Effects of Green Foxtail and Lamb’s-Quarters Interference in Field Corn

Field experiments were conducted to study the effects of full season interference of various densities of green foxtail (Setaria viridis (L) Beauv. ) and lamb’s-quarters (Chenopodium album L. ) on the yield of field corn. Green foxtail interference was studied at densities of 0, 29, 56, 89 and 129 plants/m 2 in 1976 and 0, 20, 40, 62, 84 and 119 plants/m 2 in 1977. Non-significant (P = 0. 05) corn yield reductions were obtained at densities of 56 and 20 plants/m 2 in 1976 and 1977, respectively. Increased green foxtail density reduced corn yields by 5. 8–17. 6% in 1976 and 5. 6–16% in 1977. Lamb’s-quarters interference was tested at densities of 0, 46, 83, 112, 167 and 221 plants/m 2 in 1976 and 0, 54, 109, 172, 208 and 277 plants/m 2 in 1977. Corn yields were not reduced significantly at lamb’s-quarters densities of 46 and 109 plants/m 2 in 1976 and 1977, respectively, compared to weed-free treatments. Yield reductions from 12. 3–37. 9% in 1976 and 6–58% in 1977. The competitive effects of green foxtail and lamb’s-quarters on corn yield differed mainly on the ability of the latter to reduce ear and seed size.