Fertilisers

Background, how we make them and the good and the bad

Overview of Fertliser

Fertilisers contain soluable nitrogen compounds which are used by plants to make proteins. When added to plants soil they premote fast and strong growth in plants. Manure can be natual or artifical.

How long they've been around

Fertilisers have been used by farmers to aid plant nutrition for thousands of years. John Bennet Lawes was one of the first scientists to begin experimenting with the effects of manure on plant growth.


Industrial nitrogen based fertiliser was developed by Kristian Birkeland in 1903, nitrogen is placed in the fertiliser as the plants absorb the nitrate ions. The reaction used to produce this nitrogen based fertiliser was HNO3 → H+ + NO3-.

The Haber Process

The raw materials used in the haber process are hydrogen and nitogen. The hydrogen gas is obtained by reacting methene with steam and the nitrogen is obtained through the burning of hydrogen.

The nitrogen and hydrogen will react together under these conditions:

- At a very high temperature (400 degrees)

- Under very high pressure (200 times normal pressure)

- An iron catalyst is used.


When nitrogen and hydrogen are reacted together ammonia is formed. Ammonia is used in fertilisers. The reaction of nitrogen + hydrogen ammonia can work both backwards and forwards. This means that nitrogena and hydrogen can be reacted together to form ammonia and ammonia can be broken up into hydrogen and hydrogen.

Advantages and Disadvantages

Advantages

Use of artifical fertilisers means that farmers can grown more crops faster and more effiecently. This extra growth means that more people can be fed.

Disadvantages

Fertlisers contain large amounts of nurtients so when they enter the soil and water supply they can cause eutrophication. This process causes plants and algae in streams and lakes to grow very quickly. These overgrown plants then prevent sunlight from penetrating the water. When all the overgrown plants die they are decomposed by bacteria that then use up all the oxygen in the water. This lack of oxygen and sunlight cuases the organisms in the pond/lake/river to die out.