Modeling Wheat and Maize Productivity as Affected by Climate Variation and Irrigation Supply in North China Plain

A modeling approach was used to analyze the response of crop productivity to irrigation in the North China Plain (NCP), where excessive use of water for irrigation has caused rapid decline in groundwater table. We calibrated and evaluated the farming systems model APSIM with data from three sites (Luancheng, Yucheng and Fengqiu). The calibrated model was applied to simulate the response of crop yield to climate variation and irrigation. The results show that the APSIM model was able to simulate growth and yield of wheat and maize in a double cropping system. Root mean squared error (RMSE) of yield and biomass simulations were 0.83 and 1.40 t ha(-1) for wheat, 1.07 and 1.70 t ha(-1) for maize, respectively. Soil water and ET were also reasonably predicted, with RMSE of 24.33 mm 1.49 mm d(-1), respectively. The simulated rainfed yield range was 0 similar to 6.1 t ha(-1) for wheat and 0-9.7 t ha(-1) for maize in the double cropping system. Each 60 mm additional irrigation increased crop yield by 1.2 t ha(-1) and 540 mm irrigation would be required to achieve the yield potential of 7.1 t ha(-1) for wheat and 8.3 t ha(-1) for maize. If >180 mm irrigation water was available, partition it to wheat and maize would lead to higher total yield than applying it only to wheat. Changing to a single crop system would lead to significantly lower annual total crop yield, although yield of the single crop could be increased due to increased stored soil moisture.