Growth habit, plant density and weed control on weed and root yield of sweet potato (Ipomoea batatas L.) Areka, Southern Ethiopia

Abstract

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.