WEED EMERGENCE FROM TWO SOILS AT VARIOUS MOISTURES TEMPERATURES AND DEPTHS

Under controlled conditions in a growth chamber, emergence of tumblegrass (Schedonnardus paniculatus (Nutt) Trel.), redroot pigweed (Amaranthus retroflexus L.), and barnyardgrass (Echinochloa crusgalli (L.) Beauv.) was best with an 8-hr. night temperature of 65 F and a 16-hr. day temperature of 80 F. Other temperature ranges, in order of decreasing effectiveness in stimulating emergence, were 80-95, 50-65, and 35-50 F. Best emergence occurred at the 1/2-in depth of planting followed by 1/4, 1,2, and 4 in. Barnyardgrass was the only weed that emerged appre- ciably from the 4-in depth. Average emergence was better on a coarse-textured soil than on a fine-textured soil. Under dry soil conditions, emergence was reduced by soil crusting.