Leaves are turning yellow...

[dilvish]

again recalibrate the PH tester to make sure you are getting an accurate reading. Calcium in coir the PH needs to be at least 6.2 otherwise it won't get absorbed. Other than that watering plain PH'd water for the soil is fine for the first 3-4 weeks. that type of soil should contain enough nutrients to last that long. Beyond that you should start feeding.

Also, is there any reason you would leave out so much soil/coir? the pots look almost half empty.

Fabric pots have great drainage but don't believe that they can't be overwatered or underwatered. Make sure the pots are not sitting in water as fabric pots reabsorb anything leftover underneath unless the have some airflow under them. 40 oz of water may seem like enough but each watering should give about 20% runoff so don't be afraid to give them more, just make sure they dry out enough before the next. Coir dries out faster than soil so be aware of that. lower temps means the soil takes longer to dry out.

[GrumpyOldMan]

On a TOTALLY different topic, I read in a post recently (don't remember who...) where someone heard a rumor about Fox Farm creating a cannabis only line, so I asked them, here's what they said;

Thank you for contacting FoxFarm, I’m happy to help!

The majority of FoxFarm products can be used for cannabis as well as other plants. Our first option to grow your cannabis to its fullest potential is our original Soil Trio products; Big Bloom, Grow Big and Tiger Bloom. Big Bloom is a gentle micronutrient liquid that helps young plants increase nutrient cycling and new root health. You can then begin to incorporate Grow Big. This liquid concentrate boosts lush vegetative growth. Finally you can bring in Tiger Bloom to help your plants create multiple buds and flowers for big harvests. With this feeding program you have more options to use additives, seen in orange and purple.

If you have any other questions please do not hesitate to contact us. To learn more about our company, new products, and download our latest feeding schedules please visit www.FoxFarm.com.

Caelidh
Product Support Specialist
FoxFarm Soil & Fertilizer Company
(707)443-4369 office
(707)443-7645 fax
POST OFFICE BOX 787 • ARCATA, CA 95518

just what I found...

[dilvish]

was there a point to that? FF has all kinds of "hot" soils. they also have a nutrient line as mentioned in the response. I doubt they would specifically earmark "cannabis only" on any of their products for fear of reprisal...some people would stop buying their products if they saw FF was catering to "stoners". It's a slippery slope and I can assure you they won't fall down it. Coir would be a better choice anyway...it's easier to manage, reusable and tends to reduce or eliminate pests.

[Ckbrew]

GOM, The calibration solution can be mixed and stored, it will keep, it is a buffer solution. I only change it once a year and I think that is over cautious. Make sure you rinse your pen between solution calibrations and readings in distilled water preferably. Mix your calibration solution with distilled water. There are 3 calibration solutions. One at 6.86 one at 4.00, and one at 9.18- for the Vivosun pen. Other pens may use different solutions. You only need to use the calibration solutions in the acid and base range if you want a Ph reading accurate to two decimal places. For one decimal I just use the 6.86 calibration solution. Ph papers or drops are always a good back up and as a spot check. In the coco I shoot for Ph 6. I also let it drift 5.8 to 6.2 in small increments. I do this to cover the spectrum. Some people agree with this practice, and some do not. Your decision. Some people check the run off Ph. I do not unless I see a big problem, which I have not seen yet. In coco if I want to adjust Ph in coco I just over water it a bit and collect and dispose of the run off. I think 6.5 would cover it in soil, but I will defer to a soil grower. A $1.00 says your pen is off and causing your problems. Been there done that.

[Jebidiah]

I just got a vivosun pen and within a week of being paranoid and checking it against my old halfway working pen and a manual test kit it has rose 0.4 out of calibration.

[GrumpyOldMan]

CKBrew, Thanks for the info about the calibration solution, I'll be keeping that on hand. I still have some of the calibration powder that was supplied with the pen.
I use distilled water in a spray bottle to rinse the pen between readings, so I have distilled water, and I'll go ahead and get the test strips as a backup.
Also, you answered a question I had about Phosphorus uptake and the low PH it needs... I was wondering how to get the food to the right PH for that without causing uptake problems with Cal-Mag uptake, I'll just alternate the ph somewhere between the 5.8 to 6.2 during the feedings?
As far as runoff PH, what should I want it to be? Just for reference...

Thanks again,
GrumpyOldMan

[Ckbrew]

This may be semantics but I would not "alternate" between 5.8 to 6.2, I would call it letting it change slightly between feedings with in that range. I try to keep the change like 5.9 to 6.0 for a change, not 5.8 directly to 6.2. As for run off it is more of a looking to see what is there and what direction you need to go. Once you find your groove you will not need to check run off.

[Ckbrew]

After thought on the pen. If you have a stable water supply (I have a drilled well) the Ph of the water will not change at least mine doesn't. Do a quick check on the tap water. If you know what it should be and your pen says different, calibration is needed.

[Gingerbeard]

Yep. If tap water doesn't convince me, I check coffee.

[GrumpyOldMan]

Ckbrew, Yeah I meant that I would just kinda let the PH wander, but keep it between those ranges, and not being so strict that it HAS TO BE 6.0., every time, I guess I should have said it differently, I can see where you got that idea, sorry.

As far as the pen, I've got county water, and they're pretty good, but not great, about keeping the PH about 7, but I've never gotten the same reading more than 2 days in a row, and that's with a freshly calibrated meter...
But I'm taking your advice and making up a bottle of the calibration solution and check it every time I use it.
And I'll probably get test strips anyway, I'm old school, and I'm partial to a chemical test strip than some newfangled eelectronic deevice...

And Gingerbeard... I wonder what the PH of my coffee would be?! interesting thought...

Thanks again
GrumpyOldMan

[bboyfromwayback]

I grew in FFOF or Coco Loco for over 12yrs and started feeding using FF’s schedule at 1/2 strength from day 1 above dirt. Ph 6.3-6.4 on feed days, 6.6-6.7 on plain water days no issues.

Ive recently grown a few plants in coco and 5.9-6.3 seems to be the zone there. I started off feeding every other watering and started to see yellowing so I switched to feeding every watering and plants were much happier.

IMO marijuana likes to be fed more often than not, only in small amounts. It prefers to micro dose 😂