CN104756841B - Reduce the soilless culture method of Caulis et Folium Lactucae Sativae blade nitrate - Google Patents

Abstract

The invention discloses a soilless cultivation method for reducing nitrate in lettuce leaves, and aims to overcome the problem of high nitrate content in lettuce in the prior art. The steps of the method are as follows: 1. Seed soaking and germination; 2. Seedling cultivation in an artificial climate box: 1) Put the plastic nutrition bowl that has been sown into the artificial climate box, the daytime temperature is 25-30°C, and the illuminance is 5-5°C. Level 6, night temperature is 15-20°C, illuminance level 0, relative humidity is 70-80%RH; 2) Lettuce, Chinese cabbage and cherry radish grow 3-4 true leaves, and the height of pea shoots is 5-6cm 3) In order to ensure that crops can be transplanted simultaneously, lettuce, Chinese cabbage, and cherry radish are raised in the same batch, while pea seedlings should be raised 15 ± 1d later; 3. Seedling transplantation; 4. Preparation before field planting; 5. Planting; 6. Setting the cultivation environment; 7. Adjusting the pH and conductivity of the nutrient solution in the aerosol cultivation box, that is, the EC value; 8. Harvesting the plants.

Description

Soilless cultivation method for reducing nitrate in lettuce leaves

technical field

The invention relates to a soilless cultivation method for vegetables, more precisely, the invention relates to a soilless cultivation method for reducing nitrate of lettuce leaves.

Background technique

Soilless cultivation is a planting technique that uses nutrient solution or solid substrate plus nutrient solution to cultivate crops without soil. Since the 1970s, my country has begun to apply this technology in production, and the development and application of this technology have achieved good results. As a kind of soilless cultivation, aerosol cultivation is a technology that uses a spray device to atomize the nutrient solution into small droplets and spray it directly to the root system of the plant to provide the water and nutrients needed for plant growth. It has high yield and great benefit. , saving water and fertilizer, and reducing pests and diseases are the trends of future agricultural development. However, since nitrate is usually used as a nitrogen source in cultivation, the nitrate content in vegetables is often high, and the nitrate ingested by the human body mainly comes from vegetables, so reducing the nitrate content in vegetables has become an urgent problem to be solved. Investigations and studies have shown that the nitrate content of fruit and vegetable vegetables is low, while the nitrate content of leafy vegetables, which are consumed by Chinese residents, is relatively high, which should arouse people's sufficient attention.

Intercropping is a planting method in which two or more crops are planted alternately in rows or in strips during the same growth period on the same field. In the intercropping system, different crops have different ability to compete for nutrients, time to absorb nutrients peak, maturity period, depth of rooting and root distribution, so they can use nutrients of different levels, regions and different forms to reduce inter-specific nutrient competition, thereby promoting Formation of nutrient utilization advantages in intercropping crops. Through the efforts of scientific researchers at home and abroad, some experiments have confirmed that intercropping can reduce the nitrate content in soil and vegetables, but the application of intercropping to aerosol cultivation of lettuce has not been reported.

Contents of the invention

The technical problem to be solved by the invention is to overcome the problem of high nitrate content in lettuce in the prior art, and provide a soilless cultivation method for reducing nitrate in lettuce leaves.

In order to solve the problems of the technologies described above, the present invention is achieved by adopting the following technical solutions: the steps of the soilless cultivation method for reducing lettuce leaf nitrate are as follows:

1) Seed soaking and germination, the steps are as follows:

(1) Soak the seeds in warm water at 55°C for 15 minutes, stir continuously, and then soak the seeds in clean water at 10-30°C for 0-24 hours to allow the seeds to fully absorb water;

(2) Wrap the seeds with clean wet gauze and germinate in an incubator at 28°C to 30°C for 1 to 2 days. When 80 to 90% of the seeds open and sprout, they are sown into plastic nutrition bowls, and 1 to 2 2 seeds;

(3) Seed soaking time varies from species to species. Lettuce and cabbage seeds are not soaked to germinate directly, cherry radish seeds are soaked for 6h-8h, and pea seeds are soaked for 20h-24h;

2) Cultivate seedlings in an artificial climate box, the steps are as follows:

