The Latest Tutorial on Efficient Cultivation Techniques for Seedless Watermelon
The growth of seedless watermelon is largely the same as that of ordinary watermelon, so its cultivation techniques are close to those for ordinary watermelon. However, seedless watermelon also has many unique characteristics, such as low seed germination rate, low seedling survival rate, slow early growth, vigorous growth in the middle and late stages, pollen abortion, and low natural fruit-setting rate. Therefore, corresponding technical measures must be taken in cultivation management to achieve high yield and high efficiency.
Melon Field Preparation
Although seedless watermelon is not strict about soil requirements, from the perspective of high yield and high quality, it is still necessary to artificially create a better suitable environmental condition for its high yield. Because seedless watermelon is afraid of continuous cropping, afraid of waterlogging, afraid of drought, and has a well-developed root system, when selecting a melon field, choose a plot with high and dry terrain, sufficient sunlight, deep soil layer, good permeability, and convenient drainage and irrigation, so as to ensure the normal growth and development of seedless watermelon. After the soil thaws in early spring, harrow the melon field finely and level it, dig melon furrows according to the planned row spacing, with each furrow 30 cm deep and 30 cm wide. Irrigate enough bottom moisture water, apply 4000--5000 kg of high-quality decomposed farmyard manure per mu in the furrows, 50 kg of nitrogen-phosphorus-potassium ternary compound fertilizer, or 50--60 kg of watermelon special fertilizer, and spray phoxim for disinfection, then close the ridges to make beds and cover with film. This work should be carried out 5--7 days before planting.
Sowing and Seedling Raising
Seedless watermelon seeds have higher temperature requirements for germination and emergence than seeded watermelon. Growth is slow before the two-leaf stage, and the seedlings have weak cold resistance, so at present, seedling transplanting is generally used for production, and direct seeding cultivation is also carried out in a few places.
1. Seedbed preparation: Build a seedbed in a greenhouse or small arch shed. The seedbed is generally 1.2 m wide, 15-20 cm deep, and 8-12 m long. On the north side of the small arch shed seedbed, make a windbreak with sorghum or corn stalks. Nutrient soil is generally prepared in a ratio of four parts field soil to one part decomposed barnyard manure, add an appropriate amount of thiophanate-methyl and trichlorfon for disinfection, mix thoroughly, sieve, put into nutrient pots, and cover with film to increase temperature.
2. Seed soaking and germination: First pour boiling water and cold water into a clean basin at a ratio of 2:1, adjust the temperature to about 55-60 C, put the seeds in and stir quickly until the temperature drops below 40 C, stop stirring, and continue soaking the seeds for 1-1.5 hours. Remove and rub repeatedly to remove the sticky substance on the seed surface. Because the embryo of seedless watermelon seeds is not fully developed and the seed coat is thick, germination is difficult, so before germination, shell cracking treatment should be taken to improve the germination rate. Generally, use teeth to gently crack open one third of the suture line at the hilum, or use a nail clipper to clip open the hilum, taking care not to damage the seed embryo. Also, do not crack the hilum too much, so as to avoid the seed coat falling off during germination. Wrap the cracked seeds in a wrung-out wet cloth and place them in a constant-temperature box at 33-35 degrees for germination. After 20--24 hours, pick out the germinated seeds, and continue germinating the remaining seeds. In rural areas, heated kang, electric blankets, and stoves are generally used for germination, but temperature and humidity must be well controlled to ensure smooth seed germination. During germination, special attention should be paid to:
① Maintain appropriate humidity; do not add water or rinse at will, to prevent excessive moisture in the germination bed and seeds, which can cause seed or sprout rot, and do not let the seedbed humidity become too low, to prevent the seeds from drying out.
② Maintain a relatively constant temperature and prevent drastic temperature changes. A sharp drop in temperature or excessively high temperature will cause germinating seeds to lose their germination ability.
③ Keep the seeds ventilated and breathable; do not germinate them in tightly closed, airtight containers or plastic film.
