The Latest Cultivation Techniques and Method Guide for Qilin Watermelon

Qilin watermelon is a new variety developed through breeding research, and it has very high requirements for the growing environment, soil and sunlight. However, because it takes only about 60 days from planting to flowering and from flowering to harvest, even though cultivation is demanding, the short cycle, good taste and quick returns mean farmers in Wenzhou and Hainan are still very willing to grow it.

Site Selection and Greenhouse Construction

Choose a plot with high terrain, good drainage and deep soil to build the greenhouse. Low-lying plots with poor drainage are not suitable for greenhouse construction. The plot must not have grown cucurbit crops within 3 years. Jiangxi mostly uses paddy fields to grow “Qilin watermelon”.

Greenhouses for growing watermelon generally use a simple bamboo strip structure. A north-south orientation is best, with a width of 4.5-5 m, a length of 25-30 m and a height of 1.8-1.9 m. The spacing between 2 greenhouses in the same row is 80-100 cm, and the distance between two rows of greenhouses is 2.5-3 m. The moso bamboo strips used for building the greenhouse are generally about 7 m long and about 5 cm wide.

When building the greenhouse, on the plot where it will be built, draw the side lines according to the greenhouse span, and at corresponding positions on the two long side lines, use a steel rod to make a small hole about 30 cm deep every 50-60 cm. Then insert the moso bamboo strips into the pre-made small holes. When inserting the bamboo strips, alternate the base (thick) end and the top (thin) end. At the top of the greenhouse, use a horizontal tie rod to firmly tie the arch rods so that the whole greenhouse is connected as one, with all arch rods at the top at the same horizontal position. Then install a diagonal brace on each side at both ends of the greenhouse, cover it with greenhouse film, press the soil firmly over the film edges so the film is stretched tight, and leave greenhouse doors at both ends.

Digging Ditches and Making Beds

1. Digging ditches: Dig drainage ditches around the greenhouse, requiring a ditch depth of 50 cm and a width of 30-50 cm. The drainage ditches between greenhouses should be 25 cm wide and 25-30 cm deep. In heavy rain, water in the greenhouse ditches must be able to drain away along the ditches, with no water accumulation, otherwise watermelon root rot is likely to occur.

2. Soil improvement: When the watermelon plot lies idle in winter, the soil should be deeply plowed and exposed to sun and frost. If the soil is too acidic, quicklime can be used to neutralize the acidity. Generally, 100-150 kg of quicklime per mu is broadcast on the ground, then the land is plowed.

3. Making beds: Watermelon is suitable for cultivation in deep ditches and high beds. Generally, a 4.5-5 m wide greenhouse is made into 2 beds, each about 2.3 m wide and roughly turtle-back shaped. Each greenhouse only has one ditch dug in the middle, 40 cm wide, ditch depth 20 cm, with no ditches on either side.

4. Applying base fertilizer: One month before planting, apply 2000 kg of decomposed organic fertilizer, 25 kg of calcium magnesium phosphate fertilizer, 15 kg of potassium sulfate compound fertilizer and 50 kg of rapeseed cake per mu. For boron-deficient soil, boron fertilizer should also be applied, with 1.5 kg of borax per mu. The base fertilizer should be applied in a ditch opened in the middle of the bed, then covered with soil.

5. Laying drip irrigation pipes and plastic film: Half a month before planting, level the bed surface, lay the drip irrigation, and cover with plastic film and greenhouse film to raise the temperature. Planting can only be done after the ground temperature is above 15°C.

Seedling Raising Techniques

Cultivation generally uses the method of large greenhouse + small greenhouse + plastic film. If conditions permit, use electric heating wires to sow and raise seedlings in mid-to-late December, and transplant in early-to-mid February. Without heating equipment, it is better to sow and raise seedlings in mid-to-late February and transplant in late March.

1. Selection of seedbed site: Seedlings should be raised in a greenhouse, preferably in a plot close to the cultivation field, with high and dry terrain, shelter from wind, facing the sun, good light conditions and convenient drainage and irrigation.