(1) Put the plastic nutrient bowl that has been seeded into the artificial climate box to grow seedlings. During the day, the temperature is controlled at 25-30°C, the illuminance is 5-6, and the nighttime temperature is 15-20°C, the illuminance is 0, and the relative humidity is controlled. Controlled at 70-80% RH;

(2) Prepare to transplant seedlings when lettuce, Chinese cabbage and cherry radish grow 3 to 4 true leaves, and the pea shoots are 5 to 6 cm high;

(3) In order to ensure that the crops can be transplanted at the same time, lettuce, Chinese cabbage, and cherry radish are raised in the same batch, while pea seedlings should be raised 15 ± 1d later;

3) Transplanting seedlings;

4) Preparation before planting;

5) Colonization;

6) Set the cultivation environment;

7) Adjust the pH value and electrical conductivity of the nutrient solution in the aerosol cultivation box, that is, the EC value;

8) Plant harvesting.

The steps of transplanting seedlings described in the technical scheme are as follows:

1) Fully water the soil before transplanting the seedlings to reduce the damage to the roots when transplanting the seedlings;

2) Gently separate the soil and the root system to be transplanted, and then clean the root system to be transplanted, ensuring the integrity of the root system of the plant during the process;

3) This process is carried out in the evening, that is, from 17:00 to 19:00 or on cloudy days. At this time, the transpiration of plants is weakened, which improves the survival rate of transplanted seedlings.

The steps of preparation before planting described in the technical scheme are as follows:

1) Transfer 1/3 to 1/2 volume of leaf vegetable nutrient solution into the aerosol cultivation box, and the highest liquid level of the nutrient solution should not exceed the spray head in the aerosol cultivation box;

2) Set a cycle spray timer, spray 15 minutes every 15 minutes during the day, and spray 5 minutes every 60 minutes at night.

The large amount of elements in the leaf vegetable nutrient solution described in the technical scheme adopts the Japanese garden formula, and the trace element formula adopts Holland's general formula, and the unit is mg/L, as follows:

Japanese Garden Recipe

Holland's Universal Formula

The steps of colonization described in the technical scheme are as follows:

1) Use the plant fixer matched with the aerosol cultivation box to fix the root neck of the seedling to be transplanted, and then insert it into the planting hole on the aerosol cultivation box. The plant fixer matched with the aerosol cultivation box adopts ethylene- Made of vinyl acetate copolymer foam material;

2) Move lettuce and Chinese cabbage, cherry radish or pea sprouts into one aerosol cultivation box, intercropping at a ratio of 1:1, and simultaneously move all lettuce into another aerosol cultivation box, as a control group;

3) The plant fixer with a diameter of 6cm and a thickness of 1.5cm is suitable for the planting hole of the aerosol cultivation box with a diameter of 5.5-5.9cm.

The steps of setting the cultivation environment described in the technical scheme are as follows:

The aerosol cultivation box was placed in a greenhouse environment for cultivation, and the greenhouse environment was set at a daytime temperature of 25±2°C and a nighttime temperature of 15±2°C.

The steps for adjusting the pH value and electrical conductivity of the nutrient solution in the aerosol cultivation box, that is, the EC value, described in the technical solution are as follows:

1) Insert the probe of the portable acidity meter into the nutrient solution, and read the pH value and EC value of the nutrient solution directly after the reading is stable;

2) Measure the pH value of the nutrient solution in the aerosol cultivation box every day, and adjust the pH value by adding 1-2 mol/L sulfuric acid solution or 1-2 mol/L sodium hydroxide solution to control the pH value of the nutrient solution at 5.8-6.2 ;

3) Measure the EC value of the nutrient solution in the aerosol cultivation box every day, and adjust the EC value by adding water or nutrient solution, so that the EC value of the nutrient solution is controlled at 1900-2300 μS/cm.

The steps of plant harvesting described in the technical scheme are as follows:

1) It can be harvested after 30-50 days after the lettuce, cabbage and cherry radish are planted;

2) When the pea shoots are about 15cm high, cut the pea shoots from the base to eat. After 2 to 3 days, the base of the pea shoots will grow tender shoots, and the harvest and growth will be repeated.

Compared with prior art, the beneficial effects of the present invention are:

1. The soilless cultivation method for reducing lettuce leaf nitrate described in the present invention is simple to operate, and only needs to select suitable crops and main crops for reasonable intercropping on the basis of the original aerosol cultivation.

