Mg, Ca, and Nutrient Lockout Issues..Need Help

I was hoping to get some knowledgeable input about some watering issues I am having. For the majority of my current grow I have been using tap water that has sat out for 2+ days.

After reading the water report here are some useful(average) values:
TDS: 148ppm
Chloride: 23ppm
Calcium: 29ppm
Hardness CaCO3: 75ppm
Magnesium: 1.8ppm

My question is that when I flush my plants with "pure" tap water, I get what sure looks like an Mg, or Ca deficiency. From what I have read 75ppm of hardness is pretty soft, would I benefit from adding Calmag to my non nutrient waterings?

I use Fox Farm nutrients and always pH my nutrient solutions down to roughly 6. The most ppm I have ever given them is around 900. I am positive it isnt nutrient burn, and always pH my water and run off, which is sometimes a bit low but never bad. I feed them every other watering with at least a gallon of water.

Any input would be greatly appreciated.

Is it soil?

Yea sorry..FFoF soil

ph is too low, should be at 6.5-6.8 for ffof. This low of a ph has caused the deficiencies for sure. That ph would work for coir. The soil itself is a buffer for ph. Flush with 6.7 water and check the runoff a few days later to compare. You should google cannabis deficiency chart lockout graph.

FFOF??

You need to add some dolomite or calcitic lime to buffer your pH and take care of the cal/mag problems.

The buffer that FFOF has in it (oyster shell flour IIRC), seems to run out at ~6 weeks or so.

Wet

I have pelletized dolomite lime by Organic Traditions. How much would you recommend per 5 gallon pot of fox farm ocean forest cut with like 25-30% perlite? So based on that next time I think I will start to watch for Mg and Ca def around 5-6 weeks next time. Am I wrong in assuming that 140ppm tap water is pretty decent? I've been thinking about an RO filter but would it really be worth it?

rightcoast said:

I have pelletized dolomite lime by Organic Traditions. How much would you recommend per 5 gallon pot of fox farm ocean forest cut with like 25-30% perlite? So based on that next time I think I will start to watch for Mg and Ca def around 5-6 weeks next time. Am I wrong in assuming that 140ppm tap water is pretty decent? I've been thinking about an RO filter but would it really be worth it?

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I have used that same lime, the trick is to crush 50% as fine as you can get it. Apply a 50/50 mix of the crushed and uncrushed lime at a rate of 2 TBSP/Gallon of soil. This will give you lime now and later. And as for the water.....that's good tap water. I wouldn't get RO in your case because you already have a low pH. If you use RO it will be even lower requiring higher amounts of pH up. BTW, chloride does not evaporate at room temp. like chlorine. So letting it sit won't really help you with that.

2tbl/gallon of mix. Total amount, including the perlite. 5gal container=10tbl of lime.

Most pellets are powdered lime formed into pellets with a fast dissolving binder and don't need to be crushed. Simple way to find out is to put a bit in a glass of water. You should end up with brown water from the dissolved binder and a pile of powdered lime at the bottom of the glass.

Organic Traditions is like this, no need to crush unless you want to. It will release with the first watering or 2.

Wet

i agree with bill wilson. Ph is too low locking out Mg and Ca, make it 6.5. View attachment 1811999

Here is a good question for this thread, I'm sure it will help rightcoast as well...

Once you have the lime mixed in with your 5 gallon container and your growing well for lets say 4 weeks or so, is there a point when you have to add dolomite lime again? If so when would you do this?

Or should you only mix it in when transplanting?

Thanks for everyone's help. I will adjust pH in the future for sure. After reading my water report again I noticed that it only has 1.8 ppm's of magnesium and 29ppm's of calcium. Provided I reach the correct pH levels, would you say I need to supplement Cal-mag? I can't imagine I am getting nutrient lockout due to too much Mg or Ca.

I used 2 tablespoons of dolomite lime per gallon in my new soil mixture. Got a baby Vanilla Kush started straight in a 5 gallon bucket. Any more input would be greatly appreciated as I would much rather not have another issue like I did this time.

rightcoast said:

Thanks for everyone's help. I will adjust pH in the future for sure. After reading my water report again I noticed that it only has 1.8 ppm's of magnesium and 29ppm's of calcium. Provided I reach the correct pH levels, would you say I need to supplement Cal-mag? I can't imagine I am getting nutrient lockout due to too much Mg or Ca.

I used 2 tablespoons of dolomite lime per gallon in my new soil mixture. Got a baby Vanilla Kush started straight in a 5 gallon bucket. Any more input would be greatly appreciated as I would much rather not have another issue like I did this time.

Click to expand...

If you added the dolo, no need for the cal/mag. The tap water and dolo should be sufficient.

You MAY need a little shot of Mag early on as the dolo seems to release the mag slower than the Ca. When needed, one application was sufficient till the lime broke down further.

Wet

p4stlife said:

Here is a good question for this thread, I'm sure it will help rightcoast as well...

Once you have the lime mixed in with your 5 gallon container and your growing well for lets say 4 weeks or so, is there a point when you have to add dolomite lime again? If so when would you do this?

Or should you only mix it in when transplanting?

Click to expand...

Not at 4 weeks. I've had to top dress long term heavy feeders after ~4 months or so. But, none of this was mj.

Wet