Time-temperature Effect on Soil-borne Pathogens

The adoption of a model using thermal death kinetics parameters for a selected soil born pathogen (Fusarium oxysporum f. sp. basilici) has been proposed to predict the pathogen reduction and to design the best treatment duration and temperature during soil steam disinfestation. Models have been identified and validated using experimental data. The scope was to control the steam treatment avoiding energy consumption and negative side-effects on soil quality due to overheating. In fact, during soil steaming, in some cases, even during the same treatment (e.g. surface application) some soil layers are both heated and cooled very rapidly (surface layers), while the internal layers follow different heat transfer dynamics which are slower in heating, but the cooling phase is longer and even starts after the stop of the steam supply. The risk to control the treatment considering only the temperature at one depth is to heat more than required to pasteurize all the soil slab, loosing energy, or to fail in soil disinfestation. As the contribution of each time temperature interval could be different for microorganism with different death kinetic parameters, the same methodology could be adopted to evaluate the pasteurizing effect on some selected soil-borne pathogens potentially dangerous in horticultural contexts.