2. Preparation of nutrient soil: The nutrient soil should be loose, fertile and water-retentive, and needs to be composted more than 1 month in advance. Take paddy field soil that has not grown cucurbit crops for more than 3 years, add decomposed farmyard manure, compound fertilizer, calcium magnesium phosphate fertilizer and plant ash, etc., mix well, then cover with plastic film and compost. Paddy field soil : decomposed farmyard manure : plant ash = 5:3:2. At the same time, add 5 kg of calcium magnesium phosphate fertilizer and 2 kg of crushed compound fertilizer to 1 cubic meter of nutrient soil. During mixing, it can be disinfected with 50% carbendazim 600-fold solution or 1% formalin solution, turned and sprinkled evenly, dried and sieved.

3. Seedbed preparation: Generally about 400 seedlings are needed per mu of watermelon. Build the seedling greenhouse in advance and make an electric heating hotbed. Make the seedbed 1.3 m wide, dig it into a concave bed 5 cm deep, with length according to need. To keep warm, lay a layer of old plastic film underneath, fill in 2 cm thick rice husk, cover with a layer of disease-free fine soil, pat the soil surface flat, then lay the heating wires. Lay 1000 watts of heating wire per 10 sq m of seedbed, sparser in the middle of the bed and slightly denser on both sides. Connect the power supply and switch, choose 10 cm × 10 cm plastic nutrient pots, fill them with nutrient soil and arrange them on the heating wires of the seedbed, then cover with film to keep warm and raise the temperature.

4. Germination acceleration and sowing: Sun the seeds for one day before sowing. For germination acceleration, first soak in 55°C warm water for 15-30 minutes, stirring while soaking. Or treat with 1% formaldehyde solution for 10 minutes, rinse clean with clear water, then soak the seeds for 6-8 hours. Then rub and wash off the mucus on the seed surface, wrap the seeds in a wet cloth, and place at 28°C-32°C for germination acceleration (human body temperature or an electric blanket can be used for germination acceleration). Generally after 24-30 hours they whiten and can be sown. Two days before sowing, water the nutrient soil thoroughly once and energize the seedbed to preheat it. Sow when the soil temperature is controlled above 25°C. Sowing is best done on a sunny morning, one seed per pot, with the seed placed flat. After sowing, cover with 0.5 cm of fine soil, sprinkle water appropriately, then lay plastic film and build a small arch shed to keep warm.

5. Seedling stage management

① Temperature: Before emergence, keep the small arch shed at a relatively high temperature, preferably 28°C-30°C during the day and 18°C-25°C at night. When 30% of seedlings have emerged, promptly remove the plastic film covering the nutrient pots and the small arch shed film for ventilation. After emergence, keep the greenhouse temperature at about 25°C during the day and 15°C-18°C at night. If the temperature is insufficient during seedling raising, use electric heating wires to energize and heat.

② Humidity: The water management of the seedbed nutrient soil follows the principle of “better dry than wet”. From emergence to the unfolding of true leaves, water as little as possible; afterward, decide according to whether the nutrient soil is dry or wet. Do not water if the soil does not turn white; if watering, water thoroughly. Watering is best done at noon. The greenhouse should be ventilated as much as possible while ensuring temperature, to reduce humidity and prevent diseases. If after a long rain the sky clears and seedling leaves wilt, properly cover with a shade net to shade them and help the seedlings recover. Stop watering 5-7 days before transplanting. Generally no topdressing is needed at the seedling stage. If the seedlings are thin and weak, use 0.3% urea and potassium dihydrogen phosphate for foliar topdressing.

③ Light: During the seedling stage, let the seedlings receive more light, and remove the small arch shed film during the day. In continuous overcast and rainy weather, artificial supplementary light should be used, with 300 watts of incandescent bulbs per 10 sq m of seedbed.

④ Pest and disease control: Because the seedbed temperature is low and humidity is high when raising seedlings in early spring, damping-off and many other diseases easily occur. In addition to reducing greenhouse humidity as much as possible, pesticides such as Previcur, Daconil and metalaxyl mancozeb can be used for control. If there is continuous low-temperature, weak-light overcast and rainy weather, pesticides can be mixed with dry fine soil and broadcast in the seedbed. Spray once with 50% carbendazim 600-fold solution before transplanting and carry the pesticide to the field.