Nitrogen Cycle

Nitrogen Cycle - C:N ratio of OM decreases with time and...

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1 1 Nutrient Cycling The Nitrogen Cycle Chapter 12 SS 121 2 N important because… • Amino acids Æ Proteins • Chlorophyll • Nucleic acids 3 Plants take up N as •NO 3 - •NH 4 + 4 N Cycle 5 N Cycle N fixation N 2 Æ organic-NH 2 – Industrial – Lightning – Most is microbiological Rhizobium , Azotobacter , Frankia , others – Takes much energy (or enzymes) to break N 2 triple bond 6 N mineralization = conversion of organic N to inorganic form Organic-NH 2 Æ NH 4 + • Carried out biologically by decomposers • Necessary for plant uptake 7 Nitrification NH 4 + Æ NO 2 - Æ NO 3 -
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2 Proceeds quickly in healthy soils Biochemical process, nitrifying bacteria Nitrosomonas NH 4 + Æ NO 2 - Nitrobacter NO 2 - Æ NO 3 - 8 Denitrification – Loss of nitrogen by reduction and volatilization NO 3 - Æ N 2 O or N 2 • Microbiological • Saturated conditions (wetlands, highly irrigated soils) 9 Immobilization • By microorganisms • High C:N ratio
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Unformatted text preview: C:N ratio of OM decreases with time and decomposition 10 Ammonia volatilization Loss of N in form of ammonia gas NH 4 + + OH- NH 3 (g) + H 2 11 Ammonium fixation NH 4 + becomes fixed in certain layer silicate minerals related to cation exchange Weathered micas, vermiculite Mineral must weather again to release ammonium 3 12 Nitrate leaching Because NO 3-not retained on CE complex Eutrophication 13 Runoff NH 4 + enters surface waters Attached to soil particles Fertilizer particles Eutrophication 14 Eutrophication Nutrients (such as N, P) added to surface waters in higher-than-natural quantities excessive growth or "blooms" of algae algal blooms to oxygen depletion fish kills 15 Eutrophic lakes...
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Nitrogen Cycle - C:N ratio of OM decreases with time and...

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