Plant factory nutrient solution element concentration correction method and application thereof

Abstract

The invention belongs to the field of soilless culture, and particularly discloses a plant factory nutrient solution element concentration correction method and application thereof. The plant factory nutrient solution element concentration correction method comprises the steps that in the process of multiple crops of hydroponic plants under the stable environment condition of a plant factory, a steady-state environment element correction solution is added into a residual nutrient solution completing a specific growth stage of the plants in each crop for nutrient solution element correction, and performing the growth stage of the next crop of plants by using the nutrient solution subjected to element correction. The method is suitable for being applied to multi-crop repeated standardized production in a plant factory, consumption in the nutrient solution can be accurately supplemented without frequently detecting elements, the service life of the nutrient solution can be prolonged for multi-crop plant production, pollution of the waste nutrient solution to the environment is reduced while resources are saved, and the method is suitable for popularization and application. And the advantages in the large-scale production of plants are further amplified.

Description

Technical Field

[0001] This application belongs to the field of soilless cultivation, and specifically relates to a method for correcting the concentration of nutrient solution elements in a plant factory and its application. Background Technique

[0002] A plant factory is an advanced production method for efficient annual production of crops in a controllable environment, which can effectively ensure the stable supply of food.

[0003] In order to maintain the standardization, cleanliness, and high efficiency of product production, most artificial light plant factories adopt nutrient solution circulation cultivation and continuously monitor the electrical conductivity (EC) value. When the EC value changes, it is adjusted by adding a supplementary solution based on the mother liquor formula. For example, the nutrient solution supplement methods and devices mentioned in CN101491206B, CN117859632A, CN115259495A, and CN212436798U.

[0004] However, EC represents the total ion amount (total elements), and this supplementary method cannot be adjusted according to the plant's demand for single elements. The contradiction between the selective absorption of each element by the plant and the fixed ratio of each element in the mother liquor used for supplementing the nutrient solution is amplified many times in the nutrient solution recycling, ultimately leading to the imbalance of nutrient solution elements, endangering plant growth, and reducing crop yields. At this time, the nutrient solution can only be discarded and discharged, which not only causes a large amount of water and fertilizer waste but also seriously affects the natural environment. Therefore, only by supplementing the used nutrient solution with targeted elements can the imbalance of elements in it be corrected and the service life of the nutrient solution be extended.

[0005] The environment is an important factor affecting the absorption of plant elements. Therefore, in greenhouses vulnerable to nature, the supplementation of nutrient solution elements needs to rely on regular detection to correct the deviation of element absorption caused by environmental impact. As Savvas (Improvement and validation of a decision support system to maintain optimal nutrient levels in crops grown in closed-loop soilless systems. Agricultural Water Management) and Gallardo (Decision support systems and models for aiding irrigation and nutrient management of vegetable crops. Agricultural Water Management) combined elemental chemical analysis and elemental correction models, the automatic adjustment of nutrient solution elements can be completed by inputting a small number of parameters. However, regular elemental chemical analysis incurs high detection costs, and the long feedback cycle of detection results is also difficult to meet the needs of the changes in cultivation stages and crop rotations in actual production.

[0006] Due to the need for rapid element detection and real-time correction, element detection sensors have received increasing attention due to their advantages such as wide detection range, fast speed, and small size. They are used in CN107894786A, CN106508226A, CN103798116B, CN103499984B, and CN118527015A. However, element detection sensors have poor anti-interference ion ability and are easily affected by the accumulation of organic matter in the nutrient solution during long-term use, resulting in reduced accuracy, and it is still relatively difficult to apply them widely in nutrient solution management.

[0007] The internal environment of the plant factory is stable, and the production operations are unified and standardized, fully ensuring the consistency of plant growth. The stable environment makes the element absorption of plants relatively fixed, which means that the plants cultivated in the plant factory have regular element absorption characteristics, and the element correction cost can be reduced accordingly to achieve efficient nutrient solution element correction. Summary of the Invention

[0008] The technical problem to be solved by the present invention is how to accurately supplement the element consumption in the nutrient solution without frequent element detection during the multi-crop repeated standardized production process of plants, so as to extend the service life of the nutrient solution to supply multi-crop plant production, save resources and reduce the pollution of the environment by waste nutrient solution.

