Optimum Nutrient Levels for Cannabis. A Scientific Study

A scientific study was published in November 2021 about the optimum amount of nutrients for Cannabis.

Increased K had no effect on inflorescence yield. 30 mg/L did not show deficiency nor did 340mg/L indicate toxicity. The study suggests that many commercial fertilizers supplied far too much K.

"The lack of response to K in the range of 60-340 mg/L observed in our trial may be partially due to competition for uptake from Ca"

P levels above 30mg/L ; the excess was sequestered in the root tissue. The paper indicated that 59 mg/L was optimum

The study openly states that N supplied at 194 mg/L was for optimum yield.

The study stated that there is an inverse relationship between yield and potency meaning that higher yield meant lower potency.



A must read.

Cpl. Cadaver said:

The study stated that there is an inverse relationship between yield and potency meaning that higher yield meant lower potency.

Click to expand...

I've wondered about this because I've read that this plays a role in fruits and vegetables lacking the flavor they had in years past. You pump up the volume but not the substance.

Potassium in plants has a key function to control the internal water-content, this is why e.g. tomato-fert is high in K for flower, that tomato has just so much water. Cannabis achene not at all... and then there is this antagonism between K & many other Kations...

thanks for posting this!

5g of DynaGro Bloom and 3.5g of CaNO3 per gallon puts you close to their "optimum" NPK at 183ppm N, 69 ppm P, and 66 ppm K, according to the version of Renfro's spreadsheet I have.

Observe & Report said:

thanks for posting this!

5g of DynaGro Bloom and 3.5g of CaNO3 per gallon puts you close to their "optimum" NPK at 183ppm N, 69 ppm P, and 66 ppm K, according to the version of Renfro's spreadsheet I have.

Click to expand...

Just curious... not argumentative.. My DynaGro literature, I received from them, all measures are in ml, not g. What is the conversion? For pure water, it is 1:1. Do you think I can use the same conversion? Would you mind sharing your Renfro sheet? thnx

Cpl. Cadaver said:

A scientific study was published in November 2021 about the optimum amount of nutrients for Cannabis.

Increased K had no effect on inflorescence yield. 30 mg/L did not show deficiency nor did 340mg/L indicate toxicity. The study suggests that many commercial fertilizers supplied far too much K.

"The lack of response to K in the range of 60-340 mg/L observed in our trial may be partially due to competition for uptake from Ca"

P levels above 30mg/L ; the excess was sequestered in the root tissue. The paper indicated that 59 mg/L was optimum

The study openly states that N supplied at 194 mg/L was for optimum yield.

The study stated that there is an inverse relationship between yield and potency meaning that higher yield meant lower potency.



A must read.

Frontiers | Optimisation of Nitrogen, Phosphorus, and Potassium for Soilless Production of Cannabis sativa in the Flowering Stage Using Response Surface Analysis

Following legalisation, cannabis has quickly become an important horticultural crop in Canada and increasingly so in other parts of the world. However, due t...

www.frontiersin.org

Click to expand...

Interesting. I have used boosters in the past( koolbloom) etc and noticed a difference both in yield and potency. More yield, slightly less potency but noticeable amount. These days I don’t use those products for that exact reason. I could care less about yield, but I care a hella lot about potency.

sunsetair said:

... Would you mind sharing your Renfro sheet? thnx

Click to expand...

I had a similar question, searched and found this thread by Renfro.

simpleleaf said:

I had a similar question, searched and found this thread by Renfro.

Understanding and Calculating Nutrient PPM

Understanding and Calculating Nutrient PPM PPM (Parts Per Million) can seem like a mystery but it’s actually very simple. Basically the idea is to quantify how much “stuff” is in your water. PPM is commonly measured by a grower using an electronic pen which measures the electrical conductivity...

www.rollitup.org

Click to expand...

Oh lord. I don't want to grow Arnold S. I want to grow a weed. This write up reminds me the budybuilding journal nutrition section.

Fardsnarp said:

I've wondered about this because I've read that this plays a role in fruits and vegetables lacking the flavor they had in years past. You pump up the volume but not the substance.

Click to expand...

100% this. I think this more so applies to commercial grows and dispensaries where they specifically only grow cultivars for their ability to produce yield over flavour and effect! Talk about compounding the issue. So not only are you starting off with a seed/plant that sacrifices quality for quantity, they are also grown and fed in such ways to promote yield as the ultimate end goal.

There's a reason why Michelin star restaurants source their vegetables from local small owned farms most of the time. They don't shoot for yield or size, they shoot for quality and taste.

sunsetair said:

Just curious... not argumentative.. My DynaGro literature, I received from them, all measures are in ml, not g. What is the conversion? For pure water, it is 1:1. Do you think I can use the same conversion?

Click to expand...

NPK and guaranteed analysis are all done by weight so that's what the spreadsheet does. You have to weigh it to figure out the exact dilution. I'm measuring about 1.3g/ml of DG Bloom. YMMV.

