When rapeseed plants suffer from nitrogen deficiency, their leaves turn yellow, growth becomes stunted, and the plants appear short and weak. Nitrogen-deficient symptoms are often observed during drought or after fertilizer depletion. This condition can significantly impact 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 15–20 kg of ammonium bicarbonate in 500–700 liters of water and apply it to the soil. These treatments help restore nutrient balance and promote healthy growth.
Phosphorus-deficient rapeseed exhibits slow growth, with smaller leaves that become thicker and darker in color—often appearing dark green or grayish green. The leaves may lack luster, and petioles might show purple discoloration. In severe cases, purple veins or patches can be seen along the leaf edges. Leaves may also be fewer in number, and their growth appears sluggish with a reddish tinge.
To correct phosphorus deficiency, apply 25–30 kg of superphosphate per acre. Another effective method is to spray the leaves with potassium dihydrogen phosphate two or three times. This helps improve nutrient uptake and supports better development.
Potassium-deficient rapeseed typically shows symptoms starting from the older leaves, gradually moving toward the younger ones. Initial signs include yellow spots on the leaves, followed by the development of "edge-browning" and pale brown lesions. The leaves become thick, hard, and brittle, and the tissue may appear scorched before wilting. After death, these tissues retain a brown color.
To treat potassium deficiency, apply 7.5–10 kg of potassium chloride per acre mixed with 500–700 liters of water. You can also mix it with 100–150 kg of wood ash to enhance nutrient availability.
Boron-deficient rapeseed has a high demand for boron, but many soils contain low levels of this essential micronutrient. As a result, rapeseed is particularly prone to boron deficiency. Affected plants exhibit stunted root growth, with no root hairs or lateral roots. Some roots may develop small, knob-like swellings at the tip, and the root bark turns brown. Leaves may display purple or blue-purple patches, and their edges may curl inward. The stem may also become swollen.
During the flowering stage, boron deficiency can lead to a condition known as “flowers without pods,†where flowers open but fail to produce seed pods.
To correct boron deficiency, apply 150–200 grams of borax per acre in 150–200 liters of water. Alternatively, use 50–100 grams of borax in 50 liters of water and spray the foliage during the afternoon on a sunny day. These applications help ensure proper boron uptake and prevent long-term damage to the crop.
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