Ammonium sulphate is one of the first and most widely used nitrogen (N) fertilizers for crop production. It is now less commonly used, but especially valuable where both N and sulfur (S) are required. Its high solubility provides versatility for a number of agricultural applications.
Ammonium sulphate Fertilizer (sometimes abbreviated as AS or AMS) has been produced for over 150 years. Initially, it was made from ammonia released during manufacturing coal gas (used to illuminate cities) or from coal coke used to produce steel. It is made from a reaction of sulfuric acid and heated ammonia. The size of the resulting crystals is determined by controlling the reaction conditions. When the desired size is achieved, the crystals are dried and screened to specific particle sizes. Some materials are coated with a conditioner to reduce dust and caking. Most of the current demand for ammonium sulphate is met by production from by-products of various industries. For example, ammonium sulphate is a co-product in the manufacturing process of nylon. Certain by-products that contain ammonia or spent sulfuric acid are commonly converted to ammonium sulfate for use in agriculture. Although the color can range from white to beige, it is consistently sold as a highly soluble crystal that has excellent storage properties. The particle size can vary depending on its intended purpose.
Ammonium sulfate is used primarily where there is a need for supplemental N and S to meet the nutritional requirement of growing plants. Since it contains only 21% N, there are other fertilizer sources that are more concentrated and economical to handle and transport. However, it provides an excellent source of S which has numerous essential functions in plants, including protein synthesis. Because the N fraction is present in the ammonium form, ammonium sulphate is frequently used in flooded soils for rice production, where nitrate-based fertilizers are a poor choice due to denitrification losses. A solution containing dissolved ammonium sulphate is often added to post-emergence herbicide sprays to improve their effectiveness at weed control. This practice of increasing herbicide efficacy with ammonium sulphate is particularly effective when the water supply contains significant concentrations of calcium, magnesium, or sodium. A highhigh-purity grade of ammonium sulphate is often used for this purpose to avoid plugging spray nozzles.
|Composition||N content: 21% S content: 24%|
|Solution pH||5 to 6|
|Molar Mass||132.14 g/mol|
|Appearance||Fine white hygroscopic granules or crystals|
|Density||1.769 g/cm3 (20 °C)|
|Melting point||235 to 280 °C (455 to 536 °F; 508 to 553 K) (decomposes)|
|Solubility in water||70.6 g/100 mL (0 °C) 74.4 g/100 mL (20 °C) 103.8 g/100 mL (100 °C)|
|Solubility||Insoluble in alcohol, acetone and ether|
|Moisture by weight||>1.0|
|Arsenic as (As2O3)||<0.01|