lower doses of pendimethalin mixed with allelopathic crop water extracts for weed management in canola (Brassica napus)

Injudicious use of synthetic herbicides has resulted in environmental pollution, soil contamination, development of resistance among weed biotypes and threats to human health, which necessitate finding alternative weed management strategies to reduce the use of herbicides. This study was conducted to investigate the possibilities of reducing pendimethalin dosage by tank mixing with allelopathic crop water extracts for weed control in canola (Brassica napus L.). Allelopathic crop water extracts including sorghum (Sorghum bicolor L.), sunflower (Helianthus annuus L.), mustard (Brassica campestris L.) and rice (Oryza sativa L.) each at 15 L ha^-1 were tank mixed with 0.4 and 0.6 kg active ingredient (a.i.) ha^-1 pendimethalin and sprayed immediately after sowing. Control (weedy check) and standard dose of pendimethalin 1.2 kg (a.i.) ha^-1 were used for comparison. Data regarding weed density, weed fresh weight, weed dry weight and yield components was recorded. Horse purslane (Trianthema portulacastrum L.), purple nutsedge (Cyperus rotundus L.), lambsquarters (Chenopodium album L.) and swine cress (Cronopus didymus L.) were the weeds present in the experimental field. Weed density, weed fresh weight and dry weight were lower than control in all the treatments; however the performance of various combinations of allelopathic crop water extracts and lower pendimathalin rates was better than the standard dose of herbicide particularly in case of purple nutsedge (C. rotundus L.). All the yield contributing parameters including number of branches per plant, number of pods per plant, numbers of seeds per pod and 1000-seed weight were higher, where combinations of allelopathic extracts were used with lower herbicide rates. In crux, pendimethalin dose for successful weed control in canola can be reduced up to 67% for environmental safety.