How to use ammonium sulfate as a fertilizer

In conventional agriculture, ammonium sulfate is still widely used, especially for less profitable crops and as an important source of nitrogen accompanied by sulfur, a precursor in its assimilation.

The ammonium form is rapidly assimilated by crops, although in large volumes it can become phytotoxic for the plant. In fact, in hydroponics, its use is limited to a maximum of 15-20% of the total nitrogen fraction, the remaining 80-85% being nitric nitrogen.

However, controlling the dose and the application in all types of soil crops, ammonium sulfate is a very good source of contribution of this element, being easy to mix and use.

In this article we want to highlight the possibilities that this fertilizer has in current agriculture, how to use it, properties and doses in all types of crops.

As an introduction, comment that ammonium sulfate is not an ecological fertilizer, since its process is obtained by synthetic transformations and, therefore, is not included in the European regulations for organic farming.


Ammonium sulfate is not just a fertilizer used in agriculture. This industrial component is also used as a flocculant . One of the great properties of amines and all nitrogen-rich compounds is that they facilitate the mixing of different components.

This is the case of urea , which can be mixed with fuel (AdBlue) to optimize the mixture and increase combustion efficiency.

In this case, when we have an acid solution, the incorporation of a small amount of ammonium sulfate purifies it, leaving it clear and transparent.

For example, in the presence of proteins, this additive is capable of separating soluble proteins (eg globulins) from red blood cells.


All the nitrogen in this fertilizer is in ammonia form . Although it is highly assimilable by the plant, it is preferable to absorb it in nitric form.

In the soil, its behavior is good, since because it has a positive charge, it remains fixed in the clay-humic complex and does not leach as much to deep fields (as the nitric form does).

However, the presence of nitrifying microorganisms (nitrobacter and nitrosomonas, among others), facilitates its transformation to nitric. In summer, increased temperatures in the soil can transform this nitrogen in a few days.

As it has an acid reaction , it is used to acidify soils with alkaline pH and a high presence of non-soluble calcium and magnesium. In addition, the sulfur incorporated in the fertilizer improves the availability of nitrogen and acts synergistically in its assimilation.


  • 21%p/p nitrógeno amoniacal
  • 60% p/p azufre (SO3)

Chemical formula

The chemical formula of ammonium sulfate is (NH 4 ) 2 SO 4

The presence of sulfur and ammonium crystals makes the final color of the product white.

CAS No.: 7783-20-2

Actual Price

Ammonium sulfate presented in 25 kg bags has a price between € 0.2 / kg and € 0.25 / kg.

For each fertilizer unit contributed (1 UFN), its cost is € 1 or € 1.19

Solubility and  pH

  • Solubility:  dependent on temperature.
    • 70,6 g/100 mL (0 °C)
    • 74,4 g/100 mL (20 °C)
    • 103,8 g/100 mL (100 °C)
  • pH:  when we solubilize this fertilizer, due to the buffer capacity of ammonia, the pH is usually between 5 and 7.

However, that the pH of the fertilizer is that does not mean that, once applied, it is conserved. In fact, the reaction of this element in the soil is acidic, hence its use is recommended in alkaline soils with a high content of limestone, to facilitate its assimilation by the plant.

  • Relative density: 1.77 g / cc


Obtaining ammonium sulfate as an industrial product is the transformation of gaseous ammonia (NH3), mixed with steam water to create a saturation and the incorporation of sulfuric acid.

This controlled reaction is transformed into the mixture of sulfur (SO4) and ammonium (NH4), which, because it is attacked with an acid, adds one more hydrogen (H) to the formula.

Read more:  use of sulfur in agriculture



The solubility of this fertilizer is quite high, although less than other more common fertilizers such as ammonium nitrate. There are cases in which the farmer prefers to work with liquid formulas already solubilized of ammonium sulfate.

A concentrated formula would be to dilute up to 40% of the fertilizer, achieving a nitrogen concentration of 8.4% w / w and sulfur (SO3) of 24% w / p


One of the best known and most used formulas, presented the fertilizer in solid but powder form, easily soluble.

It is used when preparing liquid solutions, to be directly applied in fertigation.

Being highly soluble, this fertilizer must always be provided as a cover , that is, when we already have crops planted.


Granulated ammonium sulfate is slowly soluble and is used in pre-sowing or in tree crops, when it is not possible to incorporate water through fertigation (period of rains or puddles).

It contains the same richness as any other formula, and its contribution is quite common in crops such as almond, olive or fruit trees, especially at the time of sprouting and development of new leaves.

Read more: the great importance of nitrogen for plants


  • Technical data sheet type
  • Safety data sheet type


Ammonium sulfate is not a fertilizer that should be applied in large quantities, since it is not very efficient in terms of supplying nitrogen. That is, the current role is to serve as a support along with other supplies of quick-release nitrogen.

This is due to the fact that the transformation from the ammonia form to the nitric form , although it is rapid, has an environmental extra cost. And it is that an average soil with organic matter and relatively normal presence of microorganisms, the gaseous loss of ammonia (the cleaning product that we use at home) is 30%.

That is to say, of 100% of the transformation of nitrogen to nitric form, 30% does it in gaseous form to the environment.


For this reason, it is increasingly common to incorporate nitrification inhibitors , such as dicyandiamide (DCD) or DMPP, which act to prevent the development of nitrifying microorganisms and keep nitrogen in its initial form for a longer time.

Read more: the importance of nitrification inhibitors


Horticultural crops:  applied in fertigation, from 1 to 1.5 kg / 1000 m of surface and irrigation.

Tree crops:  in dry land, crops such as almond or olive grove, apply 2 to 3 kg / foot of granulated and slowly soluble formula in a cover.


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