Calcium Nitrate Foliar Dillution Rate

Simple question. Hoping someone might chime in with some real world experience.


What is a good application rate for calcium nitrate, to be used as a foliar spray on cannabis plants?


As a soil drench, in combination with Jacks, the application rate is apx 1/2 teaspoon per gallon. So I assumed the foliar rate would be similar. Although after a little research, I noticed many people stating the rates at 2-4 tablespoons per gallon. That is 6-24x the strength. The sources I found were using it on tomatoes. Hard to say, without real world experience. Is the 6-24x rate because of tomato vs canna, or soil drench vs foliar, or stand alone vs combined with Jacks.


Thanks for any input. Think I have some test plants, I can sacrifice. Otherwise, I think I will start with the lower rate and observe the change.

Mr^^

Bump
I also would like to know

I have been wondering the same. I prepare my foliar sprays of MgSO4 and/or CalMag to a strength of EC 3.0, and that seems fine.

The recommended dosage for MgSO4/Epsom salt foliar is 1 Tbsp/gal, and that gives around EC 3.0 with my tap water (my well has EC 0.2 or lower). So that what I aimed for with the Cal+Mg spray, too.

Also, if I would use calcium nitrate salt, I would check the pH of the solution before watering or spraying.

Onboard said:

I have been wondering the same. I prepare my foliar sprays of MgSO4 and/or CalMag to a strength of EC 3.0, and that seems fine.

The recommended dosage for MgSO4/Epsom salt foliar is 1 Tbsp/gal, and that gives around EC 3.0 with my tap water (my well has EC 0.2 or lower). So that what I aimed for with the Cal+Mg spray, too.

Also, if I would use calcium nitrate salt, I would check the pH of the solution before watering or spraying.

Click to expand...

Hey, cheers for the answer. I have it bookmarked for future reference
I'm on rainwater and an organic soil mix. From what I've stumbled on here and there I'm possibly more likely to have just a calcium deficiency as the required ratio is about 10:1 cal:mag and mag deficiency is much rarer and often over done, so I'll try just the calcium nitrate first and see if it fixes it.
I bought a 25kg (50lb) bag of calcium nitrate from a farming supplier for $61nzd ($35USD)
Should last me a while

You can see it on these Mindblowers on the lower fan leaves and working it's way up

No worries, @StickyBandit! Hope it works out.

Actually, on my bag of Calcium Nitrate, it says: Watering: 1-3 g/liter Spray: 5 g/liter.

I am very much In the process of figuring out these things myself. I got the MgSO4 spray tips from this podcast: Episode 95: Diagnosing Deficiencies in Cannabis with Brandon Hudson

Basically he reccommends foliar spraying, both as a diagnostic tool and treatment, for Mg as well as Ca deficiencies. If it is a deficiency, you should see a good improvement within 24 hrs after spraying.

Somewhere I also heard that high humidity may also block Ca uptake, meaning there can be Ca in the soil, but if it is too humid, the plant can't absorb it.

In my most resent case, spraying did not make much difference (neither Mg nor Ca).
Instead, the plants became healthier when I upped the fertilizer, and lowered the humidity a bit (from 60-65% to 50-55%RH, at ca 28-30 °C). This was at the onset of flowering.

Calcium Nitrate, Nitrate – Ca(NO3)2
That's very good information @Onboard
I've been doing some mixing and spraying and working out EC and pH and you are pretty much on the money
The recipe for an EC of 3.0 using very pure rainwater that doesn't register on my truncheon to begin with is exactly 2gm/L using scales accurate to 0.01gm. So my $35 bag can make 12,500L
The pH is exactly 7.0 on the Bluelab meter
So I went silly and sprayed everything, I'm so confident in your advice

I only sprayed at 2gm/L
At 5gm/L the concentration will be about 7.0 EC. Seems pretty high. Even the 3gm/L for watering will be at about 4.5 EC won't it? My truncheon only goes to about 3.2 from memory
I will up mine gradually and watch for problems

I was just checking the pH on the canna bio nutes vega and it was 4.5
I added some pH up to take it to pH-6.5 and the EC raised by about 0.2 by the time it was in range. I really have to start checking these things more, although the plants don't seem to mind so much since it's organic but they must assume many people use tap water and well water I guess

My calcium problem may be related to the soil pH being below the desired absorption level for calcium which starts ~pH 6.5 I think?

There are so many things that can go wrong and so many combinations of things. I kinda miss the old days when I used to buy a bag of cheap potting mix and pour on the bottle nutes from start to finish, oblivious of what was wrong, or even if something was wrong

Keep that big bag in a very dry place after opening it. Calcium nitrate absorbs humidity like crazy.

Cheers

Koondense said:

Keep that big bag in a very dry place after opening it. Calcium nitrate absorbs humidity like crazy.

Cheers

Click to expand...

Cheers @Koondense
I put about 20kg into a new 20L paint bucket and sealed the lid. The other 5kg is still in the bag

I use Calcium Chloride as a foliar spray at 1500 ppm. Soil drench too, maybe a 1/4 cup when needed.