Intercropping potato with grain legumes for enhanced productivity and climate change adaptation in smallholder farms, Kenya

This study evaluated the effect of potato-grain legume intercropping systems on best land equivalent yield ratios, crop water productivity and net profits in field trials conducted in three agro-ecologies of Kenya: upper highland with seasonal rainfall of 592 mm and altitude of 2550 m, lower highland (505 mm, 1879 m) and lower midland (356 mm, 1522 m) in 2017 rainy seasons. Shangi and Unica the most common potato variety in Kenya, and a drought and heat tolerant variety, respectively, were grown alone and intercropped with the deep rooting legumes, Dolichos (Lablab purperous) and Lima bean (Phaseolus lunatus). Whereas the potato varieties had similar yields in the traditional highland growing zone, the heat and drought tolerant Unica performed significantly better in a typical semi-arid midland agro-ecology. Intercropping systems with lima bean and Unica potato variety increased crop water productivity by 38% compared to the pure Unica cropping system and maintained soil moisture content above 33% during flowering and tuberization stages at all sites. This resulted in significantly higher dry matter equivalent yields of 3.21 ± 0.12 ha-1 compared to pure stands (1.98 ± 0.21 ha-1) and when intercropped with Dolichos (1.11 ± 0.23 ha-1) in the low midland zone. This system (Unica + Lima bean) recorded the highest net profits of USD 3,324 ± 143 ha-1 across the three agro-ecologies. These results reveal a strong effect of Unica potato genotype and environment interaction, and show that intercropping a heat and drought tolerant potato variety with lima bean is an excellent option for improved resource use efficiency in non-mechanized smallholder farming systems. This strategy can diversify potato production to mid-elevation agro-food systems and mitigate events of climate change in traditional growing regions.