[0009] To solve the above problems, the present invention first provides a method for correcting nutrient solution elements. The method includes, during the process of cultivating hydroponic plants in multiple batches under stable environmental conditions in a plant factory, adding a steady-state environmental element correction solution to the remaining nutrient solution after each batch has completed a specific growth stage of the plants, and then proceeding to the next growth stage of the plants in the next batch;

[0010] The steady-state environmental element correction solution is a supplementary solution for supplementing the consumption of elements in the nutrient solution after cultivating the plants in a single batch with the initial nutrient solution under the stable environmental conditions.

[0011] The element correction refers to the process of restoring the concentration and volume of the elements in the nutrient solution after cultivation to be the same as or close to those of the nutrient solution before the start of cultivation.

[0012] The preparation method of the steady-state environmental element correction solution is as follows: Detect the consumption of nutrient solution elements in a single batch of plants cultivated with the initial nutrient solution under the stable environmental conditions, and formulate the steady-state environmental element correction solution with the goal of supplementing this consumption. It specifically includes steps A1, A2, and A3:

[0013] A1. Detect the concentration and volume of each element in the initial nutrient solution under the stable environmental conditions, and detect the concentration and volume of each element in the remaining nutrient solution after cultivating the plants in a single batch to complete the growth stage. Calculate the consumption of each element using formula 1:

[0014] n = C1V1 - C2V21

[0015] In the formula, n is the consumption of a certain element in the nutrient solution, with the unit of mmol or μmol; C1 is the concentration of this element in the initial nutrient solution, with the unit of mmol·L -1 or μmol·L -1 ; V1 is the volume of the initial nutrient solution at the start of single-batch cultivation, with the unit of L; C2 is the concentration of this element in the remaining nutrient solution after completing the growth stage in a single batch, with the unit of mmol·L -1 or μmol·L -1 ; V2 is the volume of the remaining nutrient solution after completing the growth stage in a single batch, with the unit of L;

[0016] A2. Calculate the EC of the steady-state environmental element correction solution according to formula 2:

[0017]

[0018] In the formula, ECs is the preset EC of the steady-state environmental element correction solution, that is, the value to be obtained; EC o is the target EC after adding the steady-state environmental element correction solution, with the unit of mS / cm, the same as the EC of the initial nutrient solution; EC rEC is the EC of the remaining nutrient solution after a single crop cycle has completed the growth stage; f is the percentage of the volume V2 of the remaining nutrient solution after a single crop cycle has completed the growth stage to the total volume of the nutrient solution for the next crop cycle.

[0019] A3. Based on the calculation results of A1 and A2, design the components and dosages of the steady-state environmental element correction solution. At the same time, based on Formula 3, with the goal of ECs reaching or approaching the EC of the preset steady-state environmental element correction solution in A2, adjust the dosages of each component to achieve that the element content and EC in the nutrient solution after supplementing the remaining nutrient solution to the initial nutrient solution volume with the steady-state environmental element correction solution are the same as or close to those of the initial nutrient solution, thus completing the correction of nutrient solution elements.

[0020]

[0021] In the formula, is the sum of the products of the concentrations and valences of each cation in the steady-state environmental element correction solution, with the unit meq·L -1 , representing K in the nutrient solution with the concentrations of potassium, calcium, magnesium, and ammonium nitrogen elements + 、Ca 2+ 、Mg 2+ and NH4 + cation concentrations to calculate EC.

[0022] In the above method, the growth stage is divided according to the standard that the regular change range of element absorption within a certain concentration range is relatively small under the stable environmental conditions of the plant factory. For example, leafy vegetables have a short cultivation cycle, and the regular change range of element absorption during the period from the completion of seedling raising to harvesting is relatively small, so it can be directly used as a growth stage. Another example is that flowers and fruit vegetables often have a large regular change in element absorption during vegetative growth and reproductive growth, and can often be divided into two or more growth stages, and a steady-state environmental element correction solution suitable for each growth stage is used respectively.

[0023] In the above method, the plant can be various plants suitable for hydroponic production in the prior art, including vegetables, flowers, medicinal materials, etc.; preferably leafy vegetables, such as lettuce.

[0024] In the above method, the stable environmental conditions are set according to the requirements of the specific plant and specific growth stage.

