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Soil pH problems & P-deficiency: phosphorus

TroyMcclure

Member
Hey,

I got 2 Crop King Seeds Fem White Widows growing under 4 Spider Farmer SF1000's (220 total watts drawn - 2x @ 70 watts + 2x @40 watts)

End of week 10 total, week 1 of flower

climate: 67 night time temp - 77 (81) max daytime temp + rh 40-60%

soil: 5 gallon pot with 3 gallons of fox farm ocean forest and 1 gallon of pro-mix
nutes: fox farm big bloom, grow big, tiger bloom
watering: 2-3 gallon per week + run-off of 15% every other watering (ph. 6.35-6.45)
feeding: every watering starting from week 7
- usually around 10ml per gallon or less of grow big and big bloom
- first feed of flowering was 10ml / gal big bloom, + 5 ml/ gal of both grow big and tiger bloom
run-off: 15% every other watering, plant 1: 5-6 ph & plant 2: 4-5


old minor issues: Red stems on some growth, some light green throughout grow on new growth, some twisted dark growth

current persisting issues: red stems on some growth, some yellowing, bronzing, browning on fan leaves, usually older leaves, and in random places.


So overall the plants seem really healthy, however, there has been red stems since week 6 and discolouration in leaves. The soil pH fluctuates from the low 6's after a feed/water and finishes in the high 7's by the time it is dry and ready for another water/feed.

I believe the ph swings are causing the problems, notably with some boron, nitrogen, phosphorus deficiencies along the way.

I currently believe that the phosphorus deficiency is still lingering.

Mistakes made:
- under watered and under-fed to ensure I err'd on the side of caution
- ankle surgery and holidays made consistent feeding and check ups a little delayed, so maybe 2 timesI was late to feed

Currently, leaf discolouration has declined a fair bit but still persists, but the biggest issue I am having, is the pH going from low 6's to high 7's

Why is this happening and what can I do to prevent it. Both plants treated 100% same?

picture context:
plant 2 =back left
plant 1 = front right

most discolouration pictures are old and have been pruned, but all the same issues look to be slowly coming back and each plant has around 20 fan leaves currently being affect, in 1 week or so they will look like this again. I will post new pictures when lights come on today.
 

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bobrown14

Grow Journal of the Month: Dec 2017 - Photo of the Month: May 2020
Looks good to me. swings in soil pH are normal. Thats how the soil microbes and roots of plants communicate.

How are you testing your soil pH? Likely not very accurate thats a test best done in a LAB under laboratory conditions. pH is a measurement that is logarithmic, so any deviation in testing can be quite a bit of a swing. As long as your test results are below 8 and above 5 your probably going to be ok with that. pH swings are normal.

Also plants loosing leaves (turning yellow) at the onselt of flowering is also normal.

Look up Leaf Senescence. This is something plants do for lots of reasons all thru the life cycle of the plant. The leaves have their own life cycle as well and why you should see the older large fans turn yellow and FALL off earliest in flower.

Brown spots on your leaves - inter-veining (in between veins) is a sign of some deficiency.

Since you're doing chemical fertilizers I can not help you. What I do with organic soil growing and getting those conditions I make a ACT (aerated compost tea) and give the plants kelp tea in addition.

I just went thru this and fixed the problem in about a week with the above treatment.

The tops that are lighter colored are OK - thats normal for a plant thats about to go into flowering.

Red stems is genetic. Dont worry about that. Its actually preferable. Whomever lent you any advice otherwise in that regard is on the wrong track. I think red stems can be invoked by light that has red spectrum in it - most all modern lamps have red spectrum.


On pruning - btm 1/3 of the plant get rid if that BEFORE flowering light. You can prune now but go easy. Dont want to stress plants going into flower.

Leaves that have those "bronzing" inter-veinal discoloration. Thats permanent. It wont go away even tho you "fixed" the problem. So dont look to previous leaf problems to fix themselves they will not. Slight yellowing yes, anything else no.

Dont under water and be sure your water/feed nutrients are pH'd to what the manufacturer suggests. Water more frequently in flower to run off 15% is good. Just do it more often say up it 1 more time a week.

Get a fan under the netting and point it toward the soil if you dont have that already.

