Early prevention of freezing injury of rapeseed

Rapeseed is vulnerable to freezing injury at low temperature, especially the rape with good autumn hair is more vulnerable to low temperature freezing injury because of its green and tender leaves. According to the investigation, the degree of freezing is closely related to the strength of rape seedlings, topography, soil moisture and transplanting quality. Early anti-freezing is the key to obtain high yield of rape.

? Enhance the ability to resist cold

Taking different measures for different seedlings to ensure strong rape seedlings overwintering is the fundamental measure to defend against low temperature. In the process of overwintering, rape leaves are most likely to die from freezing, resulting in a decrease in the number of branches after the year, which directly affects the yield. Therefore, we must do everything possible to root and grow leaves before the end of the year. For the prosperous seedlings before winter, during the stage from Lesser Snow to the Winter Solstice, the soil depth is about 10 cm between rape rows, cut off part of the branch roots, reduce its nitrogen absorption capacity, and promote the accumulation of sugar and other organic compounds in rape plants to improve cold resistance. Pay close attention to the rape ploughing soil in order to thicken the root soil layer, which plays a certain role in preventing the cold wind from attacking and improving the ability of heat absorption, heat preservation and cold resistance, especially after the tall seedlings cultivate the soil, the shortening of the rhizome is beneficial to the heat preservation. When entering the cold winter season, especially before the attack of low temperature, the application of available nitrogen fertilizer should be controlled to control the growth of rape nutrient area and make the wax layer of rape leaves accumulate, which is beneficial to cold resistance.

Early and heavy application of wax fertilizer

Increasing the amount of phosphorus and potassium fertilizer in wax fertilizer can increase the thickness of leaf wax layer, and it is best to apply wax fertilizer before the cold wave comes. In the early stage of overwintering, the application of organic fertilizer such as pig and cow manure or soil fertilizer can increase the soil temperature by 2-3 ℃, and it can also play the effect of Lashi spring. Generally, it is appropriate to apply 1000-1500 kg pig and cow manure or 2000-2500 kg soil fertilizer per mu. Potassium can increase the concentration of cell fluid and enhance the cold resistance of cells, generally applying 5-8 kg potassium chloride and 10-15 kg calcium superphosphate per mu. Plant ash is rich in potassium and has strong thermal insulation. when the weather suddenly gets cold and other measures are too late to implement, we can spread a layer of plant ash on rape leaves and fields, which can not only protect leaves, but also increase soil heat absorption and soil temperature.

? Timely foliar spraying

Spraying phosphate fertilizer on rape leaves can significantly increase the thickness of waxy layer on the leaf surface and has a significant effect on cold resistance. Generally, the leaves that turn purple due to low temperature can be transformed into normal green after spraying phosphate fertilizer for 5 days, and can endure low temperature attack of minus 5 ℃. The specific method is to use 2 kg of calcium superphosphate or 0.5 kg of ternary compound fertilizer per mu, filter out the fertilizer residue after soaking in 30-40 kg water for a week, spray it on the leaf, and spray it again every 7 days, the key object of spraying is the rape field where the nitrogen fertilizer is overweight and green. For the thinner rapeseed, 0.1-0.2 kg urea can be added to the phosphate fertilizer solution to promote the growth of rape leaves, so as to improve the ability of leaves to produce waxy layer and enhance cold resistance.