[0025] In the above method, the initial nutrient solution has its specific components and dosages set according to the requirements of the specific plant and specific growth stage. Existing nutrient solution formulas in the prior art can be selected. For example, for lettuce cultivation, improved Cornell lettuce nutrient solution, Hoagland nutrient solution, Japanese garden test nutrient solution, Japanese Yamazaki nutrient solution, South China Agricultural University leafy vegetable nutrient solution, etc. can be used.

[0026] In the above method, the initial nutrient solution components refer to the compounds for formulating the initial nutrient solution. The steady-state environmental element correction solution components refer to the compounds for formulating the steady-state environmental element correction solution.

[0027] In the above method, the compounds are selected from the compounds commonly used in the prior art for formulating nutrient solutions. For example, for the nitrogen-containing compounds, one or more of KNO3, Ca(NO3)2·4H2O, (NH4)2SO4, (NH4)2HPO4, and NH4H2PO4 can be selected; for the phosphorus-containing compounds, one or more of (NH4)2HPO4, NH4H2PO4, KH2PO4, K2HPO4, and (NH4)2SO4 can be selected; for the potassium-containing compounds, one or more of KNO3, K2SO4, KH2PO4, and K2HPO4 can be selected; for the calcium-containing compounds, Ca(NO3)2·4H2O can be selected; for the magnesium-containing compounds, MgSO4·7H2O can be selected; for the sulfur-containing compounds, one or more of MgSO4·7H2O, K2SO4, and (NH4)2SO4 can be selected; for the iron-containing compounds, one or more of EDTA-NaFe and EDTA-Na2Fe can be selected; for the manganese-containing compounds, one or more of MnSO4·4H2O and MnSO4·H2O can be selected; for the zinc-containing compounds, ZnSO4·7H2O can be selected; for the copper-containing compounds, CuSO4·5H2O can be selected; for the boron-containing compounds, one or more of H3BO3 and Na2B4O7SO4·10H2O can be selected; for the molybdenum-containing compounds, one or more of (NH4)6Mo7O 24 ·10H2O and Na2MoO4·2H2O can be selected.

[0028] In the above method, the plant is lettuce, the stable environmental conditions are a temperature of 22 ± 0.5 °C, the light source is LED full-spectrum white light, the light-dark period is 16 h / 8 h, and the canopy effective photosynthetic radiation is 200 μmol·m -2 ·s -1, relative humidity (65±10)%, carbon dioxide concentration 400±50 μmol / mol, the initial nutrient solution is the modified Cornell lettuce nutrient solution (formula shown in Table 1), the growth stage is from 14 days after seeding to harvest, and the cultivation is deep flow solution culture with 80 L of nutrient solution for 18 days. Then the formula of the steady-state environmental element correction solution is: 0.436 g / L KNO3, 0.784 g / L Ca(NO3)2·4H2O, 0.024 g / L (NH4)2SO4, 0.168 g / L (NH4)2HPO4, 0.179 g / L MgSO4·7H2O, 21.59 mg / L EDTA-NaFe, 6.47 mg / L MnSO4·H2O, 6.82 mg / L Na2B4O7·10H2O, and 0.06 mg / L Na2MoO4·2H2O.

[0029] The present invention also provides a preparation method of the steady-state environmental element correction solution: It is to detect the consumption amount of nutrient solution elements in a certain growth stage of a plant with a single crop of the initial nutrient solution under stable environmental conditions, and formulate the steady-state environmental element correction solution with the goal of supplementing this consumption amount, so that it can supplement the content of each element in the nutrient solution and the volume of the nutrient solution reaches or approaches the initial state before cultivation. Ideally, it can maintain the constancy of the element content and volume before and after nutrient solution cultivation, specifically including steps A1, A2, and A3:

[0030] A1. Detect the concentration and volume of each element of the initial nutrient solution under the stable environmental conditions, and detect the concentration and volume of each element of the remaining nutrient solution after completing the cultivation of the plant in the growth stage with a single crop. Calculate the consumption amount of each element according to formula 1:

