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Root zone temperature.

Posted: Mon Mar 19, 2018 12:45 pm
by Dick Fein
I found this quite interesting especially for my DWC garden.
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Oxygen at plant roots is an important factor in all scales of agriculture and horticulture; especially in hydroponic, and to a lesser degree aeroponic systems. Typically, the higher the oxygen solubility of a nutrient solution, the better.

Increased dissolved oxygen increases the permeability of plant roots to water and macro/micro minerals, which increases nutrient uptake thus increasing the growth rate and overall health of the plant. This is well known to "we in the cannabis-culture". Modern science proves out this ancient ag-cult belief.

As is also well known in agriculture and horticulture, in many plant varieties, high nutrient solution temperatures can and do cause root system oxygen starvation, as well as promote growth of unwanted and harmful pathogens. As the temperature increases, nutrient solution oxygen solubility dramatically decreases and the plant essentially suffocates. Plant injury from hypoxia, low or no oxygen at the roots, may take several forms, each differing in severity and dependent upon the plant family and variety.

Typically, the first sign of root suffocation is overall wilting of the plant shoot during the warmest part of the day when temperatures and light levels are highest, or the overall wilting of plants grown with artificial illumination in controlled conditions. Insufficient oxygen reduces the permeability of roots to water and results in the accumulation of toxins, thus both water and minerals cannot be absorbed in sufficient quantities to support plant growth, particularly under plant stress conditions.

This wilting is accompanied by slower rates of photosynthesis and carbohydrate transfer, and over time plant growth is reduced and crop yields are negatively affected. If oxygen starvation continues, mineral deficiencies in the plant will set-in, roots will die back, and plants will become stunted. Under these continuing anaerobic conditions, plants produce a stress hormone--ethylene--which accumulates in the roots and causes the collapse of root cells. Once root cell injury and deterioration caused by anaerobic conditions has begun, common opportunist pathogens such as pythium, fusarium, verticillium, rizoctonia, and the like, can easily infect and rapidly destroy the plant.

To prevent plant root hypoxia -which in turn prevents pathogen infection and infestation, and to increase nutrient uptake by a plant- intelligently so, the vast majority of canna-cultivators reduce nute solution and grow medium temperatures to between 55-70 degrees F. This indeed will increase solubility making supplementary oxygen bubblers, injectors, and the like much more effective and efficient.

However, this common nutrient temperature reduction while maintaining the plant shoot at higher temperatures is resulting in a condition which is stunting and retarding the growth and development of millions of cannabis plants; from seedlings all the way to old-timers. I call it the FULL NELSON ™; and it's a plant killer...

Most in the canna-cult who keep roots cold and shoots hot don't know of Professor Clarence Nelson, and his work with hemp-sativa plants back in the 1940s. Nelson observed that cannabis placed in a condition where the plant root temperature is maintained below that of the plant shoot... significantly reduced plant growth and production.

As I noted on my canna-cult patent, U.S. 9,622,426:

"In Growth Responses of Hemp to Differential Soil and Air Temperatures, by Clarence H. Nelson, Plant Physiol. 1944 April; 19(2): 294-309, ...Nelson explains that specific development changes occur in C. sativa L. plants grown in such temperature differential environments. Nelson placed C. sativa L. into four unchanged temperature conditions (series), remaining unchanged throughout the vegetative growth phase of the plants. The four temperature conditions Nelson used where:

Shoot at 86.degree. F., and roots at 86.degree. F., (hereinafter "H/H").

Shoot at 86.degree. F., and roots at 60.degree. F., (hereinafter "H/L").

Shoot at 60.degree. F., and roots at 86.degree. F., (hereinafter "L/H").

Shoot at 60.degree. F., and roots at 60.degree. F., (hereinafter "L/L").

The following was observed and concluded by Nelson:

The H/H Plants: Vegetative growth was the most robust, with the smallest internodal length and stem diameter until maturity, and with the greatest root development. Specifically, H/H series plants exhibited the maximum stem elongation; greatest number of nodes produced; earliest blossom and seed formation; least aggregate leaf area; greatest number of leaf abscissions; and the highest absolute water consumption during growth.

The H/L Plants: Both the aggregate number of leaves produced and the total leaf area per plant where smaller than in any other series. The leaves themselves were relatively thin and more finely veined. This series showed the least anabolic efficiency as noted by their low fresh and dry weight per plant. There was a possibility of impaired translocation of reserves into the region below the ground line due to low root temperatures. The FULL NELSON ™

The L/H Plants: Had the maximum stem diameter and greatest internodal length. Leaves were very coarse in texture, large in size, and extremely thick. Leaf abscission was lowest of the four series, and leaf and stem production was favored. Plants of this series had the largest stem diameter, largest individual leaves, and highest aggregate dry weight.

The L/L Plants: The leaves on these plants were relatively large, attaining the maximum area per leaf of the four series. Though the stems attained a height only slightly greater than in the L/H plants, the stem diameter was relatively large. The vegetative habit was essentially similar to L/H plants except as to stem length."

The tragic take-away in all this, reducing root/nutrient temps to 50-70 degrees F while maintaining shoot/gas mixture temps at 70-90 degrees F; where the shoot is about 10 degrees F above that of the root temperature - is starving your cannabis by reduced and slower rates of photosynthesis and carbohydrate transfer- and therefore is costing you time, effort, and money. Maybe a ton...

