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Fumigant application rates at the Florida and Georgia trials.

 
Fumigant Site 1 Site 2 Site 3
Florida trials
 1,3-Dichloropropene, kg ha−1 142 145 n/a†
 Chloropicrin, kg ha−1 192 198 184
 Metam potassium, kg ha−1 348 336 342
Georgia trials
 Dimethyl disulfide, kg ha−1 612 603 637
 Chloropicrin, kg ha−1 162 160 169
 Metam sodium, kg ha−1 335 343 331
1,3-Dichloropropene not applied.



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Permeability of plastic films to fumigants used in the study.

 
Trial† Film type‡ Location Permeability§
cis 1,3-D trans 1,3-D CP MITC DMDS
h cm−1
FL sites 1 and 3 metalized roll 10.6 ± 3.0¶ 6.0 ± 2.0 37.0 ± 12.0 NS# 1.8 ± 0.50
FL sites 1 and 3 metalized field 1.6 ± 0.4 1.0 ± 0.3 5.0 ± 1.0 0.9 ± 0.1 2.7 ± 0.68
FL site 2 VIF roll 104 ± 3.0 41.0 ± 1.0 3618 ± 292 2.6 ± 0.4 159 ± 24.7
FL site 2 VIF field 78.0 ± 2.0 28.0 ± 3.0 2477 ± 228 2.1 ± 0.2 80.6 ± 39.5
GA sites 2 and 3 LDPE roll 0.13 ± 0.01 0.08 ± 0.01 0.37 ± 0.01 0.05 ± 0.01 0.13 ± 0.01
GA sites 2 and 3 LDPE field 0.13 ± 0.01 0.08 ± 0.01 0.38 ± 0.01 0.05 ± 0.01 0.10 ± 0.01
GA site 1 VIF roll 601 ± 19 227 ± 4.0 42,466 ± 6230 6.0 ± 3.0 7327 ± 3659
GA site 1 VIF field 310 ± 94.0 133 ± 28.0 14,672 ± 7468 6.9 ± 0.6 74.8 ± 12.0
FL, Florida; GA, Georgia.
LDPE, low-density polyethylene; VIF, virtually impermeable film.
§ Permeability (R) = 1 h−1, where h = mass diffusion coefficient.
Values are the mean of three replicate cells ± SD. All films tested at 25°C.
# Not sampled.



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Characterization of soil properties at the fumigant application sites.

 
Parameter Site 1 Site 2 Site 3
Florida trials
Organic carbon, Mg ha−1 9.73 16.0 13.3
Bulk density, g cm−3 1.49 1.44 1.40
Sand, g kg−1 940 935 960
Silt, g kg−1 35.0 40.0 20.0
Clay, g kg−1 25.0 25.0 20.0
Water content, g kg−1 125 153 144
Water content at 33 kPa suction, g kg−1 51.1 74.0 62.9
% of field capacity (33 kPa suction) 245 206 229
Georgia trials
Organic carbon content, Mg ha−1 6.85 6.41 6.85
Bulk density, g cm−3 1.50 1.38 1.52
Sand, g kg−1 792 812 860
Silt, g kg−1 124 84 132
Clay, g kg−1 84.0 104 8.00
Water content, g kg−1 83.0 99.0 81.0
Water content at 33 kPa suction, g kg−1 117 152 109
Moisture relative to field capacity, % 71 65 74



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Environmental conditions at time of application.

 
Site 1 Site 2 Site 3
Duette, FL
    Ambient temperature, °C 18.0 19.4 19.4
    Soil temperature at 15 cm depth, °C 15.8 18.0 19.2
 Wind speed, m s−1 0.90 0.70 0.40
Tifton, GA
    Ambient temperature, °C 21.1 20.0 15.6
    Soil temperature at 15 cm depth, °C 9.20 11.1 13.3
 Wind speed, m s−1 2.70 2.20 0.20



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First-order degradation rate constants of fumigants in field and autoclaved soil at 25°C and 40°C.

 
Site Field soil, 25°C Autoclaved soil, 25°C Field soil, 40°C Autoclaved soil, 40°C
d−1
Florida trials
Chloropicrin
    1 1.71 (0.93) 0.24 (0.93)† 3.83 (0.98) 0.98 (0.96)
    2 4.91 (0.97) 0.42 (0.96) 17.3 (0.97) 1.92 (0.99)
    3 1.21 (0.93) 0.26 (0.87) 1.47 (0.96) 0.91 (0.96)
1,3-dichloropropene (cis)
    1 0.13 (0.70) 0.13 (0.91) 0.57 (0.98) 0.45 (0.99)
    2 0.17 (0.81) 0.16 (0.94) 0.72 (0.99) 0.47 (0.99)
    3 0.17 (0.94) 0.14 (0.71) 0.73 (0.98) 0.45 (0.98)
1,3-dichloropropene (trans)
    1 0.11 (0.92) 0.14 (0.69) 0.55 (0.97) 0.58 (0.99)
    2 0.14 (0.93) 0.16 (0.84) 0.72 (0.99) 0.52 (0.97)
    3 0.14 (0.71) 0.17 (0.92) 0.84 (0.99) 0.42 (0.91)
Methyl isothiocyanate
    1 0.08 (0.98) 0.05 (0.90) 0.27 (0.99) 0.15 (0.99)
    2 0.10 (0.98) 0.04 (0.87) 0.31 (0.99) 0.22 (0.99)
    3 0.10 (0.98) 0.05 (0.94) 0.32 (0.99) 0.18 (0.98)
Georgia trials
Chloropicrin
    1 0.40 (0.95) 0.18 (0.95) 0.58 (0.88) 0.33 (0.94)
    2 0.37 (0.94) 0.13 (0.93) 0.52 (0.85) 0.43 (0.97)
    3 0.36 (0.87) 0.15 (0.96) 0.58 (0.92) 0.40 (0.98)
Methyl isothiocyanate
    1 0.12 (0.98) 0.05 (0.93) 0.43 (0.98) 0.77 (0.96)
    2 0.28 (0.99) 0.08 (0.95) 0.96 (0.99) 0.27 (0.93)
    3 0.07 (0.95) 0.05 (0.92) 0.30 (0.98) 0.21 (0.77)
Dimethyl disulfide
    1 0.60 (0.92) 0.03 (0.44) 0.26 (0.81) 0.08 (0.75)
    2 0.68 (0.93) 0.03 (0.44) 0.28 (0.90) 0.09 (0.71)
    3 0.44 (0.74) 0.02 (0.43) 0.11 (0.68) 0.06 (0.50)
Numbers in parentheses are regression coefficients.