Epsom Salt Drench: Everything You Need to Know

April 16, 2021
Category: Growing Tips

Do you need to do an Epsom salt drench? In this article we discuss why you might consider using an Epsom salt drench with your plants, and if so, how to properly formulate what you need.

What is EC?

As you test your soil or soilless growing media for nutrient levels, you’ll pay attention to two primary levels: pH and EC. pH is a familiar indicator of the acidity of a substance, and the necessary levels will depend on which plants you’re growing.

EC stands for electrical conductivity, which is a measure of a solution’s ability to conduct electricity. This measure indicates how much soluble salt is found in the growing medium. A higher ability to conduct electricity indicates more salt; a high EC indicates a growing medium with too much salt. A lower ability to conduct electricity means a low EC, which may point to inadequate fertilization. If your EC is low, increase the rate or frequency of your fertilizing program, or consider using a different fertilizer. 

Why would I leech nutrients from my growing medium?

A high EC level indicates that soluble salts are outside the normal range. The soluble salts typically found in soil are calcium, magnesium, sodium, chloride, sulfate, and bicarbonate. There can also be small amounts of potassium, ammonium, nitrate, and carbonate. A growing medium that has too many of these nutrients for an extended period of time can cause root rot, leaf chlorosis, and burn plant matter. It’s important to maintain a proper EC level to keep plants healthy. A normal level is about 2.0-3.5 mS/cm measured using a Saturated Media Extract method

Why use Epsom Salts?

Epsom salts are known to reduce stress on plants and refresh them by washing away nutrient buildup from the growing medium and roots. 

In addition to giving your plants a good cleanse, Epsom salts can also help regulate the Magnesium and Sulfur content of your soil, especially if your EC levels are out of normal range. 

How to do an Epsom Salt drench

If your soil’s EC levels are off, use an Epsom salt drench to leach extra nutrient buildup from the growing medium.

Use Epsom salts at 1 TBSP per gallon of water. If you have your injectors set at 1:100, then add ¾ lb Epsom salts per gallon in the stock tank. That will give you ¾ lbs of Epsom salts per 100 gallons since your injector will inject 1 gallon of stock tank solution per every 100 gallons that flow through the system. Run this through a normal irrigation cycle, then you can go right back to feeding as usual at the next appropriate water cycle. (Some people believe you should immediately follow that irrigation cycle with a second additional irrigation cycle, but we have not found this necessary.) 

At your next watering, allow the medium to dry out and recheck the EC level to determine whether it has lowered to a normal range. Perform the back-to-back irrigation again if the EC level is still too high. 

Going forward, make any adjustments that may be needed, based on your determination.

Benefits of an Epsom Salt Drench

This method gives the roots and soil a bath and washes away nutrient buildup. The Epsom salts can also help to green up the foliage of your plants. 

An Epsom salt drench will not address root rot due to high fertilizer rates. Use a fungicide to address the root rot, and adjust your fertilizer levels.