In the course of rapeseed growth and development, various leaf color changes such as red, yellow, brown, dark purple, blue-purple, and gray can occur due to improper management or nutrient deficiencies. These symptoms are often early indicators of underlying problems that need timely attention.
**First, Red Leaves**
Red leaves in rapeseed can be caused by several factors. During the seedling stage, drought can lead to slow growth, stunted plants, and a light red discoloration of the leaves. To address this, proper irrigation is essential—ditch irrigation should be used, avoiding waterlogging that could damage young plants.
Waterlogging during the seedling stage can also cause red leaves. In such cases, improving drainage by digging deep trenches and lowering the groundwater level is crucial.
Aphid infestations can cause leaves to become stiff and turn red. A recommended treatment is to spray 10-20g of 50% anti-inferiority WP in 20-30kg of water.
Frost damage during winter, when temperatures drop below 0°C, can also result in red leaves. To reduce frost risk, farmers can mix about 100kg of plant ash per acre with the soil.
**Second, Yellow Leaves**
Yellowing of leaves can be due to nitrogen deficiency. Symptoms include stunted growth, small leaves, and yellowing starting from the lower parts. Applying 15-20kg of ammonium bicarbonate per acre or using a 1%-2% urea solution for foliar spray can help.
Sulfur deficiency causes yellowing that starts from the new leaves, unlike nitrogen deficiency which affects older leaves first. Adding 10kg of gypsum powder per acre during cultivation can help correct this issue.
Acidic soil conditions may lead to yellow leaves, especially in new growth. Applying 50kg of lime and 50kg of ash per acre can neutralize soil acidity and improve leaf color.
**Third, Brown Leaves**
Brown leaves are typically a sign of potassium deficiency. Symptoms include yellow spots on old leaves, followed by browning at the tips. At the seedling stage, applying 7-10kg of potassium chloride per acre or spraying a 0.1%-0.2% potassium dihydrogen phosphate solution (50-80kg per acre) can help. Repeating the spray 2-3 times improves results.
**Fourth, Dark Purple Leaves**
Dark purple leaves indicate phosphorus deficiency. Plants grow slowly, leaves are small, and purple spots appear on the edges. At the seedling stage, mixing 25-30kg of calcium phosphate per acre into the soil helps. For later stages, spraying a 1% superphosphate solution 2-3 times is effective.
**Fifth, Blue-Purple Leaves**
Blue-purple leaves are a symptom of boron deficiency. Leaves initially appear dark green, then become smaller, brittle, and curl. Spraying 50-100g of borax in 50kg of water during the seedling, flowering, or early bloom stage, repeated 2-3 times, can effectively address this issue.
**Sixth, Gray Leaves**
Gray leaves signal zinc deficiency. The discoloration starts at the leaf margins, progressing inward, with irregular white-yellow patches. The veins remain green. In the seedling stage, mixing 1.5kg of zinc sulfate with 30-40kg of dry soil per acre is recommended. Later, spraying a 0.3%-0.4% zinc sulfate solution 2-3 times (50-80kg per acre) helps restore leaf health.
By understanding these symptoms and taking prompt action, farmers can significantly improve rapeseed health and yield. Regular monitoring and timely interventions are key to successful crop management.
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