13.5 Environmental issues concerning the use of nitrogen-containing fertilisers

Question 1

What are the detrimental effects of using nitrogen-containing fertilisers

Answer 1

1. Reduced species diversity
2. Leaching
3. Eutrophication

Question 2

What is leaching

Answer 2

The process by which nutrients are removed from the soil

Question 3

What does rainwater do to soluble nutrients

Answer 3

Carry them deep into the soil, eventually beyond the reach of plant roots. These ions find their way into watercourses, and may have a harmful effect on humans

Question 4

What is Eutrophication

Answer 4

The process by which nutrient concentrations increase in bodies of water

Question 5

Describe the sequence of events that occur when eutrophication happens

Answer 5

1. In most watercourses there is a naturally low concentration of nitrate ions, so they are a limiting factor
2. As the nitrate concentration increases as a result of leaching, it stops being a limiting factor and algae population increases rapidly. Algal bloom occurs which prevents light penetrating to lower depths
3. Light becomes a limiting factor and plants at the lower depths die.
4. The lack of dead plants is no longer a limiting factor for saprobiotic bacteria and these grow dramatically.
5. Saprobiotic bacteria use oxygen to respire, oxygen quickly becomes a limiting factor and aerobic organisms die.
6. Without aerobic organisms, anaerobic organism populations rise -
7. Anaerobic organisms further decompose dead material, releasing more nitrates and some toxic wastes, making the water putrid

Question 6

How do nitrogen-containing fertilisers cause reduced species diversity

Answer 6

Nitrogen-rich soils favour grass growth and other rapidly growing species. These out-compete other species which die - reducing the species diversity