There are divided opinions on the use of Epsom salts in the garden, and some have observed that there is not much research to prove that their application is beneficial. However, many gardeners swear by this practice, and Epsom salts have been used to amend the soil for generations.
Epsom salts can be sprinkled around the base of plants or tilled into garden soil. They can also be applied as a foliar feed or in drip irrigation using one tablespoon of salts to one gallon of water. The magnesium and sulfur they contain can boost plant growth, photosynthesis, and crop yields.
Epsom salts are naturally occurring minerals consisting of magnesium, sulfur, and oxygen. While it sounds like it should taste salty and looks similar to table salt, its chemical composition is entirely different. Although it has a bitter, unpleasant taste, it has been used for human health in various contexts.
The Benefits Of Epsom Salts In An Organic Garden
Since Epsom salt is a naturally occurring chemical compound, it is acceptable for use in an organic garden, unlike manufactured chemical fertilizers. Organic gardeners cannot use artificial pesticides, insecticides, and fertilizers, so they must look to natural products instead. Epsom salt can remedy magnesium deficiencies in soil or boost plants that require higher quantities to bloom and fruit.
Lettuce, Swiss chard, beans, and English peas will do just fine in soils low in magnesium. However, plants like tomatoes, eggplants, and peppers won’t. Magnesium sits at the core of the chlorophyll molecule in green plants. If there is a magnesium deficiency, their growth is poor and stunted because they cannot synthesize light properly.
Epsom salts help keep foliage green, improve the plant’s capacity to absorb other nutrients from the soil, and significantly reduce the need for chemical fertilizers. You don’t want to use other chemical fertilizers in an organic garden, so Epsom salts are a boon. Epsom salts can also improve seed germination.
Magnesium strengthens the cell walls of germinating seeds and ensures sufficient energy for growth. Epsom salts also don’t build up to harmful levels in the soil or poison groundwater like so many artificial chemical fertilizers.
Misting plants with an Epsom salts solution can prevent curling leaves and transplant shock when planting new seedlings from a nursery. They also deter slugs, snails, and voles. If Epsom salts are applied to crop plants just after flowering, they can also help to grow more flavorful, sweeter vegetables and fruit.
In a test to look at the benefits of Epsom salts on peppers and roses, Charlie Nardozzi, a senior horticulturist at the National Gardening Association, asked six test gardeners in Tennessee, California, Colorado, Iowa, and Pennsylvania to do the following. They each grew six Gypsy pepper plants. Then they applied a solution of one tablespoon of Epsom salts mixed with a gallon of water as a foliar spray to three pepper plants.
The three remaining pepper plants were used as a control, and the gardeners did not apply Epsom salts to them. They were asked to record the number of peppers each plant produced and note the differences if any. Four of the six gardeners reported that the pepper plants treated with Epsom salts grew larger than those that weren’t.
They also said that the fruits were larger, almost twice the size, and sweeter, juicier, and thicker than the untreated peppers. The roses they tested produced more canes from the bottom of the plant and had greener leaves.
Some scientists in Alabama and a horticulturist in Pennsylvania treated tomato and pepper plants with Epsom salts by applying a solution directly to the soil. Unlike the gardeners, they reported that they couldn’t see much benefit but did not use Epsom salts as a foliar spray. However, it is not known how the soil conditions in these tests compared with those in the test gardens.
Nardozzi noted that Epsom salts work best on alkaline soils, i.e., with a high pH, older and acidic soils, soils high in potassium and calcium, or slightly deficient in magnesium.
Epsom salts can be used to make cucumbers greener and less tired-looking. You can also boost grapevines, berries, and nut and fruit trees with a generous application of Epsom salts solution to the roots once a month during the growing season.
The Impact Of Sulfur In Epsom Salts On A Garden
The other chemical in Epsom salts is sulfur. It is also critical to plant growth to produce proteins, enzymes, and vitamins. Sulfur is essential for all crop growth and development. It assists in chlorophyll formation and the activation of plant enzymes that help in biochemical reactions. Sulfur increases crop yields and the quality of produce.
The growth of plants deficient in sulfur is hindered, and they tend to be spindly and slender with fruits that don’t mature. It is not needed in high quantities, but it is necessary for vigorous, healthy plants. Sulfur contributes to the flavor of garlic, onions, and mustard plants.
Sulfur is obtained chiefly from soil and manure, but too much of it will have an adverse effect as it can build up in the ground, so adding sulfur alone is not generally recommended. However, only a small quantity of sulfur is present in Epsom salts which do not build up in the earth.
Crops That Have Higher Magnesium Requirements
Crops that are tolerant of low magnesium in soil are radishes, lettuce, beans, beets, sweet potatoes, and Swiss chard. Those sensitive to magnesium deficiencies are eggplants, tomatoes, peppers, cucumbers, squash, watermelons, and other Cucurbit family members.
Brassicas such as broccoli, cabbage, and cauliflower can also have issues when magnesium is low. Wheat and corn have been shown to be very susceptible to heat stress if grown in soil deficient in magnesium.
Researchers noted in 2020 that due to the emphasis in modern times on NPK (nitrogen phosphorous and potassium) fertilizers, people have lost sight of the need to replenish magnesium in the soil, resulting in large-scale magnesium deficiency. This is particularly true in intensive crop farming.
Since magnesium is required for human and animal health, this trend is concerning. The researchers also found that magnesium fertilizers promoted the yield for most crops, but especially fruit, grasses, tubers, and vegetables.
