Weed Control and Yield Comparisons of Glyphosate- and Glufosinate-Resistant Corn Grown in Rotation

Abstract

Information on long-term glyphosate- and glufosinate-resistant corn (Zea mays L.) production on weed control and rotation benefits is lacking. A six-year field study was conducted from 2004 to 2009 at Stoneville, MS, to examine the effects of rotating glyphosate-resistant and glufosinate-resistant corn under reduced tillage conditions on weed control, soil weed seedbanks, and yield. The four rotation systems were glyphosate-resistant and glufosinate-resistant corn grown continuously and in rotation with two herbicide programs, post-emergence-only herbicides (POST) and preemergence herbicides followed by POST (PRE + POST). Control of 13 predominant weed species in glyphosate-resistant and glufosinate-resistant corn was >95%, regardless of herbicide program, with the exception of johnsongrass and yellow nutsedge, both perennial weeds. Johnsongrass and yellow nutsedge control was lower in the continuous glufosinate-resistant corn system compared with other rotation systems. Yellow nutsedge control was higher with the PRE + POST (89% to 99%) compared with the POST-only (72% to 86%) treatment. Corn yields were similar regardless of rotation when a corn cultivar stacked with both glyphosate-resistant and glufosinate-resistant traits was used. The PRE + POST program gave 5% to 10% higher yield than the POST-only program in four of six years. The seedbank for yellow nutsedge and predominant grass and broadleaf weeds was not significant among the four rotation systems. Seedbanks for grasses and yellow nutsedge were higher in the POST-only program (20.5 and 1.8 per core of 678 cm3, respectively) compared with the PRE + POST program (9.5 and 0.4 per core, respectively). These results indicate that johnsongrass and yellow nutsedge control could be reduced in continuous glufosinate-resistant corn and could be mitigated by rotating with glyphosate-resistant corn.