Most of our province will enter the heading and flowering stage in mid-July after mid-July. During this period, rice will be sensitive to changes in temperature. If it meets the north with strong cold air southwards, it will enter Yunnan and meet the southwest warm and humid air stream. There will be a wide range of cool and rainy weather. As the saying goes, “The Valley is afraid of the autumn rain, people are afraid of the old to poor; the autumn north wind will not be full of grain,†the sudden drop in temperature will seriously affect the rice heading and flowering, corn flowering and pollination, thus affecting the seed setting rate, resulting in reduced production.
Low temperature during the drawing period: If the average daily temperature in the heading and flowering period of rice is lower than the critical indicator temperature for 3 consecutive days or more, it is the low temperature during the rice raising period, which is commonly called “low temperature in Augustâ€. If it appears, “low temperature in Augustâ€, sudden drop in temperature will inhibit or delay the flowering of rice, extend the flowering period, reduce the flowering rate, and even cause the spikelets to fail to open normally. The empty shell rate doubles; if the filling period is affected by low temperature, It will reduce the speed of grain filling, leading to a decrease in the growth rate of grain weight and a decrease in grain weight.
Low-temperature critical indicators: The critical temperature indicators of low-temperature rice during the pumping season in different regions of Yunnan vary according to the area and altitude. The distributions are: Zhaotong (17°C), Lijiang (14.8°C), Zhanyi (17.2°C). ), Dali (16.8°C), Baoshan (18.5°C), Kunming (17.2°C), Yuxi (18.5°C), Chuxiong (17.8°C), Mengzi (20.1°C), Wenshan (20.2°C).
Cold damage analysis over the years: By analyzing the data of the daily average temperature over August in more than 30 years in our province, it was concluded that the areas most affected by the low temperatures in August were the northeastern Yunnan and the eastern Yunnan, followed by the northwestern Yunnan and Langzhong, and the second was the western Yunnan. ; Most of Minnan has no effect. Historically, there have been 1965, 1966, 1971, 1972, 1974, 1977, 1983, 1988, and 2002 years of low temperature in August. These years, due to the low temperature and cold damage in August due to the heading and flowering stage of rice, all of the rice yields in different parts of the province were reduced.
The temperature distribution in most of the rice fields in our province has been normal to slightly higher this year. According to the statistics, from May to early July, the average temperature of the province was 21.5°C, which was 0.32°C higher than the same period of the previous calendar year. 85% of the stations were high in the province and the others were low. The anomalies of the ten-day average temperature were: 1.05°C, 0.14°C, 0.2°C, -0.02°C, 1.01°C, 0.24°C, -0.36°C.
Production measures: In order to ensure a bumper crop yield in the spring of this year, we still need to prepare for the defense against low temperature damage in the later period. We must not ignore the precautions against cold damage due to the high temperatures in the early days and we must be prepared for it. It is recommended that the following measures be taken in various places
1. Adopt “day-row night irrigation†to adjust temperature with water, improve the microclimate in the field, prevent low temperatures, and reduce the harm of cold damage. Change the water frequently on a cloudy day to regulate the temperature of the paddy field and supplement the oxygen in the water. At the beginning of earing, shallow water was poured.
2. In case of cold injury, various chemical agents and fertilizers can be sprayed, such as: "920", boric acid, naphthaleneacetic acid, kinetin, 2.4-D, urea, calcium superphosphate and potassium chloride, etc. Control effect. In the booting and filling stages of rice, spraying 902 rice cold-resisting agents had the best effect.
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