Effect of tillage and tank-mix herbicide application on weed management in soybean (Glycine max)

A field experiment was carried out at the Indian Agricultural Research Institute during 2010 and 2011 to investi- gate the effect of tillage and tank-mix herbicide application on growth, yield, nutrient uptake and protein content of soybean [Glycine max (L.) Merrill]. It was observed that conventional (CT) and no (NT) tillage systems resulted in comparable weed density and dry weight and soybean seed yield during both years except 2010, when NT re- sulted in significantly lower weed density. Tank-mix pre-emergence application of pendimethalin 0.5 kg/ha + imazethapyr 0.075 kg/ha was next to weed-free check and superior to all other weed control treatments on the re- duction of weed density in both years, but, with respect to reduction in weed dry weight, it was comparable with pendimethalin 0.5 kg/ha + hand weeding, which resulted in the lowest weed dry weight after weed-free check. Ni- trogen, P and K uptake by soybean seed was comparably higher in weed-free check and tank-mix pre-emergence application of pendimethalin 0.5 kg/ha + imazethapyr 0.075 kg/ha in both years. Conversely, N, P and K uptake by weed was significantly higher in weedy check, and the lowest amount of these nutrients after weed-free check was observed in pendimethalin 0.5 kg/ha + imazethapyr 0.075 kg/ha. All weed control measures resulted in signifi- cantly higher soybean seed yield compared to weedy check, but the tank-mix pre-emergence application of pendimethalin 0.5 kg/ha + imazethapyr 0.075 kg/ha resulted in considerably higher seed yield over others in both years.