DETERMINATION OF ORGANIC CARBON IN FOREST SOILS BY COMPARATIVE ANALYSIS OF METHODS: WALKLEY BLACK METHOD WITH THE GOGOASA MODIFICATION VERSUS DRY COMBUSTION DUMARS METHOD
E. M. Edu, M. Mihalache, Mariana IONESCU · Research Journal of Agricultural Science · 2013
The present work aims at comparative analysis the analytical methods used for determining organic carbon and total nitrogen in forest soil to assess the status of soil fertility through C/N ratio on the number of samples collected from different regions. In this article were studied 504 soil profile (1940 horizons), soil samples were collected from hills and mountains zone of Romania. The following parameters are analyzed: pH, organic C and total N. The pH was electrochemically determined in calcium chloride, organic carbon was determined by wet oxidation method and dosage titration - Walkley Black method with the Gogoasa modification and dry combustion Dumars method. Total nitrogen in the soil was determined by wet digestion method and dosage titration - Kjeldahl method and dry combustion Dumars method. The results were grouped on the following horizons categories: A, A/x, E, B. Analytical results shows that, given the differences in soil type with soil-specific soil characteristics and the method used in the determination. C/N ratio is different depending on soil type, distinct variance analysis shows significant differences when using Tru Spec CN analyzer. When applied wet mineralization, analysis of variance indicated for most samples analyzed very distinct significant influence of the type of soil C/N ratio. Organic carbon and total nitrogen shows a positive correlation with increasing altitude, because soils are high content in both elements. Dry combustion method using Tru Spec Leco CN analyzer is more efficient and faster time for a sample is 7 minutes allows the simultaneous analysis of carbon and total nitrogen in the soil sample being analyzed. On soils with carbonates, the analyzer is determined inorganic and organic carbon and thus is not necessary to still further analysis. Reaction forest soils are influenced by the distribution of the relief. Organic carbon content is in close contact with major bioclimatic zones: the mountain zone appears highest values, while values occur in the medium and low hill. Total nitrogen content is very close to the geographical distribution of carbon.