A field experiment were conducted for two years at Agricultural Research Station, Bhavanisagar of Tamil Nadu Agricultural University, during kharif season of 2009 and 2010 to evaluate the new formulation of oxyfluorfen (23.5% EC) on weed control in onion. Weeds constitute one of the biggest problems in agriculture that not only reduce the yield and quality of onion but also utilize essential nutrients. Hence, weed control is essential for increasing onion production. Based on two years field experimentation, it was found that pre-emergence application of oxyfluorfen (23.5% EC) at400 g^.ha^-1 gave significantly lower total weed density, weed dry weight and higher weed control efficiency at all the intervals. Application of new formulation of oxyfluorfen (23.5% EC) at200 g^.ha^-1 as pre-emergence herbicide can keep the weed density and dry weight below the economic threshold level and increase the bulb weight (42.56 and43.87 g) and yield (15940 and15610 kg^.ha^-1) in onion. Unweeded control accounted for lower bulb yield which inturn reflected through higher weed index of 60.6 and 56.1 per cent, respectively during both the years, due to heavy competition of weeds for nutrients, space and light.

Cotton is one of the important crops that have been genetically altered to address challenges with weed and insect control. The research was conducted with glyphosate resistant cotton hybrids during winter irrigated season of 2009-10 and 2010-11 at the experimental site of Tamil Nadu Agricultural University, Coimbatore, with the objective, to find out the weed control efficacy and yield of transgenic cotton hybrid with the application of glyphosate. Glyphosate was applied as post-emergence application on 25 and 65 DAS at 900, 1350, 1800, 2700, 3600 and 5400 g a.e./ha in MRC 7347 BG-II RRF test hybrid. These treatments were compared with hand weeding on 15 and 30 DAS and unweeded control. In both sprays, post-emergence application of glyphosate 2700, 3600 and 5400 g a.e./ha registered lower weed density and higher weed control efficiency in transgenic cotton hybrid compared with other treatments. Seed cotton yield (3195 and 3092 kg·ha -1 during 2009-10 and 2010-11 respectively) was significantly higher in post-emergence application of glyphosate at 2700 g a.e./ha. Increased use of transgenic cotton with herbicide and pest resistance has resulted in more efficient insect and weed management practices.

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Weeds are posing a serious problem in maize. The congenial climatic conditions encourage more weed growth in the widely spaced crop like maize and cause yield reduction to the tune of 29 to 70 percent. A field experiment was conducted for two years at Tamil Nadu Agricultural University, Coimbatore during kharif seasons of 2010 and 2011 to evaluate the weed management options for transgenic stacked (TC 1507 & NK 603) and conventional maize hybrids. The experiments were conducted with the following objective to evaluate the weed control efficiency and crop productivity with K salt of glyphosate formulations under field conditions. Treatments consisted of two transgenic stacked hybrids named 30V92 and 30B11 applied with glyphosate as early post emergence at 900 and 1800 g a.e ha -1 during kharif, 2010 and conventional maize hybrids named 30V92 and 30B11 applied with glyphosate by controlled droplet application method at 900, 1350 and 1800 g a.e ha -1 during kharif, 2011 compared with non transgenic counterpart maize hybrids applied with pre emergence atrazine at 0.5 kg ha -1 followed by one hand weeding on 40 DAS with and without insect management. Based on the two years field experimentation, it was found that early post emergence application of glyphosate at 1800 g a.e ha -1 gave significantly lower weed density, weed dry weight and higher weed control efficiency at all the intervals. Higher grain yield was registered with post emergence application of glyphosate at 1800 g a.e ha -1 in transgenic and conventional maize hybrid of 30V92 (12.21 t ha -1 and 11.23 t ha -1 ) during both seasons of the study. Unweeded control accounted for grain yield which in turn reflected through higher weed index of 58.39 and 57.26 per cent, respectively during both the years, due to heavy competition of weeds for nutrients, space and light.

A field experiment was carried out at Tamil Nadu Agricultural University, Coimbatore during kharif seasons of 2010 and 2011 to study the effect of Glyphosate on weed management and grain yield in kharif maize of transgenic stacked and conventional maize hybrid. This investigation was conducted with the following objectives to evaluate the weed control efficiency and crop productivity with K salt of glyphosate formulations under field conditions. Treatments consisted of two transgenic stacked hybrids named 30V92 and 30B11 applied with glyphosate as early post emergence at 900 and 1800 g a.e ha -1 during kharif season of 2010 and conventional maize hybrids named 30V92 and 30B11 applied with glyphosate by controlled droplet application method at 900, 1350 and 1800 g a.e ha -1 during kharif season of 2011 compared with non-transgenic counterpart maize hybrids applied with pre emergence atrazine at 0.5 kg ha -1 followed by one hand weeding on 40 days after sowing (DAS) with and without insect management. Among the treatments, early POE application of glyphosate at 1800 g a.e ha -1 registered lower weed density and higher weed control efficiency in transgenic and non-transgenic maize hybrids at all the intervals. Higher grain yield was registered with post emergence application of glyphosate at 1800 g a.e ha -1 in transgenic and non transgenic maize hybrid of 30V92 during both the kharif seasons