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Yellowing leaves, soil, nutrient question

ColonelBlake

Well-Known Member
Hello All.

This is my first grow. I'm currently growing in a well ventilated greenhouse in Michigan ( legal 12 plant grow ). My plants are currently 6-7' tall. The specifics of my grow are at the bottom.

I've been experiencing lower to mid leaf yellowing issues for at least a month now. It started out looking like a Nitrogen deficiency, but now it looks like a potassium deficiency ( since they are flowering ). I'm pretty sure it's a mobile macro nutrient deficiency as @Emilya noted in another thread ( https://www.420magazine.com/community/threads/noob-with-possible-ph-issues-soil.470048 ).

I've been giving my plants some nutrients. Not allot by any stretch. So I'm wondering if I need to kick it up a notch ( esp given the size of the plants ). I've been pretty cautious this entire grow - nutrient and watering wise. Mainly because of what I've read on this forum ( i.e. water when dry, and don't overfeed ).

I started out doing a feed, water, feed, water, etc schedule. I've since moved to a feed (100%), partial feed (50%), full, partial, etc. I started doing this recently - a little over a week now., but I haven't noticed much progress yellowing wise. It's the same or possibly getting worse. I'd guess that each plant has 2-3 dozen yellowing leaves atm. Several leaves fall off every plant daily ( completely shriveled up and brown ). That said, the top 2/3 of the plant looks good and seems to have allot of vigor.

I'm currently using General Hydroponics Trio for nutrients. I bought a gallon of each so I'd like to use them up unless it truly a problem.

Current nutrient feed:
Full feed ( early flowering ): 4ml/gal micro, 1ml/gal grow, and 5ml/gal bloom. ~450ppm ( more if I add calmag - or use more well water ).
Partial feed: 50% of a full feed. ~225 ppm.
This is done using the full feed, partial feed, full, partial schedule as noted above ( every 2.5 days or so ).

A few other tidbits:
*Plants have been in the present container for ~3 months ( 20/gal fabric pot ).
* I really don't think this is a watering issue. I've been pretty good ( not perfect ) about not watering until the soil gets pretty dry - not completely dry though.
* Plants were put on pot elevators recently.
* I use straw for mulch. I sprinkle DE on the straw ever week or less.
* Plants get 6 hours of light.
* I've done a dozen soil ph samples and the ph is usually right around 7.0 ( +/- .2 ). I use a slurry test to determine the ph.


Grow medium: Soil ( made myself - 40% compost, 30% sphagnum peat moss, 30% perlite ). Mixed by hand..
Container: 20 gallon fabric pots.
Grow area: 8x20' greenhouse. 8' ceiling.
Water: 80-90% RO, remaining is well water.
Water frequency: Every 2.5 days currently. ~3 gallons of water per plant each watering.
Plants: 6 gorilla glue, 6 purple chem ( started as clones ).
State: Early flowering.
Planted: Early May ( 3.5 months old ).
PH: Soil ph is 7-8. Water ph: 6.2-6.3. .
Nutes: GH Trio.

Thank you for reading my post, and thanks in advance for any advice!
 

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Emilya

Member of the Month: Mar 2019 - Grow Journal of the Month: Jan 2020, Aug 2021
towards the argument for upping the nutes let me suggest the following, knowing that most nute directions are based on an indoor grow with a 1000w HPS:
  1. you are using the sun, so your lighting is more intense than an indoor grow, so the plants are more active
  2. your plants are huge and could easily handle more of a boost
  3. your diagnosis is correct, mobile macro nutrient deficiency moving up from the bottom... always indicates starvation
 

ColonelBlake

Well-Known Member
towards the argument for upping the nutes let me suggest the following, knowing that most nute directions are based on an indoor grow with a 1000w HPS:
  1. you are using the sun, so your lighting is more intense than an indoor grow, so the plants are more active
  2. your plants are huge and could easily handle more of a boost
  3. your diagnosis is correct, mobile macro nutrient deficiency moving up from the bottom... always indicates starvation
Thank you Emilya!

Should I slowly increase the dose and keep an eye out for nutrient burn? If so, would I look at the new growth to see if they have tip burn? Sorry for the stupid questions, I'm pretty new at this :) Thank you in advance!
 

Emilya

Member of the Month: Mar 2019 - Grow Journal of the Month: Jan 2020, Aug 2021
Thank you Emilya!

Should I slowly increase the dose and keep an eye out for nutrient burn? If so, would I look at the new growth to see if they have tip burn? Sorry for the stupid questions, I'm pretty new at this :) Thank you in advance!
Yes on both... again knowing that a little tip burn is not a crisis and lets you know you are just a little bit hot. I would go up about 25% and see if green starts coming back to some of the leaves that are starting to go yellow.
 
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