Effect of water stress and planting system on growth, yield and quality of sweet potato

Sweet potato (Ipomoea batatas (L.) Lam) is an important crop due to its cultivation as staple food for millions of small farmers as well as for poor people in Latin America, Asia, Africa and in many other parts of the world. This tuberous crop is susceptible to drought stress especially during the period of crop establishment as well as vine development and tuber initiation. Yield of the crop vary widely among farmers due to improper planting systems. This current study was aimed to investigate the influence of various irrigation intervals and planting systems on vegetative growth, storage root yield and quality of sweet potato (Ipomoea batatas (L.) Lam) cv. ‘White star’ under field conditions. Three irrigation intervals (7, 14 and 21 days for summer crop, and 14, 28 and 42 days for winter crop) and two planting systems (bed planting and ridge planting) were adopted in this study. Vine length, number of branches and average leaf area significantly reduced as the irrigation interval was increased. Ridge planting produced longer vines with greater leaf area in winter crop as compared to bed planting. Yield parameters (storage root length, storage root diameter, number and fresh weight of marketable roots per plant) were directly linked with vegetative growth especially in summer crop. Under water stress conditions, as vegetative growth decreased storage root yield was also reduced. However, yield attributes were not affected by the planting systems. Vitamin C content decreased with water stress, whereas total soluble solids (TSS) and leaf proline content significantly increased with water stress in summer crop. Ridge planting also resulted in increased leaf proline content in summer crop. It is concluded that for attaining good vegetative growth and storage root yield, sweet potato should be irrigated at an interval of 7 days during summer and 14 days during winter crop and planted on ridges.