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Types of Biogeochemical Cycle Biogeochemical cycle is crucial for every living organism on Earth. It is strongly influenced by life forms, especially plants and microorganisms. A biogeochemical cycle can be defined as a continuous pathway by which conversion and circulation of chemical nutrients through both biotic and abiotic compartments of Earth (Butcher, 1992). Generally, biogeochemical cycles can be classified into three major categories which are nitrogen cycle, sulfur cycle and carbon cycle (Refer to Figure 1 in Appendix 1). First type of biogeochemical cycle is nitrogen cycle. Nitrogen is abundant and chemically inert gases, constitutes of about 78% of the atmosphere. According to Stevenson and Cole (1999), accumulation in soil happens through microbial fixation of nitrogen in the presence of ammonia, nitrate and nitrite; depletion exists in the process of crop removal, leaching and volatilization. In term of that, the process of releasing compound during decomposition is called mineralization. Mineralization process is carried out by the microorganisms in which it releases carbon, and also ammonium (Sprent, 1987). As a result, many kinds of organic reduce nitrogen present, like urea, organic bases, such as purines and pyrimidines, and amino compounds. Animals have nitrogenous wastes and will eventually produce lots of nitrogen (Sprent, 1987). Several pathways are illustrated throughout the nitrogen cycle, such as nitrogen fixation, ammonification, nitrification and denitrification. Gates (1921) state d that the process of converted gaseous nitrogen into ammonia or ammonium is nitrogen fixation, while ammonium can also be produced through the decaying of nitrogenous organic substance, which is called ammonification. Afte... ...ut slowly uptake of carbon dioxide from the atmosphere (Zepp, & Sonntag, 1995). Hanson, Ducklow and Field (2000) mention that in the ocean, some of the carbon taken up by phytoplankton in order to make shells of calcium carbonate that settles to the bottom of the sea to form sediments. In geological carbon cycle, carbonic acid combines with magnesium and calcium in the Earth's crust to form insoluble carbonates. Carbon dioxide reacts with some minerals to form limestone, then dissolves by rainwater and carries to the oceans. Once there, it can precipitate out of the ocean water and form layer of sediments on the sea floor. The limestone melts and reacts with other minerals under high heat and pressure far below the Earth's surface by releasing carbon dioxide. The carbon dioxide is then back into the atmosphere through volcanic eruptions (Lockwood, & Hazlett, 2010).