GROWTH AND YIELD OF SWEET POTATO (Ipomoea batatas L.) MONOCROPS VERSUS INTERCROPS IN THE SEMI-ARID KATUMANI, KENYA

Abstract

Background: 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. Objective. To assess the relative performance of sweet potato under various cropping systems. Methodology: 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 (Mwezi mbili) 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. Results: Intercropping significantly (p < 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< 0.05) higher than monocropped Bungoma with 23.9 t ha-1 whereas their common bean intercrops yielded 26.2 t ha-1 and 18.1 t ha-1,respectively. Correlation analysis showed that rainfall, ETo, LAI, vine length, and percent canopy cover negatively affected tuber yields. Implication: 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. Conclusion: Yield stability analysis showed that orange-fleshed Kabode was the most stable variety across seasons to be grown in Katumani.