MORE CROP PER DROP: THE MAGIC OF SWEET POTATO (Ipomoea batatas L.)

Abstract

Background: 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. Methodology: 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. Results: 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 ETcrop demanding 622.1 mm irrigation water, whereas S(II) envisaged a 3.3% decrease in ETcrop 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-1 mm-1 and 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. Implications: 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. Conclusions: 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.