Hemp (Cannabis sativa L) tissue nutrient analysis data

[habeeb]

taken from fatman over at rollitup:

Veg,
MAJOR ELEMENTS, Three different sets of tissue samples: The first two are Indica and the third an Indica dominant. The samples were a mix of both bract and bud leaf tissue. Total THC: 22.9, 21.8 and 20.8
Total Nitrogen (N) 4.6%...........3.25.....4.2......4.4
Total Phosphorus (P) 1.5%.......0.35....0.50....0.65
Total Potassium (k) 3.6%.........2.55....3.75....3.00
SECONDARY ELEMENTS,
Total Magnesium (Mg) 1%........0.25....0.50....0.50
Total Calcium (Ca) 4.7%..........2.45....3.45....3.10
Total Sulphur (S) 4.2%............0.25....0.25....0.45

Flower,
MAJOR ELEMENTS,
Total Nitrogen (N) 1.2%...........3.75....4.25....3.60
Total Phosphorus (P) 1.3%.......0.75....0.90....0.75
Total Potassium (k) 2.6%.........4.1.....4.5......4.3
SECONDARY ELEMENTS,
Total Magnesium (Mg) 1%........0.40....0.50....0.50
Total Calcium (Ca) 3.8%..........1.40....1.30....1.25
Total Sulphur (S) 3.2%............0.30....0.35....0.35

------------------------------------------------------

Pot Bloom
Nitrogen 267
Phosphorus 82
Potassium 291
Magnesium 93
Calcium 261
Sulfur 123
Iron 10.00
Manganese 5.00
Boron 5.00
Zinc 5.00
Copper 1.00
Molybdenum .09




not sure where he got these, just passing along if its any use to you

 

[Carl Carlson]

thanks habeeb.

 

[spurr]

Hey Carl,

I keep meaning to post up some info in this thread from my other thread about cannabis and tissues assays I uploaded for you; and I keep forgetting. For now, here is a little more for ya, I will try to post more in the next week:


1. "An Eye On Phosoporus Nutrition: Understanding how phosphorus acts in soil and in the plant will help you regulate vegetable transplant growth"
By Shiv Reddy
September 2010
http://www.greenhousegrower.com/magazine/?storyid=3753

^^^ great info about why we don't need nearly as much P as growers love to apply, in soilless media and hydro. Also good info about how high P and N effects upon "root:shoot" ratio.​

2. "Understanding Plant Nutrition: An Introduction: In a year-long series, Argo and Fisher take a microscope to the details that can help growers make informed decisions on nutrients"
By Bill Argo and Paul Fisher
January 2008
http://www.greenhousegrower.com/magazine/?storyid=109

^^^ the series "Understanding Plant Nutrition" by Bill Agro and Paul Fisher should be required reading for all cannabis growers IMO.

Here is another good example of average content of elements in plants. Note how P is as low as Mg, and 2 times lower than Ca and 8 times lower than K:

 

[Carl Carlson]

Yep that's a great magazine. Better than High Times, Urban Gardener, Growing Edge and Max Yield put together.

agreed on #2. I've e-mailed back and forth with Argo. He's nice guy and very willing to talk and explain things.

and I've got this on order:

http://www.meistermedia.com/store/books.html

Understanding pH Management $39.95 On Sale! $25.00
For Container-Grown Crops by William R. Argo and Paul R. Fisher You asked for it and now you've got it All you ever needed to know about pH. Bill Argo and Paul Fisher, authors of the 13-article pH series in Greenhouse GrowerTM, have repackaged the series into a full-fledged, 64-page book, Understanding pH Management For Container-Grown Crops. Based on the latest plant nutrition research, this book is a necessity for every greenhouse and nursery operation. Offering detailed descriptions and solutions for day-to-day nutrition problems, accompanied by comprehensive color charts, graphs, photos, and a full glossary of pH and EC related terms, Understanding pH Management For Container-Grown Crops is available from Meister Publishing for the most affordable price in the industry.

