Cryogens are defined as substances that produce low temperatures. In this study, cryogens refer to salts added to snow or ice to cool underlying soil, resulting in reduced weed establishment. In laboratory experiments, bags of ice mixed with cryogens were able to reach temperatures as low as −17 C. In soil-filled pots stored at 4 C, bags of cryogenic salts filled with ice chips reduced the soil temperatures to below 0 C and reduced the establishment of weeds significantly without salinity effects. The cryogen magnesium chloride-6-hydrate (MC) that was effective in pot experiments was tested in an oat field in 2008 and 2009. Plastic bags containing concentrated solutions of MC, perforated at the top, were placed on bare soil just before snowfall. Contact of snow with MC was expected to decrease the surface soil temperature enough to cause freezing injury to seeds in the soil. Although overall effects on weed establishment were small, the cryogenic effect did significantly reduce corn spurry establishment in 2008, and significantly reduced overall weed establishment in both years. These results show that weed management with cryogenic salts is possible in principle, but requires further technical improvements to be practical in the field.

Nomenclature: Corn spurry, Spergula arvensis var. sativa (Boenn.) Mert. & Koch.; oat, Avena sativa L.