[CH] Epsom Salts Information....
Imagator (imagator@preferred.com)
Sat, 19 Aug 2000 20:16:39 -0400
Dear List,
I can neither vouch for the accuracy of the following nor have I personally
tried. I am forwarding to the list as information only, also would like
opinions.
Charlie
Fertilize with Epsom Salts
Use this old household remedy to give some plants a boost
by Charlie Nardozzi
After working with home gardeners for more than 10 years, I know that they
love to use home remedies on their plants. From setting out beer traps for
slugs to hanging bars of soap to repel deer, if the household product seems
to work, gardeners try it. That's why I was intrigued by the often-mentioned
idea of using Epsom salts as a fertilizer.
Gardeners apply it to tomatoes, peppers, and roses, hoping to produce more
flowers, greener plants, and higher yields. You can use it to improve
magnesium content if you know you have a soil that's deficient in that
element, but home gardeners are most likely to apply Epsom salts to peppers,
tomatoes, and roses.
I wanted to find out if it really works and learn the best ways to apply it
for best growth, so last summer I asked some of our test gardeners (home
gardeners who test seeds and products for National Gardening magazine) to
test Epsom salts' effects on plant growth and vigor by applying it to pepper
plants and roses. Then I talked to researchers about using the salts as
fertilizer. Here's what I found out.
The History and Science of Epsom Salts
This natural mineral, discovered in the well water of Epsom, England, has
been used for hundreds of years, not only to fertilize plants but to treat a
range of human and animal ailments. Who hasn't soaked sore feet in it at
least once?
Chemically, Epsom salts is hydrated magnesium sulfate (about 10 percent
magnesium and 13 percent sulfur). Magnesium is critical for seed germination
and the production of chlorophyll, fruit, and nuts. Magnesium helps
strengthen cell walls and improves plants' uptake of nitrogen, phosphorus,
and sulfur.
Sulfur, a key element in plant growth, is critical to production of
vitamins,
amino acids (therefore protein), and enzymes. It's also the compound that
gives vegetables such as broccoli and onions their flavors. Sulfur is seldom
deficient in garden soils in North America because acid rain and commonly
used animal manures contain sulfur, as do chemical fertilizers such as
ammonium sulfate.
The causes and effects of magnesium deficiencies vary. Vegetables such as
beans, peas, lettuce, and spinach can grow and produce good yields in soils
with low magnesium levels, but plants such as tomatoes, peppers, and roses
need high doses of magnesium for optimal growth. However, plants may not
show
the effects of magnesium deficiency until it's severe. Some common
deficiency
symptoms are yellowing of the leaves between the veins, leaf curling,
stunted
growth, and lack of sweetness in the fruit.
Magnesium tends to be lacking in old, weathered soils with low pH, notably
in
the Southeast and Pacific Northwest. Soils with a pH above 7 and soils high
in calcium and potassium also generally have low magnesium levels. Calcium
and potassium compete with magnesium for uptake by plant roots, and
magnesium
often loses. Sometimes, a soil test will show adequate magnesium levels in
soil, but a plant grown in that soil may still be deficient because of that
competition.
Gardeners add magnesium when they apply dolomitic lime to raise the soil's
pH. However, this product (46 percent calcium carbonate, 38 percent
magnesium
carbonate) breaks down slowly, and the calcium can interfere with magnesium
uptake. For soils with a pH above 7, many gardeners use Sul-Po-Mag (22
percent sulfur, 22 percent potassium, 11 percent magnesium) to increase
magnesium. Although dolomitic lime and Sul-Po-Mag are inexpensive ways to
add
magnesium, Epsom salts' advantage over them is its high solubility.
When diluted with water, and especially when applied as a foliar spray,
Epsom
salts can be taken up quickly by plants. Epsom salts' magnesium content,
high
solubility, and ease of application as a foliar spray are the main reasons
for the positive results many gardeners see in their plants.
What Our Testers Found
To get a first-hand look at the effectiveness of Epsom salts in the garden,
we asked six of our testers (in California, Colorado, Iowa, Pennsylvania,
and
Tennessee) to try Epsom salts on peppers and roses. Testers each grew six
'Gypsy' peppers. They applied 1 tablespoon of Epsom salts mixed with a
gallon
of water as a foliar spray to three plants at bloom time and again 10 days
later. They also selected two established rose bushes of the same variety
and
sprayed the same amount of Epsom salts mixed with water to one bush every 6
weeks, starting when leaves came out and continuing through the summer
(about
4 applications). We asked them to record the number of pepper fruits and
rose
blooms, and to note any differences they saw.
