Residue Removal Method and Herbicides for Tall Fescue Seed Production: I. Weed Control

Abstract

AbstractPacific Northwest grass seed production is in transition from reliance on open‐field burning to new systems integrating chemical weed control with mechanical removal of crop residues. Field tests were initiated in 1989 to ascertain if these systems can meet seed trade expectations for genetic purity while maintaining normal seed yields. Fourteen herbicide treatment sequences plus an untreated check were evaluated under five residue removal methods at two sites during two consecutive growing seasons. Residue removal included two methods of burning and three nonburn systems varying in thoroughness of removal. Acceptable control (>90% reduction in ground cover) of volunteer seedling tall fescue (Festuca arundinacea Schreb.), the most abundant weed in all tests, was achieved by nearly all herbicide treatments at one site. At the other site, however, thorough residue removal or aggressive herbicide treatments were required to achieve this same degree of control. Over sites and years, acceptable control without use of herbicides was achieved in one case out of four for the most thorough mechanical residue removal system (vacuum‐sweep, VS) and twice by open‐field burning (FB). Preemergence (PRE) application of pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] provided acceptable control following VS, FB, and propane flaming (PP). Oxyfluorfen [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl)benzene] applied postemergence (POST) at 0.28 kg a.i. ha−1 plus diuron [N′‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea] at 2.7 kg a.i. ha−1 controlled weeds in all residue removal methods at one site, and for VS, FB, and PP at the other site. Applied in sequence after each of four PRE herbicides, POST application of 0.14 kg ha−1 oxyfluorfen plus 1.8 kg ha−1 diuron controlled volunteer seedling tall fescue better than POST application of 2.7 kg ha−1 diuron without oxyfluorfen. With properly chosen herbicide treatments, seed trade standards for tall fescue can be met without field burning.