Impact Fertilisers
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Sulphate of Ammonia (SOA)

N% P% K% S% Zn%
Typical Analysis 21 0 0 24 0

cropping-canola

Chemical Name
Sulphate of ammonia
Crop Segments
All
Features
Source of nitrogen and sulphur as a straight fertiliser and in blends.
Quality & Handling
Off-white granule 2-4 mm nominal sizing, free flowing properties.
Bulk density 1.05 tonnes per cubic metre.
Blending
Blends with most products and trace elements.

1. Features and benefits

  • Sulphate of ammonia is commonly used as a source of nitrogen and sulphur.
  • It is commonly blended with other fertilisers to supply sulphur.
  • It has good storage and handling qualities, and can be readily blended with other fertilisers.
  • Higher nitrogen cost can be one of the main factors limiting the use of SOA, however, if the value of the available sulphate sulphur is considered it can be good value.
  • Where conditions exist that nitrogen losses through volatilisation of Urea occur  SOA can be used more efficiently as its nitrogen is in the ammonium form.

2. Manufacture

SOA is often manufactured by the direct mixing of sulphuric acid and ammonia, or as a by product of refinery or caprolactum manufacture.

3. Uses

SOA is a valuable fertiliser as a straight product or in blends.
Sulphur in SOA is sulphate sulphur which is the form taken up directly by plants. Sulphate sulphur is readily soluble in water and goes straight into solution when applied to the soil (providing there is moisture).

SOA releases nitrogen to the soil directly as ammonium NH4+, which is converted by bacteria to nitrate nitrogen. This process is favoured by conditions conducive to microbial activity, such as warm temperatures, moisture and organic matter. The rate of this reaction depends on those conditions and complete nitrification of applied ammonium can vary from a few days to several weeks.

4. Storage and handling

  • As with all nitrogen fertilisers, SOA is hygroscopic and so susceptible to absorbing moisture from the atmosphere.
  • Although it has lower moisture uptake qualities than Urea, care must be taken to minimise exposure to moisture. When stored in a bulk shed, ensure all adverse weather is excluded and preferably keep covered with plastic. When used in the field, all efforts must be made to avoid exposure to moist air. Keep trucks and spreaders covered, empty drills and air-seeders overnight or between jobs.
  • Of the nitrogen fertilisers, SOA has the most acidifying effect on the soil.

5. Restrictions

Do not store in silos.