study published in Oct. on the effects of EC levels on Cannabis yield

[LJB]

This study was released on October 2nd, 2009 at the International Association for Cannabinoid Medicines, 5th Conference on Cannabinoids in Medicine, held in Cologne, Germany.

Here is the link to the .pdf: http://www.cannabis-med.org/meeting/Cologne2009/reader.pdf

The study begins on page 28:

EFFECT OF SALINITY IN NUTRIENT SOLUTION ON YIELD OF CANNABIS IN INDOOR CONDITION

Gianpaolo Grassi1, Salvatore Casano1,2, Marco Michelozzi3, Valentina Martini3 and Diaz Kroeze4

1CRA-CIN, Rovigo branch section, Italy
2DAAT, Faculty of Agricultural Sciences, University of Palermo, Italy
3Institute of Plant Genetics, National Research Council, Sesto Fiorentino, Italy
4PlantResearch International BV, Oosterhout nb, The Netherlands

Recent cultivation tests showed that in rock wool cultivation the fertiliser level, generally expressed as Electrical Conductivity (EC), affects yield and quality of Cannabis sativa L. The precise effects differ between varieties. However, the interaction between EC and active constituents (cannabinoids and terpenoids) remains poorly understood. So as to increase the EC level of the nutrient solution without causing phytotoxicity, agronomically optimised formulas of fertilizers were designed by PlantResearch BV to be used for this trial.

Methods: Four levels of EC (1, 2, 3 and 4 dS m-1) have been applied with an automatic system of irrigation starting from the generative phase of two different chemotypes: Δ9-THC (genotype 13) and Δ9-THC/CBG (genotype 16). Two female (pistillate) plants were used as sources for cuttings. Threeweek-old cuttings were placed in 5-litre pots with rock wool as substrate, with a 6 plants/m2 density. Two groups of 6 tables (1 m x 2 m) were used, resulting in 72 pots for each genotype. The light was supplied by 12 lamps of 600 watts fixed on the ceiling at 160 cm from the plants that produced about 24’000 Lux on a growing area of 24 m2. After harvest, the chlorophyll content, plant height and stem weight were measured. Furthermore, the leaf-flower production was determined and cannabinoid content was analysed on GC. Terpenes were identified by comparison of retention times with those of standards under the same conditions. The relative amount (proportion of profile) of each monoterpene was expressed as a percentage of total monoterpenes.

Results: The EC levels affected plant growth differently and the different parameters were evaluated. The portable chlorophyll meter (SPAD-502, Konica Minolta) showed that chlorophyll content in the leaves increased by increasing EC levels. The measured parameter at the lowest EC value is half of the value recorded on the plants fertilised with the highest EC. The plant height of both genotypes and EC level was correlated, and the highest plants were produced when levels EC 3 and EC 4 were used.

The effect of EC was positive on plant weight when the total and the leaf-flower portion were considered. Cannabinoid content, tested by cannabidiol (CBD), cannabigerol (CBG) and delta-9- tetrahydrocannabinol (Δ9-THC), was modified by the EC level of the fertiliser solution. The high level of EC tended to reduce the concentration of the three cannabinoids, although not significantly.

The optimal value of EC was close to 3 dS m-1 because this showed a positive effect on the total production of the three cannabinoids’ yield per square meter when genotype 16 is considered, while this trend was the same only for CBG and Δ9-THC when genotype 13 is considered.

No significant changes in proportions of the main monoterpene constituents were detected for any of the treatments. These results agree with data in the literature showing that the relative proportions (percentages) of constitutive monoterpenes are under strong genetic control and little affected by abiotic factors.

Conclusions: The salinity level has a major effect on Cannabis chlorophyll content and plant mass production. However, cannabinoid content in the flower and leaves changed only slightly, with an inverse tendency to the increase of EC level. At the optimal fertilizer concentration, the leaf-flower yields were 330 gr/m2 and 437 gr/m2 respectively using chemotype Δ9-THC/CBG and Δ9-THC.

optimal value close to EC 3.0

Thoughts?

 

[Iron_Lion]

I never had more problems then when I used an EC meter and a pH pen, things have never been better since I threw them both out of the garden room.

 

[smallfry707]

in other words the higher the ec ( more fert) = more yield and better buds?

 

[FreezerBoy]

More leaf, less THC. Doesn't sound very appealing.

 

[LJB]

More leaf, less THC. Doesn't sound very appealing.

I'm sorry, more leaf?

If total plant mass and flower production increases, naturally that's going to include some leaf matter.

As far as the latter, it does say " not significantly". How much is that, we don't know. It's too bad some more data wasn't included. I'd love to know where yield intersects with THC.

 

[LJB]

in other words the higher the ec ( more fert) = more yield and better buds?

More yield, and maybe "not significantly" worse buds. We don't really know for sure.

 

[DiscoBiscuit]

3.0???

Sounds like they're gonna start selling fertilizer.

 

[BurmeseDragon]

I never had more problems then when I used an EC meter and a pH pen, things have never been better since I threw them both out of the garden room.

