Nitrogen makes up 78 percent of the earth's atmosphere and is essential to healthy plant growth. Without it, green plants are weak and smaller than they should be. Too much nitrogen, on the other hand, makes plants unable to withstand frosts or heavy winds. While many chemical fertilizers contain nitrogen, there are also natural sources of the element that do not put the environment at as much risk for pollution.
Identification
The letter N is the scientific symbol for nitrogen. An ingredient found in every amino acid, nitrogen is key to both plant and animal life on earth. Certain plants, especially legumes, are able to process nitrogen from the atmosphere and fix it in the soil where it can be utilized by other plants. The decay of organic material, clay deposits, as well as ammonium and nitrate compounds are the other ways that soil can become nitrogen rich.
Function
The nitrogen cycle transforms organic matter and animal manure into usable nitrogen. The entire cycle happens in the soil. Earthworms, bacteria and decay break down the proteins in the organic matter, assisting it to decompose. Ammonia compounds, mixtures of nitrogen and hydrogen, form. Next, these compounds become nitrates, which are then consumed by nitrobacteria called azotobactors. Azotobactors produce soluble nitrates, which can be used by plants.
Considerations
Legumes have rhizobium bacteria in their root nodules. These bacteria are able to take nitrogen directly from the atmosphere and fix it into the soil. An acre of alfalfa, for example, is able to fix 251 pounds of nitrogen from the atmosphere into the soil. Some soluble nitrates also enter the soil after atmospheric nitrogen reacts with rain water.
Warning
Nitrogen is a significant ingredient in chemical fertilizers used by farmers to enrich soils. If, however, too much nitrogen gets into the soil, three problems are possible. First, cattle grazing on the land can get nitrate poisoning even though animals do not eat plants that are too rich in nitrates. Second, the groundwater and nearby rivers and streams may become polluted. Third, the production of ethylene in the soil may be reduced. Ethylene causes fruits to ripen.
Expert Insight
Natural sources of nitrogen include rabbit droppings, cottonseed meal, feather meal and legumes. Organic farmers choose these options to enrich their soil because they do not pollute like chemical fertilizers can. They also have the benefit releasing nitrogen slowly.
