Emissions and distribution of methyl bromide in field beds applied at two rates and covered with two types of plastic mulches

Abstract

A field experiment was conducted to compare two plastic mulches and two application rates on surface emissions and subsurface distribution of methyl bromide (MBr) in field beds in Florida. Within 30 minutes after injection of MBr to 30 cm depth, MBr had diffused upward to soil surface in all beds covered with polyethylene film (PE) or virtually impermeable film (VIF) and applied at a high rate (392 kg/ha) and a low rate (196 kg/ha). Due to the highly permeable nature of PE, within 30 minutes after injection, MBr volatilized from the bed surfaces of the two PE-covered beds into the atmosphere. The amount of volatilization was greater for the high rate-treatment bed. On the other hand, volatilization of MBr from the bed surfaces of the two VIF-covered beds were negligible. Volatilization losses occurred from the edges of all the beds covered with PE or VIF and were greater from the high rate-treatment beds. Initial vertical diffusion of MBr in the subsurface of the beds covered with PE or VIF was mainly upward, as large concentrations of MBr were detected from near bed surfaces to 20 cm depth in these beds 30 minutes after injection and little or no MBr was found at 40 cm depth. The two VIF-covered beds exhibited greater MBr concentrations and longer resident times in the root zone (0.5-40 cm depth) than corresponding PE-covered beds. Concentrations of MBr in the root zone of the high rate-treatment beds were 3.6-6.1 times larger than the low rate-treatment beds during the first days after application. In conclusion, VIF promoted retention of MBr in the root zone and, if volatilization loss from bed edges can be blocked, volatilization loss from VIF-covered beds should be negligible.

Effect of Plastic Mulch Type on Fomesafen Dissipation in Florida Vegetable Production Systems

“…Films containing an EVOH barrier layer are currently referred to as TIF (Qin et al 2011). Films containing barrier polymers are significantly less permeable to fumigants than LDPE and high-density polyethylene (HDPE) mulches (Chellemi et al 2011; Gamliel et al 1998; Ou et al 2007; Qin et al 2011; Santos et al 2007; Wang et al 1998). Gamliel et al (1998) reported a 100-μm-thick LDPE film was more than 150-fold more permeable to methyl bromide than a 30-μm mulch containing an EVOH barrier layer.…”

Yellow Nutsedge (Cyperus esculentus) Control with Reduced Rates of Dimethyl Disulfide in Combination with Totally Impermeable Film

“…The most advanced highly retentive films are virtually impermeable film (VIF) and totally impermeable film (TIF). These films, manufactured by co-extrusion containing multilayers with barrier polymers, such as ethyl vinyl alcohol (EVOH) or polyamide (nylon), are significantly less permeable to fumigants than LDPE and HDPE (Chellemi et al 2011;Fennimore and Ajwa 2011;Gamliel et al 1998;Ou et al 2007;Qin et al 2011;Santos et al 2007b;Wang et al 1998;Yates et al 2002). Films containing an EVOH barrier layer are currently referred to as totally impermeable film (TIF) (Chow 2009;Fennimore and Ajwa 2011;Gao et al 2011;Qin et al 2011).…”

Retention of the Soil Fumigant Dimethyl Disulfide by Virtually and Totally Impermeable Film Mulches

“…Benefits of mulches with increased fumigant retention are a reduction in the amount of fumigant needed for effective pest control, lower emissions, and a decreased buffer zone requirement. Films manufactured by coextrusion containing multilayers with barrier polymers such as ethyl vinyl alcohol (EVOH) or polyamide (nylon) are significantly less permeable to fumigants (Gamliel et al, 1998;Ou et al, 2007;Santos et al, 2007;Wang et al, 1998;Yates et al, 2002) than LDPE and HDPE. These less permeable films were all classified as VIF in the literature regardless of the type of barrier material or permeability rate (Austerweil et al, 2006;Minuto et al, 1999;Ou et al, 2007;Wang et al, 1998;Yates et al, 2002).…”