Rapeseed deficiency and its remedial measures

Rape needs to absorb a variety of nutrient elements in the process of growth and development. once a certain element is deficient, it will show corresponding symptoms of element deficiency through the external morphology of the plant. in production, it is often used as a basis for diagnosing element deficiency and taking remedial measures.

Nitrogen deficiency is the most important element for the growth and development of rapeseed. When nitrogen deficiency, the plant growth is thin, the leaves are few and small, yellowish green to yellow, some edges of the lower leaves of the stem are red, and gradually expand to the leaf veins; the number of effective branches and pods are greatly reduced, the 1000-grain weight is also reduced, and the yield is significantly reduced. Remedial measures: nitrogen deficiency at seedling stage, ditching with 15-25 kg ammonium bicarbonate per mu, or water application with 750-1000 kg human feces; late nitrogen deficiency, foliar spraying with 1%-2% urea solution.

Rapeseed with phosphorus deficiency is a phosphorus-loving crop, and its phosphorus requirement is more than double that of cereal crops. Under the condition of phosphorus deficiency, the plant was short, the growth was slow, the leaf emergence was delayed, the leaf area was small, the leaf color was dark green, lack of luster, purplish red spots or patches appeared at the edge, the veins on the petiole and the back of the leaf turned purplish red, and the root system was poorly developed. the number of pods and 1000-grain weight decreased significantly, and the oil yield decreased. In addition, according to the hydroponic culture experiment, if the rape true leaves began to lack phosphorus, the rape leaves were few, the leaves were small, they could only bolt, could not bear fruit, and the grains had no harvest; the five-leaf stage began to lack phosphorus, and the yield decreased, which was only 0.44% of the normal supply of phosphorus nutrition; the yield increased significantly from the ten-leaf stage, which was 27.8% of the normal supply of phosphorus nutrition. Remedial measures: deficiency of phosphorus at seedling stage, ditching with 25,30kg superphosphate per mu or watering, the earlier the better, and the later with 1% superphosphate leaching solution foliar spraying.

Potassium deficiency had significant effects on growth and development, dry matter accumulation, yield and quality of rape. In potassium deficiency, the plants tend to wilt, the seedlings are creeping, the interveinal parts of the leaves protrude upward, causing the leaves to bend arched; the leaves become dark, usually dark blue-green, and the leaf margin or veins lose green, often showing needle-sized spots at first, and finally plaque necrosis occurs. When severe potassium deficiency occurs, the leaves die completely, but do not fall off. In addition, according to the oil observation of the Chinese Academy of Agricultural Sciences, under the condition of extreme potassium deficiency, compared with the normal potassium-supplied rape, the ten-leaf stage after emergence was delayed by about 7 days, and the emergence of bud bolting was delayed by about 20 days. The plants with extreme potassium deficiency began to die at flowering stage. Remedial measures: potassium deficiency in the early stage, ditching with 7-10 kg potassium chloride per mu or 75-100 kg plant ash, and foliar spraying with 0.1% 0.2% potassium dihydrogen phosphate solution in the later stage.

When rape is magnesium deficient, yellow-purple and green-purple flower spots appear on the leaf surface. Remedial measures: if magnesium deficiency is found, foliar spraying with 1%-2% magnesium sulfate solution in time.

When rapeseed is sulfur deficient, the plant is short and light green, which is very similar to nitrogen deficiency; the leaf margin appears large defect and shrinks into a cup, and the back of the leaf, leaf vein and stem turn purplish red. Remedial measures: combined with ploughing, sprinkle 1kg of sulfur powder per mu, or 50kg of gypsum powder. In addition, the appropriate application of ammonium sulfate and other sulfur fertilizer, also has a good effect.

Boron-deficient rape is a boron-loving crop, and its content of boron in dry matter is 32.5-36 times higher than that of wheat, rice and other gramineous crops. Generally, if there are more plants with symptoms of boron deficiency in the field, the yield will be reduced by at least 20% to 30%, and in severe cases, there will be almost no harvest. The symptoms vary greatly due to the degree of boron deficiency, the severe ones atrophied and died at the seedling stage, and the mild ones showed symptoms only after flowering. The root system of the diseased plant is dysplastic, the fibrous root is not long, the epidermis turns brown, some root necks are enlarged and the cortex is cracked. The leaf turns dark green at first, the leaf shape becomes smaller, the leaf quality thickens, becomes brittle, the leaf tip reverses, the wrinkle is uneven. After that, the edge of the middle leaf turns purple from the bottom, develops inward, and then turns blue-purple; the leaf vein and its surrounding tissue turn yellow, resulting in the formation of blue-purple spots. Finally, part of the leaf margin withered and the whole leaf turned yellow and fell off early. After bolting, the growing point shrinks or dies, the embryoid cleaves, the transport system and fertilization are destroyed, carbohydrates remain in the leaves, the flowering is slow, the inflorescence is shortened, the small branches are clustered, the flowering is not fruiting (commonly known as "flower but not fruitful") or the grain is not full, and the pod is as short as turnip at maturity. The pericarp and stem epidermis became purplish red or blue-purple, longitudinal cracks appeared in the middle and lower cortex of the stem, and fissures appeared in the upper part. Prevention and remedial measures: ① soil with serious boron deficiency, 0.5 ~ 1 kg borax per mu as base fertilizer, rape seedlings and transplanting rape, 15-25 kg boron-magnesium fertilizer per mu before transplanting, the effect is good. ② was sprayed on rape leaves with 0.1%-0.2% borax solution at seedling stage, before bolting, early flowering stage or when boron deficiency was found in plants.

Manganese deficiency rape plants are short, chlorosis occurs, young leaves are yellow and white, leaf veins are green, stem growth is weak, yellowish green, woody, flowering and fruiting decreases. Remedial measures: when manganese deficiency is found, foliar spray of 0.1%-0.2% manganese sulfate solution is used in time.

When rape is zinc deficient, it starts from the leaf edge, the leaf color fades, becomes gray-white, and then develops to the middle, and the mesophyll shows yellow patches. The leaf edge of the diseased leaf did not shrink, the middle and lower albino leaves turned outward and the leaf tip drooped. Prevention and remedial measures: 0.5-0.75 kg zinc sulfate per mu was applied at seedling stage; when the plant showed symptoms of zinc deficiency, 0.2% zinc sulfate solution was sprayed on the leaves.

Molybdenum deficiency when rape is short of molybdenum, the leaves wither or scorch, usually twisted in a spiral shape, the old leaves become thicker and the plants are clustered. Remedial measures: when molybdenum deficiency is found, foliar spray of 0.01%-0.1% ammonium molybdate solution is used in time.