Potential Global Change Impacts on Australia’s Wheat Cropping Systems

Wheat is the major crop in Australia in terms of both value and volume. National wheat production is currently about 24 million tones (Mt) from an area of 11.9 million hectares (Mha) with both production and area generally increasing over time (Figure 1). Yields are generally low (national average over the past decade of 1.75 t/ha) due to low rainfall, high vapor pressure deficit, and low physical and chemical soil fertility. High climate variability forces low input management to limit financial risk (Hammer et al., 1996). Irrigation can ameliorate this factor, but restricted volumes of irrigation water limit irrigated cropping. Consequently, regional yields are generally highly correlated with rainfall, although in high rainfall years yield reductions can occur due to waterlogging, lodging, and pest and disease problems (Stephens and Lyons, 1998a).