Submitted to: International Journal of Climatology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/23/2012
Publication Date: 4/26/2013
Citation: Yu, Q., Li, L., Luo, Q., Eamus, D., Wang, E., Nielsen, D.C., Xu, S., Chen, C. 2013. Year patterns of climate impact on wheat yields. International Journal of Climatology. doi:10.1002/JOC.3704. Interpretive Summary: Winter wheat yields are highly variable due to year-to-year variation in rainfall, temperature, and solar radiation. This study used long-term yield data (1889-2004) from Queensland, Australia, to determine the importance of these weather variables during both vegetative and reproductive development on wheat yield. Rainfall during the vegetative growth stage was found to have the greatest influence on wheat yield and could be used to predict final crop yield in advance of harvest. This study also found that the APSIM cropping systems model was able to simulate wheat yields well when precipitation was moderate (400-500 mm), but over-predicted yield when precipitation was greater, and under-predicted yield when precipitation was less. The cropping systems model can be useful to determine the effects of climate change on future wheat yields.
Technical Abstract: Rainfall, temperature, and solar radiation are defining factors for crop production. Due to the close correlation among these factors, it is difficult to evaluate their individual impact on crop yield. We propose to identify year patterns of climate impact on yield on the basis of rain and non-rain weather. We also evaluate the performance of crop models in simulating interactive effects of rainfall, temperature, and solar radiation under specific patterns that differ in terms of the relative dominance of each climate variable. Historical wheat yield data in Queensland during 1889-2004 were used in this study. The influence of meteorological conditions on wheat yields was derived from statistical yield data which were detrended by nine-year-smoothing averages to remove the effects of technological improvements on wheat yields over time. We considered the effects of meteorological conditions at both vegetative and reproductive stages on yield. Five patterns were identified in the analyses. Precipitation during the vegetative stage was the dominant factor for wheat yields although both temperature and solar radiation had measurable influences. As the effect of rainfall on soil water is relatively long lasting, its beneficial effect in vegetative stage was higher than its effect on reproductive stage. The Agricultural Production Systems sIMulator (APSIM) was evaluated using long-term historical data to determine whether the model could reasonably simulate effects of climate factors for each year pattern. The model provided good estimates of wheat yield when conditions resulted in medium yield levels, however in extremely low or high yield years, corresponding to extremely low or high precipitation in the vegetative 42 stage, the model tended to underestimate or overestimate. When growing season precipitation was high, simulations responded more favorably to reproductive stage rainfall than measured yields. This work is valuable for crop model improvement and model assessment of climate impact.