2. The soilless cultivation method for reducing lettuce leaf nitrate according to the present invention retains the advantages of high yield of aerosol cultivation, water saving and fertilizer saving, reduction of plant diseases and insect pests, and reasonable intercropping light energy and high nutrient utilization rate, high economic benefits, etc. advantage.

3. the weight per plant of the lettuce obtained by the soilless cultivation method of reducing lettuce leaf nitrate obtained by the present invention is obviously higher than that of lettuce alone, the root vigor is obviously enhanced, and the nitrogen utilization rate is also improved, and the nitrate of lettuce leaf content has decreased significantly. That is, the lettuce obtained by using the soilless cultivation method for reducing the nitrate of lettuce leaves according to the present invention has good environmental adaptability and resource utilization rate, and its yield and quality are effectively guaranteed, which can provide people with safe and secure soilless cultivation methods. Cultivated vegetables.

Description of drawings

Below in conjunction with accompanying drawing, the present invention will be further described:

Fig. 1 is the block flow diagram of the soilless cultivation method of reducing lettuce leaf nitrate according to the present invention;

detailed description

The present invention is described in detail below in conjunction with accompanying drawing:

Lettuce, also known as leaf lettuce, is very popular among consumers because of its high nutritional value. Aiming at lettuce, which is a common leafy vegetable, the present invention applies intercropping to aerosol cultivation, optimizes common vegetables such as cabbage, cherry radish, and pea sprouts for intercropping with lettuce according to the collected data, and proposes an effective and easy-to-operate The soilless cultivation method for reducing the nitrate of lettuce leaves provides guarantee for the safety of soilless cultivation of vegetables, and provides a certain theoretical basis for further research.

The steps of the soilless cultivation method for reducing lettuce leaf nitrate are as follows:

1. Seed soaking and germination

1) Soak the seeds in warm water at 55°C for 15 minutes, stir continuously, and then soak the seeds in clean water at 10-30°C for 0-24 hours to allow the seeds to fully absorb water;

2) Wrap the seeds with clean wet gauze and germinate them in an incubator at 28-30°C for 1-2 days (days). When 80-90% of the seeds open and show buds, sow them into plastic nutrition bowls, and sow 1 ~2 seeds.

3) The specific soaking time varies from species to species. For example, lettuce and cabbage seeds can be directly germinated without soaking. Cherry radish seeds are generally soaked for 6-8 hours, and pea seeds are generally soaked for 20-24 hours.

2. Seedling cultivation in artificial climate chamber

1) Put the plastic nutrient bowl that has been seeded into the artificial climate box to grow seedlings. During the day, the temperature is controlled at 25-30°C, the illuminance is 5-6, and at night, the temperature is controlled at 15-20°C, the illuminance is 0, and the relative humidity is Has been controlled at 70 ~ 80% RH.

2) Prepare to transplant seedlings when lettuce, cabbage and cherry radish grow 3 to 4 true leaves, and pea seedlings are 5 to 6 cm high.

3) In order to ensure that the crops can be transplanted at the same time, lettuce, Chinese cabbage, and cherry radish should be raised in the same batch, while pea seedlings should be raised 15±1d later.

3. Transplanting seedlings

1) Fully water the soil before transplanting seedlings to reduce damage to roots during transplanting.

2) Gently separate the soil and the root system to be transplanted, and then clean the root system to be transplanted, ensuring the integrity of the root system of the plant during the process.

3) This process is best carried out in the evening, that is, 17:00-19:00 or on cloudy days, because the transpiration of plants is weakened at this time, which improves the survival rate of transplanted seedlings.

4. Preparation before planting

1) Transfer 1/3 to 1/2 volume of leaf vegetable nutrient solution into the aerosol cultivation box, and the highest liquid level of the nutrient solution should not exceed the spray head in the aerosol cultivation box.

2) Set a cycle spray timer, spray 15 minutes every 15 minutes during the day, and spray 5 minutes every 60 minutes at night.

5. Colonization

1) Use the plant fixer matched with the aerosol cultivation box to fix the root neck of the seedling to be transplanted, and then insert it into the planting hole on the aerosol cultivation box. The plant fixer matched with the aerosol cultivation box adopts ethylene- Made of vinyl acetate copolymer foam.

