Conventional Seedling Raising Technique for Watermelon under Small Arch Shelter with Double Film
Watermelon cultivation under small arch shelter with double film means covering with a small arch shelter on top of plastic film mulching, so that both the aboveground and underground parts of the watermelon are kept under suitable environmental conditions. The crop can be marketed in early June, maturing 30-40 days earlier than open-field cultivation and 15-20 days earlier than with plastic film mulching alone. Moreover, after the first crop of melons is harvested, a second crop can continue to be produced, greatly increasing the yield, generally 3500-4000 kg per unit area. Because of the early marketing and high yield, the output value is 1.5-3 times that of open-field and plastic-film-mulched watermelon cultivation, and the economic returns are good as well.
1. Selection of suitable improved varieties. In order to obtain high economic returns, watermelon cultivation under small arch shelter with double film should use early-maturing, high-yielding, disease-resistant varieties with good quality and tolerance to low temperature and weak light. At present, the main varieties grown in production include: Jingxin No. 1, Te Da Jingxin, Xinong No. 8, Chuangfeng No. 8, Zhengza Wu Hao, Meikang No. 8, Guifei, Zaoshu Taizi and other improved varieties.
2. Conventional seedling raising. Watermelon cultivation under small arch shelter with double film can be direct-seeded or transplanted as seedlings; transplanting seedlings can advance maturity and save seeds. Seedling raising methods include conventional seedling raising and grafted seedling raising.
1. Seedling raising site and facilities. For watermelon cultivation under small arch shelter with double film, transplanting is relatively early (25-30 days earlier than open field). Protected facilities such as solar greenhouses, large plastic tunnels and small warm pits can be used, with electric heating beds for seedling raising; each 10 sq m of seedling bed requires 1 electric heating wire. Generally, about 6 sq m of seedling bed is needed per mu of watermelon, or about 8 sq m if grafted seedlings are used. Plastic nutrition pots (8-10 cm in diameter, 10 cm high), plug trays (50 cells) or nutritional soil blocks can be used for seedling raising.
2. Preparation of nutritional soil and disinfected soil. For the nutritional soil formula, use disease-free, loose garden soil that has not grown cucurbit crops in recent years; sieve the garden soil, barnyard manure and decomposed chicken manure, and mix them in a ratio of 6:2:2. Add 1 kg of diammonium phosphate or superphosphate, 1 kg of potassium sulfate and 100 g of 50% carbendazim per cubic meter, and mix evenly for later use. Soil disinfection treatment can also be carried out by spraying the nutritional soil with a 100-fold solution of 40% formalin (1 kg of 40% formalin can disinfect 4000-5000 kg of nutritional soil), stirring while spraying, then covering with plastic film and heaping for 2-3 days; after removing the film, let it air for 7-10 days before filling pots. The amount of water added to the nutritional soil should be such that it forms a ball when squeezed by hand and breaks apart when dropped to the ground. When filling pots with nutritional soil, make the top loose and the bottom firm to help the seeds emerge.
To prevent seedling-stage diseases, also prepare disinfected soil for the seedling bed. Mix equal amounts of 50% carbendazim powder and 50% thiram wettable powder, then evenly blend with nutritional soil at a ratio of 1:300-400. At sowing, apply 1/3 as basal application and 2/3 as covering application.
3. Seedling bed preparation. Dig a bed to make the seedling bed; after leveling, lay the heating wire at a power of 80-90 W/sq m with a spacing of 10 cm (the spacing of the two outer wires is best at 8 cm). Add a 1 cm thick layer of fine soil over the heating wire, then spread a 1 cm thick layer of sieved stove ash, or directly place nutrition pots filled with nutritional soil, seedling (plug) trays or nutritional soil blocks on the heating wire. Cover the shelter 5-7 days before sowing to warm the soil and raise the temperature. Water thoroughly 1-2 days before sowing; after the water has completely infiltrated, cover with plastic film and turn on the heating wire to increase temperature.
4. Seed treatment
(1) Seed selection: Select seeds before sowing, remove moldy, insect-damaged, broken, deformed and relatively shriveled seeds, and choose plump seeds. Sun the seeds for 1-2 days on a sunny day, which can increase the germination rate and make the seedlings emerge uniformly.