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How To Prevent And Treat Nutrient Lockout In Cannabis

Nutrient lockout (or nutrient lock) is caused by the pH levels when not measuring it properly, by an excessive feeding when you’re giving watering your plants with a higher dose of nutrients, if you don’t take the right care your plants will start to grow slowly, show deficiencies on the leaves and ultimately die.

1. What is nutrient lockout?

Nutrient lockout is when the necessary macro and micronutrients are present in the medium but your plant cannot absorb them because the medium is saturated or because of higher (or lower) pH levels, this it can happen in all types of mediums and your plant will start signs of nutrient deficiency.

This is a very common problem growers encounter when using a new nutrient brand and especially when using synthetic nutrients, a nutrient lockout will inhibit your plant from absorbing the nutrients it needs to develop and it can ultimately kill your plants if you don’t find out what’s wrong with them.

2. What causes nutrient lockout?

Nutrient lock can happen because of two things:

Inappropriate Ph levels

The pH level is what determines which nutrients your plant is able to absorb , that’s why it’s so important to not only check the pH of your nutrient solution but also the pH level of the medium you’re growing in.

The pH level varies depending on the medium you’re growing in and the only way to measure it is with a pH meter, so it’s essential to have one if you want to avoid problems, although you can grow cannabis without one but it will be harder to figure out what’s wrong if you encounter problems along the way.

Nutrient build-up in the medium

Because nutrients are minerals, the excess of nutrients in the medium can increase the pH level in the medium and this can inhibit nutrient absorption.

To avoid this, it’s better to use organic nutrients or really control how much and how often you feed your plants, remember than cannabis plants need a certain amount of nutrients, feeding more or less will result in nutrient deficiency.

3. How to identify nutrient lock and symptoms?

Identifying nutrient lockout can be kinda hard because the symptoms shown will be the same as when overfeeding or when there are nutrient deficiencies , like:

  • Weak plants
  • Stunted growth
  • Yellowing leaves
  • Leaves curling

To make sure your plants are suffering from nutrient lockout and not anything else, you must first check the pH level of the nutrient solution you’re feeding your plants and the medium they’re in.

You need to check both of them because sometimes the nutrient solution has the correct pH but there are nutrients accumulated in the medium, so even if you’re feeding your plants a pH nutrient solution, they won’t be able to absorb them.

There are two ways to do this and how you do it depends on the tools you have available, obviously you will need a pH meter but some of them allow you to check the soil and others don’t so you can check the soil’s pH directly or measure the run-off after watering your plants.

When measuring the run-off, the pH level of the water coming out of the pot is the pH level in the soil so if it comes up too high it means the medium has a nutrient build-up.

4. How to prevent nutrient lockout?

There’s nothing extra to do to prevent nutrient lockout other than growing with caution, with these three tips and keeping an eye for the signs your plans give you you’ll avoid any problems.

Check pH daily

Depending on the medium you’re growing in, you’ll have to check the pH daily or even multiple times a day, in hydro the roots are directly in the nutrient solution so you have to check it a couple of times a day while in soil you’ll be fine by checking the soil and the nutrient solution once a day.

If you need to adjust the pH, you can buy a pH Up or a pH Down solution at your local growshop or even adjust it naturally with lemon juice (decrease the pH) or baking soda (increase pH).

Use organic nutrients

Another good way to prevent it’s using organic nutrients, and unlike synthetic nutrients, organic nutrients make the minerals available in the medium for your plant to absorb them when they need to instead of feeding the roots directly.

If you wanna keep using synthetic ones, make sure you use good quality nutrients and always check the pH and amount of nutrients you provide in every watering, have in mind that in most cases the recommended dosage the manufacturers advise is too high, so if you don’t have a TDS meter you’ll have to decrease the dose manually.

Stages Nutrients
Seedling Water
First half of the Vegetative stage ½ dose of Veg. Nutrients
Second half of the Vegetative stage 1 dose of Veg. Nutrients
Pre-flowering stage ½ Veg. Nutes + ½ Flowering Nutes
First half of the Flowering stage ½ Flowering Nutes
Second half of Flowering Stage 1 dose of Flowering Nutrients
Ripening and Harvest Flushing (water)

You can follow the chart above to make sure you’re not overfeeding your plants, just remember that this is approximate and you should see how your plant develops to increase or decrease the nutrients.

