Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/1999
Publication Date: N/A
Citation: Caesar, T., Cochran, V.L. 2000. Soil aggregate stabilization by a saprophytic lignin-decomposing basidiomycete fungus. I. microbiological aspects. Biology and Fertility of Soils. 32(5):374-380. Interpretive Summary: Dryland soils of the Great Plains have lost an estimated of 50% of organic matter. The decline of organic matter has been accompanied by a loss of water stable aggregates and a greater propensity to erode. We investigated the role of a soil fungus isolated from soil litter in Easter Montana for its ability to produce extracellular materials that act as soil binding agents and to form persistent water stable soil aggregates. This fungus fr fungi that include mushrooms capable of degrading plant materials. It can b easily mass-produced in the laboratory and the binding capacity of the fungus is not reduced at high temperature. We demonstrated that artificial fungal amended aggregates were significantly more resistant to degradation by microbes and maintain their integrity much longer when they were supplemented with a source of carbon (millet or lentil straw) than fungal amended aggregates without supplements. Our results support the idea that water stable aggregates conserve organic matter or nutrients from plant residues in a form protected from rapid microbial decomposition. The possible role of fungi that degrade plant materials to aggregate soil in plant residues has been totally neglected. Since under natural conditions much of the available plant materials is converted to humus, clarification of the interactions which occur between this class of fungi in the soil environment is important in agriculture. .
Technical Abstract: Since saprophytes are of great importance in lignin decomposition from plan residues to its incorporation into soil organic matter, we studied the effe of a saprophytic lignin decomposer basidiomycete isolated from plant litter soil aggregation and stabilization. The basidiomycete produces large quantities of extracellular materials that bind soil particles into aggregates. These binding agents are water insoluble and heat resistant. Wa stability of aggregates amended with the fungus and the degree of biodegradation of the binding agents by native soil microorganisms were determined by the wet sieving method. Data demonstrated that aggregates supplemented with a source of carbon (millet or lentil straw) were much mor water stable and resisted microbial decomposition longer than when they wer prepared with fungal homogenates alone. Moreover, retrieval of fungal-amen naggregates supplemented with millet during the first 4 weeks of incubation natural soil exhibited more large aggregate fractions (>2 mm) than the ones supplemented with lentil straw. The possible relationship of the role of basidiomycetes in litter decomposition and soil aggregation is discussed.