Can copper be safely used in hydroponics to keep roots out of drains?

Advanced Techniques
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I just ran across a thread on another forum with ideas on stopping roots from going into bad places like drains. One of the ideas was to use copper pipe, mesh etc, to stop the roots. The idea being that the roots will not grow over, through, or past copper.

Apparently, General Hydro and other places sell copper grommets, inserts etc to do this for drain pipes.

https://www.onestopgrowshop.co.uk/products/iws-copper-root-control-insert

https://www.ebay.com/i/302402072612

The silk screen I am using to block the drains in the NFT tote was working perfectly - until the roots found a flaw in where I had it sealed to the tote bottom. I had to cut through the silk screen to get in and cut the roots back.

Im going to lay a piece of copper wire in on top of the drain holes and see how it does.

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Oh - I tossed some perlite into the NFT and Membrane totes to see if the roots like it any better than the fabric. After 2 days, the roots in the Membrane tote are starting to grow into the perlite. The NFT roots dont seem to like the perlite any better than the fabric.

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Is using copper in contact with the nutrient solution safe? I’ve heard this could lead to an overabundance of copper in solution possibly leading to toxicity.

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I have no clue. Its possible I guess. There must be some reason the roots dont like copper, so Im guessing it hurts them some way.

Maybe I better do some more research. So far, all I have found are anecdotal comments that are not based on any real testing or science. That is not unusual in this hobby :smiley:

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True that. idk, for certain.

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I spent the last hour searching for info on copper in hydro setups and all I can find is anecdotal information. The vast majority of that is negative - along the lines of “Dont use copper or all your plants will die and you will go bald and have limp what ever issues!!!”

But, I also found a few places where people in commercial grow situations do use copper to stop roots. Plus, some people are using copper water chillers with no bad results.

There were also some comments about it not being the copper itself, but an electrolysis issue. That part makes more sense to me. Even a tiny current leak from faulty insulation on a submerged pump would cause galvanic corrosion. That would very quickly erode the copper, putting tons of it into solution.

I have no electrical items in contact with my water other than a brand new aquarium heater - which is rated for full submersion, so I think Im ok on that, but I will check for leakage first.

In the mean time, I placed one end of my copper wire in some nute solution. Im going to let it sit there for a few days and see if it shows signs of corrosion or erosion. If there are no signs, and my leak test looks good, I will try it.

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The first thing here I have experience with as I had fish tanks for 40 years. Watch that heater if the water every get low than recovers with water they blow up. :confounded::sob:

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Oh yeah, and its one heck of a mess and dangerous to boot!

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Huh. They’re recirculating the nutrient solution through a copper exchanger (as opposed to using a glycol loop). That’s a ton of contact area and time and would say it sounds like a non issue then.

LaMotte has a test kit for copper on Amazon. Would be interesting to quantify this. Can I send you a test kit?

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If you are willing to do that, sure! I will wait until I get the test kit to introduce the copper so we can get a baseline value.

I think I will do two tests.

One with the copper just sitting in a jar with nutes. That way there will be no possibility of electrical shenanigans adding to the issue.

Then, if that looks safe, I will put the copper in my tote and see if the rez values change as well as see if it actually stops the roots. No point in using the copper if it doesnt stop the roots.

I’ll PM you shipping info.

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Cool! Will do. Sending you this: Lamotte Company 3619/EC-70 Test Kit Copper

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Ive started off by taking two samples of water from my rez. One I will set aside as a reference. I put a piece of copper wire in the second sample leaving one end sticking out. I will test both samples when the test kit gets here and see if there is a measurable difference in copper levels. I will also look closely at the copper wire where it was in the sample to see if there is any discoloration , corrosion, etc.

if that looks good, then on to the root test and measuring the rez water over time.

One thing I have not been able to find is what levels of dissolved copper are good/bad for the plants? Anyone have any references for that info?
.

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Spent some time trying to get an idea of what concentrations might be of concern. Notes for reference:

From Greenhouse and Nursery Management Practices to Protect Water Quality, Julie Newman

Certain ornamentals show sensitivity at 0.5 to 1.5 ppm.
Chrysanthemum, miniature rose, and germaniums show toxicity at 0.32, 0.15, and 0.50 PPM respectively.

