[dizzlekush]

Cannabinoid Profile and Elemental Uptake of Cannabis sativa L. as Influenced by Soil Characteristics.
"Soil Mg was negatively correlated with Ag THC concentrations in leaf tissue (Table 7). Mean Ag THC concentrations greater than 6,900 ppm were found in leaf tissue of plants grown on two soils with <40 ppm extractable Mg. However, one soil with <40 ppm Mg produced plants with a mean Ag THC concentration of only 2,257 ppm(Table 6, soil 3). Plant N, previously shown negatively correlated with soil Mg(Table 4), was positively correlated with Ag THC (Table 7). Haney and Kutscheid (1973) reported positive correlation of total soil N with A~THC levels in wild C. sativa in Illinois. A highly significant positive correlation was found for the Ca/Mg soil ratio to A~THC concentration (Table 7). A balance between Ca and Mg appeared to be required for maximum Ag THC accumulation in leaf tissue. As Mg levels increased relative to Ca, Ag THC concentrations decreased. These relationships will be examined in future experiments....
Ratios of concentrations of /xgTHC/CCC were positively correlated with leaf P, P/Fe, and P/Zn ratios (Table 8). Consequently, the P content of plant tissue seemed to affect the A~THC-CCC relationship, which
suggested involvement of P in CCC breakdown or /~gTHC formation. Added involvement of P was shown by the positive correlation between the A~THC/ CBD ratio and plant P. Several writers have indicated that CBD may be a precursor of Ag THC in C. sativa (Kiippers, Lousberg, and Bercht, 1973; Farnsworth, 1969). These data suggested that increased concentrations of P in leaf tissue may have enhanced the conversion of CBD to Ag THC.
Cannabinoids belong to the chemical class of natural terpenophenols. P may be involved in cannabinoid reactions by interaction of geraniol phosphate and olivetol which may form CBD precursors (Mechou- lam, 1973). These, in turn, may transform to Ag THC and eventually CBN."

Responses of Greenhouse-grown Cannabis sativa L. to Nitrogen, Phosphorous, and Potassium.
"Concentration means of CBD and A°THC ranged from 183 to 2,532 ppm and 2,434 to 9,472 ppm, respectively, but did not differ significantly among treatments (Table 5). Mean total yields of AO THC ranged from 0.3 mg to 61.2 rag/plant and were significantly different among treatments. The significance of these differences was largely due to growth responses to P. Total AO THC yield was significantly correlated with soil P205and applied P (r --- 0.82,** 0.84,** respectively). Concentrations of CBD and AO THC were both positively correlated with soil P205(Table 6) and plant P (Table 7).
Plant Mn and Ca were negatively correlated with CBD and A9THC concentrations (Table 7). These relationships probably reflected the influence of P on cannabinoid concentrations and on Mn and Ca levels in the plants. Plant B and Zn were also negatively correlated with concentration of Ag THC.The biochemical mechanisms responsible for synthesis of cannabinoids are not clearly understood; therefore, we cannot yet explain how previously discussed elements affect cannabinoid production. Phosphorus may be involved in cannabinoid biosynthesis via the interaction of geraniol phosphate and olivetol (Mechoulam,. 1973). The other elements may affect related enzymatic reactions."

Seems to be some possible benefits of high P after all, in late bloom especially. Mg having negative correlations with THC surprises me personally.

[spurr]

Hey buddy,

IIRC, the second study (which I posted here some months ago and) I read a while ago, also found high K was (weakly) negatively correlated to THC-A quantity. Correct? Also, as I wrote in my fertilizer thread, I really do wish the second study authors had quantified trichome density (trichome per mm^2) instead of simply hypothesizing about why they found a increase in THC.

In the first study I think we can draw less strong conclusion being that it was carried out in soil. However, from my understanding it's not high Mg per say that has the strongest correlation to THC, it's the Ca:Mg ratio. Once the ratio falls below 1, according to my understanding, THC quantity sufferers. That is why I keep the Ca:Mg ratio 2 during full-flowering, and Mg at ~66 ppm, that and due to the antagonistic relationship of Ca and Mg. Also, if we reduce Mg we reduce leaf Chl (chlorophyll) which will reduce Pn (rate of photosynthesis) and have other negative impacts. I think the 'happy medium' is keeping Mg less than 80 ppm and and Ca:Mg ratio equal to and greater than 2 during full-flowering.

I am happy that C.B. Coffman authored the first paper, he seems to like THC

UV-B radiation effects on photosynthesis, growth and cannabinoid production of two Cannabis sativa chemotypes
Lydon J, Teramura AH,Coffman CB.
Photochem Photobiol. 1987 Aug;46(2):201-6

It's nice to see those two studies both found high P is (strongly) correlated to THC. That lends more weight to the evidence of high P and THC.

Also, below is a study I have been meaning to get, however, it's from 1947 so its quality could be poor:

The effect of soil fertilization on the formation and the amount of cannabinoid substances in Cannabis sativa L. in the course of one vegetation period
Lumír Hanuš, Marie Dostálová (1947)
Acta Univ Palacki Olomuc Fac Med. 1994;138:11-5.

Abstract

The study followed the effect of the soil fertilization on the growth of plants and on the formation and the amount of extractible substances as well that of two main cannbinoid substances (CBD, delta-9-THC) in the Czechoslovak variety of hemp, Rastislavice, cultivated in Czechoslovakia for fibre production in the course of the vegetation period of 1988. In fourteen various vegetation stages of the plant growth, the samples of the plant tops, cultivated on five fields with different soil fertilization, were collected and analyzed in the dried state.

