NUCLEIC ACID BASES IN SOILS AND THEIR ASSOCIATION WITH ORGANIC AND INORGANIC SOIL COMPONENTS

Abstract

Purines and pyrimidines were determined by ion-exclusion chromatography in 15 soil samples of widely differing pedological origins and in humic fractions isolated from these soils. The nucleic acid bases tended to concentrate in humins and fulvic acids (FA) rather than in humic acids. N in purines and pyrimidines constituted up to 7.4% of the soil-N and up to 18.6% of the N in a FA. The distribution of nucleic acid bases in soils and humic fractions was similar. Guanine, cytosine and adenine were detected in all samples, and thymine in most, while uracil and 5-methyl cytosine were found less frequently. The predominance of guanine and cytosine suggested a microbial DNA origin for the nucleic acid bases. Evidence was obtained that the nucleic acid bases interacted not only with humic materials but also with inorganic soil components such as clays and hydrous oxides. Our data show that purines and pyrimidines accounted for up to 16% of the unidentified N in a soil and for up to 40% of the N in a FA so far not yet identified. This suggests that more attention be given to nucleic acid bases when considering the N status of soils.