Effect of Number of Nodes and Storage Duration of Vine Cuttings on Growth, Yield and Yield Components of Sweet Potato (Ipomoea batatas L.) at Jimma, Southwest Ethiopia

Abstract

Information regarding cutting characteristics for the establishment and successful sweet potato production in the study area is scarce. The optimum number of nodes used for planting material and the effect of storage duration of vine cuttings have not yet been established. The objective of the study was to identify  the optimum number of nodes and storage duration of vine cuttings that improve the yield and yield components of sweet potato in Jimma area. Sweet potato cultivar, Awassa-83 was used for the experiment. A 3×4 factorial treatment structure in a randomized complete block design (RCBD), with three replications was used. Effect of different node numbers (5-nodes, 7-nodes and 9-nodes) and storage duration of vine cuttings (immediate planting, planting after 2-days storage, planting after 4-days storage and planting after 6-days storage) on the growth and yield parameters was studied at Jimma University research site. The result revealed significant interaction in the number of main stems, aboveground biomass yields (q/h), number of marketable tubers per hill, number of unmarketable tubers per hill, marketable tuber yields (q/h), unmarketable tuber yields (q/h), total tuber yields (q/h) and the harvest index. Statistically both 2 and 4-days storage duration of vine cuttings gave significantly higher marketable tubers than immediate planting and 6-days storage duration of vine cuttings under shade. 9-node numbers per cutting gave significantly higher total tuber numbers than 5 and 7-node numbers.  The total tuber yield of sweet potato was highly significant and positively associated with marketable tuber numbers (r=0.65**), total number of tubers (r=0.50**) and marketable tuber yield (r=0.99**). This also showed that, total tuber yield favored by marketable tuber numbers, total number of tubers and marketable tuber yield. The presence of high marketable tuber number and yield contributes much to the total yield because of  increase in individual tuber size and weight.  The correlation of marketable tubers per hill was significantly and positively associated with number of main stems (r=0.39*) and above ground biomass yield (r= 0.47**). This shows that marketable tuber numbers favored by main stem numbers and above ground biomass yield. When stem number increases, the plant canopy and associated leaf area increases leading to more carbon assimilation to the optimum level. Based on the results farmers are advised to use 9-node numbers per cutting with planting of vine cuttings after 2 days of storage duration to maximize their marketable and total tuber yields. Hence, studies involving various sweet potato genotypes on multi-locations for a number of years would generate sufficient information that enables appropriate recommendations to be made.

Keywords: Sweet potato; Storage duration; Node number;  Internodes; Vine cutting; tuber yield