So, everything was going perfect (lots of new growing and nice looking seedling), but 4/5 days ago, a little yellowing started appearing at the tips of the first set of leaves. I thought it could be nutrient burn, since my soil comes pre-loaded with nutrients - enough to last 4 weeks, as they say - and I read it could be normal in a seedling with this type of soil and that it would pass. I waited and it got worse, so I asked around for help and most people said it was N deficiency, maybe due to pH lockout. Up to that point, I hadn’t fed it any nutes, nor had I measured the pH. I went to the shop and got both. I measured the pH pre-feeding and it was around 8 (color kit, so no precise measurement), but didn’t attempt to change it as it could only be N deficiency. So, I fed it and waited. Unfortunately, it only got worse: the 2nd set of leaves is also affected. Yesterday I tried to lower the pH with vinegar (only thing I got laying around the house) and I’m currently waiting for results.
Strain: Northern Lights
Grow medium: BioBizz All-Mix Soil (NPK 4-8-6)
Light size: 60W LED
Pot size: 1/4th cut of a 2L bottle
Nutrient type and schedule: BioBizz Fish-Mix (NPK 5-3-4) - None until 3 days ago and once
Watering schedule and pH of your runoff or reservoir water: 150mL each 2 days - only started measuring pH since 3 days ago and it was ~8
I’m no expert. However PH 8 is not enough acid. At 8 your plant is probably not getting any phosphorus, iron, manganese, boron, or copper. And minimal everything else except for zinc.
I had a nitrogen Overdose on a couple of my plants and the only part of the leaves that turned yellow was the very tip. Once I flushed, new growth was fine.
With pots as small as 1/4 of a 2 litre bottle, I’m not sure there’s enough room for all the roots that have grown.
I water only when my plants tell me to. My pots are much bigger, so I water once a week for the most part.
If this was my grow, my first order of business would be to figure out how to get the PH down around 6.5 without shocking the plants too badly.
I had to go to distilled water because my tap water is close to 8 due to all the limestone here. Even with that I sprinkle sulfur pellets on top of my soil using the package guidelines. When I water, they add enough acid to change my PH 1 full number.
The other guys here can give you better advice than I can, but this is all stuff I’ve learned here and by researching myself.
Yes, that’s what I found too. One thing in particular that caught my attention is Zinc. From what I gathered, it fits particularly well to the yellowing/browning of my leaves and to the stunted growth.
The small pot was only intended for the seedling phase and I planned (still planning) on moving it to a bigger pot.
Yesterday I tried watering it with nutrients added at a pH 6-7 and so today the soil is still a bit wet on the inside, reason why I don’t want to water it today. I’ll try to water it tomorrow with nutes at a pH ~6.5.
To address the tap water issue, that’s exactly what I found out after buying the pH test kit: the water’s pH is ~8. I’ll probably do the same and buy distilled water (unfortunately, one expense I wasn’t counting on).
Finally, about the watering tomorrow. Would you recommend flushing with distilled water and then water (agan with distilled water) the plant with added nutes?
Everything sounds like you are on the right track. Yes, you have the right idea and be careful not to cause other problems with overwatering and drowning your roots.
One mistake I made was to use miracle grow for acid plants to try to lower my tap water ph. End result was the PH was better, but then I had too much nitrogen. Eventually I flushed with distilled water. (question, are there drain holes in your bottle bottoms? If not, I suggest them as it really helps to not overwater.) The distilled water helped some, but I ended up using fox farm sledgehammer flush. I then used Espoma sulphur to lower the ph. it’s a simple 1 tablespoon per square foot of soil to lower 1 unit of PH.
The biggest lesson I’ve learned in this grow was not to make huge changes all at once.
Yes, there are drain holes. Thanks for the advice on the Espoma sulphur! I’ll search for similar products here. The other alternative is using a <insert brand name> pH down (which is just some acid not harmful to plants), but I’m not so fond of that.
Regarding the current situation, I watered it today with nutes and I hope for the best. I’ll keep you posted. Thanks again!
