2007 Extension Research Report
Cultural Management
EVALUATING GAS FUMIGANTS RELEASED THROUGH VARIOUS
MULCHES 2006
Paul E Sumner1 and Stanley Culpepper2, University of Georgia Cooperative Extension,
Departments 1Biological and Agricultural Engineering and 2Crop and Soil Science, P.O. Box
748, Tifton, GA 31793, psumner@uga.edu
fumigation. Many different chemical, soil,
and environmental factors interact to cause
the wide variation of reported emission
losses from soil with methyl bromide. In
general, the rates in which methyl bromide
volatilizes from soil under typical
conditions are initially high following
application and then decrease with time,
such that after 5 to 7 days post application,
little remains in soil (Figure.1). Data is
plotted only to show general decline in
emissions with time, and highest daily rates
of emission occurring midday and lowest
emissions at night. Besides temperature,
other soil and environmental conditions can
modify methyl bromide emissions from soil
greatly.
Introduction
Methyl bromide has been used as a
soil fumigant since the 1930’s. Since its
discovery and implementation, methyl
bromide has been consistently effective for
control of nematodes, fungi, soil insects,
and weeds. Methyl bromide’s high vapor
pressure allows rapid and thorough
distribution throughout the soil profile. This
vapor pressure facilitates a relatively short
plant-back interval.
In addition to the horticultural
advantages, plastic mulches also serve to
delay the volatilization of fumigant gases
like methyl bromide from soil, and reduce
emissions into the atmosphere. In practical
reality however, the LDPE mulches in
common use today actually provide little
direct physical barrier to the diffusion of
methyl bromide through the mulch. Beds
which are moist and tightly compressed are
much more resistant to methyl bromide
diffusion than beds which are dry and only
loosely compacted or pressed (Noling,
2002).
Mulch Permeability
The permeability (the ability to pass
through) of a plastic mulch to a gas
fumigant is based on the thickness, density,
and chemical composition of the plastic
mulch. Regardless of composition, thicker
mulches are generally less permeable to
methyl bromide than are thin mulches
(Figure 2). In most cases, practical and cost
efficiency considerations prevent the use of
thicker LPDE mulches for enhanced
containment of methyl bromide in soil.
Some plastic mulches provide better
diffusion barrier to certain fumigants than
others. For example, permeability to methyl
bromide decreases as the density of a mulch
increases. High density polyethylene
(HDPE) mulches are less permeable to
methyl bromide than LDPE mulches.
Emissions of Methyl Bromide from
Agricultural Fields
In recent years many different
experiments have been conducted to obtain
information on methyl bromide emissions
from bare and mulched soil following field
application. Much of this research appears
to show that as much as 20 to 90% of the
methyl bromide applied to a given field can
ultimately out-gas through the LDPE plastic
mulch cover and into the air after soil
11
Figure 2. Permeability of methyl bromide
(Mbr), Chloropicrin (Pic), and two isomers of
1,3-Dichloropropene (Telone) through high
density polyethylene (HDPE) plastic mulch of
two thicknesses. (Noling 2002)
Figure 1. Generalized representation of the
relative emissions of methyl bromide
volatilizing through a plastic mulch cover
with time after initial soil fumigation. (Noling
2002)
way combination (1,3-Dichloropropene
(Telone II), Chloropicrin and metam
sodium (VAPAM)) were the fumigants
used in the test.
Ponder Fall Test – An additional
area of plot land was prepared at the
University of Georgia Ponder Farm for
commercial pepper production on July
19, 2006. Soil type is Tifton sandy loam.
Three mulch films were evaluated. They
were LDPE (embossed), VIF Domestic
(Cadillac) and metalized smooth (silver
on black). Methyl bromide, methyl
iodide and three way combination (1,3Dichloropropene
(Telone
II),
Chloropicrin and metam sodium
(VAPAM)) were the fumigants used in
the test.
Telone II was applied at 12
gallons/acre and metam sodium was
applied at 75 gallons/acre for all trials.
Table 1 is the rates used for the three
tests. Table gives the temperature and
rainfall fro the days gas fumigant data
was measured.
At the time the beds were formed
at all locations soil moisture was ideal
for soil fumigation and bed formation.
Each fumigant gas was measured with a
gas detector pump (GASTEC GV100S)
with detector tubes for each. Plastic
Objectives
• Measure the amount of gas
movement of methyl bromide,
methyl iodide and chloropicrin
through various mulches.
Methods and Materials
TVP Test - Plot land was
prepared at the University of Georgia
Tifton Vegetable Park for commercial
pepper production on February 23, 2006.