If you could please be kind and inform me of how you correct your PH? With liquid nutrients I can't imagine eye balling adjustments.

Does anyone know how PPM different from EC, I know that the measurements are...but yes pushing the limits isn't always good and they didn't say what they fed with.

It's easy to push to far on some nutrients that stress and not giving those hormones and little tiff for taff things that do add up!

 

[LJB]

3.0???

Sounds like they're gonna start selling fertilizer.

That is funny, but assuming you're joking about Plant Research International, that is doubtful.

***

Folks, I'm not about to start indiscriminately feeding at 3.0, but clearly this raises some questions.

 

[Lazyman]

I typically feed until I get slight tip burn on the fans. The amount varies by strain, but healthy plants will take a ton of food before burn or curl. I foliar feed 1-2 times per week as well, hell you can use 30% dilute reservoir nutes as a foliar feed, the plants always seem to do better this way, for me.

 

[MediScrogs]

3.0 sounds awful high. How high are people going, really?

 

[PetFlora]

Like most studies the results depend on the input factors. Was the medium soil? Were other mediums (aeroponic) tested?

In a high pressure fog system you can push nutes into 2000 ppm range with no harm to the plant. In just about any other system that would burn the plants up

 

[Balazar]

I use House & Garden Aqua Flakes with the Dripclean solution. On some Island Sweat skunk in RDWC I can get the nutes higher than my meter can read! I estimate they are at 2200 ppm and not burned yet. When I get a strain I haven't done before I up it slowly until the leaf tips show slight signs of burning then I back it off about 200 ppm's.

 

[Balazar]

Like most studies the results depend on the input factors. Was the medium soil? Were other mediums (aeroponic) tested?

In a high pressure fog system you can push nutes into 2000 ppm range with no harm to the plant. In just about any other system that would burn the plants up

I just read through the most of the doc. That was just a small part of it. It seems to be the minutes from a cannabis doctors seminar or convention of some sort with lots of speakers on lots of different cannabis related lectures.

It is stated in the lab writeup that the plants are grown in pots of rockwool with an automatic feed system. I'm gonna guess because soil would create extra variables in the dose and type of fertilizer as well as a buffer. It also states that four degrees of nute strength were tested side by side using cuttings from two moms.

Methods: Four levels of EC (1, 2, 3 and 4 dS m-1) have been applied with an automatic system of
irrigation starting from the generative phase of two different chemotypes: Δ9-THC (genotype 13) and
Δ9-THC/CBG (genotype 16). Two female (pistillate) plants were used as sources for cuttings. Threeweek-
old cuttings were placed in 5-litre pots with rock wool as substrate

The conclusion says that higher doses of nutes make bigger plants (bigger as in more plant mass all together) but they don't really effect the concentration of THC or CBG in the plant. In fact with bigger plants there was a slightly lower concentration of THC and CBG.

Conclusions: The salinity level has a major effect on Cannabis chlorophyll content and plant mass
production. However, cannabinoid content in the flower and leaves changed only slightly, with an
inverse tendency to the increase of EC level. At the optimal fertilizer concentration, the leaf-flower
yields were 330 gr/m2 and 437 gr/m2 respectively using chemotype Δ9-THC/CBG and Δ9-THC.

They don't tell us what the NPK levels are though or exactly what there nute schedule or formula was.

to increase the EC level of the nutrient solution
without causing phytotoxicity, agronomically optimised formulas of fertilizers were designed by
PlantResearch BV to be used for this trial.

I don't think this is a big deal. We already knew that some strains are better than others and running your nutes as high as you can gives a better yield. We just have science to prove it now.

 

[LJB]

This is a good summary, which is something I'm not very good at providing. Thanks Balazar.

 

[antimatter]

uh.. more like 1.6-2 max

 

[LJB]

3.0 sounds awful high. How high are people going, really?

I do not run recirculating systems and have always kept the salinity relatively low: .6 EC for young veg, 1.0 for veg, 1.2 for early flower, 1.4 for late flower. And go from there depending on the needs of the plant.

Are there people that have had success going up to like 2.5 on ICMAG?

 

[SOTF420]

Higher ppm leves are maintained much easier in constant drip systems that are always recirculating and flushing out the nutes while providing the plants with what they need without drying and causing a nute salt build-up. If you are not using a system like this it is ill advised to go with higher ec leves, flushing is also much harder as well as the plant will store a good portion of the unused elements in reserve that can take weeks to use them all up.

 

[LJB]

Higher ppm leves are maintained much easier in constant drip systems that are always recirculating and flushing out the nutes while providing the plants with what they need without drying and causing a nute salt build-up. If you are not using a system like this it is ill advised to go with higher ec leves, flushing is also much harder as well as the plant will store a good portion of the unused elements in reserve that can take weeks to use them all up.

Yep it makes sense.

In the study they don't tell us exactly, but (and this is an assumption) going by from what I've seen as the methods used in other studies on salinity levels, when the authors say a "system of automatic irrigation", they are referring to a recirculating system.