Four out of the six testers reported that the Epsom salts-treated pepper
plants and fruits were larger than the controls. For the treated roses,
testers reported greener foliage, bushier plants, and more roses than on the
control plants.
Kathy Stone Downie of Alameda, California, noticed many differences in her
treated 'Gypsy' peppers. "The fruits were much bigger, almost twice the
size.
They were juicier, sweeter, and triple the thickness of the untreated
peppers." Tommy Owen, in Rogersville, Tennessee, said that his treated roses
had greener foliage and bigger flowers with deeper colors.
Recent Studies of Epsom Salts
Scientists are beginning to test its use. Although many studies confirm that
magnesium sulfate is a good way to supply magnesium and sulfur to soils
deficient in those elements, little research has been done on the use of
Epsom salts as a supplemental fertilizer on soils with adequate levels of
these nutrients.
Renee Schloupt, horticulturist at Delaware Valley College in Doylestown,
Pennsylvania, is testing peppers and tomatoes grown in a greenhouse
environment under drought and nondrought conditions. She's comparing control
plants with those watered with applications of 1, 2, and 3 tablespoons of
Epsom salts mixed with 1 gallon of water and applied at planting, flowering,
and fruit set. So far, she has not seen any measurable evidence of growth or
yield differences in the treated tomatoes or peppers. "The peppers have
greener leaves, and it seems the 1- and 2-tablespoon doses yield a better
result than the 3-tablespoon dose, but I haven't seen any dramatic effects
on
yields so far," she says. "The magnesium in the Epsom salts applied to the
soil could be getting tied up with other nutrients. We might see better
results when we apply Epsom salts directly to the leaves."
At Auburn University in Alabama, plant pathologist Kira Bowen and soil
scientist Beth Guertal see similar results when they apply Epsom salts
directly on the soil. They are conducting a 3-year study of roses in field
plots that includes applying 1 cup of Epsom salts per plant per month as one
of the treatments to increase plant vigor and control black spot. "The first
year, we saw reduced defoliation in the Epsom salts-treated plants, but the
second year the differences weren't there," Bowen reports. "This year [1997]
will be the deciding year. I think it's hard to find a direct link between a
specific nutrient such as magnesium sulfate and increased yield or plant
growth because of all the other variables in the soil, such as pH, calcium
and potassium content, and weather, that may affect the plants."
Is Using Epsom Salts Worth a Try?
In their studies, researchers applied Epsom salts directly to the soil.
Foliar applications, such as those our test gardeners used, appear to be a
better way to guarantee that the plants get the benefits of the added
magnesium.
Before you try Epsom salts, test the soil to determine its magnesium
content.
Don't rely on Epsom salts to correct large soil magnesium deficiencies, but
rather use it as a supplement to soils with adequate or slightly low
magnesium levels to boost plant growth, flowering, and fruiting. For
severely
magnesium-deficient soils, use dolomitic lime or Sul-Po-Mag. Foliar
applications of Epsom salts seem work better than adding it, dry or mixed
with water, directly to the soil. Plants may not efficiently take up
magnesium sulfate in granular form, especially in alkaline soils or soils
that already test high in potassium, calcium, or magnesium. If you have
tested your soil and know it has those qualities, a foliar application is a
faster way to get the nutrients to the plant.
Roses
Many rosarians agree that Epsom salts produces more new canes at the bottom
of the plant (bottom breaks) and darker green foliage. Recommendations on
how
much to use vary, but generally you can apply 1/2 cup of granules in spring
before buds first begin to open and 1/2 cup in fall before leaves drop.
Apply
a foliar spray (1 tablespoon per gallon of water per foot of shrub height)
after the leaves open in spring and again at flowering.
Tomato and Peppers
Magnesium deficiency in the soil may be one reason your tomato leaves yellow
between the leaf veins late in the season and fruit production slows down.
Test your soil every 3 years or so to check on nutrient levels. Epsom salts
can keep plants greener and bushier, enhance production of healthier fruit
later in the season, and potentially help reduce blossom-end rot. Apply 1
tablespoon of granules around each transplant, or spray a solution of 1
tablespoon Epsom salts per gallon of water at transplanting, first
flowering,
and fruit set.
Epsom salts is available in drug and grocery stores.
Epsom salts works best on soils that are...
* Slightly deficient in magnesium
* Alkaline (show high pH) as in western areas
* Old, "weathered," and acidic (with low pH) soils of the Southeast and
Pacific Northwest
* High in calcium and potassium (western soils)