Watermelon wilt disease and anthracnose are common problems in watermelon cultivation, especially in low-lying areas with poor drainage, excessive nitrogen fertilizer use, and inadequate ventilation. Many farmers lack proper knowledge about fertilization, often believing that "more dung means better growth" or that applying more nitrogen and phosphate fertilizers is sufficient, while neglecting potassium and micronutrients. This unbalanced approach hinders the plant's ability to absorb nitrogen and phosphorus effectively, leading to soil nutrient imbalances. Over time, this results in compacted soil, which deteriorates growing conditions and increases the occurrence of pests and diseases.
To prevent further degradation, it’s essential to improve soil health through scientific and rational fertilization practices. First, apply a base fertilizer. Typically, 40 kg of ecological 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 should be applied. It’s best to place the fertilizer in furrows or mix it into the soil after spreading.
Second, during the seedling stage, if the base fertilizer already provides enough nutrients, no additional fertilizer is needed. However, if the base fertilizer was insufficient, a small amount of seedling fertilizer can be applied when the plant has two true leaves. A light application of 4–5 kg of urea per acre before watering the seedlings is recommended. Avoid over-fertilizing too close to the roots, as this may burn the seedlings.
Third, during the vine extension phase, apply fertilizer after the vines have spread. A typical recommendation is 10–20 kg of ecological fertilizer, 20–25 kg of urea, and 10–12 kg of potassium sulfate per acre. Spread the fertilizer near the furrows but not too close to the plant to avoid root damage, and cover it with soil.
Fourth, apply top-dressing sparingly. Before and after flowering, it’s a critical period for fruit setting. Usually, no extra fertilizer is needed at this stage. However, once the fruit reaches the size of a duck egg, it enters the peak absorption phase. If nutrients are lacking at this point, it can affect fruit development and lead to early plant decline, reducing both yield and quality. In such cases, a small amount of compound fertilizer (5–10 kg per acre) is advisable.
Finally, in the later stages, foliar sprays can help supplement nutrient uptake. After the fruits begin to swell, the roots’ ability to absorb nutrients decreases. Spraying a 0.2% to 0.3% urea solution can help maintain fruit quality and ensure proper ripening. These steps, when followed consistently, can significantly improve watermelon health and productivity.
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