FWIW,
Because of those studies I made my nutrient formulations have increased P during second stage flowering, what I call full-flowering. K is only increased during first stage flowering, what I call early-flowering.

[dizzlekush]

Originally Posted by spurr

Hey buddy,

IIRC, the second study (which I posted here some months ago and) I read a while ago, also found high K was (weakly) negatively correlated to THC-A quantity. Correct?

Responses of Greenhouse-grown Cannabis sativa L. to Nitrogen, Phosphorous, and Potassium.
"Growth of C. sativa, concentration of the hallucinogen A.9THC, and yield of AflTHC were positively related to soil P levels in a greenhouse study employing anthssic 45-day-old plants. There were no significant growth or cannabinoid responses to varied rates of applied N and K, although maximum plant growth and A9THC yields were associated with soil P in conjunction with high N or moderate to high K levels in the soil. C. sativa plants accumulated Mn up to 1,800 ppm under low P without exhibiting visual toxicity symptoms although plant and soil Mn concentrations were negatively correlated with plant growth.
Levels of several elements in leaf tissue were shown to be related to soil P2O5, Mn, B, and Mg concentrations, suggesting an approach to determination of origin of Cannabis derivatives by their chemical analyses."

from the 2nd study.

but looking at the actual data graph actually shows a conclusion different than the conclusion given. it shows your conclusion.

out of the 21 different feeding methods in the study, 5 produced a significantly higher THC content in hemp plants.

Oppm N, 150ppm P, 0ppm K - had a 4.5g yield on average
25ppm N, 150ppm P, 0ppm K - had a 3.41g yield on average
125ppm N, 150ppm P, 0ppm K- had a 6.58g yield on average (highest yield in study by almost 1 g)
0ppm N, 50ppm P, 50ppm K- had a 3.41g yield on average
0ppm N, 150ppm P, 50ppm K- had a 5.54g yield on average (highest THC concentration in study)

threw the dry yield in there just for kicks.

every single plant fed 150ppm P was in the highest group when it comes to THC content except the one group that was fed 150ppm K.

Originally Posted by spurr

from my understanding it's not high Mg per say that has the strongest correlation to THC, it's the Ca:Mg ratio. Once the ratio falls below 1, according to my understanding, THC quantity sufferers. That is why I keep the Ca:Mg ratio at and greater than 2, that and due to the antagonistic relationship of Ca and Mg. Also, if we reduce Mg we reduce leaf Chl (chlorophyll) which will reduce Pn (rate of photosynthesis) and have other negative impacts. I think the 'happy medium' is keeping Mg less than 80 ppm and and Ca:Mg ratio equal to and greater than 2.

i think the first study related reduced THC production with >40ppm Mg

[spurr]

Thanks for clarifying that for me, my brain isn't working well today

[dizzlekush]

Originally Posted by spurr

Thanks for clarifying that for me, my brain isn't working well today

you are very possibly right that increased K will limit inceased THC production via increased P (not sure how, just what the data shows), but K by itself seems to have no antagonistic effects on THC production.

[spurr]

Cool. I thought i was going mad there for a minute. Thanks for looking at it again, I don't have time to review those papers today and it's been some months since I last read them.

[dizzlekush]

Originally Posted by spurr

It's nice to see those two studies both found high P is (strongly) correlated to THC. That lends more weight to the evidence of high P and THC.

Sounds like the high P myth has been revived, and Papa's got a brand new bag.

[spurr]

Originally Posted by dizzlekush

but looking at the actual data graph actually shows a conclusion different than the conclusion given. it shows your conclusion.

out of the 21 different feeding methods in the study, 5 produced a significantly higher THC content in hemp plants.

Oppm N, 150ppm P, 0ppm K - had a 4.5g yield on average
25ppm N, 150ppm P, 0ppm K - had a 3.41g yield on average
125ppm N, 150ppm P, 0ppm K- had a 6.58g yield on average (highest yield in study by almost 1 g)
0ppm N, 50ppm P, 50ppm K- had a 3.41g yield on average
0ppm N, 150ppm P, 50ppm K- had a 5.54g yield on average (highest THC concentration in study)

threw the dry yield in there just for kicks.

every single plant fed 150ppm P was in the highest group when it comes to THC content except the one group that was fed 150ppm K.

I tried to place P ppm above 100 in my full-flowering mix but it's not possible while keeping K near 200 ppm and ammonium low (re NO3:NH4 ratio). Sadly, there are not a great many sources of P; there's MAP, DAP, MKP, phosphoric acid, etc., but all contain other elements that affect the profile.

Originally Posted by DizzleKush

i think the first study related reduced THC production with >40ppm Mg

This is what I focused on:

"A highly significant positive correlation was found for the Ca/Mg soil ratio to A~THC concentration (Table 7). A balance between Ca and Mg appeared to be required for maximum Ag THC accumulation in leaf tissue. As Mg levels increased relative to Ca, Ag THC concentrations decreased. These relationships will be examined in future experiments...."

[spurr]

Originally Posted by dizzlekush

Sounds like the high P myth has been revived, and Papa's got a brand new bag.

Ha. Only for later-flowering phase IMO . Not for vegetative or early-flowering (i.e., pre-flowering and a week or two after that point), when roots and shoots are still growing.

[Storm Shadow]

Spurr...any relation to my comment about 15ml per gallon of FN Bloom gave me frostier nugs and this data? I used the FN at 1300 PPM per your suggestion and it was always bomb results...I think I also noticed plants gettings trichs sooner also ...