3. Sowing: In North China, it is suitable to sow at the end of March and the beginning of April, and water thoroughly the day before sowing. Sowing should be carried out under clear and windless conditions. For dibbling, use a small wooden stick to make a small hole in the center of each nutrient pot, then place the seed flat in the seedling soil, with the small sprout downward and close to the hole wall. Sow one seed per nutrient pot, and cover promptly with sieved fine soil, with a thickness not exceeding 1 cm. Start sowing from one side of the seedbed, covering with film while sowing.
4. Seedbed management: The seedling stage of seedless watermelon is generally about 30 days. According to the rules of germination and seedling growth, seedbed management can be divided into three stages: The first stage, from sowing to cotyledon emergence and slight unfolding, with the focus of management on increasing temperature and “removing the cap.” Keep the daytime temperature at 30-35 C, appropriately cover with straw curtains at night to prevent cold, and keep the nighttime soil temperature at 18-20 C. Seedless watermelon emerging with the shell is a common phenomenon during seedling raising. Every morning, while the seed coat is moist and soft, use both hands or tweezers to gently remove the seed coat, taking care not to injure the cotyledons and young stem. The second stage, from slight cotyledon unfolding to the appearance of the first true leaf, with the focus of management on controlling water and lowering temperature, preventing high-temperature spindly growth that forms tall-legged seedlings. During this period, the daytime temperature should be controlled at about 25 C, and nighttime at 15-20 C. If the temperature is too high, open the film opening for ventilation and cooling. The ventilation position is generally on the leeward side, and ventilation is generally from about ten in the morning to about four in the afternoon. The third stage, from seedling heart breaking to 2-3 true leaves, with the focus of management on temperature and humidity. Appropriately raise the seedbed temperature to 25-30 C, appropriately extend ventilation time, and remove the film to harden the seedlings 3-5 days before transplanting, enhancing seedling stress resistance. Strictly control humidity during the seedling stage. As long as the seedbed has sufficient bottom water, try not to water. If water shortage occurs, sprinkle with a watering can on a sunny morning to maintain a certain humidity. Water thoroughly once on the afternoon of the day before transplanting to prevent the soil clod from breaking apart and damaging roots during transplanting. In addition, promptly remove weeds and spray chemicals to prevent damping-off disease and various pests.
5. Arranging pollinator varieties: The male flowers of seedless watermelon have poorly developed pollen and almost no vitality, and cannot stimulate the development of the female flower ovary. Only with the stimulation of pollen from ordinary watermelon can seedless watermelon grow. For pollinator varieties, it is advisable to choose excellent local main seeded watermelon varieties. The fruit skin color should differ from that of the seedless watermelon for easy identification. The ratio to seedless watermelon is generally 9-10 to 1. In order to make the flowering periods of the pollinator varieties and seedless watermelon meet, the pollinator varieties should be sown 3--5 days later.
Seedless watermelon seedling technology is the key technology in seedless watermelon production. Only by accurately mastering the key links in the seedling process can uniform and strong seedlings be ensured, laying a good foundation for high yield and increased income.
Field Planting
Planting time: transplanting and field planting of seedless watermelon is suitable after the last frost, when the average daily temperature is stable above 15 C. In North China, it is generally from the end of April to the beginning of May. The seedling age of 2-3 leaves and 1 heart is better. Planting should choose clear and windless weather, and pay attention to listening to the weather forecast to prevent windy and cooling weather. Planting density: in northern regions, generally plant 650-750 plants per mu, with a plant spacing of about 70 cm and a row spacing of 1.4-1.6 m. Planting method: first punch holes in the center of the high ridge according to the planned plant spacing, and if necessary, spray chemicals to control soil pests or apply a small amount of hole fertilizer. Plant the seedlings into the holes, with the depth slightly lower than the ground surface, cover with soil so that the nutrient pot is closely combined with the soil, water to stabilize the seedlings, and after the water seeps down, seal the film holes tightly with fine soil.
Field Management
Seedless watermelon grows slowly in the seedling stage, so it should be managed early to promote early development. After vine extension, control fertilizer and water to prevent excessive growth, create conditions for fruit setting, and choose better node positions for artificial pollination.
