Distribution of organic matter and adenosine triphosphate after fractionation of soils by physical procedures

• Published in: Soil biology & biochemistry Vol. 16; no. 5; pp. 465 - 470
• Main Authors: Ahmed, M., Oades, J.M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1984; New York, NY Elsevier Science
• Subjects: adenosine triphosphate; Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; clay soils; fractionation; Fundamental and applied biological sciences. Psychology; methodology; microorganisms; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; soil organic matter; soil physics; Soil science; soil separates; Soil; Composition; Organic matter; ATP; Physical method
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(84)90053-1

A mildly leached soil and a calcareous clay soil were dispersed using ultrasound. In the mildly leached soil, organic carbon, nitrogen and ATP (which was used as a guide of the soil microbial biomass) were concentrated in the finer fractions. In the calcareous clay, organic carbon and nitrogen were concentrated in the silt fraction. When slurries of the same soils were shaken vigourously in a wrist action shaker the soils were more completely dispersed but the recovery of ATP was only 30% compared with 90% after ultrasonic dispersion. It is concluded that the vigorous shaking of a soil slurry is destructive with respect to the biomass and smears cell contents, including ATP, across the colloidal fractions. The use of 14C showed that organisms, and metabolic products after incubation of [ 14C]glucose, existed mainly in larger aggregates (> 250 μm dia), silt and clay sized materials. Following physical dispersion the 14C shifted to silt and clay fractions. It is concluded that while fine clay may be a source of the metabolic products of organisms, the silt fraction a source of cells, and macroorganic matter contains most of the plant debris, the association of microorganisms with inorganic colloids is such that “clean” fractionations of biological components in soils cannot be realized.