 

[spurr]

Nice! I am ordering tomorrow, thanks for the heads up!

 

[habeeb]

carl, you delete your account?

I have some pics for you if there any help ( please save them if you see them, as I'm gonna change the folder soon ) :

 

[spurr]

habeeb,

Where did you find those tables? I ask because they look very familiar to me. Thanks.

Oh yea, it sucks Carl deleted his account, I have his email address I will ask him why.

 

[tester]

Hemp diseases and pests

 

[habeeb]

Hemp diseases and pests

this book spurr

it really is one of the best cannabis books written. looking at it online does not compare to to having it in your hand to skim through. pulled it out of "storage" and am amazed every time I open it.. really is a vault of knowledge, and not just on pests / diseases ..


the pics are dark, but Im no photographer...

 

[spurr]

Tester, yup, that's it, I was just re-reading a thread I made at TCC on this topic and I used the same image from "Hemp diseases and pests: management and biological control" by John Michael McPartland, Robert Connell Clarke, David Paul Watson (aviable via. Google books for free ).

Thanks

 

[spurr]

@ all,

I am going to post a bunch of papers and studies, the ones about cannabis shows how cannabis has much less need for P than N, K, etc., which agrees with other studies already posted in this thread:


1. In the first study Carl uploaded in the first post, the soil used was "chernozem", a Russian word meaning "black earth". Chernozem is a humus rich and fertile soil horizon found in many parts of the world. I think it's important to list typical properties of chernozem for a more complete understating about the paper Carl uploaded.

Typical nutrient profile of chernozem (Melent’ev, et al, 1999)

• Total Nitrogen = 0.61%
• P2O5 = 0.15%
• Ca = 0.049%
• Mg = 0.012%
• CEC = 15 – < 40 meq/100 g

2. Foundation for Practical Application of Plant Analysis: "Scientific Basis for Plant Analysis"
(North Carolina State; link to webpage)



3. "Plant Analysis Handbook – Nutrient Content of Plant"
(University of Georgia; link to webpage)



4. "Plant Tissue Analysis"
(University of Maryland; link to PDF)



5. "Mineral nutrition of Cannabis sativa L."
S. Landi
Journal of Plant Nutrition, Volume 20, Issue 2 & 3 February 1997 , pages 311 - 326
(abstract only for now) http://www.informaworld.com/smpp/content~content=a905881394&db=all



6. "Influence of nitrogen supply and P and K levels of the soil on dry matter and nutrient accumulation of fiber hemp (Cannabis sativa L.)"
Ildiko Ivonyi , Zolton Izsoki and Hayo M. G. Van der Werf
(full webpage) http://druglibrary.net/olsen/HEMP/IHA/jiha4209.html



7. "Nutrient Uptake and Partitioning by Industrial Hemp"
by John Heard, Keith Watson and Jeff Kostiuk,
Manitoba Agriculture, Food and Rural Initiatives, Manitoba Canada
(full PDF) http://www.umanitoba.ca/afs/agronomists_conf/proceedings/2007/Heard_poster.pdf



8. "Time factor in utilization of mineral nutrients by hemp"
Sister Mary Etinne Tibeau
Plant Physiol. (1936), vol. 11, no. 4, pp. 731-47
(full PDF) http://www.plantphysiol.org/cgi/reprint/11/4/731.pdf



9. "Effect of nitrogen on tetrahydrocannabinol (THC) content in hemp (Cannabis sativa L.) leaves at different positions"
I. Bócsa, P. Máthé, and L. Hangye
(full webpage) http://druglibrary.net/olsen/HEMP/IHA/jiha4207.html



10. "Responses of Greenhouse-grown Cannabis sativa L. To Nitrogen, Phosphorus, and Potassium"
C. B. Coffman and W. A. Gentner
Published in Agron J 69:832-836 (1977)
(abstract only for now)

