Evaluation of the Performance of Sweet Potato (Ipomoea batatas) Clones under Water Stress in the Coastal Lowlands of Kenya

The production of sweet potato (Ipomoea batatas (L.) Lam.) in coastal Kenya is diminishing due to unreliable rainfall, coupled with farmers’ use of unimproved sweet potato varieties that are not drought tolerant. A study was conducted at Pwani University from 2016 to 2017, to identify sweet potato clones with best performance under low water stress. Nine clones (6.1A, 4.10, 7.8, 15.10, 7.6AO, 10.10B, 4.2B, 7.6B and 4.2A) and a farmer-preferred variety “Rabai” were evaluated under the following four water stress levels: (i) Watering for the first two months after planting and stressing the plants for the next three months - S3, (ii) Watering for the first three months after planting and stressing the plants for the next two months - S2, (iii) Watering for the first four months after planting and stressing the plants for the next one month - S1, and (iv) Watering throughout the growing period and not stressing the plants at all - S0. A randomized complete block design was used, with factorial arrangement of treatments. Treatments were replicated three times. Tuber circumference was reduced by low water stress irrespective of the time it started, relative to the growing season. Water stress that was imposed early in the season, at three or two months after planting, reduced tuber yield by about 52 and 70%, respectively. Sweet potato clones C2 and C8 performed relatively well across seasons, irrespective of the water stress level. Farmers are likely to realize improved tuber yields by planting sweet potato early in the rainfall season to ensure adequate soil water during the first four months of crop growth. Sweet potato clones C2 and C8 are therefore recommended for multi-locational trials in coastal lowland Kenya, to ascertain their performance across agro-ecological zones.