Little brown spots on oldest leaves

[pontiac]

OK, so i'm getting these little brown spots on some of the older leaves. So far i've identified 6 or 7 leaf sets with this problem. Not alot, but i want to prevent any problems b4 it gets out of hand. The following pic shows the one in the worst condition, infact the other 5 or 6 leaf sets dont even come close to the damage extent on this leaf set.

The two plants are flowering right now, the TDS is at 700ppm (.5 NaCl factor), the ph is at 5.22. The problem seemed to occur only during veg, right now it seems like everything is ok. My nutes are GH maxi grow, GH maxi bloom, GH pH up/down, and epsom salts.

 

[MTF-Sandman]

Looks like nute lockout from PH issues to me...

The necrosis will never heal, so just keep an eye on the newer growth and as long as it doesn't spread you're good.

Having a PH of 5.22 seems a little low to me...even for hydro. Are the plants drinking more than they're eating? (ie. do you have to add more water than nutes vs. the original mix) Alot of times if the PH is staying low it'll be because of overfeeding (which will contribute to the lockout).

 

[pontiac]

I thought the the pH range for hydro should be between 5.1 and 5.5???

I'm thinking this is only an Mg defficiency, do you agree?

 

[MTF-Sandman]

I always aim for 5.8-5.9 with coco/hydroton personally....6.5-6.8 for soil. Seems like it's the sweet spot for uptake IMO. I really don't see any signs of Mag def...normally it'll show as a yellowing from the edges of the lower leaves and between the veins.

Here's a little bit I found in MyNameStitch's "The Complete guide to Sick plants,pH and Pest Troubles"

Ph Problems

One of the first signs of having a slight ph problem is, your plant having part of the leaves kind of twisty, spotty with brown, yellowish, red spots within each other.
Sometimes they don’t have to have all the colors, they could just be spots that have yellowish brown, or just reddish brown and can happen anywhere on the plant. Mainly starts on big fan leaves then goes to little leaves.
When this happens you need to check your soil ph, water ph before and after adding your nutrients. One of the biggest causes is adding nutrients like earth juice; they take the ph down quite a bit. Also can happen when you add bone and blood meal to your soil, that will throw the ph off as well, so it’s smart to test the mix before putting your plants into the mix. After the spots happen you will soon see nutrients being locked out, when that happens DO NOT ADD ANYTHING TO FIX THE PROBLEM UNTILL YOU GET YOUR PH FIXED!! Reason why is, because the plant isn’t absorbing that nutrient, by adding the nutrient it is deficient in, you are causing it to have a build up in the soil therefore can cause that nutrient to become toxic to the plant, because of buildup, to much buildup of certain nutrients will lock out other nutrients. In order to fix the problem you will need to first fix the ph and then if the soil is deficient in nutrients you can add it to fix the problem. A digital PH tester is the best tester to use as they are the most accurate. If you can’t afford a digital ph meter, then your best bet is to get ph testing papers. DO NOT get soil testers, those are the cheapest junk I ever seen and do not give good readings, so you cant rely on one of those. There are a lot of good ph testers out there, one of them is hanna. That is the one I use and is the best money ever spent! Vast majority of problems with soil ph comes from the soil if it has additives like peat moss, which is HILGY acidic..... and or the water you are using, as well as nutrient deficiencies from using the wrong ph for watering. You want to be careful when adjusting your ph, doing this over a week is the best idea, to fast will cause shock to the plant. If you can’t get a hold of a ph tester or ph test papers. If you have some dolomite lime, its always better to use it in soil rather than every time you water, imo and from others (Uncle Ben) That it really doesn’t stabilize as many people think it does, Soil pH and micronutrient availability are interrelated. Don’t Use to much lime to decrease the soil pH to a point where micronutrients can't be unavailable to plants. The micronutrients affected by pH include iron, manganese, zinc and, not as often copper. The problems when you apply to much lime can make it harder to correct your ph than what you would have when you didn’t add as much lime. You can always add more lime, but if you add to much you can’t remove it if you put to much lime in the soil. With great soil moisture, lime will work immediately and pH will start to change over a few months. However, it can take up to a year for the real benefit of lime to work. As the soil pH rises, the time it takes for lime to react decreases due to lower levels of soil acids. If you need to change your ph when its to high, if you choose to use lime it will not help as much as you think in lowering your ph, it would need alot of lime to lower your ph to a point where it would cause a toxcicity to the plants so look else where to use something to lower your ph rather than using lime.