Growers of illegal Cannabis sativa L. Use various cultural practices to maximize crop production. The objective of this study was to evaluate the morphological and biochemical responses of greenhouse grown C. Sativa to soil incorporated N, P, and K as they reflect the geographical origin of Cannabis derivatives. Fertilizers were blended with Ap horizon soil from a Gilpin silt loam before placement in 12-cm pots. NH4NO3-N was applied at 0, 25, and 125 ppm. Phosphorus and K from super-phosphate and KCI, respectively, were applied at 0, 50, and 150 ppm. Forty-five-day-old anthesic Cannabis plants were harvested and combined leaf and flower tissues were analyzed for cannabidiol (CBD) and {Delta}g-tetrahydrocanna-binol ({Delta}9THC). Nine essential elements were also measured in plant tissue.

Plant growth, tissue yield, and concentration of CBD and {Delta}9THC were positively correlated with extractable P2O5 (p < 0.01). Phosphorus concentrations in tissue were similarly related to yield of dry matter and cannabinoid concentrations. Uptake of K was positively correlated with extractable K.2O across all treatment levels (r=0.40**), but was negatively correlated with tissue yield (r=--0.36"*). Growth and tissue yields were negatively related to total plant N (p< 0.01). Levels of extractable P2O5, Mn, B, and Mg were associated with specific concentration ranges for several plant elements plus {Delta}9THC. Thus, it was possible to partially characterize a soil by tissue analysis. For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm {Delta}9THC. Usefulness of such relationships will be dependent upon extensive evaluation of Cannabis on different soils under various cultural conditions. At this time, the reliability required for determination of origin of Cannabis derivatives via chemical analysis does not exist when only essential elements and cannabinoids are considered.

 

[spurr]

the pics are dark, but Im no photographer...

I think a pics look fine, thanks for taking the time to post them. If you move them can you re-post them again once they are moved?

 

[spurr]

@ all,

Here are some papers and info about plant nutrient topics, I figured it was worth posting...



1. "Modelling plant nutrition of horticultural crops: a review"
J. Le Bot, S. Adamowicz and P. Robin
Scientia Horticulturae 74 1998. 47–82
(full PDF) http://dwkx.hzau.edu.cn/kech/ssyy/qysd/szmx/6.pdf



2. "Phosphorus Uptake by Plants: From Soil to Cell" [relevant info for soilless and hydro]
Daniel P. Schachtman, Robert J. Reid, and S.M. Ayling
Plant Physiol. (1998), vol 116, pp. 447–453
(full text) http://www.plantphysiol.org/cgi/reprint/116/2/447



3. "pH Management and Plant Nutrition"
Bill Argo
This article from the Journal of the International Phalaenopsis Alliance.

• Part 1 Intro
• Part 2 Water Quality
• Part 3 Fertilizers
• Part 4 Substrates
• Part 5 Choosing the Best Fertilizers

4. CALL FOR PAPERS: Plant Physiology: Focus Issue on Plant Phosphorus Nutrition
(full PDF for announcement) http://aspb.site-ym.com/resource/resmgr/Docs/2010_FOCUS_Plant_Phosphorus.pdf

• this is just a heads up that Plant Phys. Journal will be devoting an entire issue to plant P nutrition in July 2011! I will post papers from it once they are available

 

[spurr]

@ all,

Below is my best attempt to use GH Flora Series ferts to make a (close to) ideal fert mix for cannabis. I based my mix upon studies in this thread from Carl and myself, also, a while ago Carl was kind enough to let me know CNS-17 has nearly identical elemental makeup as my mix.

I have tested my mix, and someone else here is also testing my mix, and so far he likes it as much and/or better than Lucas's suggestion for GH FloraBloom at 1,110-1,300 ppm (TDS).

Below is my best effort to make an ideal chem fert mix using General Hydroponics Flora series to provide cannabis with sufficient level of elements. Ideally I would drop N to around 100 ppm so using maybe 3-4 ml of GH Micro and using 2.5 ml of CalMag+ might be better but I haven't done the math for that yet.

