Ammonium sulfate

Ammonium sulfate is used on grain, forage and a number of perennial crops that need nitrogen in ammonium form and additional sulfur. It can be useful for farms working with crops sensitive to sulfur deficiency, as well as for nurseries, berry plantations and industrial plantings on soils where nutrition adjustment is needed. Before application it is advisable to take soil pH into account, because the fertilizer has an acidifying effect and this will not be an advantage for every crop.

The best time to apply this fertilizer to the soil is spring, before pre-sowing treatment, as well as the early tillering phase of winter crops. In autumn, ammonium sulfate can also be applied, but only on soils not prone to nitrate leaching. It is important to remember that the ammonium form of nitrogen is fixed by the soil complex and does not volatilise as quickly as the nitrate form. That is why it is spread in early spring, even on frozen-thawed soil, and moisture draws it into the root zone.

In practice, ammonium sulfate is used in spring to feed winter grain crops, sweet cherry, apple, black currant, roses, as well as vegetable crops — brassicas and nightshades. Landowners often ask what to feed with ammonium sulfate in spring when they see pale foliage and weak growth. In this situation it gives a fast nitrogen start while also supplying sulfur, which improves protein synthesis. Blueberries, rhododendrons and cranberries respond especially well to such spring application thanks to the mild acidification of the soil.

This salt can be identified by its appearance: a white or slightly coloured crystalline powder resembling coarse salt. To accurately identify ammonium sulfate, the crystals are dissolved in water and barium chloride is added — the appearance of a white barium sulfate precipitate confirms the presence of the sulfate ion. The ammonium part is revealed with a strong alkali solution: ammonia is released with a characteristic smell. In the laboratory, the question of how to identify ammonium sulfate quantitatively often arises, and the ammonia distillation method is used, but in field conditions qualitative reactions are sufficient.

It can be applied both dry, worked into the soil before watering or between rows, or as a solution for liquid feeding. The main thing ammonium sulfate provides is concentrated nitrogen in ammonium form and sulfur, necessary for amino acid synthesis. It is not mixed with alkaline substances, is not left on the surface without incorporation, and is used where sulfur is lacking. As a result, what this fertilizer gives is a strong increase in green mass, disease resistance and high grain protein content.

The shelf life of ammonium sulfate is usually 5 years from the date of production, but with basic storage conditions this period is practically unlimited. To keep ammonium sulfate for a long time, it is kept in a dry, ventilated room, in undamaged factory packaging. If the salt absorbs moisture, it may cake, but after drying and crushing it becomes usable again, since it is chemically stable.

Dissolving ammonium sulfate in water is quite simple: the crystals are poured into a container with warm liquid and stirred until clear. In practice, to properly dissolve the fertilizer for liquid feeding, 20–40 g per bucket of water is used. Usually there are no problems with dissolving ammonium sulfate in water, because its solubility is high (more than 70 g per 100 ml at 20°C). The main thing is not to use ice-cold water and to stir thoroughly, then there will be no residue.

Feeding with this fertilizer can be carried out once the average daily air temperature reaches around +5°C, when growth processes begin in winter crops and perennials. Ammonium nitrogen is absorbed gradually, and even during significant frosts the applied ammonium sulfate remains in the soil until warmth arrives. Root and foliar feeding, however, are best carried out on days when the temperature is above +10…+15°C, so that plant metabolism is active and the nutrients are quickly put to use.