Detailed Explanation of Key Techniques for Growing Large-Fruit Watermelons
1. Site selection
1. Soil quality: Choose sandy soil that is loose and well aerated. Black soil with a sand content of about 30-40% is best. For clay soil, increase the number of tillage operations to improve soil permeability; autumn plowing is best. Once the vines have grown to more than 30cm, do not deep-plow, to prevent damaging the roots.
2. Terrain: The plot should be level, with a slight slope, facing the sun and sheltered from the wind, with convenient drainage and irrigation, no waterlogging (not a seepage-prone plot), close to a water source, easy to manage, and with convenient transportation for shipping.
3. Previous crop: Virgin land or land left fallow for a second year is best; millet stubble, wheat stubble, corn stubble, sorghum stubble, foxtail millet stubble, and rice stubble are all acceptable. There must be at least 6-7 years without growing watermelon, melon, or vegetables, with neither continuous cropping nor adjacent cropping. For planting melons after rice, the soil must be deep-plowed in the autumn of the year before to mature the soil.
2. Fertilization
Watermelon fertilization should be based mainly on basal fertilizer, with balanced fertility (nutrients), which helps improve disease resistance and stress resistance. Therefore, per mu, apply 5000 kg of fully decomposed high-quality farmyard manure (preferably sheep manure, chicken manure, or pig manure; horse manure and cow manure are also acceptable), 50 kg of superphosphate (superphosphate), and 30 kg of three-element compound fertilizer (or 20 kg of diammonium phosphate and 15 kg of potassium sulfate).
Fertilization method: First, use a large plow or deep-loosening shovel to deep-loosen the original furrow where the watermelon will be planted, to a depth of 20-30 cm, then irrigate thoroughly. After the water seeps down, evenly filter the basal fertilizer into the furrow (fertilize 2 furrows, leave 2 furrows empty). After the basal fertilizer is filtered in, break the original ridge to cover the basal fertilizer. After covering the basal fertilizer, filter fertilizer once more onto the new ridge, then close the ridge to form layered basal fertilization. After closing the ridge, press it once with a roller, then cover it with 70 cm wide plastic film, press the film down tightly, and prepare for transplanting.
3. Plant spacing and row spacing
1. Row spacing: Each ridge is 65-70 cm, plant 2 ridges and leave 2 ridges empty, for a row spacing of 2.1 m.
2. Plant spacing: 80-100 cm. Plant 350-500 plants per mu.
4. Seedling raising and transplanting
1. Preparation of seedling trays
Choose seedling trays with good water permeability in the specifications 60cm*40cm*5cm or 60*40*8cm, or sprouting trays for soilless bean sprouts, or other containers. Fill the trays with sand as large as yellow glutinous millet grains (medium sand), wash it clean with clear water to make pure sand (no soil), and put it into the sprouting trays to a thickness of 3-4 cm, ready for sowing.
2. Germination
At room temperature, put the seeds into a basin, add cool water to the basin and soak the seeds for 8 hours, then take them out and wipe off the moisture and sticky substances on the seed surface with coarse cloth or a towel. To ensure uniform germination, it is best to crack the seeds open. Insert the seed into the empty space behind the blade of a nail clipper and in front of the pivot, and pinch; hearing a click is enough. Then place the cracked seeds evenly on a slightly wrung-out (but not dry) wet towel, 0.5-1.0 cm thick, cover with another layer of slightly wrung-out wet towel, and place at a constant temperature of 25-30°C to germinate for 24-36 hours, preferably until the seeds show white.