From Hydroponics: A Practical Guide for the Soilless Grower, J. Benton Jones, Jr.

In hydroponic systems, CU toxicity can result in root damage if the Cu content of the solution is too high [>0.1mg/L].

e.g 0.1ppm

…normal concentration range for Cu in nutrient solution is from 0.001 to 0.01 mg/L…There is evidence that if a chelated form of Fe is present in the nutrient solution, Cu uptake and translation in the plant can be imparied…

From “Interactive effects of copper and zinc accumulation in Portulaca olearcea stem cuttings, through hydroponics”, Jayanthi P., et al.

The results of the present findings established that both Copper along with Zinc ions in aqueous solutions interferes with the regeneration potential of the stem cuttings by reducing the root growth and increasing their decay. The magnitude of toxicity was found to be higher at a combination of Copper and zinc at the concentration levels beyond 0.1 mg/l for Copper and 2.5 mg/ l for Zinc.

From "Impacts of EDTA on Uptake and Accumulation of Cu 2+ by Spinach ( spinacia oleracea L. ) Seedlings Replanted in Hydroponic Solutions, Dagari,M.S., et al.

The effects of EDTA on Cu2+ uptake by spinach (spinacia oleracea L) seedlings replanted in hydroponic solutions in a greenhouse were investigated. Four week old seedlings were exposed to various doses of Cu2+ (0, 5, 10, 15, and 20mg/L) and constant concentration of EDTA (10mM). During the exposure, the plant protected itself from the damage caused by Cu2+ uptake by using the antioxidant,(proline). The photosynthetic pigments (i.e.chlorophyll a, chlorophyll b and Carotenoid) gradually declined. In this study, dry weights and lengths of roots, shoots and contents of the photosynthetic pigments of both chelated and unchelated hydroponic treatments were investigated. Changes in photosynthetic pigments, root and shoot weights and lengths were significant (p < 0.05) with respect to addition of EDTA to different concentrations Cu2+ compared to unchelated treatments of same Cu2+ concentrations. Hence, chelation enhanced Cu2+ uptake with adverse effects on the plant.

Edit: 5/29

From, "The effect of copper toxicity on the growth and root morphology of Rhodes grass (Chloris gayana Knuth.) in resin buffered solution culture, A.R. Sheldon, et. al.

Adsorption of Cu is highly pH dependent and phytoavailability of Cu increases with decreasing pH. As pH increases, both total soluble Cu, and Cu2+ activity decreases (Tye et al., 2004).

The effect of Cu toxicity is largely on root growth and morphology. Copper tends to accumulate in the root tissue with little translocated to the shoots (Marschner, 1995).

The critical concentration of Cu in the nutrient solution associated with a 10% reduction in growth of Rhodes grass was between 0.6 and 1.1 uM.

e.g. between 0.04 and 0.07 ppm for Cu2+

The interesting thing is, when we look at formulations for water soluable nutrients, the copper content is much higher than what those papers suggest.

For instance, Ultrasol indicates the following at EC of 1.84 mS:

Ultrasol
Total Nitrogen 130
Ammoniacal N 7
Nitrate N 123
Phosphorus 66
Potassium (K) 240
Calcium 123
Magnesium 52
Sulfur 90
Boron 0.5
Copper 0.7
Iron 3
Molybdenum 0.1
Manganese 1
Zinc 0.4

Likewise, Megacrop indicates the following at an EC of 1.67:

Megacrop
Total Nitrogen (N) 158.5040
Nitrate Nitrogen (NO3-) 152.1563
Ammonical Nitrogen (NH4+) 6.3403
Phosphorous (P) 38.0431
Potassium (K) 190.7790
Magnesium (Mg) 30.1152
Calcium (Ca) 103.0256
Sulfur (S) 17.4353
Iron (Fe) 1.2682
Zinc (Zn) 1.7433
Boron (B) 1.2682
Manganese (Mn) 1.2682
Copper (Cu) 0.7925
Molybdenum (Mo) 0.1584
Silicon (Si) 1.5849
Total PPM 545.9994

I do not know how to interpret this at this point other than, perhaps, they are taking into account the effect of iron chelates in solution on the uptake of copper.

