The Nitrogen Cycle.
The nitrogen cycle is when nitrogen in the atmosphere or in the soil goes through many complex chemical and biological changes is combined into living and non-living material, and returns back to the soil or air in a continuing cycle. In the soil, nitrogen changes from organic matter in the soil, to bacteria, to plants, and back to organic matter.
In fact, all animals, humans, and microorganisms on this earth are breathing nitrogen, because around 80% of our earth's atmosphere is comprised of nitrogen. The other 20% is oxygen.
Nitrogen is also used by our plants as nutrients for growing. Nitrogen is so vital because it is a major component of chlorophyll, the compound by which plants use sunlight energy to produce sugars from water and carbon dioxide (i.e., photosynthesis).
It is also a major component of amino acids, the building blocks of proteins. Therefore, we wouldn't have any food without nitrogen.
These all play into the nitrogen cycle, which is a biogeochemical process through which nitrogen moves from our atmosphere to our soils, to organisms, and then back, into the atmosphere.
Masri et al., 2022. This video, is part of a Powerpoint presented during the 11th International Drainage Symposium (SWCS- IDS-ASABE), August 30- September 2, 2022, at Marriott Des Moines Downtown, Iowa. https://youtu.be/oJpRh0hI5l8
Nitrogen gas cannot be used by most organisms. However, it can be converted into plant usable forms by certain bacteria, legume plants, or through industrial fertilizer production. This fixed nitrogen can then be absorbed by plants, and later by the animals who eat these plants to grow and thrive. Soil organisms and plants use it in their bodies just as we do. When these organisms die, nitrogen is released back into the soil, providing an opportunity for other plants and microorganisms to use it. Other soil bacteria feed on nitrogen, gaining energy by converting ammonium to nitrate the same way we gain energy from eating carbs. And a wide variety of soil bacteria can use nitrate in place of oxygen when oxygen isn't available, converting the nitrate to nitrogen gas, which is released back into the atmosphere, completing the nitrogen cycle.
Nitrogen is so important to agriculture that many farmers use nitrogen-rich fertilizers or plant legumes to spur growth in their crops. However, these fertilizers can cause damage to the environment in different ways:
If too much fertilizer is applied in ways that don't allow plants to use the nitrogen in the fertilizers, the extra nitrogen can easily move into the runoff water leaving the farm, and leaching in form of nitrate. Thus carrying the nitrate so deep into the soil that plants can no longer use them. This process leads to contaminated drinking water supplies, polluted rivers and surface water, and harmful algae blooms.
Volatilizing in the form of ammonia. Turns urea fertilizers and manures when applied on the soil surface and not incorporated into gases that also join the atmosphere.
Not all the nitrogen released back into the atmosphere is converted back to nitrogen gas. Some are converted to nitrous oxides by denitrification, a powerful greenhouse gas that traps heat and lingers in our atmosphere for a long time.
These processes account for most of the nitrogen lost to the cycle — a concern for soil fertility and water quality resources.
For the above three points, we have published refereed research and used innovative methods for the evaluation of the soil nitrogen mineralization cycle, (e.g., nitrification, denitrification, and immobilization) process.