<p><strong>Background:</strong> In the wake of the changing climate, the current water crisis has increasing relevance for the human race, hence estimation is an integral part of planning, development and management of water resources of the country based on several meteorological parameters. <strong>Hypothesis. </strong>No significant changes in water requirements sweet potato crop for the next 20 years in Katumani, Kenya. <strong>Methodology:</strong> The study predicted the implications of climate change on crop water requirements for the short rain seasons between 1991-2016 (baseline climate) and future from 2020-2039 (climate change) in Katumani with the aid of the CROPWAT 8.0 model. Crop Water Requirements (CWR) were projected in two scenarios: i) Average rainfall and temperature of baseline period (1991-2016), ii) rainfall and temperature predicted in 2039 based on Relative Concentration Pathways (RCP); 8.5 and 2.6 scenarios, adopting the global circulation models (GCM) of IPSL-CM5A-MR and GFDL-CM3 for predicting monthly rainfall and temperature, respectively. To achieve effective water allocation and planning, data on sweet potato water requirements, irrigation withdrawals, soil types and climate conditions were gathered from the study area. <strong>Assumptions:</strong> The study assumed no change in the conditions relating to irrigation and crop production in the future. <strong>Results: </strong>Sweet potato water requirement in the baseline period were modelled at 579.9mm whereas predicted under RCP 2.6 and 8.5 to be 634.1 and 639.3mm, respectively. Averagely, a 16.7% decrease in effective rainfall may increase the overall sweet potato WR by 10.2%. This may be due to increased temperature and reduced rainfall. <strong>Implication: </strong>Short rain season is the most appropriate for production of rain fed crops in Katumani. <strong>Conclusion:</strong> This study is useful in explaining the adverse impacts of climate change mostly on sweet potato water needs in Katumani and in helping to plan and manage water resources for many other crops in arid regions.</p><p> </p><p><strong><br /></strong></p>

<p><strong>Background:</strong> Water is the most valuable resource in agriculture. Agricultural development in semi-arid eastern Kenya is essentially dependent on intermittent rainfall. An accurate estimate of sweet potato water usage and productivity is considered a significant feature of conservation agriculture under such climatic conditions. <strong>Methodology:</strong> The research was conducted for two seasons, from December 2018 to April 2019 and October 2019 to March 2020, with the aim of quantifying the water use efficiencies of two sweet potato varieties, Kabode and Bungoma. Assuming that there were no variations in water-use efficiency between the two varieties. The experiment was established as RCBD for the two seasons. Treatments comprised of sole sweet potato varieties of Kabode and Bungoma, together with their intercrops with common beans. <strong>Results:</strong> Seasonal effective rainfall values were 302 and 639.2 mm, whereas the mean saturation pressure deficit recorded was 2.5 and 2.4 Kpa for S (I) and S (II), respectively. This presented S(I) with 815.1 mm ET_crop demanding 622.1 mm irrigation water, whereas S(II) envisaged a 3.3% decrease in ET_crop values; 788 mm and requiring 427.6 mm of supplemental irrigation water to attain optimal sweet potato yields. Similarly, the test crops paraded WUE values of 39.8 and 30.0 kg ha^-1mm^-1and water productivity indices based on rain water were 1.11 and 0.95 kg m⁻³ for Kabode and Bungoma varieties, respectively. HI for S (I) were 40.8 and 35.4% whilst 54.2 and 46.8 % for Kabode and Bungoma varieties, respectively. <strong>Implications:</strong> WUE values of the sweet potato crop increased from warm-dry season S (I) to the warm-wet season S (II), as Kabode portrayed a higher adaptability. These results provide an acumen for decision making in the setting of climate change.<strong> Conclusions:</strong> Kabode variety differed significantly with Bungoma variety in their abilities to efficiently use water, thus portraying its adaptability in such a peculiar environment. The climatic environment: dew point temperatures and saturation pressure deficit had no significant impact on sweet potato water use efficiency.</p>

