The Medical Cannabis response to NPK during Veg

[farside05]

Looking at Table 3 from the PDF file, I have a few issues:

TABLE 3.jpg

• farside05
• Oct 4, 2021

They are supposedly testing the 3 macros at 5 different ppm levels (from Table 2). That's 125 different possible combinations. They did 20, that's 16% of the total possibilities. 10 of the 20 tests utilized180ppm N, 60ppm P, and 200 ppm K in some combination. Seems to me that they had a preconceived notion on those particular numbers since they chose them in much higher frequency than the other possibilities.

In 13 of the 20 instance, ppm of Ca was 130. The other 7 instances it was even greater. I'm not familiar with any fertilizer product line that has that high of Ca.

Sulfur was 180ppm in all 20 instances. Holy Shit Batman, that's A LOT of S! Like with Ca, I know of no product line that has that much S.

 

[InTheShed]

Thanks farside! And I wonder why change the ppm of chlorine so drastically? 5, 95, 190ppm? If they only tested macronutrients and were supposed to be static for Ca and Mg, then why does Ca bounce around as well as the wildly different Cl numbers? That makes for 5 variables.

 

[farside05]

Thanks farside! And I wonder why change the ppm of chlorine so drastically? 5, 95, 190ppm? If they only tested macronutrients and were supposed top be static for Ca and Mg, then why does Ca bounce around as well as the wildly different Cl numbers? That makes for 5 variables.

They were probably using Calcium Nitrate as their primary N source because the real high Ca numbers coincide with the higher N trials. They could have chosen a different N source. Seems like they had a limited number of salts and were a bit lazy on manipulating them or acquiring others.

 

[farside05]

And I wonder why change the ppm of chlorine so drastically? 5, 95, 190ppm?

Some, but not all, of the higher Cl numbers coincide with higher K, which leads me to think one of the K sources used is Potassium Chloride. KCl is 45-47% Cl.

 

[InTheShed]

Thanks Columbo!

 

[farside05]

Thanks Columbo!

I could maybe see using Potassium Chloride in a soil-less or soil application since they say the K will stay in the substrate and the Cl will leach out with water, but this was done in DWC. You're gonna sit your plant in a bathtub full of Chlorine? Doesn't seem the wisest move.

 

[bruno12345]

Great analysis farside.

Regarding Cl and other nutrients, i quote the authors:

"No matter the experimental design used, an inherent problem in nutrient solution experiments is
that nutrients cannot be added individually but must be added as a compound containing both
anions and cations. Further, the ionic balance constraint requires the sum of the charges of
cations and anions in solution to be equal (De Rijck and Schrevens, 1999b). The implication for
formulating experimental treatment solutions is that it is practically impossible to change the
level of one nutrient while keeping concentrations of all other nutrients the same. In this study,
we focused on N, P, and K concentrations while attempting to keep all other nutrients at
reasonable levels using commonly available horticultural fertilizer compounds. For example,
potassium nitrate and calcium nitrate usually contribute the bulk of nitrogen, potassium, and
calcium in horticultural nutrient solutions (Resh, 2012). Formulating a high N, low K nutrient
solution with these fertilizers results in higher levels of Ca than other nutrient solution
treatments. Likewise, a low N, high K nutrient solution necessitates an additional source of K
such as KCl, which would increase solution Cl concentration. Higher concentrations of nutrients
such as Ca and Cl bring the potential for nutrient interactions which may affect experimental
results. The lack of response to K in the range of 60-340 mg L-1 observed in our trial may be
partially due to competition for uptake from Ca. Regarding experimental Cl levels, hydroponic
cannabis has been shown to tolerate rates of 180 mg L-1 Cl with no impact on yield or potency
(Yep et al., 2020a) so it is unlikely Cl levels limited plant growth in this trial. Though less than
ideal in an experimental setting, there is no perfect solution for the problem of keeping all
nutrient concentrations the same when formulating treatment solutions."


Also note that we cant change the ammonium nitrate ratio.

Seems cannabis pretty resistant to Cl, even at higher KCl rates and DWC

 

[bruno12345]

Also regarding treatments, 125 different nutrient solutions would mean a work for 50 people.

Can you imagine the hard work It would be to scientifically manage 750 plants, measure them, weight root mass, change nutrient solution (125 different types) every week?

The space, the number of equipments required, etc

It would be work for 50 people lol.

So i believe they took science info already there, and made the design accounting that too..

Im not a statistic, nor its been Pret reviewed, so i dont know the implications of that.

