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Cadmium mobility and accumulation in plant material

Hello everyone!

Anyone has scientific data about the mobility of cadmium and it’s diffusion through the plant?

We know it is easily moved inside the plant, but is there data on the rate of absorption,
meaning, let’s say there is 1 ppm of Cd in the growing medium, does that correlate directly into
dried flower material that will also have automatically 1 ppm?

Are there factors, beside the excessive use of silicate additives, that favors uptake of Cd (or other heavy metals) ?

Thank you very much



Absorption of all nutrients is based on size and proportional aubondence.

If you have heavy metals you are using an organic product as a fertilizer source. They only times I have had heavy metals as a problem is from to sources a really bad compost and poor choices in feed. One time was a too acid compost at at the time of steam pasterisation. The metals present at pasterisation spiked and we through the whole lot out, about 10 tons of potting compost. Did not buy the culprit again.

Heavy metals are the bane of organic growers.

There is a good USDA publication on heavy metals in organic production of vegetables. Has a very handy table, that shows the paths at a verity of pH level.

From the voices in my head


Thanks Ethan

am looking really for specific data on Cadmium and Cannabis, which of course is hard as heck to find because it was (and still is in many places) the devil’s cabbage… :roll_eyes:

The growing medium in the situation I am enquiring has shown very low levels of everything, cadmium shows up between 0.05 and 0.60 PPM . Yet flowers have shown above 1 PPM. Which is where my question about correlation and triggers comes from.

-If you have 1PPM Cd in the growing medium, do you automatically obtain 1PPM Cd in the buds?
-What triggers the intake?
-Where else does Cd come from? Air samples were taken, containers were tested, drip lines, floor cleaner etc all show clean.

because Health Canada will not allow more than 1ppm Cd in the buds, it becomes a real issue to figure this out. The growing medium has not changed source for 4 years, always tested the same , but this issue of Cd is just showing up now and not on all crops. So I’m trying to find where and why it’s doing it.



I need more information what is your fertilizer source. You can PM me if you don’t want to publicly say.

Uptake of all salts in your fertilizer and growth medium based on pH affect uptake in the plant. The simplest way to look at it is if I have 500 ions of salts in my mix.
Say 100 N, 100 P, 100 K, 100 Ca, 100 Cd. I will proportionally take up the ions indiscriminately, say one of each if the pH is optimal.

The plant does not discriminate in uptake, but pH does play a role in which ions look more attractive.

I find from experience that organic source fertilizers are my biggest potential sources of heavy metals. Fish byproducts used in lots of organic products are heavy metal sources as is products that contain things similar to milorginte. If I am try to produce an organic product that people consume. I have problems sourcing fertilizers that don’t cause me heavy metal problems. If you make teas all bets are off. I had a organic vegetable grower in Kansas City area who made teas from his chicken manure. We found that his chicken shit was high in arsenic and it was 100% soluble in his tea process. We change to his goat manure and got ride of the arsenic. I think the arsenic was coming from the oyster additive to his feed supplement for egg production. The chicken mostly where free range but he gave them extra calcium for stronger shells. He did change is calcium supplement to a non seafood source, I don’t remember what he picked.

I have not had problems with growing medium as a point source of heavy metals. But, I source very carefully. If the tomato growers are using it I generally feel I picked a good product. For example the rock wool from oasis is a good product. Growstone looks beautiful @paula.costa I think she is on the forum and she can speak to these issues better. I personally like growing in MetroMix 510 and 810. But, would definitely be using a hydroponic medium for maximum root hair production. Bunt’s book on “modern Potting composts” Oxford Press has a good explanation of source contamination of heavy metals, in production. Plus it just a readable book.

I think I would be sourcing my fertilizer from HGV or my old time favorite J R Peters HGV is on the forum @ron

Ron, can you add something here and maybe make a sale.

But you have Cd somewhere in your supply chain. What goes in is what comes out.

From the voices in my head,

PS you might owe me a pair of socks. :upside_down_face:

1 Like

He He He he!

Socks are the xmas gift that our US sister company offers… unfortunately Canada doesn’t get so much comfy goodies :wink:

Cd in the fertilizer tested at 0.009ppm in the A 0.025ppm in the B part. no organics are used, no additives, no magical gimmick… I do have to trust they aren’t doing anything behind my back. it is state of the art medical facility with a bunch of over zealous people keeping things ultra clean.

really nothing’s changed over the last 4 years ( I know everyone grower says that, but its true LOL)

why it is suddenly showing up now is very puzzling and am inclined to think they are hiding or lying about something and are pointing fingers away from them selves and perhaps they are not telling the whole story.

Anyhow in the mean time I do have to gather as much data as possible. The interesting part, is I would also expect this to happen more on the organic side of their grow and somehow it always came out clean.

Am beginning to think it would offgas from their new ballasts or something Cd is often found in steel and other chromed material. Or it may have came in the air from the newly built expansion they made and perhapsit wasnt present in the air anymore when they tested it, but was there long enough to enter stomatas and stick in there in high enough amounts (2 ppm) which is ridiculously low but still above the allowance.

Once lead was showing up, they also blamed nutrients and medium, but then we found out their lab were using cheap metal grinders… which were leaching Pb on the plant material. I love this detective work.

Thanks for the ongoing help !



The only way I have been able to track source containmention is with the help of the accounting people. I get a report on every purchase.

Zinc plating, plastic that are not food grade, rechargeable batteries, water. These are places to look.

I think cadmium Sulfate is the mostly form I have seen growers of horticulture crops complain about CdSO4·H2O. It is a monohydrate and is a real pain to find.

I don’t think the lighting balest are a likely source unless they are leaking. Cadmium is sometime a contaminate in aluminum. I have heard of tomato growers accidentally pulling both aluminum and cadmium from aluminum flood benches when the pH of the irrigation water was bellow 6.5, but that was years ago and in Canada in the greenhouse belt, around 1995 or 96.

I know at mizzu when we paturized with live steam from the university power plant we had to watch for heavy metals. We had agronomy test our mixes twice a year for heavy metals.

Good luck

Heavy metals are QA bane.

From the voices in my head


I was thinking about the ballast boxes, because they are set about 2feet above canopy, are all new and all come from china, so I’m thinking as they heat up the china paint might be offgassing or even the steel of the box itself.

you make a good point about the aluminum, maybe the reflectors could be leaking it out, they do get quite hot.

It will be a long detective work, just like inspector Colombo… I know who is guilty, but he is certainly not going to cooperate, especially if they are already trying to pin the murder on me :wink:

thank for the help, very appreciated