Ammonium sulfate (AS) [(NH4)2 SO4] as a nitrogen fertilizer has been used by farmers all over the world for over 150 years. It contains 21% Nitrogen and 24% Sulphur. Its high solubility provides versatility for a few agricultural applications. 

Ammonium sulfate is the most accessible source of low-concentration Nitrogen and is an excellent source of fertilization in crops which extract large quantities of Sulphur from the soil, such as vegetables (cruciferous vegetables, onions and garlic), cereals, maize, sorghum, sugarcane etc. It is widely applied directly to the soil as a single product and is also a relevant component in the production of balanced fertilization formulas. 

The first production processes of AS involved the release of ammonia during coal gas manufacturing or coal coke when producing steel. Ammonium sulfate of this production is classified as steel grade. But the final product of such production contains many pollutants that are harmful to the environment.

New technologies to produce environmentally friendly ammonium sulfate provide for its production during the production of caprolactam (capro grade) or by synthesis from ammonia and sulfuric acid (chemically pure). Such ammonium sulfate is widely used not only in agricultural production, but also in the food, pharmaceutical and biotechnological industries.  

Physiological effect:

Ammoniacal nitrogen (NH3) is readily available for absorption by plants by active transport. The positive charge of ammonium contributes to the simultaneous absorption by the plant of anions: phosphates, sulfates, borates, etc. During the active transport of ammonium, hydrogen ions are released into the environment, which causes a local decrease in the pH of the soil solution. Therefore, ammonium nitrogen is most effective when applied on neutral and alkaline soils. Ammonium sulfate is frequently used in flooded soils for rice pro duction, where nitrate-based fertilizers are a poor choice due to denitrification losses.

Many sulfur products only supply elemental sulfur, with the elemental sulfur not becoming available to crop roots until converted to sulfate. Once in the soil, this conversion can take anywhere from 90 days to several months, which leaves crops hungry for sulfur at critical growth stages. Ammonium sulfate fertilizers contain sulfur in the form of anion-sulfate (SO4–), unlike elemental sulfur, is immediately available for assimilation by the plant and does not require transformation by sulfur bacteria, which is especially effective when applied to crops sensitive to sulfur deficiency.  

Advantages of ammonium sulfate application as fertilizer:

1.   The physiologically optimal ratio of nitrogen and sulfur makes this fertilizer biologically valuable for nutrition of any growing plants including evergreens. The interaction of nitrogen and sulfur has a synergistic effect since both biogenic elements are key in the chain of amino acid synthesis. At foliar application both nutrients are quickly absorbed by the plant through the leaf surface and are immediately involved in metabolism. When farmers in western Canada introduced this product to their fields, production levels rose by up to 60%.

2.   In addition to providing nutrition with readily-available sulfate sulfur and ammonium nitrogen to your crops, ammonium sulfate assists plants with the uptake of other critical nutrients. In many soils, high soil pH decreases the solubility of phosphorus and critical micronutrients, impeding root uptake. When ammonium is absorbed by the crops, it acidifies their root zones, often unlocking phosphorus and key micronutrients such as zinc, boron, iron, copper and manganese from fertilizers and soil. 

3.   Ammonium sulfate is the best source of nitrogen for soil microbiota. It activates the accumulation of biomass by microorganisms and the decomposition of plant remains. This increases the content of organic matter and soil humus, and it promotes the transformation and biological availability of other nutrients.   When a product like ammonium sulfate fertilizer can improve the health of local soil, then the increased crop production that results can improve the amount of residue and root biomass that exists locally. There are direct benefits occurring every time an increase in soil organic matter happens after a growing season. That means an increase in the levels of organic carbon, nitrogen, phosphorus, and sulfur are possible. This advantage works to improve the long-term fertility of the soil. It also works to create benefits in the natural nutrient cycling process. Moreover, nitrogen immobilization by microflora is an additional mechanism for reducing losses of this element due to evaporation, leaching and denitrification.

4.   Ammonium sulfate fertilizer is affordable for the average grower. The price of ammonium sulfate fertilizer is one of the primary reasons why some growers prefer to use this chemical product. Synthetic items are typically cheaper than organic ones. By keeping your costs down when preparing your fields, it becomes possible to increase your profit margin on each item grown.

5.   Ammonium sulfate provides fast results. When you decide to use ammonium sulfate fertilizer, then you will not need to wait for several weeks or months before you start to see positive results. Once you apply the product to the soil, the improvements in your plants will happen within days. Chemical fertilizers like this one release nutrients at a much faster rate than organic products. As far as the amount of time required for the fertilizer to show results, ammonium sulfate is always an excellent solution.

6.   This fertilizer follows standardized labeling practices and ratios. When you choose to use an ammonium sulfate fertilizer, then you’ll see the nutrient ratios of the product clearly defined on the label of your bag or bucket. This advantage reduces the risk of over-fertilizing a garden or cropland. Although organic items might be healthier in the long-term for many fields, there is a higher risk of applying too much product – and that could result in plant death.

7.   The disinfecting property of ammonium sulfate fertilizer makes it possible to remove potentially harmful components from the soil when applied. Although it works best when alkaline conditions exist, there are some situations where an acidic foundation is also useful.

Environmental benefits of  Ammonium Sulfate:

(I) Ammonium sulfate is immediately available for root uptake and can even be applied to the soil surface under reduced tillage conditions. As a result, no N loss via NH3 volatilization when applied on the surface.

(II) Positively charged ammonium ions bind to negatively charged soil ions, making ammonium sulfate less susceptible to leaching. As a result, less NO3 leaching can increase N efficiency and reduce nitrate pollution of groundwater and eventually drinking water.

(III) The denitrification process that can cause nitrate loss in poorly-drained soils does not affect the availability of the ammonium in ammonium sulfate. As a result, less denitrification may increase N efficiency and minimize greenhouse gases (NO and N2O).

(IV) Production and application of ammonium sulfate provides the lowest contribution of CO2 emission to greenhouse gases.

Non-Agricultural Uses

Ammonium sulfate is a highly adaptable product that serves multiple functions in our society today. Some food companies like to add this item to bread because it works well as a dough conditioner. It is also a common component in fire extinguisher powders and flame-proofing agents. If you have items with a robust fire-resistance rating, then there is an excellent chance that one of the ingredients used in the manufacturing of that product is this item. Several different industries, including textiles, wood pulp, and pharmaceuticals, use ammonium sulfate in a variety of applications.

Ammonium sulfate can act as a disinfecting agent. Some municipalities like to use ammonium sulfate with chlorine as a way to generate an item called monochloramine. That makes the water safe for drinking because it disinfects the fluid effectively. It can also be useful in the preparation of some salts like ammonium persulfate. It is also a common ingredient that gets listed on many vaccines in the United States.