Project Number: 6615-12000-004-00
Project Type: Appropriated

Start Date: Dec 17, 2007
End Date: Dec 16, 2012

Objective:
Improve efficacy of low-vapor-pressure alternative pre-plant soil fumigants (such as 1,3-dichloropropene, chloropicrin, and methyl isothiocyanate) by improving dispersion and distribution in the target treatment zone by use of carbonated solutions that degas within the soil and thereby propel the dispersion of fumigant vapors. Improve retention of soil fumigants by improved placement of virtually impermeable films or use of other absorption-reactant materials, especially in the middles between raised-bed plasticulture systems.

Approach:
Initially, laboratory experiments of dispersion enhancement provided by carbon dioxide/decarbonating solutions will be conducted using a physical scale model soil box that will emulate an actual cross-row slice (30-cm thick) of field soil of raised-bed plasticulture systems. The soil box will have a two-dimensional vertical and horizontal array of gas sampling ports installed on the back panel and injection ports at several depths and horizontal spacings along the vertical centerline of the panel. Air bag bladders will be appropriately installed at the top of the soil box for pressure equalization to avoid back-pressure artifacts. Soil covered with VIF film with deep-buried edges will be tested to minimize emissions from the row middles. Various amounts of propellant gas in water supersaturated with carbon dioxide will be administered to determine the optimum for displacement-dispersion of alternative low-vapor-pressure fumigants. The time and space relationships of dispersion of propellant and fumigant will be obtained by GC analysis of soil-air samples obtained from sampling port probes. Information from the laboratory soil box will be applied to planning and executing field-plot studies using carbonated water provided by a pinpoint carbonator during or following drip tube placement of fumigants. Effectiveness of carbon dioxide for dispersion of low-vapor-pressure fumigants in the field will be determined using arrays of soil air probes and surface emission pans. Findings and accomplishment will be relayed to the scientific and customer-stakeholder community as appropriate.