General properties of nitrogen atoms found in the periodic table
Nitrogen is a gas. It has no colour, smell or taste, and will neither burn by itself nor help other substance to burn. For the fact that a substance seems so lifeless, nitrogen play a vital part in the life of all living things. Nitrogen gas make up rather more than three quarter of the air we breathe, most of the rest been oxygen. When combine with other substance nitrogen form compound. This compound may be nitro compound such as nitrate ammonia or ammonium salt, or protein such as nucleic acids and other organic compounds found in the living things. Plant and animal use nitrogen but they cannot obtain the nitrogen they need simply by breathing in the air containing it nor can plant take a nitrogen through their leave the way they take in carbon dioxide.
What happened is that plant get their nitrogen from the soil in the form of nitrate and use it in the production of protein and other nitrogen containing organic compound. Animals eat the plant and convert the nitrogen compound into substance require for their own growth, and renewal or repair. Animals cannot store excess nitrogen compounds, so this are broken down and expel from the body in the animal waste matter or droppings.
Farmer collect the dropping in a manual heap which is spread over the land to give the nitrogen back to the soil. If the plant are not eating they die and rot and bacteria and fungi change the nitrogen containing compound in in them back into nitrate once again. Thus nitrogen from the soil possess to plant and animals and back to the soil again this is called nitrogen cycle.
There are some loss in the nitrogen cycle. The greatest loss is caused by returning only a part of the treated human waste matter to the land. Some of the loss are made up by the actions of certain bacteria found in leguminous plant such as beans pears clover and alfalfa. This bacteria live in swelling called nodules on the root of the plant. The bacteria take nitrogen from the air in the soil and change it into nitrate which are taken up by the plants. this is called nitrogen fixation.
More important the bacteria produce more nitrate than the plants need and thus enrich the soil. so farmer sometimes grow clover or another leguminous crop and plough it into the soil. This is called green manuring.
More often they spread the soil with natural manure (dung leaf mould or seaweed )or artificial one( nitrate or ammonium compound). A certain amount of nitrogen is added to the soil when I energy bolt of lighting enforce atmospheric nitrogen and oxygen to combine forming simple compound that dissolves in water and thus fall to the ground.
Sources: children britannica volume 13.
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