2) Transfer lettuce and Chinese cabbage, cherry radish or pea sprouts to one aerosol cultivation box for intercropping at a ratio of 1:1, and at the same time transfer all lettuce to another aerosol cultivation box as a control group to complete colonization.

3) Generally, a plant fixer with a diameter of 6cm and a thickness of 1.5cm is suitable for the planting hole of the aerosol cultivation box with a diameter of 5.5-5.9cm.

6. Set the cultivation environment

The aerosol cultivation box was placed under the environment conditions of the greenhouse for cultivation. The greenhouse environment was set at a daytime temperature of 25±2°C and a nighttime temperature of 15±2°C.

7. Adjust the pH value and electrical conductivity (EC) value of the nutrient solution in the aerosol cultivation box

1) Insert the probe of the portable acidity meter into the nutrient solution, and read the pH value and EC value of the nutrient solution directly after the reading is stable.

2) Measure the pH value of the nutrient solution in the aerosol cultivation box every day, and adjust the pH value by adding 1-2 mol/L sulfuric acid solution or 1-2 mol/L sodium hydroxide solution to control the pH value of the nutrient solution at 5.8-6.2 ;

3) Measure the EC value of the nutrient solution in the aerosol cultivation box every day, and adjust the EC value by adding water or nutrient solution, so that the EC value of the nutrient solution is controlled at 1900-2300 μS/cm.

8. Plant Harvesting

1) It can be harvested after 30-50 days after the lettuce, cabbage and cherry radish are planted;

2) When the pea shoots are about 15cm high, cut the pea shoots from the base to eat. After 2 to 3 days, the base of the pea shoots will grow tender shoots, and the harvest and growth will be repeated.

Example 1

The steps of the soilless cultivation method for reducing lettuce leaf nitrate are as follows:

1. Seed soaking and germination

1) Soak lettuce seeds in warm water at 55°C for 15 minutes, stirring constantly;

2) Wrap the seeds with clean wet gauze and germinate them in an incubator at 28°C for about 1 day. When 80-90% of the seeds open and sprout, sow them in plastic nutrition bowls, and sow 1-2 seeds in each bowl.

3) The operation of cherry radish seeds is the same as that of lettuce seeds, the difference is that the cherry radish seeds need to be soaked in water at 10-30°C for 6-8 hours to allow the seeds to fully absorb water.

2. Seedling cultivation in artificial climate chamber

1) Put the plastic nutrient bowl in which the seeds have been sown into an artificial climate box to grow seedlings. During the day, the temperature is controlled at 26°C and the light level is 5, at night the temperature is controlled at 16°C and the light level is 0, and the relative humidity is kept at 80% RH.

2) Prepare to transplant seedlings when the lettuce and cherry radish grow 3 to 4 true leaves.

3. Transplanting seedlings

1) Fully water the soil before transplanting seedlings to reduce damage to roots during transplanting.

2) Gently separate the soil and the root system to be transplanted, and then clean the root system to be transplanted, ensuring the integrity of the root system of the plant during the process. This process takes place at 18:00.

4. Preparation before planting

1) Transfer 15L of leafy vegetable nutrient solution into the aerosol cultivation box (53mc×37cm×23cm). The major elements in the leafy vegetable nutrient solution adopt the Japanese garden formula, and the trace element formula adopts Holland’s general formula (mg/L) ,as follows:

Japanese Garden Recipe

Holland's Universal Formula

2) Set the cycle spray timer, spray 15 minutes every 15 minutes during the day, and spray 5 minutes every 60 minutes at night, this embodiment defines 7:00 to 19:00 as daytime, 19:00 to 7:00 the next day for night.

5. Colonization

1) Use the plant fixer matched with the aerosol cultivation box to fix the root neck of the seedling to be transplanted, and then insert it into the planting hole on the aerosol cultivation box. The plant fixer matched with the aerosol cultivation box adopts ethylene- Made of vinyl acetate copolymer foam.

2) Move lettuce and cherry radish to one aerosol cultivation box for intercropping at a ratio of 1:1, and at the same time move all lettuce to another aerosol cultivation box as a control group to complete colonization.

3) The diameter of the planting hole of the aerosol cultivation box used in this embodiment is 5.5 cm, and a plant holder with a diameter of 6 cm and a thickness of 1.5 cm is selected.

6. Set the cultivation environment

The aerosol cultivation box was placed in a greenhouse environment for cultivation, and the greenhouse environment was set at a daytime temperature of 25°C and a nighttime temperature of 15°C.

