G Y P S U
everywhere. It is the most common sulfate mineral on earth
and of immense commercial value. Gypsum, known technically as Calcium Sulfate, is one
of the most useful and widely used minerals of the 20th
century. It is used in the building industry, food and
beverages, pharmaceuticals, and as a soil additive for the
landscape industry, and agriculture. Yet, despite gypsum's
widespread use, few people know what it is or where it came
from. Gypsum deposits are sediments from ocean brine and
ancient inland seas. Time, heat, pressure, moisture,
movement and mixing with other elements produces various
forms of gypsum.
nature provides two kinds of natural gypsum for agriculture:
ANHYDRITE and DIHYDRATE. Chemically, the only difference
between anhydrite gypsum and dihydrate gypsum is two
molecules of combined crystallized water.
two molecules of water and anhydrite
(CaSO4) contains no water molecules. The
absence of water molecules in anhydrite makes it harder
"denser" and heavier than dihydrate. The perferred
quality Gypsum, is predominantly anhydrite
The value of
agricultural gypsum is directly related to its percentage of
Calcium Sulfate. It is the anhydrite that accounts for
the high calcium sulfate content. Although the value of gypsum
as a soil additive has been recognized for decades, each
year field tests around the world reveal more and more of
the benefits of
Sulfate - CaSO4) is one of those rare materials that
performs in all three categories of soil treatment: an
amendment, conditioner, and fertilizer. Gypsum amends soil
alkalinity, lowers high pH conditions and raises low pH
conditions, and leaches out harmful salts. Gypsum conditions
and improves soil structure allowing air and water
penetration and root development.
the plant with Calcium & Sulfur.
Sulfate - CaSO4) is one of those rare materials that
performs in all three categories of soil
treatment: a soil amendment, conditioner,
Soil conditioners, such as gypsum,
are seriously undervalued compared to fertilizer usage. Dr.
Arthur Wallace (Ph.D. Soil Science and Plant Nutrition) and
Dr. Garn Wallace (Ph.D. Bio-Chemistry) of Wallace
Laboratories in El Segundo, CA, U.S.A., believes that if soil
structure ain't right, then nothing is
Gypsum contains both calcium and sulfur.
Calcium as “...an engineering superstar will be applied to
agricultural crops and landscapes more than any other
nutrient. Sulfur, once considered to be of minor
importance, is now regarded as a major, essential nutrient
along with nitrogen, potash and phosphorus.
When dissolved in water
gypsum becomes calcium ions (Ca2+ and sulfate-sulfur
ions (S042). Both of these ions are required nutrients for
growing plants. In addition to being a major plant nutrient,
calcium plays a vital role in establishing and maintaining
good chemical balance in soil, water and
There is a great
deal of confusion concerning the solubility of gypsum.
Solubility has emerged as almost the sole criterion for
evaluating gypsum. But, as a singular concept, separate from
other factors, the importance of solubility is more
misunderstanding than reality. As a practical matter,
solubility only has meaning in relation to time, particle
size and purity.
Soluble calcium is the
calcium found in the water in the soil or by applying
gypsum to the soil. Soluble calcium is directly
available for uptake by plants growing in the soil.
Insoluble calcium is often found in the soil as calcium
carbonate (The caliches soils in the
Texas Hill Country) and is not ready available to
plants. This form of calcium can only be converted to
soluble calcium by reaction with
Lets look at it from the plants
point of view. The bottom-line question here is
AVAILABILITY. How much calcium sulfate (nutrition) is
available to the plant to meet its gypsum requirement when
it needs it? As plants grow, they require continuous supply
of calcium because calcium becomes fixed and immobile
within the plant tissue.
is true with the soil. If it does not get gypsum when it
needs it, the soil may compact, prevent water and air
penetration, lose its leaching ability and become saturated
with salt or other excessive elements harmful to plant
growth and health. Then the plant suffers from bad soil
conditions. Poor soil structure is a major limiting
factor in plant health or crop
Soil management is
a continuing and long term process. There is no sudden
cure for ages of soil abuse and mismanagement. The
application of gypsum is a not a quick fix alternative with
over night results, however in the long term, soil moisture
Gypsum Improves Soil Structure - Gypsum provides
calcium which is needed to flocculate clays in acid and
Gypsum Helps Reclaim Sodic Soils
- Where the exchangeable sodium percentage (ESP) of sodic
soils is too high, it must be decreased for soil improvement
and better crop growth. The most economical way is to add
gypsum which supplies calcium. The calcium replaces the
sodium held on the clay-binding sites. The sodium can then
be leached from the soil as sodium sulfate to
an appropriate sink. Without gypsum, the soil
would not be leachable.