The responsible professor is a PhD which worked in japan, china, britain and USA, i Hope he knows what hes doing

 

[farside05]

Great analysis farside.

Regarding Cl and other nutrients, i quote the authors:

"No matter the experimental design used, an inherent problem in nutrient solution experiments is
that nutrients cannot be added individually but must be added as a compound containing both
anions and cations. Further, the ionic balance constraint requires the sum of the charges of
cations and anions in solution to be equal (De Rijck and Schrevens, 1999b). The implication for
formulating experimental treatment solutions is that it is practically impossible to change the
level of one nutrient while keeping concentrations of all other nutrients the same. In this study,
we focused on N, P, and K concentrations while attempting to keep all other nutrients at
reasonable levels using commonly available horticultural fertilizer compounds. For example,
potassium nitrate and calcium nitrate usually contribute the bulk of nitrogen, potassium, and
calcium in horticultural nutrient solutions (Resh, 2012). Formulating a high N, low K nutrient
solution with these fertilizers results in higher levels of Ca than other nutrient solution
treatments. Likewise, a low N, high K nutrient solution necessitates an additional source of K
such as KCl, which would increase solution Cl concentration. Higher concentrations of nutrients
such as Ca and Cl bring the potential for nutrient interactions which may affect experimental
results. The lack of response to K in the range of 60-340 mg L-1 observed in our trial may be
partially due to competition for uptake from Ca. Regarding experimental Cl levels, hydroponic
cannabis has been shown to tolerate rates of 180 mg L-1 Cl with no impact on yield or potency
(Yep et al., 2020a) so it is unlikely Cl levels limited plant growth in this trial. Though less than
ideal in an experimental setting, there is no perfect solution for the problem of keeping all
nutrient concentrations the same when formulating treatment solutions."


Also note that we cant change the ammonium nitrate ratio.

Seems cannabis pretty resistant to Cl, even at higher KCl rates and DWC

Yeah, I read that, but can't say I have complete buy-in. I still think they had other options for salts that they left on the table. Notice Mg and S are static throughout all trials. That suggests to me that they only used 1 source for those elements, Magnesium Sulfate. There's Magnesium Nitrate that could have been added to help create a higher N product. The Mg number never goes up, or if they cut Magnesium Sulfate to account for the increase in Mg from Magnesium Nitrate, the Sulfur number would drop. That didn't happen either. Magnesium Nitrate is common enough that I just bought some from an online hydro store.

Also regarding treatments, 125 different nutrient solutions would mean a work for 50 people.

Can you imagine the hard work It would be to scientifically manage 750 plants, measure them, weight root mass, change nutrient solution (125 different types) every week?

The space, the number of equipments required, etc

It would be work for 50 people lol.

So i believe they took science info already there, and made the design accounting that too..

Im not a statistic, nor its been Pret reviewed, so i dont know the implications of that.

The responsible professor is a PhD which worked in japan, china, britain and USA, i Hope he knows what hes doing

Yes 125 plants and their maintenance would be a pain and a lot of labor, but if they didn't have the space or manpower, and were basically planning on "testing the middle", why design a trial with 5 variables for each macro? If you did 3 variables for each: Nitrogen at 100, 150, 200, Phosphorus at 30,60,90, and Potassium at 150,225,300. Three macros x 3 variables, 27 plants instead of 125. Way more manageable. You'd probably also find that the N-P-K combos produced would line up with a lot of commercially available products.

During COVID-19, some doctors have prescribed the Malaria drug Hydroxychloroquine. Others are prescribing the horse wormer, Ivermectin. I don't take anything someone says as gospel just because they have a few initials after their name. Remember, Jack Kevorkian had a doctorate too.

Don't mean to come off as a dick if it sounds that way. I love this research stuff and wish more would be done to kill off all the bad "Bro Science" that's existed for years. I'm just one that tends to challenge everything. It's my way of learning. Thinking out loud so to speak. If I were a blind sheep I'd have been chucking P-K boosters and other needless crap at my plants the last 6 years, enriching the nute companies who are laughing their way to the bank.

 

[bruno12345]

Oh i was talking about your assumption that they only tested 20 nutrient combinations.

If they did all the possible combinations It would not be 125 plants. Its 5 replicants per treatment, which means 625 (i Said 750, damn math) plants. Simply inhumane for a lab research

I agree with you.
I had classes with godlike phd teachers, and classes with dumba$$ phd teachers that couldnt teach something New to a child. You can google the author easily also.

Science isnt about the answers, the questions are what make us evolve.

Glad you are here. I didnt pay attention to the details you pointed.