Hi all!
Im looking around the site for some dosages in grams of Magnesium Sulphate for soil drench and foliar spray…lots of info but im getting a little headache figuring out.
Im experimenting with Megacrop at 4 g x gallon and some of them they are still pretty pale…
Im using Distilled water from dehums and AC, plus with strong LED, im thinking a Mg supplement is due…
Thanks a lot!!
Hi @Grapefruitroop,
My initial thought is related to using the dehumidifier and AC water…
I’ve heard rumors that it may contain metals from the condenser, but those are just rumors…
I have no idea if there is any truth to them.
A bigger problem is that there are likely to be very little minerals in the water, ie, calcium, etc., so it would be like using RO water to mix your nutes.
For MY water (RO) I found that adding 2ml/gal each of silica and calmag first helps to restore those minerals and stabilize the pH. Then add in your MC or preferred nutes and see where you are for ppm and pH.
After a few feedings you can watch for persistent chlorosis problems that might indicate a mag def.
Good luck, and happy growing!
id start at 1-1.5 g/gal for watering. not sure about foliar feed dosages
Thanks a lot guys!!!
I was wondering about the metal residues from condensers, but its already few runs that im using it with no issue at all ( With the difference that I always mixed my own organic soil )
This time I decided to buy some light mix soil and then start feeding with MC, mainly because with my organic recipe and potions I couldn’t keep up with the feeding demands of the plants under 640w Spectrum king LEDs + CO2 that were making plants hungry as fuck since 3rd week of flower…
Of course like everything, also this program needs to be dialed in properly…I had the bad luck of getting some very shitty potting soil (supposedly specific for cannabis…meeeeh…) and after gettin out of the woods regarding the ph unbalance and potassium toxicity, the plants came back to happiness and healty growth…so I started feeding em with MC with very nice results for a couple weeks
but…
thers always a butt…
Now some of them (the ones right under the light source) are getting alittle pale-er…nothing extremely allarming but it looks like that general pale that I was getting before with my organics and I think is time to address the issue…so im guessing I should add some CalMag to the water and maybe alternate with some Epsoms…
I just don’t want to mess up too much the calcium content of the MC that should be enough already…
I was thinking to try a low dosage of Epsom with just water next time and after that Calmag and megacrop…and keep checking!
Thanks again for the quick replies!!
Love you all!!
I run 1/3 to 1/2 teaspoon Epsom per gallon every other watering under LEDs and just once a week under hid lights.gl
Thanks Bobo…
On another forum a guy was very kind to provide this useful dosage and I will post it here too 
"If you shoot for a target range of ~75ppm Mg per gallon of water for foliar, then three grams per gallon should do it. "
“Common hydroponic fertilizers recipes, usually contain between 40-60ppm Mg. We have found that a range or 75-90ppm of Mg to ideal under LED lighting. The best way to increase only Mg and not introduce more nitrogen, is to add 1gram of epsom salt(Magnesium Sulfate) per gallon of nutrient solution. 1gram/gallon of epsom salt adds ~25ppm of Mg and 30ppm of S, and is usually a sufficient supplement to most fertilizer programs.”
I followed this guideline and I first sprayed with 3gxGal and after seeing good results like immediately greening up I decided to keep watering them every time with 1gxGal and is working like a charm!! Healthy, green , lush and very happy!!
I run MC in RO water and have heard stories about a lack of Mg. Was foliar spraying Mg @ 1mg per gal. I will up this to 3mg a gal and see what happens.
I always add a 1/4 tsp (1.5g) Epsom salt/gal (well water, .15 EC) during veg. You may need 2g/gal using MC. I’ve read in many forums that one shouldn’t use DH or AC runoff due to molds and other contaminants in the water. Just my .02.
I kept adding 1 g x Gallon of Epsoms with every watering with Megacrop and then after the 2nd week o flowering with Maxibloom too.
Im running super bright Led and the supplement was really needed. I just stopped a watering ago cause they all look nice and healthy green and also because im adding now CalMg from the mono nutrient line of Canna, im combining 6 parts of Calcium and 1 of Mg , in this way im not adding any more N.
Thanks for the hint Yooper about the recycled water…I never heard of that but makes sense…i’ll make more research…as far as now its the 3rd run with recycled water and I didn’t got any problem so far…
As far as the recycled water, seems that if the units are in a decent shape and you clean the filters diligently, should be fine…
https://www.maximumyield.com/free-water-dehumidifier-water-and-consumable-plants/2/1211
I just wish they were more energy efficient…im thinking to switch my 105 pints with another mini split and run it only as a dehum…maybe I could save power and push less heat in the room
Some per gallon ppm breakdowns, including epsom.
INteresting.
Thanks for posting this chart
1-2 grams per gallon for watering
3 grams per liter for foliar
What about adding Epsom salt to your soil mix during transplanting? Is that effective?
No…its 100% water soluble and pretty fast release…loaded in the soil will fry the plants in the first waterings…
As far as i know…dolomite lime its a good Mg supplement ( not enough for LEDs) slow release…but has ph buffering properties and will raise the PH of the medium…
I put a tblspoon in my 2 gal pots so the roots have to search for it.
Doesn’t fry mine.
Wow…i went and measured a TBS of Epsoms and its about 15 grams…
Based on what i red that is a big amount for a single watering…but i believe you…
Probably the salts melt instantly but the plant uptake em slowly ?!?!
Well maybe not a full tblspoon but close if you were to level it out.
Not heaping anyway.