The obstacles caused by excessive soil moisture or ground waterlogging on the growth and development of rapeseed, called rapeseed staining, also called wet damage, are common meteorological disasters in rapeseed production. Especially in low-lying areas, the probability of waterlogging is extremely high.
In the rapeseed production areas in the middle and lower reaches of the Yangtze River, most of the foreheads are rice. Due to long-term flooding, the physical and chemical properties are poor, and the fertilization capacity is low, which is an important reason for the low yield of rice bran. Waterlogging occurs when there is a long-term rainy weather or low-lying terrain, poor drainage, excessive water in the field, or water accumulation. Under normal conditions, under the condition of soil water content of about 40%, rapeseed in the wintering, flooding, flowering and pod development stages have obvious waterlogging symptoms, including waterlogging during seedling stage and pod development. Most sensitive. The rapeseed suffered from waterlogging during the growth period, the leaf color became lighter, the yellow leaves appeared earlier and more, and the plant height, stem diameter, root thickness, root length, green leaf number, leaf area, dry weight, etc. were all reduced and effectively branched. The number, the number of pods per plant and the number of grains are reduced to different degrees, and finally the loss of production and other losses.
The key to controlling waterlogging is to reduce the groundwater level, reduce the soil moisture content, and increase the application of quick-acting fertilizer in the seedling stage to promote the robust growth of rapeseed, improve the resistance to stress, and prevent the occurrence of secondary diseases in time.
The varieties with strong moisture resistance were selected to have higher relative germination rate, higher relative seedling length, root length, seedling weight and vigor index, and higher resistance to waterlogging rapeseed resistant to hypoxia stress.
Reasonable land preparation and ditching farmland infrastructure construction to ensure ditch and canal irrigation. In the rice-oil two-cropping area, in order to ensure the normal sowing of rapeseed, for the poorly drained muddy field, the ditch can be drained around 7~10 days before the rice harvest; if the residual water is difficult to drain, the sorghum deep ditch cultivation method can be used, which is beneficial to Reduce the groundwater level and promote root development and yield. In areas with poor drainage, it is necessary to eliminate surface runoff and reduce the groundwater level. The method is to use other management measures to open the ditch before or before transplanting, and the width is about 150 cm. Generally, the permeability of the sandy soil is good, and the kneading surface can be appropriately relaxed; the water permeability of the sticky soil is poor, and the kneading surface can be narrower. In particularly low-lying and rainy areas, a narrow arched back can be used. The depth of the groove is preferably 26-33 cm in the sulcus, 33 cm in the sulcus, and 50 cm or more in the gully. For plots with high groundwater levels, the depth of the furrow should be greater than that of the tillage layer.
Drainage in the ditch and cultivating soil transplanting fields may cause waterlogging after continuous drainage in the rainy weather. It is necessary to carry out clearing and draining in time after the end of the rainy weather, so that the main ditch, the ditch, the ditch and the ditch are connected, the drainage is smooth, so that the rain can live in the field and reduce the humidity in the field. After the weather turns fine, it is necessary to carry out the cultivating loose soil in time, and increase the application of fire ash or decomposed compost and manure to increase the ground temperature, control weeds, improve soil ventilation and promote root development.
Replenishing quick-acting fertilizer damage will lead to the loss of soil nutrients, and the nutrient absorption capacity of roots will decrease. According to the growth of seedling stage, 4~6 kg of urea should be applied per acre to promote the growth before winter. On the basis of topdressing nitrogen fertilizer, it is necessary to apply appropriate amount of phosphorus and potassium fertilizer to increase plant resistance. Apply 3 to 4 kg of potassium chloride per mu or 0.2% potassium dihydrogen phosphate solution, 2% to 3%. 50 kg of aqueous calcium phosphate solution. In addition, after the bud, the application of boron fertilizer once, that is, using 50% of 0.1%~0.2% boron fertilizer solution for foliar spraying, to prevent "flowers and not real".
Preventing the lodging of rapeseed after the occurrence of waterlogging, the underground part of the development is traumatic. In the middle and late stages, it may be "top-heavy". Therefore, after spring, it should be surrounded by the roots of the leaf, the cultivating of the soil, the foundation of the soil, and the spring. For the long-term trend of the plot, it is necessary to spray the growth regulator once in the flood season, generally with 15% paclobutrazol wettable powder 50g and 50 kg evenly sprayed per acre to improve the plant type and enhance the lodging resistance.
Preventing secondary diseases in the field where waterlogging occurs, it is prone to downy mildew under low temperature and high humidity conditions, and is susceptible to sclerotinia and clubroot disease under high temperature and high humidity conditions. It is necessary to remove the yellow old diseased leaves at the bottom and reduce the pathogenic bacteria. Select 2-3 times of carbendazim or polysulfate, thiophanate-methyl, thiophanate, and mancozeb to prevent it. For the field where the cabbage caterpillar is harmful, it can be controlled by alternating spray of avermectin emulsifiable concentrate or lambda-cyhalothrin emulsifiable concentrate. For the field damaged by aphids, it can be controlled with a dimethoate emulsion, an imidacloprid wettable powder, an imidacloprid emulsifiable concentrate or the like.
(He Yongmei)
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