I have tested the following mix for growing cannabis and it preformed better than the Lucas formula without excess ions found in the Lucas formula (which is based upon flawed claims by Ed Rosenthall, Mel Frank, George Cervantes, et al.):

GH Grow/Micro/Bloom at 5/5/5 ml with CalMag+ at 5 ml and ProTeKt at 2.5 ml (all per gallon; along with some citric acid to lower pH to ~6 and to keep P anions soluble):​

• Total N...140 ppm
• Nitrate N...130 ppm
• Ammoniacal N...10 ppm
• P.....39 ppm
• K.....155 ppm
• Ca...126 ppm
• Mg...46 ppm
• S.....15 ppm
• Fe....3.1 ppm
• Mn...0.8 ppm
• Si.....56 ppm
• total PPM = ~580
• Ca:Mg ratio = ~2.7
• Nitrate N:Ammoniacal N ratio = 13

Here is data from CNS17 (from bontaicre) thanks to Carl Carlson:

15 ml per gallon​

• Total N - 137 ppm
• Nitrate N - 131 ppm
• Ammoniacal N - 6 ppm
• P - 40 ppm
• K - 152 ppm
• Ca - 128 ppm
• Mg - 23 ppm
• S - 50 ppm
• Mn - .22 ppm
• Mo - .02 ppm
• Total PPM - ~530
• Ca to Mg ratio - ~5.5
• Nitrate N to Ammoniacal N ratio - ~21.8

FWIW,

1. in terms of Ca to Mg ratio, anywhere from 1.5-8 is fine, the claim that there is an ideal Ca to Mg ratio (i.e. 3) is a total myth. I debunked that myth over at TCC and I could post many studies here if anyone is interested.

2. in terms of NN to AN ratio, above 10-13 is the goal, the reason is cannabis prefers NN, not AN. And, if the plant can't move enough sugar into the roots to convert AN, the AN will cause roots to 'burn' (i.e. phytotoxicity). Also, plants can not self-regulate uptake of AN, but they can/do self-regulate uptake of NN, I can post info about this self-regulation of nitrogen if anyone is interested (plants also self-regulate uptake of P and IIRC K, Ca, etc.).

 

[spurr]

.

https://www.icmag.com/ic/showpost.php?p=4094492&postcount=55

 

[BerndV]

"Plant growth, tissue yield, and concentration of CBD and {Delta}9THC were positively correlated with extractable P2O5 (p < 0.01). Phosphorus concentrations in tissue were similarly related to yield of dry matter and cannabinoid concentrations. Uptake of K was positively correlated with extractable K.2O across all treatment levels (r=0.40**), but was negatively correlated with tissue yield (r=--0.36"*). Growth and tissue yields were negatively related to total plant N (p< 0.01). Levels of extractable P2O5, Mn, B, and Mg were associated with specific concentration ranges for several plant elements plus {Delta}9THC. Thus, it was possible to partially characterize a soil by tissue analysis. For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm {Delta}9THC."

The above quote indicates that higher levels of P are in fact positively correlated with higher yields and THC content while higher K correlates with lower yields. I have not yet read the full study, but this seems to contradict the notion that we need significantly lower P and higher K for optimum cannabis nutrition.

 

[spurr]

"Plant growth, tissue yield, and concentration of CBD and {Delta}9THC were positively correlated with extractable P2O5 (p < 0.01). Phosphorus concentrations in tissue were similarly related to yield of dry matter and cannabinoid concentrations. Uptake of K was positively correlated with extractable K.2O across all treatment levels (r=0.40**), but was negatively correlated with tissue yield (r=--0.36"*). Growth and tissue yields were negatively related to total plant N (p< 0.01). Levels of extractable P2O5, Mn, B, and Mg were associated with specific concentration ranges for several plant elements plus {Delta}9THC. Thus, it was possible to partially characterize a soil by tissue analysis. For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm {Delta}9THC."

