Key Points for Rice Cultivation Management During Spring Cold Waves

I. Characteristics of Cold Wave Disasters

Due to the invasion of cold air, when the temperature drops sharply by more than 10°C within 24 hours, and the minimum temperature within that day is below 5°C, it is called a cold wave. In the middle and lower reaches of the Yangtze River, when strong cold air moves southward and causes the temperature to drop by more than 10°C within 48 hours, it is also called a cold wave. Cold waves generally occur in spring and autumn, with spring being the most common, and spring cold waves mostly occur from March to May. Cold waves mainly cause seed rot, seedling rot and dead seedlings during the rice seedling stage.

II. Rice Cultivation Management Measures

1. Determine a safe sowing period. Early rice in Hunan is generally sown from late March to early April, which is precisely the period when cold waves frequently occur. According to the temperature requirements for rice growth and development, early rice must be sown when the daily average temperature stably passes 12°C-14°C to be relatively safe. The safe sowing period for early rice in Hunan Province is from the Spring Equinox to Qingming (Tomb-Sweeping Day). During this time period, sow in stages and batches. The initial sowing period in southern Hunan can be slightly earlier than in western and northern Hunan, and plains can be slightly earlier than mountainous areas. During spring sowing, pay attention to listening to local weather forecasts, and master the technique of soaking seeds on the eve of a cold wave, germinating during the cold wave, and after the cold wave, seizing the "cold tail and warm head" to sow, striving for 3-5 days of sunny weather after sowing to promote root establishment and seedling emergence.

2. Select excellent varieties. Select varieties with high yield, strong cold resistance, suitable growth period, good grain quality and wide adaptability. At present, local early rice varieties (combinations) with relatively strong cold resistance: conventional rice includes Changzaoxian No. 10, 99-12, Chuangfeng No. 1, Xiangzu No. 1, 99 Zao 677, etc.; hybrid rice combinations include Zhuliangyou 819, Luliangyou 996, etc.

3. Reasonable cultivation models. ① Choose a suitable seedling-raising method. Our province mainly adopts 2 methods: film-mulched seedling raising and film-mulched soft-disk seedling raising, implementing seedling hardening, water management before the 4-leaf stage, and dry management after the 4-leaf stage, in order to cultivate strong seedlings. Some also adopt cold-resistant dryland seedling raising, whose sowing period can be about 7 days earlier than water-based seedling raising, will not suffer from seed rot or seedling rot, and emerges neatly. ② Reasonably choose the seedbed. Choose a plot that is sheltered from the wind and faces the sun, convenient for irrigation and drainage, and with fertile soil as the seedbed. This can not only meet the temperature, fertilizer and water needs required for seedling raising, but also allow the adoption of the dual measures of covering with film and irrigating water to protect seedlings when a strong cold wave comes. ③ Scientific management. During a cold wave, the seedbed should be tightly covered with plastic film to preserve heat and prevent freezing, and to prevent ventilation and air leakage. Where conditions permit, irrigate immediately to protect seedlings. After the cold wave, wait until the weather improves, then release water first, ventilate and harden the seedlings, and then remove the film. For seedlings whose leaves are green-wilted or yellow-wilted but whose roots and stems are not damaged: first, raise seedlings in shallow water, supplement water by irrigation or watering, keep the seedbed soil moist, and promote the seedlings to recover their vitality as soon as possible; second, fertilize to promote seedlings, using the method of going from light to concentrated and "eating small meals more often," topdressing 1000 kg of plant ash per hectare or spraying 750 kg of 0.2% potassium dihydrogen phosphate solution to promote seedling growth; third, prevent disease and protect seedlings. For seedlings affected by green wilt disease, spray the seedlings with a 1000-fold solution of 55% dexon to improve seedling quality; fourth, extend the time to strengthen seedlings.