Cucurbit Fertilizers - Buy from Manufacturer Dünger

Three Feeding Phases for Cucurbits: Growth, Flowering, Fruiting

Watermelon, melon, cucumber and zucchini all belong to the cucurbit family and share identical nutritional logic: before flowering - balanced NPK to build a strong plant and root system, at flowering - boron for fruit set, at fruiting - maximum potassium for sweetness, size and flesh density.

Universal cucurbit feeding schedule:

1. At transplanting or one week after direct sowing: SKU 1 (N12-P15-K15-S15) - 20-25 g/m².
2. At first tendril / active vine growth: SKU 1 - 20-25 g/m² every 10-14 days.
3. When first flower buds appear: SKU 18 (N12-P15-K15-S15-B0.35%) - 20-25 g/m².
4. At fruit set and fruit sizing: SKU 19 (P23-K30) - 20-25 g/m² every 10-14 days. Stop nitrogen.

Potassium: Why It Determines the Sweetness of Watermelon and Melon

Of all nutrients, potassium K most directly influences cucurbit fruit quality. The mechanism: K activates enzymes that synthesize sugars (sucrose, fructose, glucose) and transports them from leaves into the fruit. The more available K during fruit sizing - the higher the Brix (sugar content).

Specific K effects for each crop:

• Watermelon: K raises Brix by 2-3 points, stimulates lycopene synthesis (vivid red flesh), reduces rind thickness. Without adequate K: watery, pale-pink flesh, thick rind.
• Melon: K synthesizes volatile aromatic compounds (esters, alcohols) - their concentration determines the characteristic honeyed fragrance. Without K melon is sweet but lacks aroma.
• Cucumber: K provides crispness, even green skin color and extended shelf life. K deficiency = soft, watery cucumbers.
• Zucchini: K builds wall thickness and flesh density. Without K: hollow, soft fruits.

DÜNGER SKU 19 (P23-K30) - zero chloride, zero nitrogen, maximum P and K. 20-25 g/m² or dissolved 20-25 g/10 L. Start at first fruit set and continue every 10-14 days.

Boron at Flowering: Why Cucurbits Drop Flowers Without It

Cucurbits have separate male and female flowers on the same plant. For fruit to set, pollen from a male flower must reach the stigma of a female flower and grow a pollen tube.

Boron B is directly required for pollen tube elongation. With B deficiency:

• Pollen forms but the pollen tube cannot grow.
• Pollination fails and the female flower aborts.
• Only isolated fruits set instead of abundant fruiting.
• With severe deficiency: deformed, corky-cracked fruits.

DÜNGER SKU 18 (N12-P15-K15-S15-B0.35%) - apply when first flower buds appear, before mass flowering begins: 20-25 g/m². B present in tissues when flowers open = normal pollination = abundant fruit set. Additionally: foliar boric acid 1 g/10 L at the start of mass flowering.

Excess Nitrogen in Watermelon: Dark Green Vines Instead of Sweet Fruit

Watermelon is the most sensitive cucurbit to excess nitrogen. With too much N during fruiting:

• Vines are dark green, vigorous and keep growing late in the season.
• Fruits remain small or few: the plant 'invests' in leaf mass rather than fruit.
• Flesh is watery, pale pink and bland.
• Thick rind - the classic sign of excess N.

As soon as the first watermelons reach fist size - stop nitrogen completely and switch to SKU 19. The same rule applies to melons.

Calcium and Magnesium for Cucurbits

Calcium (blossom-end rot): a dark, leathery patch on the blossom end of watermelon or zucchini - this is blossom-end rot, identical to tomatoes. Cause: Ca deficiency in the developing fruit. Triggered by inconsistent watering (drying out between waterings blocks Ca transport). Prevention: calcium nitrate 10 g/10 L root feeding at fruit set + consistent watering.

Magnesium (yellowing leaves): cucurbits readily show Mg deficiency - older leaves yellow between green veins. Treatment: foliar magnesium sulfate 20 g/10 L twice. Often triggered by excess K (K and Mg compete for uptake), so monitor leaves when heavily feeding SKU 19.

Nutrient Deficiency Signs in Cucurbits and How to Fix Them

• Pale leaves, slow growth - N deficiency. Apply SKU 1.
• Few fruits, flowers dropping - B deficiency. SKU 18 at flowering + foliar boric acid 1 g/10 L.
• Dark patch on fruit tip - Ca deficiency (BER). Calcium nitrate 10 g/10 L + consistent watering.
• Older leaves yellow between green veins - Mg deficiency. Magnesium sulfate 20 g/10 L foliar.
• Bland, watery fruit - K deficiency or excess N. Switch to SKU 19, stop N fertilizers.
• Deformed, corky-rough fruits - B deficiency. Foliar boric acid spray.

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