The Nitrogen Cycle
The Nitrogen Cycle is the movement of nitrogen from plants, animals, bacteria, the atmosphere, and the soil on Earth. To be used by different processes, Nitrogen is stored in four different states: nitrates, nitrites, ammonium, and nitrogen. Nitrogen is key to living organisms because it helps make chlorophyll in plants. Plants use the chlorophyll in photosynthesis to produce their food and energy which gets transferred through the food pyramids. Nitrogen is also an important component of complex molecules such as amino acids and nucleotides. These complex molecules make up important proteins and DNA which become the building blocks of life.
Nitrogen is cycled through the environment in a number of processes. Most of the nitrogen on Earth is stored in the atmosphere, and is unable to be processed by most living organisms. Precipitation deposits nitrogen into soil and surface waters and combines with hydrogen atoms to form ammonia. Bacteria do most of the grunt work in the conversion through symbiotic relationships with plants, free anaerobic bacteria, and algae. A lesser amount of nitrogen is "fixed" into other parts of the cycle through high energy fixation in lightning strikes.
The next part of the cycle comes from the decomposition of manure, organic matter, and crop residue by microbes in ammonia. This process is called mineralization or decay. The ammonia from these several processes is converted to nitrate by microorganisms through nitrification. Plant absorption is the ultimate goal for farmers and can be the next step in the nitrogen cycle. The efficient amount of nitrogen depends on temperature, soil moisture, pest pressure, and soil compaction. However, not all nitrogen is taken up by plants and passed along other organisms.
There are a couple ways that nitrogen can be converted back to non-usable forms of nitrogen. Denitrification occurs when nitrogen is converted from nitrates into unusable gaseous forms of nitrogen. This happens when soil is saturated and the bacteria use nitrate as an oxygen source. Leaching is another process where usable nitrogen is lost. Since soil particles and nitrate are both negatively charged, nitrate can be easily moved by water running through the soil. Soil drainage, rainfall, amount of nitrate, and plant absorption can all have an effect on the amount of nitrate that ends up in water sources. This process is called leaching.
The major reservoir of nitrogen is the atmosphere. The atmosphere is comprised of 78% nitrogen gas. Other major storage places include organic matter in soil, the ocean, and in living organisms. Unfortunately, humans have been contributing to the disruption of the cycle. The major increase in nitrogen based fertilizers have increased the amount of nitrogen in groundwater that runs into streams, rivers, and lakes. Plant and animal populations can and will be altered by the changing amount of nitrogen levels. Also, the burning of forests and fossil fuel emissions have had effects on the amount of nitrogen in the air and can lead to acid rain. Finally, more livestock ranching creates more waste that enters the soil and the cycle.
Some interesting facts about the nitrogen cycle:
There are a couple ways that nitrogen can be converted back to non-usable forms of nitrogen. Denitrification occurs when nitrogen is converted from nitrates into unusable gaseous forms of nitrogen. This happens when soil is saturated and the bacteria use nitrate as an oxygen source. Leaching is another process where usable nitrogen is lost. Since soil particles and nitrate are both negatively charged, nitrate can be easily moved by water running through the soil. Soil drainage, rainfall, amount of nitrate, and plant absorption can all have an effect on the amount of nitrate that ends up in water sources. This process is called leaching.
The major reservoir of nitrogen is the atmosphere. The atmosphere is comprised of 78% nitrogen gas. Other major storage places include organic matter in soil, the ocean, and in living organisms. Unfortunately, humans have been contributing to the disruption of the cycle. The major increase in nitrogen based fertilizers have increased the amount of nitrogen in groundwater that runs into streams, rivers, and lakes. Plant and animal populations can and will be altered by the changing amount of nitrogen levels. Also, the burning of forests and fossil fuel emissions have had effects on the amount of nitrogen in the air and can lead to acid rain. Finally, more livestock ranching creates more waste that enters the soil and the cycle.
Some interesting facts about the nitrogen cycle:
- Nitrous oxide is a greenhouse gas - too much of it can cause acid rain
- Nitrogen has no color, odor, or taste
- Many explosives contain nitrogen
- Approximately 3% of one's body weight is nitrogen
- Nitrogen is responsible for the orange-red, blue-green, blue-violet, and deep violet colors of the aurora
You mentioned nitrogen fixation, but maybe you could put a short definition by it because I do not think everyone knows what it is. The definition from the environmental science course I took was pretty simple: Converting gaseous nitrogen to a usable form.
ReplyDelete