Watermelon wilt disease and anthracnose are common in watermelon crops, especially in low-lying areas with poor drainage, excessive nitrogen fertilizer use, and inadequate air circulation. Many farmers lack proper knowledge about fertilization and hold misconceptions such as "manure and groundwater are enough, no need for expert advice" or the belief that applying more nitrogen and phosphate fertilizers is sufficient, while neglecting potassium and micronutrients. This imbalance leads to reduced efficiency in nitrogen and phosphorus uptake, creating an unbalanced soil environment. Soil compaction worsens, harming the growth conditions of watermelons and increasing the occurrence of pests and diseases.
To prevent this from getting worse, it's essential to improve soil health and adopt scientific fertilization practices. First, apply base fertilizer. A typical base application includes 40 kg of organic fertilizer per mu, or 5,000 kg of farmyard manure, along with 40–50 kg of calcium magnesium phosphate, 5 kg of urea, and 8–10 kg of potassium chloride. It should be applied in furrows or mixed into the soil after being spread on the bed.
Next, during the seedling stage, if the base fertilizer already provides enough nutrients, no additional fertilizer may be needed. However, if the base fertilizer was insufficient or not used at all, a small amount of seedling fertilizer can be applied when the plant has two true leaves. A recommended dose is about 4–5 kg of urea per acre before watering the seedlings. Be careful not to over-fertilize or apply it too close to the roots, which could burn the plants.
After the vines start to spread, it’s time for vine extension. Apply 10–20 kg of organic fertilizer, 20–25 kg of urea, and 10–12 kg of potassium sulfate per acre. Spread the fertilizer near the ditches but keep it away from the main plant to avoid root damage, then cover with soil.
Before and after flowering, it's a critical time for fruit setting. Usually, no top-dressing is needed. However, once the young melons reach the size of a duck egg, they enter their peak growth phase. If nutrients are lacking during this period, it can affect fruit development and lead to early plant decline, reducing both yield and quality. At this stage, a light application of compound fertilizer (about 5–10 kg per acre) is recommended.
Finally, in the later stages, when the roots' ability to absorb nutrients declines, foliar sprays can help. Spraying a 0.2% to 0.3% urea solution can supplement nutrient uptake and support proper ripening of the watermelons. These steps ensure balanced nutrition and healthier crops, leading to better yields and quality.
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