Source: China Weather Network
Cold Dew wind is one of the meteorological disasters that befall rice in its late growing period. The Cold Dew is the key time for the heading stage of the southeast late rice. The low temperatures at this time will cause empty, shriveled grain, resulting in reduced production. The damage is called Cold Dew wind. Since the liberation of China, the double cropping rice has gradually expanded northward to the Yangtze River Delta. In these areas, the second rice enters the heading and flowering stage on the second and third ten-days in September, when it is also vulnerable to the cold damage. The name "Cold Dew Wind" has been followed in these areas. In the areas around the middle of the Yangtze River, it is referred to as “She wind” or the Autumn Equinox wind; in the lower reaches of the Yangtze River, it is addressed as “Qiaosui”, meaning “raising ear” or “raising head”. In the Yangtze River valley, there is a proverb that goes, “If the ear doesn’t come out in the Autumn Equinox, the rice has to be cut to feed the cow”. Though the time and address of the damage is different, the basic idea is referring to the damage made by the low temperatures on the late rice.
1. Damages of the Cold Dew wind
In the growth period of the second rice, there are three stages when it is sensitive to low temperatures: first, the initiation stage of the rice head (25-30 days before heading); second, the pollen mother cell meiosis stage (10-15 days before heading); and third, the flowering period. Among them, the rice suffers the damage of the Cold Dew wind in its flowering period with more chance, and seldom in the meiosis stage, but once it comes across the Cold Dew wind in the second stage, the damage is serious. Meanwhile, the initiation stage is essentially free from low temperature damage. In the Meiosis stage, the rice is very sensitive to low temperature. The mainly victims is stamens, leading to the pollen not mature or less. The empty grain or ear deformities, abnormal are following, and the production cuts. Generally, in the year when the damage of Cold Dew wind is severe, rice production is significantly reduced. There are many factors for the Cold Dew, but low temperature is the main one.
