13.5 Environmental conditions concerning use of nitrogen containing fertilisers

Question 1

How does using nitrogen containing fertilisers reduce species diversity

Answer 1

. Nitrogen rich soils favour the growth of grass, nettles and other rapidly growing species
. These may outcompete others which will die as a result.

Species rich hay meadows only survive when soil nitrogen concentrations are low enough to allow other species to compete with the grasses

Question 2

How does use of nitrogen containing fertilisers contribute to leaching

Answer 2

. Process where nutrients are removed from soil
. Rainwater will dissolve soluble nutrients eg nitrate ions and carry them deep into the soil eventually far below the roots of the plant

. These leached nitrate ions make their way to watercourses eg streams and rivers that drain into lakes

Question 3

How is leaching harmful to humans

Answer 3

. If river or lake is a source of drinking water for them:

. High nitrate ion concentrations are very harmful to babies
. Also nitrate ions are linked to stomach cancer

Question 4

What is eutrophication

Answer 4

. Nutrient concentrations increase in bodies of water , so nutrients are no longer limiting factor for plant growth

. So Upper layers of water become densely populated with algae, called algae bloom

. This dense layer absorbs light and prevents it from penetrating to lower depths

. So plants underwater can’t photosynthesise so will die

. So saprobiontic bacteria use these dead organisms as food and population grows

. They respire aerobically so concentration of it in water is reduced

. So aerobic organisms such as fish can’t respire aerobically so die

. Less competition for anaerobic organisms so their populations rise and they can further decompose dead material