Abstract: 【Objective】The impacts of climate warming on growth process and yield of summer maize in recent 20 years in Huang-Huai-Hai Plain (HHH) of China, for the purpose of providing a theoretical basis for food security.【Method】Six provinces and regions (Hebei, Henan, Shandong, Anhui and Jiangsu provinces and Beijing-Tianjin region) in HHH Plain were selected as the area for conducting research. Making use of the meteorological observation data and the long-term observation data of summer maize in recent 20 years in HHH Plain, the relationships between climatic factors (temperature and precipitation) and growth process and historical production data during growing season were systematically studied by correlation and nonlinear multiple regression analysis and other statistical methods.【Result】In recent twenty years, an upward trend was found out in the temperature during the growth season of summer maize in Huang-Huai-Hai Plain. The precipitation in northern regions, Beijing-Tianjin region, Hebei and Shandong provinces, was reduced, while it was increased in Henan, Anhui and Jiangsu provinces. Compared to 1990s, the growth process of summer maize in HHH Plain was significantly changed since 2000. The whole growth stages were prolonged with vegetative period shortened by 2 and 1 d in Hebei and Shandong provinces, prolonged by 1 d in Henan province and reproductive stage prolonged by 4 and 2 d in Hebei and Shandong provinces, Henan province remained the same. Different correlations were found between each growth duration and temperature factors. Analysis of the relationship between two linear regression equations showed that the state-approved varieties had a same change in the growth period with the experiment station varieties. This indicated that varieties were one of the factors which affected the growth period of summer maize. By adopting linear partial regression test method the importance of varieties and climatic factors on summer maize growth period was analyzed and the results showed that the climatic factors were the main factors causing the changes of summer maize growth period. In addition to Jiangsu province, the summer maize yield in HHH plain is given priority to production. Nonlinear analysis showed that when the temperature rose, the summer maize yield in Hebei and Henan provinces rose. But the yield of maize in southeast provinces showed reduction in HHH Plain. Precipitation had a positive effect on the yield in the rarely rainy north region and a negative effect on the yield in the moist south region. Besides, when GDD10 rose, the yield in Hebei and Henan provinces increased, but the yield reduced in Shandong, Anhui and Jiangsu provinces. The whole HHH Plain yield reduced when GDD30 rose, obviously in Shandong province.【Conclusion】The above evidences indicate that summer maize production is affected by climate warming in HHH Plain. Summer maize is gradually adapting to climate warming. Varieties improvement and sowing date adjustment to adapt to climate warming can improve the yield of summer maize.

Key words: climate warming, summer maize, Huang-Huai-Hai Plain, varieties growth period, yield