Abstract
Saprotrophic fungi are abundant in soils of (semi-)natural ecosystems, where they play a major role in ecosystem functioning. On the contrary, saprotrophic fungal biomass is remarkably low in intensively managed soils and this can have a negative impact on soil functioning. Nevertheless, arable soils harbour a diverse pool of fungi, which can be stimulated by organic amendments. Management targeted towards increasing soil organic matter often coincides with an increase of fungal biomass, but it can take years before effects are seen. However, a rapid stimulation of fungal biomass at the start of the growing season could immediately benefit crop production, by improving nutrient availability, soil structure and suppression of soil-borne diseases. The objective of this study is to realize a rapid increase of saprotrophic fungal biomass with organic amendments. In controlled pot experiments, dried and milled organic materials of different quality were added to an arable sandy soil. Ergosterol-based fungal biomass and ITS2-based fungal community structure were measured over a period of two months. Wood sawdust of deciduous tree species and paper pulp resulted in a high and lasting increase of fungal biomass, as opposed to transient effects given by cover crops and other non-woody plant materials. Little or no stimulation of fungi was seen for coniferous wood sawdust and agro-industrial by-products. Nitrogen immobilization induced by sawdust and paper pulp was compensated by supplementing mineral nitrogen, which enhanced the stimulation of saprotrophic fungi. The composition of the stimulated fungi was influenced by the quality of organic amendments. In particular, deciduous wood sawdust and paper pulp favoured saprotrophic ascomycete fungi (mainly Sordariomycetes), with no increment in potential plant-pathogenic fungi. Overall, our results point at a good perspective to use woody materials as sustainable soil improver via stimulation of saprotrophic fungi.
Highlights
Saprotrophic fungi represent an important component of soil microbial life in many terrestrial ecosystems
This study shows that paper pulp and wood sawdust of deciduous tree species rapidly and consistently increase fungal biomass in arable fungal-poor soils, over a time-frame of two months
We showed that elevated nitrogen did not inhibit, but rather enhanced fungal biomass stimulation by fresh, high C:N materials
Summary
Saprotrophic fungi represent an important component of soil microbial life in many terrestrial ecosystems. In contrast to many soils in natural ecosystems, saprotrophic fungal biomass is remarkably low in arable soils, in particular in intensively managed arable land (Djajakirana et al, 1996; van der Wal et al, 2006a; de Vries and Bardgett, 2012). This is ascribed to the application of chemical pesticides, mineral fertilizers and intensive tillage (DuahYentumi and Johnson, 1986; Beare et al, 1997; Frey et al, 1999; Bittman et al, 2005; Scotti et al, 2015). When arable soils are taken out of production, fungal biomass and activity increase and are followed by Abbreviations: ITS2, ribosomal internal transcribed spacer region 2; CRBD, completely randomized block design; ANOVA, analysis of variance; PERMANOVA, permutational analysis of variance; OM, organic matter
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