7. Adjust the pH value and EC value of the nutrient solution in the aerosol cultivation box

1) Insert the probe of the Hana HI98129 acidity meter into the nutrient solution, and read the pH value and EC value of the nutrient solution directly after the reading is stable.

2) Measure the pH value and EC value of the nutrient solution in the aerosol cultivation box at 12:00 every day. If the two are in the range of 5.8-6.2 and 1900-2300 μS/cm respectively, no adjustment is required.

3) If the measured pH value of the nutrient solution in the aerosol cultivation box is less than 5.8, add 2 mol/L sodium hydroxide solution dropwise while measuring the pH value of the nutrient solution until the measured value is within the range of 5.8 to 6.2; If the pH value of the obtained nutrient solution in the aerosol cultivation box is greater than 6.2, add 2 mol/L sulfuric acid solution dropwise while measuring the pH value of the nutrient solution until the measured value is within the range of 5.8 to 6.2.

4) If the measured EC value of the nutrient solution in the aerosol cultivation box is less than 1900μS/cm, add the nutrient solution while measuring the EC value of the nutrient solution until the measured value is within the range of 1900-2300μS/cm; if the measured If the EC value of the nutrient solution in the aerosol cultivation box is greater than 2300 μS/cm, add water while measuring the EC value of the nutrient solution until the measured value is in the range of 1900-2300 μS/cm.

8. Plant Harvesting

It can be harvested after 30-50 days after the lettuce and cherry radish are planted.

Example 2

The steps of the soilless cultivation method for reducing lettuce leaf nitrate are as follows:

1. Soaking seeds and germination

1) Soak lettuce seeds in warm water at 55°C for 15 minutes, stirring constantly;

2) Wrap the seeds with clean wet gauze and germinate them in an incubator at 28°C for about 1 day. When 80-90% of the seeds open and sprout, sow them in plastic nutrition bowls, and sow 1-2 seeds in each bowl.

3) The operation of pea seeds is the same as that of lettuce seeds. The difference is that pea seeds need to be soaked in water at 10-30°C for 20-24 hours and the operation should be performed 15±1 days later to ensure that the two seedlings are transplanted at the same time.

2. Seedling cultivation in artificial climate chamber

1) Put the plastic nutrient bowl in which the seeds have been sown into an artificial climate box to grow seedlings. During the day, the temperature is controlled at 26°C and the light level is 5, at night the temperature is controlled at 16°C and the light level is 0, and the relative humidity is kept at 80% RH.

2) When the lettuce grows 3-4 true leaves and the pea shoots are 5-6cm high, prepare to transplant the seedlings.

3. Transplanting seedlings

1) Fully water the soil before transplanting seedlings to reduce damage to roots during transplanting.

2) Gently separate the soil and the root system to be transplanted, and then clean the root system to be transplanted, ensuring the integrity of the root system of the plant during the process. This process takes place at 18:00.

4. Preparation before planting

1) Transfer 15L of leaf vegetable nutrient solution into the aerosol cultivation box (53mc×37cm×23cm). The major elements in the nutrient solution adopt the Japanese garden formula, and the trace element formula adopts Holland’s general formula (mg/L), as follows :

Japanese Garden Recipe

Holland's Universal Formula

2) Set a cycle spray timer, spray 15 minutes every 15 minutes during the day, and spray 5 minutes every 60 minutes at night. In this embodiment, 7:00 to 19:00 is defined as daytime, and 19:00 to 7:00 the next day is defined as nighttime.

5. Colonization

1) Fix the root neck of the seedling to be transplanted with the plant fixer matched with the aerosol cultivation box, and then insert it into the planting hole on the aerosol cultivation box. The plant fixer matched with the aerosol cultivation box is ethylene- Vinyl acetate copolymer foam.

2) Move lettuce and pea seedlings into one aerosol cultivation box for intercropping at a ratio of 1:1, and at the same time move all lettuce into another aerosol cultivation box as a control group to complete colonization.

3) The diameter of the planting hole of the aerosol cultivation box used in this embodiment is 5.5 cm, and a plant holder with a diameter of 6 cm and a thickness of 1.5 cm is selected.

