What does gypsum contain

This topic can get a little confusing due to the chemistry and causes of soil acidity, and the different ways in which lime and gypsum react in the soil. The short answer is that pure gypsum will not affect the pH of the topsoil when surface applied or incorporated by typical methods.

However, gypsum is able to offset some of the toxic effects of extremely acid subsoil, in some soil types. Gypsum may even increase the pH of those subsoils to some degree. These seemingly contradictory statements can be explained by the differences in the chemistry between lime and gypsum, plus the somewhat unique nature of most acid subsoils. Some people think that gypsum will increase soil pH. This belief is apparently based on fact that gypsum contains a significant amount of Ca.

Without getting too deeply into the chemistry of lime, a short description of how lime works will help to illustrate why gypsum will not neutralize soil acid. The principle acid-neutralizing power of agricultural lime is caused by the carbonate CO 3 in both the calcium carbonate CaCO 3 and magnesium carbonate MgCO 3 , not so much by the Ca nor Mg. Both lime minerals work in the same way to neutralize acid. The beneficial effect of gypsum on some acid subsoil occurs by a different type of chemistry.

If acid neutralizing power were the only consideration, then lime would be the material of choice to neutralize acid subsoils. The problem with lime is that it is not very mobile in the soil. Therefore, in order to neutralize acid subsoils in any reasonable amount of time, the lime must be physically mixed into the subsoil. This is not something that most farmers can accomplish. Gypsum can affect subsoil acidity in a shorter time frame because it is much more mobile in the soil and can be leached into the subsoil by irrigation or rainfall.

In extremely acid subsoils pH 5. Excess soluble Al is toxic to plants. The same benefit would occur in the topsoil if it were at the same pH. However, in this case, we can use lime in which we get the benefits of acid neutralization plus the effects of Ca and Mg. Depending on the nature and particle size of lime, it could require up to 18 months for the lime to completely react and neutralize acid topsoil.

Gypsums effects on subsoil can take less time, depending on how fast it can be leached through the subsoil. Because gypsum is highly soluble, it is an excellent source of Ca and S, especially for acid-loving crops and ornamentals, plus a few crops that are especially responsive to either Ca or S for reasons other than soil pH.

Acid soils are by nature low in Ca. Where additional Ca is needed, gypsum is an ideal source for these crops. Potatoes are often grown in acid soil to control common scab. In these conditions, gypsum can improve tuber quality.

Commercial Christmas tree producers have greatly improved the quality of their acid-loving species with applications of gypsum. Blueberry producers have also found gypsum to be benefit with that acid-requiring crop.

The list of acid-loving ornamentals is much too long to include here, but any of these plants are likely to benefit from additional Ca that does not increase the soil pH. While peanuts do not require acid soils, they are very responsive to applied Ca as gypsum.

These two uses for gypsum require somewhat more complicated calculations in order to determine the appropriate rate of application. Reducing soil Na levels is by far the more complicated process and the following is only a superficial discussion of correcting this problem.

A much more in-depth discussion is presented in Spectrum Analytics paper entitled "A Guide to Interpreting Irrigation Water Analysis", which can be found in the Library at spectrumanalytic. Reducing Na to a particular saturation percent: The following calculation may be used when there is a specific percent Na saturation target to be achieved. Gypsum requirements can be calculated from the residual sodium carbonate RSC value of the irrigation water from the following equation.

Remember, gypsum alone does not solve a high Na problem, you must apply adequate irrigation water or wait for enough rainfall to leach the displaced Na out of the root zone. This calculation is to simply increase the soil Ca to some desired percent Ca saturation through the use of gypsum. The formula was published by North Carolina State University. Gypsum is sometimes recommended in order to adjust the soil Ca:Mg ratio to some desired value.

The previous formula designed by N. State Univ. However, The idea that there is some "ideal" soil Ca:Mg ratio is a myth, and not worth pursuing.