The above quote indicates that higher levels of P are in fact positively correlated with higher yields and THC content while higher K correlates with lower yields. I have not yet read the full study, but this seems to contradict the notion that we need significantly lower P and higher K for optimum cannabis nutrition.

I too have yet to read the full study. What you quoted was my hand copying of the abstract from that study. But I made that more than a year ago and now I cannot find the study again. I am still looking for it.

There are a couple of issues with the wording of that abstract:

1. It doesn't list the levels of P, K, etc. used in fertigation water relative to the results. Ex., it doesn't list the ppm level of P that gave the highest level of THC, CBD and growth; and same goes for level of K. I.e., "...Phosphorus and K from super-phosphate and KCI, respectively, were applied at 0, 50, and 150 ppm.". For all we know, 50 ppm P gave the best results for P (verses 150 ppm), and 150 ppm K gave the worst rustles for K (verses 50 ppm). The following sentence of the quote is a prime example of why I think 50 ppm P was better than 150 ppm P: "Thus, it was possible to partially characterize a soil by tissue analysis. For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm {Delta}9THC."


2. The last two sentences of the abstract basically nullify the study as a means to form a definitive answer: "Usefulness of such relationships will be dependent upon extensive evaluation of Cannabis on different soils under various cultural conditions. At this time, the reliability required for determination of origin of Cannabis derivatives via chemical analysis does not exist when only essential elements and cannabinoids are considered."


3. The abstract doesn't list the levels of P, K, etc. extracted from the soil relative to the results; it only gives one ambiguous example of exacted P2O5. Without quantitative data we can not from definitive opinions based upon that abstract in terms of amounts of elements and their effect upon growth and cannabinoid levels of cannabis.


4. The soil extraction method used (via strong acids) is not representative of the actual P that was available to the plant (the same goes for K, N, etc., albeit to a lesser degree). In terms of P, it is because much of the inorganic P added to fertigation water is made insoluble once in soil; and also because soluble P has very low mobility in the "soil solution" (thin layer of water surround media particles). Using strong acids as a soil test of potentially plant usable ions (both soluble and insoluble) is flawed because it doesn't show what the plant has access to (see #5 below), thus it doesn't show only what the plant can take up.


5. The much better soil (and soilless) test method of potentially plant usable (both soluble and insoluble) elements, especially P, is the Co2 extraction method. Few soil scientists use that method, even though it's much more representative of what the roots have access to in soil. That is because the Co2 extraction method mimics the weak acids (ex. carbonic acidic, citric acid, etc.) found in soil that help solublize P and other ions for roots to take up.


FWIW,

My own trials with low P (via my mix at 39 ppm P) verses high P (via the Lucas formula, both the traditional 0-18-06 formula and his updated FloraNova Bloom formula; both with > 105 ppm P); showed reduced P did not reduce growth or yield or THC content (via my testing with comparative TLC). Also, Oswizzle has been testing my mix for a while now and he found the same as I did verses the Lucas formula (with FloraNova Bloom) in terms of growth and yield. Not only that, but Grat3fulh3ad's formula, which is used by MANY growers, has 60 ppm P, and no one has complained about reduced yield or high from his mix AFAIK...

 

[spurr]

FWIW, here is a post I made back at TCC where I complied a (corrected) list of common ferts for cannabis:



Fert breakdown per gallon of water:

• TN = Total Nitrogen (nitrate + all forms of ammoniacal)
• NN = Nitrate Nitrogen
• AN = Ammoniacal Nitrogen
• P = Phosphors
• K = Potash
• Ca = Calcium
• Mg = Magnesium
• S = Sulfur
• Fe = Iron
• Mn = Manganese
• Si = Silicon
• Ca:Mg ratio = Calcium to Magnesium ratio
• NN:AN ratio = Nitrate N to Ammoniacal N ratio (greater than 10:1 is best, a mix of both forms of N creates less pH flux. Ammonium nitrogen (which is major form of AN in ferts) can limit uptake of other ions by roots (such as P), thus only a little AN should be used).

