What concentration of nutrients is too much for plants and can cause burning?

[kwisatz]

I have a question on what concentration of nutrients (mg/l) is too much for plants in that it can cause the leaves or roots to burn? I know of some people trying to add DIY tabs (containing 1 mg of dry KNO3) into their substrate, and then saying the roots of their plants were just burned. So to add dry KNO3 into the substrate seems to be bad idea (maybe too high concentration of K/NO3. When we are dosing dry salts into the water column the chemicals are diluted so its much more safe for plants as well as for us to reach some dangerous levels.

Does anyone know what levels are still safe (for water column vs. root fertilizing)? Better yet what is the critical level for each nutrient (NO3, PO4, K, Fe ...) before it harms our plants?

I know we speak a lot of EI dosing, so the IE recomended levels should be OK. But what about sediment levels? We're adding a different stuff into the sediment, but it seems no one knows how much is OK vs. how much can cause burning roots.

I'm quiete confused with this matter, because in ADA AS/PS there is quite (extremely) high concentration of NH4, PO4, Fe ... but still the roots have obviously no problem with it. So why they have problem with dry KNO3 ... ?

Any suggestions/ideas/answers welcomed.

[Tom Barr]

NH4 is the only nutrient I know of that will burn any plant, and your tank will be dead if you get to that level and no fish etc.

There is no known level of KNO3 I'm aware of that will "burn plants". 160ppm etc did nothing, many others have repeated this and had no issues of any sort.
Often times people will make a dosign mistake and really over dose a lot, 3-10 x etc............no one has killed fish or shrimp or plants in this manner.

They may have killed them from doign OTHER things, but when all the livestock and plants are fine.....it falsifies such claims easily and with a high degree of certainty, speculation however offers nothing more than speculation..........there is no support for the claim in other words.

[yme]

one caution....

make sure if you add dry fertilizers that everthing is dissolved. pieces of ferts can burn plants.

greets,

yme

[Crispino Ramos]

I want to share this article about the advantages of potassium nitrate compared to potassium sulfate. To read the article, please click on this link - http://www.kno3.org/en/product-featu...-and-k-sources .

Word of caution - potassium nitrate can cause fire or explosion at high temperature. I know we want to dissolve the crystals/dry ferts in water fast by heating up the mixture in the microwave oven. I would advise you not to boil the solution in the microwave oven. Use lukewarm water instead and stir patiently until the crystals are completely dissolved.

[kwisatz]

Thank you VERY MUCH for all your replies.
So just to be sure: If I add KNO3 (or other dry salt) in a pill to the substrate and the salt do not dissolve completely, there is a danger for the roots to burn when they come into direct contact with the undissolved salt. Is that correct? But if the salt dissolves in the water, than it is extremely hard to reach a lethal concentration for the roots to be burned. Am I right?

PS: Tom, in one post (http://www.barrreport.com/showthread...0332#post40332) you mentioned that you've gone to 200mls in 75 liters of Flourish. Did you use Flourish Iron (200 ml of Flourish Iron in 75L tank would give 26.7 mg/l Fe) or Flourish Comprehensive (200 ml = 8.5 mg/l Fe)? And how long (months/years) were you adding it + was it weekly or daily dose? I am just curious.

[Tom Barr]

3 weeks time.

No issues.

Plants are pretty tolerant of metals, Copper is the exception.
KNO3 will dissolve rapidly, just dissolve it, add it to the water.
No good reason to add to the soil, it'll just leach out in a few hours anyway.

[Crispino Ramos]

Thank you VERY MUCH for all your replies.
So just to be sure: If I add KNO3 (or other dry salt) in a pill to the substrate and the salt do not dissolve completely, there is a danger for the roots to burn when they come into direct contact with the undissolved salt. Is that correct? But if the salt dissolves in the water, than it is extremely hard to reach a lethal concentration for the roots to be burned. Am I right?.

If you are referring to fertilizer tablets, they are safe for plant roots. Most fertilizer tablets are mixed in clay based material to slowly release nitrogen, phosphorous and potassium. I have observed that plant roots like to clump around the fertilizer tablet and make the plant bigger than the others around it. It's my observation when I pull some plants and the fertilizer tablet is still intact. It's the same way with Osmocote Plus fertilizer capsules/ice cubes.