Model outputs were compared with detailed field experiments from four rainfall zones, three soil types, and five wheat genotypes. The model was used to simulate above- and belowground growth, grain yield, water and N uptake, and soil water and soil N in wheat crops in Western Australia. The examples show that there will be threats and opportunities for agriculture with climate change, depending on the actual change and other systems parameter.APSIM-wheat is a crop system simulation model, consisting of modules that incorporate aspects of soil water, nitrogen (N), residues, and crop development. This study highlights that the impact of climate change is often not linearly related to yields and the complexity of the change, the rainfall distribution and the crop water use need to be considered for realistic climate change impact assessments. In Western Australia, despite the large decline in rainfall, simulated yields based on the actual weather data did not drop, because rainfall changes occurred mainly in June and July, a period when rainfall often exceeds crop demand and large amounts of water are usually lost by deep drainage. However, soil water storage capacity and managing the stored water over summer will be critical for the wheat crop to benefit from increased summer rainfall. Using the well tested simulation model APSIM-Wheat indicated that the large additional rainfall in the Pampas of Argentina increased some of the yield potential of wheat in the current cropped region and would allow the extension of profitable wheat cropping into currently non-cropped areas. Annual rainfall in the wheat-belt has declined by about 11% since the mid 1970’s. Also here wheat is grown in winter and again rain is the main factor limiting production. In contrast, the wheat-belt of Western Australia shows a distinct Mediterranean climate with most of the rainfall occurring in winter. Rainfall has increased by 100–200 mm/year over the last century in the Pampas, but mainly in summer. The main factor limiting wheat production, grown over winter, is rainfall. The Pampas of Argentina shows a distinct sub-tropical climate with most rainfall occurring in summer. Case studies from major agricultural regions in the world will be presented where a simulation model was used to explore the potential impact of recent and future climate change on wheat production and externalities. As an alternative, well-tested bio-physical simulation models can be used as a first approximation for such a study. To study the full impact of a changing climate on agriculture, extensive experimentation would be required. This has potentially a large impact on agriculture.
Our climate is changing and will continue to do so in the future.
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