Cpl. Cadaver said:

The study stated that there is an inverse relationship between yield and potency meaning that higher yield meant lower potency.

Click to expand...

In this experiment the potency was the same for all treatments. Other experiments only found a drop at the highest rates of fertilizer application. In one referenced experiment, the concentration was 20% lower at the highest N rate but overall yield was doubled.

this is the relevant paragraph, emphasis added by Yours Truly

While the cannabinoid concentrations in the floral tissues in our study did not respond to nutrient solution NPK concentrations, other studies indicate that plant mineral nutrition can affect production of secondary metabolites in cannabis (Caplan et al., 2017a; Saloner and Bernstein, 2021). There appears to be an inverse relationship between cannabis yield and potency, with cannabinoid concentrations decreasing as plant inflorescence yield increases. Inflorescence from plants supplied with 160 mg L–1N had approximately 30 and 20% lower concentrations of THCA and CBDA than plants supplied with 30 mg L–1N (Saloner and Bernstein, 2021). However, while nutrient stress and deficiency may enhance inflorescence cannabinoid content, this method is not ideal for optimising overall plant productivity as plants supplied with 160 mg L–1 N yielded twice that of those supplied with 30 mg L–1N. Cannabis grown in two organic growing media with different organic fertiliser rates (i.e., 57, 113, 170, 226, and 283 mg L–1N) had negative linear relationships between the concentrations of inflorescence THCA and CBGA and the fertiliser application rate for some of the treatment combinations (i.e., growing media and fertiliser rate) (Caplan et al., 2017a). However, for the most of the treatment combinations, fertiliser rates from 57 to 226 mg L–1N did not have any effects on THCA or CBGA concentrations; and the cannabinoid concentrations only dropped when the fertiliser rate increased to the highest level of 283 mg L–1N. The context of yield is again important when analysing differences in cannabinoid content as THCA concentrations dropped by ∼20% in the highest fertiliser rate, but inflorescence yield almost doubled vs. lowest fertiliser rate.

Click to expand...

they go on to say more research is needed, of course

Observe & Report said:

In this experiment the potency was the same for all treatments. Other experiments only found a drop at the highest rates of fertilizer application. In one referenced experiment, the concentration was 20% lower at the highest N rate but overall yield was doubled.

this is the relevant paragraph, emphasis added by Yours Truly


they go on to say more research is needed, of course

Click to expand...

The context of yield is again important when analysing differences in cannabinoid content as THCA concentrations dropped by ∼20% in the highest fertiliser rate, but inflorescence yield almost doubled vs. lowest fertiliser rate. As noted by Bernstein et al. (2019), an understanding of how nutrient supply influences cannabinoid concentrations would be an important step towards controlling and standardising the cannabinoid contents of medical cannabis. Cannabinoid concentrations are also important to recreational consumers, who rank THC and CBD concentrations among the most important factors when making purchasing decisions (Zhu et al., 2020). (Bold Emphasis Mine)

The goal of this study was to determine the optimal concentration of N, P, and K in the nutrient solution for the flowering stage of soilless cannabis production using RSM.

The overall purpose of the study was to find optimum levels of nutrients so to avoid environmental waste such as excess levels of "K". More efficient use of nutrients means lower costs to growers and better buds. (italics Mine)

No one is going to argue that growers have been using nutrient solutions that aren't optimized for buds. Obviously MasterBlend isn't suitable for cannabis as it has far too much "K". The other One Size Fits All nutrient solutions aren't optimized for cannabis either. From the papers I have been reading it is obvious that MasterBlend isn't suitable for tomatoes either.

Isn't this exciting? We growers now have a starting point established from scientific research.

Better buds through science! My Phosphorus is arriving today and I can finally transplant my Critical Mass into DWC and grow it in a solution demonstrated by the scientific community to be overall optimal. No more wondering if the premixed formulas are going to work. I am giddy with anticipation.

Can anyone forward this to Dr. Who? I am sure he would appreciate the info presented in the paper. Google Scholar is your friend.

Cpl. Cadaver said:

... Obviously MasterBlend isn't suitable for cannabis as it has far too much "K". ...

Click to expand...

You're supposed to mix MasterBlend with Calnit and MgSO4 for the classic formula. It's not as cut and dried as the NPK on the label of a single ingredient. I took it a little further than that, as I quickly realized I didn't have to use the recommended by MB ratios, and could devise my own similar ones, thus tweaking the NPK.

I'm now at a point, finally, where I believe I could phase out MB entirely and still have all the needed micros and minors, but I see no need to do so, I have half lb of it on hand, why not use it?

simpleleaf said:

You're supposed to mix MasterBlend with Calnit and MgSO4 for the classic formula. It's not as cut and dried as the NPK on the label of a single ingredient. I took it a little farther than that, as I quickly realized I didn't have to use the recommended by MB ratios, and could devise my own similar ones, thus tweaking the NPK.

