Yellow and dried out leaves

[Raja Ram]

Hi, I have this problem with a grow of G13 x Hashplant x Bubblegum, and have also had it before on other plants but never really figured out the problem. The problem starts with yellow and brown spots on the leaves which then expand and finally the whole leaf is yellow and so dried out that it crumbles if touched. The problem is foremost found on larger fanleaves, but also to some extent on smaller leaves. The plants still grow good, the buds are fattening and the trichome layer builds up nicely - still I know they could perform better if everything was ok.

Here is a picture of the problem in its full extent, you can also see beginning problems on the leaves in the background. Any help is appreciated!

 

[Blackvelvet]

Copy these questions into a reply. More info needed.


Hydroponic or soil?
If soil, what is the composition?
From seed or clone?
Age of plant in question?
What stage (Veg/Flower; how many days into)?
Medium (Soil, Rockwool, Hydroton etc.)?
Container/Pot size?
Have they been transplanted, if so how long ago?
If soil, composition ratios (peat moss, perilite, vermiculite etc.)?
Water runoff Ph?
Nutrients added? Be specific as possible.
Ratios of nutrients (N% P% K%)?
Feeding schedule?
When were they last fed/watered?
How are you determining when to feed/water (weight, wilting, etc.)?
TDS/EC/PPM?
Tap/RO/Distilled water?
Ph before and after adding nutrients?
Is your Ph equipment properly calibrated?
Light intensity/Age of bulb/Wattage?
Distance to the canopy?
Temps at canopy?
Temps at root zone or reservoir?
Day/Night temps (Min.-Max.)?
Current air flow (CFM)?
Is there air blowing directly onto plant?
Using CO2?
Relative humidity?
Growing technique (Scrog, Sog, Supercropping etc.)?
Has plant recently been pruned, clones taken, fimmed or pinched?
Pests?
Chemicals used to irradicate?
If so,When?

 

[Raja Ram]

Thanks for showing interest in helping me out, I'll try to answer as many of the questons as possible.

Hydroponic or soil? - Soil

If soil, what is the composition? - According to the bag it's a mixture of peat, lime, manure and sand.

From seed or clone? - Seed

Age of plant in question? - 2 months, give or take

What stage (Veg/Flower; how many days into)? - Flower, around day 35
Medium (Soil, Rockwool, Hydroton etc.)? - Soil

Container/Pot size? - 15 liter

Have they been transplanted, if so how long ago? - Yes, they were transplanted about four weeks ago


Nutrients added? Be specific as possible. - HESI Bloom Complex

Ratios of nutrients (N% P% K%)? NPK 4-3-5

Feeding schedule? - 1 ml/l every watering

When were they last fed/watered? - Yesterday

How are you determining when to feed/water (weight, wilting, etc.)? - Weight of the pot and by sticking a finger into the soil

Tap/RO/Distilled water? - Tap water

Light intensity/Age of bulb/Wattage? - 400W HPS, only used for one grow

Distance to the canopy? - Around 15"

Temps at canopy? - ~35 degrees celsius

Temps at root zone or reservoir? - 25 degrees celsius

Day/Night temps (Min.-Max.)? - 20-25 at night and 25-30 at day, celsius

Is there air blowing directly onto plant? - Yes, an oscillating fan

Relative humidity? - 35-40%

Growing technique (Scrog, Sog, Supercropping etc.)? - Just letting them grow

Has plant recently been pruned, clones taken, fimmed or pinched? - Some of the lower branches have been removed

Pests? - No

 

[Raja Ram]

Perhaps I might add that the problem is mainly in the middle parts of the plants, not the tops, so I guess we can exclude heat related problems.

 

[Guest]

saddly mine do the same thing and I cant figure out why!

 

[Blackvelvet]

Feeding too weak

Feeding too weak

Your feeding too weak. at least double what your using to 2ml per liter. Better 2.5 ml per liter. You can apply this with every watering but make sure you get alot of runoff out the bottom of the container everytime.

Ph is important. You need to keep track of it.

How to test ph: After watering and ferting well till runoff, wait 30 minutes. Apply a small amount of distilled water to the top till 1 ounce (30 ml) of runoff occurs. Catch this on a saucer. Test ph. If after watering and waiting 30 minutes you can tilt the pot and get some liquid out, you can test that instead. Ph 6 is a good number to aim for.

 

[delta9thc06]

35 degrees celsius is around 95 degrees fahrenheit, thats really hot mate. I dont think ur problem isnt with feeding right now but more so heat. It looks like heat stress so what i would recommend doing is getting really good air flow and try to get it around 80's. Whats ur current ventialtion system?

Also heres a link to the thread that has everything that could go wrong with ur plant, heat stress is under post #7 http://www.icmag.com/ic/showthread.php?t=11688

 

[Blackvelvet]

Here is what he's feeding his plant (approximate ppm's):

n 40
p 13
k 41

Just as a reference, I give seedlings their first feed at 75 ppm nitrogen. He's way underfeeding. The burn is probably potassium deficiency.

Heat stress would show up at the top of the plant closest to the bulb.

 

[delta9thc06]

If the plants getting burned by potassium then that means he would be giving it too much potassium, and the fan leaves that have the most surface area would be getting the most heat and show stress first. Ive had heat stress on my plants and it looks just like that. Blackvelvet do u think that 95 degrees fahrenheit is good growing weather?

