How to grow watermelons in a greenhouse? Keep this complete cultivation guide
In the past, when material resources were extremely scarce, it was not easy to eat seasonal fruits and vegetables, and eating off-season fruits and vegetables was even harder than climbing to the sky. The development of the times has solved many of the problems we faced in the past one by one, and greenhouse fruit and vegetable technology also lets us eat whatever we want all year round.
Watermelon greenhouse cultivation techniques
1. Variety selection
There are many cultivated varieties of watermelon. Watermelon varieties suitable for early spring greenhouse cultivation are required to be both early-maturing and high-quality, and also have characteristics such as easy fruit set, disease resistance, high yield, and suitability for market demand. Based on summaries from recent years, the varieties suitable for greenhouse cultivation mainly include Jinmei Daguo, Zhizun, Lidu, and others.
2. Rootstock selection
Watermelon rootstock is required not only to have good, stable affinity with watermelon grafting, but also to have good disease resistance and no adverse effect on watermelon quality. According to observations in recent years, gourd rootstock performs poorly against acute watermelon wilt and can easily cause inestimable losses, while pumpkin rootstock performs relatively better. Therefore, at present, basically all watermelon rootstocks use pumpkin rootstock. Currently, the better rootstocks include Zhuangsi, Pumpkin No. 2, Pumpkin Changbai Daban, and others.
3. Seed treatment
Rootstock seeds and watermelon seeds are treated in the same way: soak the seeds in warm water at 25-30°C for 48 hours. After soaking, wash the seeds several times in clean water and rub them repeatedly to wash off harmful substances on the seed surface. Then wrap them well in fine cloth and place them in a constant-temperature chamber at 27-30°C for sprouting, or insert a thermometer and place them on a heated kang for sprouting. The sprouting length is best when the seeds have just turned white.
4. Sowing techniques
The sowing period for greenhouse watermelon is preferably around December 20 on the solar calendar. Place the sprouted rootstock seeds in the middle with the embryo bud facing down, then cover with floating soil (fine sandy loam) and cover with 1.5-2 cm of soil. Under normal circumstances, about 5 days after sowing the rootstock seeds, watermelon seeds can be sprouted. Watermelon seeds can be sprouted in a sand box.
5. Grafting techniques
① Grafting time: Grafting can be carried out after the cotyledons of the rootstock seeds have flattened out, which is also the best time for grafting.
② Grafting method: Use the top insertion method. During grafting, remove the growing point of the rootstock, use a bamboo skewer at the cut on the rootstock, insert obliquely downward at 45 degrees along the line connecting the cotyledons into the hypocotyl, to a depth of 0.5-1 cm, with the top of the bamboo skewer reaching the cortex on the other side of the hypocotyl. Then immediately take out the scion seedling, place it on the index finger, and cut it at 45° with a blade. After trimming the scion seedling, immediately pull out the bamboo skewer and insert the scion seedling in the direction of the bamboo skewer hole.
③ Grafting management: Keep the temperature at 25°C, and the low temperature at 24°C. For the first three days after grafting, keep it closed without ventilation or air exchange, so that the air humidity reaches saturation. One week before planting, lower the soil temperature to 15-13°C and the air temperature to 23°C during the day and 13°C at night, with the nighttime minimum not lower than 10°C, to harden the seedlings and bring the young seedlings close to the environmental temperature after planting.
Field management of watermelon
1. Cultivation and drainage
Cultivation begins after sowing and full emergence or after planting and recovery. Generally, thinning, loosening the soil, and hilling are carried out in combination. When the vines are 30 cm long, apply a heavy fertilizer once and then hill the soil. Watermelon fruits are large, yields are high, and water demand is great. Irrigation is needed in particularly dry seasons, but during the watermelon growing period in the Yangtze River Basin there is a lot of rain, so drainage work is especially important.
