关键词: 倒伏, 气象等级, 倒伏率, 夏玉米

Abstract: Strong wind and precipitation are the direct external conditions that induce maize lodging. In order to accurately define the lodging degree of summer maize under different wind and rain conditions, the data of maize regional variety tests in Hebi city from 2003 to 2019 was used. The wind speed (extreme max. or max.wind speed) and precipitation were extracted according to the recorded lodging time. The quantitative relationship between lodging percentage and meteorological conditions was analyzed, and the summer maize lodging meteorological grade index was constructed. The validations of the indices were conducted using agricultural meteorological observation data and lodging disaster data in the literatures. Firstly, according to the correlations between the lodging percentage and precipitation at different time scales, the “process rainfall” that had a significant impact on lodging was determined as the total amount of precipitation from 1 day before the occurrence of the lodging to 1 hour during the lodging process. R2 of the regression equation between the determined "process rainfall" and the lodging percentage was 0.924. According to the threshold of "process rainfall" of 15mm, the types of lodging disaster weather were classified into "strong wind type" and "wind and rain type". After classification, the fitness between wind speed and lodging percentage for two weather types was significantly improved. The regression equations between meteorological conditions and lodging percentage for two weather types were established. Then, the meteorological factors thresholds for three lodging grades (slight, moderate and severe) were determined responding to the lodging percentage standards 5%, 10%, and 20%, respectively. For the "strong wind type", the indices of light grade were the extreme maximum wind speed between 14m•s⁻¹ and 25m•s⁻¹or the maximum wind speed between 8m•s⁻¹ and 16m•s⁻¹. The indices of moderate grade were the extreme maximum wind speed higher than 25m•s⁻¹ or the maximum wind speed higher than 16m•s⁻¹. For the "wind and rain type", 15mm≤"process rainfall"＜40mm and the extreme maximum wind speed≥11m•s⁻¹ or the maximum wind speed≥5m•s⁻¹ was moderate grade；The indices of severe grade were the "process rainfall" higher than 40mm and extreme maximum wind speed higher than 15m•s⁻¹ or the maximum wind speed higher than 7m•s⁻¹. The validation results of the meteorological grade indices of maize lodging showed that 73% of the judged grades were consistent with the actual disaster grades, and 27% were different by one grade. The indices could provide a reference for meteorological early warning of lodging and guide agricultural production to prevent and reduce disasters.

Key words: Lodging, Meteorological grade, Lodging percentage, Summer maize