Hydroponic vegetables refer to vegetables that are cultivated under the traditional soil cultivation form, in which most of the roots grow in the nutrient liquid layer and only provide water, nutrient and oxygen through the nutrient liquid. Hydroponic leaf vegetables have the characteristics of short growth cycle, clean product, good taste and good benefit. The varieties of hydroponic vegetables are mainly leaf vegetables, such as lettuce, green vegetables, cabbage, water cabbage, amaranth, chicory and so on. Preparation of nutrient solution is the key technology for normal growth of hydroponic vegetables.
At present, the nutrient solution formula used in the production of leafy vegetables is 1122g calcium nitrate, 910g potassium nitrate, 272g potassium dihydrogen phosphate, 40g ammonium nitrate, 247g magnesium sulfate, 1.2g boron sulfate, 0.09g zinc sulfate, 4.2g iron chelate, 27.8g ferrous sulfate and 37.3g disodium ethylenediamine tetraacetic acid per 1t nutrient solution. Leaf vegetables are grown on substrate. Vegetable seedlings grow to the colonization stage, seedlings from the soil or soilless cultivation matrix, can be directly planted in the pipeline equipped with funnel filter, or through root treatment and then planted in the pipeline water, the specific treatment method:
1. Wash soil or other cultivated substrate with clean water to remove roots;
2. Cut off old or dead roots, dead skin and excess lateral roots;

3. Soak roots with hydroponic plant disinfectant for 15-20 minutes to sterilize and disinfect. 4. Rinse with water again several times before colonizing.

The production management

1.Temperature control Hydroponics leaf vegetable root growth environment is nutrient solution, the temperature of nutrient solution directly affects the speed of leaf vegetable growth, the appropriate nutrient solution water temperature is 15-18 ℃, the temperature is 18-23 ℃. In summer, with high temperature and strong light, leafy vegetables grow fast, have low nutrient content and poor quality. Moreover, the stems and leaves of leafy vegetables contain more moisture and are crisp and tender. Strong light or water vapor condensation droplets are easy to burn the leaves, causing spots on the leaves and reducing the commercialization. Therefore, in the production, fan wet curtain cooling system and shading net are used to achieve the purpose of ventilation and cooling, control the growth of leafy vegetables and ensure the quality. However, it should be noted that the indoor light time and intensity must meet the requirements of the growth of leafy vegetables. In the morning and evening, the shade net should be pulled up to increase the weak light time to increase the color depth and thickness of the leaves. In winter, the temperature of the nutrient solution is preheated to reach the temperature required for the growth of leafy vegetables.

2.Concentration regulation winter temperature is low, the growth of leafy vegetables is slow, in order to improve the growth rate, the concentration of nutrient solution can be appropriately high, but not too much nitrogen, so as not to cause the taste of leafy vegetables, reduce the quality. Leafy vegetables grow faster in summer, and nutrient solution concentration is slightly lower than that in winter. The growth rate of leafy vegetables can be controlled by increasing the number of cycles to improve their quality.

3.Timely liquid supply The time and times of nutrient solution supply mainly depend on the cultivation form, vegetable growth state and environmental conditions. In the cultivation process should be timely liquid supply to ensure adequate nutrient supply. The time of liquid supply is generally chosen in the daytime, and no or little liquid supply at night. The number of liquid supply in sunny days is more, and the number of liquid supply in rainy days is less. More when the temperature is high and the light is strong, less vice versa. Under normal circumstances, 2-4 times a day, each time hold in 30 minutes.

4. Replacement of nutrient solution The nutrient solution should be replaced timely after a period of use. Because nutrient solution in the process of use will gradually accumulate too much material hindering plant growth, nutrient imbalance, a large number of bacteria, resulting in root growth arrest, and even lead to plant death. To grow the vegetable with shorter cycle commonly, each crop changes nutrient fluid. At the same time, NFT Gutters and plastic pipes should be cleaned and disinfected once a year.