| Summary: | A field experiment was carried out at Tobacco Research Station Khan Ghari, Mardan, (NWFP)- Pakistan during spring 2003 to study the impact of herbicides on some agronomic and chemical characteristics of flue-cured virginia (FCV) tobacco (Nicotiana tabacum L.). The experiment was laid out in RCB design, replicated four times with ten treatments, comprising hand weeding, weedy check, pre-transplanting herbicides; S-metalocholar @ 1.92, pendimethalin (EC) @ 1.00, pendimethalin (CS) @ 1.00, and butralin @ 1.44 kg a.i ha-1 and the post-transplanting herbicides include; clodinafop @ 0.04, fenoxaprop-p-ethyl @ 1.00, acetochlor @ 0.125 and glyphosate @ 0.95 kg a.i ha-1. None of the herbicides except S-metalocholar had a phytotoxic effect on tobacco. All the parameters except the number of leaves plant-1 were significantly affected by different treatments. The highest (228.3) weeds density m-2 was observed in weedy check while minimum (69) was recorded in pendimethalin (EC) treatment. The maximum grade index of 74.60% was recorded in acetochlor and minimum grade index of 53.88% was recorded in S-metalocholar treatments. Nicotine (%) was higher in pendimethalin (EC) treated plots with 2.362%; however it was comparable to all other treatments. The maximum percent reducing sugar of 18.22% was recorded in pendimethalin (CS) treatment, while minimum of 12.42% reducing sugar was recorded in weedy check. Similarly maximum yield of 2465 kg ha-1 was recorded in pendimethalin (EC) treatment and minimum yield of 1703 kg ha-1 was recorded in weedy check (control) treatment. Thus it can be concluded from the experiment that herbicides proved effective against weeds and their growth and promoted tobacco quality and yield. Hence the use of herbicides not only increases the net income of the farmers but also will make the weed seed bank poorer.
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