Soil nitrogen fractions as influenced by sample preparation and extraction

Abstract

In order to evaluate the influence of extraction procedure on extractable nitrogen (N) fractions, fresh as well as dried soil samples were extracted with CaCl₂ at various temperatures (20,40,60, 80°C) for 30–120 minutes. Data obtained were compared with those from the electro‐ultra‐filtration (EUF) method. Increasing the drying temperature as well as the extraction temperature led to an increase in N_org content. The EUF and CaCl₂‐method produced comparable results for all N‐fractions (NO₃ ^‐, NH₄ ⁺, N_org) when an extraction temperature of 80°C was applied for two hours. Data presented suggested that the N_org fraction represented mainly the microbial biomass and may thus be considered as being easily available to plants.