The Medical Cannabis response to NPK during Veg

[bruno12345]

How are you doing?

Found these 3 interesting articles. A series named:

Response of medical cannabis (Cannabis sativa L.) to nitrogen supply under long photoperiod 2020 Ncbi link to the article​

Response of medical cannabis (Cannabis sativa L.) genotypes to P supply under long photoperiod: Functional phenotyping and the ionome 2021 - Sci Hub link to the article

Response of medical cannabis (Cannabis sativa L.) genotypes to K supply under long photoperiod 2019 Frontiers link to the article​

They are produced by the Israeli Institute of Soil, using two israeli strains of medical cannabis. High Cbd Low Thc/ Equivalent THC and CBD strain.

Im not an agronomist, but the articles are a good read.

Main findings:
30ppm/L of P is a good ammount during veg phase. More than that can impact gas exchanges, and Zn on leaves. Although, at the highest tested dose of 90ppm, no major issues were found (but effects on growth could possibly happen in a longer veg cycle, or with higher doses of P).

160ppm for N is a good amount during veg phase (talking about soluble N, maybe not appliable for slow release organic fertilizers). Pigments on the leaves impact directly photosynthesis (you know that good old dark green is awesome). But overdosing for N, altough not changing leaf color, reduced plant biomass, and directly impacted the roots.

More effects on plant toxicity of excess N its discussed on the article.
I believe this 160ppm of N, on a established cutting or seedling, is near many commercial formulas PPMs.

Optimal potassium is strain dependent, but a medium ppm of 100 seems suitable, regarding Ca competition and overall plant growth. Some strains can benefit of higher K doses, producing more biomass.

Mostly a general purpose 3-1-2 Npk to 3-1-3 or 4-1-3 are potential good ratios for cannabis fertilizing during veg phase.


Science extra:

Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.)​

Highlights

•N Supply affects cannabinoid and terpenoid concentrations in medical cannabis.​

•Tetrahydrocannabinolic acid and cannabidiolic acid decrease with the increase in N application.​

•The optimal N level for yield quantity, combined with relatively high secondary metabolite content, is 160 mg L−1 N.

Couldnt access the complete article to investigate the graphic, to see the correct relation of N and THC and CBD concentrations.
It is said that a 30ppm of N can concentrate the cannabinoids on buds, at the expense of Yield, and a 160mg of Nitrogen (similar to vegging phase), can balance yield with a relatively high cannabinoids content.

Feel free to comment, analyze or criticize.

 

[InTheShed]

Interesting info bruno, thanks for posting it! I've often heard that pumping up the nitrogen will give you really leafy flowers with fewer bracts, which would be confirmed by the article you posted about nitrogen and THC. I'm going to read through the P and K articles this weekend.

Keeping the phosphorus low (and a lot lower than most nute sellers are selling us) is confirmed by the tissue analysis charts below.

This is a pdf with plant analysis charts and graphs (with full detailed lab analysis) done on the macro and micronutrients found in three different strains of cannabis plant during veg and flower.

The varieties and analysis are from 2003, but I don't think we have modified the plant in the last 17 years to the extent that the nutrient results would vary that greatly today. Here are screenshots of the first three graphs:

What is most interesting, besides the continued need for nitrogen in flower, is how little phosphorus the plants are using compared to nitrogen and potassium.

I'm trying to run close to 5-1-5 from beginning to end on my current grows, using the lower leaves as a gauge to the plant's nitrogen needs as basis for increasing the concentrations.

 

[bruno12345]

Thanks for the reply!
Yeah, comercial brands are intoxicating our plants with high doses of phosphorus. The good news is plants have self regulating mechanisms for P concentrations, sending them to roots and avoiding toxic effects. But this effect has a limit.

Its not uncommon to see people using 2-8-4 fertilizers. And those brands are being sold as special cannabis fertilizers. they are not!

Still plenty to investigate for rooting of seedlings and initial flowering burst. Maybe P could have a special effect in those moments.

I believe your 5-1-5 fertilizer could Go the entire cycle and yield ALOT.

 

[Diatomacious]

Would love to see more data points between 160 and 200.

 

[bruno12345]

Would love to see more data points between 160 and 200.

I do believe some plants would respond better when nearing the 200 mark.
Nutrient matters series argue that, during initial flowering stretch, one should increase P and N.
N to around 200-220.
And during veg and initial flowering between 160-200.

 

[Diatomacious]

I do believe some plants would respond better when nearing the 200 mark.

