Vegetation control for no-tillage corn planted into warm-season perennial species

The success of no-tillage corn (Zen mays L.) planted into sod in the Southe ast depends on control of warm-season perennials. Preemergence (PRE) and po stemergence (POST) herbicides were evaluated for control of warm-season per ennial and annual species in no-tillage corn production, Vegetation spectru m differences at the various Locations influenced both herbicide rate and t iming of application required for 90% control by imazapyr {(+/-)-2-[4,5-dih ydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-pyridinecarboxyli c acid}, imazethapyr {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-im idazol-2-yl]-3-pyridinecarboxylic acid, imazethapyr 2-[4,5-dihydro-4-methyl -4-(1-methylethyl)-5-oxo-1 H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic ac id}, glufosinate [2-amino-4-(hydroxymethylphosphinyl) butanoic acid], or im azapyr + imazethapyr. Imazapyr controlled established bermudagrass (Cynodon dachtylon L.), broomsedge (Andropogon virginicus L.), johnson-grass [Sorgh um halepense (L.) Pers.], tall fescue (Festuca arundinacea Schreb.), and da llisgrass (Paspalum dilatatum Poir.) in all instances. Several herbicides w ere used in selected combinations for PRE and/or POST applications in discr ete rate trials, These were imazapyr, imazethapyr, glufosinate, imazapyr imazethapyr, paraquat (1, 1'-dimethyl-4,4'-bipyridinium ion), atrazine [6-c hloro-N-ethyl-N-1-(1- methylethyl)-1,3,5-triazine-2,4-diamine], and glyphos ate [N-(phosphonomethyl)glycine]. The glufosinate-resistant corn hybrid in 1997 at Holly Springs, MS, with glyphosate PRE at 0.84 kg a.i. ha(-1) follo wed by glufosinate POST (28 DAP) at 0.45 kg ha(-1) produced a maximum yield of 10.2 Mg ha(-1). Results from this study indicate that vegetation can be controlled for corn production in untilled sod comprised of warm-season pe rennials when transgenic hybrids are grown.