Biological soil disinfestation : a safe and effective approach for controlling soilborne pests and diseases

Biological soil disinfestation (bsd) is an environmentally friendly method to disinfest the soil from soilborne fungi and nematodes. With biological soil disinfestation a green manure crop (40 tonnes per ha) or other green biomass is homogeneously incorporated into the soil layer that has to be disinfested. Then the field is lightly compacted and irrigated. Subsequently, the soil is covered with a plastic film to restrict oxygen supply. The soil is left covered for six to ten weeks in summer. After covering the soil, anaerobic conditions develop which last for several weeks. Under these conditions toxic fermentation products are formed. In a three-year trial at Meterik on a loamy sand biological soil disinfestation was applied in two ways during the first year. After the green manure was rotary tilled through the soil two different plastic types were applied at different fields. The first plastic type was the standard ensilage polyethylene sheet of 0.12 mm thickness (Hermetix). The second type was a thin three-layer film of polyethylene and polyamide, 0.035 mm thick with a very low methyl bromide and oxygen permeability (VIF; Hytibarrier). The Hermetix plastic reduced Verticillium dahliae contamination of the soil from 2.0 and 1.6 microsclerotia for the control treatments to 0.5 microsclerotia.g-1 soil. The Hytibarrier plastic fields decreased the contamination even further to hardly detectable levels. Also the number of Pratylenchus penetrans nematodes seemed to be lower in the Hytibarrier fields even at the end of the growing season. This pathogen inactivation led to a marked decrease of stunted and wilted plants and a 5.7-fold increase in yield compared to untreated. With biological soil disinfestation the level of pathogen inactivation is similar to that of inundation, soil solarisation and steaming. In contrast to some of these methods, bsd does not result in an accelerated recolonisation of the soil by the pathogen. Furthermore, its effect seems more reproducible and is larger than that of biofumigation with glucosinolate containing crops. As bsd may be used also in cold and wet climates, where soil solarisation is not effective, this method is a real alternative to methyl bromide fumigation.