St0ney

Hello everyone!

It has come to my attention that some advice I was giving out was incorrect. In particular, my advice about Magnesium Deficiency and Epsom Salt. When I first started growing I was told (at another site that will remain nameless ) that Marijuana had very high needs for Magnesium and most hydro nutrients didn't have enough. So adding Epsom Salt was the trick to keeping Magnesium Deficiency away. So for every grow since then I’ve used Epsom salt, and I have advised others to do the same.

Well, The other day Ozgrowa informs me that, that is incorrect. Well, I was shocked to say the least. He informed me that a low PH usually 'locks out' Magnesium and most hydroponic nutrients have plenty of it.... And some have too much.

So, being the computer geek that I am.. I immediately started researching this and found him to be quite correct.

Here is the truth about Magnesium Deficiency

First let's start off defining a few terms.

Magnesium (Mg)- is essential to photosynthesis in plants. It’s the "main molecule" in chlorophyll, the green coloring in green plants! Photosynthesis is the process by which plants use the sun’s energy to create carbohydrates. Without magnesium, plant leaves turn yellow (usually at the bottom) and will soon die.

PH- is measured on a scale of 1-14 with 7 being "neutral". Acids are lower than 7 and alkalis (bases) are above 7. To be technical, the term pH refers to the potential hydrogen-hydroxyl ion content of a solution. Solutions ionize into positive and negative ions. If the solution has more hydrogen (positive) ions than hydroxyl (negative) ions then it is an acid (1-6.9 on the pH scale). Conversely if the solution has more hydroxyl ions than hydrogen it is alkaline (or base), with a range of 7.1-14 on the pH scale.
Pure water has a balance of hydrogen (H+) and hydroxyl (OH-) ions and is therefore pH neutral (pH 7). When the water is less than pure it can have a pH either higher or lower than 7.

Why should you care about any of this?

When the pH is not at the proper level marijuana will lose it's ability to absorb some of the essential elements required for healthy growth. For all plants there is a particular pH level that will produce optimum results. Marijuana likes it's hydroponic solution to be 5.5 to 6.1. Although most plants can still survive in an environment with a pH of 5.0 to 7.5.

If the pH is too high, marijuana suffers from a lack of iron, zinc, manganese, copper and boron. If the pH is too low, it lacks phosphoric acid, calcium, and magnesium. At lower pH (more acidic) ranges, diseases can thrive. Normally, plants tend to take up more acidic elements, causing pH levels to increase or drift up the scale.

Now, from my understanding of this is, you should let your hydroponic solutions 'drift' up to 5.9 to 6.0 to allow the Magnesium to be available without the addition of Epsom salt (which results in EDTA lockouts because we are adding too much Magnesium.)

Please correct me if I’m wrong on this Oz.

__________________

"A man's ethical behavior should be based effectually on sympathy, education, and social ties; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death." -- Albert Einstein

OzGrowa

I think that summizes the situation very well st0ney, good job with that man!

Id also say that the whole system of nutrients is a delicate balance of +ve and -ve ions, adding a certain element such as Mg usually has the effect of altering the potential with a sudden and drastic availability of the element within solution, the plant uptakes this solution and the problem is further compounded as the plant goes further away from centre...I have read so many growers say "wow the plants have gone really green bafter I added the Epsom Salts" (excess Mg symptoms) then a few days later its "my plant has stopped growing and is starting to yellow in the leaves" (Iron lockout).... as a further example or approach to the overall picture of nutrient solutions think of ph correction....adding ph up (+ve ions) to a solution that you have added too much down ie acid (-ve) to, it shouldnt be done, the whol solution should be dicarded. As it is in DWC, NFT, Dripper,etc etc in hydroponics, if we discard and completly replace our solutions regularly (and use a hydroponics nutrient to begin with) deficiencies will become non existant. Occasionally, and I mean occasionally we will need to add a slight amount of Mg, and it should be fractional, but this should be such a rare situation if the other practises are correct.

Ph drift is a great thing, letting it climb to 5.9- 6.1 isnt going to have an adverse effect whatsoever, in fact the inverse is true, the rise will permit correct iron, potassium and phosphorous uptake and prevent the deficiencies that people claim to be experiencing. This is especially the case during flowering, the PH rise will result in slightly more P being absorbed so the constant battle to keep the PH at 5.5 or even lower I think is a little futile.

Oz

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St0ney

I also ran a crossed quite a few pH/ Nutrients Availability charts while researching this but, due to copyright issues I couldn't use them.. So I had to make my own.

I've tried to make this as accurate as I could.. If anyone sees a problem please let me know.

This chart shows how pH affects nutrient availability.

__________________

"A man's ethical behavior should be based effectually on sympathy, education, and social ties; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death." -- Albert Einstein

DrZook

So I guess that if you use hydro nutes there is really no reason to add Epsom Salts unless you see definite signs of Mg deficiency. And even if you do, the pH is more than likely causing a nute lockout problem rather than an actual lack of Mg. So the bottom line is that Epsom Salts are an unnecessary addition to our hydro systems, right?

I guess the amount of Epsom Salts that have been recommended must not be enough to cause significant harm (or we all probably would have noticed by now) but I will be happy with one less ingredient to worry about.

Thanks to St0ney and OzGrowa (The 'Nute Masters ) for setting the record straight!

Oh yeah, awsome work on the chart St0ney!

__________________
Catch ya on the flip side...
-Dr. Zook

Dr. Zook's Grow v2.1

St0ney

I have re-worked the hydro chart for easier reading & more accuracy. And I have created one for soil as well, even though this is the hydroponic forum I’m still gunna post it since it's relevant to the discussion.

Later,

__________________

"A man's ethical behavior should be based effectually on sympathy, education, and social ties; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death." -- Albert Einstein