Climate change effects on the suitability of an agricultural area to maize cultivation: A new Hybrid Land Evaluation System for maize

Climate change will cause significant effects on the suitability of an agricultural area to specific crop cultivation for food and feed, mostly due to the changes in water distribution and availability that will be limiting factors in most of Mediterranean regions to the cultivation of some species, included cereals. Different approaches are used to examine the potential impact of climate change on crop yields able to evaluate the land suitability: (i) process-based crop simulation models, (ii) simple empirical approach, (iii) expert-based approaches, (iv) crop-specific evaluation approach, (v) Land suitability evaluation and (vi) statistical model approaches. But all approaches can show limitations in a widespread application and a best approach, universally recognized, doesn't exist. It is clear that the study of climate change impacts on land crop suitability must be oriented to consider the characteristics of environment and climate but also to the crop intraspecific variability (hybrids or cultivars) to the adaptation. In this sense, a Land Evaluation Hybrid System (LEHS) was proposed to evaluate the effects of climate change on land suitability for maize cultivation on an irrigated district of Southern Italy (Destra Sele, 20,000 ha), based on three hierarchical steps: (1) Evaluation of thermal conditions for maize; (2) Environmental evaluation for maize cultivation: Land suitability for maize (LE)(qualitative approach); (3) Evaluation of soil ability for maize crop adaptation to water availability (through SWAP agro-hydrological model), considering the reference and future climate information, water scarcity for irrigation and crop intraspecific responses in terms of adaptability (quantitate evaluation). The advantage of methodology applied is its hybrid approach which integrates: (i) the effects of single climatic variables on crop adaptation (e.g. temperature), (ii) the dynamic treatment of these ones on the soil-plant and atmosphere system by means of a physically based simulation model (iii) the evaluation of single Soil Typological Unit (STU) crop suitability considering a range of responses in terms of adaptability of a range of maize hybrids at different levels of water availability (iv) the use of classic LE that allows to consider some land characteristics that could be not necessarily characterized through the simulation modeling and generally not included in the studies of climate change impacts on crop adaptation (e.g. flooding risk). To reach this purpose : oTwo climate scenarios were studied: "past" (1961-1990) and "future" (2021-2050), the last generated through statistical downscaling procedures from general circulation models (AOGCMs) othe yield response functions to water availability of 11 maize hybrids (Zea mays L., belonging to four FAO hybrid classes) were determined from experimental data and scientific literature, identifying the hybrids' specific hydrologic requirements. othe agro-hydrological model SWAP (soil-water-plant and atmosphere) was used to determine the soil water regime (under different irrigation strategies: optimal irrigation, and deficit irrigation to simulate the water scarcity) and the hydrological indicator at landscape scale (25 STUs) in both climate periods. othe specific crop hydrological requirements and the hydrologic indicators obtained from SWAP were compared and the crop adaptability in each soil of study area in both climate periods determined. othe results of three steps of LEHS were compared, and the land suitability for maize to climate change realized The main results of LEHS approach have shown that in the study area: othe evolution of thermal conditions during maize growing season have not affected crop adaptability; othe main physical and chemical constraints of the study area were: pH, soil organic carbon content and flooding hazard (step 2, Standard Land suitability for maize, qualitative approach). ofrom the quantitative approach (step 3, simulation of soil water regimes with SWAP model), only four hybrids of maize could be considered suitable for cultivation (NS640, Manuel, PP700 and Kaystar 890) if a reduction in water supply was accounted for; othe quantitative and qualitative approaches showed the same weight as limiting factor in the final LEHS classification (30% ) with an agreement in the 40% of cases.