Evaluation of Chemical and Cultural Methods of Weed Management in Potato (Solanum tuberosum L.) in Gishe District,North Shewa, Ethiopia

A field experiment was conducted in Gishe District, North Shewa, using irrigation during February to June in 2013. The objectives were to identify the most effective method of weed management in potato production as well as to assess the effect of herbicides and their rates of application on weeds and the crop. The treatments consisted of sixteen weed control methods, viz. atrazine (1.0, 1.5 and 2.0 kg ha-1), pendimethalin (1.0, 1.5 and 2.0 kg ha-1), s-metolachlor (1.0, 1.5 and 2.0 kg ha-1), isoproturon (1.0, 1.5, 2.0 kg ha-1), one hand weeding and hoeing 20 days after crop emergence (dae), two hand weeding 20 and 40 days after crop emergence (dae), complete weed free and weedy check. The experiment was laid out in randomized complete block design with three replications. Herbicides were applied as preemergence. The weed community comprised of grass (45.5%) and broadleaved (54.5%) weeds. Weed density and dry weight were significantly reduced by weed management methods. Isoproturon and pendimethalin on grass and atrazine on broadleaved weeds were more effective. Pendimethalin gave good control of Snowdenia polystachya while atrazine failed to control Amaranthus hybridus and Chenopodium fasciculosum. Application of isoproturon and pendimethalin each at 2.0 kg/ha, and hand weedings at 20 and 40 dae resulted in more than 80% weed control efficiency over the weedy check. Isoproturon and pendimethalin had higher herbicide efficiency index than atrazine and s-metolachlor. Weed management practices did not significantly influence days to emergence, number of stems/hill, plant height, number of unmarketable tuber/hill and specific gravity of potato tubers. On the other hand isoproturon at 1.5 and 2.0 kg/ha and pendimethalin at 1.5 kg/ha gave number of marketable tubers/hill statistically at par with complete weed free check. Marketable tuber weight/hill was maximum in complete weed free plot and had significantly higher total tuber weight/hill than other treatments. There was no significant difference in marketable and total tuber yield between complete weed free and isoproturon at 2.0 kg/ha and the latter treatment was also statistically in parity with pendimethalin at 2.0 kg/ha and two hand weeding at 20 and 40 dae. Unchecked weed growth throughout the crop growth period resulted in 62.1% loss in tuber yield which was reduced to 6.8, 10.3 and 12.4% with the application of isoproturon at 2.0 kg/ha, pendimethalin at 2.0 kg/ha and two handweeding at 20 and 40 dae, respectively. The cost-benefit analysis indidated that preemergence application of isoproturon at 2 .0 kg/ha was the best proposition for acceptable weed management in the study area under irrigated conditions. Keywords: hand weeding, pre-emergence herbicides, Solanum tuberosum, tuber yield, weed density and dry weight