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Seed Viability and Dormancy of 17 Weed Species after 9.7 Years of Burial in Alaska

A 50-year study at Fairbanks, AK, was started in 1984 to determine soil seed longevity of 17 weed species. Seed were buried in mesh bags 2 and 15 cm deep and were exhumed 0.7, 1.7, 2.7, 3.7, 4.7, 6.7, and 9.7 yr later. Viability was determined by germination and tetrazolium tests. All common hempnettle and quackgrass seed were dead after 2.7 and 3.7 yr, respectively. Less than 1% of wild oats and foxtail barley seed were viable after 3.7 yr, but > 6.7 yr were required for loss of all viability. By 9.7 yr, < 1% seed viability remained for: bluejoint reedgrass, corn spurry, pineappleweed, prostrate knotweed, and wild buckwheat From 2 to 5% of seed from common chickweed, common lambsquarters, flixweed, Pennsylvania smartweed, rough cinquefoil, marsh yellow-cress and shepherd's-purse were viable, while 62% of American dragonhead seed was still alive. Seed longevity in agricultural fields is not greater under subarctic conditions than under warmer conditions.