Epsom salt @ 1 gram per gallon: (~4.5 g Epsom salt = 1 level tsp)

• Mg...26
• S.....103
• total PPM = 129

ProteKt @ 2.5 ml per gallon:

• K = 18
• Si = 56
• total PPM = 74

CalMag+ @ 5ml per gallon:

• TN...27
• NN...26
• AN...1
• Ca....43
• Mg...16
• Fe...1.4
• total PPM = 86

Original Lucas Formula @ 0/8/16 ml per gallon:

• TN...132
• NN...124
• AN...8
• P.....106
• K.....184
• Ca...132
• Mg...73
• S.....49
• Fe...2.6
• Mn...1.3
• total PPM = ~670
• Ca:Mg ratio = ~1.8
• NN:AN ratio = ~15.3

Grat3fulh3ad Formula @ 0/6/9 ml with 1 g Epsom salt, per gallon:

• TN...99
• NN...93
• AN...6
• P.....60
• K.....107
• Ca...99
• Mg...67
• S.....130 (Grat3fulh3ad gives an incorrect total S ppm figure of 61)
• Fe....2
• Mn...1
• total PPM = 565
• Ca:Mg ratio = ~1.5
• NN:AN ratio = 15.5

My mix @ 5/5/5 ml with 5 ml CalMag+ and 2.5 ml ProTeKt, per gallon(along with some citric acid to lower pH to ~6 and to keep P anions soluble):

• I plan to test reducing CalMag+ by 25%

• TN...140
• NN...130
• AN...10
• P.....39
• K.....155
• Ca...126
• Mg...46
• S.....15
• Fe....3.1
• Mn...0.8
• Si.....56
• total PPM = ~580
• Ca:Mg ratio = ~2.7
• Nitrate N:Ammoniacal N ratio = 13

CNS17 (from bontanicare) thanks to Carl Carlson @ 15 ml per gallon

• TN...137
• NN...131
• AN...6
• P.....40
• K.....152
• Ca...128
• Mg...23
• S.....50
• Mn...0.22
• Mo...0.02
• Si.....56
• total PPM = ~530
• Ca:Mg ratio = ~5.5
• Nitrate N:Ammoniacal N ratio = ~21.8

 

[tester]

Epsom salt is MgSO4.7H2O
According to this molar mass calc it contains :

• 13.01% S
• 9.86% Mg

Epsom salt @ 1g/gallon =
0.0986 * 1000 / 3.78541178 = 26.05 Mg
0.1301 * 1000 / 3.78541178 = 34.37 S (instead of103)

You might made a typo when calculating the S content.


DynaGro's ProTekt label's says:

• 3.7% K2O
• 7.8% SiO2 (=3.646% Si calculated with the molar mass calc)

1.2 g/ml specific gravity according to MSDS


2.5ml ProTekt per gallon:

• 29.3 K2O
• (24.3 K)
• 61.83 SiO2
• (28.9 Si) (instead of 56)

According to my calculations:

LUCAS Original as Cannastats
Source: http://www.angelfire.com/cantina/fourtwenty/articles/profiles.htm

• 129.6 N
• 121.9 NO3
• 7.8 NH4
• 243.1 P2O5
• 106 P
• 220.4 K2O
• 183 K
• 129.6 Ca
• 72.9 Mg
• 2.59 Fe
• 1.2965 Mn
• 0.0207 Mo
• 0.013 Co
• 48.6 S

674 PPM

• N2O5:K2O ratio = 1 : 1.9 : 1.7
• N:K ratio = 1.2 : 1 : 1.7
• Ca:Mg ratio = 1.8 : 1
• K:N ratio = 1.4 : 1

Rez/H3ad Coco
Source: https://www.icmag.com/ic/showthread.php?t=55683

• 97.2 N
• 91.4 NO3
• 5.8 NH4
• 136.8 P2O5
• 59.6 P
• 128.9 K2O
• 106.9 K
• 97.2 Ca
• 66.9 Mg
• 1.94 Fe
• 0.9723 Mn
• 0.0156 Mo
• 0.0097 Co
• 62 S

