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8/3/2019 Nutrient.cycle Group3

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Group 3 January 30, 2012

The Nutrient Cycle

All of the life on earth revolves around a few key nutrients and in combination with

energy form the sun, these nutrients are essentially contained within a closed system on earth,

which means no nutrients enter or leave the biosphere in large quantities. For this reason there is

a limited amount of the essential nutrients available to the producers, so the available nutrients

such as carbon, nitrogen and phosphorus must be recycled and reused by organisms. The

recycling of these nutrients involves the relations between both the living organisms and the

physical environment, so they are called biogeochemical cycles. There are cycles under the

nutrient cycle that are highly important to all life on earth namely the water cycle, the carbon

cycle, the nitrogen cycle, and the phosphorus cycle.

Basically, nutrients are the fuels of life. Nutrients are chemical elements that all plants

and animals require for growth. Nutrients that are used in large amounts are the non-mineral

elements for example carbon (C), hydrogen (H), and oxygen (O). But these elements are not

sufficient for the existence of life. Hence, elements like nitrogen (N), phosphorus (P), potassium

(K), calcium (Ca) and magnesium (Mg) are very important, particularly for the growth of plantsand agriculture. As mentioned earlier, the nutrient cycle has four important cycles that are very

essential to all life on earth, first is the constant movement of water from earth to the atmosphere

is called the water cycle. Earth has a stable water supply which ninety-eight percent of the

earths water is contained in oceans, lakes, rivers, and streams including those that are in a form

of ice, water vapor, and in the bodies of living organisms. Evaporation drives the water cycle for

it is the primary mechanism supporting the surface to atmosphere portion of the water cycle. The

amount of water evaporating is about the same as the amount of water delivered to earth as

precipitation. Second is the process of respiration that converts the carbon containing compounds

into carbon dioxide and water is called the carbon cycle. Its primary photosynthesizes are plants,

phytoplankton, marine algae, and cyan bacteria. Third cycle is one of the most essential elements

on earth which is nitrogen. The nitrogen cycle has three principal stages namely ammonification,

nitrification and assimilation. Ammonification also known as nitrogen mineralization occurs


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when soil dwelling saprophytic bacteria decompose dead organic matter, which are composed of

complex nitrogen containing compounds such as proteins and amino acids, and nucleic acids

these bacteria use the nitrogen they obtain to create their own amino acids and proteins and

release the excess nitrogen as ammonium which can then be used by plants. On the other hand,

nitrification occurs when bacteria oxidize ammonia or ammonium ions, this chemical reaction

produces energy, which the bacteria use to convert carbon dioxide into nitrite, hydrogen, and

water. Since the nitrite produced by the bacteria is toxic to plants it must be converted to nitrate

by another species of bacteria, once converted to nitrate, the nitrogen is available for absorption

by plants. Lastly, the assimilation of inorganic nitrogen in the form of ammonium or nitrate into

organic compounds such as proteins, amino acids and nucleic acids is one of the most important

processes on earth and is almost equal to photosynthesis and respiration. The greatest source of

nitrogen to crop plants is in the form of nitrate, which is broken-down and reduced to ammonia,

which can be quickly incorporated into organic compounds like amino acids. Although most

plants receive their nitrogen in an inorganic form like nitrate some plants in the artic, where

nitrogen availability is limited, are able to utilize organic nitrogen from dead organisms, these

specialized plants are able to do so without going through the process of ammonification. To

finish, the last cycle is the phosphorus cycle. Phosphorus that plants use is contained mostly in

the earths crust rather than in the atmosphere, this phosphorus is released with the weathering of

rock caused by wind, water and geologic uplift. Essentially, all nutrients that plants and also

human beings require to survive are cycled in this way.

At this time, humans played a big role on influencing the nutrient cycle in such a way that

we remove nutrients from the land and discharge them into aquatic environments. For example

the harvesting of crops, nutrients are removed from the soil. By the use of animal manure or

dung as fertilizers, nutrients are restored back to the soil. Other factors contributes to the

influence of the nutrient cycle particularly in agriculture because it accelerates land erosion in

ways of ploughing and tilling that disturbs and expose soil, more nutrients drains away because

of runoff. In addition, human induced alterations in the nutrient cycle leads to an imbalance in

the availability of nutrients. However, there should be a new approach in the management of

nutrients in order to sustain the stability and the balance of nutrients and to avoid its future

consequences.


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References:

http://en.wikipedia.org/wiki/Nutrient_cycle http://www.wisegeek.com/what-is-the-nutrient-cycle.htm http://www.sswm.info/category/concept/nutrient-cycle http://library.thinkquest.org/C007506/cycles.html

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