| dc.description.abstract | Sweet Potato (Ipomoea batatas [L.] has increasing potential as a food security crop in Kenya. However, its’ production is comparatively low compared to its potential production, which is attributed to drought conditions and low soil fertility conditions alongside the use of local landrace cultivars that are quite low-yielding. A study was conducted at Meru University of Science and Technology comprising two field experiments (NPK fertilizer levels) and (soil moisture regimes) to assess the performance of selected improved sweet potato lines under the varied conditions. Three sweet potato varieties were used: CIP 106988.1 (Naspot13) and CIP 112286.1(Margarette), and a farmer-preferred variety, Kemb-10. The varieties were subjected to three watering regimes: (i) Severe stress (SS), 30 days WAE (ii) Moderate Stress (MS), 60 days WAE, and (iii) (WW) well-watered to maturity; three NPK levels: 0, 120 and 240 Kg NPK ha-1. A randomized complete block design in a split-plot with 3 replicates was used: water treatment as the main plot and, varieties as a subplot for moisture experiment and varieties on the main plot, and NPK levels as the subplots for the fertilizer experiment. Data collected data was analyzed using SAS 2007, and means were separated using the least significance difference test (P≤0.05). There was no significant interaction between moisture treatments and NPK levels with varieties. Water treatments and NPK levels significantly affected vine length, number of leaves, and tuber yield. Plants under severe stress had significantly lower vine length, branches, and leaves. Under Moderate stress 60 days WAE, plants experienced a significant reduction in vine length, leaves, and branches compared to the well-watered. However, this reduction was less compared to severe stress. The reduced vine length and tuber yield are attributed to impaired photosynthesis, reduced cell division, elongation, and assimilate partitioning. Tuber numbers correlated with leaves (r = 0.63*, 0.74*), and vine length (r = 0.62*, 0.76*).This positive correlation implies that if drought significantly reduces the number of leaves and vine length, it reduces tuber yield, indicating the effect of drought on tuber yield can be estimated by measuring tuber length and number of leaves. Sweet potato growth parameters (vine length, number of branches, number of leaves) and tuber yields (tuber length, tuber circumference, number of tubers, and tuber fresh weight were significantly affected by the different NPK levels applied. Application at 240 Kg NPK ha-1 produced the highest vegetative growth and tuber yields. As the NPK rates were increased from 0 Kg NPK ha-1 through 120 Kg NPK ha-1 to 240 Kg NPK ha-1, the vegetative and tuber yields also increased. Based on findings, ensuring the crop obtains enough moisture during the first nine weeks after planting is recommendable. In contrast, NPK nutrient supply is fundamental to the growth and development of the crop. It is recommended that farmers incorporate inorganic fertilizers in sweet potato farming, rather than just organic manures, for enhanced production. | en_US |