[0031] n = C1V1 - C2V21

[0032] In the formula, n is the consumption amount of a certain element in the nutrient solution, with the unit of mmol or μmol; C1 is the concentration of this element in the initial nutrient solution, with the unit of mmol·L -1 or μmol·L -1 ; V1 is the volume of the initial nutrient solution at the beginning of single-crop cultivation, with the unit of L; C2 is the concentration of this element in the remaining nutrient solution after completing the growth stage with a single crop, with the unit of mmol·L -1 or μmol·L -1 ; V2 is the volume of the remaining nutrient solution after completing the growth stage with a single crop, with the unit of L;

[0033] A2. Preset the EC of the steady-state environmental element correction solution according to formula 2:

[0034]

[0035] In the formula, EC oThe target EC after adding the steady-state environmental element correction solution, in mS / cm, is the same as the EC of the initial nutrient solution; EC r is the EC of the remaining nutrient solution after completing the growth stage for a single crop, in mS / cm; ECs is the EC of the preset steady-state environmental element correction solution, in mS / cm; f is the percentage of the volume V2 of the remaining nutrient solution after completing the growth stage for a single crop to the total volume of the nutrient solution for the next crop;

[0036] A3. Based on the calculation results of A1 and A2, design the components and dosage of the steady-state environmental element correction solution. At the same time, based on Formula 3, with the goal of ECs reaching or approaching the EC of the preset steady-state environmental element correction solution in A2, adjust the dosage of each component to achieve that the element content and EC in the nutrient solution after supplementing the remaining nutrient solution to the volume of the initial nutrient solution with the steady-state environmental element correction solution are the same as or close to those of the initial nutrient solution, thus completing the correction of the nutrient solution elements;

[0037]

[0038] In the formula, is the sum of the products of the concentrations and valences of each cation in the steady-state environmental element correction solution, in meq·L -1 ; Represent the K in the nutrient solution with the concentrations of potassium, calcium, magnesium and ammonium nitrogen elements + 、Ca 2+ 、Mg 2+ and NH4 + cation concentration to calculate EC.

[0039] The present invention also provides a steady-state environmental element correction solution produced by the above preparation method.

[0040] In the examples of the present invention, a steady-state environmental element correction solution for the factory production of lettuce produced by the above preparation method is recorded. Its formula is 0.436 g / L KNO3, 0.784 g / L Ca(NO3)2·4H2O, 0.024 g / L (NH4)2SO4, 0.168 g / L (NH4)2HPO4, 0.179 g / L MgSO4·7H2O, 21.59 mg / L EDTA-NaFe, 6.47 mg / L MnSO4·H2O, 6.82 mg / L Na2B4O7·10H2O and 0.06 mg / L Na2MoO4·2H2O. It is used for the multi-crop standardized production of lettuce with the initial nutrient solution being the modified Cornell lettuce nutrient solution and the growth stage being 18 days from the seedling age of 14 days to harvesting under stable environmental conditions. After each crop at this growth stage is cultivated, the remaining nutrient solution is supplemented to correct the nutrient solution elements and then the next crop of lettuce at this growth stage is produced.

[0041] The present invention also provides the application of the above method in plant factory (standardized) production.

[0042] The present invention also provides the application of the above steady-state environmental element correction solution in the factory (standardized) production of lettuce.

[0043] The present invention is suitable for multi-crop repeated standardized production in a plant factory, and its advantages will be further amplified in large-scale production. The specific beneficial effects of the present invention are as follows:

[0044] 1. Once the cultivation environment and operation process are fixed, it is only necessary to detect the content of each element in the newly prepared nutrient solution and the nutrient solution at the end of the first crop cultivation to determine the supplementary solution applicable to multi-crop cultivation, achieving a good nutrient solution element correction effect. During this period, there is no need to perform element detection again, reducing the element correction cost, and at the same time extending the service life of the nutrient solution during the recycling of the nutrient solution.

[0045] 2. Although there are still deviations in this method and it is impossible to completely supplement the consumed nutrient elements. Generally speaking, the concentration of each element is closer to the average concentration of the newly prepared nutrient solution than that of the control group, especially the supplementation of macronutrients calcium, magnesium, and sulfur, and micronutrient manganese.

