Abstract:

The purpose of the research is to provide a theoretical basis for monitoring, forecasting, early warning and preventing of cotton drought disasters. Based on the monthly temperature and precipitation data at eight meteorological stations in southern Hebei Province from 1962 to 2020, the standardized precipitation evapotranspiration index (SPEI), regression analysis and Mann-Kendall test were used to analyze the drought variation characteristics of cotton growing season (from April to October). The results showed that the drought frequency in the whole growth period of cotton was 25% in southern Hebei, and the frequency of above severe drought was 6.8%. The drought frequency of seeding stage, seedling stage, bud stage, flowering and boll-forming stage, and boll opening stage was 35.6%, 30.5%, 32.2%, 30.5% and 32.2%, respectively. The climate of seedling stage changed abruptly from dry to wet in 1976 and showed a clear trend of wetting after 1976. The climate of bud stage changed abruptly from dry to wet in 1968, and became moist after 1968. The climate of cotton flowering and boll-forming stage showed a drought trend after 1982, and the trend was more and more obvious. The climate of cotton boll opening stage showed a drought trend after 1989. The climate during the whole growth period of cotton showed a drought trend after 1982. Since the 1990s, the climate of cotton seedling stage and bud stage showed humidified trend, while the climate of cotton flowering and boll-forming stage showed arid trend. These trends should be highlighted in variety breeding and cultivation technique improvement.

Key words: cotton, Hebei Province, growing season, SPEI index, drought characteristics