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Unformatted text preview: Nitrogen and Sulfur Immobilization is the incorporation of inorganic-N into organic compounds. When the C / N ratio is high, immobilization > mineralization. Nitrogen Influence of N on Plant Growth and Development NH 4 + Fixation Entrapment of NH 4 + between adjacent tetrahedral sheets of neighboring layers of 2:1 minerals. The tendency for fixation follows the sequence, vermiculite > illite > smectites. Fixed NH 4 + is slowly released. N is taken up as NH 4 + or NO 3- . It is essential as a component of many different biomolecules such as proteins, nucleic acids and chlorophyll. Deficiency results in chlorosis and poor growth. However, oversupply causes rank but abnormal growth and poor quality. NH 3 Volatilization NH 4 + + OH- H 2 O + NH 3 Conditions favoring Opposing volatilization volatilization ___________________________________ High pH Low pH Low CEC High CEC Surface application Incorporation in soil Dry soil Moist soil High temperature Cool temperature Nitrification Microbial oxidation of NH 4 + Origin and Distribution of Nitrogen 2NH 4 + + 3O 2 2NO 2- + 4H + + 2H 2 O + E 2NO 2- + O 2 2NO 3 + + E Most N is atmospheric. There is 10 to 20 x as much N in soil as in vegetative cover. Most soil N is in organic combinations and N comprises about 5 % of soil organic matter. Only about 1 or 2 % of the soil N is inorganic. Nitrification is carried out by autotrophic bacteria Step 1 Nitrosomonas Step 2 Nitrobacter Immobilization and Mineralization Clearly, nitrification acidifies soil....
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This note was uploaded on 01/08/2012 for the course AGRO 2051 taught by Professor Gaston during the Fall '08 term at LSU.
- Fall '08