Can extended phenology in wheat cultivar mixtures mitigate post-anthesis water stress?

Abstract

Abstract Wheat cultivar mixtures have a well-explored potential for improving crop diversity, yield stability, and agronomic features. However, it is unclear whether heterogeneity of phenological traits in such mixtures may help to cope with increasing environmental stresses and uncertainties. To investigate the option of using wheat cultivar mixtures with different ripening patterns for mitigating the adverse effects of post-anthesis water stress, a two-year field experiment was conducted during 2014−15 and 2015−16 growing seasons at the research field of School of Agriculture, Shiraz University, Iran. The factorial experiment was a Randomized Complete Block Design with 3 replicates, in which 15 mixture treatments including monocultures and every 11 possible mixtures of four early- to middle-ripening wheat cultivars were grown under two normal and post-anthesis deficit-irrigation conditions. The results indicated that under the stressful conditions, heterogeneity in the ripening pattern of mixtures was diminished. Consequently, dissimilarities in grain yields as well as various agronomic characteristics of mixture treatments were also lessened. Although cultivar mixtures showed some casual beneficial effects, such advantages were not consistent across all conditions. Besides, cultivar mixtures could not mitigate the post-anthesis water stress significantly. However, only when the total averaged values of Susceptibility Index across the two seasons were assessed, a tendency for decreasing SI (up to 5.9 %) was observed in response to the extended phenology, which may suggest further studies for investigating the cultivar mixtures in long-term cropping systems. Despite the general expectation for beneficial ecological services from cultivar mixtures, in many cases there were disadvantageous blends, which led to a considerable reduction in grain yield and water productivity in single growing seasons. Therefore, it is suggested that unless the performance, and preferably the involved mechanisms of cultivar mixtures are fully understood, use of blends as an alternative for conventional high-input wheat cropping systems may lead to adverse results.