What is Ammonium Sulfate?

Ammonium Sulfate, sometimes abbreviated AS or AMS, is an inorganic salt used in various crystals, powders, and granules as a chemical fertilizer in agriculture. Diammonium sulfate and hydrogen ammonium sulfate are other names for this fertilizer. The molecular composition of this fertilizer is 21% nitrogen in the form of ammonium (NH4) and 24% sulfur in the form of sulfate (SO4). As you know, the role of nitrogen and sulfur in this fertilizer in plant growth and development is undeniable. It is very necessary for the usually alkaline soils of Iran because the ammonium ion in this fertilizer increases its acidity as it is released into the soil. Following the reduction of soil pH, the supply and absorption of nitrogen required for plant growth are more easily done. As mentioned, the nitrogen of this fertilizer is in the form of ammonium, and its sulfur is in the form of sulfate. In this case, ammonium is exchanged with clay particles and leached less into the soil than other nitrogen fertilizers.

Nitrogen is basically one of the most important elements for achieving high yields for most crops and orchards, and the lack or deficiency of this element in the soil will severely limit the growth of the plant so that even the formation of stems will be difficult. As a result, the plant will not even be able to enter the reproductive phase and produce the product.

Nitrogen is an important component of organic compounds such as chlorophyll pigments, coenzymes, and proteins. Nitrogen is a stimulant for plant growth. One of the forms of nitrogen that is applied to the plant as a source of nitrogen is ammonium. Ammonium has a positive charge that absorbs by soil anions, so its mobility and leaching are low. Sulfur and nitrogen in ammonium sulfate in the soil cause sulfuric acid and nitrogen to form ammonium.

Uses

- Primary use of ammonium sulfate is an agricultural fertilizer for alkaline soils. Ammonium ions are released into the soil and produce a limited amount of acid. Reducing the pH of the soil provides the nitrogen needed for plant growth. The most important problem of using ammonium sulfate is its nitrogen deficiency compared to ammonium nitrate, which increases transportation costs.

- It is also used in agriculture as an auxiliary spray for water-soluble insecticides, fungicides, and herbicides.

- It is used to produce other ammonium salts, especially ammonium persulfate.

- Ammonium sulfate is used as a wood preservative. But today, it is less used due to corrosion in metals.

The role of ammonium sulfate fertilizer in agriculture

Nitrogen is one of the most important factors in achieving optimal yield and increasing plant yield in agriculture.

Nitrogen is the most abundant element in the atmosphere and is the most consumed element by plants, which is absorbed in the form of nitrate, ammonium, and urea ions through the roots and, after transfer to the leaves, participate in the synthesis of amino acids and finally creates proteins.

Nitrogen is an important part of plant organic compounds such as chlorophyll pigments and coenzymes. Nitrogen stimulates the vegetative growth of the tree and, if consumed in large quantities, leads to the formation of soft tissues and increased offshoot and trunk offshoot in the tree and harms the production process, so the optimal amount of nitrogen fertilizers should always be used to have the best effect on plants function.

Nitrogen required by plants is supplied from two sources of chemical fertilizers and organic fertilizers. Ammonium sulfate is primarily used for cases where nitrogen and sulfur are needed as soil supplements and to meet the needs of growing plants. Although ammonium sulfate fertilizer contains 21% nitrogen and other fertilizers contain a higher percentage of nitrogen (for example, urea contains 46% nitrogen), the nitrogen in ammonium sulfate fertilizer is wasted, and it has much less leaching than other nitrogen fertilizers as well as ammonium sulfate fertilizers are an excellent source of sulfur, which has several basic functions in plants, especially the production of proteins.

Advantages of ammonium sulfate fertilizer

This fertilizer has been produced for more than 150 years. It was originally made from ammonia released during coal gas production and was used to illuminate cities. Ammonium sulfate is also obtained from coal coke, which is used to make steel.

By using ammonium sulfate instead of urea fertilizer, rice production can be increased up to 800 kg/ha. Unlike urea fertilizer, this fertilizer has less nitrogen wasted in the fields. Also, the sulfur in this fertilizer will improve the quality and increase the harvest. Ammonium sulfate contains ammonia nitrogen, which is quickly absorbed and consumed by the plant with the least amount of energy consumption. The presence of sulfur in the form of sulfate in this fertilizer, along with nitrogen, regulates soil pH and facilitates the absorption of other micronutrients in the soil, including iron, zinc, copper, and manganese.

