Depletion of the weed seed bank by stimulating germination during winter months and subsequently exposing the seedlings to adverse air temperatures is a possible means of controlling weeds in small-scale horticultural operations. Johnsongrass [Sorghum halepense (L.) Pers.], hemp sesbania [Sesbania exaltata (Raf.) Rydb. ex A.W. Hill], and barnyardgrass [Echinochloa crus-galli (L.) Beauv.] were seeded in soil trays and maintained for 4 days at 4 or -12 °C, then heated to 32 °C for 4 days using electric heating pads. Germination percentages, after heating soils, were: 55% and 70% for hemp sesbania, 82% and 72% for barnyardgrass, and 45% and 55% for johnsongrass, respectively; for seeds kept at -12 and 4 °C, respectively. Subsequent exposure of seedlings to -12 °C for 7 days killed all seedlings, while exposure to 4 °C killed only 18% to 28%. The temperature regimes of -12 °C for 4 days, and 32 °C for 4 days followed by -12 °C killed 95%, 78%, and 68% of the johnsongrass, hemp sesbania, and barnyardgrass, respectively.
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