DETERMINATION OF ORGANIC CARBON IN FOREST SOILS BY COMPARATIVE ANALYSIS OF METHODS: WALKLEY BLACK METHOD WITH THE GOGOASA MODIFICATION VERSUS DRY COMBUSTION DUMARS METHOD PUBLISHED

Elena Mihaela EDU, M. MIHALACHE, Monica IONESCU
The present work aims at comparative analysis the analytical methods used for determiningorganic carbon and total nitrogen in forest soil to assess the status of soil fertility through C/N ratio onthe number of samples collected from different regions. In this article were studied 504 soil profile (1940horizons), soil samples were collected from hills and mountains zone of Romania. The followingparameters are analyzed: pH, organic C and total N. The pH was electrochemically determined incalcium chloride, organic carbon was determined by wet oxidation method and dosage titration - WalkleyBlack method with the Gogoasa modification and dry combustion Dumars method. Total nitrogen in thesoil was determined by wet digestion method and dosage titration - Kjeldahl method and dry combustionDumars method. The results were grouped on the following horizons categories: A, A/x, E, B. Analyticalresults shows that, given the differences in soil type with soil-specific soil characteristics and the methodused in the determination. C/N ratio is different depending on soil type, distinct variance analysis showssignificant differences when using Tru Spec CN analyzer. When applied wet mineralization, analysis ofvariance indicated for most samples analyzed very distinct significant influence of the type of soil C/Nratio. Organic carbon and total nitrogen shows a positive correlation with increasing altitude, becausesoils are high content in both elements. Dry combustion method using Tru Spec Leco CN analyzer is moreefficient and faster time for a sample is 7 minutes allows the simultaneous analysis of carbon and totalnitrogen in the soil sample being analyzed. On soils with carbonates, the analyzer is determinedinorganic and organic carbon and thus is not necessary to still further analysis. Reaction forest soils areinfluenced by the distribution of the relief. Organic carbon content is in close contact with majorbioclimatic zones: the mountain zone appears highest values, while values occur in the medium and lowhill. Total nitrogen content is very close to the geographical distribution of carbon.
organic carbon, total nitrogen, forest soil, C/N ratio
Presentation: oral

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