This fertilizer can be used for urea-sensitive products such as citrus, grapes, and pistachios. Ammonium sulfate and relieving the yellowing of old leaves that occurs due to reduced soil nitrogen also removes yellowing of young leaves that occur due to sulfur deficiency.

Mixing this fertilizer with herbicides and pesticides may improve their effectiveness (when the water used contains significant concentrations of calcium, magnesium, or sodium). It is worth mentioning that ammonium sulfate has the lowest water absorption among other nitrogen fertilizers, which reduces clumping and increases its storage time.

Management of ammonium sulfate fertilizer use

After being added to the soil, ammonium sulfate decomposes rapidly into its constituents, ammonium, and sulfate. If you use it on the soil surface, ammonium may be prone to gas loss in alkaline conditions. In this case, it is recommended to mix the material inside the soil as soon as possible or before irrigation or to predict rainfall.

Most plants are able to use both ammonium and nitrate nitrogen for growth. In warm soils, microbes will quickly begin to convert ammonium to nitrate during the nitrification process.

Ammonium sulfate can acidify the soil due to the nitrification process, which has nothing to do with the presence of sulfate because it has little effect on pH. The potential for acid production by ammonium sulfate fertilizer is greater than for ammonium nitrate because all N in ammonium sulfate is converted to nitrate while only half of N in ammonium nitrate is converted to nitrate.

Uses of ammonium sulfate fertilizer

Ammonium sulfate is used for many agricultural products, especially pistachios, citrus, alfalfa, corn, canola, cotton, potatoes, rice, and wheat, and improves the quality and better growth of these products.

Environmental problems of ammonium sulfate fertilizer

Soil nitrogen is supplied from two sources, including organic and chemical fertilizers. In animal manures and green fertilizers, nitrate is a highly water-soluble anion that is not absorbed by the soil and can easily move to the roots or be removed from the plant by leaching. Urea is also mobile and can be removed by leaching despite easy absorption. Therefore, leaching of nitrate and urea into the soil can contaminate water resources, especially groundwater; but ammonium has a positive charge and, like other cations, is absorbed by soil particles, so its mobility, leaching, and consequently its loss is limited.

Urea in alkaline and calcareous soils can also cause problems and further increase soil alkalinity as well as salinity poisoning. If ammonium sulfate fertilizer due to the presence of sulfur in its chemical structure and its decomposition in the soil and the formation of sulfuric acid, and the presence of nitrogen in the form of ammonium causes soil alkalinity is reduced and has no negative effect on the environment. Therefore, this type of fertilizer has less destructive effects on the environment than other chemical fertilizers.

Properties of ammonium sulfate fertilizer

Safety in transport and storage relative to ammonium nitrate, pH modifying properties of alkaline, saline, and calcareous soils, increasing plant resistance to dehydration, a suitable alternative to urea fertilizer as a nitrogen fertilizer, increasing the effectiveness and absorption of phosphate in concomitant use with phosphate fertilizers, minimum energy consumption by the plant for rapid absorption and consumption of ammonium nitrogen in plant metabolism, prevention of yellowing and leaf fall, increased growth in leaves and canopy in trees, increasing crop quality, yield and fruit are the main properties of ammonium sulfate fertilizer, which makes it superior to other nitrogen fertilizers.

Time and amount of ammonium sulfate fertilizer consumption

It is better to use any type of agricultural fertilizer to improve and strengthen the soil of agricultural lands and orchards, based on the result of soil test and with the opinion of experienced experts in the region and the uses, distribution method, fertilization time, and fertilizer effect should be considered. If ammonium sulfate fertilizer remains on the soil surface under alkaline conditions, ammonium can be lost as a gas. So if the soil of your farm is alkaline, it is recommended to mix the fertilizer with the soil or use fertilizer before irrigation or rain and apply fertilizer.

Also, due to the fact that the nitrogen form in this fertilizer has high acidic properties, if this fertilizer is used too much, lime can be used to reset the soil pH.