Then, some other formulations that are more aligned with the research papers:

Jack’s Hydro-FeED(16-4-17)
Nitrogen (N) 150
Phosphorus (P) 16
Potassium (K) 132
Calcium (Ca) 38
Magnesium (Mg) 14
Iron (Fe) 2.1
Manganese (Mn) 0.47
Zinc (Zn) 0.49
Boron (B) 0.21
Copper (Cu) 0.131
Molydenum (Mo) 0.075

Jack’s Hydroponic (5-12-26) + Calcium nitrate
Nitrogen (N) 150
Phosphorus (P) 39
Potassium (K) 162
Calcium (Ca) 139
Magnesium (Mg) 47
Iron (Fe) 2.3
Manganese (Mn) 0.38
Zinc (Zn) 0.11
Boron (B) 0.38
Copper (Cu) 0.113
Molydenum (Mo) 0.075

ModifiedSonneveld’s solution
Nitrogen (N) 150
Phosphorus (P) 31
Potassium (K) 210
Calcium (Ca) 90
Magnesium (Mg) 24
Iron (Fe) 1.0
Manganese (Mn) 0.25
Zinc (Zn) 0.13
Boron (B) 0.16
Copper (Cu) 0.023
Molydenum (Mo) 0.024

Peter’s Professional Hydroponic Special (5-11-26)
Nitrogen (All Nitrate) N 50
Phosphorus P 48
Potassium K 216
Magnesium Mg 60
Sulfur S 80
Iron Fe 3
Manganese Mn 0.50
Zinc Zn 0.15
Copper Cu 0.15
Boron B 0.50
Molybdenum Mo 0.10

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You are much better at searching than I am :slight_smile:

That test kit looks like it reads from .05 to 1.0 PPM, so that should be sensitive enough for our purposes.

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Those bugs may be regular fruit flies, but I still have not caught one to get a decent pic. I put a DIY trap with some soda in a jar to see if I can get one.

Up-date on the copper test.

The wire I am using is some 14ga copper electrical wire. I stripped it and sanded the entire thing with some 400 grit sand paper to get rid of any existing corrosion, discoloration, etc and get down to fresh, bare copper. One end of the wire has been sitting in the nute solution for roughly 36 hours. I stir it every once in a while.

Here are some pics of the wire. The first pic is just the setup so far.

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This is a macro shot with my cell phone. The part to the right of the arrow has been sitting in the solution. You can just see an angled line of discoloration.

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This is a close up using a USB scope. The line is very clear. Above is dry, and below is where it is in the solution.

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I can’t feel any ridge at all, but that doesnt mean much. This could just be some surface deposits or oxidation and it may or may not mean any copper is entering the solution. We will have to wait until the test kit gets here - possibly later this week or the first part of next week.

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It’s the “low-range” test kit and it seems that it’ll be able to cover the concentration range that may be of interest. It is, unfortunately, color based so it may be a bit of a challenge comparing against the color reference card if the solution has significant tint. Keeping fingers crossed that it will produce usable results for your test.

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Good photos. Good call on removing the initial oxidation layer. Yes, looks like oxidation of the portion exposed to air. PH in the 5.6-6.0 range or so?

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Im not sure of the PH - my meter died and I had to send it in for repair. Im using drops to test now so as near as I can read the colors - its around 6 ±. Probably a hair under.

I didnt think about the color of the solution making the test difficult to read. My nute solution is not real dark. I can tell colors fairly well on the PH testing, so I hope it works out.

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Oh, right. Sorry, you did mention that. Ack, short term memory…

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I’m seeing lots of conflicting information of copper concentrations (specifically with nutrient formulations). The research papers seem fairly consistent, though. I’ve sent Harley at NPK a couple of questions and will be speaking with him later this evening. I’ll see if I can get his input on this if he has time…

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Cool!! Looking forward to hearing what he has to say.

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