Page 43 - Curriculum Visions Dynamic Book

Sulphate fertilisers
Sulphates are soluble in water. This is important for plants because they need to take up their nutrients through their roots using water in the soil. Those nutrients most needed by plants to make their tissues are potassium, nitrogen and phosphorus. Sulphates are thus used as a cheap “vehicle” to carry sulphur and the other main nutrients that the plants need.
A fertiliser is produced by reacting a suitable source
of potassium, nitrogen or phosphorus with sulphuric acid. About two-thirds of all the sulphuric acid made goes into the production of fertilisers.
Most fertilisers contain one or more of ammonium sulphate (nitrogen), calcium phosphate (which contains phosphorus), and sulphate of potash (potassium sulphate).
One of the best known fertilisers is called superphosphate (a combination of ammonium sulphate and phosphate), first produced by scientist John Lawes in 1843. To make it, sulphuric acid is poured over phosphate rock, producing phosphoric acid. Ammonia gas and sulphuric acid are also reacted to produce ammonium sulphate. The two fertilisers are then mixed to make superphosphate.
pesticide: any chemical that is designed to control pests (unwanted organisms) that are harmful to plants or animals.
preservative: a substance that prevents the natural organic decay processes from occurring. Many substances
can be used safely for this purpose, including sulphites and nitrogen gas.
sulphate: a compound that includes sulphur and oxygen, for example, calcium sulphate or gypsum.
sulphide: a sulphur compound that contains no oxygen.
sulphite: a sulphur compound that contains less oxygen than a sulphate.
Energy for life
Many different organisms use sulphur instead of oxygen to oxidise their energy supplies. Among the most common are bacteria. This is why bacteria and blue–green algae are able to live in places with very little oxygen. The vastness of the deep ocean waters is one example; the areas near geysers and volcanoes are another.
Whereas green plants give off oxygen, organisms that live in oxygen-poor water give off sulphur as part of their living processes. These organisms get all the energy they need by fermenting dead tissue using sulphur-containing compounds.
Also...
In recent years farmers near industrial regions have noticed that their yields
of cereals have declined almost in proportion to the rate at which sulphur has been removed from the smokestacks of power stations. This is because plants have been using the sulphur in the acid rain as a fertiliser. Now acid rain has been reduced, farmers are having to increase their applications of sulphate fertilisers in order to maintain their yields!
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