6. Set the cultivation environment

The aerosol cultivation box was placed in a greenhouse environment for cultivation, and the greenhouse environment was set at a daytime temperature of 25°C and a nighttime temperature of 15°C.

7. Adjust the pH value and EC value of the nutrient solution in the aerosol cultivation box

1) Insert the probe of the Hana HI98129 acidity meter into the nutrient solution, and read the pH value and EC value of the nutrient solution directly after the reading is stable.

2) Measure the pH value and EC value of the nutrient solution in the aerosol cultivation box at 12:00 every day. If the two are in the range of 5.8-6.2 and 1900-2300 μS/cm respectively, no adjustment is required.

3) If the measured pH value of the nutrient solution in the aerosol cultivation box is less than 5.8, add 2 mol/L sodium hydroxide solution dropwise while measuring the pH value of the nutrient solution until the measured value is within the range of 5.8 to 6.2; If the obtained pH value of the nutrient solution in the aerosol cultivation box is greater than 6.2, add 2 mol/L sulfuric acid solution dropwise while measuring the pH value of the nutrient solution until the measured value is within the range of 5.8 to 6.2.

4) If the measured EC value of the nutrient solution in the aerosol cultivation box is less than 1900μS/cm, add the nutrient solution while measuring the EC value of the nutrient solution until the measured value is within the range of 1900-2300μS/cm; if the measured If the EC value of the nutrient solution in the aerosol cultivation box is greater than 2300 μS/cm, add water while measuring the EC value of the nutrient solution until the measured value is within the range of 1900-2300 μS/cm.

8. Plant Harvesting

1) The lettuce can be harvested after 30-40 days of planting;

2) When the pea shoots are about 15cm high, cut the pea shoots from the base to eat. After 2 to 3 days, the base of the pea shoots will grow tender shoots, and the harvest and growth will be repeated.

The effect verification of the soilless cultivation method for reducing nitrate of lettuce leaves according to the present invention is the detection of nitrate in lettuce leaves.

30 days after the plants were planted, three experiments were conducted with reference to the "Principles and Techniques of Plant Physiological and Biochemical Experiments" edited by Li Hesheng. The average plant weight, root activity, and leaf nitrate content of lettuce under the three modes were measured, and the total nitrogen content in the nutrient solution under the three modes was measured at the same time to calculate the nitrogen use efficiency. The results are as follows:

It can be seen from the above table that the average plant weight, root activity and nitrogen use efficiency of the lettuce under the two intercropping patterns were all higher than those under the monocropping pattern, while the nitrate content of the leaves was lower than that of the lettuce under the monocropping pattern, and both The nitrate content of lettuce leaves decreased by 27.30% and 57.13% respectively under intercropping mode. It can be seen that the lettuce cultivated by the soilless cultivation method for reducing nitrate of lettuce leaves according to the present invention has good yield and income increasing benefits, environmental adaptability, and high resource utilization rate. At the same time, the nitrate content of the leaves is reduced, which ensures the quality of the lettuce and can provide people with safe and secure vegetables.

Claims (8)