Could be... would have been nice to see the result from a laboratory analysis where the conditions are controlled and you could be sure only the N value was different. Hard to say what is happening as you approach the 200 value with the data presented. They jump straight from 160 to 240 so only linear interpolation between those 2 points which does not really display an accurate assessment of exactly where the "point of diminishing return" lies.

 

[Diatomacious]

Interesting they say that some strains can handle more potassium than others and actually have a different nutrient concentration requirement for K.

 

[Diatomacious]

Chemical nutes are just a "soil simulation" some scientist cooked up in a lab somewhere anyway.

 

[Diatomacious]

Would love to see more data points between 160 and 200.

Would also help establish a range for the most optimal concentration. Very useful for organic amending where it's sometimes hard to tell exactly the ppm's.

 

[bruno12345]

Good day cannabis lovers.

Another article regarding nutrition. (still in preprint condition).

Optimization of N, P, K for soilless production of Cannabis sativa in
the flowering stage using response surface analysis
By:
Lewys Bevan1, Max Jones2, and Youbin Zheng1*

Now during flowering.
And now with changing ammounts of N P K and their relations inbetween.

Other articles were produced with variating macronutrient concentration, while the other 2 macronutrients were static.
This one relates changing concentrations of 3 macronutrients and their relations.

Was done in DWC.

Found optimum P for growth in flowering of 60PPM.
Loss of yield when below 40 and higher than 80.
Extra: Bruce bugbee says buds were found to be sinks for phosphorus, consuming this element as they mature. Maybe thats why we should double the concentration of the recommended for veg period (30PPM P for veg).

Some commercial fertilizers recommend absurd 200PPM of P.

Optinum N of 194PPM - optimum yield under 160 to 220PPM of N.

K at the highest concentration (340PPM), and at the lowest (60PPM), no deficiency or excess achieved. No effect on yield.

Also gives us light on the article that says N regulates yield and cannabinoid concentration.
30PPM of N produces 20 to 30% more concentrated buds, but loses half of the yield of 160PPM of N.

Thats why they recommend working with N levels that are very close to vegetating period.

Our cannabis strains are getting more and more potent, i believe exchanging 20% cannabinoid concentration for 100% more yield is a good exchange. Also for oil producers, will give a higher total cannabinoid yield.

Limitations:
Only one genetic tested.
Only macronutrients tested, static Calcium and Static Mg.
Only DWC used.
No terpenes or organoleptic characteristics were tested.

But should give us a good direction into phosphorus fertilization during flowering.

In annex, a graphic showing the relation between N and P for yield production.

Link for the article for the science lovers.: Optimization of N, P, K for Soilless Production of Cannabis sativa in the Flowering Stage Using Response Surface Analysis

 

[InTheShed]

Great info, thanks @bruno12345!

Found optimum P for growth in flowering of 60PPM.

Noted!

Some commercial fertilizers recommend absurd 200PPM of P.

I know right? Crazy what passes for science in the nutrient manufacturing space.

K at the highest concentration (340PPM), and at the lowest (60PPM), no deficiency or excess achieved. No effect on yield.

That's an interesting piece of information for sure, and certainly goes against what I've read before. Potassium has no effect on yield between 60 and 340ppm? I would also think you would lock out a few other nutrients at 340ppm.

@farside05 @MrSauga might want to take a peek here!

30PPM of N produces 20 to 30% more concentrated buds, but loses half of the yield of 160PPM of N.

Do they say what they mean by "concentrated"? I find it hard to believe that a plant will get through flower on 30ppm of N. I would definitely want to double my yield over some undefined increase in "concentration"!

 

[MrSauga]

@farside05 @MrSauga might want to take a peek here!

I haven't the time to read it all now, but maybe there is a difference in running those numbers in DWC. I can't see some of the numbers working, although the data is there, apparently, to support it.
Too bad there were no pics of the plants. All that work and not one image to show their results.

 

[farside05]

My current low P grow is under 20ppm. So here we have someone saying 60ppm. That's greater than a 3:1 relationship to N and AN's old tissue samples don't support that. So I guess it all comes down to who's data you want to believe/trust. I can say I'm not seeing much difference between my previous grow that was closer to 40ppm of P with the same strains.

 

[InTheShed]

All that work and not one image to show their results.

