sam's thunk:
Works every time.
Works every time.
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interesting study on cloning
- Thread starter ramse
- Start date
I’ve had males root in water when I cut flower tops to ripen and collect pollen. Actually revegged one but it took a long time and work.
Always afraid to do regular clones in water because of rot.
Always afraid to do regular clones in water because of rot.
Somatek
Active member
That was my initial reaction, it's unimpressive they're only getting a 70% success rate but then I stepped back and realised it'd be foolish to dismiss it just because it doesn't match my experience.
Since changing I've had quicker success and more importantly better root formation (not measured, purely observed). If you've created the right environment for 100% success, trying their way will probably just speed it up or give you denser roots.
I run a perpetual garden, so I'm always snipping clones and it was easy to test side by side. It's worth challenging your assumptions as it's improved my grow.
Veggia farmer
Well-known member
two subjects here now.. Nice to here about experiments
had something say about cloning but forgot it after the drought subject came up..
Drought will effect the potency level ? Cacit works like that and some other herbs I think.. Espescially the plants that like sandy soil. Cannabis is natually sandy loam. Riverbanks I believe I have heard about.
container cap. what substrat? Bigger but looser?
had something say about cloning but forgot it after the drought subject came up..Drought will effect the potency level ? Cacit works like that and some other herbs I think.. Espescially the plants that like sandy soil. Cannabis is natually sandy loam. Riverbanks I believe I have heard about.
container cap. what substrat? Bigger but looser?
I agree. Its funny how we as a culture we take on practices and these practices are seen as must do and then bam along comes a proper study. The thing is though I have always got 100 percent strike rates in about 10 - 12 days by cutting some leaf material so while I can't improve strike rates perhaps as you say I can improve root quality.
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two subjects here now.. Nice to here about experiments
Drought will effect the potency level ? Cacit works like that and some other herbs I think.. Espescially the plants that like sandy soil. Cannabis is natually sandy loam. Riverbanks I believe I have heard about.
container cap. what substrat? Bigger but looser?
Yep they have just confirmed what hippies believed in the 60's. If you subject a plant to stress of any kind it produces more resin as part of the defense to this stress. Nothing new here but it is great to see that science is now confirming very old beliefs and practices that a lot of more advanced growers use to maximise quality. I'm really looking forward to seeing more on this type of thing. E.g. light colour spectrum and quality etc.
Somatek
Active member
If you read the full paper it's really looking at optimal irrigation strategies for keeping costs down, testing the cannabinoids was just to see if quality suffered more then testing if it specifucally raised them. So while properly irrigated crops produced slightly more then those that experienced water stress the difference was negligible and they achieved a 47% water reduction with draught. So for the slight yield increase it doesn't justify the added expense, especially as I believe the draught crops produced as much or more cannabinoids.
It also looked at flushing and found there was no reduction of nutrients in the plant matter comparing the flushed vs control crops. Challenging another long held assumption in the community.
https://atrium.lib.uoguelph.ca/xmlui/handle/10214/12125
I'm also looking forward to seeing what their research discovers, it's a local university that's focused on Ag and is currently building a plant lab specifically to study pot. Exciting times to be alive, I hope they study things like defoliation to show one way or the other if it's effective.
Absolutely on defoliation although I think they will find it is effective with a whole bunch of considerations such as genetics, nutrient adjustments, level and timing of defoliation etc. Certainly studies have already been done on other dicots that demonstrate that some defoliation increases flower and fruit yield. And yes I have seen the flushing study - no surprises there for me.
On the drought stress - conclusion was
Drought increased the concentration of major cannabinoids tetrahydrocannabinol acid (THCA) and cannabidiolic acid (CBDA) by 12% and 13%, respectively, compared to the control. Further, yield per unit growing area of THCA was 43% higher than the control, CBDA yield was 47% higher, Δ9-tetrahydrocannabinol (THC) yield was 50% higher and cannabidiol (CBD) yield was 67% higher. Controlled drought stress may therefore be an effective horticultural management technique to maximize both floral weight and cannabinoid yield in cannabis, although results may differ with cannabis cultivar or chemotype.
Interesting. But how does drought differ from a wet dry cycle. Typically you don’t water until the pot dries out. You generally wait until it’s light but not so much you’ll hurt the roots.
Are we talking literally let the pot sit dry for an extended period. 1 hour...6 hours...
Are we talking literally let the pot sit dry for an extended period. 1 hour...6 hours...
Best to read the paper very carefully. Definitely a high risk practice that should be approached with great care.
I have been testing coco DTW plants with dry-ish medium conditions
the last weeks of flower and will agree that flowering plants in coco with
moist vs wet is yielding better smoking yields.
Your mileage will vary, natch.
the last weeks of flower and will agree that flowering plants in coco with
moist vs wet is yielding better smoking yields.
