Efficacy of different herbicides for controlling weeds in onion in higher altitudes

To study the efficacy of different herbicides for controlling weeds in onion (variety Swat-1), an experiment was conducted at Agriculture Research Station (North), Mingora during rabi 2003-04, using Randomized Complete Block (RCB) design, having eight treatments and four replications. The treatments were seven herbicides including pendimethalin @ 1.32, trifluralin @ 1.2, s-metolachlor @ 1.92 kg ha-1 used as pre-emergence, while post-emergence herbicides were 2,4-D @ 1.13, bromoxynil + MCPA @ 1.3, clodinafop @ 0.05 kg ha-1 and terbutryn + triasulfuron @ 0.3 kg a.i ha-1 and a weedy check. The effect of all these herbicides was studied on weeds kill percentage, fresh weed biomass (kg ha-1), size of onion bulbs (ml), onion bulbs m-2, plant height (cm), onion diameter (cm), onion yield (kg ha-1) and cost-benefit ratio. The parameters that significantly affected by different herbicides were weed kill percentage, size of onion bulbs (ml), onion diameter (cm) and onion yield (kg ha-1). Maximum weeds kill percentage (88.6 %), size of onion bulbs (78.25 ml), onion diameter (5.49 cm) and onion yield (29950 kg ha-1) were recorded in pendimethalin treatment as compared to weedy check 00.0 %, 47.75 ml, 4.06 cm and 13700 kg ha-1, respectively. The cost-benefit ratio was also highest (1:29.81) in pendimethalin followed by s-metolachlor (1:19.32) and trifluralin (1:17.05) while, it was the lowest was in terbutryn + triasulfuron (1:3.90). It is concluded that the performance of pendimethalin was the best among all the herbicidal treatments followed by s-metolachlor. Therefore, pendimethalin is recommended @ 1.32 kg a.i. ha-1 for significantly reducing the weeds population and enhancing the bulb yield in onion.