The United States is the first country to use soilless cultivation in vegetable production. The existing soilless vegetable greenhouse has an area of nearly 200 hectares, and the main cultivated vegetable species are tomato, cucumber and lettuce (lettuce). The yield of soilless vegetables in the United States is very high. The national average yield is 135-150 t/ hectares of tomato ,135225 t/ hectares of cucumber and 30-45 t/ hectares of lettuce. The high yield technical measures used in soilless vegetable cultivation in the United States mainly include the following. The selection of fine varieties farmers attach great importance to the selection of good varieties suitable for soilless cultivation. In the United States, there were many vegetable varieties suitable for greenhouse cultivation, but many of the vegetable seeds used in soilless cultivation were purchased from the Netherlands. Commonly used varieties: tomato Dombito銆丷ianto銆丣umbo, cucumber Daleva銆丗arbiola, lettuce Ostinata銆丼alinas銆丟rand銆丷apid and so on. There are many soilless systems that choose the appropriate soilless culture system, and the appropriate soilless culture system and related facilities are adopted in the United States according to the variety of vegetables. Tomato and cucumber are mainly cultivated by substrate, and their containers are mainly plastic bags, so they are also called bag culture, equipped with a set of drip irrigation facilities. lettuce is mainly cultivated by nutrient liquid film, and seedlings are planted in white hard plastic pipes (about 8 cm in diameter), equipped with a nutrient liquid circulation system. the commonly used substrates are vermiculite, perlite, peat, rock wool, sand bark, wood chips, polypropylene foam, etc. Mixed substrates are often used, such as vermiculite (or perlite)1 with peat 1, or marl 4 with vermiculite and perlite 3 each. During recent years, rock wool cultivation has developed rapidly, and most of the Grodan rock wool used is imported from Denmark. Vermiculite and other substrates can be used continuously for two years, and rock wool can only be used for one year. Plastic bags developed by substrate cultivation, often flat, white on the surface and black on the opposite side, are generally 100 cm脳30 cm脳8 cm. in size According to different soilless cultivation systems, the short-age strong seedlings were cultivated by adopting the corresponding seedling raising methods, strictly controlling the environmental conditions of the seedling stage, and cultivating the short-age strong seedlings. The size of rock wool seedling is generally 2 cubic meters. Bag culture with vermiculite and other substrates, with plastic bowl (with large bottom hole) seedling, bowl with vermiculite and peat and other substrates. The lettuce cultivated in nutrient liquid membrane was raised with finger-shaped seedling raising tubules, and "fiber cotton" was placed in the tube as the seedling substrate. A hand-held seeder was used to carry out precision seeding in the finger-shaped seedling raising tube. The suitable temperature and environment conditions were strictly controlled at seedling stage. The general conditions were as follows: tomato 4-5 weeks, cucumber 3-4 weeks, lettuce 1520 d.China Hydroponics Soilless Cultivation suppliers website:http://www.greenhouse-china.com/hydroponics-soilless-cultivation/