Abstract: Based on the observational data collected from 124 meteorological stations in Northeast China from 1961 to 2008, water deficit indices were defined for maize in different growth stage, and then spatial and temporal distributional characteristics of drought were analyzed on the basis of inter annual variation features. The results indicated that the occurrences of drought showed distinct seasonal and regional features. In the view of growth stage, drought occurred with high frequency at the seedling stage and the frequency decreased evidently at afterwards growth stages. Slight drought happened in higher frequency than moderate and severe drought. The main cause of drought was the seasonal distribution characteristics of precipitation. In the view of spatial scale, the occurrence frequency of drought for different degrees reduced gradually from west to east. The most frequent areas of drought were northwestern of Liaoning province, western of Jilin province and southwest of Heilongjiang province, respectively. For interdecadal variation characteristics, drought frequency decreased from 1960s to 1980s, increased slightly in the early of 1990s and increased apparently after the middle of 1990s, especially increased dramatically from 2000 to 2004. In view of different growth stage in the years, the trend of drought frequency was seedling stage＞jointing booting stage＞ filling maturation stage＞tasseling flowering stage. The most frequent water stress was slight drought for seedling stage during 1960s and 1990s, slight drought stress occurred frequently at tasseling and flowering stage during 1990s. All kinds of drought happened frequently at kernel filling to mature stage from 2001-2008. Thus it can be seen that the occurrence frequency of drought has increased in this area over the past several decades, especially in the critical period of yield formation of maize, and has dramatically adverse effect on maize yield. The results show positive significance to better understand the causes and distribution characteristics of drought for different growth stages of maize in Northeast China and then it will be beneficial to take appropriate measures.

Key words: Maize, Water deficit index, Drought occurrence frequency, Distributional characteristics, Primary causes