Soil type is Tifton sandy loam. Two
mulch films were obtained. They were
LDPE (black on black) and metalized
(silver on black with a black strip 12
inches wide down the center). Methyl
bromide, methyl iodide and three way
combination
(1,3-Dichloropropene
(Telone II), Chloropicrin and metam
sodium (VAPAM) were the fumigants
used in the test.
Ponder Spring Test - Plot land
was prepared at the University of
Georgia Ponder Farm for commercial
pepper production on February 22, 2006.
Soil type is Tifton sandy loam. Four
mulch films were evaluated. They were
LDPE (embossed), LDPE Smooth (nonembossed), VIF Domestic (Cadillac) and
metalized smooth (silver on black).
Methyl bromide, methyl iodide and three
12
The range used were methyl bromide
(0.9 – 500ppm), methyl iodide (5 40ppm), and chloropicrin (0.05 –
16ppm).
funnels measuring 6.5 inches were glued
to mulch beds to be used to collect gases
as they pass through the mulch (Figure
3). Gas detector tubes were used to
measure the fumigant gasses in ppm.
Figure 3. Plastic funnels installed to collect gas fumigants released through various mulches.
Table 1. Application rate of gas fumigants used in all trails.
Methyl Bromide
Methyl
(67:33)
Iodide(50:50)
Three Way
Combination –
Chloropicrin
Application Rate (Gallons/Acre)
400
150
400
150
TVP* - LDPE
400
TVP – Metalized
400
Stripe
PS** – LDPE
350
350
PS – LDPE Smooth
350
350
PS – Metalized
350
350
PS – VIF
350
350
350
350
PF*** – LDPE
PF – Metalized
175
175
PF - VIF
175
175
*
**
***
Tifton Vegetable Park, Ponder Farm Spring, Ponder Farm Fall
150
150
150
150
150
75
75
applied 4inches deep with coulter knives
4 inches apart on the bed top.
Funnels were glued to the films
immediately after fumigation. Samples
of the air in the funnels were taken 1, 24,
48 hours after application of the
fumigants. Fumigant gas was measured
every day in the funnels until no gases
were detected. Plots of the measured
methyl bromide gas through different
Results and Discussion
Fumigants were applied in 6 feet
by 25 feet plots with 32 inch bed tops.
Methyl bromide, methyl iodide and
chloropicrin were applied with a supper
bedder layer injecting fumigant 8 inches
with injection knives 11 inches apart.
Telone II was applied with coulter
injection knife at 12 inches depth 12
inches apart in the pre-bed. Vapam was
13
Table 2. Temperature and rainfall data for the days
Date
Max.
Temp.
(°F)
Min.
Temp.
(°F)
Rain
(in)
Date
Max.
Temp.
(°F)
Min.
Temp.
(°F)
Rain
(in)
Feb 22, 2006
73.4
55.6
0.00
Jul 19, 2006
93.6
74.8
0.00
Feb 23, 2006
65.7
49.1
0.02
Jul 20, 2006
93.6
71.4
0.00
Feb 24, 2006
65.5
48.0
0.00
Jul 21, 2006
94.3
72.9
0.00
Feb 25, 2006
57.7
51.4
1.48
Jul 22, 2006
94.8
74.3
0.00
mulches for the three trials are shown in
figures 4-6. Figures 7-9 illustrates the
measured amount of methyl iodide gas
through various mulches in the three
trials. The three way combination only
chloropicrin could be measured with the
detector tubes. The graphics showing the
measured fumigant gas moving through
different mulches are figures 10-12.
These figures show that the permeability
of metalized and VIF mulches to
fumigant gas had significant reduction to
LDPE plastic mulch. This reduction is
illustrated in figures 13-15. Fumigants
passing through mulches were reduced
by 20 to 90 percent. VIF mulch had the
highest reduction.
Measured Methyl Bromide Through LDPE and Metalized Black
Striped Mulch, Tifton Vegetable Park Spring 2006
Measured Methyl Bromide Through Different Mulches,
Ponder Farm Spring 2006
LDPE
Metalized
LDPE
Black Stripe
Metalized
Smooth LDPE
VIF
250
80
A
A
70
200
A
60
Gas Emission (ppm)
Gas Emission (ppm)
A
50
A
40
A
30
A
20
100
B
B
B
0
AB
A
50
10
B
150
C
A
B
C
B
A
B
B
0
1
24
48
1
Hours After Application
24
48
Hours After Application
Figure 4. Measured methyl bromide fumigant
gas (400 lb/acre) through LDPE and
metalized black stripe mulch, Tifton
Vegetable Park Spring 2006. Values followed
by the same letter do not significantly differ
(P=0.05, LSD).
