A method to determine soil DNA and RNA.

A method for determining soil RNA and DNA concentrations after their extraction from soil is described. The determination was carried out with colorimetric methods specific for the sugar moiety of the nucleic acids. Various extraction procedures were tested when nucleic acids were added to soil either as pure reagents or as internal standards. A procedure involving three extraction steps gave the highest yields. Soil samples were extracted twice with 0.5 N HC104, neutralized with 2 n NaOH and the extraction continued after the addition of 0.1 m Na4P2O4 at pH 7.2. In the third step the soil sediment was extracted with 0.1 m Na4P2O7 at pH 7.2. Low molecular weight ribose and deoxyribose-containing compounds were separated from the nucleic acids on the basis of their solubility characteristics in the acid medium of the supernatant obtained after the first extraction step. Approximate recoveries of organic P in the nucleic acids were found to range from 3.2 to 6.5% of the total soil organic P. Nucleic acid-N ranged from 2.0 to 4.0% of the total N. The organic C content of the soils used was lower than 2% but when soils richer in organic matter are used, extracted humic molecules are likely to interfere during the colorimetric determination.