Using Anaerobic Soil Disinfestation in Organic Vegetable Production

Anaerobic soil disinfestation (ASD) or biological soil disinfestation (BSD) is a process that involves incorporation of a labile carbon source into soil, covering soil with polyethylene film to limit oxygen exchange, and saturating the treated soil to allow it to become anaerobic. This method has been shown to control many plant pathogenic fungi, bacteria, nematodes, and weeds. Rates of soil carbon amendment and soil temperatures have all been identified as important factors in developing effective levels of anaerobic activity and plant pathogen control. The putative mechanisms of ASD comprise of direct and indirect biological control, including the generation of organic acids and volatile compounds. In the investigation and application of the technique in Florida, the development of anaerobic conditions has not been correlated with weed control, but the use of clear plastic combined with organic amendments has resulted in the most significant reduction in weeds. Recent work has allowed for the substitution of totally impermeable film for solarization film, which would reduce the total amount of mulch film and eliminates one hurdle for adoption of ASD. Composted poultry litter has been utilized as a nitrogen source in one approach for ASD application and conventional vegetable growers have expressed concern over potential food safety issues related to the use of composted animal manures.  The composted poultry litter serves to lower the C:N ratio during ASD treatment and potentially increases water holding capacity and microbial diversity in sandy soils with a history of soil fumigation. In order to address this concern, multiple organic residues with relatively high nitrogen content have been tested for their suitability as a component in ASD. Also, targeted human pathogen testing is being conducted on soil inputs, soil, and harvested fruit. ASD has been used to produce tomato, cucumber, bell pepper, eggplant, strawberry, and flower crops successfully and with no foodborne human pathogen detections. The approach can be scaled to accommodate small-to-medium-sized production systems and tailored to the availability of local waste product inputs.