COMPARISON OF 2 CHEMICAL METHODS OF ASSESSING POTENTIALLY AVAILABLE ORGANIC NITROGEN IN SOILS

Two chemical methods (Phosphate Borate Buffer and 2M KCl methods) of assessing potentially available organic N in soils were evaluated using some infertile upland soils from Thailand. Their results were, highly correlated with those of the waterlogged incubation method which is considered to be one of the best laboratory methods for assessment of potentially available organic N in soils. While the data obtained support the findings of Gianello and Bremner (4) that the two methods provide good indexes of potentially available soil organic N, it appeared that their precision was affected by the low fertility status of the experimental soils. Of the two chemical methods evaluated, the 2M KCl method was found to be the most suitable for the experimental soils.