Your mileage will vary, natch.
Somatek
Active member
Were those results consistent? I thought the results varied and they concluded the effect was in relation to pot size.
The paper I linked conpared 3 crops; 2 saw a reduction in cannabinoids & 1 increased, the yields were slightly lower in 2 but the same (possibly slightly higher) in the 3rd. Which is what I was basing my comment on, the results don't seem to be conclusive but they have consistently found the difference to be negligible compared to the water savings. Sorry if I wasn't clear and seemed to be contradicting you instead of elaborating on the one studies results.
Somatek
Active member
No, if you read the full paper their creating and controlling the water stress by measuring VPD and other metrics to gauge 2 different levels of water availability. Essentially it's just a much more controlled version of maintaining a good wet dry cycle. It's worth reading the whole paper and looking at the data, but at this point it seems to reinforce both arguments; optimal watering usually yields a bit more but from a purely economic viewpoint slight water stress is more cost effective at large scale.
All good chap I didn’t take it as you were contradicting me.
I expect you will find this is because of the air to water relatioship in the substrate. The thesis goes through this also finding that higher numbers of irrigations in a well aerated coir substrate yielded better than fewer irrigations in a substrate with lower air capacity.
Hey just quickly on this the point of introduing drought stress in the study was based on well known science that drought stress increases oil production in medicinal crops so the hypothesis began at by inducing drought stress it is feasible we can increase THC etc percentage in cannabis.
i.e. from paper
Drought stress is a major stimulator of secondary metabolites in plants. This is exemplified in herbs and spices cultivated in semi-arid regions such as the Mediterranean. Intermittent drought 89
and high solar radiation in these areas has been attributed to aromatic herbs and spices with abundant essential oil (Kleinwächter and Selmar, 2015). In the literature, there are no reports on the effects of drought stress in cannabis; however, secondary metabolite accumulation due to drought stress has been documented in a number of other herbaceous species (Baher et al., 2002; Bettaieb et al., 2009; Kleinwächter and Selmar, 2015). In Summer savory (Satureja hortensis), plants that were highly drought stressed during the flowering stage had 31% higher essential oil concentration than a well-watered control (Baher et al., 2002). Likewise, drought stress increased essential oil concentration in lemon balm (Melissa officinalis L.) and lemon catmint (Nepeta cataria L. f. citriodora) compared to a well-watered control but did not for sage (Salvia officinalis L.). Though concentrations were higher, essential oil yield (by growing area) of lemon catmint and lemon balm was lower in the drought-stressed plants because of reduced growth and harvestable plant material.
Another hypothesis they wanted to test was: "Drought stress timing is also essential to minimize yield losses and maximize essential oil yield and the concentration of secondary metabolites; differences in growth stage and natural timing of phytochemical accumulation must be considered by species (Petropoulos et al., 2004)."
Finding was
Yield and cannabinoids
Yield in the control was 178 ± 9.4 g·m-2 and was 232 ± 18.5 g·m-2 in the drought treatment but yield did not differ statistically between the two treatments (P = 0.06; n = 3). The moisture content of the dried and cured floral material was 8 ± 0.1 % in the control, 11% lower than that in the drought treatment, at 9 ± 0.1 % (P = 0.01; n = 3). Henceforward, the floral dry weight and cannabinoid contents are corrected to zero percent moisture.
Of the analyzed cannabinoids, all were detected in at least one sample, these included: THC, THCA, CBD, CBDA, CBG, CBGA, and CBN. In the drought treatment, only one sample had a detectable concentration of CBG and CBN, and in the control there were no samples with detectable CBN; therefore, comparisons could not be made for these cannabinoids, and the means for CBN were not presented.
The drought treatment elicited a 12% increase in THCA concentration and a 13% increase in CBDA concentration but had no effect on the concentrations of the other detected cannabinoids
98
(Table 5.3, top). Drought had substantial effects on cannabinoid yield, expressed as grams of cannabinoid from floral material per unit growing area (g·m-2). In the drought treatment, THC yield was 50% higher, THCA yield was 43% higher, CBD yield was 67% higher, and CBDA yield was 47% higher than in the control (Table 5.3, bottom).
Conclusion equals
Discussion
The controlled drought treatment used in this study substantially increased the concentrations of both major cannabinoids, THCA and CBDA as well as yield of THCA, CBDA, THC, and CBD compared to the control. These results suggest that the level of drought stress applied in the present study was adequate to stimulate cannabinoid production without reducing yield for this cultivar.
So no the hypothesis that drought stress could be used to improve oil yields was demonstrated. Also the hypothesis that if drought stress was implemented correctly yield losses (re harvested dried product) may not result was also demonstated.
Look over the paper more carefully - I think you might find you've misread/misinterpreted the data.. I wanted to go back to it myself to look more closely before commenting further.
