While greenhouse cultivation dominates the market for watermelons, open-field cultivation remains one of the main production methods. Watermelons can usually be planted when the soil temperature stabilizes at around 15°C. However, for high yields and good quality in open-field watermelon cultivation, proper fertilization is crucial. So, how should watermelons in open fields be fertilized? Let's find out.
How to Fertilize Watermelon in Open Field?
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Base Fertilization: For open-field watermelon cultivation, it is advisable to select plots with convenient irrigation and drainage, deep soil, and abundant organic matter. After selecting the site, deeply turn the soil, expose it to sunlight for half a month, break it into fine particles, and create continuous ridges and furrows 2.5 meters long. The ridge height should be 40 centimeters on one side and 20 centimeters on the other side. Then, dig planting furrows 25 centimeters deep and 40 centimeters wide on the high side of the ridge. Apply 1000-1500 kilograms of decomposed farmyard manure, 25 kilograms of compound fertilizer, 1.5-2 kilograms of borax, and 4 kilograms of magnesium sulfate per acre as base fertilizer.
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Seedling Fertilization: Seedling fertilizer refers to the fertilizer applied during seeding or transplanting of watermelon seedlings. The amount of seedling fertilizer is much less than that of base fertilizer. Both single-element and compound fertilizers can be used for seedling fertilization.
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Topdressing Fertilization:
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Seedling Stage Fertilization: When watermelon seedlings grow two true leaves and are 15 centimeters tall, create a shallow arc-shaped furrow 15 centimeters away from the seedlings and apply nitrogen fertilizer or nitrogen-phosphorus-potassium compound fertilizer. Generally, apply 8-10 grams of nitrogen per plant.
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Vine Extension Fertilization: After watermelon vines elongate, apply vine extension fertilizer before watering. Generally, apply 10-20 kilograms of high ecological fertilizer and 20-25 kilograms of urea per acre. It is usually preferable to apply vine extension fertilizer in furrows.
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Fruit Enlargement Fertilization: After watermelon fruit set, when the fruit rapidly enlarges, apply fruit enlargement fertilizer in a split application. The first application should be when the fruit is the size of an egg. Dig a trench 30-40 centimeters away from the base of the plant on one side, and apply 225-300 kilograms of ammonium phosphate and 75-110 kilograms of potassium sulfate per hectare. The second application should be when the fruit is the size of a bowl. Apply 80 kilograms of urea, 60 kilograms of calcium superphosphate, and 60 kilograms of potassium sulfate per hectare.
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Recovery Fertilization: Immediately after the first harvest of watermelon, apply the fourth round of fertilizer. Apply efficient potassium-phosphorus compound fertilizer, such as potassium dihydrogen phosphate foliar fertilizer, at a rate of 10-15 kilograms per acre. This will quickly supplement phosphorus and potassium elements to the plants, promote crop growth and flower bud differentiation, increase the number of flower buds, and prevent premature vine and leaf senescence.
In summary, fertilization is a crucial part of open-field watermelon cultivation management. Focus on mastering base fertilization, seedling fertilization, and topdressing fertilization. Additionally, execute the corresponding fertilization plan according to the different growth stages of watermelons to achieve optimal results.