[0046] 3. The element composition during the recycling of the nutrient solution using this method is more suitable for the growth of lettuce. Starting from the fourth crop, there are significant differences in the growth of lettuce treated with the steady-state environmental element correction solution (ECSSE) and the control group that only adjusts the EC. Its stem diameter, above-ground fresh weight, underground fresh weight, number of leaves, and leaf area are significantly increased by 13.6%, 32.7%, 41.2%, 10.2%, and 32.8% respectively compared with the control group; the root surface area, root volume, and number of branches are significantly increased by 27.9%, 38.2%, and 30.3% respectively compared with the control group. By the fifth crop, the ECSSE treatment still maintains an advantage over the control group, and its stem diameter, above-ground fresh weight, and underground fresh weight are significantly increased by 19.1%, 29.3%, and 36.7% respectively compared with the control group; the total root length and number of branches are significantly increased by 15.0% and 29.8% respectively compared with the control group. Description of the Drawings

[0047] Figure 1 It is the consumption of macronutrients and micronutrients of single-crop lettuce in Example 1 of the present invention. Figure 1 A is the consumption of macronutrients; Figure 1B is the consumption of trace elements. In the figure, the numbers on the bar graph represent the number of moles decreased or increased. The white bars represent the elemental moles in the new nutrient solution (EMNS); the gray bars represent the elemental moles in the harvested nutrient solution after 18-day cultivation of lettuce in a single crop (EMHS).

[0048] Figure 2 This shows the content changes of the major elements potassium, calcium, magnesium, sulfur, nitrogen, and phosphorus in the nutrient solution at the start of each crop (cultivation day 0) under different supplementation methods in Example 2 of the present invention. SC: Standard concentration of elements in the new nutrient solution; ECSSE: Treatment with steady-state environmental element correction solution; CK: Supplementary dilution of the mother liquor

[0049] Figure 3 This shows the content of each element in the nutrient solution at the start of the fifth crop cultivation (after all four supplements) under different supplementation methods in Example 1 of the present invention.

[0050] Figure 4 This shows the effects of different supplementation methods on the growth of lettuce in each crop in Example 1 of the present invention. Among them, 2-ECSSE is the ECSSE treatment in the second crop, 2-control group is the control in the second crop, 3-ECSSE is the ECSSE treatment in the third crop, 3-control group is the control in the third crop, 4-ECSSE is the ECSSE treatment in the fourth crop, 4-control group is the control in the fourth crop, 5-ECSSE is the ECSSE treatment in the fifth crop, and 5-control group is the control in the fifth crop.

[0051] Figure 5 This shows the effects of different supplementation methods on the root morphology of lettuce in each crop in Example 1 of the present invention. Among them, 2-ECSSE is the ECSSE treatment in the second crop, 2-control group is the control in the second crop, 3-ECSSE is the ECSSE treatment in the third crop, 3-control group is the control in the third crop, 4-ECSSE is the ECSSE treatment in the fourth crop, 4-control group is the control in the fourth crop, 5-ECSSE is the ECSSE treatment in the fifth crop, and 5-control group is the control in the fifth crop. Detailed implementation manners

[0052] The present invention will be further described in detail below in combination with specific implementation manners. The given examples are only for clarifying the present invention, rather than limiting the scope of the present invention. The following examples can be used as a guide for those of ordinary skill in the art to make further improvements, and do not limit the present invention in any way.

[0053] The materials, reagents, etc. used in the following examples can be obtained from commercial channels without special instructions.

[0054] The lettuce variety Tiberius RZ in the following embodiments is a product of Rijk Zwaan.

[0055] The lettuce seedling raising process in the following embodiments is as follows:

[0056] Sow lettuce seeds (Lactuca sativa cv. Tiberius RZ) on a moist large sponge block composed of 63 small sponge blocks connected together. Sow 1 seed in each small sponge block, for a total of 63 seeds sown. The dimensions of each small sponge block in length, width, and height are 25 mm × 25 mm × 25 mm. Place the large sponge block in a seedling tray (330 mm × 225 mm × 40 mm). Spray each seed 4 times with a watering can to ensure it is fully moistened. Add deionized water to the seedling tray until it covers the bottom end of the sponge block by about 5 mm, and germinate in the dark in a constant temperature incubator (GLED-400PY, Beijing Luxi Technology Co., Ltd.) at 23.5 °C for 44 h. After the lettuce seeds show white tips, transfer them to a plant factory with a temperature of (22 ± 0.5) °C, a light source of LED full-spectrum white light, a light-dark period of 16 h / 8 h, a canopy effective photosynthetic radiation of 150 μmol·m -2 ·s -1 , a relative humidity of (65 ± 10)%, and a carbon dioxide concentration of (400 ± 50) μmol / mol for 14 days of seedling raising. During this period, irrigate with modified Cornell nutrient solution (pH = 6.3 ± 0.2, EC = 1.45 ± 0.5 mS / cm, and the specific formula is shown in Table 1).

