Crop water requirement and temporal-spatial variation of drought and flood disaster during growth stages for maize in Northeast during past 50 years

It is essential to comprehensively analyze the rules of water demand and supply and the variation of drought-flood disaster of growth stages for maize in Northeast China over the recent 50 years to provide theoretical basis for strategies of preventing and reducing disasters. The multivariate data including daily meteorological data during 1961-2010, maize growing records over the past 20 years, and agriculture disaster data in the recent 10 years for 48 agro-meteorological observation stations across Northeast China were used. Based on these data, the water requirement of the four growth stages were calculated using crop coefficient method to reveal the temporal-spatial distribution of maize water supply and demand over Northeast China. The drought-flood distribution and evolvement of maize during different growth stages in Northeast of the recent 50 years were analyzed using the crop water surplus deficit index as the assessment index. Results showed that the water demand of maize during the four growth stages and the whole growing period didn’t have an appreciable change. There was a significant aridity tendency during milky ripening to maturation, while during the other three stages and the whole growth period there were no significant changes of drought or flood. Different spatial distribution patterns of water demand were found for the four growth stages, with a band distribution. From sowing to seven-leaf period, the frequency of middle drought or above and middle flood or above was lower, while during the followed three growth stages, the frequency was higher. Widespread and regional middle drought or above and middle flood or above of growth stages had obvious decadal changes. From 1980s, the number of widespread and regional middle drought or above and middle flood or above increased significantly.