EFFECT OF PRE EMERGENCE HERBICIDES AND THEIR COMBINATIONS ON WEEDS INFESTATION, YIELD COMPONENTS AND YIELD OF COMMON BEAN (Phaseolus vulgaris L.) AT GURAFERDA AND MENITSHASHAWOREDA, SOUTH WEST ETHIOPIA

Weeds cause significant yield and quality loss in common bean. Thus, the experiment was conducted at Guraferda and Menit Shasha Woreda, Southern Ethiopia during 2019 main cropping season (July to October). The objectives were to determine the effect of pre emergence herbicides and their combinations on weeds infestation, yield component and yield of common bean, investigate the possibility of supplementing low dose of herbicides with hand weeding for effective weed control and to assess the economic feasibility of different weed management practices. The experiment comprised of 16 treatments: s-metholachlor at (1.0,1.5 and 2.0 kg ha-1); pendimethalin at (1.0,1.3,1.6 kg ha-1); s-metholachlor at 1.0kg ha-1+ pendimethalin1.0kg ha-1,s-metholachlor1.0 kg ha-1+ pendimethalin at 0.75 kg ha-1, s- metholachlor at 0.75 kg ha-1+ pendimethalin at 1.0 kg ha-1, s-metholachlor at 0.75kg ha-1+pendimethalin at 1.25 kg ha-1, s-metholachlor at 1.0kg ha-1+one hand weeding at 5WAE, pendimethalin at 1.0 kg ha-1 + one hand weeding at 5weeks after emergence (WAE), two hand weeding at 2 and 5WAE, one hand weeding at 3WAE, the weed free and weedy checks. At crop harvest, the integrated use of one hand weeding at 5WAE with s-metholachlor and pendimethalin both at 1.0kg ha-1and two hand weeding at 2and 5 WAE revealed lower weed dry biomass at both sites. The highest (3715.7kg ha-1and 3437.1kg ha-1) grain yield was obtained from the weed free at Guraferda and MenitShasha respectively. The maximum (79.48% and 67.64%) grain yield losseswere recorded from weedy check plots at MenitShasha and Guraferda respectively. The application of s-metholachlor at 1.0 kg ha-1 superimposed with one hand weeding at 5WAE had highest (Birr 27640.1 ha-1) net benefit.