Nitrogen

1. NITROGEN: An Essential Nutrient

* Nitrogen is an element that is essential for all living organisms.

Organisms need nitrogen to build important molecules, including proteins and DNA. Proteins are important because they help build body structures and allow cells to carry out many different functions and DNA includes the instructions for building proteins.

* Without nitrogen, living organisms could not grow, reproduce, or maintain healthy cells.

* About 78% of the atmosphere is nitrogen gas, written as N2. However, most organisms cannot use nitrogen gas directly from the atmosphere.

- The nitrogen atoms must first be changed into forms that plants and other

         organisms can use.

* The movement of nitrogen between the atmosphere, soil, water, and living

   organisms is called the nitrogen cycle.


2. NITROGEN CYCLE: Nitrogen Fixation

  • One of the first important steps in the nitrogen cycle is called nitrogen fixation.

  • During nitrogen fixation, atmospheric nitrogen gas is changed into forms of nitrogen that can be used by organisms.

  • Certain types of bacteria play an important role in nitrogen fixation.

  • Some of these bacteria live freely in soil, while others live in structures associated with the roots of certain plants, especially legumes such as beans and peas.

  • Once nitrogen has been changed (fixed) into a usable form, it becomes available to plants.


3.  Plants Take Up Nitrogen

  • Plants obtain nitrogen primarily from the soil through their roots.

  • Plants cannot simply absorb nitrogen gas from the atmosphere.

  • Instead, their roots take up nitrogen-containing compounds dissolved in soil water. Because plants are producers, they are an important connection between nitrogen in the soil and nitrogen in the food web.

  • When an animal eats a plant, nitrogen moves from the plant into the animal.

  • If one animal eats another animal, nitrogen moves again through the food web.

  • The nitrogen originally found in the soil can eventually become part of the tissues of several different organisms.

- For example: Nitogen could move in this food chain:

Soil → Plant → Rabbit → Fox


4. Decomposition Returns Nitrogen to the Environment

  • When plants and animals produce waste or die, their nitrogen-containing materials  are returned to the environment.

  • Decomposers, including bacteria and fungi, break down dead organisms and waste materials.

  • During decomposition, nitrogen is returned to the soil in forms that plants can use.

  • Part of this nitrogen in the soil can be returned to the atmosphere.

  • Some bacteria convert nitrogen in the soil to nitrogen gas to be returned to the atmosphere in a process called denitrification.

  • This is an important part of the nitrogen cycle because nutrients are recycled rather than being used only once.

  • The nitrogen cycle demonstrates an important idea in ecology: matter is recycled through ecosystems.


5.  Nitrogen and Water

  • Nitrogen can also move from soil into streams, rivers, lakes, and other bodies of water.

  • Rain can wash nitrogen-containing compounds from soil into waterways. This movement of nutrients from land into water is called runoff.

  • A small amount of nitrogen is necessary for healthy aquatic ecosystems.

  • Plants and algae need nutrients to grow. However, an excessive amount of nitrogen can create environmental problems.


6. Human Activities and Excess Nitrogen

  • Human activities can change the natural nitrogen cycle.

  • One major source of excess nitrogen is fertilizer, Farmers add nitrogen fertilizers to soil because crops need nitrogen to grow.

  • When fertilizer is used at an appropriate rate, it can improve plant growth and food production.

  • However, if more fertilizer is applied than. plants can use, the extra nitrogen may remain in the soil.

  • Rain can carry excess nitrogen from agricultural fields, lawns, and other areas into streams, rivers, lakes, and coastal waters.

  • This movement is called nutrient runoff


Other sources of Excess Nitrogen include:

1.) Animal manure: Animal waste and household wastewater contain nitrogen compounds. When large amounts of manure are placed on soil, rain can wash excess nitrogen into nearby streams, rivers, and lakes.

2.) Sewage and wastewater: Human waste and household wastewater contains nitrogen compounds. If wastewater is not properly treated, nitrogen can enter rivers, lakes, and coastal waters.

3.) Industrial activities: Some factories and industrial processes release nitrogen compounds into the air or water. These compounds can eventually enter soil and waterways.

4.) Burning fossil fuels: Cars, trucks, power plants, and factories burn fuels such as gasoline, coal, and natural gas. This releases nitrogen oxides into the atmosphere. These compounds can return to Earth in rain or other forms of deposition.