Summary
14C-labelled substrates were incubated at 20°C in 4 soils with clay contents ranging from 6 to 34%. Glucose was most readily decomposed, followed in order by hemicellulose, cellulose, maize straw, and barley straw. After the first 10 days of incubation, about 60% of the glucose-C had left the soils as CO2, compared with only 23% of the barley-C.
The humified matter that remained in the soils after 3 months decayed at almost the same rate whether the origin of the matter was glucose, hemicellulose, cellulose or straw; this rate was, on the whole, independent of the caly content of the soils. Half-life values for the labelled C in the soils during the second and third year of incubation ranged from 5 to 7 years. The amino acid-C percentages of the humified matter tended in all four soils to be largest in matter originating from glucose and least in that originating from straw. The amino acid-C percentages increased with the clay content of the soils.
The biomass was determined by fumigation with CHCl3 according to Jenkinson. After 3 months an average of 17% of the residual labelled C was in biomass; the values ranged from 37% when the labelled C was added as glucose to 2–9% when added as barley straw. The half-life of labelled C in biomass during the second year of incubation ranged from 2 to 3 years.
Native C in biomass ranged from 0.5 to 1.4% of the total C in native soil organic matter, the highest values occurring in the clay-rich soils. The half-life of native soil C, estimated from CO2 evolution during 3-month periods, ranged from 13 to 29 years.
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Sørensen, L.H. Size and persistence of the microbial biomass formed during the humification of glucose, hemicellulose, cellulose, and straw in soils containing different amounts of clay. Plant Soil 75, 121–130 (1983). https://doi.org/10.1007/BF02178619
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DOI: https://doi.org/10.1007/BF02178619