To fix magnesium toxicity soil, flush the area with clean water. This pushes extra magnesium salts below your root zone. It is the fastest fix that university services back. Stop all Epsom salt or magnesium use right away before you do anything else.
Most magnesium over-application garden trouble starts when you use Epsom salt too often with no test. I made this mistake in my second year of serious vegetable growing. Monthly drenches turned into weekly ones after I read a blog saying more was better. By midsummer, a white salt crust covered the soil around my tomatoes. The leaves turned dark blue-green and growth stopped cold. Two weeks of deep watering brought my plants back, but I lost about a month of good production.
Toxicity signs trick most of you because they do not look like a magnesium problem at all. Extra magnesium fights with calcium and potassium for entry into your roots. When magnesium takes too many of those spots, your other nutrients cannot get through. Your plants may show what looks like calcium shortage with blossom end rot and weak stems. Or they mimic potassium shortage with scorched leaf edges. The real cause is too much magnesium blocking everything else.
To flush soil excess magnesium from your garden, follow a clear plan. For your pots, run clean water through equal to twice the pot volume. A 5-gallon pot needs 10 gallons poured through over about 30 minutes. For your garden beds, Clemson Extension says to apply 1 extra inch of water beyond your normal amount for three days in a row. The goal is to dissolve the built-up salts and push them below where your roots can reach.
After you flush, switch to a fertilizer that has calcium in the mix to help restore your nutrient balance. Look for products with calcium nitrate or gypsum listed. These add calcium without changing your soil pH and help offset the extra magnesium still in the ground. Avoid any fertilizer with more magnesium until your follow-up test confirms levels have come down.
Get a soil test 4 to 6 weeks after your flush to check if magnesium has dropped enough. If the test still shows high levels, repeat the flushing and test again. Do not start using Epsom salt again until the lab says your magnesium sits in the right range for your crops. Keep notes on every treatment and test result. Tracking your progress helps you avoid the same mistake next season.
Read the full article: Epsom Salt for Plants
