PH level is too high and lower leaves turning pale green to yellow with brown spots.

[Papachez]

Hi There,

I have been reading numerous forums on this site and have found them all to be most helpful when seeking advice with growing weed. While I have experience in growing outdoors, this is my first attempt to grow in a tent under LED lights and I would really like some advice and help regarding the current PH levels in my pots.

• 4’x4’x7’ Mars Hydro tent with TS2000 led light
• 300wt
• Currently on maximum setting
• 21 ½ inches from top of pot to light (too close?)
• 1[SUP]st[/SUP] time grower in tent but have previously grown outdoors
• Growing organically with homemade compost/worm castings
• Feminised seedlings 4 weeks old and currently shooting 4[SUP]th[/SUP] node – 2 x Bruce Banner 3 and 2 x Star Dogs
• 1[SUP]st[/SUP] transplant at 2 weeks from seed pot to 1.5lt pot.
• 2[SUP]nd[/SUP] transplant from 1.5lt pots to 4lt pots at 3 weeks due to roots reaching the bottom of all pots
• 1.5lt pot soil mix – equal parts compost and coir, ½ part perlite and ½ part sand and PH level of 6.8 and no other nutrients. Plants grew really quickly with roots reaching the bottom of the pots within 6-7 days hence the decision to pot on.
• 4lt pot soil mix – 9lts coir (3lts of water and 1.5lt compost tea) with equal part compost, 5lts perlite, approx. 1lt vermiculite and approx. 50gms of bird guano but PH level of 9-9.5!!
• Must be said that the first batch of compost was 5-6mths old while the second batch is only 3-4mths old, so I’m wondering if the mix is still too hot as there has been no change to the “ingredients” of our compost
• Applied weak solution of vinegar and water – 35mls vinegar to 500mls water 2 days after transplant with small temporary reduction in PH level at surface but no change to PH level at 50-60mm depth
• Then applied Seasol (NPK ratio 12%,1.4%,7%) at a ratio of 30ls Seasol with 1lt water (250mls per plant) next day to increase Nitrogen levels in an attempt to lower the PH level but again with little change.
• Flushed all pots 4 days after the first application of Seasol and initial testing showed little change in PH as went from 9 to 8.5.
• I am now planning to apply another solution of vinegar but increasing the ratio to 50-60mls vinegar per 500mls of water as well as increasing the volume to 2lt to give each pot 500mls, but not sure if this will have the required effect???

I have read a fair bit online regarding increasing/lowering PH levels in organic soils and have come away more confused than when I started for three main reasons: compost is used to both lower and increase PH levels in soil. In addition to these two reasons, I have also read that if using an organic soil, then high and/or low PH levels are not too much of a concern as the microbes within the soil will buffer the soil enabling the plants to take up the nutrients in the soil.
I would really appreciate some feedback and advice as to what the issue is regarding the high PH level, and what I am doing wrong so I can correct it before it seriously impacts on the health of my girls. The pics were taken a couple of days ago but have managed to keep growing, as it’s taken me a wee while to pluck up the courage to post anything, including pics about growing weed online.
Thanks very much for reading my post!
Cheers

 

[stridex]

pH in the 8-9 range? Ouch that must hurt...


I had a similar problem myself, caused by not always watering until runoff, resulting in salt build-up and elevated pH.
They we a few weeks into flowering so had to be careful...

Scraped off as much top-soil as possible.
Got some pH 6.5 soil, mixed with some water. Used a pH- product to bring it down to 6.
Slapped it into the pots then gave nutrients as usual.

Your problem looks a lot easyer to fix though, they are still seedlings.
Just transplant into suitable pH adjusted soil


/stride

 

[Rwise]

Forget the vinegar, it is temporary at best (does kill chloramine in tap water), I use sulfur (pelleted) to buffer the soil. Sulfur when mixed with water and air make sulfuric acid in the soil.
Do this test, PH your water with the vinegar, let it set 12 hours and recheck it.
Black Strap Molasses gives a PH down also.

 

[stridex]

Forget the vinegar, it is temporary at best (does kill chloramine in tap water), I use sulfur (pelleted) to buffer the soil. Sulfur when mixed with water and air make sulfuric acid in the soil.
Do this test, PH your water with the vinegar, let it set 12 hours and recheck it.
Black Strap Molasses gives a PH down also.

Agreed,

Elemental Sulfur can be used, but have a slow "release time". Might be good as a long-term solution though. Full details here

As a fast-acting alternative I've tested Iron Sulphate in granules. 1 teaspoon dissolved in 10 litres of water, flush with it. Brought pH down one mark. Details here
Applied on one plant only, which totally boomed after the treatment. Now with the biggest and healthiest buds of them all!

Strongly recommend testing on one plant only...


/stride

 

[Papachez]

Good morning Stridex and Rwise,

Thanks very much for your comments and advice. Given all 4 plants are still in the seedling stage, I am leaning towards making another batch of soil from the original compost as this mix returned a 6-6.5 PH reading, rather than trying to solve the issue with plants included. I figure I have already "lost" a weeks growth the the PH issue, so potentially losing another 2-3 days of growth while the plants adjust to the new soil is not a big thing and will probably be the least invasive on them. This will also give me an opportunity to correct the high PH levels of the current mix using the suggested Iron Sulphate in time to use in the final transplant once tipping has been completed, without risking the overall health of the plants.

Thanks again and stay safe!!
Papachez