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Management of soil suppressiveness against soil-borne diseases

Lucius Tamm: Research Institute of Organic Agriculture FiBL

<div>Soils suppressive to soil-borne diseases have attracted the attention of farmers and researchers for decades and many suppressive soils have been described. Microorganisms and soil microbial communities involved in suppressiveness have been studied intensively, but the underlying mechanisms are still not well understood. Suppressiveness to soil- as well as air-borne diseases has been shown to be highly site-specific. We will review how suppressiveness can be influenced by agricultural practices. Suppressiveness destroyed e.g. by steam sterilisation of soils could only be partially restored on the short-term by re-inoculation of soils, and the success of re-inoculation depended on the soil matrix as well as on the inoculum used. Long-term management (e.g. conventional or organic management), tillage regime, and short- or long-term fertility inputs have the potential to alter soil suppressiveness, yet the effect of a particular practice is still difficult to predict. Application of biocontrol organisms such as Pseudomonads or <em>Bacillus</em> sp. can have a beneficial effect against particular diseases on the short-term, but they can rarely persist after introduction in natural soils. Application of suitable composts can often help to sanitize fields contaminated with soil-borne pathogens more efficiently than individual biocontrol organisms. An ongoing study tries to identify key microbial consortia responsible for the beneficial effect of composts to allow a targeted application.</div>