Submitted to: The Global Farm Selected Papers from the International Soil Conservation Or
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 18, 2002
Publication Date: July 1, 2002
Interpretive Summary: Loss of water stable aggregates due to excessive tillage has increased the potential for soil erosion in semi-arid farming-systems. Fungi can be responsible for the resistance of soil aggregates to breakdown upon wetting. We studied the effects of a saprophytic lignin decomposer basidiomycete isolated from plant litter on soil aggregation and stabilization. The Basidiomycete produces large quantities of non water-soluble extracellular materials that bind soil particles into aggregates. Water stability of aggregates amended with the fungal mycelia and the degree of biodegradation of the binding agents by native soil microorganisms was determined by the wet sieving method. Data demonstrated that fungal amended aggregates supplemented with a source of carbon (millet or lentil straw) were much more water stable and resisted microbial degradation longer that when they were prepared with fungal homogenates alone.
Technical Abstract: The objective of this study was to determine the role a saprophytic lignin decomposing basidiomycete isolated from plant residues in forming and stabilizing artificial soil aggregates, 1-2 mm in size composed of soil particles < 0.25mm. Our study demonstrated that a saprophytic lignin decomposing basidiomycete has the ability to efficiently bind and stabilize soil particles into water stable aggregates. This is because this fungus secretes large amounts of water insoluble extracellular compounds that act as binding agents of soil particles. Our results showed that addition of growing mycelia in sterile soil which contain sterile artificial fungal-amended aggregates previously autoclaved, provoked a considerable increase in aggregate stability. The amount of WSA recovered was almost triple that of the controls after 2 weeks of incubation, suggesting that the fungus alone bound more soil particles. The possible relationship of the role of basidiomycetes in litter decomposition and soil aggregation is discussed.