Effect of different soil texture on the final sweet potato tuber shape (Ipomoea batatas)
Abstract
There is increasing demand for sweet potato in the manufacturing and export sectors. These new markets for sweet potato are creating new challenges that need to be addressed. One of the key demands of the export and processing market is the requirement for standard uniform tuber shape, size and color. While color can be predetermined by variety. Shape and size of the tuber are determined by environmental conditions in which crop is grown. Regularly shaped sweet potatoes are preferred by the export market, because of their easy packing and processing. Unfortunately factors which influence the tuber shape are not well understood. Therefore the purpose of this study was to find out if soil texture has a major role in determining the final shape of a sweet potato tuber. Therefore the purpose of this experiment was to find out if texture has a key role in determining the final shape of a tuber. The experiment was arranged as follows: The textures created where formed by addition of proportions of 10% (T2), 30% (T3), 50% (T4) sand to loam soil and a control experiment of 0% (T1). The study was conducted at Makerere University Agricultural Research Institute Kabanyolo (MUARIK) and was laid out as a randomized complete block design (RCBD) with 4 replications, 4 treatments and 16 pots. Data was collected at different growth stages of the crop, right from the 1st day of planting the vines to harvesting the tubers .Data was collected every after two weeks. The data collected included the number of vine branches per sweet potato plant, number of leaves per sweet potato plant and number of vine branches per sweet potato plant. After harvesting of the tubers data were collected on weight of tubers, and shape regularity. Data collected was analyzed using GenStat statistical software package 14th edition. Analysis of variance (ANOVA) was performed to determine significant differences within the treatments at 5% (P ≤ 0.05). Significant differences (P < 0.05) were observed among different treatments over the exposure period. Results of the study showed a significant effect of the treatments (P<0.005) on plant height, number of leaves, vine branch number and yield data of weight of tuber and shape regularity. Pots that had added proportions of 50% (T4) sand to loam soil had the highest vegetative growth (longest plant height, highest number of leaves and vine branches) and yield (weight of the tubers) followed by that of 30% sand added to loam (T3) soil .while the pots with 0% sand added to loam (T1) soil had the least vegetative growth( leaf number, vine number and plant length) and lowest yields (weight of tubers) followed by 10% sand added to loam soil (T2). Although increasing the sand percentage in loam soil increased yields ,it reduced the shape regularity of the tubers i.e. the pots with 50% sand added to loam(T4) had more irregularly shaped tubers while pots with less or no sand added to loam soil had more regular tubers. This study therefore recommends growing tubers in a more sandy soil if the farmer is interested in yields, and maintaining a minimal sand percentage to balance high yields and shape regular.