Millets and sorghum as promising alternatives to maize for enhancing climate change adaptation strategies in the Mediterranean Basin

CONTEXT: Climate change is increasingly requiring the adoption of both climate-resilient alternative crops and sustainable management practices. Millets and sorghum are increasingly recommended as alternatives to maize in addressing these issues, yet there are no studies comparing the environmental impacts of food-crop millets and sorghum with maize, under sustainable management in Mediterranean area. OBJECTIVE: The present study examined for the first time the environmental and economic impacts, as well as agronomic performances, of rainfed cultivated proso millet, sorghum and maize over a three-year period under challenging climatic conditions in Emilia-Romagna region, Italy. METHODS: Different kinds of trials were realized during three years of experimentation in one location in Ravenna province. The first trial aimed to compare proso millet, sorghum and maize agronomical performances and water use efficiency in a low-input system. The second trial aimed to compare soil fertility and biodiversity impacts of two different agronomical management systems (low-input and high input) for the summer crops previously described. Soil basic fertility parameters were monitored and ground dwelling arthropods were collected and analyzed using pitfall traps. The last trial of this study intended to evaluate the environmental and economic performances of the previous cereal crops cultivated in the low-input and high-input systems, applying the Life Cycle Assessment (LCA) and the Life Cycle Costing (LCC) methodologies. RESULTS: Both organic sorghum and millet showed high potential as viable summer-crop alternatives, not only to organic maize, based on yield, water use efficiency, disease tolerance and weed competition, but also to conventional maize, based on reduced environmental and economic impacts. Positive land impacts including improved beneficial arthropod abundances and preserved soil fertility were evident under organic management. In fact, the comparative LCA and LCC, carried out with primary data from conventionally cultivated maize and sorghum within central-north Italy and the organic experimental field under investigation, showed that the Global Warming and Eutrophication Potential, were comparable between the organically cultivated crops and significantly lower than conventional maize and sorghum. CONCLUSIONS: The results highlighted the potential of sorghum and millet cultivation as rainfed summer-crop alternative to maize in climate-change context, especially in low-input agronomical systems. In particular, under rainfed, organic management over three years, proso millet yielded consistently. IMPLICATIONS: Under the sustainable practices of the present study, proso millet outperformed maize for yield and WUE stability, as well as potential costs saved, related to the production amount per unit area and potential revenue.