When rapeseed suffers from nitrogen deficiency, the leaves turn yellow, growth becomes stunted, and the plants appear short and weak. Nitrogen-deficient symptoms often appear during drought or when the soil has been over-cropped and lacks nutrients. This condition can significantly reduce yield and overall plant health.
To address nitrogen deficiency, it is recommended to apply 7.5 kg of urea per acre. Alternatively, you can dissolve 15 to 20 kg of ammonium bicarbonate in 500 to 700 kg of water and apply it as a foliar spray. These treatments help restore nutrient balance and promote healthy growth.
Phosphorus-deficient rapeseed exhibits slow growth, with smaller, thicker leaves that have a dark green or grayish-green color and lack luster. The petioles may develop purple coloration, and there might be purple veins or patches along the leaf edges. Leaves are fewer in number compared to healthy plants, and the tips may show red discoloration.
For phosphorus deficiency, applying 25 to 30 kg of superphosphate per acre is effective. Additionally, spraying the leaves with potassium dihydrogen phosphate two or three times can help improve phosphorus uptake and support plant development.
Potassium-deficient rapeseed typically shows symptoms first on older leaves, gradually moving toward the younger ones. Yellow spots appear initially, followed by "edge burn" and pale brown spots. The leaves become thick, hard, and brittle, with a scalded appearance. After death, these tissues remain brown, indicating severe potassium deficiency.
To correct potassium deficiency, apply 7.5 to 10 kg of potassium chloride per acre mixed with 500 to 700 kg of water. You can also mix it with 100 to 150 kg of wood ash for better results. This helps replenish potassium levels and improves plant resilience.
Boron-deficient rapeseed often shows poor root development, with no root hairs or lateral roots. The roots may have small knob-like growths at the tip, and the root bark turns brown. Purple or blue-purple patches appear on the leaves, and the leaf margins curl inward. The base of the plant (rhizome) may swell. During flowering, boron deficiency can lead to “flowers without pods,†where flowers do not develop into seed pods.
To treat boron deficiency, apply 150 to 200 grams of borax per acre in 150 to 200 kg of water. Alternatively, use 50 to 100 grams of borax in 50 kg of water and spray the foliage during sunny afternoons for best absorption. Boron is essential for reproductive growth and should be applied carefully to avoid toxicity.
By identifying and addressing these nutrient deficiencies early, farmers can significantly improve the health and productivity of their rapeseed crops. Regular soil testing and balanced fertilization practices are key to maintaining optimal growing conditions.
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