Pre-sowing and early growing-season rainfall are key drivers of wheat yield change in Australia

Abstract Since 1990, Australian wheat yields have shown modest annual increases, with substantial spatial variation across dryland cropping regions. Quantifying the contribution of climate change, especially rainfall-related factors, to these yield trends is critical for informing effective adaptation strategies. To better understand these trends, we integrated crop simulation modelling, statistical regression, climate scenario analysis, and 18 rainfall indices, based on evidence indicating their strong influence on Australian crop yields to investigate water-limited wheat yield trends and their drivers across the Australian wheatbelt over the past 34 years (1990–2023). This study provides the first integrated, continental-scale assessment of how changes in rainfall characteristics have shaped these trends, revealing that water-limited wheat yields have generally declined, with cumulative reductions ranging from 6.8% in the eastern wheatbelt to 44.2% in the western wheatbelt. Plant available water at sowing and early-season rainfall were identified as the primary climatic drivers, together accounting for 80.0% of yield variation and dominating in about 79.1% of grid cells across the wheatbelt. Over this period, declines in plant available water at sowing and early-season rainfall contributed to an estimated 20.4% cumulative reduction in water-limited yield across the Australian wheatbelt. These findings reveal the key rainfall factors driving changes in water-limited wheat yields, supporting both the development of targeted on-farm adaptation strategies, such as soil-water management and flexible sowing, and the formulation of drought-resilience policies to enhance Australian wheat production.