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United States Department of Agriculture

Agricultural Research Service

Methyl Bromide
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1 - Background
2 - Chemical and Physical Properties
3 - Reactions with Stratospheric Ozone
4 - Solubility
5 - Henry's Law Constant
6 - Vapor Pressure
7 - Adsorption
8 - Diffusion Coefficient
9 - Air Sampling
10 - Field Experiments
11 - Transformation of MeBr in Water
12 - Transformation of MeBr in Soil
13 - Transport Model
14 - Simulating MeBr Volatilization
15 - Fumigation
16 - Post-Fumigation
17 - Further Reading
Methyl Bromide Fumigation
Two months before fumigating with methyl bromide, the soil was ripped to a depth of approximately 0.75 m in both the north-south and east-west directions. This was followed by discing, to break up the soil large aggregates. Several weeks before applying methyl bromide, the field was irrigated and followed by a waiting period that lasted until the soil water content was near field capacity.
The morning that methyl bromide was applied, the field was cultimulched to break any remaining soil aggregates to further protect the plastic from punctures. After cultimulching, the surface soil had a bulk density of approximately 1.35-1.40 gm/cm3 and was easily compressed.
Methyl bromide was applied to the field by a commercial applicator using a tractor containing two noble plows mounted on the center section of the tool bar with four injection points evenly spaced along each plow. A standard straight shank was located at each end of the tool bar. There were a total of 11 injection points for each panel (e.g., the width of field covered by a single sheet of plastic), spaced laterally approximately 0.25 m apart. During the first north-south pass along the eastern side of the field, methyl bromide was applied to the soil and a 3.6 m (i.e., 12 feet) sheet of 0.025 mm (1-mil) high-density polyethylene plastic was rolled out from behind the tractor and a small portion of each edge buried with a small noble plow located at the end of the tool bar. When the tractor reversed directions for the next pass, one side of the plastic was glued to the previous panel near the buried edge and the other edge was buried. This application method creates a series of panels down the field and a continuous polyethylene cover over the field.
The depth of injection was approximately 0.25 m. The methyl bromide was applied to the field as 99.5% methyl bromide (CH3Br) and 0.5% chloropicrin (CCl3NO2) (EPA Reg. No. 8536-12-11220). The application rate was approximately 240 kg/ha (i.e., 215 lb/a) to an area of approximately 3.5 ha (i.e., 8.6 acres), for a total applied mass of 843 kg. The fumigation process took 6 1/2 h and began at 0800 h.
Yates, S.R., Gan, J., Ernst, F.F., Mutziger, A., Yates, M.V. 1996. Methyl bromide emissions from a covered field. I. Experimental Conditions and Degradation in Soil. Journal Environmental Quality 25:184-192.
Yates, S.R., Ernst, F.F., Gan, J., Gao, F. and Yates, M.V. 1996. Methyl bromide emissions from a covered field. II. Volatilization. Journal Environmental Quality 25:192-202.
Yates, S.R., Gan, J. and Ernst, F.F. Methyl bromide emissions from a covered field. III. 1996. Correcting Chamber Flux for Temperature. Journal Environmental Quality 25:892-898.
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Last Modified: 10/20/2005
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