use of false seedbed and reduced doses of imazethapyr for weed management in common bean (phaseolus vulgari l.)

experiment was conducted in 2011 to evaluate the efficacy of reduced herbicide rates in combination with false seedbed for selective weed control in common bean. the experiment was carried out with a completely randomized factorial design. factors were herbicide dose (post-emergence application of imazethapyr at the rates of 0, 25, 50, 75, and 100 g a.i. ha-1) and seedbed preparation (false seedbed and conventional seedbed). a hand weeding control was also included as check. in the absence of herbicide, there were significant differences in grass and total weeds biomass between two seedbeds (p< 0.01), however, biomass of broadleaved weeds was not significantly different in two seedbeds (p=0.053). the false seedbed decreased grass and total weed biomass by 28 and 21%, respectively, as compared with conventional seedbed. imazethapyr application greatly affected grass and broadleaf weed growth and biomass production. the rate of 50 g a.i. ha-1of imazethapyr was as effective as the 100 g a.i.ha-1 rate to maintain consistent weed control in the false seedbed, while, the rate of 75 g a.i. ha-1 was required to maintain effective weed control in conventional seedbed. season-long weed competition resulted in 68 and 73% yield loss in common bean in the false and conventional seedbed, respectively. however, imazethapyr application decreased yield loss down to 4.7 and 2.9% in false and conventional seedbed, respectively. the study suggests that acceptable weed control in common bean of the weed species observed in the present study could be achieved using imazethapyr at the rate of 56 g a.i. ha-1 in combination with false seedbed, which can save the yield by 90%.