| Positives of nitrogen-containing fertilisers | - Essential component of biological molecules such as proteins + is needed for growth
- This increases rate of photosynthesis
- Improve crop productivity
- Cheaper food |
| Negatives of nitrogen-containing fertilisers | - Reduced species diversity
- Leaching, which may lead to pollution of watercourses
- Eutrophication, caused by leaching of fertiliser into watercourses |
| Reduced species diversity | - Because nitroglycerin-rich soil favour the growth of grasses, nettles and other rapidly growing species
- These out-compete many other species, which die as a result |
| Leaching | - Process by which nutrients are removed from the soil
- Rainwater dissolves soluble nutrients, like nitrate ions, + carry them deep into the soil
- The leached nitrate ions find their way into watercourses, like streams, rivers, lakes
- They may have harmful effect on humans if river or lake is source of drinking water
- High conc. of nitrate ions in water can prevent efficient oxygen transport in babies + link to stomach cancer
- They can cause eutrophication |
| Eutrophication | - Process where nutrients increase in concentration in bodies of water |
| Eutrophication process (1) | - Mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds and rivers (algal bloom)
- Nitrate ion con. become limiting factor for growth
- Large amounts of algae block light from reaching the plants below |
| Eutrophication process (2) | - Light becomes limiting factor for growth
- Eventually the plants die because they're unable to photosynthesise enough
- Saprobiontic bacteria feed on the dead plant matter |
| Eutrophication process (3) | - The increased numbers of bacteria reduce the O2 conc. in the water by carrying out aerobic respiration
- O2 becomes limiting factor for growth
- Fish + other aquatic organisms die because there isn't enough dissolved O2 |
