Raising potted soil pH

[Anoobis]

Hello All

I have a few seedling on the go, maybe 2 weeks old (indica). I also have a plant maybe 5 weeks old, looks sativa dominant. The seedlings looked nitrogen deficient despite it being fresh soil mix with plenty of worm castings and blood n bone amendments (also coco coir, perlite, and some garden lime mixed in). I gave them a foliar spray of a generic fertilizer and they perked up immediately in colour. But it got me wondering why it was needed in the first place given the soil was fresh and should be fertile, so I grabbed a soil pH tester. The soil was very acidic, as low as 5. So applied a small amount of garden lime on the top of the soil and watered it in, but it only came up to around 5.5 in the few days after. I dusted off an old pH pen for hydro and I tested the local water supply. Its also really acidic at 5.5. What I am wondering is how should I address the soil pH. I will obviously need to make the water more alkaline before I water my plants, but if I am dissolving garden lime how high should I raise it to also address the soil pH. Do I keep top dressing and watering in lime, or should I fix it purely by raising the water pH with the lime? My 5 liter watering can has water I raised to 6.9 with the lime, should I just keep watering and retesting the soil with that until its fixed, then drop waterings back to 6.5? Or should I be slightly more aggressive?

I just noticed what I think are magnesium deficiencies in the older plants leaves, so I applied some Epsom salts as a foliar spray, but I suspect the main problem is nutrient lock out because of the soil pH. Any advice is appreciated. Thanks.

 

[Blew Hiller]

Pics help. Sooooo much going on for that poor seedling...you are changing so many variables at once, you need to start being scientific and choosing one thing to alter at a time. For example, you are better off making soil amendments to the plants next pot rather than the current pot. Seedlings don't need (and shouldn't get) fertilizer (or epsom sprays) ....they have all they need this early in life.

Sometimes we overthink and over love our plants...to death.

 

[Chris Scorpio]

Wow, lots going on for sure

Like Blue said, reel it back in, maybe even transplant to basic soil till they recover

Not sure if yer an experienced grower of cannabis, but normal HOT soil used for veggies don't work with cannabis, it requires totally different levels of nutes

Build it for cannabis or use basic soil and use nutes designed for cannabis

And pics for sure

 

[Anoobis]

A couple of shots of the seedlings . They are a little bit green for my liking, but after the foliar spray that is to be expected. But prior to that they were anaemic yellow. I am confident the leaves were abnormally yellow based on previous experience, and a diluted foliar spray was ok to address the issue. But even at half strength nute they responded a bit more than needed. I understand some will disagree but i dont have photos of them prior to the spray. They looked sickly

The leaf shot showing the deficiency is from the older plant (5 or so weeks, i hadnt bothered to note the date it germinated. The seeds were so old they were proving a challenge to germinate). I havent grown anything in 20yrs, and prior grows were hydro (flood and drain) or coco hand watered. This older plant i dont plan on flowering. It was from 20 yr old seed i had frozen, and i was using as a test grow. Ive been experimenting with topping/mainlining techniques. I am not an expert by any means but it looked like a magnesium deficiency to me. Hence a weak epsom salt spray.

I cannot transplant pots to adjust soil ph. They are already in their final pots. This is a micro grow in a very confined space. I will post some shots of the filing cabinet i converted. I have 3 Chung Lee's, and i was told these are very short indica plants. Its too many plants for the space, but i am allowing for a male or 2.

Since liming the pots and watering in, and subsequent ph adjusted waterings, the soil ph is now up to 6.9. I will try and let that drop a smidge. The soil ph i assume will fluctuate throughout the grow cycle, but i will try and keep it around 6.5ish.

Again all critique is welcome. Havent really grown in soil sice i was a teen and its been 2 decades or so since a hydro grow for me. When i mixed the soil i didnt ph test it, just winged it. Now i have a cheap soil ph probe, though i have doubts about its accuracy. I also have a ph meter, but only just pulled it of retirement. A eutech wp scan model 1 or 2.... have calibrated it and seems to be working fine

 

[Blew Hiller]

I am confident the leaves were abnormally yellow based on previous experience, and a diluted foliar spray was ok to address the issue. But even at half strength nute they responded a bit more than needed. I understand some will disagree but i dont have photos of them prior to the spray. They looked sickly

If that's true then you will have challenges the entire grow...the plant will rely more and more on the soil and what's in it as it grows.

 

[Anoobis]

Yeah no worries. I am confident there is more than enough nutrient in the soil (maybe misplaced confidence haha). A 3rd of the soil is fresh worm castings from my worm farm, and I've added several amendments to the organic soil mix. Unfortunately i dont have quite the same range as in the states, so i used what i had available. Some bat guano wouldnt go astray... I figured the initial yellowing on the keeper seedlings was from a highly acidic soil and nutrient lock out. One pot showed a 4.5, the 2nd a 5 and the 3rd a 5.5. The older plant had less blood and bone and was about 6, and I chalked the others up to adding extra blood and bone before transplanting and not mixing it thoroughly. I had added Epsom salts for magnesium to the mix but I suspect early on I was over watering and flushed that out.

 

[Anoobis]

As a side note here is something weird. I purchased the Chung Lees from a seed bank. My old seeds were collected while smoking up at university in the late 90's haha. I germinated two Chung's using the paper towel method, then transferred into jiffy pots. The first went without a hitch, the 2nd I snapped the tap root in half. I applied some seasol and it still sprouted but a week later than the first. Both plants had the first seed leaves snap in half for some reason. They just broke off. And the same thing happened when the first single bladed pot leaf emerged. It just snapped in half. While I was waiting the extra week for the snapped taproot plant to live or die, I decided it prudent to plant a 3rd seed. When it germinated, it didn't have the seed leaves and first set of leaves snap in half... It snapped both sets of leaves off entirely back to the stem. By itself, no handling to blame.... It looked like someone had planted a matchstick or a toothpick, no green at all. Instead of chucking it out I placed it under a fluoro bulb for a week till it generated healthy leaves. Never heard of this before. The seeds were just in jiffy pots and plain water was used on all but the one that had a snapped tap root. All 3 had leaves that just dropped off for no apparent reason. Not looking for an explanation, they are all healthy looking now, it was just weird. If you look at the seedling shots you can the snapped bottom leaf