Abstract
Soil biodisinfestation is the process generated after the incorporation of organic amendments followed by a plastic cover to control soilborne diseases. Among organic amendments, the use of agricultural by-products could be an interesting alternative as it promotes circular economy. In this study, beer bagasse and defatted rapeseed cake together with fresh cow manure were incorporated into the soil (1.5, 0.5, and 20 kg/m2, fresh weight, respectively) to assess their capacity to reduce disease incidence caused by the root-knot nematode Meloidogyne incognita in protected lettuce crops and develop suppressive soils. The trial was conducted in a commercial greenhouse for 7 weeks during which temperature was continuously recorded at three different soil depths (15, 30, and 45 cm). Short- and long-term effects were assessed: before treatment, after treatment, after first crop post-treatment and one year post-treatment. Disease incidence and changes in nematode community structure were analyzed along with microbiological properties and general physicochemical parameters. After biodisinfestation, microbiological activity significantly increased in the treated soils and changes in the nematode community structure were detected in detriment of M. incognita and other plant-parasitic nematodes. These effects were more apparent after the first crop post-treatment than right after biodisinfestation. In the first crop after biodisinfestation, lettuce yield increased in the treated plots and root galling indices were significantly lower. One year after treatment, differences between treatments could be observed in the incidence of the damage caused by M. incognita that remained lower in the treated plots. In this trial, the addition of beer bagasse and rapeseed cake along with fresh manure in biodisinfestation treatment demonstrated nematicidal effects against M. incognita. Moreover, we suggest that the compounds released during the degradation of these by-products and the sub-lethal temperatures achieved in this trial during biodisinfestation (<42°C) were the key to develop suppressive soils in the long-term.
Highlights
Conventional crop management includes pathogen control and the use of chemical fumigants is the most common practice, but many of them are harmful and cause environmental damages
Beer bagasse and rapeseed cake together with fresh cow manure were incorporated into the soil as organic amendment in biodisinfestation treatment against RKN M. incognita in a commercial lettuce greenhouse with significant yield losses
fresh cow manure (FCM) presented the highest amount of organic matter (65.36%) but similar N total content as rapeseed cake (RC) (1.48 and 1.36, respectively)
Summary
Conventional crop management includes pathogen control and the use of chemical fumigants is the most common practice, but many of them are harmful and cause environmental damages. Biosolarization is based on the incorporation of organic amendment followed by mulching with transparent polyethylene plastic film during hot seasons in order to achieve high soil temperatures These conditions promote certain physical, microbiological and biochemical processes that contribute to disease reduction and even a decrease in soil pathogen populations (Katan, 2014; Katan and Gamliel, 2014). In climate regions with low solar radiation, labile C-sources are used to boost anaerobic conditions and this strategy is commonly called anaerobic soil disinfestation (ASD) (Shennan et al, 2018; Rosskopf et al, 2020) Another practice is the incorporation of plants of the Brassicaceae family, which is known as biofumigation (Kirkegaard et al, 1993). These ITCs along with other biocidal compounds produced during decomposition of plant tissue, like volatile fatty acids (VFA) and NH3, have demonstrated biocidal activity (Oka et al, 2007; Dutta et al, 2019)
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