Rice to protect against cold wind

Cold dew is one of the main meteorological disasters in the growth period of southern late rice. Every autumn before and after the “cold dew” solar season, it is the critical period for the south China’s late rice to head and raise flowers. At this time, in case of low temperature hazards, it will cause empty shells and pods, which will lead to a reduction in yield, which is usually called “cold dew wind”. After the liberation, the double-season rice gradually expanded northwards to the middle and lower reaches of the Yangtze River. Late rice in these regions entered the heading and flowering stage in the middle and late September. It is also vulnerable to low temperature hazards. However, the term “cold dew wind” is still used in the middle of the Yangtze River. In some areas, it is called "society style" or "autumn wind", and the lower reaches of the Yangtze River is called "anchored" or "not countersunk". In the Yangtze River basin, there is "the autumn equinox does not come out and the cows are cut and fed". Although the time and the title are different, they are essentially the damage caused by the low temperature in the autumn to late flowering and grouting.

one. The danger of cold dew

The late rice growth stage is sensitive to low temperature for three periods: (1) young panicle differentiation (25-30 days before heading); (2) meiosis of pollen mother cells (10-15 days before heading); (3) Heading and flowering period. Among them, the risk of being exposed to cold dew wind during the heading and flowering period is relatively high, and the risk of cold damage during the meiosis period is relatively small, but the damage is heavier after encountering, and the young panicle differentiation period is basically not affected by low temperature damage.

The meiosis period is most sensitive to low temperatures, mainly stamen victimization, which results in the failure of normal maturation or poor maturity of the pollen, resulting in phenomena such as deformity and metamorphosis of empty grains or grains, resulting in reduced yields.

When the heading and flowering stage meets the low temperature, the pollen grains cannot be normally matured and fertilized normally, resulting in empty grains; at low temperature conditions, the heading speed is slowed, the heading period is prolonged, the spikelets cannot be normally opened, loose powder and fertilization, and the ovary is prolonged. Etc., resulting in infertility, so that significant increase in empty particles. In addition, in the early stage of filling, in the event of significant low temperature, it will delay or stop the grouting process. As a result, the vegetative physiology of pods and rice plants is also inhibited. In some cases, the phenomenon that the grains are not full and the seedlings have died before they appear.

In general, when the cold dew is severe, the late rice yield is significantly reduced. There are many factors that cause the harm of cold dew, but it is mainly low temperature. Generally during heading and flowering, the earlier the emergence of low temperature, the lower the temperature, and the longer the appearance of low temperature, the heavier the damage will be. If there is strong wind, rain, or too dry, it will increase its harm. For example, in the coastal area of ​​South China, when the cold air meets the typhoon, winds are relatively large, accompanied by heavy rain, heavy rain, or continuous rain. The shortage of sunshine affects not only late rice but also mechanical damage and greater damage.

two. Type of cold dew

The harm caused by cold dew wind to late rice can be roughly divided into two types of weather.

1) Wet-cooled type: The cold air from the north to the south meets the gradually weakening and retreating warm-humid airflow, which usually occurs at low temperature and rainy weather, characterized by low temperature, rainy weather, and low sunshine.

2) Dry-cooled type: strong cold air goes south, winds northerly, winds are 3-5, air is dry, the weather is clear, and there is obvious cooling. It is characterized by low temperature, dryness, strong wind, large temperature difference between day and night.

three. Low temperature hazard indicator

Low temperature is the main factor affecting the heading and flowering of late rice. Generally, temperature is used as an index to measure the degree of damage.

In the south, planting double-season rice has a large range, complicated terrain, and different varieties, and the temperature indicators used in different regions are also inconsistent. According to the "China's Agricultural Meteorological Information Survey" and "China's Main Meteorological Disaster Analysis" in the cold dew wind standards, focus on a wide range, and easy to apply, the average daily temperature as the main basis for the classification of whether the cold dew occurs, the specific indicators are as follows :

1. The average daily temperature of japonica rice is lower than 20°C for three consecutive days or more.

2. The daily average temperature of indica and hybrid rice is less than 22°C for three consecutive days or more.

Fourth, the cold wind defense

The cold dew wind is very harmful to the double-season rice and must take active defense measures:

1. Grasp the law of appearance of cold dews and the safe heading date of double-season rice (refer to the date when more than 80% of the dates of the double-season rice during heading and flowering will not be harmed by cold dew). That is, according to the emergence of cold dew wind sooner or later, select varieties, arrange a suitable sowing date, make it safe and ear, avoid the harm of cold dew wind;

2. Scientifically use cold wind forecast and rationally arrange production. The long-term prediction of cold dewness can provide reference for all levels of leaders and farmers' friends when arranging double-season rice production. For example, in the early years of cold dew, some early maturing varieties can be used, and the planting area of ​​the double-season late rice can be appropriately reduced. In later years, there can be more late-maturing varieties.

3. Breeding anti-low temperature and high product species;

4. Strengthen field management, rational fertilization, scientific water use, enhance root vigor and leaf assimilation ability, make plants grow robustly, and increase their resistance to low temperature;

5. Take appropriate agricultural measures to improve the microclimate of the farmland. For example, before the advent of cold air, water temperature adjustment measures are generally used to carry out night irrigation (drainage during the day) and irrigation of deep water or spray water in rivers with higher temperatures, so that the temperature between the plants is relatively high; Insulation agent, that is, the insulation agent sprayed on the leaf or drip into water to form a film, inhibit evaporation of water, reduce heat, so that the temperature does not decrease or cooling rate and other insulation measures to reduce the temperature hazards.

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