Evaluation of multiple spring wheat cultivars in diverse intercropping systems

Re-diversifying agriculture through cereal-legume intercropping could provide higher productivity, but the cultivars and traits associated with agronomic performance of intercropping are currently unclear. Moreover, the impact of different cultivars on intercropping performance under diverse environmental and management conditions is largely unexplored. Therefore, we investigated various cultivar combinations of spring wheat (SW, Triticum aestivum L.) and faba bean (FB, Vicia faba L.) under diverse intercropping conditions, and evaluated their mixing abilities. We used variability in terms of plant height among cultivars and assessed the effects of height on total grain yield in the mixture. Twelve entries (ten cultivars and two cultivar mixtures) of SW and two cultivars of FB were sown as sole crops and all possible 1:1 species mixtures, with each of these treatments grown at two sowing densities and in three environments. Our results did not show any significant main effect of SW and FB cultivars on the total grain yield in the mixture. However, there were significant two-way interaction effects of SW cultivars with all the other factors (environment, FB cultivar, and sowing density) on the mixtures' grain yield advantage over sole crops. Spearman's rank correlation (ρ) among SW cultivars between SW yield in monoculture and total yield in mixture was variable, depending on the trial environment with ρ ranging from 0.42 (non-significant) to 0.90 (P < 0.001). In addition, a highly significant effect of environments and crop densities on the total grain yield in the mixture was observed. A significant but weak positive correlation of SW plant height with the total grain yield in the mixture was detected in one of the three environments. We conclude that selecting a site-specific partner combination of cereals and legumes with appropriate management practices is a key element to enhance functional complementarity and improve total productivity in intercropping, though the complexity of the interactions makes this a difficult task.