[0057] Table 1 Formula of modified Cornell lettuce nutrient solution

[0058]

[0059]

[0060] The specific measurement methods for each index in the following embodiments are as follows:

[0061] 1 Nutrient solution volume measurement

[0062] The nutrient solution volume consists of two parts: the nutrient solution in the nutrient solution tank and the nutrient solution in the cultivation tank. Use a ruler to measure the liquid level depth of the nutrient solution tank and the cultivation tank, and combine their respective lengths and widths to obtain the nutrient solution volume.

[0063] 2 Nutrient solution sampling and element content determination

[0064] Before sampling, the nutrient solution in the deep liquid flow system was fully mixed, and then a 100 ml small beaker was used to sample the nutrient solution according to the volume ratio of the nutrient solution in the nutrient solution tank and the cultivation tank, and poured into a 1 L large beaker and mixed. The sample was filtered through a 0.45 μm polyethersulfone microporous filter membrane (Tianjin Jinteng Experimental Equipment Co., Ltd.) in a 50 ml centrifuge tube, and a portion of the filtrate was added with 5 μL of 65% HNO3 diluted 10 times and stored at 4 ° C for metal element determination (potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum), and the remaining filtrate was added with 50 μL of 95% H2SO4 diluted 10 times and stored at -20 ° C for nitrogen and phosphorus determination (total nitrogen, total phosphorus, nitrate nitrogen, ammonium nitrogen).

[0065] The total nitrogen content is determined according to the standard HJ636-2012, using ATC-227 UV-visible spectrophotometer and alkaline potassium persulfate digestion UV spectrophotometer method; the total phosphorus content is determined according to the standard GB / T-11893-1989, using ATC-227 UV-visible spectrophotometer and ammonium molybdate spectrophotometry method; the metal element content is determined according to the standard HJ700-2014, using inductively coupled plasma mass spectrometer and inductively coupled plasma mass spectrometry; nitrate nitrogen and ammonium nitrogen are determined by flow injection method.

[0066] 3. Nutrient solution pH and EC determination

[0067] pH was measured using a portable pH meter (PHB-5; Shanghai Yidian Scientific Instrument Co., Ltd.); EC was measured using a portable EC meter (HI98130; HANNA, Italy).

[0068] 4. Determination of lettuce growth index

[0069] The stem thickness was measured with a vernier caliper at the plant circumference 1 cm above the contact surface between the plant stem and the sponge block.

[0070] Plant height was measured using a vernier caliper from the base of the plant stem to the growth point.

[0071] The fresh weight and dry weight of the plants were measured using an analytical balance (GL6202-1SCN; Sartorius, Germany). The plants were cut from the base of the stem with scissors to separate the aboveground part and the underground part. The underground part was wrapped with absorbent paper and pressed 5 times to absorb the residual nutrient solution in the underground part, and the fresh weight of the aboveground part and the underground part were weighed separately.

[0072] The leaf number refers to the number of all true leaves. The leaf area was measured using a leaf area meter (LI-3100C; LI-COR, USA).

[0073] For root morphological indexes, the WinRHIZO root analysis system was used to analyze the root images scanned by a root scanner (V850 Pro; Epson, Japan) to determine the total root length, root surface area, root volume, average root diameter, number of root tips, and number of branches.

[0074] For other experimental methods in the following examples, if not otherwise specified, they are all conventional methods.

[0075] For quantitative tests in the following examples, if not otherwise specified, three repeated experiments were set, and the results were averaged.

[0076] In the following examples, SPSS 26.0 statistical software was used to process the data. The experimental results were expressed as mean ± standard deviation. The T-test method was used for significant difference analysis. P < 0.05 (*) indicates a significant difference, P < 0.01 (**) indicates a highly significant difference, and P < 0.001 (***) indicates a highly significant difference. Origin 2021 was used for plotting.