1. Fertilizer and water management: For water management, seedless watermelon should be watered at least 2--3 times throughout the growth period. After the watermelon vines extend, the leaves increase, sunshine duration is long, and water demand increases, so a “vine-extension water” must be applied. When the young melon grows to the size of a fist, water well for melon expansion to ensure watermelon yield, quality, and normal growth and development. Afterward, whether to water can be decided according to the climate and soil moisture at that time, and watering should stop one week before harvest. Topdressing: Watermelon is a fertilizer-loving crop, and rational fertilization is one of the important measures to ensure high-quality and high-yield watermelon. The general principle is: apply seedling-promoting fertilizer cautiously, apply vine-extension fertilizer skillfully, and apply melon-expansion fertilizer heavily. Topdressing is mainly quick-acting fertilizer. Under the condition of sufficient base fertilizer, non-sandy soil generally does not apply seedling-promoting fertilizer. Under normal circumstances, mainly two topdressings are carried out. Vine-extension fertilizer should be mainly nitrogen fertilizer, supplemented by potassium quick-acting fertilizer, to promote the vegetative growth of watermelon, so as to ensure the formation of a well-developed root system and sufficient leaf area required for high yield. Generally, apply 8 kg of urea and 5 kg of potassium sulfate per mu. The second time is before the fruit expansion period, apply quick-acting chemical fertilizer. Topdressing should be mainly potassium and nitrogen fertilizer, which is beneficial to the formation of fruit yield and the improvement of quality. Generally, apply 20-25 kg of urea and 10--15 kg of potassium sulfate per mu. Water and fertilizer management should be reasonably controlled according to local soil and climate conditions and vine growth, achieving a combination of topdressing and control, and a combination of irrigation and drainage.
2. Pruning and vine pressing: Seedless watermelon generally adopts two-vine or three-vine pruning. Two-vine pruning means retaining the main vine and selecting one robust side vine at the base of the main vine, with all other side vines removed. In this way, the stems and vines are reasonably distributed, the leaves are ventilated and receive light, photosynthesis and disease resistance are enhanced, thereby increasing yield and improving quality. Vine pressing can fix the melon vines, prevent them from being overturned by strong winds, and control vine growth. When the main vine of the melon plant grows to about 30 cm, push the vine over from an upright position to force it to grow in the specified direction. Vine pressing generally has two methods: open pressing and hidden pressing. Open pressing refers to fixing the melon vine on the ground with soil blocks or branches; hidden pressing is loosening and flattening the soil with a shovel and burying and pressing the melon vine underground. Generally, press the main vine the first time at 40-50 cm, then press once every 4--6 nodes thereafter, requiring 2--3 pressings.
3. Artificial supplementary pollination: To ensure fruit set on female flowers at suitable nodes, artificial pollination must be carried out. Keeping fruit on the third female flower of the main vine or the second female flower of the side vine gives the best quality and the highest yield. Pollination is carried out from 7--10 a.m. every day. When watermelon flowers open in the morning, first collect newly opened male flowers from the pollinator varieties, fold the petals backward to expose the stamens, then lightly smear once around the stigma of the female flower of the seedless watermelon opened that day, so that pollination is uniform.
4. Fruit setting and fruit retention: When the young fruit grows to the size of a steamed bun, the fruit begins to expand rapidly. At this time, fruit drop generally no longer occurs, so promptly select fruit with good node position and correct fruit shape. For two-vine or three-vine pruning, retain one fruit per plant.
5. Pest and disease control: Pest and disease control is a regular task in field management and an important link for high yield, so it is necessary to prevent and treat early. The main diseases of seedless watermelon include gummy stem blight, anthracnose, leaf blight, etc. Promptly spray 75% chlorothalonil 600 times solution, or 70% thiophanate-methyl 500 times solution, or 70% mancozeb 600 times solution, and use them alternately. Stop spraying 7-10 days before harvest.
6. Covering melons: In the late growth stage of seedless watermelon, the plants gradually decline, and the leaves cannot effectively shade sunlight, so promptly cover the melons with newspaper to prevent them from being damaged by the sun.
Timely Harvest
Seedless watermelon takes about 35-40 days from flowering to fruit maturity. Moderately mature fruit has good flesh color, is juicy, sweet, and refreshing, and should be picked in time.