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Revista de Ciências Agrárias
versión impresa ISSN 0871-018X
Resumen
DIAS, R.M.S.; SEMPITERNO, C.M. y FARROPAS, L.. Influence of soil grinding degree on the determination of total nitrogen, total carbon and organic carbon concentrations.. Rev. de Ciências Agrárias [online]. 2010, vol.33, n.1, pp.88-95. ISSN 0871-018X.
According to ISO Standard 11464 (Soil quality -Pretreatment of samples for physicochemical analyses) for test samples below 2 g, the air dried soil sample must be ground to a particle diameter ≤ 0.25 mm, in order to have a homogeneous test sample and, therefore, minimize the variability of results. This is quite a time consuming task. The aim of this study was to compare the influence of two different degrees of grinding (<2mm and < 0.15 mm) on the determination of total nitrogen, total carbon and organic carbon, with test samples of 0,5 g. These elements were analyzed in 7 different soils from Continental Portugal, derived from different parent material. Five representative samples were taken from each soil and manually crushed to pass a 2 mm plastic sieve. Each sample was then split in two portions: in one of them, nitrogen and carbon were analyzed directly on the fine earth fraction (< 2 mm); on the other portion, the analyses were carried out only after grinding the soil sample on a agate mill till it just passed a plastic sieve of < 0.15 mm. Total nitrogen and carbon were determined by dry combustion on a CNS elemental analyzer, according to ISO Standards 13878 and 10694, respectively. Organic carbon was determined indirectly after correction of the total carbon content for the carbonates present in the soil sample. Results suggest that the soil grinding degree had no significant (p>0.05) effect on C and N concentrations. Grinding the soil to 0.15 mm didnt increase significantly (p>0.05) the precision of results suggesting that, for the determination of total nitrogen or total and organic carbon, it is not necessary to grind the soil to a fraction less than 2 mm.
Palabras clave : carbon; ISO Standard 11464; nitrogen; soil analysis; soil grinding.