 

[Blackvelvet]

Let's do this. Cool the plants more and increase ferts. No need to argue.

 

[delta9thc06]

Fair enough, just start increasing the nutes slowly dont want to give it full strength right away. Also watch for any other variations in the leafs.

 

[Raja Ram]

Your feeding too weak. at least double what your using to 2ml per liter. Better 2.5 ml per liter. You can apply this with every watering but make sure you get alot of runoff out the bottom of the container everytime.

Ph is important. You need to keep track of it.

How to test ph: After watering and ferting well till runoff, wait 30 minutes. Apply a small amount of distilled water to the top till 1 ounce (30 ml) of runoff occurs. Catch this on a saucer. Test ph. If after watering and waiting 30 minutes you can tilt the pot and get some liquid out, you can test that instead. Ph 6 is a good number to aim for.

When the problems started I tried both to go higher on the nutes (from the beginning i actually gave them 2ml/l every watering, which I increased to full dose) and later flushing and lowering the dose when i noticed it didn't help. I don't think I will be using more nutes in general, cause when I upped the dose they also started to show signs of too much nitrogen. I forgot to say that apart from the Bloom Complex I've also added a very light dose of PK 13-14 a few days ago, and I will supply the plants with an increased dose every week until harvest.

I have grown for 6 years and don't need general tips on growing, I need specifics on the lack or overuse of some specific nutrient - what it is that actually cause this problem. My own theory is that the problem is pH related, since I don't have a pH meter (and can't afford one) it's very hard to verify though. Perhaps someone can identify these problems as too high/low pH?


delta9thc06: I don't think that's very hot when measuring straight under the HPS light, this is not the air temperature, it's the temperature when considering heat being transferred from the bulb to the thermometer as well.

Most other plants I've been growing through the years have grown really well with lush dark green leaves all the way, I also have an Oasis in the same grow room right now that doesn't show this problem. If it's heat related it would be a general problem, not strain specific. Right?

 

[Blackvelvet]

I need specifics on the lack or overuse of some specific nutrient - what it is that actually cause this problem.

Start with only using 41 ppm potassium. Lack of potassium will cause a burn on lower leaves when deficient.

If you saw too much nitrogen before, maybe that was due to having manure in your potting mix. It may be depleted by now since you repotted 4 weeks ago.

If you want more specifics about your fertilizer plan you will need to provide more details. How much pk 13/14 are you adding? What is the % of the elements in your ferts like calcium, magnesium, iron, zinc, manganese, copper, boron, and molybdenum. Without this info, I can't tell you more.

 

[Raja Ram]

Thanks for not giving up on me.

I added 0.25ml/l of PK 13-14, which is what the label on the bottle is recommending in the 4th week of flowering, although that dose is for hydro culture.

Here's the info I can find on the soil bag about nutrient contents, all values are measured in grams per cubic meter, which would be milligrams per liter if I'm not mistaken. This is how much they added to the soil mixture, I don't think the nutrients from the manure in the mixture is accounted for in these values.

N: 140
P: 70
K: 150
Mg: 260
S: 80
Ca: 2200
Fe: 1,2
Mn: 2,1
B: 0,4
Cu: 1,6
Zn: 0,5
Mo: 2,6

 

[Blackvelvet]

Thanks for not giving up on me.

We're not giving up. It's free buds were talking about.

Numbers are in parts per million (ppm) = mg fert per liter

.25 ml pk 13/14 per liter adds:

p 16
k 34

1 ml per liter regular fert:

n 40
p 19
k 41

Total:

n 40
p 35
k 75

This is very, very weak. So weak you could pour it on a newly hatched seedling.

First step to fixing this is raise your nitrogen to 100. So you would use 2.5 ml regular fert per liter (2.5 x 40=100) Gives you this:

n 100
p 48
k 103

Add the .25 ml pk 13/14 per liter also. Total:

n 100
p 67
k 137

This should be plenty of phosphorus. nitrogen at 100 will keep leaves from yellowing and falling off but yet not really strong enough to encourage leafy growth.

As far as the soil having nutes already, they were probably sprayed on to it. They are long gone. This is called a starter charge. I not sure what exactly to make of the numbers you came up with but your calcium level compared to magnesium level is bad. Too much calcium. k, ca, and mg compete to get in the plant. Excess calcium can bring on a magnesium or potassium deficiency or both. In the future, find a soil mix with dolomite lime. This would be a more balanced cal mag ratio.

I am not sure what is in the bloom complex as far as calcium and magnesium. Lime in your soil mix is beginning to wear out probably after 4 weeks with repeated watering. Hopefully the fert contains calcium and magnesium since your increasing potassium. All about keeping a balance.

Ph control is very important. If you can not get a meter, go to a brew your own beer/wine store or the aquarium section of a petstore and get some ph test strips. Only a couple of $. Range 4-7 is ok. Not only can you use it to test the runoff, you can adjust the ph of your fert water after mixing everything in. Ph 6 would be about right.

When you apply the fert water, make sure you get alot of runoff everytime. This will prevent salt buildup. You will probably not need to leach with plain water until the end.

Good luck!

 

[Raja Ram]

Thanks a lot dude, I have learned a few things in this thread. I'll try that nutrient schedule for a while and we'll see how the plants react. The bloom complex does indeed contain calcium and magnesium, doesn't say in what quantities though.