HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kassim, G. Articles by Haider, K. Search for Related Content PubMed Articles by Kassim, G. Articles by Haider, K. Agricola Articles by Kassim, G. Articles by Haider, K.

Incorporation of a Wide Variety of Organic Substrate Carbons into Soil Biomass as Estimated by the Fumigation Procedure¹

ABSTRACT

Biodegradation of the carbon or specific carbons of a large variety of ¹⁴C-labeled organic substrates were followed in a closed, constantly aerated system in Steinbeck loam (pH 5.0) and Greenfield sandy loam (pH 7.0) over various periods of incubation at 22°C. Incorporation into biomass and stabilization in humus were estimated after 12 weeks of incubation. The labeled carbons in biomass were estimated using a slight modification of Jenkinson's fumigation method. Readily available substrates such as glucose, acetate, pyruvate, uracil, uridine, amino acids, and some polysaccharides were rapidly metabolized by the soil population, and after 8 to 12 weeks, about 80% or more of the substrate carbons had evolved as CO₂. After 12 weeks, about 20 to 40% of the residual carbons of these substrates were present as hiomass, and 60 to 80% was present as new humus. Glucosamine, cysteine, cellulose, protein, and some microbial and plant polysaccharides were degraded to a somewhat smaller extend, 60 to 70%, indicating some stabilization of the intact molecules or partial degradation products by incorporation into humus or by complexing with soil colloids or metals. About 10 to 30% of the residual carbons were associated with the biomass after 12 weeks. Most microbial cells and plant residues such as straw were utilized to a still lesser extent, with about 50 to 60% loss of applied C in 12 weeks and an incorporation of about 5 to 13% of the residual ¹⁴C into biomass. A fungal humic acid-type melanin was still more resistant, and less of the residual C, 0.2 to 1.3%, was present in biomass at 12 weeks.

¹ Contribution from Dep. of Soil and Environmental Sciences, Univ. of Calif., Riverside, Ca 92521, and from Institut für Pflanzenernährung und Bodenkunde, Braunschweig, Germany.

² Former Graduate Student and Professor of Soil Sci., Univ. of Calif., Riverside; and Biochemist, Institute für Pflanzenernährung und Bodenkunde, Braunschweig, Germany. Present address of G. Kassim is Dep. of Soil Science, Mosul University, Haman al-Alil, Mosul, Iraq.

Received for publication April 6, 1981. Accepted for publication July 28, 1981.