Physiological Responses and Productivity Assessment of Sorghum-Leguminous Association Cropping Systems in the Sudan-Sahelian Zone of Burkina Faso, West Africa

Optimizing farming systems is essential to boost productivity in Sudano-Sahelian zones, particularly in the face of challenges posed by climate change and soil degradation. This research explores the effects of sorghum-mungbean (Vigna radiata) and sorghum-voandzou (Vigna subterranea) intercropping on crop physiology and productivity in a farming context in Burkina Faso. The experiment was carried out at two sites, Yilou and Tansin, using a randomized block design with three treatments (sorghum monocrop, intercropping sorghum + leguminous, leguminous monocrop). The parameters such as leaf area index (LAI), stomatal conductance, leaf water potential, grain and biomass yield, and the Land Equivalent Ratio (LER) have been measured and calculated. The results show a variation in physiological and agronomic responses depending on the type of association and the site. In monoculture, sorghum shows a higher but not significantly (p = 0.206) leaf area index (LAI) of 1.41 compared to the associations, where it is 1.35 for sorghum-mungbean and 0.97 for sorghum-voandzou. In Yilou, the stomatal conductance of sorghum in association with voandzou was higher (340.9 ±50.885 mmol/m²/s) than in pure cultivation (264.7± 40.254 mmol/m²/s, p = 0.241), indicating better water uptake. In Tansin, on the other hand, sorghum in pure culture had a higher conductance (411.840± 95.625 mmol/m²/s) than when combined with mungbean (252± 45 mmol/m²/s, p = 0.122), suggesting greater water competition. In terms of productivity, overall, the sorghum-mungbean intercropping had an average LER (Land Equivalent Ratio) for grain production of 1.3, while it was 1.05 for the sorghum-voandzou system, but without any significant difference (p = 0.301), indicating respective gains of 30% and 5%. Furthermore, the average LER for biomass was 1.25 for the sorghum-mungbean system and 1.20 for the sorghum-voandzou system, but this difference was also not significant (p = 0.344). These results indicate that sorghum-leguminous associations improve resource use efficiency, although their performance depends on agro-ecological conditions. The sorghum-mungbean intercropping seems better suited to optimizing grain yield, while both systems could offer similar benefits in terms of forage production.