Sweetpotato slip planting density and slip length optimization for mass production of quality planting material in smallholder farm settings.

Sweetpotato production in unimodal rainfall farming systems in sub-Saharan Africa is constrained by inadequate quality planting material. Technologies for efficient production of sweetpotato planting material are imperative to improve this sub-sector. Consequently, two separate field experiments, using five orange-fleshed sweetpotato varieties were conducted to determine the optimum slip spacing and slip length for optimal vine growth and vine-cutting production as planting material. Slip spacing levels were (15×15), (20×20), (25×25) and (30×30) cm. The slip length treatments were; 15, 20, 25 and 30 cm all planted at 20×20 cm spacing. The experimental sites were ARI Uyole, Mbeya in 2016 and 2017 and SUA, Morogoro only in 2017. Both experiments were set in split-split plots in randomized complete blocks with three replications. The vine growth rate (cm day) and vine-cutting yield m were significantly (P=0.05) higher at Morogoro than at Uyole. Cultivars; Kakamega and Ejumula, respectively had significantly (P=0.05) higher vine-cutting yield than Kiegea and Mataya while cultivar Kabode had intermediate yield. Vine-cutting yield was significantly (P=0.05) higher at (15×15) cm than at (30×30) and increased with repeated vine harvesting. The effect of slip length though significant (P=0.05) over varieties, years and locations was inconsistent except for fresh foliage yield (t ha).