Most "growth augmentation efforts" such as as high concentration nutrient solutions, increased CO2 and increased corresponding lux/light intensity, and all the other myriad of "trade secrets" used to increase plant growth output and efficiency ARE WASTED, if your cannabis root is colder than your cannabis shoot.

SO - keep your root/nutrient temps within approximately 10 degrees F of your shoot/air-gas mixture temps.

And please, don't keep your shoot temperature below your root temperature without permission or license, or you'll be infringing my U.S. Patent 9,622,426 - and that's not very nice... Rude even. In fact, such is theft of intellectual property. Now, if you'd like to talk shop and possibly collaborate... sounds great.

Now dem is some nice ruts... ~Charles

Root zone temperature.

Posted: Mon Apr 09, 2018 5:32 pm
by Hopefull Stoner
says this : The tragic take-away in all this, reducing root/nutrient temps to 50-70 degrees F while maintaining shoot/gas mixture temps at 70-90 degrees F; where the shoot is about 10 degrees F above that of the root temperature - is starving your cannabis

and this seems to be a contradiction because it is in line with the above guidelines imho.
wtf =SO - keep your root/nutrient temps within approximately 10 degrees F of your shoot/air-gas mixture temps.

Root zone temperature.

Posted: Mon Apr 09, 2018 8:42 pm
by bentech
for years the advise was just cut out foil backed rigid insulation to place between your plants canopy and your buckets...

tons of people did that for years as a matter of course

odd the antithetical observations didn't make it back into the discourse

or did it?

Root zone temperature.

Posted: Thu Apr 12, 2018 8:05 pm
by Dick Fein
I always kept my air pumps hanging from hooks beside the plants for reasons of sound dampening and because of the risk of siphoning during power failures, but in my current garden I had them screwed on the wall outside the garden until I read this.
Since then I moved them back in the grow room.
I go through a lot more nutrients and have to watch my ph drift but I may have been doing the right thing before without knowing exactly why.
When I flower the clones I will do a side by side comparison with a pump inside and a pump outside the room.

Root zone temperature.

Posted: Thu Apr 12, 2018 10:30 pm
by Prawn Connery
Don't forget, the pumps themselves get warm during operation.

Also, let's address the elephant in the room . . .The above experiment was conducted in SOIL. It does not take into account oxygen saturation at the root zone in hydroponics.

Reducing root zone temperatures from 30C to 15C increases dissolved oxygen by almost 50%

Further, the more nutrient in solution, the less dissolved oxygen - up to 20% less in sea water compared to fresh water. Nutrient solution is clearly not as salty as sea water, but the increase in nutrient needed for full flowering coincides with the greatest oxygen demands from the roots.

Raising temperatures from 15C to 30C also increases the growth rate of anaerobic pathogens, such as pythium (root rot), by something like six or seven times.

Finally, the reality is root zone temperatures fluctuate markedly less than air temperatures in nature - soil is an insulator - so root zone and canopy temperatures are rarely the same at any time of the day or night.

I note the experiment did not try using a stabilised root zone temperature with a fluctuating canopy temperature to emulate natural conditions. It would have been interesting to compare.
bentech wrote:for years the advise was just cut out foil backed rigid insulation to place between your plants canopy and your buckets...

tons of people did that for years as a matter of course

odd the antithetical observations didn't make it back into the discourse

or did it?
Wasn't that mostly to do with reflecting light back towards the plant and cutting down on evaporation from the pot? I always thought that was the main reason.

Root zone temperature.

Posted: Fri Apr 13, 2018 5:20 pm
by Dick Fein
I agree you do not want your nutrient solution at 30c but I don't want my room that hot either. At the top of the canopy I am 23 and night temp is 16.
In the summer I may be looking at a different situation.

Root zone temperature.

Posted: Fri Apr 13, 2018 7:36 pm
by MadMoonMan
Plants like to breath oxygen.

If you slept in a room with them they would fall in love with you.

Of course you are all-ready in Love with them or why else would you be sleeping in a room full of marijuana plants?

Doh!

Root zone temperature.

Posted: Fri Apr 13, 2018 7:39 pm
by MadMoonMan
GRRRRR! Found an ant colony nested in one of my flowering Burmese Kush 5 gallon pots.

had to bare root and re-transplant. So far so good. Rough up the girl a lot but she is hardy. she is in 1st month of flowering end of and gorgeous.

So far so good watering well kissing often ... no wilt ...

Root zone temperature.

Posted: Fri Apr 13, 2018 9:11 pm
by Dick Fein
bentech wrote:for years the advise was just cut out foil backed rigid insulation to place between your plants canopy and your buckets...

tons of people did that for years as a matter of course

odd the antithetical observations didn't make it back into the discourse

or did it?
I never used foil but did have all my clones poking through a sheet of black and white poly. It was always a pain in the ass and why I quit SOG.

Root zone temperature.

Posted: Fri Apr 13, 2018 11:38 pm
by Prawn Connery
Dick Fein wrote:I agree you do not want your nutrient solution at 30c but I don't want my room that hot either. At the top of the canopy I am 23 and night temp is 16.
In the summer I may be looking at a different situation.
Mine regularly gets over 30C, which is why I switched from DWC coco.