Effect of Vine Harvesting Frequency on Sweetpotato Root Yield Components and Gross Income in Southern Mozambique

Sweetpotato is widely produced by smallholder farmers in Mozambique with average yield of 7.3 t/ha. One of the challenges in sweetpotato production system is inadequate seed during the rainy season resulting in low productivity. The few sweetpotato seed multipliers (Decentralized vine multipliers (DVMs)) resort to several vine harvesting frequency to meet farmers seed requirements at the peak of demand. Repeated vine harvesting contributes to sweetpotato root yield reduction. The objective of the study was to evaluate the effect of vine harvesting frequency on sweetpotato yield components. Three experiments were set up in three farmers’ fields in Vilankulos district inhambane province in Southern Mozambique in the 2021/2022 and 2022/2023 cropping seasons with a sweetpotato variety Esther. The experiments were set up in randomized complete block design with three replications in each farmer’s field. The treatments were no vine harvesting (control), harvesting only once at 8 weeks after planting (WAP), harvesting twice at 8 and 12 WAP, and harvesting three times at 8, 12, and 16WAP. Total storage root yield, number of roots per plant, root diameter, and root length were measured in each treatment. Results show that storage root yield was significantly higher in control (22.1 t/ha) and harvesting once (17.8 t/ha) compared to harvesting twice (11.8 t/ha) and three times (9 t/ha) (P < 0.05). Additional harvesting from one to two resulted in 33.7% yield decline. Vine harvesting twice resulted in 46.6% storage root yield decline compared to the control treatment. The same observation was noted for the number of roots per plant, where five roots per plant were observed both in no harvesting and harvesting once treatments. A 40% decline in the number of roots per plant was observed when vine harvesting frequency was increased from one to two. No treatment effect was observed on the root diameter. Increasing vine harvesting frequency from one to two or one to three resulted in a 14.7% income loss from sales of both vines and roots. Vine multipliers are recommended to harvest vines for use as planting material only once if they want to benefit from the roots for consumption or commercialization.