The optimum growth temperature of lettuce is between 65438 05℃ and 25℃. When the temperature is lower than 15℃, the growth is slow, and when it is higher than 30℃, the growth is poor, and it is easy to bolting and flowering. Hydroponics is the best in winter and spring, and hydroponic lettuce is suitable for choosing loose leaf lettuce varieties.

Nutrient fertilizer

The formula of lettuce nutrient solution is that calcium nitrate 600g, potassium nitrate 600g, magnesium sulfate 350g and ammonium dihydrogen phosphate 150g are added to each ton of water, and the micro-fertilizer is in the general formula. When breeding in production, a breeding pond or pond can be used; When cultivating at home, use pots, bowls, boxes, etc. Make sure there is no water leakage.

Hydroponics

Seedling raising: vermiculite is used as seedling raising substrate in the seedling raising tray. Before sowing, the vermiculite is soaked in water, the seeds are evenly spread on the vermiculite, and then covered with a layer of vermiculite twice as large as the seeds, and the seedlings can emerge in 5-7 days at 20℃. After emergence, the EC value of water and nutrient solution (conductivity, the main index of water quality standard) is 1.6 ~ 1.8.

Planting: take the foam board, drill a hole every 20 cm, with a diameter of 2.5 cm, and tighten the lid of the hydroponic container. Put nutrient solution into the container, and the EC value is 1.6 ~ 1.8. When lettuce seedlings grow to two real leaves, plant them separately. Firstly, the vermiculite at the root of the seedling was washed, and the stem base was wrapped with sponge strips, and then the seedling was stuffed into the holes of the foam board. Keeping the stem base dry and breathable can greatly reduce the occurrence of rhizome base diseases.

Harvest: The management process of hydroponic lettuce is very simple. After planting, in order to keep the level of nutrient solution stable and consistent, nutrient solution can be added every 2 ~ 3 days, with water temperature of 20℃ ~ 22℃ and pH value of 6 ~ 6.5. When the seedling has 3 ~ 4 true leaves, the EC value is adjusted to 1.8 ~ 2, and nutrient solution is added according to the situation, and commercial vegetables can grow in about 20 ~ 25 days.

If cultivated at home, you can pick leaves and eat them to keep them fresh. Production is generally a one-time harvest. In order to visually express the characteristics of hydroponic vegetables, it is best to bring some white roots. In order to reduce the nitrate content in lettuce, you don't need to supplement nutrition one week before harvest, just add water.

Preparation before seedling raising

① Prepare the nursery tray. The seedling tray is made of flat-bottomed impermeable plastic tray, which is 60 cm long, 24 cm wide and 4 cm high.

(2) Prepare the nursery substrate-sponge block. Lettuce seedlings are also cultured in water, and its seedling substrate is loose sponge with a thickness of 3 cm. First, the sponge is cut into blocks slightly smaller than the size of the seedling tray, and then cut into small pieces of 3 square centimeters, which are slightly connected with each other to facilitate settlement in the seedling tray. Wash the sponge with clear water and lay it flat on the seedling tray for later use.

③ Seed treatment. In order to make lettuce seeds germinate evenly, low temperature treatment must be carried out, especially in high temperature season. The specific method is: soak the raw rapeseed in cold water for 30 minutes, control the excess water, wrap it with gauze, put it in a sealed plastic bag, then store it in the refrigerator (the temperature is about 1~2℃) for 2 days, and then take it out for sowing.