Screenhouse-based shade-tolerance assessments of coffee and bean varieties, and cover crops, to optimize multi-strata intercropping in African smallholder systems
Year: 2026
Type: article
Abstract: Introduction Intercropping annuals with perennials such as banana, coffee and trees is widespread in East and Central Africa, where farms are typically small and fragmented. Within such multi-strata production systems, shade is a critical constraint affecting crop productivity. This study aimed to identify crop species and varieties tolerant to varying shade levels. Methods Twenty common bush and climbing bean ( Phaseolus vulgaris ) varieties each, eight Arabica coffee ( Coffea arabica ) varieties, and three cover crops (velvet bean ( Mucuna pruriens ), rattle pod ( Crotalaria grahamiana ), and elephant grass ( Pennisetum purpureum )) were screened under four screenhouses transmitting photosynthetically active radiation (PAR) levels of 70%, 50%, 35% and 10% compared to open field light levels. Results Eight bush and four climbing bean varieties maintained grain yields comparable to open-field conditions at low (70% light transmission) shade conditions. High tolerance persisted for many beans at 50% and 35% transmission, though only two bush beans (HM21-7, CODMLB 499) remained unaffected at the deepest shade (10% light transmission). Bush beans consistently elongated under shade, whereas climbing beans showed mixed height responses. Arabica coffee seedlings exhibited stable height and stem diameter across all shade levels, with only a few varieties showing modest reductions. Cover crops showed no shade tolerance, with > 84% above-ground biomass loss across all shade levels for elephant grass. Meanwhile velvet bean and rattle-pod suffered 48–58% biomass losses even at 70% light transmission, though velvet bean retained a high root mass until the deepest shade. Discussion These findings suggest a high diversity in shade tolerance within existing bean and coffee varieties. They demonstrate that selecting shade-tolerant bean cultivars and stable coffee varieties can substantially improve productivity in multi-strata systems, while many common cover crops are unsuitable beneath canopy shade. Rapid phenotypic screening could offer a low-cost strategy for optimizing crop mixtures and guiding breeding efforts toward greater shade resilience in smallholder multi-strata agro-ecosystems.
Source: Frontiers in Agronomy
Language: English
Subfield: Agronomy and Crop Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: gold
Estimated APC paid: $3,077
OpenAlex ID: W7154262782