I'm now at a point, finally, where I believe I could phase out MB entirely and still have all the needed micros and minors, but I see no need to do so, I have half lb of it on hand, why not use it?

Click to expand...

You are free to use whatever you wish just as I am free to disagree with your methods. I'm using Flora Nova Grow as a base for my tomatoes and Flora Micro as a base for my weed. At 8ml/gal Flora Micro gives me the micronutrients in quantities I want without exceeding optimum N-P-K. I can't do that with Masterblend. Too much potassium doesn't have any effect on yield but does have serious negative effects on THC production. Since there isn't much research on the Micronutrients and their effects and I don't want to risk a deficiency from the start so I am keeping the micronutrients at a level I am certain is not nutrient deficient. I'm supplementing with RAW industries Nitrogen, Phosphorus, Potassium Chloride and epsom salts.

I have used MasterBlend for my bell peppers with good results. I don't think it is suitable for weed as a nutrient solution simply due to the volume of Potassium. I think that the whole 4-18-38 was just a marketing gimmick of "More is Better". I'll believe the scientists over the marketing department.
Get high as a kite and make stuffed bell peppers. That sounds like a plan.

For cannabis I'd use the 5-11-26 and calcium nitrate if using Masterblend. I don't but that would be comparable to Jacks 5-12-26 used for the 3-2-1 which many use very successfully.

While there are no published studies examining the effect of K on inflorescence quality, some recent studies have looked at how K impacts inflorescence yield. Yield of aquaponically grown cannabis (g/plant) increased linearly with increasing nutrient solution K concentration in the range of 15–150 mg L–1 (Yep and Zheng, 2020). The nitrogen concentration (75 mg L–1) used by Yep and Zheng (2020) reflects that of a typical aquaponic solution, but this N concentration is fairly low compared to conventional hydroponic nutrient solutions and may have been a limiting factor for plant growth and yield (Yep et al., 2020b). For the vegetative stage, cannabis plants supplied with 15 mg L–1K had reduced growth and displayed foliar symptoms characteristic of K deficiency, while plants that received 60–240 mg L–1 K produced substantially more biomass and did not display K deficiency symptoms (Saloner et al., 2019). Although there is a lack of recommendations based on scientific research, some fertiliser companies are recommending 300–400 mg L–1K. More research is needed to determine the optimal nutrient solution K concentration during cannabis flowering in soilless production systems when other nutrient elements are not limiting.

i got this from the article

A scientific study has shown that high levels of "K" interfere with the uptake of Ca and Mg.


TL;DR
Reduction in Ca concentration in the plants under high K supply (Figure 3E), points at competition for uptake. Ca/K competition for root uptake (Johansen et al., 1968; Maas, 1969) and a resulting reduced Ca concentration in the shoot was documented for a variety of plant species (Fageria, 2001). Moreover, in-planta transport of these two ions is also competitive since high K concentrations decreased the amount of Ca arriving to the foliage, as already seen before (Overstreet et al., 1952; Bar-Tal and Pressman, 1996).

...while plants that received 60–240 mg L–1 K produced substantially more biomass and did not display K deficiency symptoms.

There appears to be an inverse relationship between cannabis yield and potency, with cannabinoid concentrations decreasing as plant inflorescence yield increases. Inflorescence from plants supplied with 160 mg L−1 N had approximately 30 and 20% lower concentrations of THCA and CBDA than plants supplied with 30 mg L−1 N (Saloner and Bernstein, 2021).

The context of yield is again important when analysing differences in cannabinoid content as THCA concentrations dropped by ∼20% in the highest fertiliser rate, but inflorescence yield almost doubled vs. lowest fertiliser rate.

It has been shown that high "K" interferes with the uptake of Mg and Ca so more "K" causes more problems than it solves. I have two white widow plants in solution and I am keeping the "K" to approx 59 ppm with the "P" at 58-59ppm and "N" at 195ppm. Interestingly enough this also keeps the ratios in line suggested with some observations. K:Mg 1:1. P:K 1:1. Ca:Mg 2:1. My formulation isn't perfect with the Mg:Ca amounts but close enough to get the prize.

Cpl. Cadaver said:

I have two white widow plants in solution and I am keeping the "K" to approx 59 ppm with the "P" at 58-59ppm and "N" at 195ppm.

Click to expand...

what nute(s) are you using to achieve it?

from what @Observe & Report mentioned, you can achieve that ratio with DG Bloom and Cal/Nit. i have both on hand and wanted to try this formula. i'm a bit worried about 19% Ca + 2% Ca in the calnit and dg bloom plus what my well water contains? will that be too much Ca overall? any ideas?

Do you have a water analysis of your well water so you can take it into account?

Fardsnarp said:

Do you have a water analysis of your well water so you can take it into account?

Click to expand...

yes.