1. reduce the soilless culture method of lettuce leaf nitrate, it is characterized in that, the described step of the soilless culture method that reduces lettuce leaf nitrate is as follows: 1) Seed soaking and germination, the steps are as follows: (1) Soak the seeds in warm water at 55°C for 15 minutes, stir continuously, and then soak the seeds in clean water at 10-30°C for 0-24 hours to allow the seeds to fully absorb water; (2) Wrap the seeds with clean wet gauze and germinate in an incubator at 28°C to 30°C for 1 to 2 days. When 80 to 90% of the seeds open and sprout, they are sown into plastic nutrition bowls, and 1 to 2 2 seeds; (3) Seed soaking time varies from species to species. Lettuce and cabbage seeds are not soaked to germinate directly, cherry radish seeds are soaked for 6h-8h, and pea seeds are soaked for 20h-24h; 2) Cultivate seedlings in an artificial climate box, the steps are as follows: (1) Put the plastic nutrient bowl that has been seeded into the artificial climate box to grow seedlings. During the day, the temperature is controlled at 25-30°C, the illuminance is 5-6, and the nighttime temperature is 15-20°C, the illuminance is 0, and the relative humidity is controlled. Controlled at 70-80% RH; (2) Prepare to transplant seedlings when lettuce, Chinese cabbage and cherry radish grow 3 to 4 true leaves, and the pea shoots are 5 to 6 cm high; (3) In order to ensure that the crops can be transplanted at the same time, lettuce, Chinese cabbage, and cherry radish are raised in the same batch, while pea seedlings should be raised 15 ± 1d later; 3) Transplanting seedlings; 4) Preparation before planting; 5) Colonization; 6) Set the cultivation environment; 7) Adjust the pH value and electrical conductivity of the nutrient solution in the aerosol cultivation box, that is, the EC value; 8) Plant harvesting. 2. according to the soilless cultivation method that reduces lettuce leaf nitrate according to claim 1, it is characterized in that, the step of described transplanting seedlings is as follows: 1) Fully water the soil before transplanting the seedlings to reduce the damage to the roots when transplanting the seedlings; 2) Gently separate the soil and the root system to be transplanted, and then clean the root system to be transplanted, ensuring the integrity of the root system of the plant during the process; 3) This process is carried out in the evening, that is, from 17:00 to 19:00 or on cloudy days. At this time, the transpiration of plants is weakened, which improves the survival rate of transplanted seedlings. 3. according to the soilless culture method that reduces lettuce leaf nitrate according to claim 1, it is characterized in that, the step of preparation before described field planting is as follows: 1) Transfer 1/3 to 1/2 volume of leaf vegetable nutrient solution into the aerosol cultivation box, and the highest liquid level of the nutrient solution should not exceed the spray head in the aerosol cultivation box; 2) Set a cycle spray timer, spray 15 minutes every 15 minutes during the day, and spray 5 minutes every 60 minutes at night. 4. according to the soilless cultivation method of reducing lettuce leaf nitrate according to claim 3, it is characterized in that, in the described leaf vegetable nutrient solution, macroelement adopts Japanese garden formula, and trace element formula adopts Holland general formula, The unit is mg/L, as follows: Japanese Garden Recipe Holland's Universal Formula 5. according to the soilless cultivation method that reduces lettuce leaf nitrate according to claim 1, it is characterized in that, the step of described field planting is as follows: 1) Use the plant fixer matched with the aerosol cultivation box to fix the root neck of the seedling to be transplanted, and then insert it into the planting hole on the aerosol cultivation box. The plant fixer matched with the aerosol cultivation box adopts ethylene- Made of vinyl acetate copolymer foam material; 2) Move lettuce and Chinese cabbage, cherry radish or pea sprouts into one aerosol cultivation box, intercropping at a ratio of 1:1, and simultaneously move all lettuce into another aerosol cultivation box, as a control group; 3) The plant fixer with a diameter of 6cm and a thickness of 1.5cm is suitable for the planting hole of the aerosol cultivation box with a diameter of 5.5-5.9cm. 6. according to the soilless cultivation method that reduces lettuce leaf nitrate according to claim 1, it is characterized in that, the step of described setting cultivation environment is as follows: The aerosol cultivation box was placed in a greenhouse environment for cultivation, and the greenhouse environment was set at a daytime temperature of 25±2°C and a nighttime temperature of 15±2°C. 7. according to the soilless cultivation method that reduces lettuce leaf nitrate according to claim 1, it is characterized in that, the pH value of described regulation aerosol cultivation box and the step of electrical conductivity i.e. EC value of nutrient solution are as follows: 1) Insert the probe of the portable acidity meter into the nutrient solution, and read the pH value and EC value of the nutrient solution directly after the reading is stable; 2) Measure the pH value of the nutrient solution in the aerosol cultivation box every day, and adjust the pH value by adding 1-2 mol/L sulfuric acid solution or 1-2 mol/L sodium hydroxide solution to control the pH value of the nutrient solution at 5.8-6.2 ; 3) Measure the EC value of the nutrient solution in the aerosol cultivation box every day, and adjust the EC value by adding water or nutrient solution, so that the EC value of the nutrient solution is controlled at 1900-2300 μS/cm. 8. according to the soilless culture method that reduces lettuce leaf nitrate according to claim 1, it is characterized in that, the step of described plant harvesting is as follows: 1) It can be harvested after 30-50 days after the lettuce, cabbage and cherry radish are planted; 2) When the pea shoots are about 15cm high, cut the pea shoots from the base to eat. After 2 to 3 days, the base of the pea shoots will grow tender shoots, and the harvest and growth will be repeated.