Growing in peat moss - pH dropping heavily.

[dr.bomkfist]

I would like to ask other growers about problems with pH when growing in soilless mix (peat moss + perlite).

I'm growing in Biobizz Lightmix and Canna terra.

I've noticed that pH drops in a few weeks and I have to flush it with high pH water to avoid burning plants by too acidic medium. Is it normal?Do you have same issue with peatmoss medium?

What's the right way to maintain healthy plants in soilless?

Should I treat soilless like soil or there are some differences?

Proper pH is supposed to be 5.8-6.2, but my plants aren't happy below 6.5.
I've never had any problems in soil, only in soilless.

I would be very greatful for advices how to keep my plants healthy to the end. This soilless gives me a headache, I have issues for 2 months now. I'll never grow in peat moss mix ever again.

 

[lobsterbush]

adding lime to the mix helps to stabalize the ph. as well as adding calcium to the mix

 

[dr.bomkfist]

adding lime to the mix helps to stabalize the ph. as well as adding calcium to the mix

I forgot to say, I add 1 tablespoon/gallon of lime. Do you grow in soilless?

 

[lobsterbush]

yeah. I don't measure but I use a small handfull per 3/gal. In the past if a plant was showing ph problems I have also topdressed with some powdered lime, then small amount of mix or ewc and then water in. Takes a week or so to really balance out but it will.

 

[dr.bomkfist]

yeah. I don't measure but I use a small handfull per 3/gal. In the past if a plant was showing ph problems I have also topdressed with some powdered lime, then small amount of mix or ewc and then water in. Takes a week or so to really balance out but it will.

Thanks. Do you check your runoff pH?

 

[lobsterbush]

only if needed. I grow organic and lately everything has been keeping itself in check. good luck

 

[dr.bomkfist]

thank you

 

[guest 77721]

Hi dr.bomkfist

peatmoss is naturally low pH but also so is liquid fertilizers. Most peatmoss based potting soils have some dolomite lime added and adding 1 - 2 tablespoons extra per gallon of soil will help.

The pH ranges for soil and soil-less is actually 6.5 - 7.0 with 6.8 as the optimum. I have had problems myself when the pH drops below 6.5. This dropping of the pH is from adding too much nutes and having them accumulate in the soil throughout the grow.

It sounds like you're on top of things by monitoring and flushing but really your nute levels are too high.

There is a difference between Hydro which runs higher concentrations with lower pH and the pH will rise as nutes are consumed. In soil the nutes are more available at lower concentrations and will accumulate over time driving the pH down.

 

[dr.bomkfist]

Hi dr.bomkfist

peatmoss is naturally low pH but also so is liquid fertilizers. Most peatmoss based potting soils have some dolomite lime added and adding 1 - 2 tablespoons extra per gallon of soil will help.

The pH ranges for soil and soil-less is actually 6.5 - 7.0 with 6.8 as the optimum. I have had problems myself when the pH drops below 6.5. This dropping of the pH is from adding too much nutes and having them accumulate in the soil throughout the grow.

It sounds like you're on top of things by monitoring and flushing but really your nute levels are too high.

There is a difference between Hydro which runs higher concentrations with lower pH and the pH will rise as nutes are consumed. In soil the nutes are more available at lower concentrations and will accumulate over time driving the pH down.

Thank you . I've noticed that plants feel alot better when I flush most of salts out with high ph water. This soilless mix has pH = 5 and has too much nutrients (ec=2). It's strange that mix which is supposed to be designed for cannabis plants is such a crap.

I hope that I will finish this grow without losing much yield and I'll go back to real soil.

 

[guest 77721]

I've helped out lot's of growers with pH problems over the years. Pre-fertilized soil can be too hot for seedlings and young plants to begin with. Knowing your water is important too. If you have a water softener, you'll have lots of pH and over feeding problems because of the dissolved salts in the water. Mg and Ca are replaced with Sodium Na.

I've had great success with Promix soilless which is peat moss, perlite and some dolomite lime. My soil mix is 2 parts Promix to 1 Part Vermiculite to 1 part Perlite and Dolomite Lime at 1-2 tbsp/gal.

The other thing I found out is that all the liquid fertilizers do not add Mg or Ca because these minerals are normally in most tapwater and high concentrations are called hard water. When your plant is growing hard in veg, it needs lots of Ca and Mg. These deficiencies can trick you into adding extra NPK fertilizer which just lowers the pH and locks out Mg/Ca from the plant.

Dolomite Lime is a 50/50 blend of Magnesium Carbonate MgCO3 and Calcium Carbonate CaCO3. The carbonate ion will react with H+ ions to form water and will reduce the acidity of the soil. I don't know what you're adding to lower the pH but it may cause complications as well.

 

[dr.bomkfist]

Hi. Take a look at this pic. All plants (10) have the same symptoms. Yellowing leaves with necrotic patches, curling and falling off. NPK fertilizer makes it even worse. Flushing with high pH water helps a little bit, but leaves are yellowing anyway. I added 1tblsp/gallon of mix. Seems that it doesn't make plants happy. My lime is 2/3 Ca 1/3 Mg.



Strange thing is that when I put plants into fresh mix (pH=5.5!) they're perfectly healthy for 3-4weeks. Only after this period everything goes wrong. EC is still high so it shouldn't be NPK problem.

Thank you for any help, maybe this problem will be easier for you than for me, I'm struggling with it for months.

More pics of sick plants are in my album.