Flush your plants

If you wanna be sure nothing happens, you can always flush between the vegetative and flowering stage although it is not obligatory but will ensure there is no excess to cause nutrient lockout when going from one stage to another.

5. How to treat nutrient lockout?

Depending on the amount of nutrients in the medium, it can take a couple of flushes to completely remove them so you will need to measure the medium until the run-off (or soil) has the correct pH, this is the only way to treat nutrient lockout, if you don’t have a pH meter then you will have to do it until your plant is back to normal.

The best pH level in your case will depend on the nutrients you’re using, your environment and the strains you’re growing but you can use this chart as a guideline.

When doing this it’s a good idea (if you are growing indoors) to decrease the humidity level in your growing space because the humidity can go up and it will stress your plants even more.

The water you’re flushing with needs to be pH’d and the right pH level will depend on the medium you’re growing in.

Medium Ph Level Range Optimal Range
Soil 5.5-7.0 6.0-6.8
Hydro and Soilless 5.5-6.5 5.8-6.0

6. In conclusion

Nutrient lockout can be caused by overfeeding but is really caused by the pH level of your solution and medium, this is a really common problem with new growers so make sure you’re feeding your plants properly.

If you’re dealing with this kind of problem and need advice or want to help us by giving tips, please leave a comment below!

Nutrient lockout inhibits your plant from absorbing the nutrients in the medium and is caused by a nutrient excess, here are some tips to prevent it.

Ph lockout? Soil pH too high?? Need help fast please!

Alter Ego
Active Member

I have 3 plants right now do not look so good. They are showing signs of NPK (mainly N) being locked out due to HIGH pH in the soil. The leaves are yellowing from the bottom on up, from the tips of the leaves, working there way back to the node. BTW, I am growing in organic soil, so I don’t think flushing would help. Just wanted to point that out. The soil mix consist of Lady Bug Vortect Organic potting soil, 1 cup Alfalfa meal, 1 cup Kelp meal, 1 cup Green sand. Thats it, I occasionally feed with a guano tea/molasses tea or foliar. Thats all I have done, nothing else.

PLANT#1 has already lost 4 fan leaves due to N lockout:

The feed water has a constant pH of 5.4-5.5.

The run off tested at 6.9-7.0.

PLANT#2 looks very light overall, but is also showing classic signs of N lockout:

The feed water has a constant pH of 5.4-5.5.

The run off tested at 6.5-6.6.

PLANT#3 is in a mix of FFLW and Earthworm casting with 40% perlite. She is showing the same bullshit yellowing. on the bottom/oldest leaves:

The feed water has a constant pH of 5.4-5.5.

The run off tested at 6.5-6.6.

I am quite frustrated at this point since I have battled this problem with no solution. My current soil is pissing me off and 3 out of 4 plants are dying slowly and dont know what I should do.

I was thinking of getting some pH down and lowering the pH to about 4-4.5 in an attemp to bring my run off down to about 6-6.5. I dunno if thats the best idea or what soooooo someone please help me out.

Nice Ol Bud
Well-Known Member

Dude the pH needs to be 6-7.
Why lower to 4.5? LOL.

Anyways it needs nitrogen dude.
You haven’t been feeding it?

Alter Ego
Active Member

I know what my pH needs to be. I know it needs Nitrogen but I think it is locked out. If I am feeding water with a pH of 5ish and my runoff is coming out at around 7, don’t you think my soil pH is is higher than 7? Thats the problem, my soil is higher than 5 possibly causing a lockout of N?? I am not thinking correctly?

I was thinking of I lower my pH solution for my feed water even lower, I can maybe bring my runoff down from 7 closer to 6 allowing nutrients avaliable to my plants. Hell, what do I know. Hence this thread.

Nice Ol Bud
Well-Known Member

Could be (Zn) def.
Remember to much of one nutrient can show def in other nutrients..
Hope these help.