Gypsum Prevents Crusting of Soil
and Aids Seed Emergence - Gypsum can decrease and prevent
the crust formation on soil surfaces which result from rain
drops or from sprinkler irrigation on unstable soil. It can
prevent crusting that results when acid soils are lime&
the gypsum is co applied with the lime.
Gypsum Improves Low-Solute
Irrigation Water - Gypsum is used to increase the solute
concentration of low-solute water used for irrigation.
Irrigation water from rivers that no longer have sources of
leachable salts either penetrates poorly into soil or causes
soil particles to degrade which results in low-water
penetration. The problem can be corrected with
surface-applied gypsum or application to the irrigation
Gypsum Improves Compacted Soil -
Gypsum can help break up compacted soil and decrease
penetrometer resistance. Combination with organic amendments
also helps, especially in preventing return of the
Gypsum Makes Slightly Wet Soils
Easier to Till - Soils that have been treated with gypsum
have a wider range of soil moisture levels where it is safe
to till without danger of compaction or deflocculation.
Gypsum Stops Water Runoff and
Erosion - Gypsum improves water infiltration rates into
soils and also the hydraulic conductivity of the soil.
Gypsum Decreases pH of Sodic
Soils - Gypsum immediately decreases the pH of sodic soils
or near sodic soils from values often over 9 but usually
over 8 to values from 7.5 to 7.8. these values are in the
range of acceptability for growth of most crop plants.
Gypsum Increases the pH of Acidic
Soils - One mechanism in which gypsum can increase soil pH
enough in some acid soils to sufficiently decrease the level
of soluble aluminum to grow crops satisfactorily is
replacement of hydroxyl ions from some clay lattices by
Gypsum Improves Swelling Clays -
Gypsum can decrease the swelling and cracking associated
with high levels of exchangeable sodium on the
montmorillonite-type clays. As sodium is replaced by calcium
on these clays, they swell less and therefore do not easily
clog the pore spaces through which air, water and roots
Gypsum Prevents Waterlogging of
Soil - Gypsum improves the ability of soil to drain and not
become waterlogged due to a combination of high sodium,
swelling clay, and excess water.
Gypsum Can Help Remove Excess
Boron from Sodic Soil - More boron was leached from sodic
soils when gypsum was applied than when the soil was leached
Gypsum Increases the Stability of
Soil Organic Matter - Gypsum is a source of calcium which is
a major mechanism that binds soil organic matter to clay in
soil which gives stability to soil aggregates.
Gypsum Makes Water-Soluble
Polymer Soil Conditioners More Effective - Gypsum
complements or even magnifies the beneficial effects of
water soluble polymers used as amendments to improve soil
Gypsum Makes Excess Magnesium
Non-Toxic - In soils having unfavorable calcium magnesium
ratios, such as serpentine soils, gypsum can create a more
Gypsum Corrects Subsoil Acidity -
Gypsum can improve some acid soils even beyond what lime can
do for them. Surface crusting can be prevented. Gypsum is
now being widely used on acid soils.
Gypsum Can Enhance the Values of
Liming - Addition to soil together with lime increased crop
yields. The combination also decreased leaching losses of
potassium and magnesium.
Gypsum Improves Water-Use
Efficiency - Gypsum increases water-use efficiency of crops.
In areas and times of drought, this is extremely important.
Improved water infiltration rates, improved hydraulic
conductivity of soil, better water storage in the soil all
lead to deeper rooting and better water-use efficiency. From
25 to 100 percent more water is available in gypsum-treated
soils than in nontreated soils.
