Effect of planting depth and cutting orientation on growth and yield of sweet potato (Ipomoea Batatas L.(LAM) cultivars for small scale production in Verulam

Abstract
Sweet potato (Ipomoea batatas L. (Lam) is an important root crop for small scale farmers in the KwaZulu-Natal province of South Africa. However, low storage root yields in small scale farming are attributed to a number of factors including poor selection of cultivars and possibly unsuitable cultivation practices. Therefore, two experiments were conducted over two growth seasons (2014/2015 and 2015/2016) to test the effect of sweet potato cultivar, orientation of cuttings at planting and planting depth of cuttings in the Verulam area of northern KwaZulu-Natal province. Both experiments were conducted in the field under rain fed conditions and both were laid out in a randomized complete block design (RCBD) with four replications per treatment. Experiment 1 tested four cultivars (Monate, Ndou, 199062.1 and Blesbok) in either horizontal or vertical orientation of cuttings at planting. In Experiment 2, cuttings of one cultivar (Bophelo) were planted at 5 different depths (5 cm, 10 cm, 15 cm, 20 cm and 25 cm) either horizontally or vertically. Vine lengths were measured at 3, 6, 9 and 12 weeks after planting on five randomly selected plants per plot. Aboveground biomass (ABM) yield, marketable yield (MY), non-marketable yield (NMY), storage root yield according to four size classes, total storage root yield and harvest index (HI) were determined at harvesting. Of the four cultivars tested in Experiment 1, cultivar 199062.1 scored the highest values for most parameters measured in season I, including MY, extra-large tubers (451 – 1000 g) and total storage root yield (significant, p<0.05). Cultivar Ndou scored the lowest values for all yield-related parameters measured in season I, but had the longest (significant p<0.05, at 12 weeks after planting) vines in season II. In season II, most differences among cultivars were not significant. For both experiments, there was generally a trend for plants grown from horizontally orientated cuttings to show higher values for most parameters measured than for plants grown from vertically orientated cuttings with significant (p<0.05) differences for total storage root yield and HI in season I. Planting cuttings to different depths did not have significant effect on any of the parameters measured, except for vine length at 12 weeks after planting for season II, where cuttings planted to a depth of 25 cm produced significantly (p<0.05) longer vines compared with other planting depths. However, it was observed that planting cuttings to a depth of 10 cm had a tendency to result in higher values for most parameters measured and 20 cm the lowest. The data collected in this study was preliminary and the experiments will have to be repeated before recommendations can be made to farmers with regards to the best cultivar, cutting orientation at planting and planting depth to use by small scale farmers at Verulam.
Description
A dissertation submitted to the Faculty of Science and Agriculture in fulfilment of the requirements for the Degree of Master Of Science in Agriculture in the Department of Agriculture at the University of Zululand, 2018
Keywords
sweet potato --Ipomoea batatas L.( Lam) --small scale farming --South Africa
Citation
Collections