3. Sowing and seedling raising
Place the seeds evenly (1.0cm*1.0cm) on the previously prepared sand tray, cover with another layer of pure sand (medium sand) 1.0 cm thick, and water thoroughly immediately. Place indoors or in a warm shed, with daytime not exceeding 30°C and nighttime not below 18°C; seedlings will emerge in about 3-4 days. Because sand has good water permeability and is prone to water shortage, water once more on the 3rd day after sowing and watering. You may also cover the seedling tray with a layer of film, and remove it immediately after seedlings emerge, to preserve moisture and warmth. After that, water once every 3-4 days, and apply a foliar liquid fertilizer once 5-7 days after emergence. When watering, add diammonium phosphate fertilizer to the water to a concentration of 0.3% (that is, 10 jin of water with 0.3 qian of fertilizer). After that, water with nutrient solution once every 5-7 days. Too high a temperature, too much water, or too much fertilizer can easily cause excessive vine growth, so attention must be paid to controlling excessive growth. Control water, temperature, and ventilation appropriately; seedling age is 15-20 days. Harden the seedlings 5-7 days before planting (hardening temperature 15-17°C). (When raising seedlings, raise some extra, 20% more than the actual number of seedlings needed, to prepare for seedling selection.) The above method is called raising cotyledon seedlings, also called large-bud seedlings. It saves time, saves money, has low cost, and is easy to manage; 1-2 trays are enough for 2 mu of land. For open-field cultivation of large-fruit watermelons, it is better to germinate and sow when the atmospheric temperature steadily passes 15°C and the soil temperature steadily passes 10°C, but the moisture conditions for seedling emergence and seedling growth must be ensured. When sowing, leave a seed pit to prevent the cotyledons from contacting the plastic film at emergence and burning the seedlings from high temperature. After sowing, immediately cover with plastic film, and after emergence, ventilate promptly according to seedling condition and temperature to prevent burning the seedlings.
4. Planting (transplanting)
When planting (cover with plastic film first, then plant), use a small trowel to dig pits at a plant spacing of 80-100 cm (dig open together with the plastic film), to a depth of 6-7 cm, and plant. When transplanting, sort the seedlings into grades by size and plant them separately, planting 2 plants per pit to allow for selecting and keeping seedlings; finish planting within 3-4 days. For transplanting, it is best to plant on a windless sunny morning, which makes survival easier. When transplanting, the root system of the cotyledon seedlings is required to spread out, stand upright or semi-upright (slanted), and the roots must not curl, so as not to affect root system and seedling growth. When earthing up, it is best not to expose white roots; after earthing up, gently press the soil with your hand so that the root system and soil are in close contact, then water thoroughly immediately. After the water seeps down, cover with 1 cm of fine soil to close the pit, preventing a hard crust from forming. Then cover with plastic film and press the film down tightly with soil to prevent it from being blown dry by wind. After planting is completed, let the cotyledons and hypocotyl be 1.0-1.5 cm above the ground, and at the same time press the soil between each seedling pit to prevent the wind from moving the film and injuring the seedlings. When transplanting, stagger the plant spacing to lay the foundation for pruning and removing side branches.
5. Field management
1. Pruning: Three-vine pruning, keeping one vigorous main vine growing from the root and two vigorous side vines growing from the root, and promptly pinching off the other side vines. Pruning is best done from about 11 a.m. to before 4 p.m., and preferably not on cloudy or rainy days, to avoid injuring the vines and causing wound infection and bleeding. If a vine is not straight, be sure to straighten it by hand and press it firmly.
2. Vine pressing: Generally press three times. Press the first time when the main vine is 30-40 cm; after that press once every 40 cm (side vines the same as the main vine). When pressing vines, use relatively heavy soil or clods, with the pressed soil weighing about 2 jin. Spray a fungicide on the leaves once 1-2 days before pruning to prevent wound infection by pathogens during pruning. Hidden pressing: dig a furrow in the ground below the melon vine with a depth of 5-10 cm and a length of 10-20 cm, bury the melon vine firmly with soil, leaving the leaves exposed. Depending on weather conditions, it is generally more suitable in dry years, and melon vines showing excessive growth can also be hidden-pressed. The hidden pressing method is not suitable in continuous rainy and humid weather and years.
3. Artificial pollination: When female flowers open, if there is fog or cloudy and rainy weather, go to the field on the afternoon of the day before the female flowers open and put rainproof paper caps on the female flowers. On the morning of the next day at 5 o'clock, go to the field and pick the male flowers that are about to open, bring them back, and place them indoors at a suitable temperature for later use. When the female flowers open between 6 and 9 o'clock, go to the field, turn the petals of the male flowers back to expose the pollen, and gently smear it on the stigma of the female flowers. After pollination, put the rainproof paper caps on the female flowers again (the central purpose is to prevent the stigma and pollen of the female flowers from getting rained on). This improves the fruit-setting rate.
