Simulating resilience of rainfed wheat-based cropping systems of Iran under future climate change

Recognizing the climate change (CC) can have vast impacts on agricultural production has generated a desire to create resilience into cropping systems. Crop management is the most important strategy to improve crop yield and resilience under CC. This study investigated the adaptation (changing planting date and crop rotation) effects on rainfed wheat yield in Iran. A fallow-wheat rotation was simulated by the DSSAT model under the Representative Concentration Pathway (RCP)-4.5 and RCP-8.5 emission scenarios, for four time periods (1994-2018, 2032s (2020-2044), 2057s (2045-2069), and 2082s (2070-2094)) and an ensemble of five GCM models within the latest model based CMIP 5 for 16 representative sites within agro-climatic zones of the country. Results revealed that the magnitude and direction of CC impact and adaptation response varied spatially even within the agro-climatic zones. Under future CC, due to higher temperature and lower precipitation, wheat yield are projected to decrease depending on emission scenarios in all sites except Qorveh, Aligudarz, and Saqez. In general, greater rainfed wheat yield reduction is highly possible during the late twenty-first century and wheat yield will be more affected by CC under RCP-8.5. In the highlands of northwest Iran, rotation carryover effects and chickpea- and annual medic-wheat rotations can modulate the rainfed wheat yield response to CC, in 2032s and 2057s periods, with greater effects from annual medic. In lowland areas, replacing fallow with crop legumes was not sufficient to avoid wheat yield losses. When planting dates were adapted, wheat yield improved across a large number of locations under all wheat-based crop rotations. In general, crop rotation can be considered as an essential component of risk reduction strategies for CC adaptation and yield resilience especially in areas where crop rotations better represent predominant cropping systems.