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Root zone temperature anyone?

Is anyone controlling or monitoring their root zone temperature specifically? Have seen lots of info on it, but hard to find people who are doing it.

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I think it is a commonly overlooked issue. Cold, stagnate root zones are prime for root rot and other issues. I was just in a coco garden yesterday, 76-78* ambient but root zone temps in the low 60’s. They had stunting, lockout and eventually root rot. Cold temps also slow down transpiration and root uptake, so the plants were stuck in a cold, stagnate condition for days because the coco wouldn’t dry! Then they were hungry, but soaked through, showing both deficiencies and tip burn.

I have a data logger somewhere with a soil probe, I will try to get it set up along with the ambient logger and post comparative data. Would that be useful to anyone? Ambient vs rootzone temps?

Cold roots = slow growth, lag and potential root problems! I think this is a very common issue, especially when going from small container veg to large container flower with a shift in environmental and watering schedule without the rootzone being up to speed. (Often accompanied with transplant shock.)

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@casey;

Any kind of data would be awesome; we’re trying to find anything in the cannabis world that would support the findings that have been done extensively in the vegetable growing world… it would be interesting to know how much of a temp difference there is from ambient to root zone in any given condition. What are you growing in (greenhouse/warehouse/outdoor?)

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@greg.s
Coolio! I will work with one of my clients to get the data loggers set-up. I think there is a lot to learn in this area!

I don’t grow myself currently, but I work with many, many grows all over the world. My ideal setup in rockwool greenhouses, but I have done indoor coco, soil and rockwool production as well as soil and coco outdoor. I work with greenhouses, warehouses and outdoors all over! Maybe we can get data from multiple grows!

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@casey I think that would truly be great - this is all part of the maturing and legitimizing of the industry (in my opinion) that’s currently lacking. There’s a lot of data about the impact of root zone heating (RZH) on all plants, but nothing specific to cannabis. We’re trying to figure out how to gather data - we don’t grow ourselves (but are thinking of doing a little ‘test’ growth) but would love any kind of info on this - hopefully that would benefit the community at large. I think there are a lot of issues that are blamed on ‘over-watering’ or ‘under-watering’ etc that might simply be temperature related.

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I believe you can lose up to 60% of heat through the ground and somewhere around 35% through walls. Putting your pots or medium on a grate or anywhere off the ground slightly will help tremendously. Your rooting zone should not be getting any colder then the ambient room temp.

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@mwmzx6

Interesting take on it; it seems that root zone ‘issues’ seem to fall into two categories - for indoor (fully enclosed) growers who are using HPS lamps the issue is heat; it seems that talking to these people they don’t know how to cool their growth down so as not to ‘cook’ the plants. The second issue is growers in greenhouses/outdoor and some growers using LED lights; that’s how to warm the root zone. What seems to be consistent between the two is keeping the root zone at a consistent temperature throughout the growth period - I keep reading over and over that temperature changes in the ROOT ZONE stress the plants and cause issues with potency, grow size, flower time etc. The leaves can handle way more variation (some growers have said to me that temperature changes for the leaves is actually GOOD for the plant) - but I find that there are not a lot of growers who are addressing Root Zone differently than simply ‘grow temperature’, from what I’m reading that seems to be a mistake - but I’m not a grower. I would love for growers with experience to chime in!

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In HPS rooms with established plants the root temperature is not an issue: The plant intercepts all the light. When substrate is exposed you can have the issue of the top part of the substrate drying out and not being utilized by the roots. Covering your medium can solve that easily and will create a lot more root mass.

Insulating the pots from the (cold) floor is always a good idea.

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@Theo Interesting that you say it’s not an issue in HPS room - I’ve been told by indoor (warehouse style) growers that they struggle to keep the temperature consistent - either to cool the room during the long light hours during veg, vs. keeping the room an even temperature during black out. But I agree that the issue of Root Zone Temp. applies mostly to greenhouse and outdoor growers - especially in norther climes. Do you think it’s fair to say that the BENEFITS of RZT are :
Healthier roots=Healthier plants
Faster growth
Higher yield
Better nutrient absorption
Beneficial to good bacterial growth
More grow cycles, longer grow time (climate dependent)
Improved soil biology

?

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Along with temperature, pH and oxygen levels are very important to nutrient uptake and rhizosphere development:

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@JoeGrow - Thanks for that - interesting that she points out that too HIGH a temperature is just as bad as too LOW; we’re mostly fighting cold with the people we deal with; but it does go to show that anything outside the norm is not good!

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yes, I totally agree with that. I always have a soil thermometer in my substrate. I adjust the temperature of my nutrients to it if I need to, if it is too warm I keep the nutrients a bit cooler. But when you cover the substrate with a piece of BW film or mylar or even a thin layer of perlite you have a lot less problems in early veg when the plant does not cover the pot yet. Believe me: I have scrogged in large pots of 20 gallons and covering that can take some time ;). In a sea of green that should not be an issue. I personally hate perlite (try recycling that) so I usually use a airy peat mix without perlite (Goldlabel Custom).

Same goes for outdoor pots btw. Autopot just brought out a white pot series, and I have received a set already to replace my black ones, the root temp of my tomatoes was way too high on my deck. I prefer to use white pots outdoor.

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You’ll find similar range requirements for optimum uptake related to pH, different ranges for different ions to a certain degree. pH effects on chelating agents also comes into play.

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@Theo;
so you’re growing hydroponically - as well as in soil on the deck? lots of stuff to manage…

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@JoeGrow I love the info; BUT can we assume that the temps/levels/info is the same for Cannabis as other plants?

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lol nah, autopots are easy. Just fill the tank. I use 60/40 substrate in the autopots. (clay pebbles/long fibre coco and coco peat).

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pH largely affects solubility of an ion, so that aspect is plant independent.

While nutrient uptake in general, boron tolerance, etc., is a more complex issue which is definitely morphology dependent for any given plant species, we generally view through the lens of 3 morphological types (short and bushy, tall and stringy, etc.), which have different nutrient requirements to support their ideal development.

Hybridized plants can be directed to express different phenotype potentialities based on a variety of garden conditions, explaining the variation in expression among any given strain.

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Oops. I should point out that boron tolerance is primarily species dependent, but greatly affected in how it presents relating to pH. Below pH 8.6 it primarily presents as boric acid with no ionic charge, above pH 8.6 it primarily presents as the borate ion and is a bit of an outlier when it comes to solubility in that way.

You’re looking for 0.02 - 0.05 ppm for optimum functioning as a micronutrient with B.

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@JoeGrow Yikes! That’s a lot of info to process for my little old brain! thankfully for me I’m looking at mostly soil grows… but I appreciate the info! Have you done any growing in soil or coco?

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@theo i’ve heard of autopots, never tried 'em - looks like a cool solution. i will have to investigate - maybe I can figure out how to heat those!
:wink:

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