关键词: 气候变化, 华北平原, 夏玉米, 适宜播期, 高稳系数

Abstract: 【Objective】As the demand for food and fuel increase with growing population, society will be pressed to increase agricultural production, especially in China. Under the background of limited arable land resources, increasing yields and their stability on already cultivated lands is a high priority to food security. North China Plain is the main summer maize producing area in China. Therefore, knowledge of the suitable sowing date of summer maize in this region under climate change are quite important for stabilizing and improving the yield of summer maize and ensuring food security in China. 【Method】 In this paper, the study area was divided into eight climatic zones (CRs) according to the precipitation and accumulated temperature during summer maize growing season. In each climatic region, the APSIM-Maize model was validated based on climatological data from 1981 to 2015, agro-meteorological observations of summer maize and soil data. Then statistical indicators of the decision coefficients (R2), D-index, root mean square error (RMSE) and normalized root mean square error (NRMSE) were used to evaluate the model performance and accuracy. Using the validated models, the summer maize yields on the different sowing date were simulate in each climatic region. In the winter wheat-summer maize cropping system, we identified the suitable sowing date of summer maize under two scenarios: Potential (non-water limited) and rain-fed (no irrigation), by using the high stability coefficient (HSC) and considering the sowing date of winter wheat. And evaluated the yield changes of summer maize under appropriate sowing date were compared with the current actual sowing date. 【Result】 For model evaluation indicators, the R2 values were higher than 0.75, the D values were higher than 0.80, and NRMSE values were less than 7%, and those results indicated that the APSIM-Maize model provided good estimates of the growth period and yield of summer maize, and could be applied to simulate the growth period and yield of summer maize in North China Plain. Under full irrigation, the suitable sowing date of the CR1 was mainly in late June. For CR2 to CR7, the suitable sowing date were mainly in the middle and late June, and CR8 was mainly in the middle and early June. Under rain-fed conditions, the suitable sowing date of the CR1 was mainly in late June and early July. For CRs 2, 3A, 4, 5, 6, the suitable sowing date were mainly in late June. CRs 3B and 7 had a wide range for sowing in June, and CR8 were suit for mid-June. Under potential and rain-fed conditions, there were increases in yields due to the changes of sowing dates in each CR. Moreover, CRs 1 to 5 had the highest yield increases, with an average of 4% to 10%. For CRs 6 to 8, yield increases were ranging from 2% to 5%. CR8 had the lowest increases, with an average of less than 3%. 【Conclusion】 The suitable sowing date of summer maize in North China Plain advanced with the increase of latitude. On the conditions of potential or rain-fed, the suitable sowing date of summer maize delayed 3 days per decade from the 1980s to the 2000s. The suitable sowing dates in CRs 1 and 2 under rain-fed condition were later than that under potential conditions, while there were no significant differences in other CRs. Compared with the actual sowing date, the yield under the suitable sowing date was increased by 2% to 10% in each CR, but there were no significant differences between potential and rain-fed conditions. The magnitude of increase rate showed a decreasing trend from south to north. In the CRs 1 to 5, the yield increases were higher than other CRs.

Key words: climate change, North China Plain, summer maize, suitable sowing date, high stability coefficient