SOUTHERN FERTILIZER FOR WATERMELON PLANTS

1. General Introduction

– Origin: Watermelon (scientific name: Citrullus lanatus) is a flowering plant species belonging to the family Cucurbitaceae, similar to vine crops. It originates from the West African region. It is cultivated for fruit production.

– Agronomic characteristics and environmental requirements: Watermelon is a herbaceous vine that can spread along the ground or climb trellises, highly adaptable to climate and soil conditions. The optimal temperature for growth is 25-30°C. Growth stops when the temperature drops below 15°C. Watermelon grows best on sandy loam or medium soil. Suitable soil pH is 5.5-6.5.

2. Watermelon cultivation with Southern Fertilizer

2.1. Seed preparation, soil and planting techniques

a. Seeds: Currently, many varieties are available on the market depending on consumer demand. Popular varieties include Sugar Baby watermelon, imported from the USA (Sunblest, Harris Moran, Eagle) and Thailand (Chia Tai, Trai Bau). The Sugar Baby variety has been widely cultivated for years, especially for Lunar New Year displays. Fruits are round, 3-5 kg on average, dark green rind, red flesh, growing period 65-70 days, open-pollinated variety. Hybrid seedless F1 varieties imported from the USA, Thailand, Taiwan such as NH-Tan Nhat, NH-Thang Loi No.1, NH-Hung Huy, NH-Gia Linh, NH Quoc Hoa, NH–Quoc Vuong. An Tiem 95: F1 hybrid, large round fruit, 6-7 kg, dark rind with strong stripes, red flesh, good quality…

b. Soil: Watermelon can be planted on various soil types. However, loose and well-drained soil is most suitable. Soil should be well plowed and ridged, with mulch film applied or without ridges in some conditions.

Fertilizer needs vary depending on soil fertility. Poor, sandy, or degraded soils require additional nutrients to meet crop demands.

c. Planting techniques:

– Planting seasons:

+ Early crop (Christmas melons): sow in October, harvest around Christmas (20/12 – 30/12).

+ Main crop (Tet melons): sow in November, harvest for Lunar New Year.

+ Summer crop: sow from February to May.

– Direct seeding / nursery:

+ Direct sowing: Punch planting holes 10 cm deep, apply ash-compost to retain moisture. Sow 2-3 pre-germinated seeds 2-3 cm deep, cover with ash or fine soil. Thin weak seedlings later.

+ Nursery: Most convenient for better seedling care and land preparation. Make nursery beds 60-80 cm wide, 15-20 cm high, in well-lit and ventilated areas. Transplant when ready.

Seed requirement: 0.5–1.0 kg/ha.

– Planting: Transplant seedlings at 5–7 days old. Density: 2.3–2.5 m x 0.5–0.6 m, about 9,000 plants/ha. Carefully remove nursery bag and place seedling into pre-made hole. Water thoroughly.

2.2. Fertilization

SFJC Bio-Gold G.A.P Organic Fertilizer is a clean fertilizer product from Southern Fertilizer JSC, made from 100% plant-based materials, suitable for G.A.P farming, containing 55% organic matter, natural nitrogen sources, Humic acid, Fulvic acid, Trichoderma fungi, etc., helping stabilize the soil ecosystem, enhance beneficial microorganisms, reduce harmful fungi, limit nutrient leaching, stimulate stronger root formation, and prevent soil degradation.

Supe Lan Long Thanh contains 16% available phosphorus, 10% sulfur, 15% calcium, and other secondary & micronutrients that stimulate root and shoot formation, promote flower bud differentiation. Quickly dissolves and absorbs in soil, suitable for many crops.

Southern Fertilizer NPK 20-20-15+TE (single-color blend). A modern steam granulated product, high nutrient content, enhancing shoot growth, branching, and strong plant development.

Southern Fertilizer NPK 15-9-13+TE (granular type) — specialized for vegetables, highly soluble and contains balanced macro, secondary and micro nutrients, ensuring strong plant health, reduced pests and diseases, increased biomass, yield, and quality.

2.3. Crop care

– Weeding: After each side-dressing, weed around roots and on beds to reduce nutrient competition.

– When side-dressing under mulch, pierce small holes between two plants to apply fertilizer and water. Apply based on plant growth: 1st side-dress at 5–7 leaves, 2nd at flowering, 3rd at fruit setting. Fertilizer may be applied directly or dissolved in water.

– Watering: Sprinkler or furrow irrigation depending on field conditions. Under mulch, use furrow irrigation—fill and drain the furrows within the same day. Water frequently when plants are young and roots are shallow.

– Pruning vines: Remove excess vines to avoid nutrient waste and maintain strong main vines for fruit development.

– Vine training: Keep vines straight and parallel along the beds, perpendicular to planting rows.

– Pollination: Manual pollination is necessary, done from 7–9 AM. Pick freshly opened male flowers and transfer pollen evenly to freshly opened female flowers.

– Fruit selection: Choose fruit at leaf position 15–20 on the main vine. Keep only one fruit per plant for market-standard size and shape.

3. Integrated pest management

– Common pests & diseases: Cucumber beetles; leaf miners; thrips; armyworms; leaf spot, stem cracking and gummosis caused by Mycosphaerella melonis, and downy mildew caused by Phytophthora melonis.

– Control measures: Integrated management including thorough soil tillage; field sanitation before planting; using clean irrigation water; insect traps; manual removal; approved pesticides; rotate chemicals to prevent resistance.

4. Harvesting

– Harvest watermelon at 80–90% ripeness, about 60–70 days after planting depending on variety and market distance. Yield ranges 18–45 tons/ha.

– Long-term storage method: In some areas, watermelons are soaked in 15% salt water for 3–5 days, then dried, coated with juice from watermelon leaves and vines, placed in soft plastic bags and stored underground.

Chemical-free preservation in hot weather: Select newly ripe melons, remove the stem. Wrap each fruit tightly in plastic bags and keep in shade. Maintain low temperature and natural low oxygen. Place on a straw bed and inspect frequently. Remove any spoiled fruit immediately. Storage duration: 35–40 days.

Collected and compiled by

Le Minh Giang & Danh Tri Tam