Human influence on the nitrogen cycle Energy in Ecosystems

The last lesson was about the nitrogen cycle. Re-cap The last lesson was about the nitrogen cycle. What do organisms use nitrogen for? How do animals get their nitrogen? How do plants get their nitrogen? Which types of decomposers are responsible for releasing nitrogen from dead organisms? Which type of organisms convert ammonium compound to nitrates? Energy in Ecosystems

Today we are learning about: How humans can influence the nitrogen cycle Success criteria Be able to explain how and why humans influence the levels of nitrogen in the cycle Energy in Ecosystems

Human influence on the nitrogen cycle Humans influence the nitrogen cycle particularly in relation to their farming activities. Harvesting crops removes nitrogen locked up in the crops that could have gone back into the soil. How do farmers put the nitrogen back into the soil? Energy in Ecosystems

Growing crops like clover Did you get all of these? Adding fertiliser Adding manure Adding compost Growing crops like clover Fertilisers are (man made) chemicals used to add a variety of essential minerals including nitrogen, phosphorus and potassium to the soil. This why fertiliser bags are labelled N:P:K Energy in Ecosystems

The N:P:K balance can be altered to provide to provide the correct mineral balance for the crops being grown. For root crops a high proportion of P For leaf crops a high proportion of N For flower and fruit crops a high proportion of K Energy in Ecosystems

Manure or compost which are natural fertilisers can also be added to the soil by farmers which adds nitrates as it decomposes. Growing crops like clover (legumes) will return nitrogen because they have root nodules with bacteria that fix nitrogen into nitrates. The clover is ploughed back in to the soil before a new crop is planted. Increasing the nitrates (and other minerals) will increase the yield in the crops being grown. Energy in Ecosystems

Excessive use of fertilisers Farmers can apply more fertilisers or manure than the crops can use. These excess nitrates can end up in fresh water like rivers, reservoirs and loch as run-off when it rains. This can cause an increase in the growth of algae in the water (algal blooms) which can block out light. Energy in Ecosystems

Excessive use of fertilisers As the algae die they sink to the bottom and decay. This decay uses up a lot of oxygen that is in the water. This lowers the oxygen level and increases the deaths of other organisms in the water like invertebrates and fish. This means the water will support less life so it reduces the biodiversity. Energy in Ecosystems

Human influence on the nitrogen cycle Before you leave you need to write down on your exit ticket answers to the following. 3 ways humans add nitrogen to the cycle What can happen to the excess nitrogen added? Why this could be negative for the environment? Let the teacher see your exit ticket. Energy in Ecosystems