Figure 5. Measured methyl bromide fumigant
gas (350 lb/acre) through LDPE, metalized,
Smooth LDPE and VIF mulch, Ponder Farm
Spring 2006. Values followed by the same
letter do not significantly differ (P=0.05,
LSD).
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Measured Methyle Bromide Through Different Mulches Ponder
Farm Fall 2006
LDPE
Metalized
Measured Methyl Iodide Through Different Mulches
Ponder Farm Fall 2006
LDPE
VIF
450
1200
A
Metalized
VIF
B
400
1000
Gas Emission (ppm)
Gas Emission (ppm)
350
800
A
600
A
400
300
250
200
150
100
200
B
B B
C C
C
B
B
A
0
B
C
50
BCD
B
B
B
B B
CDE BC B-E
0
1
5
20
44
68
1
5
20
Hours After Application
Figure 6. Measured methyl bromide fumigant
gas through LDPE (350 lb/acre), metalized
(175 lb/acre), and VIF (175 lb/acre) mulch,
Ponder Farm Fall 2006.
Metalized
68
Figure 9. Measured methyl iodide fumigant
gas through LDPE (350 lb/acre), metalized
(175 lb/acre), and VIF (175 lb/acre) mulch,
Ponder Farm Fall 2006.
Measured Methyl Iodide Through LDPE and Metalized Black
Stripe Mulch, Tifton Vegetable Park Spring 2006
LDPE
44
Hours After Application
Measured Chloropicrin Through LDPE and Metalized Black
Stripe Mulch, Tifton Vegetable Park Spring 2006
Black Stripe
LDPE
Metalized
Black Stripe
45
7
6
30
25
A
A
20
15
A
A
10
A
A
5
4
3
B
2
B
A
5
A
A
A
A
35
Gas Emission (ppm)
Gas Emission (ppm)
40
A
A
1
0
1
24
0
48
24
48
Hours After Application
Hours After Application
Figure 10. Measured chloropicrin fumigant
gas (150 lb/acre) through metalized and black
stripe mulch, Tifton Vegetable Park Spring
2006. Values followed by the same letter do
not significantly differ (P=0.05, LSD).
Figure 7. Measured methyl iodide fumigant
gas (400 lb/acre) through metalized and black
stripe mulch, Tifton Vegetable Park Spring
2006. Values followed by the same letter do
not significantly differ (P=0.05, LSD).
Measured Chloropicrin Through Different Mulches
Ponder Farm Spring 2006
Measured Methyl Iodide Through Different Mulches
Ponder Farm Spring 2006
LDPE
Metalized
Smooth LDPE
30
B
A
25
A
C
20
A
15
10
Smooth LDPE
VIF
A
A
8
Gas Emission (ppm)
Gas Emission (ppm)
9
A
A
Metalized
A
10
A
40
35
LDPE
VIF
A
7
6
5
4
B
3
B
2
B
5
B
B
1
B
C
0
B
24
48
Hours After Application
0
1
24
48
Hours After Application
Figure 11. Measured chloropicrin fumigant
gas (150 lb/acre) through LDPE, metalized,
Smooth LDPE and VIF mulch, Ponder Farm
Spring 2006. Values followed by the same
letter do not significantly differ (P=0.05,
LSD).
Figure 8. Measured methyl iodide fumigant
gas (350 lb/acre) through LDPE, metalized,
Smooth LDPE and VIF mulch, Ponder Farm
Spring 2006. Values followed by the same
letter do not significantly differ (P=0.05,
LSD).
15
Reduction of Measured Gas Fumigant through Mulches
Compared to LDPE, Ponder Farm Spring 2006
Measured Chloropicrin Through Different Mulches
Ponder Farm Fall 2006
LDPE
Metalized
Smooth LDPE
VIF
90.0
80.0
25
Gas Emmission (ppm)
Metalized
VIF
B
30
B
70.0
20
60.0
C
B
Percent (%)
15
B
10
5
B
C
40.0
30.0
DE
B
50.0
20.0
E E
C
10.0
0
1
5
20
44
0.0
68
Methyl Bromide
Hours After Application
Chloropirin
Figure 14. Reduction of fumigant due to using
alternative mulches to LDPE, Ponder Farm
Spring 2006.
Figure 12. Measured chloropicrin fumigant
gas through LDPE (150 lb/acre), metalized
(75 lb/acre), and VIF (75 lb/acre) mulch,
Ponder Farm Fall 2006.
