Nutrient toxicity or incorrect ph?

I’ll try to give you as much information as I can.

Variety: Purple Haze


Growing medium: FoxFarm Ocean Forest organic potting soil (~ph 6.3-6.8)

Nutrients: FoxFarm’s Big Bloom (20ml per gal), Grow Big (7ml per gal), Tiger Bloom (7ml per gal) and Open Sesame (1/4 teaspoon per gal)

Water: Tap water (ph 8.3 adjusted to 6.1 prior to mixing in nutrients)

I just bumped up the Big Bloom from 10ml to 20ml two weeks ago. No twisting or burnt leaf tips. But I have the strange necrosis developing interveiniously. In all my years of growing (26 years) I have never seen this. Any ideas?


Oh yea, this is appearing on the newer leaves at the top of the plant.

It looks like a low level potassium deficiency by the information and description you gave us, this could potentially be caused by a pH imbalance. A lockout of potassium could also be caused by other imbalances, maybe your tap water is too hard at a starting pH of 8.3?

If the starting PH is 9.3, I would definitely monitor the PH closely.

you are definitely getting a lot of Nitrogen, and MacG could be right; If you are running an alkaline PH above 7.0 you have a high % chance of Potassium deficiency.

ON another note; I went an re0read your post.

Personally; I PH after adding all my nutrients because, some brands, such as Foxfarm have a PH buffer in the concentrate. I could be wrong, but check it out next time.

What is the PH of solution after mixing solution?

Also; If you are in veg, and using Ocean Forest; You may be applying to high a concentration of solution (EC, TDS) What is strength of solution?

Some more info;

They are 3 weeks into flowering.

Latewood, my waters’ starting ph is around 8.3

This morning when I watered, my ph meter went haywire. Using a calibrating solution of 4.01 my meter would repeatedly calibrate to a 5.3 Not sure if the solution is bad or my probe on the meter is bad (probe is my guess). I was in a hurry and did not take a ppm reading. Next feeding I will take a ppm reading and will mix my nutrients and take a ph reading with a new meter before adjusting the ph.

Yes, being sure to adjust your pH after mixing your nutrients will give a more accurate reading of what pH is actually being fed to the plants. Be sure to check the ppm of the runoff coming out of the soil, or the concentration of the nutrient fertility in the soil itself with a soil probe, to be sure you are not having a build up of nutrient salts that could be contributing to this problem.

Yeah; I know; It was a typo. (probably, because, I am blind in 1 eye, and can’t see out the other. :wink:

It is a fact that under consistent use; Probes go bad. I spent a lot of time talking with Milwaukee Instruments, because I use an SM802. multi meter. every couple years I have to buy a new one.

Best way to keep your probe from taking a dump…Buy the storage fluid they sell, and use it. Never let the probe dry out.

I think you are on the right track, and glad to see a grower being proactive, when it comes to buying a meter. Peace

MacGyver: I have always been under the assumption that it was important to have the ph of the water adjusted at the starting point. To clarify, I had thought the ph of the water was more important than the ph of the final solution. I’ve been using Botanicare’s line of products for years and recently switched to Fox Farm. Never had any issues with Botanicare before. I will follow your advice and whip out the ppm meter on the feeding solution and the runoff. I believe I have a nutrient probe, which I will have to dig up, and I will check the nutrient concentration of the soil.

Latewood: I guess getting nearly 5 years out of my Oakton Ecotestr ph2 isn’t bad. Probably because I’ve done like you’ve advised and kept 4.01 solution in the cap at all times. Guess it’s just time to get a new meter. Not good timing, money’s tight…

Kinda off subject, but I thought id throw in a little eye candy. Here is my 10 foot plus Super Skunk, which turned out awesome!

Nice pic, thanks for sharing.

It is nice to start with super low EC/PPM and a near neutral pH as you would with R/O water or distilled water. Water with 0.0 EC/PPM will pretty much always have a pH of 7.0 as it has absolutely nothing in it to make it acidic nor alkali.

However, if you think about it, what is important is what is going to be present at the roots, that is where it counts. When you add nutrients to water you are going to be adding the nutrients that can be acidic or alkali in the nutrients nature. Nitrogen can add acidity to your water as in nitric acid, as can sulfur as sulfuric acid. Calcium can add alkalinity to your water as in calcium carbonate. Many nutrient mixes will move your water’s pH on their own towards about a 6.0 - 6.5 as they are formulated to do so, but they are usually manufactured to be used with very pure water and are assuming the pH will hold after it has been mixed. On the other hand if you have hard water with a high starting pH above 8, there is no telling what will happen after the chemicals in the nutrient mix react with the chemicals and minerals in your water. Adjusting pH before adding your nutrients is just adding more chemicals to your starting water that will further react with the nutrients after you add them.

It is probably best to mix in your nutrients, give it a really good stir and then maybe give it 5 to maybe even up to 15 minutes to see how after everything has interacted with everything else, what your pH ends up. You may not have to add nearly as much pH adjusters to get it where you want it. And then you will know exactly what pH you are sending to your roots.