Simulating maize responses to climate change using a set of agroclimatic indicators in a maize-producing region of Portugal

Maize is one of the most important irrigated cereals in Portugal. This study assesses the impact of climate change (CC) on gross irrigation requirements (GIR), grain yield (Ya), irrigation water productivity (WPirrig) and on a set of agroclimatic indicators. Crop modelling simulations are performed at the field scale, while results are aggregated and analysed at the regional scale to support interpretation at different decision-making contexts. The study employs an ensemble range approach using the most extreme condition (Cold&Humid vs Hot&Dry), considering two Representative Concentration Pathways (RCP4.5 and RCP8.5) for the baseline period (1971–2000), the medium-term future (2041–2070), and the long-term future (2071–2100). Results show that anticipating the sowing date would be an effective adaptation measure, as the general increase in temperature would help to avoid high temperatures during the flowering period, which can reduce yield. Another important finding is that, although seasonal precipitation is projected to decline, maize GIR are expected to decrease by 1–11%, with the latter value associated with anticipated sowing resulting from shorter crop cycles. Impacts on Ya range from a 14% reduction under the Hot&Dry conditions to a 6% increase under Cold&Humid conditions. Reductions of around 5% and increases of 2.5% are predicted for Hot&Dry and Cold&Humid conditions, respectively, when earlier sowing. WPirrig improves with earlier sowing, achieving the highest values across all scenarios. These results highlight the importance of early sowing as a possible adaptation strategy to enhance yield stability and WPirrig in the face of future climate conditions.