Frequent Applications of Organic Matter to Agricultural Soil Increase Fungistasis

Soil-borne plant pathogens are among the most important limiting factors for the productivity of agro-ecosystems. Fungistasis is the natural capability of soils to inhibit the germination and growth of soil-borne fungi in the presence of optimal abiotic conditions. The objective of this study was to assess the effects of different soil managements, in terms of soil amendment types and frequency of application, on fungistasis. For this purpose, a microcosm experiment was performed by conditioning a soil with frequent applications of organic matter with contrasting biochemical quality (i. e., glucose, alfalfa straw and wheat straw). Thereafter, the fungistasis response was assessed on four fungi (Aspergillus niger, Botrytis cinerea, Pyrenochaeta lycopersici and Trichoderma harzianum). Conditioned soils were characterized by measuring microbial activity (soil respiration) and functional diversity using the BIOLOG EcoPlatesTM method. Results showed that irrespective of the fungal species and amendment types, frequent applications of organic matter reduced fungistasis relief and shortened the time required for fungistasis restoration. The frequent addition of easily decomposable organic compounds enhanced soil respiration and its specific catabolic capabilities. This study demonstrated that frequent applications of organic matter affected soil fungistasis likely as a result of higher microbial activity and functional diversity.