ARS | Publication request: MODELING METHYL BROMIDE FUMIGATION PERFORMANCE IN VEGETABLE PLASTIC-MULCHEDSOIL BEDS

Submitted to: Pesticide Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 16, 2000
Publication Date: August 14, 2000

Interpretive Summary: Effect of soil thermal environment on water flow and chemical movement needs to be explored in vegetable beds covered with plastic mulch. A coupled water-heat flow and chemical movement computer was used to describe fate and transport of methyl bromide fumigant in low density polyethylene plastic-mulched soil bed used for vegetable production. Effect of thermal energy on chemical transport were considered through inclusion of temperature effects on coefficients affecting chemical transformation and movement. Simulations for various scenarios revealed that large amounts (20-44% over a 7-day period) of applied methyl bromide were lost from the un-mulched furrows between the beds. Plastic-mulching of the bed was found to be only partially effective (11-29% emission losses over a 7-day period) in reducing atmospheric emissions. The investigation revealed that saturating the soil with water and deeper fumigant injection increased retention of methyl bromide within the soil and reduced emission to the atmosphere. Thus computer model could help in optimization of fumigant dosage and better management of fumigation process.

Technical Abstract: A coupled water-heat and chemical transport model was used to describe fate and transport of methyl bromide (MBr) fumigant in low density polyethylene (LDPE) plastic-mulched soil bed used for vegetable production. Transport of MBr was described by convective-dispersive processes including transformations involving hydrolysis. Effect of non-isothermal conditions on chemical transport were considered through inclusion of temperature effects on transport parameters. Sophisticated energy balance was used to describe the plastic-mulched boundary condition, which significantly affects the thermal regime within the bed. Simulations were made for variable water-saturation regimes within the bed and for different depths of fumigant injection. Simulations for various scenarios revealed that large amounts (20-44% over 7-day period) of applied MBr were lost from the un-mulched furrows between the beds. Plastic-mulching of the bed was found to be only partially effective (11-29% emission losses over a 7-day period in reducing atmospheric emissions. Saturating the soil with water and deeper fumigant injection showed increased retention of MBr within the soil and less emission to the atmosphere. However, deeper injection was not found to be conducive for sterilization of the crop root zone.