493 PPM

• N2O5:K2O ratio = 1 : 1.4 : 1.3
• N:K ratio = 1.6 : 1 : 1.8
• Ca:Mg ratio = 1.5 : 1
• K:N ratio = 1.1 : 1

Spurr's 5/5/5 ml with 5 ml CalMag+ and 2.5 ml ProTeKt, per gallon(along with some citric acid to lower pH to ~6 and to keep P anions soluble):

• 136.8 N
• 127.4 NO3
• 9.3 NH4
• 90.6 P2O5
• 39.5 P
• 194.3 K2O
• 161.2 K
• 123.3 Ca
• 46 Mg
• 2.94 Fe
• 0.8103 Mn
• 0.013 Mo
• 0.0081 Co
• 28.8951 Si
• 15.2 S

555 PPM

• N2O5:K2O ratio = 1.5 : 1 : 2.1
• N:K ratio = 3.5 : 1 : 4.1
• Ca:Mg ratio = 2.7 : 1
• K:N ratio = 1.2 : 1

with 25% less (=3.75ml/gal) Calmag

• 130.2 N
• 121 NO3
• 9.1 NH4
• 90.6 P2O5
• 39.5 P
• 194.3 K2O
• 161.2 K
• 112.7 Ca
• 42 Mg
• 2.61 Fe
• 0.8103 Mn
• 0.013 Mo
• 0.0081 Co
• 28.8951 Si
• 15.2 S

533 PPM

• N2O5:K2O ratio = 1.4 : 1 : 2.1
• N:K ratio = 3.3 : 1 : 4.1
• Ca:Mg ratio = 2.7 : 1
• K:N ratio = 1.2 : 1

Chart for quick comparison:

 

[BerndV]

"For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm {Delta}9THC."

I would infer from the above sentence that less than 100 ppm of P2O5 reduced THC content. The following sentence is also thought provoking:

"Uptake of K was positively correlated with extractable K.2O across all treatment levels (r=0.40**), but was negatively correlated with tissue yield (r=--0.36"*)."

The earlier AN study and accompanying bar graphs referred to by Carl Carlson would ostensibly demonstrate a much higher need for K in flowering. However, the above quote indicates that increasing K increases uptake of K but decreases yield. Perhaps the AN study testing higher K supplementation in flowering merely reflects the increased uptake of K in tissue analysis and nothing else. Yield and potency may still be lowered in a high K and low P scenario. I am only hypothesizing based on this one abstract but I do find it quite interesting, as there is very little in the scientific literature that looks directly at what this particular study appears to demonstrate.

Regarding H3ad's formula and results, he tweaked his formula about halfway through his thread by increasing the GH Bloom to 12 ml/gal for a portion of flowering. He also uses little if any epsom anymore (occasionally 1/2 gram/gal). The 6/12 formula gives the following profile:


N: 97
P: 79
K: 137
Mg: 55
Ca: 97

I used his formula for a while (I grow in coco) and found it a bit too low in P and K once 12/12 was initiated. My results improved rather dramatically by increasing the bloom upon initiation of 12/12 and keeping it higher throughout the flowering cycle. Whether the plants are benefiting from the higher K alone or the higher P as well is not clear. However, the higher P seems not to result in any negative effects. Also, there are plenty of very good growers on this site getting excellent results using nothing but GH Maxibloom, which is fairly high in P and and K and pretty low in N. I am currently running a combination of Canna Coco A&B plus GH Bloom and Canna PK 13/14. My bloom formula is 9 ml/gal A&B plus 5 ml/gal bloom and 1ml/gal PK 13/14. This gives the following:

N: 138
P: 97
K: 154
Mg: 52
Ca: 126

I am getting truly excellent results with this profile. The bottom line for me is that I don't think the jury is in yet on optimum P when it comes to container grown cannabis and the goal of higher yields in conjunction with maximum potency.