Soil Fate of Agricultural Fumigants in Raised-Bed, Plasticulture Systems in the Southeastern United States

Abstract

Soil concentrations and degradation rates of methyl isothiocyanate (MITC), chloropicrin (CP), 1,3-dichloropropene (1,3-D), and dimethyl disulfi de (DMDS) were determined under fumigant application scenarios representative of commercial raised bed, plastic mulched vegetable production systems. Five days after application, 1,3-D, MITC, and CP were detected at concentrations up to 3.52, 0.72, and 2.45 μg cm −3 , respectively, in the soil atmosphere when applications were made in uniformly compacted soils with a water content >200% of fi eld capacity and covered by a virtually impermeable or metalized fi lm. By contrast, DMDS, MITC, and CP concentrations in the soil atmosphere were 0.81, 0.02, and 0.05 μg cm −3 , respectively, 5 d after application in soil containing undecomposed plant residue, numerous large (>3 mm) clods, and water content below fi eld capacity and covered by low-density polyethylene. Ranked in order of impact on the persistence of fumigants in soil were soil water content (moisture), soil tilth (the physical condition of soil as related to its fi tness as a planting bed), the type of plastic fi lm used to cover fumigated beds, and soil texture. Fumigants were readily detected 13 d after application when applied in uniformly compacted soils with water contents >200% of capacity and covered by a virtually impermeable or metalized fi lm. By contrast, 1,3-D and MITC had dissipated 5 d after application in soils with numerous large (>3 mm) clods and water contents below fi eld capacity that were covered by low-density polyethylene. Soil degradation of CP, DMDS, and MITC were primarily attributed to biological mechanisms, whereas degradation of 1,3-D was attributed principally to abiotic factors. Th is study demonstrates improved soil retention of agricultural fumigants in application scenarios representative of good agricultural practices.

Photocatalytic films for soil fumigation: Control of dimethyl disulfide concentration after fumigation

“…In case of the colored films, the pollutant molecules also have to diffuse through a supplementary PE colored layer, not favored in the case of acetone. Such a different permeability of PE films toward various fumigants has been already been reported [7]. We however demonstrated from the absence of by-products in significant amounts (only acetaldehyde at the ppbV level) that acetone mineralization was almost complete (i.e.…”

“…Several studies were led in laboratory and in full fields with several PE films to monitor fumigants dispersal in air and soil. The efficiency of these films depended on their permeability against a given fumigant but also on the temperature, the soil moisture and the ground texture [7]. Nevertheless, impermeable films improved ground disinfection relative to LDPE.…”

Effect of application rate on fumigant degradation in five agricultural soils

“…In an earlier incubation study using Tifton loamy sand and Dothan sandy loam, Chellemi et al (2011) also observed short half-life of DMDS (1.0-1.6 d) applied at 20 mg kg −1 at 25°C. The degradation rate decreased significantly (P b 0.05) as application rate increased from 20 to 80 mg kg −1 for all soils (Table 5).…”

“…Residual fumigants in the incubated soils were extracted following the procedures of Guo et al (2003); Chellemi et al (2011), andZheng et al (2004a). In brief, after the frozen vials containing the fumigant treated soil were uncapped, anhydrous sodium sulfate was added at a water to Na 2 SO 4 ratio (w:w) of 1:7, followed by the addition of 8 mL of ethyl acetate, the vials were resealed immediately.…”

“…For extraction of 1,3-D and CP, the vials were placed in a water bath at 75°C overnight with intermittent shaking (Guo et al, 2003). DMDS and MeI samples were extracted using a reciprocating shaker for 1 h (Chellemi et al, 2011;Zheng et al, 2004a). The vials were centrifuged at 207 g for 5 min and approximately 1 mL of the supernatant was transferred into a 2-mL amber glass vial and capped for analysis.…”