[0077] Example 1 Preparation of Steady-State Environmental Element Calibration Solution

[0078] The internal environment of the plant factory is completely controllable, and production operations are convenient for unified standardized management. Plant planned production can be carried out according to pre-set parameters, fully ensuring the consistency of plant growth and the regularity of element absorption within a certain concentration range during the same growth stage.

[0079] During vegetative growth and reproductive growth, the regular changes in element absorption by flowers and fruit vegetables are relatively large, and they can often be divided into two or more growth stages. It is necessary to use a steady-state environmental element calibration solution suitable for each growth stage separately. Leafy vegetables have the characteristics of a short cultivation cycle and a single growth stage in actual production, which ensures the consistency between the plant element absorption tendency and the cultivation cycle, that is, there is no need to dynamically adjust the nutrient element composition of each stage according to the change of the plant growth stage, so as to achieve the consistency between the nutrient element supplement cycle and the cultivation cycle.

[0080] As a fresh leafy vegetable, lettuce (Lactuca sativa cv.) has the characteristics of a short cultivation cycle and a single growth stage in actual production. Therefore, this invention takes lettuce as the object, adopts a fixed variety and cultivation operation process, and determines the fixed consumption of nutrient solution elements per crop of lettuce in a specific production mode under the stable environmental conditions of a plant factory. With the goal of making as precise an elemental correction as possible for this consumption, a steady-state environmental element correction solution (ECSSE) is formulated. After the nutrient solution is used, this correction solution is added to the nutrient solution to replenish the consumed nutrient elements, achieving a rebalance of the nutrient solution elements. Based on this, a method for correcting the concentration of nutrient solution elements in a plant factory to extend the service life of the nutrient solution is proposed.

[0081] This example was carried out in the artificial light plant factory laboratory of the Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences from July to August 2024.

[0082] The determination of the steady-state environmental element correction solution under the standardized cultivation process of a plant factory in this invention is carried out according to the following steps:

[0083] 1. Determination of the consumption of elements per crop

[0084] After raising seedlings in the plant factory for 14 days according to the above method, lettuce is cultivated for 18 days per crop using the deep flow technique system. Three independent cultivation systems (including cultivation troughs, nutrient solution tanks, light sources, and environmental control systems such as temperature and humidity) are used as three replicates. One cultivation trough is planted in each cultivation system, and the planting density is 49.8 plants / m 2 , a total of 50 plants. Select seedlings with consistent growth vigor and plant them on a foam plastic board. A total of 80 L of nutrient solution in the cultivation trough (1500 mm × 670 mm × 60 mm) and the nutrient solution tank (482 mm × 482 mm × 800 mm) is circulated by a water pump, with 3 circulation cycles per day (7:00 - 7:30; 14:00 - 14:30; 21:00 - 21:30), for a total of 1.5 hours of circulation. Except that the effective photosynthetic radiation in the canopy is increased to 200 μmol·m -2 ·s -1 , the other environmental parameters are the same as those in the seedling raising stage.

[0085] The volume of the nutrient solution continuously decreases as the plant grows, and the concentration of each element also changes continuously. Under the condition of no new nutrient solution supplementation, the difference in the number of moles of each element (including macronutrients nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and micronutrients iron, manganese, copper, zinc, boron, molybdenum) between the newly prepared nutrient solution and the nutrient solution after cultivation is the element consumption. The calculation formula is shown in Formula 1:

[0086] n = C1V1 - C2V21

[0087] In this embodiment, the formula of the newly prepared nutrient solution adopts the improved Cornell lettuce nutrient solution (see Table 1 for details). After sampling and measuring the element content, the average concentration of the newly prepared nutrient solution is considered as the standard concentration (Standard concentration, SC) for reference of the improved Cornell nutrient solution formula. The initial volume of the nutrient solution V1 is 80 L, and the volume of the nutrient solution V2 is 62.4 L after the cultivation ends. The nutrient solution is sampled and the element content is measured.

