Rapeseed plants suffering from nitrogen deficiency show symptoms such as yellowing leaves, stunted growth, and slow development of new foliage. The leaves are small, with red edges and a yellow center, resulting in a distinct red-and-yellow leaf appearance. To address this issue, apply 8 to 10 kg of urea or 20 to 30 kg of ammonium bicarbonate per 667 square meters. Additionally, you can use 7.5 kg of human waste mixed with water, or spray a 1% to 2% urea solution (50 kg) on the leaves, repeating the process 2 to 3 times for best results.
When rapeseed lacks phosphorus, the plants grow slowly, with small and thick leaves that are fewer in number. The leaf edges and petioles turn purple-red, forming purple-red leaves. For treatment, apply 20 to 30 kg of superphosphate or 6 to 8 kg of diammonium phosphate per 667 square meters. Foliar spraying with a 0.2% potassium dihydrogen phosphate solution (50 kg) can also be used, applied 2 to 3 times for effective recovery.
Potassium-deficient rapeseed initially shows yellow spots on the leaves, which gradually develop into brown spots along the edges. The leaves become thick, hard, and brittle, resembling burn-like damage. To correct this, apply 8 to 18 kg of potassium chloride per 667 square meters, or spray a 0.2% potassium dihydrogen phosphate solution (50 kg), repeating the application 2 to 3 times for optimal results.
Boron-deficient rapeseed exhibits blue-purple spots on the leaves, with curled leaf margins and swollen roots. To treat this condition, spray 80 to 100 grams of borax dissolved in 60 to 70 kg of water per 667 square meters, applying it 2 to 3 times. You can also combine this with top-dressing using 500 to 1000 grams of boron fertilizer per 667 square meters for better absorption.
During the seedling stage, drought stress causes poor soil moisture, making it difficult for the roots to absorb water and nutrients. This leads to slow growth, dwarfed plants, and pale red leaves. To prevent this, ensure timely irrigation, using furrow irrigation rather than flooding to maintain proper soil moisture.
Excessive rainfall before winter or poorly drained paddy fields can lead to waterlogging, causing dark red leaves and root rot. To manage this, drain excess water promptly, lower the groundwater level, loosen the soil, improve air circulation, and promote healthy root development to support plant growth.
Winter frost can cause sudden temperature drops below 0°C, leading to red and frozen leaves. To reduce frost damage, combine field cultivation with ditch digging, remove damaged roots, and add organic fertilizers to strengthen plant resilience against cold weather.
Aphid infestations during the growing season can severely damage rapeseed, causing leaf discoloration, curling, and stiffness. To control aphids, use 15 g of 50% acephate wettable powder or 30 ml of 2.5% emulsion per 667 square meters, mixed with 50 kg of water for effective spraying. Regular monitoring and timely intervention are essential for maintaining healthy crops.
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