Abstract:

With the change of global climate, extreme weather events such as drought and flood disasters occur frequently. These have a great impact on crop yields. As an important main grain producing area, the impact of drought and flood on the agricultural production of the three provinces in three northeast provinces of China cannot be ignored. Based on historic meteorological data such as daily precipitation, maximum temperature, minimum temperature, 2 m average wind speed, sunshine hours and relative humidity, etc., the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) during 1988－2017 in three northeast provinces of China were calculated with different time scales. Through comparing with characterization of drought and flood disasters in history, SPEI was chosen to judge drought and flood in the growth season of spring maize. With the purpose of evaluating the effects of drought and flood on spring maize yield, based on the distance correlation analysis method, the index of reasonable time scale and key month were selected to analyze the relationship between the index and the relative meteorological yield of spring maize. The relationship between water conditions at different growth stages and the yield was also analyzed. The results showed that: (1) both SPI and SPEI could represent the drought and flood conditions in three northeast provinces of China. Compared with SPI, SPEI had higher correlation with the drought and flood disaster rate, and SPEI was more advantageous in characterizing the drought and flood conditions in the study area; (2) relative meteorological yield was significantly correlated with drought disaster rate in all three provinces (P<0.01), and reached 0.05 significant level with flood disaster rate in Liaoning province, but not significant in Jilin and Heilongjiang province; (3) the distance correlation coefficient between SPEI₃-8 and relative meteorological in Liaoning province was the largest, and that between SPEI₆-8 and relative meteorological yield in Jilin and Heilongjiang province was the largest. SPEI and relative meteorological yield showed a downward parabolic trend. Overall, the impact of waterlogging on the yield in Liaoning was slightly less than that of drought, mild drought or moderate wet could lead to a decrease in yield. The impact of drought disaster in Jilin and Heilongjiang was much greater than that of flood, but severe humidity could lead to a decrease in yield. Compared with other provinces, the maize yield in Liaoning province fluctuated more sharply with the change of dry and wet; (4) in Liaoning province, maize may reach the highest yield when the jointing-heading period was close to severe wet, which was mainly affected by drought. In the late growing season, the impact of flood disasters was more severe than that of the early growing season, and both drought and flood disasters had effects on the yield. In Jilin province, the highest yield of spring maize was reached when SPEI was about 1.0 during the period of emergence-jointing and jointing-heading, and the effect of drought was more serious during the period heading-milking. The key growth periods in Heilongjiang province were mainly affected by drought, and the maximum yield was reached in the normal-wet years of emergence-jointing and jointing-heading stages, but medium-scale size or more severe floods still led to the decrease of maize yield. The high yield could be achieved in the slightly wet years in period of heading-milking stage, while the decrease could be caused by flood when it was severely wet. This research can provide a reference for estimating the impact of drought and flood disasters on spring maize and taking disaster prevention measures in three northeast provinces of China.

Key words: drought, flood, standardized precipitation evapotranspiration index, yield, spring maize, three northeast provinces of China