<p><strong>Background</strong>: Sweet potato producers in Kenya practice either sole cropping of or relay cropping and rarely do intercropping which aims at maximizing on time and space. <strong>Objective.</strong> To assess the relative performance of sweet potato under various cropping systems. <strong>Methodology:</strong> This study was conducted in Katumani, Kenya for two seasons; 2018/2019 and 2019/2020. The treatments comprised of sole cropping of Kabode, sole cropping of Bungoma, Kabode + common bean, Bungoma + common bean, and sole cropping of common beans (<em>Mwezi mbili</em>) were laid out in a randomized complete block design (RCBD) in 3 replications. Monocropped sweet potato and beans served as the control treatment. Weather data, leaf area, leaf area index, vine length, and percent canopy cover were collected throughout the cropping period. The data were analysed by a two-way ANOVA at 0.05% significance level followed by a Pearson’s correlation analysis on the extent to which length of vines, percent canopy cover, leaf area index, and weather parameters; ETo, aridity index, and rainfall influenced the attained tuber yields.<strong> Results:</strong> Intercropping significantly (p &lt; 0.05) reduced sweet potato yields of Kabode and Bungoma varieties by 19.3% and 44%, respectively. Monocropped Kabode yielded 31.4 t ha^-1, significantly (p&lt; 0.05) higher than monocropped Bungoma with 23.9 t ha^-1whereas their common bean intercrops yielded 26.2 t ha^-1and 18.1 t ha^-1,respectively.<strong> </strong>Correlation analysis showed that rainfall, ETo, LAI, vine length, and percent canopy cover negatively affected tuber yields. <strong>Implication:</strong> Land equivalent ratio revealed that intercropping sweet potato varieties with common beans was biologically efficient and that the percentage of the land saved averagely ranged from 8% to 33%. More studies should be conducted to determine the extent of sweet potato allelopathy on companion crops and nutrient use under intercropping systems. <strong>Conclusion:</strong> Yield stability analysis showed that orange-fleshed Kabode was the most stable variety across seasons to be grown in Katumani.</p>

<p><strong>Background:</strong> Soil hydraulic parameters in non-saturated conditions are crucial for explaining soil water dynamics in the field. It is therefore necessary to understand the link between soil water potential and hydraulic conductivity in the soil in order to estimate plant available water and hence simulate its movement within the soils. However, measurement of such hydraulic properties in the field and laboratory is somehow difficult, laborious and costly. <strong>Objective</strong>: To determine soil hydraulic properties of Ferro-chromic Luvisols in Katumani using the RETC code based on pedo-transfer functions; % sand, silt, clay and soil bulk density. <strong>Methodology:</strong> Undisturbed soil samples were collected from a profile pit at 0-15, 16-30, 31-45 and 46-60 cm depths using core rings for bulk densities and texture determination. Soil water retention curves and saturated hydraulic conductivities (Ksat) were estimated for all the samples using standard suction apparatus and the constant head method, respectively. The air entry suction (α) and pore size distribution (n) were generated using the RETC code. <strong>Results:</strong> The permanent wilting point and field capacity were at 0.081, 0.102, 0.107 and 0.121 and 0.188, 0.225, 0.241, 0.262 m³m^-3H₂O, whilst its soil water diffusivity ranged from a low of 6.39, 6.94, 9.03 to a high of 12.5 cm²min^-1 in the 0-15, 16-30, 31-45 and 46-60 cm depth, respectively. Ksat values from RETC code ranged from 29 - 48 cm day^-1, while the total and readily available water within the soil profile were 330.4 and 214.7 mm H₂O, respectively. <strong>Implication:</strong> The air entry value (α) and pore size distribution (n) implied an almost even distribution from the top and subsequent horizons. The soils ‘field capacity was achieved at pF 2.0 whilst PWP was arbitrary indicated at pF 4.2 reducing the time it takes to calculate irrigation cycles based on the amount of water available to the crops. <strong>Conclusion:</strong> The data indicates that pedo-transfer functions; especially high bulk densities negatively impact on soil hydraulics conductivity.</p>