Ammonium Sulfate and Gypsum

You’ve heard the saying, “the right tool for the right job.” In agricultural production, the saying should be changed to “the right chemical for the right job.” Ammonium sulfate and calcium sulfate, commonly known as gypsum, are both products that are important to agriculture. They share one trait in common – the chemical sulfur is part of their makeup – but that is where the similarities end.

Ammonium Sulfate, (NH4)2SO4

Ammonium sulfate is a non-hazardous, nitrogen-rich fertilizer that also helps lower soil pH.  The nitrogen in ammonium sulfate tends to be stable, so it is available throughout the growing season. This reduces the need for repeated applications.  Applying ammonium sulfate to alkaline soil not only adds needed nitrogen, its acidifying capability helps make soil micronutrients such as calcium, boron and magnesium more readily available to growing plants. Ammonium sulfate fertilizer can be used on acidic soils as well, but will require alternate lime applications to prevent the soil pH from decreasing.

Herbacide Application ASAmmonium sulfate is highly soluble, so its impact on soil fertility and pH is immediate. Its solubility also makes it an ideal addition to glyphosphate-based herbicide applications by substantially increasing herbicide effectiveness; using a slightly acidic spray allows the liquid to better penetrate plant tissues which makes the herbicide more effective. Hard water is also known to bind with the glyphosphate molecules and render them ineffective; ammonium sulfate added to the water counteracts hardness. It has been found that ammonium sulfate fertilizer is one of the best nitrogen sources for soil crops such as soybeans and increases the production of sulfur-bearing amino acids in legumes and alfalfa. Ammonium sulfate is a non-hazardous byproduct derived from the production of Caprolactam.

Gypsum, CaSO4·2H2O

By contrast, gypsum is a soil amendment rather than a fertilizer. It contains no nitrogen or other macronutrients, so for the purposes of fertilization, gypsum needs to be used in conjunction with a nitrogen source such as urea. Gypsum does help to stabilize the nitrogen in urea fertilizer and reduces volatilization. Gypsum is used primarily to loosen clay soils and to reduce the sodium content of sodic soils as well as to add calcium.  Gypsum is mined from rock sources, pulverized and refined; it takes a long period of time to degrade completely into the soil. This is a positive when it is used to reduce soil compaction and increase the friability of clay, but tends to be a negative when the need for increased soil calcium is urgent. Even though gypsum is a sulfate compound, it does little to change soil pH; one soil testing lab has stated that it is the impurities in lower grades of gypsum that act to change pH. A high grade gypsum is pH neutral.Virginia-Soil

Virginia soils range in pH from acidic in the eastern regions to alkaline in the mountainous areas. Find out your soil’s pH and fertility level through soil testing, and then purchase and apply the right products in the right amounts to make any needed adjustments. Commonwealth CIS is a distributor of high quality ammonium sulfate and can provide your farm with ammonium sulfate by the 50 pound bags, 3000 pound bags or supersacks. Commonwealth CIS also provides ammonium sulfate to manufacturing firms and to the tanning industry.

Image Credit:

Soil Component Name in Virginia, By J. Albert Bowden II

Post Emergence Stomp, by Chafer Machinery

Gypsum, by Kevin Walsh

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Commonwealth Industrial Services, Inc. (CIS) is an industrial services company located in Hopewell, Virginia. Although historically a service business, CIS’ primary profit center is the packaging and resale of ammonium sulfate.
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