So here at the bottom is a list of some buffers that are good to go with when raising and lowering ph!

Here are some ph buffers when your ph is too high: Use these SOIL PH Adjustments to lower your ph: sawdust, composted leaves, wood chips, cottonseed meal, leaf mold and peat moss. Sawdust, composted leaves, woodchips and, lemon juice, PH DOWN.

Hydro PH Adjustments: PH Down (vinegar and lemon juices are good for soil, but not recommended for hydro use) Thanks goes out to syko2 for that one! (Only quality PH buffers should be used to adjust ph and be sure the buffer and nutrient work's well together.)

Here are some that will raise the ph: use these SOIL Adjustments when your ph is to low: PH UP, dolomite lime, hardwood ash, bone meal, crushed marble, or crushed oyster shells, potassium hydroxide <--- Thank you Uncle Ben!

Hydro Adjustments: PH UP, sodium bicarbonate or lime.(Only quality PH buffers should be used to adjust ph and be sure the buffer and nutrient work's well together.)

 

[pontiac]

wow, thanks for the info! I'll raise my ph to 5.8 asap.

 

[MTF-Sandman]

Glad I could help. Watch the ppms and see what they do...it's a good way to track what your plant is using and will help to dial in your feeding schedule.

 

[mace_ecam]

pontiac, just do not follow this advice for raising pH:

Hydro Adjustments: PH UP, sodium bicarbonate or lime.

potassiumhydroxide or potassiumsilicate are a good pH up for hydro.

peace,

mace

 

[pontiac]

mace_ecam, i already have GH's ph up/down kit

MTF, i always keep my tds at around 700-750ppm @ .5 NaCl factor (980-1050 442 factor),

 

[mace_ecam]

700-750ppm @ .5 NaCl factor

thats an EC of ca. 1.5mS/cm, might be a bit low IMO for flowering, i used an EC of ca. 2.0mS/cm.

 

[pontiac]

hmm i remember reading somewhere (og growfaq?) that 1.5 should be the limit. Youre not the only person that said 1.5 is too low, I think i'll gradually bring it up near 2.0.

Thanks for the heads up.

 

[Blackmelo]

hey pontiac, although i also think your ph was a bit low it might also be a nute burn.
But might not...
I recently had pretty much exactly the same problem and it turned out to be a nitrgen toxidity locking out calcium.

 

[pontiac]

Hmm looks identicle, but i have to agree with the idea that is a ph problem. Cus the problem kinda breaks out after i re-adjust the ph to 5.1. The plants seem happy at ph 5.5 so i think i'll keep it there.

 

[Blackmelo]

nice one pont, listen to the sandman and adjust ph for now... If you are lucky, that is all it is.

 

[pontiac]

Well you could be correct about your idea about nitro toxicity. This problem mostley occured during veg, when i fed them high N nutes.

 

[Sauce]

Pontiac check your ppm rise/fall, that's what really matters. PPM is irrelevant considering all situations and strains will be different.

Hydro ph should be 5.5-6.2 with 5.8-6.0 being ideal.

A friend of mine had a similar problem in soil. He had too low ph (Earth Juice) and nute burn too. But he also had fungus gnats which might have done some damage.

 

[pontiac]

Cool, i kept my ph at 5.5 right after posting this thread. Hopefully this problem will never re-occur

 

[ourcee]

I'd say a bit of calcium and boron def mostly.