IMPACT OF TILLAGE AND HERBICIDES ON WEED DENSITY AND SOME PHYSIOLOGICAL TRAITS OF WHEAT UNDER RICE-WHEAT CROPPING SYSTEM

To evaluate the impact of various tillage systems in combination with herbicides on weed density and some physiological traits under rice-wheat cropping system, an experiment using a winter wheat (Triticum aestivum L.) cultivar “Nasir 2000” was conducted in arid region of Khyber Pakhtunkhwa, Pakistan during 2007–2009 growing seasons. The experiment was laid out in randomized complete block design with split plot arrangements replicated four times. The treatments comprised of 3 tillage treatments, including conventional tillage with deep ploughing through disk plough (CT), reduced tillage with shallow ploughing through rotavator (RT), and zero tillage with stubble direct drilling (ZT) as main plots while five weed control treatments viz. 2,4-D ester @ 1.25 L ha^-1, Puma super 75 EW @1.25 L ha^-1, 2,4-D + Puma super @1.25 L ha^-1 each, Affinity 50 WDG @ 2 kg ha^-1 and weedy check as subplots. Herbicides had significant effect on weed density, fresh and dry weed biomass (FWB DWB), leaf area tiller^-1 (LAT^-1), leaf area index (LAI), plant height, grains spike^-1, and grain yield. Tillage x herbicides interaction was significant for weed density and grain yield only. Maximum LAT^-1 (141 cm^2), LAI (3.4), plant height (88.2 cm), grains spike^-1 (72.4) and grain yield (6906.9 kg ha^-1) were recorded with Affinity. Maximum weed density m^-2 (75.5), FWB (845.3 g m^-2) and DWB (220.4 g m^-2) were recorded in weedy check. Maximum grain yield (5583.8 kg ha^-1) was obtained from RT being statistically similar to grain yield (5575.1 kg ha^-1) in ZT. The lower grain yield (5479.3 kg ha^-1) in CT was due to maximum weed density m^-2 (48.3), FWB (536.6 g m^-2) and DWB (136.5 g m^-2). Affinity was the most effective herbicide against grasses as well as broad-leaved weeds in combination with either ZT or RT and resulted in higher grain yield. ZT and RT in conjunction with affinity are recommended for significantly reducing weeds population and enhancing wheat yield under rice-based cropping system.