مقايسه سينتيك تجزيه آمينو اسيدها در خاك به كمك سنجش معدني شدن كرين و نيتروژن

چكيده انگليسي :

71 A Kinetic Approach to Evaluate Amino Acid Decomposition by C and N Mineralization Assays Najmeh Salari Bardsiri ns 64925@yahoo com Date of submission October 24 2010 Department of Soil Science Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiF Nourbakhsh Assoc Prof Supervisor Farshid@cc iut ac irAbstractNitrogen is the essential element of proteins peptids aminoacids nucleic acids chitin and peptidoglycans It is alsoa macronutrient for plants which its uptake is relatively greater than other essential elements Soil aminoacidscontain both C and N and therefore can be considered as a source of the elements for soil microbial population anda link between C and N cycles in soils The aminoacid decomposition can be studied either by C or Nmineralization Carbon and nitrogen mineralization is functionally related and both are derived by soil microbialactivities More than 95 of total soil N is in organic form and aminoacids comprise between 20 to 40 of soilorganic N These compounds are relatively easily decomposable and are subjected to rapid depletion from soilswhen the environmental conditions are favorable A comparative study was conducted to investigate the C and Nmineralization in soils received aminoacids as sources of C and N For this purpose different concentrations 0 10 20 40 60 and 100 mM of L glutamine L asparagine L histidine L arginine and glysine were applied to twoLavark and Shervedan soils with three replications The mineralized C and N were measured during 6 and 24 h respectively To study the C mineralization kinetic the carbon dioxide respired was measured at the concentrationcorresponds to the greatest C mineralization N mineralization was also measured in aminoacid treated soils as thesoils werec applied with a 50 mM aminoacid concentration Results indicated that both C and N mineralization wasenhanced by aminoacid application regardless of the aminoacid type The optimum concentration was different intwo soils In Lavark soil the greatest C mineralization rate for glucose was 100 mM whereas the concentration forL glutamine L histidine glysine and L arginine was 20 mM The C mineralization rate in L asparagine applied soilwas equal in 20 and 40 mM The concentration for L histidine In Shervedan soil the optimum concentration forglucose L glutamine L histidine was 60 mM while the concentration for glysine and L arginine was 20 mM Theconcentration for L asparagine was eqally evaluated at 20 and 40 mM A first order kinetic model was observed forC mineralization The greatest C mineralization rate was observed at 15 to 60 min after aminoacid application thenit was increased decreasingly In both soils different aminoacids induced various kinetic constants The greatest Nmineralization rate was observed at 24 h following aminoacid application followed by an either constant ordecreasing rates Moreover the greatest N mineralization rate was observed at 100 mM Overall L arginine inducedgreater amounts of N mineralization and no significant relationship was observed between C and N mineralizedfollowing application of the aminoacids The non significant association between C and N mineralization rates inaminocid applied soils has not been reported elsewhere and therfore can not be compared with other researches However it can be hypothesized that in the short period of incubation both C and N mineralization is mostlygoverned by intracellular activities The previous results has been reported on the plant residues and organicfertilizers which is basically different with pure aminoacids The most important different is due to the extracellularmechanism of protein breakdown prior to aminoacid decomposition when soils are applied with plant residues andorganic fertilizers Keywords Protein aminoacid C and N mineralization

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مقايسه سينتيك تجزيه آمينو اسيدها در خاك به كمك سنجش معدني شدن كرين و نيتروژن

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