Does Epsom salt help tomato calcium deficiency?
Written by
Tina Carter
Reviewed by
Prof. Charles Hartman, Ph.D.Many gardeners mistakenly use Epsom salt to address calcium deficiencies in tomatoes, despite scientific studies that show the salt actually exacerbates these deficiencies. The magnesium in Epsom salt directly competes with calcium taken up at the root, and can cause further disruption in plants suffering from calcium deficiencies. This mistake delays treatment of the problem while causing additional damage to the plants.
Nutrient Competition
- Magnesium and calcium share same root absorption pathways
- Excess magnesium blocks calcium ion receptors
- Creates artificial calcium shortage even in rich soils
Chemical Imbalance
- Epsom salt raises soil magnesium beyond 3:1 Ca:Mg ratio
- Disrupts cell membrane permeability in roots
- Reduces calcium transport to developing fruits
Physiological Stress
- High magnesium increases plant water requirements
- Accelerates blossom end rot lesion expansion
- Causes premature fruit drop in severe cases
Magnesium and calcium have an antagonistic relationship in terms of plant nutrition. Overdosing on Epsom salt could dangerously affect the ratios of nutrients. Tomatoes need calcium at 1-2% of dry weight, while magnesium is useful at only 0.3-0.5% dry weight. An imbalance in these two nutrients manifests itself in plants with visible symptoms of a nutrient deficiency, regardless of the level of calcium available in the soil.
Immediately fix any Epsom salt damage. Flush your soil with two inches of water to remove excessive magnesium. Use foliar applications of calcium chloride to work around damaged roots. Test your soil before applying any other supplements. I redeemed plants this way last season.
Use Epsom salt exclusively if a magnesium deficiency has been established. Symptoms include yellowing in the space between leaf veins and purple stems. Mix one tablespoon of Epsom salt into one gallon of water and treat plants a maximum of once per month. Please do not use it as a calcium substitute. My plants responded to this rule.
Different treatments for calcium work in various ways. Calcium nitrate does not compete with magnesium for nitrogen. Gypsum is a soil conditioner that provides calcium and improves soil structure. Both treatments successfully eliminate the nutrient conflict involving magnesium that can arise when using Epsom salt.
Keep in mind that blossom end rot is indicative of a failure of calcium to move into the tomato plant and is not a magnesium deficiency. As a result, you would not be able to correct this physiological condition by using Epsom salts. Your efforts are better directed toward consistency in watering and providing a pH that is correct for optimal tomato health.
Read the full article: Calcium Deficiency Tomatoes: Prevention and Solutions
