Fertigation — Precision Irrigation and Nutrient Delivery

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hi I'm Darren Kaplan from The canic Cribs Horticultural Consulting team and today we're here to share some Concepts that we discuss and Implement to help commercial cannabis Growers operate as efficiently and successfully as possible

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making the right irrigation decision to make the difference between a poor quality and a good quality crop if you've been growing for months or years you know that to be true today we're going to talk about the fundamentals of irrigating cannabis

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cannabis there's a lot of information out there in the industry about Precision Irrigation crop steering drought stress but I'm going to focus today just on the fundamentals

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the first most important thing to consider is that cannabis compared to other Horticultural crops likes a dry root Zone it likes to have its roots relatively dry between irrigation events

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an important concept here to understand is water logging you often hear about overwatering underwatering that can be confusing cuz it can often be linked to the volume of irrigation you apply and the amount of times that you irrigate

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so container capacity is the amount of water that your Cube or your pot can hold after it's been completely irrigated to saturation and allowed to drain off completely

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if you maintain that amount of water in your root zone for an extended period of time then you can start seeing something called water logging overwatering is often a misnomer for water logging

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if your substrate is wet for a long period of time that's water logging and you start running into issues with low root Zone oxygen you have High incidence of root Zone pathogens like pythium and fusarium and you start also running into issues with reduced nutrient uptake

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so the ultimate goal here is to irrigate your plants completely reach that container capacity ideally once a day could be more and allow a sufficient dryback between irrigations so that the roots have time to dry out and the cannabis plants can perceive the benefits of the dry root zone

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so the first step is to match your pot size with your plant size and the growth stage

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if you miss an irrigation or you miss several irrigations you're at high risk of crop failure if you have too big of a pot then the plant will naturally not pull up enough moisture from the pot overnight and you'll have water logging conditions

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for Simplicity I'm going to break down the irrigation strategy of growing cannabis plants in containers into three phases Phase 1 2 or three or P1 2 or three

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phase one is your first irrigation of the day ... in phase one that goal is to reach container capacity ... starting 30 minutes to an hour after the lights are on and the plants have already begun to transpire remember transpiration before irrigation

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phase 2 is used to extend the period of container capacity ... the idea is that the timing of the end of P2 allows for sufficient dryback until the next P1 the subsequent day

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important to consider when you're hitting container capacity you're hitting it to run off ... we try and irrigate 10 to 15% more than you would need to just container capacity ... the leeching fraction

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phase three is the period of time from the last irrigation of P2 all the way to the first irrigation of P1 ... typically we like to see a dry back of 30 to 50% ... overnight and during P3

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... the risk is that if some of your plants are having a 50% dryback then there's other pots ... that might be going even further ... some growing media ... once it hits those really low levels of moisture it's hard to re-saturate them

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... after you transplant the roots are not fully developed ... there might be several days where you don't have to irrigate at all ... when you start seeing that first dryback to 30 to 50% then you have to start thinking about that P2 timing

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... the easiest way is kind of the lift and feel method ... if you have a scale that's an even better way ... or ... volumetric moisture content sensors ...

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... remember is not to get too dry with those types of growing media ... maintaining Field capacity is incredibly important ...

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... if you're using drip Stakes ... make sure ... slow controlled irrigation ... avoid channeling ...

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