Epsom salts, also known as magnesium sulfate (MgSO4), are a natural compound of the minerals magnesium and sulfur and are often associated with relaxation and taking a bath or soaking tired feet after a long day. Epsom salts are inexpensive and are typically safe for a lawn, but you'll need to conduct a soil test to determine if this compound is the right solution for your turf.
Do a Soil Test First
Before deciding to use Epsom salts on your lawn, it's a good idea to do a soil test to check for low levels of magnesium. Soil tests are available at many home garden centers and nurseries and are an inexpensive, easy way to measure the type of soil in your garden as well as the pH level. A test will also highlight what nutrients are in the soil, including minerals — calcium, magnesium, potassium, and phosphorous — and what adequate levels should be.
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Soils that have sufficient magnesium won't benefit from Epsom salt, and its use could potentially be harmful to the soil and the lawn. Once you conduct a soil test, you can decide if applying Epsom salt will be beneficial for your lawn.
Most Soils Aren't Deficient in Magnesium
Magnesium is sometimes lacking in the soil; this deficiency may be caused by a mineral imbalance either in the plants or in the soil. Some soil types, such as acidic or sandy soils, are more likely to lack magnesium. When conducting a soil test, you'll want to note the levels of other minerals in the soil. High levels of potassium in the soil can affect roots' ability to absorb magnesium, for example.
Magnesium is an important mineral for grass and other plants because it's a component of chlorophyll, which is essential to photosynthesis and results in the green color associated with plants. Sulfur is also important for the growth of plants. In most cases, however, using Epsom salts on a lawn won't be necessary.
Spread or Spray Epsom Salts
If you have determined that your lawn can benefit from Epsom salts, take some safety precautions before applying it. First off, put on gloves to protect your skin since magnesium sulfate is easily absorbed by the skin.
You can add Epsom salts to a grass seed spreader to ensure even distribution throughout the lawn, or you can mix the compound in water and spray it over the grass. It's recommended that for every 100 square feet of lawn, you apply 1/2 pound of Epsom salt. The best time to apply Epsom salt to turf is during the cooler months, typically during the fall and spring. Avoid applying Epsom salts during winter, when grass often grows more slowly due to the cold.