Competition between Ca and Mg for uptake by crops has become a perennial topic of discussion in agriculture. Often times, the ideal Ca:Mg ratio is somewhere between and Some of the claimed benefits of this ideal soil Ca:Mg ratio include.

As we know today, the "total" soil content of CA, Mg, or any nutrient has little relationship to its availability or uptake by crops.

It also has literally nothing to do with the general fertility of the soil. The cation ratios resulting from these idealizes concentrations are a Ca:Mg of 6. It appears that since this time, these ratios have been seized upon by some people as the "ideal" ratios, rather than examples of good ratios. Since these published figures, we have seen that many top yields of many different crops have been produced in soils with cation nutrient ratios much different than those first published.

Also, a significant amount of research has looked at the question of nutrient ratios and almost no results have supported the claim of some "ideal" ratio. Fertile soils commonly have a Ca:Mg ratio between and However, this does not mean that the specific Ca:Mg ratio is required, best, or even related to yield. Research results show that this ratio can be as narrow as or as wide as without negative effects, assuming that there is an adequate amount of each nutrient in the soil.

In the mid's the University of Wisconsin conducted research into the effect of Ca:Mg ratio on alfalfa growth. They found that while the Ca:Mg ratio in the plant tended to reflect the soil Ca:Mg ratio, the plant content of these nutrients was affected much less and in no case did the soil or plant ratio affect yield. In this work the plant Ca and Mg contents were never below the respective critical levels for each nutrient, even though the soil Ca:Mg ratios ranged from 2.

Gypsum CaSO 4. The chemical difference is that gypsum contains two waters and anhydrite is without water. Gypsum is the most common sulfate mineral. Gypsum uses include: manufacture of wallboard, cement, plaster of Paris, soil conditioning, a hardening retarder in portland cement. Varieties of gypsum known as "satin spar" and "alabaster" are used for a variety of ornamental purposes; however, their low hardness limits their durability.

Gypsum wallboard and plaster: Wallboard and construction plaster are the primary industrial uses of gypsum in the United States.

Alabaster Gypsum: Alabaster, a variety of gypsum, from Pomaia, Italy. Specimen is approximately 3 inches 7. Gypsum will change soil pH very slightly, yet it can promote better root development of crops, especially in acid soils, even without a big pH change. This is because the gypsum counteracts the toxic effect of soluble aluminum on root development.

But when soil becomes acidic, the aluminum is available to plants—and it can stunt or kill them. Another bonus of gypsum is that it is a moderately-soluble mineral. This means the calcium can move further down into the soil than the calcium from lime calcium carbonate.

This can inhibit aluminum uptake at depth and promote deeper rooting of plants. When roots are more abundant and can grow deeper into the soil profile, they can take up more water and nutrients, even during the drier periods of a growing season.

Although moderately soluble, gypsum can be an excellent source of sulfur over several growing seasons. Research found that the sulfur is available not only in the year applied, but can continue to supply sulfur for one or two years after, depending on the initial application rate. Gypsum as a sulfur fertilizer has benefitted corn, soybean, canola, and alfalfa. Gypsum can also help improve soil structure.

The calcium ion from gypsum replaces the sodium ion and allows it to be dissolved and leach away, removing it from the soil profile.

Note: An increase in soil sodicity Na increases soil susceptibility to crusting, seal formation, runoff, and erosion. Soils with lots of surface area, such as those with high clay content, tend to have higher matrix potential at a given water concentration.

In osmotic flow, water moves from an area of low salt content to an area of higher salt content. Soils with lots of salt may look moist but plants can not absorb this moisture due to this effect. Hence, gypsum helps reduce this effect and helps plants use the moisture stored in the soil. Note: We use salt to preserve food items from pickles to salted meats. The same osmotic pressure pulls water out of the microbes that would cause spoiling hence preserving the food.