Nice Ol Bud
Well-Known Member

It doesn’t look like pH at all dude.

Water doesn’t matter..
Whats the ‘Soils PH’?

Alter Ego
Active Member
Nice Ol Bud
Well-Known Member
Alter Ego
Active Member
Nice Ol Bud
Well-Known Member
Alter Ego
Active Member
tranka32
Active Member
Alter Ego
Active Member
dank smoker420
Well-Known Member
Alter Ego
Active Member

Does no one believe in run off test anymore? I have tried 4 different probe testers, all are unaccurate and suck. I am not talking about the cheap walmart crap either.

If my feed water is 5.5 and my run off is 7. it makes perfect sense to me that my soil pH is on the high side. I dont need to know exact #s. all I know it that it is too high and I need to lower it.

racerboy71
bud bootlegger

what kind of soil are you using??

idk what you’re checking water runoff ph for, as i don’t understand what that’s telling me??

and wtf if your ph in the water for @ 5 something?? it should be around 6.5 or 7 if you worry about that sort of thing, which i don’t..

they don”t look bad, they look a bit hungry like everyone else is telling you.. why do you think they looked locked out and just aren’t hungry?? just up the nitrogen a bit and let em rip.. they don’t look too bad imo.
keep an eye on new growth to make sure it comes in nice and lush green..

Alter Ego
Active Member

what kind of soil are you using??

idk what you’re checking water runoff ph for, as i don’t understand what that’s telling me??

and wtf if your ph in the water for @ 5 something?? it should be around 6.5 or 7 if you worry about that sort of thing, which i don’t..

they don”t look bad, they look a bit hungry like everyone else is telling you.. why do you think they looked locked out and just aren’t hungry?? just up the nitrogen a bit and let em rip.. they don’t look too bad imo.
keep an eye on new growth to make sure it comes in nice and lush green..

The soil I am using is Lady Bug Vortect Organic potting soil, 1 cup Alfalfa meal, 1 cup Kelp meal, 1 cup Green sand. Thats it, I feed with a high N Mexican bat guano/molasses tea foliar feed with the same mix. They get fed but dont show improvement. so I don’t understand how they are hungry.

I don’t see how no one understands what the hell I am talking about when it comes to my pH testing process. I don’t know what else to say about that.

reese123
Member
lahadaextranjera
Well-Known Member

I’d be more worried about what ur putting in than what’s running out. at PH 5.5 ur gonna have loads of lockouts. Nutes in soil are absorbed at PH 6.2-7.0.

Just raise the PH to 7.0 in the meantime to help neautralise it and u can add dolomite lime to raise the soils PH. If you’ve been flushing a lot recently then make the next mix 1/4 strength ferts and leave to dry out for a good few days.

Hope this helps.

badmojo420
Well-Known Member
Wetdog
Well-Known Member

The soil I am using is Lady Bug Vortect Organic potting soil, 1 cup Alfalfa meal, 1 cup Kelp meal, 1 cup Green sand. Thats it, I feed with a high N Mexican bat guano/molasses tea foliar feed with the same mix. They get fed but dont show improvement. so I don’t understand how they are hungry.

I don’t see how no one understands what the hell I am talking about when it comes to my pH testing process. I don’t know what else to say about that.

Fine, plenty on N and K, no P to speak of. Kelp and greensand>K, Alfalfa>N. A bit lopsided and I use all three of those, but several ‘other’ things as well.

Your runoff is fine. Quit douching those plants with that 5.5 or whatever you’re dumping on them. That’s just a stoner science fuck up. Reading sites like this, but with no practical experience to back it up.

How long have those *nutes* been cooking? Alfalfa takes a few weeks as does kelp meal. Greensand takes months.

I would suggest getting some Espoma *tone*, your choice. Add some, water with plain old tap water and give it a couple of weeks.

The plants don’t look bad and you’re trying to fix what ain’t broke.

I have 3 plants right now do not look so good. They are showing signs of NPK (mainly N) being locked out due to HIGH pH in the soil. The leaves are…