not on ZnP, but...biochervSeptember 30 2012, 13:35:22 UTC
BEHAVIOUR OF FUMIGANTS IN SOIL. H. Ajwa and A. Minuto. Department of Plant Sciences University of California, Davis, 1636 East Alisal St. Salinas, CA 93905, USA. Email: haajwa@ucdavis.edu Methyl bromide use for soil disinfestation has been phased out in most developed countries and is becoming restricted in developing countries. Several fumigants (1,3-dichloropropene, chloropicrin,iodomethane, propargyl bromide, sodium azide, dimethyl disulfide, and methyl isothiocyanate generators such as metam sodium and dazomet) have been proposed to replace methyl bromide. Due to its very high vapor pressure and low boiling temperature, methyl bromide converts immediately into gas when shankinjected into the soil. The high volatility and biological reactivity of methyl bromide make it the most versatile fumigant. Iodomethane also has a low boiling point and high vapor pressure and is more biologically reactive than methyl bromide on a molar basis. Iodomethane is not an ozone-depleting chemical because it degrades readily in the atmosphere by photolysis. Except for iodomethane, the other available alternative fumigants have low vapor pressure and high boiling temperatures and do not volatilize and dissipate in soils like methyl bromide. Therefore, effective control of soilborne pathogens and weeds requires more specialized application equipment and methods to achieve good distribution of fumigants across the target soil profile. Concerns over emissions and risk to human and environmental health have prompted the development of new formulations and application techniques such as drip application of combinations of fumigants. This presentation will summarize fumigant physicochemical properties and environmental fate.
Re: not on ZnP, but...biochervSeptember 30 2012, 13:36:51 UTC
GLOBAL PHASEOUT OF METHYL BROMIDE UNDER THE MONTREAL PROTOCOL: IMPLICATIONS FOR THE OZONE LAYER, BIOPROTECTION AND BIOSECURITY. I. Porter, J. Banks, S. Mattner and P. Fraser. Technology and Economic Assessment Panel, Montreal Protocol CA, Australia. Email: ian.j.porter@dpi.vic.gov.au The Montreal Protocol has been very effective in reducing the major ozone-depleting product, methyl bromide (MB), and represents an excellent model for future phaseout of environmentally damaging products, such as those involved with climate change. Over a ten year period, 85% of MB (c. 45,000 t) used for preplant soil fumigation has been phased out and a wide range of other products and technologies adopted for disease and weed control in agriculture. Restrictions on the use of MB have stimulated new knowledge on the importance and relationships between microbial diversity and crop growth, and improved our understanding of soil health and the development of new products and production systems to produce futures food without the impact of harsh pesticides. This has led to increased use of substrate systems, grafting and plant resistance for disease control thus avoiding the need for soil disinfestation, and the use of alternative products, such as 1,3- dichloropropene/chloropicrin (Pic), metham, methyl iodide/Pic, drip applied fumigants and barrier films as alternatives strategies for soil disinfestation. Implementation of these alternatives has led to a 45% fall in bromine in the troposphere and 30% reduction in effective chlorine load in the stratosphere. Internationally, pressure is mounting to restrict use of all fumigants worldwide (EC Reg 2037 and US Cluster Analysis) and this will further stimulate new technologies for plant disease control. Pressure is also mounting to restrict MB use for quarantine and pre-shipment (QPS) with QPS MB use exceeding 14,000 t in 2005. Industries need to be prepared for adoption of new crop protection, biosecurity and IPM management strategies.
Davis, 1636 East Alisal St. Salinas, CA 93905, USA. Email: haajwa@ucdavis.edu
Methyl bromide use for soil disinfestation has been phased out in most developed countries and is becoming restricted in developing countries. Several fumigants (1,3-dichloropropene, chloropicrin,iodomethane, propargyl bromide, sodium azide, dimethyl disulfide, and methyl isothiocyanate generators such as metam sodium and dazomet) have been proposed to replace methyl bromide.
Due to its very high vapor pressure and low boiling temperature, methyl bromide converts immediately into gas when shankinjected into the soil. The high volatility and biological reactivity of methyl bromide make it the most versatile fumigant. Iodomethane also has a low boiling point and high vapor pressure and is more biologically reactive than methyl bromide on a molar basis.
Iodomethane is not an ozone-depleting chemical because it degrades readily in the atmosphere by photolysis. Except for iodomethane, the other available alternative fumigants have low vapor pressure and high boiling temperatures and do not volatilize and dissipate in soils like methyl bromide. Therefore, effective control of soilborne pathogens and weeds requires more specialized application equipment and methods to achieve good distribution of fumigants across the target soil profile. Concerns over emissions and risk to human and environmental health have prompted the development of new formulations and application techniques such as drip application of combinations of fumigants. This presentation will summarize fumigant physicochemical properties and environmental fate.
Reply
The Montreal Protocol has been very effective in reducing the
major ozone-depleting product, methyl bromide (MB), and represents
an excellent model for future phaseout of environmentally
damaging products, such as those involved with climate change.
Over a ten year period, 85% of MB (c. 45,000 t) used for preplant
soil fumigation has been phased out and a wide range of other
products and technologies adopted for disease and weed control in
agriculture. Restrictions on the use of MB have stimulated new
knowledge on the importance and relationships between microbial
diversity and crop growth, and improved our understanding of soil
health and the development of new products and production systems
to produce futures food without the impact of harsh pesticides.
This has led to increased use of substrate systems, grafting
and plant resistance for disease control thus avoiding the need for
soil disinfestation, and the use of alternative products, such as 1,3-
dichloropropene/chloropicrin (Pic), metham, methyl iodide/Pic,
drip applied fumigants and barrier films as alternatives strategies
for soil disinfestation. Implementation of these alternatives has led
to a 45% fall in bromine in the troposphere and 30% reduction in
effective chlorine load in the stratosphere. Internationally, pressure
is mounting to restrict use of all fumigants worldwide (EC Reg
2037 and US Cluster Analysis) and this will further stimulate new
technologies for plant disease control. Pressure is also mounting to
restrict MB use for quarantine and pre-shipment (QPS) with QPS
MB use exceeding 14,000 t in 2005. Industries need to be prepared
for adoption of new crop protection, biosecurity and IPM management
strategies.
Reply
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