A comparison of different herbicides in bean (Phaseolus vulgaris L.) production under two tillage system
Two trials on bean (Pnaseolus vulgaris L.) production under minimum and conventional tillage systems were conducted during the short and long rain seasons oi 1984 and 1985 at the Faculty of Agriculture farm Kabete of the University of Nairobi Glyphosate was used to kill the existing vegetation in minimum tillage plots. Conventional tillage plots were prepared in the normal way by cultivating once and then harrowing to produce a clean seedbed. Alachlor, metolachlor and metribuzin were used as preemergence herbicides to control annual weeds. The effect of these treatments on weeds and the crop were evaluated on a split plot design replicated four times with tillage system alloted to main plots and herbicide treatments alloted to subplots. Results indicated that uniform bean germination was established in both tillage systems. The preemergence herbicides controlled weeds better in conventional tillage system than in minimum tillage system, however, more kerbicidal damage to beans was at the same time observed in conventional tillage system. ■ Alachlor and metolachlor caused. X temporary damage to beans while metribuzin caused complete kill of the bean plants. Even though injurious to beans, metribuzin effected a better weed control in both tillage systems during the initial and critical weed stages than alachlor and metolachlor. Alachlor had an edge over metolachlor in controlling the weeds. Hand weeding Cfarmer's practice) both in conventional and minimum tillage systems controlled the weeds better than all the preemergence herbicides used and resulted into the highest bean yield followed by alachlor and metolachlor at higher rates of application. Metribuzin at all the rates used reduced bean yield below the unweeded control mainly because of its damage on the bean plants. In general bean yield was lower in minimum tillage system, however, the profit margin between the two tillage systems was not significantly different.