Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2002
Publication Date: 10/1/2003
Citation: Bryson, C.T., Reddy, K.N., Molin, W.T. 2003. Purple nutsedge (Cyperus rotundus) population dynamics in narrow row transgenic cotton (Gossypium hirsutum) and soybean (Glycine max) rotation. Weed Technology. 17:805-810. Interpretive Summary: Purple nutsedge is considered to be the world's weed. It is one of the most troublesome and difficult to control non-native, invasive weeds in row crops, lawns, pastures, and other areas of the southern United States. Research conducted at Stoneville,MS, determined that purple nutsedge populations can be effectively reduced in glyphosate-based, narrow-row cotton and soybean production systems and that purple nutsedge population reduction is greater when in continuous soybean or when cotton and soybean were rotated than in continuous cotton production systems. These results are important because purple nutsedge populations, interference with crop production, and cost of herbicide inputs can be reduced in glyphosate-based, narrow-row cotton and soybean production systems.
Technical Abstract: A 4-yr field study was conducted during 1998 through 2001 at Stoneville, MS, to determine the effects of narrow-row transgenic cotton and soybean rotation on purple nutsedge populations and crop yield. Crop rotations over the 4 years included [cotton (C) and soybean (S)] CCSS, CSCS, SCSC, SSCC, and continuous cotton (CCCC) and soybean (SSSS) all with herbicide programs that were glyphosate-based, non-glyphosate-based, or no purple nutsedge control (NPNC). Purple nutsedge populations and shoot dry biomass were reduced in cotton and soybean rotation and continuous soybean by 72 and 92%, respectively; whereas in continuous cotton, purple nutsedge populations increased by 67% and shoot dry biomass reduced by 32% after 4 years. Reductions in purple nutsedge populations also occurred in soybean when cotton was rotated with soybean (CSCS and SCSC) compared with continuous cotton. Among herbicide programs, the glyphosate-based program was more effective in reducing purple nutsedge populations compared with non-glyphosate-based program. Seed cotton yield was greater when following soybean (SCSC) than with cotton following cotton (CCCC, CCSS) in 1999. However, seed cotton yields were similar regardless of crop rotation systems in 2000, and 2001. Seed cotton yields were equivalent between the glyphosate-based and non-glyphosate-based programs in 1999 and 2001. In 1999-2001, seed cotton yields were reduced by 62 to 85% in NPNC compared with yields in glyphosate- and non-glyphosate-based programs. Soybean yields were unaffected by crop rotation systems in all of 4 years. Among herbicide programs, non-glyphosate-based program in all 4 years and glyphosate-based program in 1999 and 2000 gave higher soybean yield compared with NPNC. After 4 years of rotation, tubers per soil core (9.5-cm diameter and 15.2 cm deep) in fall 2001 and plant density in spring 2002 were highest in continuous cotton and lowest in continuous soybean. Both herbicide programs reduced tubers per core and plant density compared with NPNC, and the glyphosate-based program was more effective than the non-glyphosate-based program. These results showed that soybean competes with purple nutsedge better than cotton. In cotton production, severe infestations of purple nutsedge can be managed by rotating cotton with soybean and/or using glyphosate-based herbicide program in glyphosate-resistant cotton.