Causes Of Magnesium Deficiency
Certain crops such as potatoes can deplete the magnesium in the soil. Signs of magnesium deficiency in soil are loss of green coloration in the leaves. In potato plants, the leaves begin to turn yellow from the tip towards the leaf center. Corn develops a stripy appearance along the length of the leaf.
Magnesium deficiency can occur in acidic, sandy soils. It is a secondary macronutrient that, together with calcium and sulfur, is required for healthy plant growth and photosynthesis. Primary nutrients are potassium, nitrogen, and phosphorous.
This doesn’t mean that magnesium, sulfur, and calcium are less important than the primary nutrients. They are just required in smaller quantities. The tissue of some plants contains pretty much the same levels of magnesium, a secondary nutrient, as phosphorous.
Plants can get most of their magnesium requirements from water, but not all water contains sufficient quantities of this secondary nutrient. If the water doesn’t have a minimum of twenty-five parts per million magnesium, supplementation with Epsom salts is necessary.
Magnesium is vital for plants not only because it is essential for photosynthesis but because it is used in water uptake, respiration, phosphate, and nitrogen metabolism, cell division, and protein formation and synthesis. To establish if your water contains sufficiently high magnesium levels, you need to have it tested by a laboratory.
Over-use of fertilizers high in potassium can inhibit plant uptake of magnesium. If the leaves of a plant are yellowing while the leaf veins remain green, this is a sign of magnesium deficiency. It is called interveinal chlorosis. Magnesium deficiency commonly occurs in roses, rhododendrons, grapevines, apples, tomatoes, and raspberries.
Magnesium Deficiency In Tomato Plants
In tomato plants, a sign of severe magnesium deficiency is yellowing, purplish leaves that die off at the bottom of the plant. Excessive application of high potassium fertilizers can cause a magnesium deficiency because the tomato plant will absorb the potassium in preference to magnesium.
You may only see evidence of magnesium deficiency in tomato plants mid-season when the plants are heavy with tomatoes. Magnesium deficiencies can result from light, sandy or acidic soil, heavy rainfall, cold and wet environments, improper fertilization, or soil high in potassium.
How To Apply Epsom Salts
Magnesium deficiency is frequent in sandy soils that leach easily and in high tunnel crops, especially tomatoes. Epsom salts can be applied through a drip irrigation system or as a side dressing around the plants if there is a magnesium deficiency.
The standard dose is one tablespoon of Epsom salt when applied as a side-dressing. In a drip system, you should dissolve one to two pounds of Epsom salts in one hundred gallons of water and drench the plants with it. Don’t mix the salts with any other water-soluble fertilizer.
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You can also create a foliar spray consisting of a solution of 2% Epsom salts in water and apply it to the leaves of the plants for a week. The foliar feed spray should be used on the leaves early in the morning while their pores are still open. In the heat of the day, the leaf pores close to prevent water loss.
Many plants can easily absorb Epsom salts diluted in water. You can use a solution of 2 tablespoons of Epsom salts to one gallon of water as a foliar spray once a month. In the case of tomatoes and peppers, apply one tablespoon of Epsom salts in the soil around the plant while transplanting. Do the same after they first bloom and again when they are setting fruit.
You can test the pH of your soil using a test kit available at garden stores or online. University extension offices can also conduct a professional test. If your soil pH is seven or higher, you don’t need to increase the pH. This is where Epsom salts come in.
- Contains components for 80 tests. 20 each for Soil pH, N, P and K
- Comes with sturdy plastic case
- Simple and detailed instructions included
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Epsom salts do not alter the soil’s pH. If you need to do this, you would add lime rather than Epsom salts. Lime adds magnesium while at the same time raising the pH. If you have not sown your crop yet, till your garden bed with a hoe or a rototiller to a depth of eight inches.
Once you have thoroughly tilled the soil, sprinkle the Epsom salts in granular form over the bed or dissolve them in water and then irrigate the bed with the solution. You should always have your soil tested before applying Epsom salts or lime.
The pH of acidic soil is less than six, and such soil is more likely to be deficient in magnesium than soils with a higher pH. If the soil is gravelly or sandy, it may have sufficient magnesium but not in a form readily absorbed by plants.
Using Epsom Salts On Roses
To benefit roses, apply half a cup of Epsom salts to the surrounding soil in spring before the buds open, and half a cup before the leaves drop in fall around the base of the plant. Use a foliar spray consisting of one tablespoon of Epsom salts per gallon of water for every foot of shrub height after the leaves open and again at flowering time.
When planting a rosebush, you can also put a tablespoon of Epsom salts at the bottom of each hole. To prevent shock to plant roots, apply a solution of one tablespoon of Epsom salts to one gallon of water. After you’ve transplanted, you saturate the plant’s roots with this solution.
Other Uses Of Epsom Salts
To deter slugs and snails, you can sprinkle Epsom salts around the base of plants in the garden. Alternately you can mix a cup of Epsom salts with five gallons of water and apply it as a foliar spray.
To boost fruit and nut trees and berry patches, you can water their roots with a solution of one tablespoon of Epsom salts mixed with one gallon of water.
Conclusion
You should test your soil and water or see apparent signs of magnesium deficiency in plants before you add Epsom salts. They can boost crop yield, result in more flavorful and sweeter fruit and vegetables, and improve plants’ processing of other nutrients. The fact that they occur naturally means they can safely be used in organic gardens and won’t build up in soils like other artificial chemical fertilizers.
Resources For Further Information
- https://extension.umn.edu/micro-and-secondary-macronutrients/magnesium-crop-production
- https://www.sulphurinstitute.org/about-sulphur/sulphur-the-fourth-major-plant-nutrient/
