Abstract

Tenaw Workayehu*, Waga Mazengia and Legesse Hidoto

Sweet potato is mostly left unweeded or weeded lately. Effect of variety, plant density and weeding frequency on weed and tuber yield was studied from 1992 to 1994. Three varieties (Tis 1499: erect and early; Tis 2498: long vine, spreading and early, and Koka 6 intermediate), two weeding frequencies (30 to 40 (W1) and 70 days after sprout (DAS) (W2), and four plant densities (5, 7, 10, and 12.5 plants m-2 ) were laid out in factorial arrangement in randomized complete block design with three replications. The major weed was broad leaf covering 95% of the total weeds, Capsella rubella, Guizotia scabra and Plantago lanceolata being the dominant weeds. In 1992 and 1993, mean weed density in Tis 2498 was 17 and 18% less compared with Tis 1499 and Koka 6, respectively. Weeds at higher plant densities were 11.8% less compared with the lowest density. All the cultivars produced more yield in 1994, but Tis 2498 and Koka 6 yielded 35.4 and 8.3% less than Tis 1499, respectively. Weeding twice in the first two years significantly increased the mean yield by 46.2%. Weeding of Tis 1499 and Koka 6 twice significantly increased the yield by 23.2% each but Tis 2498 did not respond to weeding. The cultivars Tis 1499 and Koka 6 yielded 22.7 and 18.8 t ha-1 , more at 7 and 10 plants m-2 , respectively, but Tis 2498 did not respond. Weeding once and twice within the range of 7 to 12.5 plants m-2 had no significant yield variation indicating weeding once would suffice at higher plant density. Varieties with high population having erect and intermediate growth habits can be weeded twice. Growth with spreading canopy structure and plant density could be used as means to reduce weed infestation. This will save farmers time and labor and thus, breeders should focus in developing cultivars with spreading canopy structure with high yield.