Describe the Nitrogen Cycle
The balance of processes which put nitrogen into the air and processes which remove nitrogen from the air is called the nitrogen cycle.
Nitrogen is an important element in proteins. Some plants have nodules on their roots which contain nitrogen fixing bacteria. These bacteria convert atmospheric nitrogen (nitrogen gas in the air) into nitrogen compounds. This process is called nitrogen-fixation. From these nitrogen compounds, the plants can synthesize proteins. Plants of the legume family have these nitrogen-fixing bacteria in nodules on their roots.
Plants which are not legumes synthesize protein from nitrates.
How do the nitrates get into the soil?
Nitrogen and oxygen come together in the atmosphere during lightning storms and in the engines of motor vehicles during combustion. They form nitrogen oxides (compounds of nitrogen and oxygen). These gases react with water to nitric acid. Rain showers brings nitric acid out of the atmosphere and wash it into the ground, where it reacts with minerals to form nitrates. This is another instance of nitrogen-fixation. Plants take in these nitrates through their roots. They use them to make (synthesize) proteins. Animals obtain the protein they need by eating plants or by eating the flesh of other animals.
In the excreta of animals and the decay products of animals and plants, ammonium salts are present. Nitrifying bacteria in the soil convert ammonium salts into nitrates. Both nitrates and ammonium salts can be removed from the soil by denitrifying bacteria, which convert the compounds into nitrogen.
To make the soil more fertile, farmers add both nitrates and ammonium salts as fertilizers.
The balance of processes which put nitrogen into the air and processes which remove nitrogen from the air is called the nitrogen cycle.
Draw the Nitrogen Cycle
NITROGEN CYCLE
Explain Nitrification and Denitrification
Nitrification
The conversion of ammonium to nitrates by bacteria living in soil is known as Nitrification.
Denitrification
The reduction of nitrates back into nitrogen gas (N2) through the action of soil micro-organisms is called denitrification.
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