My current low P grow is under 20ppm. So here we have someone saying 60ppm. That's greater than a 3:1 relationship to N and AN's old tissue samples don't support that. So I guess it all comes down to who's data you want to believe/trust. I can say I'm not seeing much difference between my previous grow that was closer to 40ppm of P with the same strains.

And y'all's real-life results certainly make it look like you don't need 60ppm of phosphorus for happy plants!

 

[bruno12345]

Well, from my point of view:
Potassium is strain dependent
I would work It around 150-200.
Even though their plants did well in 60ppm, It is known that some strains benefit from higher K. But still an interesting finding.

Well, Bruce bugbee Said his friend researcher found buds to be sinks for P. They take a Lot of It and Just hold It in form of an acid.

These optimal concentrations are for yield boosting, not for health boosting.
You can definitely work with lower P and still have healthy plants.

Give It a try in some clones, working around 40 to 80ppm, and others bellow 30, see How It goes, altough we hardly Will have a consistent enviroment as a laboratory.

Great info, thanks @bruno12345!

Noted!

I know right? Crazy what passes for science in the nutrient manufacturing space.

That's an interesting piece of information for sure, and certainly goes against what I've read before. Potassium has no effect on yield between 60 and 340ppm? I would also think you would lock out a few other nutrients at 340ppm.

@farside05 @MrSauga might want to take a peek here!

Do they say what they mean by "concentrated"? I find it hard to believe that a plant will get through flower on 30ppm of N. I would definitely want to double my yield over some undefined increase in "concentration"!

The concentration effect is like this:

When we raise N to around 160PPM we have twice the yield VS 30PPM N.

But 30PPM N buds Will have 20 to 30% more cannabinoids.

Raising nutrition gives a "dilution effect" on the buds, also noted on other oil producing plants.

Example:
30PPM N - 25% THC - 50grams yield.
160PPM N - 20%THC - 100 grams yield.

Flushing is being studied, and It seems It also "concentrate" the buds, in preliminar findings (Bruce bugbee). Also at the price of some yield.

 

[InTheShed]

I'd much rather have 100g of 20% THC bud!

Also, flushing has been studied extensively in controlled settings:

 

[bruno12345]

I want to also note that this last article, still a preprint, but produced in one of the most recognized university agronomic departaments of the world. From Canada.

 

[bruno12345]

I'd much rather have 100g of 20% THC bud!

Also, flushing has been studied extensively in controlled settings:

Well me too!
Our genetics are already filled with lots of cannabinoids, more potent than ver before. Give me yield!!!!!!! Hehehe

 

[MrSauga]

And y'all's real-life results certainly make it look like you don't need 60ppm of phosphorus for happy plants!

I believe there's more negative benefits to having too much P in a plant. It's not that I doubt the data in the paper, but it's hard to jump onboard when there's no evidence to support the data.

The image below shows the response of Alternanthera to increasing concentrations of P from 0, 5, 10, 20 and 40 ppm (left to right).

You can see the growth slowed after 10 ppm and basically stopped after 20 ppm. Phosphorus is also the primary contributor to plant stretch. Too much P will lead to excessive internode elongation and tall plants. That’s why it’s important to limit excessive P in grow applications.

This most likely can be applied to all plants; the author used it as a comparison to cannabis.

 

[bruno12345]

I believe there's more negative benefits to having too much P in a plant. It's not that I doubt the data in the paper, but it's hard to jump onboard when there's no evidence to support the data.

The image below shows the response of Alternanthera to increasing concentrations of P from 0, 5, 10, 20 and 40 ppm (left to right).

You can see the growth slowed after 10 ppm and basically stopped after 20 ppm. Phosphorus is also the primary contributor to plant stretch. Too much P will lead to excessive internode elongation and tall plants. That’s why it’s important to limit excessive P in grow applications.

This most likely can be applied to all plants; the author used it as a comparison to cannabis.

This is simply not comparable to the last article.

Not only these are different species, but different period of growing.

Vegetative state P was already studied, and yes, its pretty much similar to this plant in the image. 15 to 30PPM seems alright, damn you could even go below this and have pretty plants (look for the veg P article in the start of this post).

What do you mean no evidence to support the data? Youre using another species data, from veg period, to discuss flowering of cannabis. And this Cannabis specific article, from a Internationally renowned agronomic department of University of Guelph, seems to you as "no evidence to support the data"?

Sorry, i just cant understand the logic of what youre saying.

As i said, there is an important factor regarding Cannabis flowering and P.
Buds are Sinks for P. They store it. They consume it.

You cant compare it with a vegetative period study.