2. Pruning
Watermelon vines and leaves are luxuriant. If allowed to grow freely, the vines overlap each other, which not only affects dense planting but also delays fruit setting. Watermelon pruning methods generally include single-vine, double-vine, and three-vine types. In single-vine pruning, each plant keeps only one vine. All other side vines are removed. The method is simple, and with more plants per unit area, more fruits are set, but each plant has fewer leaves and a smaller assimilation area, so the fruits are not easy to grow large, and both yield and quality are relatively low. In double-vine or three-vine pruning, generally in addition to keeping the main vine, when the main vine grows to more than 30 cm, double-vine pruning selects one robust side vine at the base, while three-vine pruning keeps two robust side vines as secondary vines or reserve vines, and all other side vines are removed.
3. Vine pressing
When the vines are 30 cm long, the vines should be arranged so that they are evenly distributed, and soil blocks should be used to press the vines at the nodes to promote the production of adventitious roots, fix the leaves and vines, prevent mutual shading and being broken by wind, and avoid damaging roots and leaves. After that, press once every 5-6 nodes until the vines and leaves cover the entire bed surface. To prevent breaking the crisp and tender melon vines, pruning and vine pressing should both be carried out in the afternoon.
Watermelon fertilization methods
The general fertilization principle for watermelon is to apply heavy organic fertilizer, use nitrogen fertilizer in appropriate amounts, apply phosphorus fertilizer steadily, increase potassium fertilizer, and apply nitrogen, phosphorus, and potassium in combination. After applying the base fertilizer, topdressing begins. Before topdressing, we must clearly establish one principle: apply seedling fertilizer lightly, apply vine-extension fertilizer skillfully, and apply fruit-swelling fertilizer heavily. The specific topdressing method is: when watermelon grows to 2-4 true leaves, begin applying seedling fertilizer. At this time, 4-5 kg (per mu, the same below) of urea is needed, to speed up the growth of the young seedlings. The specific method is to open an arc-shaped furrow 15 cm away from the young seedlings and apply the fertilizer; or make holes 10 cm away from the young seedlings for hole application. After fertilizing, cover the soil and water.
After the vine-extension period, the final topdressing is at the fruit-swelling stage. Topdressing at the fruit-swelling stage is to promote fruit expansion and prevent premature aging. At the fruit-swelling stage, it should be applied in two rounds. The first time, when the young fruit grows to the size of an egg, 10-15 kg of urea and 10-20 kg of potassium sulfate are needed; the second time, when the fruit grows to the size of a bowl rim, if single-element fertilizers are applied in combination, 5-7 kg of urea, 3-4 kg of calcium superphosphate, and 4-5 kg of potassium sulfate are needed. If compound fertilizer is used, 2-3 kg of compound fertilizer with three 15s, plus 4-6 kg of urea and 3-4 kg of potassium sulfate. The specific method is to open a furrow 30-40 cm from the roots on one side of the plant and apply the fertilizer.
Integrated control methods for watermelon diseases, pests, and weeds
1. Centralized planting and partitioned crop rotation. The crop rotation cycle for watermelon is more than 5 years on dry land and 3 years on paddy fields. In order to strictly implement crop rotation, the watermelon cultivation area can only account for 10%-15% of farmland. Centralized planting and partitioned crop rotation are advocated to facilitate farmland irrigation and drainage and reduce disease spread through irrigation water.
2. Clean the fields and reduce sources of pests and diseases: remove weeds in the fields and near the melon fields to reduce pest and disease sources. During the growing period, if diseased plants or diseased leaves are found, pruning should be carried out promptly. Cut off melon vines and diseased leaves, take them out of the melon field, and burn them in a centralized manner.
3. Select disease-resistant varieties and seeds from healthy plants, or disinfect seeds to eliminate infection of diseases caused by seed-borne bacteria.
4. Apply decomposed farmyard manure: cattle, sheep, chicken, and other livestock and poultry manure, and soil-mixed compost, should be used after high-temperature fermentation, or piled after sun exposure, to reduce insect eggs and pathogens and eliminate disease caused by fertilizer-borne bacteria.
5. Cultivate disease-free healthy seedlings. Use disease-free culture soil, soil disinfection, and seedbed disease prevention measures to avoid disease occurrence caused by bacteria carried by seedlings.
From watermelon seeds growing into mature large watermelons, watermelon must go through many steps such as sowing, grafting, pruning, and vine pressing. Breeding, fertilizing, watering, and pest and disease control all require a great deal of thought from melon farmers. Growing watermelons is not easy, so cherish every bite!