Gypsum Creates Favorable Soil EC
- Gypsum, being readily soluble, results in proper buffered
solute concentration (EC) in soil to maintain soil in a
flocculated state. It is better environmentally and costwise
to maintain the needed EC with gypsum than with excess
application of fertilizers.
Gypsum Makes it Possible to
Efficiently Use Low Quality Irrigation Water - Use of
reclaimed municipal waste water is important for
conservation of natural resources. Reclaimed water can be
satisfactorily used if amendments, such as gypsum and
water-soluble polymers, are also used.
Gypsum Decreases Dust Erosion -
Use of gypsum can decrease wind and water erosion of soil.
Severe dust problems can be decreased, especially when
combined with use of water-soluble polymers.
Gypsum Helps Plants Absorb Plant
Nutrients - Calcium, which is supplied in gypsum, is
essential to the biochemical mechanisms by which most plants
nutrients are absorbed by roots. Without adequate calcium,
uptake mechanisms would fail.
Our Hill Country caliche
soils are high in calcium, however it is not in a soluble
form for plant
Gypsum Decreases Heavy-Metal
Toxicity - Calcium also acts as a regulator of the balance
of particularly the micronutrients, such as iron, zinc,
manganese and copper, in plants. It also regulates
non-essential trace elements. Calcium prevents excess uptake
of many of them; and once they are in the plant, calcium
keeps them from having adverse effects when their levels get
high. Calcium in liberal quantities helps to maintain a
healthy balance of nutrients and non-nutrients within
Gypsum Increases Value of
Organics - Gypsum adds to the value of organic
Gypsum Improves Fruit Quality and
Prevents Some Plant Diseases - Calcium is nearly always only
marginally sufficient and often deficient in developing
fruits. Good fruit quality requires an adequate amount of
calcium. Calcium moves very slowly, if at all, from one
plant part to another and fruits at the end of the transport
system get too little. Calcium must be constantly available
to the roots. In very high pH soils, calcium is not
available enough; therefore, gypsum helps. Gypsum is used
for peanuts, which develop below ground, to keep them
disease free. Gypsum helps prevent blossom-end rot of
watermelon and tomatoes and bitter pit in apples. Gypsum is
preferred over lime for potatoes grown in acid soils so that
scab may be controlled. Root rot of avocado trees cased by
Phytophthora is partially corrected by gypsum and
Gypsum is a Source of Sulfur -
Gypsum is a source of fertilizer sulfur.
Gypsum Helps Prepare Soil for
No-Till Management - A liberal application of gypsum is a
good procedure for starting a piece of land into no-till
soil management or pasture.
Gypsum Decreases Bulk Density of
Soil - Gypsum-treated soil has a lower bulk density compared
with untreated soil.
Gypsum Decreases the Toxic Effect
of NaCI Salinity - Calcium from gypsum has a physiological
role in inhibiting the uptake of sodium by plants.
Gypsum Multiplies the Value of
Other Inputs - Gypsum can improve the response to all other
inputs including fertilizers.
Gypsum Can Decrease pH of
Rhizosphere - Increased calcium uptake by roots when gypsum
is applied can decrease the pH of the rhizosphere.
Gypsum Keeps Clay Off Tuber and
Root Crops - Gypsum can help keep clay particles from
adhering to roots, bulbs and tubers of crops like potato,
carrots, garlic and beets.
Gypsum Decreases Loss Of
Fertilizer Nitrogen to the Air - Calcium from gypsum can
help decrease volatilization loss of ammonium nitrogen from
applications of ammonia, ammonium nitrate, urea, ammonium
sulfate, or any of the ammonium phosphates.
Gypsum Can be a Source of Oxygen
for Plants - The sulfate that is taken up by plants and
metabolized releases the associated oxygen which is a source
of oxygen to plant roots although a limited source.
Gypsum Helps Earthworms to
Flourish - A continuous supply of calcium with organics is
essential to earthworms that improve soil aeration, improve
soil aggregation and mix the soil.
Gypsum Can Increase Water
Retention in Soil - Gypsum when applied to sodic soil
decreased levels of exchangeable sodium resulted in a large
increase in water retention at a given tension compared with
controls. Dry matter and seed yield were increased as a