Because it sounds good together, cal mag, it just flows off the tongue easily.....and sales.

Yeah it’s a joke. If some situations (like growing in soilless medium with RO) then you need to add Ca & Mg. But for most growers there’s a ton of both in their feed and water and I swear 90% I see this advice it’s wrong. It’s a mystery for the ages why every single brown leaf gets a post that says “looks like a CalMag deficiency”. It’s mind numbing.

mancorn said:

Yeah it’s a joke. If some situations (like growing in soilless medium with RO) then you need to add Ca & Mg. But for most growers there’s a ton of both in their feed and water and I swear 90% I see this advice it’s wrong. It’s a mystery for the ages why every single brown leaf gets a post that says “looks like a CalMag deficiency”. It’s mind numbing.

Click to expand...

i respectfully disagree. ever heard of soft/hard acidic/alkaline water. depending what water you have... you may have high ppm water full of cal and mag or low ppm water with little calcium and magnesium....which if you drank it all day... might actually rob your body of nutrients. Quick!!! Is your water soft? better run and check!!! you might find that you have water that is in fact not full of this so called calcium and magneseum you think it is!!!

While I will agree, most diagnosis of cal mag deficiency is rather unsubstantiated on this forum, it comes from people who have done little to no research, much like certain other people cough cough...

Let me explain... There is 100% merit behind "calcium and magneseum". Different levels of nutrients can become available/unavailable for uptake at different times. Changes to ph, temp and cation exchange/ionization zones can and do naturally effect nutrient uptake making some nutrients more available and other nutrients less available for plant absorption

Please look at the nutrient availability/PH chart below, good sir. Notice anything in particular, especially regard Cal and Mag. Interesting. It would seem Cal and Mag respond similarlyy to LOW PHs. Thus it would only make sense that they are sold together, as a deficiency/unavailability of one usually will beget the other...

Please note the data in this chart may have been updated. This is just a quick google search example.

I never said no one every needs CaMag, I said that most growers don’t need a CalMag supplement. And it’s especially true for the novice grower in dirt as there’s so many sources of both it’s unlikely to be a problem. And I don’t need to check my 40 ppm tap because I’ve got a shit ton of Ca & Mg in the rock phosphate (used in AACT) and langbeinite fertilizers, and in the Epsom salt (used in alfalfa tea), in my compost, etc., etc.

Back 10-12 years ago when it was only HPS lights I never heard of anyone really using it. I thought it was used because of the LED lights?

I will say that I didnt need much, my water is about 150-180 ppm out the gate. Using more caused some problems, but I always thought you use it because of the LED lights

There is a ratio of Ca:Mg that has to be maintained for some plants, but I don't know if that figured into the reason for having Cal/Mag.

In early nute mixes, it might have been that adding both Ca and Mg with phosphorus compounds, sold pre-mixed, in bottles, would cause the three of them to precipitate out of solution and be unavailable to plants. Then it was hard to stop selling it once they started.

Study cation exchanges! Also, the ratio of calcium to magnesium in tap water is not ideal for a mag hungry plant, especially under LEDs

Lots of misinformation in regards to calcium and magnesium but most is kind of on the right track. Calcium in your water is in carbonate form and won't be made available to the plant unless you continue to add an acid such as peat. Your best bet as a soil grower is gypsum hands down. You don't want a bunch of carbonates in your soil and the plant can't take it up like that. A plant is at least 10% calcium if not more. magnesium just needs to be present but it needs to be there always or you are in trouble but not in high qty like calcium though. With gypsum the sulfur wants to bond with the magnesium over the calcium so leachable epsom salt forms and calcium is then made available. With carbonates they just add up and build up and not leach which can drive a pH higher or just not have cal available

Add calcium nitrate if you need calcium. Add epsom salt if you need magnesium. Most people just buy them together for convenience and prefer 1 bottle that fixes the 2 most common deficiency. Most advanced growers will only add what they need so that their PPM don’t raise more then they need to. Recommend calmag (new grower or not good at reading deficiency). Recommend calcium or magnesium separate (advanced grower who knows how to identify and treat deficiency better).