Impacts and adaptation to climate change in Western Australian wheat cropping systems

The environment in which crops will be grown in the future will change. Temperatures and CO₂ concentrations [CO₂] will increase. Also a decline in winter rainfall of up to 30% in 2070 is predicted for south-west Australia. Effects of climate change on cropping systems were simulated with the Agricultural Production Systems Simulator (APSIM-Nwheat) using transformed historic weather data. Fifty years of yield were simulated for three soil types at different locations on a north - south transect within the wheatbelt of south-west Australia. Simulation results showed that there were complex interactions between different aspects of climate change on crop systems. Effects of higher temperatures, elevated [CO₂] and changed rainfall were in general not linear and differed significantly between soil types and location. Higher [CO₂] increased yield especially at drier sites while higher temperatures especially had a positive effect in the cooler and wetter southern part of the region. The main difference between soil types was that heavier clay soils were most vulnerable to reduced rainfall while sandy soils were more vulnerable to higher temperatures. We tested which changes in crop traits would be a good adaptation to climate change for wheat systems. Earlier flowering varieties can increase production at lower rainfall and ambient temperatures. At increased temperatures a later maturing variety will promote wheat production. On clay soils early vigor did not improve yields for historic and future climate scenarios. Also increased rooting depth did not positively affect yields on clay soils. So the options for adapting cropping systems to climate change on clay seem to be limited. This in combination with the results that yields on clay soils are reduced the most by climate change makes these soils very vulnerable to the impacts of a drying climate. On loamy sand soils however there are plenty of opportunities to adapt cropping systems to climate change. In addition to longer season varieties and early vigor also increased rooting depth can significantly increase yields under future climate change.