5.4 CHAPTER 5. THE CHEMICAL INDUSTRY
instead of in the aquaticsystem. Laws relating to the treatment and discharge of sewage
can also help to controleutrophication. A final possible intervention is nitrogen testing
and modelling. By assessing exactly how much fertiliser is needed by crops and other
plants, farmers can make sure that they only apply just enough fertiliser. This means
that there is no excess torun off into neighbouring streams during rain. There is also a
cost benefit for the farmer.
Activity: Dealing with the consequences of eutrophication
In many cases, the damage from eutrophicationis already done. In groups,
do the following:- List all the possible consequences of eutrophication that you can think of.
- Suggest ways to solvethe problems that arise because of eutrophication.
Exercise 5 - 6
Why we need fertilisersThere is likely to be a gap between food production and demand in several
parts of the world by 2020. Demand is influenced by population growth
and urbanisation, as well as income levels andchanges in dietary prefer-
ences.The facts are as follows:- There is an increasingworld population to feed
- Most soils in the worldused for large-scale, intensive production of
crops lack the necessarynutrients for the crops
Conclusion: Fertilisers are needed!The flow diagram below shows the main steps in the industrial preparation of two
important solid fertilisers.