Physical methods for soil disinfestation in intensive agriculture: Old methods and new approaches

Physical soil disinfestation is worldwide mainly applied in protected cropping systems or in small-scale intensive field crops. Continuous cropping of monocultures or different host plants for the same pest or pathogen often leads to heavily infested soils which forces growers to disinfest the soil thoroughly. The oldest method is steam sterilization which is applied for more than a century. In the 1970s hot water treatment of soils was developed in Japan. Hot water is applied to the soil surface to raise soil temperatures to lethal levels. Since the 1980s inundation became a new method in the Netherlands and is applied in bulb cultures. This so-called flooding of soils creates anaerobic soil conditions in which toxic compounds like greenhouse gases are produced. A new approach in soil disinfestation in the current century is hot air treatment which is developed in Israel. The method is based on blowing extremely hot air into soil particles which are thrown above soil surface into a heat chamber by a rotary spading device. In the Netherlands renewed interest has started in radiation of soil with micro waves. Radiation of soil or other substrates has been studied for decades. The mechanism is that the heat produced by radiation is lethal to pathogens and pests. Anaerobic soil disinfestation (ASD) with incorporation of fresh organic matter in soil is a method developed in the Netherlands. A new and promising Dutch development in ASD is the application of defined products. Advantages and disadvantages of all methods are presented in this paper

Perspectives of Anaerobic Soil Disinfestation

Biological soil disinfestation is an environmentally friendly method to disinfest soil. From now on we refer to it as anaerobic soil disinfestation (ASD). With ASD a green manure crop (40 t/ha) is homogeneously incorporated into the topsoil (0-30 cm) after which the field is lightly compacted and irrigated. Subsequently the field is mechanically covered with air tight virtually impermeable film (VIF) to restrict oxygen supply to the topsoil. The soil is left covered for six weeks in the summer. In this period anaerobic conditions develop rapidly in which toxic fermentation products are formed. These conditions are responsible for elimination of fungal and bacterial pathogens as well as parasitic nematodes, insects and weeds. In the Netherlands since 2004 anaerobic soil disinfestation (ASD) was applied on approximately 70 ha mainly for asparagus and strawberry runners production. When the asparagus crop was replanted ASD proved to be profitable for many years by controlling Fusarium oxysporum. Although highly effective against soilborne pathogens and pests ASD is not applied widely in the Netherlands due to the high costs of about € 4000 per ha. Apart from the costs this technique needs special attention to prevent plastic damage. Moreover the mechanism behind ASD is not well defined which makes recommendations for growers complex. A new and promising development in ASD is the application of defined products on a basis of mixtures of carbon hydrates and proteins. The mechanism of ASD will be studied in the next few years with some of these products by measuring gases and fatty acids and microbial shifts in relation to efficacy. Chemical soil disinfestation with fumigants is restricted more and more and a non-chemical approach of soil disinfestation like ASD is urgently neede