What to Do When Rice Encounters Cold Dew Wind? Hazards and Preventive Measures

Cold Dew Wind refers to a disastrous weather phenomenon during the heading and flowering period of late rice in southern China, when the daily average temperature drops below 22°C for three consecutive days or two or more days, causing empty kernels and shriveled grains in late rice and leading to reduced yields. Because the temperature drop is generally accompanied by strong northerly winds, it is commonly known locally as Cold Dew Wind.

Hazards of Cold Dew Wind: When late rice encounters low temperatures during the heading and flowering period, pollen grains cannot mature and fertilize normally, resulting in empty kernels. Under low-temperature conditions, the heading speed slows down, the heading period is prolonged, spikelets cannot open, shed pollen or fertilize normally, and the extension of the ovary is impeded, thus causing sterility and a significant increase in empty kernels. In addition, if significantly low temperatures occur in the early grain-filling stage, the grain-filling process will also be delayed or stopped, resulting in shriveled grains. The plant nutritional physiology of rice is also inhibited, and in some cases the grains have not yet filled while the rice plants have already died prematurely.

Preventive Measures:

1. Reasonably match varieties. Based on the growth periods of early and late rice varieties, reasonably match varieties to ensure that late rice safely completes full heading before the arrival of Cold Dew Wind.

2. Select resistant varieties. There are great differences among varieties, so low-temperature-resistant high-yielding varieties should be selected.

3. Reasonable sowing dates, training strong seedlings, shallow transplanting and shallow irrigation, and scientific water and fertilizer management.

4. Regulate the microclimate to reduce damage: when a cold wave arrives, keep the water depth at 7-10CM at night, so that the daytime water temperature is 2-3°C higher than the soil temperature.

5. Spray ‘920’ and ‘Guli Bao’ etc. to speed up heading.