Unfortunately, the same thing (yellowing/browning starting at the tips) is going on, now attacking the near leaves. Tomorrow I’ll buy some distilled water and flush the soil. The sulfur is a good idea, but I haven’t been able to find it nearby.
I know it sounds weird, but sulfuric acid from an auto-parts store is pure and fairly strong, and doesn’t have any lead or other bad things in it. You can make a mix with this as a pH down. The only thing this adds to the soil is sulfur, not much different than what the epsoma would be doing.
The above University educational link mentions specifically the use of the same type of sulfuric acid that could be used in a lead battery.
A note of caution and safety – it is a good idea to always be wearing eye protection when working with strong acids, also a good idea to wear gloves.
When working with strong acids always mix acid to water, never the other way around. Pouring water into strong acid causes it to boil and it creates strong dangerous acid vapors that you would not want to breath or have floating around near your eyes or around anything indoors. Also the boiling action causes the acid to splash droplets everywhere.
I know this may sound scary but it shouldn’t, this can happen with the hydro store bought pH down as well. This type is often mostly phosphoric acid and therefore good if you want to be adding phosphorous to your soil.
Also if you think about it, normally anyone would be doing it the right way as they are adding the acid from the pH down mixture(the stronger acid) to the larger body of water that will be much less acidic, pH neutral or even slightly alkali with tap water of 7.5 or 8.0 or even higher.
So when mixing, remember always acid to water, never the other way around.
Thanks for all the answers. @MacGyver Stoner, I’ll try to go to some auto-parts store.
I’ve used demineralized water to water the plant twice during the last 3 days and I’ve changed most of the soil around the roots of the plants (if that changes anything). Last time the runoff pH was around 6.5 which is much better. I also took out most of the affected leaves. The browning has slowed down, but I’m not sure if due to the new pH or due to the reduced leaf area (less leaf area, less growing, less need of nutrients).
@MacGyver Stoner, really interesting link!!! I found online a store nearby that sells H2SO4 and I’ll be trying it tomorrow. I’m a bit sad though… the plant was growing really nicely and now it looks like at the end of the first week (in size), but worse looking.
Demineralised water will help. But excessive lime mineral build-up in the soil from the hard water could be keeping the pH high. And so you want to be checking the pH of the soil at the roots, the easiest way to do this is to water to the point of slightly over saturating the soil and testing the pH of the run-off from the bottom. If you use a cheapy garden soil probe, you need to check the soil when it is moist and near the root ball/root zone, likely the lower 2/3rd of the container for the most accurate reading.
Double checking the above, I see you are already testing the run-off pH. Also looking at the picture, you want to be careful you aren’t over fertilizing or over watering.
You might want to think about getting a EC/TDS/PPM meter to check the run-off for the nutrient concentration. An EC/TDS/PPM pen meter can also be found online at e-bay, amazon, etc for around $10 USD.
With this you can check the amount of nutrient salts dissolved in the nutrient mix or contained in your soil as judged by testing the run-off.
Most nutrient formulas are best at around 600-1200 parts per million, much higher than 1200 and you are more likely to get nutrient burn. The EC numbers would be around 1.2 to maybe as high as 3.0 for some adult healthy strains, but more of around EC 2.0 for most adult plants.
PPM might vary with certain TDS meters as they do the base conversion differently, but they all convert from EC, so EC is always the same but your meter might not read out in EC. The ppm numbers I gave are the reading most USA meters would use, others may vary, kind of like using metric versus imperial measurement.
The three conversion factors used for displaying ppm’s:
USA 0.5 ms/cm (EC 1.0 or CF 10) = 500 ppm
European 0.64 ms/cm (EC 1.0 or CF 10) = 640 ppm
Australian 0.7 ms/cm (EC 1.0 or CF 10) = 700 ppm
Thanks again!
Tomorrow I’ll buy some distilled water and flush the soil. The sulfur is a good idea, but I haven’t been able to find it nearby.
