Rape seedlings need to prevent freezing
On January 20, a text message from the 159****1001 mobile phone: I was Zhang Guochao of Anhui Feidong. Our large area of ​​rapeseed has suffered freezing damage, and some canola even died of freezing. How can we reduce freezing damage and minimize the damage?
After a telephone interview, the large area of ​​rape leaves in the area is of different ages, the younger ones are in the period of 5-6 leaves, and the big ones are not convulsed. The leaves of frozen rapeseed are whitish, and some of the whole leaves or even all the leaves of the whole rape are white or dead. The rapeseed soil in these rapeseed fields is mainly heavy and the younger rapeseeds are the younger ones. The rapeseeds with relatively large field age are relatively free from freezing, and generally there is no phenomenon of whole plants dying. There is snowfall in the area recently, but the amount of snow is not great.
Rape is an overwintering crop and has strong cold resistance. Rapeseed planted in the Yangtze River valley is generally not frozen in winter. Under the severe frost conditions, the green leaves of rapeseed may be frozen. The main symptom is that the leaves in the morning leaves are hard and brittle, and the color is dark. The frozen parts are water-stained during freezing, and the severe frostbite is under strong light. Loss of water, dry white, often form a piece of white spots on the leaves, the entire white leaves of the severe dead. The rape that has been convulsed during the winter period has poor frost resistance, and the stolons are easily frozen to death. When the stolons are severely chilled and water-stained, it is best to remove the frosted stolons when the sunny temperatures are high. Otherwise, some enzymes released from the frozen cells will further damage the lower healthy tissues and increase the number of plants. The damage is not conducive to plant recovery.
Dry freeze will cause fatal damage to the rape. After the rape leaves are frozen, the amount of water loss in the leaves increases. If the soil is moist at this time, the root system can absorb more water to meet the water demand of the plants; if the soil is dry, or the soil moisture is frozen (when the temperature is too low, Rapeseed roots are weak in vigor and cannot absorb water. Roots cannot absorb enough water. Physiological water shortages can occur in plants and can cause water loss and death. In the overwintering stage, rapeseed with large leafage has well-developed root system and can absorb water in deep soil and is not prone to dry and frozen seedlings. In wintering period, oilseed rape with smaller leafage has shallow root distribution and can not absorb water in deep soil. Dry dead seedling phenomenon.
If the rapeseed is frozen, if the seedlings are large, even if the rapeseed leaves are severely chilled, the whole plant is unlikely to be frozen to death. It can recover quickly afterwards and generally does not require special measures to remedy the problem. The heavily frozen land can be used for snowfall in the near future. After the snow is wet, some fertilizer is applied to promote recovery. The fertilizer is applied according to the type and quantity of the previous fertilization. The field with adequate fertilization in the previous period may not be supplemented with fertilizer; the field with insufficient fertilization in the early stage may be supplemented with urea or NPK compound fertilizer according to the situation. In the field of small seedlings and soil drought, recent snowfall can alleviate the damage caused by dry ice to a certain extent. The amount of snow is not large, and dry and frozen fields may still occur in the later period. Watering should be carried out at higher temperatures after the thawing of the rape leaves. Watering the leaves of rape when it is frozen in the morning will aggravate frostbite. The heavier fields of rapeseed, combined with watering and other operations, use some humate-like foliar fertilizers and potassium dihydrogen phosphate, which is conducive to the recovery of rapeseed.
In addition, when the temperature is low and the soil in the tillage layer is frozen for a long time, rape leaves can thaw under strong sunlight before and after noon, and the humidity of the field soil is large in time, and the rape roots mainly distributed in the frozen layer of soil are also The phenomenon of dry frozen seedlings occurs because the root system cannot absorb enough water. In order to avoid this kind of harm, for the rapeseed with small leafage or thin growth and shallow root distribution, the roots should be planted, roots covered with organic fertilizer, covered with straw and other measures to protect the seedlings from overwintering.
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