallons you need to give to your plant to saturate . How often depend from the style of growing(greenhouse/indoor),the stage of the growth ( early/late veg , flowering )the conditions(temperatures,humidity),the size of the pot(1,2,3gal …) ,the type of the pot(fabric plastic…), the medium(peat,coco,rockwool…) . And how much you will need to saturate a pot it depend from the type of the media : water capacity (peat moss has high ) and wetting condition of the media (some reused medias has low wetting abilities ,means that you will need more water to saturate them) .Example the peat moss based potting mixes has aa high water capacity but with the time is losing the wetting ability ,reused peat moss can show signs of fast drainage ,it will look like the media is saturated ,but inside the pot you will find a lot dry spots .

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Thank to all of you for these answers @JoeGrow @Jess @eldindupljak @ralpht
I understand that all this settings (type of media, physiological stage of plant, lighting regime, plant size…) have to be considered.
I was only looking for an average range which could be used even if these variations are exisiting.
But as you said, this data depends on all the factors described before.

I agree with @JoeGrow “It seems to me that in commercial indoor hydroponic cultivation with 12 hours of light as opposed to greenhouse growing, the watering “demand” has been adapted to limitations in the irrigation systems resulting from the chosen design based on readily available equipment”, but we can have an other approach and make the best compromise between available equipment and biological water needs of the plant.

@Jess “On a 12/12 cycle, growing hydroponically in 3 gallon pots using coco or peat based substrates, I usually look for a total of 3-4 liters a day on average. If I’m watering heavy after dry down days, it could be closer to 4-4.5 due to the need for runoff in a hydroponic set up, whereas there are other days where pots simply don’t need water. Again, this is often dependent on the set up and any limitations that a system may have.”, many thank you to sharing your personnal experience.

@ralpht “Water through and let dry in super soil or coco”, absolutely agree with you.

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