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The Nitrogen Cycle
Posted by: Admin on Thursday, November 03, 2005 - 12:26 AM
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Nitrogen is the most important nutrient in the growth of plants. A combination of natural and human processes is required to maintain nitrogen compounds in soil.
When we harvest crops we remove valuable nutrients from the soil. These nutrients need to be replaced in order to keep the soil fertile. Sustainable methods of food production are neeed to ensure that nutrients are replaced, and that food production can continue into the future.
The Nitrogen Cycle
( Environmental Protection Agency All EPA images are in the public domain.)
How can we get nitrogen into the soil?
Plants need nitrogen! However, a nitrogen molecule N2 cannot be absorbed directly by plants. However, they can absorb nitrogen in the form of nitrate compounds and ammonium compounds. A process called fixation enables nitrogen compounds to be formed.
Bacteria enable fixation to be achieved. In this process the nitrogen in the air is converted into nitrates. The bacteria reside in the roots of the plants.
Fertilizers, containing ammonium nitrates, can be added to the soil to increase the nitrogen levels. The use of fertilizers can increase the growth and yeld of crops by significant amounts. Many millions of people in the world depend on the use of fertilizers to provide their food. Fertilizers cost money, and many farmers around the world are unable to afford to buy them. Over-use of fertilizers can also result in damage to the coil, and also present environmental damage in rivers and streams by increasing bacterial levels.
How are nitrates cycled in nature?
There are a number of processes involved in the cycling of nitrates.
1. When plants absorb nitrates they use them to make proteins. Porteins are needed for growth
2. When animals eat plants the proteins are absorbed
3. The urine and faeces from animals are then broken down in the soil . This returns nitrates to the soil. This also happens when animals and plants die. Bacteria in the soil is essential for this process to happen.
4. Nitrates are easily dissolved in water, which allows hem to be distributed in the soil
How are nitrates removed from the soil?
There are a number of processes which remove nitrates from the soil
1. Certain types of bacteria in the soil will break down the nitrates
This releases nitrogen gas back into the atmosphere
2. Harvesting crops
3. Raising animals on the land
4. Rain can remove nitrates, in many cases the water enters streams and rivers.
Further information
http://en.wikipedia.org/wiki/Nitrogen_cycle
http://www.nps.gov/olym/hand/process/ncycle.htm
http://helios.bto.ed.ac.uk/bto/microbes/nitrogen.htm
http://www.bbc.co.uk/schools/gcsebitesize/sosteacher/biology/33968.shtml
http://www.nicksnowden.net/images/Nutrient_Cycles/nitrogen_cycle_fairly_cartoonish.jpg
http://www.soils.agri.umn.edu/academics/classes/soil2125/doc/s9chap2.htm
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