4. Fruit retention: Keep one melon per plant. Generally choose to keep a melon on the main vine at the 3rd-4th female flower, and on a side vine choose the 3rd female flower to keep the melon. Once the young melon has set firmly, promptly select and keep the melon. To prevent excessive growth and failure to set fruit, the melon-dropping method may be used, that is, when the second melon has grown for 3-4 days (set firmly), remove the first melon, and so on, until reaching the ideal node position and standard melon shape.
When the young melon grows to the size of a goose egg, select and keep the melon. Choose one with a thick, long stem, light green rind color, no scars, and a well-formed shape. Keep it as the selected melon, and remove the others.
The above is within the normal range; in special environments, the fruit retention method should be adjusted flexibly.
For watermelons sown and grown in spring in the north, regardless of the pruning method, the melon at the first female flower on the main vine must be removed promptly.
5. Topdressing and watering
1) Watering for vine extension and topdressing for vine extension: When the melon seedlings have grown 5-6 true leaves and are about to extend their vines, water once and topdress once according to soil moisture and seedling condition.
If the water source is sufficient, fast-flood irrigate heavily in the furrow between 2 melon ridges, and water thoroughly. Before irrigation, topdress first: per mu, topdress 10 kg of urea and 10 kg of potassium sulfate. Apply 20 cm away from the side of the roots, 15 cm deep, by punching holes and applying.
2) Topdressing for melon swelling and watering for melon swelling: 7-12 days after pollination of the female flower at the fruit-setting node (when the young melon grows to the size of a goose egg), it is necessary to topdress for melon swelling and water for melon swelling. Per mu, topdress 10 kg of urea and 10 kg of potassium sulfate. On rainy days apply granular fertilizer; on dry days apply water-soluble fertilizer (add urea and potassium sulfate to water, and after dissolving, punch holes 20 cm away from the side of the melon roots, 15 cm deep; each plant must receive no less than 4 jin of water). If the soil is relatively wet, water less or not at all; this should be flexibly controlled according to actual conditions.
6. Pest and disease control:
1) Control of damping-off and seedling blight at the seedling stage
When planting and watering, add 70% thiophanate-methyl, 70% formazin, and 70% dexon wettable powder to the water, mix to make a 500-800 times medicinal solution, and pour it into the pits. (Add a total of 1 jin of the above three medicines to 500 jin of water.)
2) Control of fusarium wilt: When central diseased plants are found in the field (only 1-2 plants diseased), use 1500 times solution of Jundushaxing plus 500 times solution of Withering Spirit, plus potassium dihydrogen phosphate, to irrigate the roots, applying 150-200 ml (3-4 liang) of medicinal solution per plant. At the same time, irrigate the roots of nearby uninfected plants around them. Before root irrigation, open the soil around the melon roots by hand until white roots are visible, then carry out root irrigation. After root irrigation, expose to the sun for one day, irrigate once every 5-7 days, and generally 3-4 times can bring it under control.
3) Control of anthracnose: After anthracnose is found in the field, use 3000 times Jundushaxing plus 500 times anthracnose formazin, add 0.5 jin of potassium dihydrogen phosphate per 30 jin of water (30 jin of water in a sprayer), and spray on the leaves. It is best if there is no rain for 6-8 hours after spraying; if it rains within 6 hours after spraying, respray immediately. Generally spray once every 5-7 days, and 3-4 times can bring it under control. Or mix 25 g of 50% thiophanate-methyl + 25 g of 50% ridomil + 20 g of Kocide into a 300 times solution and spray, once every 5-7 days, and 2-3 times can bring it under control.
4) Control of aphids: When ants are found on watermelon vines in the field, attention should be paid to checking whether there are aphids. When there are a small number of aphids, immediately spray 800 times solution of 40% omethoate, 800 times solution of Yibianqing, or 800-1000 times solution of Yisaojing for control, spraying once every 5-7 days, with control throughout the whole growth period. In recent years, Liriomyza sativae has also been found, and it must be controlled promptly.