Exploring the Role of Magnesium Salts in Sustainable Soil Management

Hello everyone,

I’d like to open a discussion about a group of minerals that are often overlooked in permaculture practice: magnesium salts, such as magnesium sulfate (Epsom salt), magnesium chloride, magnesium carbonate, and magnesium oxide.
While nitrogen, phosphorus, and potassium get most of the attention in soil fertility discussions, magnesium plays a key role in photosynthesis (it's the central atom in chlorophyll molecules), and magnesium deficiency can significantly affect plant growth, especially in fruiting and flowering crops like tomatoes, peppers, and citrus.
Why Magnesium Salts Matter in Permaculture:
Soil amendment: Products like magnesium oxide or magnesium carbonate can help adjust soil pH, especially in acidic soils, and support microbial activity.
Nutrient balance: Magnesium sulfate (Epsom salt) provides both magnesium and sulfur, which are essential for protein synthesis and enzymatic processes.
Stress resistance: Magnesium chloride, though less commonly used in agriculture, may improve stress resistance in certain crops by enhancing ion balance in saline soils.

Considerations for Use:
Overuse of certain magnesium salts (especially chlorides) may impact soil microbiota.
Always test your soil before applying — excess magnesium can antagonize calcium and potassium uptake.
Application methods (foliar spray vs. soil amendment) and timing can make a big difference in effectiveness.

Experience & Questions
Has anyone here experimented with natural or synthetic sources of magnesium in your permaculture projects?
Do you prefer Epsom salt, dolomitic lime, or other forms of magnesium?

I'm especially curious about:
Magnesium's role in compost health and mulching systems
Results in no-till or food forest systems
Synergies with calcium, boron, or sulfur amendments
Looking forward to hearing your experiences and insights!

Warm regards,
Danny
Magnesium-based soil amendment researcher

I am a firm believer in the benefits of magnesium salts as I use it ever night to help with pain.

I feel you are looking for something plant based or soil based of which I know nothing.

I feel a soil test would explain that.

I'm not a big fan of soil tests, I'd rather let the plants do the talking! So how would I know that the soil was low in magnesium? How would it affect my plants growth?

Nancy Reading wrote:I'm not a big fan of soil tests, I'd rather let the plants do the talking! So how would I know that the soil was low in magnesium? How would it affect my plants growth?

I had no idea so I looked it up, not sure how reliable this is ..

"The first sign of deficiency generally appears on the lower half of the plant/s, and is recognized when a yellow discoloration appears between the leaf veins.

"There could also be signs of premature autumnal leaf tints and dying leaves.

"If left untreated this problem will move higher up the plant/s."

https://www.thegardenersalmanac.co.uk/Content/M/Magnesium%20defficiency/Magnesium%20Defficiency.htm

Thanks Ac! That sounds a bit like symptoms of Nitrogen deficiency too.
From the same site:

Sometimes if the pH is not quite right this will prevent plants taking up magnesium.

Low soil pH decreases the magnesium availability, and high soil pH increases availability.

So I might get symptoms of low magnesium due to my acidic soil too....