| Based on phenological data of summer maize at from typical agro-meteorological experimental stations and parallel daily meteorological data from 48 meteorological stations in the North China Plain (NCP) from 1981 to 2009, we analyzed the variations of agro-climatic elements during summer maize growing season in recent 30 years by using the method of liner regression. The results showed that mean temperature, mean maximum temperature and mean minimum temperature during the period from emergence to jointing were increased by 0.42℃·10a-1, 0.36℃·10a-1 and 0.58℃·10a-1(P<0.05), respectively. There were more stations where mean minimal temperature became increased statistically significantly than those where mean maximum temperature was increased significantly. Mean daily temperature range became decreased by 0.22℃·10a-1(P<0.05) during the period from emergence to jointing. There was no significant changing trend in the temperature during the period from jointing to tasseling. However, mean daily temperature range was decreased by 0.22℃·10a-1(P<0.05) from jointing to tasseling. Mean temperature, mean maximum temperature and mean minimum temperature during the period from tasseling to maturity were decreased by 0.16℃·10a-1(P<0.05), 0.15℃·10a-1(P<0.05) and 0.06℃·10a-1, respectively. The stations where the temperature became decreased significantly in statistics were located in Shandong province. Also, precipitation was changed little during all the development stages of summer maize, except for the south area of Shandong and the middle regions of Henan where precipitation during the period from the emergence to jointing had been increased significantly. Additionally, mean daily radiation was decreased by 0.83 MJ·m-2·10a-1, 1.10 MJ·m-2·10a-1, 0.87 MJ·m-2·10a-1 and 0.89 MJ·m-2·10a-1(P<0.05), respectively, during the periods from emergence to jointing, from jointing to tasseling, from tasseling to maturity and from sowing to maturity. The results are helpful to refine the agricultural measures in summer maize production in NCP. |