The Carbon Cycle
Carbon is an element that is in almost everything on Earth, and the Carbon cycle shows us where it is, and how it got there.
During photosynthesis, plants use sunlight to turn carbon dioxide(CO2) into oxygen. The carbon from the CO2 then goes to make glucose, or sugar, for the plant. At night, when there is no sunlight, plants do something called cellular respiration. During this process, they take oxygen from the air, and turn it back into CO2 using glucose. This is a small part of the Carbon cycle. Carbon from decomposing plants goes into the soil where fossils and fossil fuels are formed. Cars and factories emit CO2 into the atmosphere. Animals and humans breath in oxygen and exhale CO2 which also goes into the atmosphere. The ocean absorbs some carbon from the air and from soils. Carbon is everywhere in our world and it's important for us to understand it's travels in order to take care of our Earth. |
The Nitrogen Cycle
The Nitrogen cycle is infinitely more complex than the Carbon cycle. Nitrogen, like Carbon, is everywhere in our world. But it comes in so many forms that the process is incredibly complicated.
Nitrogen gas(N2) makes up about 78% of our atmosphere. In order to enter the soil, however, the two Nitrogen atoms must be split apart. There are two main ways that this can happen; lightening has the ability to split the atoms apart, or some plants, such as legumes, can absorb N2 and return it to the soil. This is called Fixation. Mineralization, the decaying of organisms above and in the soil, can return the Nitrogen to the soil. Mineralization returns Nitrogen in the forms of either ammonium or nitrates, both of which can be used by plants. |
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Within the soil, Nitrogen can form many different compounds: ammonium, nitrates, and nitrides. Denitrificatin is the process of changing nitrides(NO2) into nitrates(NO3) which can be used by plants.
Nitrates can be lost at the surface by turning back into Nitrogen gas; this is called volatization. The nitrate and nitride molecules can soak into rivers, streams, and groundwater if there is excess in the soil. When this happens, it's called leeching. |