Effects of chloropicrin soil fumigation on pathogenic and beneficial soil microbial populations in tomato production in EU

Chloropicrin soil fumigation is a specific, but highly efficient mode of soil pathogens control, using specialized technology and procedures. Until recently, it was believed that, among target organisms, it has a negative effect on beneficial soil micro flora causing 'biological soil vacuum'. In 2012/2013, soil samples were taken during commercial soil treatments with fumigant chloropicrin, in three intensive tomato (Lycopersicon esculentum) production areas in Italy. Soil microbial population dynamics was investigated 0, 42, and 180 days after treatment, throughout the adoption of semi selective media. The research aimed to determine the effect of chloropicrin soil fumigation on dynamics of pathogenic populations of fungi and bacteria, as well as their natural antagonists from fungal genus Trichoderma ssp. and bacterial genera Pseudomonas ssp. and Bacillus ssp., to evaluate its efficiency with targeted organisms and to justify chloropicrin soil fumigation from an environmental and agronomic standpoint. The analyses showed detrimental effects on phytopathogenic fungi and bacteria, particularly Fusarium ssp. populations, while Trichoderma ssp., fluorescent aerobic bacteria and Bacillus ssp. enhanced their population density after the fumigation treatment. The obtained data i) confirms previous efficacy findings, ii) denies existence of 'biological soil vacuum effect' and might explain increase in aerial and root vigor and plant yield transplanted on fumigated soil. Furthermore, fumigantRSQUOs response period, degradation and movement in the soil is determined by soil moisture, particle size and pH. To conclude, soil fumigation with chloropicrin effects target and non-targeted soil microorganisms and can be used as an advantage to create an agronomical favored rhizosphere conditions.