What are signs of magnesium over-application?

The presence of excessive magnesium can cause problems that may be mistakenly attributed to another mineral deficiency. Symptoms in plants include weak stems that bend easily and new growth with leaf edges turning brown and crispy. Unlike deficiency patterns that typically start on older leaves, over-application issues tend to appear first in the new growth of the plant. I have diagnosed this condition in gardens where Epsom salts were used in excessive amounts without first testing the soil for its suitability.

Verify possible over-application using soil tests. Rely on a threshold of over 120 ppm to acknowledge "recalibrated". Simultaneously check potassium and calcium levels, as imbalances in these elements cause a greater number of symptoms. I have also tested cation exchange capacity to learn how minerals interact in the soil. Leaf tissue analysis accurately shows the actual ratio of nutrients a plant contains.

Immediately begin relief applications after you've confirmed the issue. Reduce all magnesium inputs to zero. Leach the soil with deep watering to flush excess minerals. Apply gypsum to replenish the calcium balance. I have successfully recovered tomato plants by applying potassium sulfate and calcium nitrate. Monitor for new growth to see the symptoms regress within a few weeks.

Avoid a repeat of this by balancing nutrient inputs. The calcium to magnesium ratio should be between 3:1 and 5:1. Do not use high magnesium fertilizers unless soil tests indicate a need. The magnesium levels can change seasonally, so it is critical to re-test the soil each season. Your surveillance will mitigate any future issues with over-application.

Read the full article: 7 Critical Signs of Magnesium Deficiency Plants