Spatiotemporal variations in summer maize droughts in the Huaibei Plain.

[Objective] Drought is a significant abiotic stress affecting agricultural production in many regions of China. This study investigates the spatiotemporal variations in drought during the growing seasons of summer maize in the Huaibei Plain. [Method] The analysis was based on the drought severity index (DSI) from 2010 to 2019 calculated using metrological data measured from weather stations across the region. We focused on the top 0-10 cm soil layer and the root zone from the soil surface to the depth of 50 cm. The M-K test and the Kriging spatial interpolation were used to analyze the spatiotemporal variation in droughts over the region at different time scales. [Result] ① Since 2016, the severity and frequency of droughts have both significantly increased in the areas of Dangshan, Mengcheng, and Qiaocheng, while decreased in the area of Fuyang. In Suzhou, droughts mainly occurred in 2010-2012 and 2019. Compared to seasonal scale, some drought events exhibited greater severity and higher frequency at the ten-day scale with unpredictable onset. ② The highest average annual drought index and frequency both occurred during the sowing-emergence stage, reaching moderate level or above, with the frequencies exceeding 40%. Severe droughts or worse at both timescales occurred in northern Dangshan and central Mengcheng and Suzhou. The frequency of the 0-10 cm soil-layer droughts was higher in the southwest, while the frequency of 0-50 cm soil-layer droughts was higher in the east and north than in other areas. ③ At the ten-day scale, the periods with the highest drought severity in each growing season mostly started in the early stage of sowing - emergence, emergence - jointing, and the mid-stage of jointing - tasseling. Severe droughts occurred primarily in August and September. [Conclusion] Since 2016, there has been a significant increase in drought severity and frequency for summer maize in the Huaibei Plain, particularly during the sowing seedling stage. Severe droughts were observed at uncertain ten-day scales, with increased drought frequency. [ABSTRACT FROM AUTHOR]