What is Nitrogen Fixation?
Green plants require several important elements in order to make their food and carry out the various life sustaining processes they need to survive. One of these important elements is Nitrogen which happens to be the most abundant element in the earth’s atmosphere. However, the nitrogen in the atmosphere is not useful to plants in its naturally occurring state. It requires processing to convert it into a form that the plants can readily absorb through their roots. Ammonia is one of the more common modified forms of nitrogen that plants absorb from the soil. The process by which atmospheric nitrogen is converted into compounds such as ammonia that plants can readily use is known as nitrogen fixation.
Just as the term suggests, nitrogen fixation involves the fixing of nitrogen into the soil. There are two primary classes of agents that are involved in the process of nitrogen fixation. The first agents are independent living micro organisms that absorb the atmospheric nitrogen and release it into the soil in the form of waste. These micro organisms which are different kinds of bacteria are able to process the nitrogen into forms such as ammonia which plants can absorb and use. Organic matter that is decaying releases various nitrogen compounds in the soil and these are also useful to plants as they are able to absorb them directly through their roots. Some kinds of independent bacteria that are useful in the conversion of atmospheric nitrogen include Azotobacter, Desulfovibrio and Green sulphur bacteria.
The other nitrogen fixing agents are found in the roots of leguminous plants such as beans, peas and clover. The roots of these plants have nodules which contain the bacteria that convert the atmospheric nitrogen into compounds which plants can use. This is a symbiotic arrangement where the plants and bacteria benefit from one another. Leguminous plants are thus an important agent of nitrogen fixation and contribute significantly to the nitrogen compounds available in the soil for plants to use. This is why farmers intercrop legumes with other crops or have them in their crop rotation programs. This ensures that there is adequate supply of nitrogen compounds in the soil. It also goes to show that solutions to some of the needs arising in nature can actually be found in nature.
Nitrogen fixation is therefore a biological and chemical process that is critical for life. By feeding plants, the process is by extension feeding the world since plants are the primary source of food. It is also part of the nitrogen cycle which is the process where nitrogen is absorbed from the atmosphere and used by living things and finally released back to the atmosphere. Natural nitrogen fixation is an important process since it accounts for two thirds of the nitrogen used by plants. All other processes including industrial production account for only a third of nitrogen compounds consumed by plants. Nitrogen fixing bacteria are found in all kind of soil conditions including deserts and swamps where they continuously supply plants with the all important nitrogen compounds they need.