Reduction in Measured Gas Fumigant Through Mulch
Compared to LDPE
Metalized
Methyl Iodide
Reduction of Gas Emission Through Different Mulches
Compared to LDPE, Ponder Farm Fall 2006
Metalized
Black Stripe
VIF
100.0
90.0
80
80.0
60
70.0
Reduction (%)
Percent (%)
100
40
20
60.0
50.0
40.0
0
30.0
-20
20.0
10.0
-40
0.0
Methyl Bromide
-60
Methyl Bromide
Methyl Iodide
Methyl Iodide
Chloropirin
Chloropicrin
Figure 15. Reduction of fumigant due to using
alternative mulches to LDPE, Ponder Farm
Fall 2006.
Figure 13. Reduction of fumigant due to using
alternate mulch to LDPE, Tifton Vegetable
Park Spring 2006.
Pepper was transplanted the
week of March 14-17, 2006 for the
spring tests. Before transplanting holes
were punch in the mulch film 3 days
prior to transplanting at the Ponder farm.
The mulch film was punch and
transplanted immediately at the TVP.
Figure 16 shows transplant growth 3
weeks after transplanting grown in
metalized black stripe mulch.
The
transplants grown on the LDPE did not
have as much stunting as metalized
black stripe. The methyl iodide and
three way fumigation showed the most
stunting. Figures 18-20 illustrate the
percent stunting measured at the three
different tests. Pepper yield (figures 2123) was measured on all three tests.
Yields reflect the amount of stunting
measured
for
each
test.
16
Figure 16. Stunting of pepper 3 weeks after transplanting using metalized black strip mulch.
Figure 17. Comparison of stunting 3 weeks after transplanting on LDPE versus metalized black
stripe at TVP. April 7, 2006.
Stunting Due to Fumigants for Pepper
Ponder Farm Spring 2006.
Stunting Due to Fumigants for Pepper
Tifton Vegetetable Park Spring 2006.
LDPE
LDPE
Metalized Black Stripe
Metalized
LDPE Smooth
VIF
60
45
40
50
40
30
Stunting (%)
Stunting (%)
35
25
20
30
20
15
10
10
5
0
0
None
Methyl Bromide
Methyl Iodide
None
Three Way
Methyl Bromide
Methyl Iodide
Three Way
Figure 19. Comparison of plant stunting for
various fumigants and mulches. Ponder Farm
Spring 2006, April 21, 2006.
Figure 18. Comparison of plant stunting for
various fumigants and mulches. Tifton
Vegetable Park Spring 2006, April 17, 2006.
17
Comparison of Pepper Yeild for Various Fumigants
Ponder Farm Spring 2006
Stunting Due to Fumigants for Pepper
Ponder Farm Fall 2006.
LDPE
Metalized
LDPE
VIF
Metalized
LDPE Smooth
VIF
70
25
60
Yeild per Plot (lbs)
Stunting (%)
20
15
10
50
40
30
20
10
5
0
None
0
None
Methyl Bromide
Methyl Iodide
Methyl Iodide
Three Way
Figure 22. Comparison of pepper yields for
various fumigants and mulches. Ponder Farm
Spring 2006.
Figure 20. Comparison of plant stunting for
various fumigants and mulches. Ponder Farm
Fall 2006, August 15, 2006.
Comparison of Pepper Yeild for Various Fumigants
Ponder Farm Fall 2006
Comparison of Pepper Yeild for Various Fumigants, TVP 2006
LDPE
Methyl Bromide
Three Way
LDPE
Metalized Black Stripe
Metalized
VIF
70
120
AB
A
60
BC
80
BC
BC
Yeild per Plot (lbs)
Yeild per Plot (lbs)
100
BC
CD
60
D
40
50
40
30
20
10
20
0
None
0
None
Methyl Bromide
Methyl Iodide
Methyl Bromide
Methyl Iodide
Three Way
Three Way
Figure 23. Comparison of pepper yields for
various fumigants and mulches. Ponder Farm
Fall 2006.
Figure 21. Comparison of pepper yields for
various fumigants and mulches. Tifton
Vegetable Park Spring 2006.
Conclusions
The use of higher permeability
mulch plastics can reduce the amount of
gas fumigants released to the atmosphere
and increase the amount of contact time
with the soil. Growers need to be
cautious of transplant stunting when
using the mulches with higher
permeability.
References
Noling, J.W. 2002. Reducing Methyl
Bromide Application Rates with
Plastic Mulch Technology.
Entomology and Nematology
Department, Florida Cooperative
Extension Service, Institute of
Food and Agricultural Sciences,
University of Florida. ENY-046.
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