Cold dew refers to a period of low-temperature weather where the average daily temperature remains below 20°C for more than three consecutive days in September. This weather condition is considered severe, especially during the late growth stage of double-season late rice. Cold dew wind primarily affects the heading and flowering phases of the crop, often leading to issues such as poor pollen development, incomplete flower opening, and problems with pollination and fertilization. As a result, the rate of empty grains increases significantly, which can have a serious impact on overall yield.
To reduce the damage caused by cold dew, it's essential to implement various preventive measures. These include selecting cold-tolerant rice varieties, planning sowing dates appropriately, and cultivating strong seedlings. In addition, farmers must closely monitor weather conditions during the heading and flowering stages of the rice. Once cold dew wind is detected, immediate action should be taken to protect the crop through comprehensive strategies.
1. **Flood with deep water for insulation**: Before the arrival of cold dew wind, fill the fields with 7 to 10 cm of deep water to provide insulation. After the wind has passed, gradually drain the water.
2. **Apply grass ash**: Spread a certain amount of grass ash 1 to 2 days before the cold dew wind occurs. This helps improve soil fertility and provides some protection against the cold.
3. **Foliar fertilizer application**: Two days before the cold dew wind, spray a solution containing 200 grams of potassium dihydrogen phosphate or other foliar fertilizer per acre, mixed with 75 kg of water. This promotes healthy root, stem, and leaf growth, enhances plant vitality, and improves grain setting rate and 1000-grain weight.
4. **Spray "920" (Gibberellic Acid)**: Apply 1 to 2 grams of "920" per 50 kg of water to rice plants that are not heading properly before and after the cold dew period. This helps prevent the necking issue in hybrid rice and supports better flowering and grain development.
5. **Pest and disease control**: After the cold dew wind, some plants may suffer mechanical damage or even fall over, making them more susceptible to pests like rice planthoppers. Therefore, it's crucial to monitor the field regularly and take timely measures to control any potential pest or disease outbreaks.
By adopting these practices, farmers can effectively minimize the adverse effects of cold dew and ensure better yields from their late rice crops. Staying alert to weather changes and being proactive in crop management are key to successful rice cultivation in this critical growth phase.
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