objectives
DESCRIPTION
Series Kd r 2 Kd correlations Lanton2.10.98 Prob. Duval1.30.99Sand0.03 Brownfield0.90.99Silt0.07 Greenville2.40.99Clay0.03 Dothan1.40.99pH0.67 Cecil1.40.98CEC0.23 Tifton1.30.99OM0.17. Introduction - PowerPoint PPT PresentationTRANSCRIPT
Objectives• Develop Kd values for flumioxazin on seven
soils commonly found in the peanut growing regions of the South.
• Describe adsorption kinetics.
• Describe desorption of flumioxazin.
Objectives• Develop Kd values for flumioxazin on seven
soils commonly found in the peanut growing regions of the South.
• Describe adsorption kinetics.
• Describe desorption of flumioxazin.
Introduction• Flumioxazin (Valor 51WP) has been labeled
for soybean and peanut since 2001.
• Flumioxazin has been most commonly used in the peanut growing regions of the South.
• No adsorption data currently exist for flumioxazin in the EPA package or in technical data recources
• Flumioxazin is non-ionic with a H2O solubility 1.79 mg/L at 25C.
Introduction• Flumioxazin (Valor 51WP) has been labeled
for soybean and peanut since 2001.
• Flumioxazin has been most commonly used in the peanut growing regions of the South.
• No adsorption data currently exist for flumioxazin in the EPA package or in technical data recources
• Flumioxazin is non-ionic with a H2O solubility 1.79 mg/L at 25C.
Materials and Methods
Batch Equlibrium• 2 g soil.• 10 ml 0.01M CaCl2.• 0, 10, 20, 40, 60 µM flumioxazin.• Shaking time – 24h.• Analysis of adsorption by LCS.
Adsorption Kinetics• Greenville sandy clay loam.• Samples removed 1, 6, 12, 24, 48, 72h.• Adsorption quantified by LCS.
Desorption
• Initial sorption time – 24h.
• Replaced with herbicide free 0.01M CaCl2.
• Desorbed for 24, 48, 72, 96h.
Materials and Methods
Batch Equlibrium• 2 g soil.• 10 ml 0.01M CaCl2.• 0, 10, 20, 40, 60 µM flumioxazin.• Shaking time – 24h.• Analysis of adsorption by LCS.
Adsorption Kinetics• Greenville sandy clay loam.• Samples removed 1, 6, 12, 24, 48, 72h.• Adsorption quantified by LCS.
Desorption
• Initial sorption time – 24h.
• Replaced with herbicide free 0.01M CaCl2.
• Desorbed for 24, 48, 72, 96h.
Yield
0
500
1000
1500
2000
2500
1 2 3 4 5 6 LSD
Treatment
Lin
t w
eigh
t (k
g/ha
)
1996-1997 1998
Yield
0
500
1000
1500
2000
2500
1 2 3 4 5 6 LSD
Treatment
Lin
t w
eigh
t (k
g/ha
)
1996-1997 1998
Ivyleaf Morningglory Control
0
20
40
60
80
100
120
1 2 3 4 5 6 LSD
Treatment
Per
cen
t C
ontr
ol (
%)
1996-1997 1998
Ivyleaf Morningglory Control
0
20
40
60
80
100
120
1 2 3 4 5 6 LSD
Treatment
Per
cen
t C
ontr
ol (
%)
1996-1997 1998
Future Research
•Determine the relative leaching potential of flumioxazin.
•Determine the duration of flumioxazin persistence in soil.
•Determine transformation products of flumioxazin by soil microflora.
*The authors thank Valent USA for supplying 14C-flumioxazin.
Future Research
•Determine the relative leaching potential of flumioxazin.
•Determine the duration of flumioxazin persistence in soil.
•Determine transformation products of flumioxazin by soil microflora.
*The authors thank Valent USA for supplying 14C-flumioxazin.
State Series % OC % sand % silt % clay
Kentucky Lanton loam 5.3 36 38 26
Texas Duval sandy loam 0.8 78 10 12
Texas Brownfield sand 0.2 90 2 8
Georgia Greenville sandy clay loam
2.6 58 10 32
Georgia Dothan sandy loam
0.9 85 12 3
Georgia Cecil sandy loam 2.6 62 20 18
Georgia Tifton loamy sand 1.6 94 4 2
Flumioxazin Adsorption Kinetics
00.10.20.30.40.50.60.70.80.9
1
0 20 40 60 80
Hours
% a
dso
rbe
d
Flumioxazin Desorption
0
20
40
60
80
100
120
140
160
0 10 20 30 40 50 60
C (µmol L-1)
S (
µm
ol g
-1)
adsorption
desorption
Results
Adsorption
•Sorption isotherms were linear.
•Flumioxazin is not tightly bound to soil (Kd values 2.4-0.9).
•With many Kd’s near 1.0, flumioxazin has near equal affinity for sorbed or solution phase.
•OM content was not correlated to flumioxazin sorption.
Adsorption Kinetics
•72% of flumioxazin was bound to soil within 1h; sorption was near instantaneous.
•After 72h, sorption was increased to 78%.
Desorption
•Desorption rates were similar to adsorption; thus, equlibrium is soil solution will be reached quickly.
•Rapid desorption could lead to flumioxazin availability during a rainfall event, thus making it susceptible to leaching.
Results
Adsorption
•Sorption isotherms were linear.
•Flumioxazin is not tightly bound to soil (Kd values 2.4-0.9).
•With many Kd’s near 1.0, flumioxazin has near equal affinity for sorbed or solution phase.
•OM content was not correlated to flumioxazin sorption.
Adsorption Kinetics
•72% of flumioxazin was bound to soil within 1h; sorption was near instantaneous.
•After 72h, sorption was increased to 78%.
Desorption
•Desorption rates were similar to adsorption; thus, equlibrium is soil solution will be reached quickly.
•Rapid desorption could lead to flumioxazin availability during a rainfall event, thus making it susceptible to leaching.
Series Kd r2 Kd correlations
Lanton 2.1 0.98 Prob.
Duval 1.3 0.99 Sand 0.03
Brownfield 0.9 0.99 Silt 0.07
Greenville 2.4 0.99 Clay 0.03
Dothan 1.4 0.99 pH 0.67
Cecil 1.4 0.98 CEC 0.23
Tifton 1.3 0.99 OM 0.17
Series Kd r2 Kd correlations
Lanton 2.1 0.98 Prob.
Duval 1.3 0.99 Sand 0.03
Brownfield 0.9 0.99 Silt 0.07
Greenville 2.4 0.99 Clay 0.03
Dothan 1.4 0.99 pH 0.67
Cecil 1.4 0.98 CEC 0.23
Tifton 1.3 0.99 OM 0.17