SOIL TYPE & TEMPERATURE AFFECT ACTIVITY OF METAM-SODIUM:

• In soil, metam-sodium (MS) is converted to methyl isothiocyanate (MIT) which is nematicidal
• Conversion is usually completed within a few hours
• Conversion is faster in finer textured soils.
• Conversion is faster at higher temperatures
• Half-life in soil varys from a few days to a few weeks
• Nematicidal activity decreases more rapidly in finer textured soils
• Nematicidal activity decreases more rapidly at higher temperatures

Products containing metam-sodium (MS) first became available for testing in the 1950's. At the present time, the product is manufactured by several companies and sold under several names including Vapam, Metam, Soil Prep, Sectagon, and Busan. Before MS becomes nematicidal, it must first be converted to methyl isothiocyanate (MIT). The rate at which this conversion occurs is affected by soil texture and temperature as summarized in this table.

In practical use, MS products are frequently applied in irrigation water or followed by irrigation to move the product through the soil. Research has shown that it is possible to move MS through the root zone faster than it is able to convert to MIT thus resulting in ineffective control in upper soil layers.

In general, the more rapid the conversion, the more rapidly the nematicidal activity decreases in a particular situation.

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