The same thing happens in soils except the water is pulled from mycorrhizal fungi, nitrogen fixing bacteria and other good microbes, killing them. Weathered soils which are chemically stable do not release electrolytes nutrients and respond readily to gypsum applications.

On young soils which weather readily and release electrolytes, the addition of gypsum will have fewer effects. Note: On sandy soils excess gypsum may cause a tie-up of Mg and K. The sorption of Ca and SO4 by plants is higher in woodland soils that in cultivated soils. Microbes in the woodlands soil help plants take up the nutrients more efficiently. Some studies have found that gypsum application reduces run-off to less than half of untreated soils and by increasing surface roughness and flow path tortuosity it decreases runoff velocity.

This reduces interrill erosion and other erosion effects from raindrops. Recycled gypsum can be mixed with ground wood chips for animal bedding. It can substitute for sawdust or sand to absorb moisture and reduce odors. Poultry bedding - Studies have shown the percentage litter moisture was significantly lower for refined gypsum than for the wood shaving treatments at 21 and 41 days, although on a weight basis the gypsum contained the same amount of or more water. Litter material had no influence on room or brooding temp.

Although it is quite dusty initially when placed in the house, refined or recycled gypsum can be used for bedding, as a base with wood shavings. Recycled gypsum can be mixed with animal wastes to combine with ammonium NH4 to form ammonium sulfate to prevent loss of nitrogen and thus reduce odors. Ammonium sulfate is odor free. Alfalfa - source of sulfur 1 ton per acre provides 17 pounds of sulfur. Alfalfa needs 25 pounds per acre of sulfur to make a good crop.

Another report indicated that it helped grow stronger healthier stems. One study found that 16 tons per acre gave best yields. Another study found that only pounds per acre doubled yields. No harmful effects have been found. Alliums - increased growth rates and bulb size Almonds - increased growth and yields Barley - increased yields Citrus - significantly reduced root rot caused by Phytophthora parasitica, reduced salinity effects of salts and improved plant growth citrus is salt sensitive.

Ginseng - did not affect tissue calcium but a significant increase in both shoot growth and root dry weight. Grapes - in California gypsum has been used for over 25 years.

Used by many wineries to increase production. All peanuts grown in gypsum treated fields had less Aflatoxin produced on them when compared to unsupplemented peanuts.

Legumes - require lots of sulfur to form nitrogen fixing nodules on the roots. Gypsum has been particularly useful to peanut farmers and to some extent to watermelon farmers. Plants that can benefit from gypsum include: Flowers - clematis, lilacs, irises, delphiniums, alyssum stock, candy-tuft, nasturtium, tulips, gladioli, roses, camellias and gardenias Landscape plants - evergreens, rhododendrons, mountain laurel, pin oak, sweet gum and flowering dogwood Potatoes Significantly reduced incidence of internal brown spot and soft rot, in several locations around the country.

The best control of the disease of common scab of potato S. The mean tuber yield response due to sulfur addition was 1. Addition of sulfur S by gypsum was effective in overcoming the sulfur deficiency symptoms and in increasing the sulfur concentration in the leaves. One study found that growers using , pounds of gypsum per acre had potatoes with stronger cells, they were more uniform in appearance, a decrease in internal brown spotting, and increased storage time Strawberries - increased yield and reduced soil disease Tomatoes earlier ripened fruit with larger fruit the fruit also had higher levels of some nutrients worked better in reducing blossom end rot as compared to other calcium sources calcium chloride CaCl2 , calcium nitrate Ca NO3 2, , etc.

Raspberries - it controlled Phytophthora root rot better, significantly increased plant growth, fruit yield, and root growth compared to other methods and control Sugarcane - increased growth rates Vegetables - cabbage, broccoli, cauliflower, radishes, turnips, kale and onions have all been shown to benefit from gypsum Wheat - increased yields Wheatgrass Agropyron elongatum - gypsum increased growth rates and increased biomass, corrected nutrient imbalances due to sodium.