Air flow is important - look up Plant Transpiration.

So 2 words to work on homework.

Transpiration
Leaf Senescence

These are very important for healthy plant growth and more importantly flowers.

Your plants look great. A few discolored leaves is not a problem.
 

TroyMcclure

Member
Looks good to me. swings in soil pH are normal. Thats how the soil microbes and roots of plants communicate.

How are you testing your soil pH? Likely not very accurate thats a test best done in a LAB under laboratory conditions. pH is a measurement that is logarithmic, so any deviation in testing can be quite a bit of a swing. As long as your test results are below 8 and above 5 your probably going to be ok with that. pH swings are normal.

RESPONSE: I agree
  • long runner soil meter (Soil Moisture/pH/Light Tester)


Also plants loosing leaves (turning yellow) at the onselt of flowering is also normal.

RESPONSE:
- only 5 days into flowering, most of the pictures showing deficiency were from week 8-9 of veg.

Red stems is genetic. Dont worry about that. Its actually preferable. Whomever lent you any advice otherwise in that regard is on the wrong track. I think red stems can be invoked by light that has red spectrum in it - most all modern lamps have red spectrum.

RESPONSE:
- I agree it can be genetic, but it also can be caused, from my homework, by too low temps ( i doubt an issue) and low phosphorus, which seems to explain both the stems, (which I am not worried about) and the discolouration.
- (How to fix Cannabis Phosphorus Deficiency (P) Pics & Symptoms)

On pruning - btm 1/3 of the plant get rid if that BEFORE flowering light. You can prune now but go easy. Dont want to stress plants going into flower.

RESPONE:
I took off 1/3 of the fan leaves, especially afflicted ones days before flowering. I am now waiting until day 21 (recommended day to prune during flowering via homework) for the stretch to finish and then I will trim below the screen, also considering lollipoping. I will gladly be taking any and all recomendations / opinions on these techniques and timing.

Leaves that have those "bronzing" inter-veinal discoloration. Thats permanent. It wont go away even tho you "fixed" the problem. So dont look to previous leaf problems to fix themselves they will not. Slight yellowing yes, anything else no.

RESPONSE:
agreed

Dont under water and be sure your water/feed nutrients are pH'd to what the manufacturer suggests. Water more frequently in flower to run off 15% is good. Just do it more often say up it 1 more time a week.

RESPONSE:
- I aim for 2 waterings, 1 light watering, 1 gal each, with the normal to half the normal amount of nutrients
- then the second watering a full 2 gallons each, 15% run-off (1.5L each) with normal nutrients (starting slow with the tiger bloom nutrients)

Get a fan under the netting and point it toward the soil if you dont have that already.

RESPONSE:
- dehumidifier fan blowing + intake ducting blowing + 2 6" mini fans blowing (2 pointing at each plant, 3 below, 1 above)

Air flow is important - look up Plant Transpiration.

So 2 words to work on homework.

Transpiration
Leaf Senescence

These are very important for healthy plant growth and more importantly flowers.

Your plants look great. A few discolored leaves is not a problem.


Thank you for the very thoughtful response I realllllly appreciate the effort and consideration, tips and all included in it. It seems we are 100% on the same page and we agree with the main issues. the plant has always handled the pruning, topping, and feeding like a champ. I would normally feed ever other watering but they love it so much, and show deficiencies, likely I was making up the debt. I think all is well and on track, now that bloom nutes are coming in I hope to solve the older issues of P deficiency or whatever it is. Not worried but trying to be super prepared. ;)
 

bobrown14

Grow Journal of the Month: Dec 2017 - Photo of the Month: May 2020
Easy to over think and as a result over react. Plants take some time several days actually for you to be able to actually visually see results of what you do.

Lots of new growers change too many variables in too short a period of time resulting in well not very good results.

Topping is something I don't do unless the plants are VERY young say 3-4th node in early VEG. Even then I'm very hesitant to do that as it affects yields negatively in the long run. Don't care what anyone says. It's about bio-mass for yields smaller plants smaller yields and topping will result in a smaller plant. Unless you wanna VEG for 3-4 months. Even then without topping I'll be in harvest mode and topped plants just starting flower.
 
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