Comparison of Weed Control, Yield, and Net Income in Conventional, Glyphosate-Resistant, and Glufosinate-Resistant Soybean

Separate field experiments were conducted in central and southeast Missouri during 2009 and 2010 to evaluate the effect of preemergence (PRE) and postemergence (POST) herbicide programs on Palmer amaranth (Amaranthus palmeri S. Wats.) and waterhemp (Amaranthus rudis Sauer) control, soybean [Glycine max (L.) Merr.] yield, and net income in conventional, glyphosate-resistant, and glufosinate-resistant soybean production systems. Visual control evaluations 10 wk after emergence at the waterhemp site revealed that all preemergence only applications (PRE-only) and preemergence followed by a postemergence applications (PRE fb POST) provided greater than 92% waterhemp control in either soybean system and at the Palmer amaranth site and all PRE-only provided greater than 83% Palmer amaranth control across soybean systems. Averaged across all herbicide programs at both locations, glufosinate-resistant soybean provided the highest grain yield and net return followed by glyphosate-resistant and conventional soybean systems. Furthermore, with the exception of the conventional PRE-only program at the waterhemp site, all glyphosate-resistant soybean herbicide programs provided greater net return than all conventional herbicide programs. Collectively, the results from both trials indicate that programs containing PRE herbicide treatments provide the best opportunity for season-long control of waterhemp and Palmer amaranth and highest grain yields and net returns in conventional, glyphosate-resistant, or glufosinate-resistant soybean systems. The results from these experiments also suggest that Palmer amaranth may be particularly difficult to control in conventional soybean systems.