Types of Biogeochemical CycleThe biogeochemical cycle is crucial for every living organism on Earth. It is strongly influenced by life forms, including plants and microorganisms. A biogeochemical cycle can be defined as a continuous pathway by which the conversion and circulation of chemical nutrients through the biotic and abiotic compartments of the Earth (Butcher, 1992). Generally, biogeochemical cycles can be classified into three broad categories: the nitrogen cycle, the sulfur cycle and the carbon cycle (see Figure 1 in Annex 1). The first type of biogeochemical cycle is the nitrogen cycle. Nitrogen is an abundant and chemically inert gas, which makes up about 78% of the atmosphere. According to Stevenson and Cole (1999), accumulation in soil occurs by microbial nitrogen fixation in the presence of ammonia, nitrate and nitrite; depletion occurs in the process of crop removal, leaching and volatilization. In terms of this, the process of releasing the compound during decomposition is called mineralization. The mineralization process is carried out by microorganisms in which it releases carbon, as well as ammonium (Sprent, 1987). As a result, many types of organic nitrogen reduce the nitrogen present, such as urea, organic bases, such as purines and pyrimidines, and amino compounds. Animals have nitrogen waste and will eventually produce a lot of nitrogen (Sprent, 1987). Several pathways are illustrated throughout the nitrogen cycle, such as nitrogen fixation, ammonification, nitrification, and denitrification. Gates (1921) stated that the process of converting nitrogen gas to ammonia or ammonium is nitrogen fixation, while ammonium can also be produced by the decomposition of a nitrogenous organic substance, called ammonification . After...... middle of paper ...... but slow absorption of carbon dioxide from the atmosphere (Zepp and Sonntag, 1995). Hanson, Ducklow and Field (2000) mention that in the ocean, part of the carbon is absorbed by phytoplankton to make calcium carbonate shells which settle to the sea floor to form sediments. In the geological carbon cycle, carbonic acid combines with magnesium and calcium present in the Earth's crust to form insoluble carbonates. Carbon dioxide reacts with certain minerals to form limestone, then dissolves in rainwater and is carried to the oceans. Once there, it can precipitate out of the ocean water and form a layer of sediment on the seafloor. Limestone melts and reacts with other minerals under high heat and pressure far below the Earth's surface, releasing carbon dioxide. The carbon dioxide is then returned to the atmosphere through volcanic eruptions (Lockwood and Hazlett)., 2010).