Field and greenhouse studies were conducted in 1995 and 1996 in Kansas to determine the efficacy of 21 herbicide treatments for control of tumble pigweed, Palmer amaranth, redroot pigweed, and two biotypes of common waterhemp in soybean. In field studies, nine of eleven preemergence treatments controlled all four species 90% or more. However, pendimethalin and trifluralin controlled Palmer amaranth, redroot pigweed, and tumble pigweed less than the other preplant incorporated and preemergence treatments. With the exception of flumiclorac and NAF-75, postemergence treatments controlled 75 to 90% of all four species. A biotype of common waterhemp collected in Iowa was not controlled by acetolactate synthase-inhibiting herbicides. Greenhouse results were similar to field experiments. Results suggest at least 90% control of theseAmaranthusspecies is possible with proper herbicide selection.

Studies were conducted to determine the effects of scarification, temperature, osmotic potential, and pH on seed germination of buffalo gourd and to examine seedling emergence and establishment. Mechanical and chemical scarification did not increase germination compared to non-scarified seed. Seed germinated at constant temperatures in the dark from 15 to 37 C with optimum germination at 25 C. As osmotic potentials became more negative from −0.1 to −0.8 MPa, germination decreased from 77 to 53%. Germination increased from 15% at pH 2.2 to 90% at pH 8. Seedlings were able to emerge from depths as great as 12 cm, and plants younger than 19 d were not able to sprout from the roots when the shoots were removed.