[0088] According to Formula 1, the element concentrations of the nutrient solution before and after the 18-day cultivation of a single crop of lettuce are converted into moles. The consumption of macronutrients and micronutrients is as Figure 1 shown. It can be seen that after the cultivation ends, the mole numbers of each element all decrease to varying degrees. However, it is worth noting that the copper element increases by 0.88 μmol. In addition, among the macronutrients, the absorption amount and absorption rate of nitrogen element by lettuce are the largest; among the micronutrients, the absorption amount of iron element by lettuce is the largest, and the absorption rate of manganese element is the largest, reaching 75.3%.

[0089] 2. Determination of the ECSSE target EC

[0090] Taking the target EC as the adjustment standard, the steady-state environment element correction solution (ECSSE) is added to the nutrient solution after the cultivation ends until the total volume of the nutrient solution is the initial volume of the nutrient solution (the same as V1 in step (1), that is, 80 L), to achieve the recycling of the nutrient solution. The EC of the steady-state environment element correction solution is calculated according to Formula 2:

[0091]

[0092] In the formula, EC o is the target EC after adding the steady-state environment element correction solution, the same as the EC (1.45 ± 0.05 mS / cm) of the initial nutrient solution (that is, the newly prepared nutrient solution); EC r is the EC of the remaining nutrient solution after the cultivation of a single crop of lettuce ends, measured as 1.56 mS / cm; ECs is the preset EC of the steady-state environment element correction solution; f is the percentage of the remaining nutrient solution volume V2 after the cultivation of a single crop of lettuce ends, measured as 62.4 L, accounting for the total volume of the next crop of nutrient solution of 80 L, which is 78%.

[0093] According to Formula 2, the range of ECs is 0.83 mS / cm - 1.29 mS / cm.

[0094] 3. Determination of the ECSSE formula

[0095] Based on the above calculation results, the dosages of various fertilizers in ECSSE are designed. At the same time, based on Formula 3, with ECs (the EC of the preset steady-state environmental element correction solution) as the target value, the dosages of various fertilizers in ECSSE are verified and adjusted to complete the correction of nutrient solution elements. The formula is as follows:

[0096]

[0097] In the formula, is the sum of the products of the concentrations and valences of various cations in the steady-state environmental element correction solution, with the unit of meq·L -1 ; The concentrations of K + , Ca 2+ , Mg 2+ and NH4 + cations in the nutrient solution are used for calculation. All nutrient solutions and supplementary solutions are prepared with deionized water, and there are no other cation components. While supplementing to the initial volume of the nutrient solution and maintaining the appropriate EC range, the consumption of each element during the single-crop cultivation period is filled as much as possible.

[0098] In this example, to fill the consumption of each element as much as possible (see Figure 1 ), it is necessary to add supplementary drugs targeted, and at the same time ensure that the EC of the nutrient solution does not change significantly after supplementation and still remains within the suitable growth range of lettuce. The specific operations are shown in Tables 2, 3, and 4.

[0099] As can be seen from Table 2, except for nitrogen element, the other major elements have been filled to the initial level. According to the above, under the experimental conditions, lettuce has the largest absorption amount of nitrogen element. Therefore, drugs with a high proportion of ammonium nitrogen ((NH4)2SO4 and (NH4)2HPO4) are selected as part of the nitrogen source to increase the supplement amount of nitrogen element. Nevertheless, the supplement amount of nitrogen element is still reduced by 25.6 mmol compared with the consumption amount.

[0100] Table 2 The supplement amounts of major elements of single-crop lettuce under experimental conditions

[0101]

[0102]

[0103] Assume that lettuce absorbs nutrient elements normally during cultivation and the volume of the nutrient solution remains unchanged. Then the decrease value of the EC of the nutrient solution caused by absorbing nutrient elements at this time is the consumption EC, and the increase value of the EC generated only after supplementing nutrient elements is the supplement EC. The EC in Table 3 is calculated according to Formula 3. It can be seen that the consumption EC of single-crop lettuce is 0.45, the supplement EC is 0.49, and the deviation value is 0.04. This indicates that the deviation value of the EC of the nutrient solution caused by supplementing ECSSE for nutrient solution element correction is small.

[0104] Table 3 EC consumption and EC supplementation of single-crop lettuce under experimental conditions

[0105]

[0106] Note: The calculated EC value is the EC when the nutrient solution volume is converted to 80 L.

[0107] Table 4 shows the amount of supplementary fertilizers for trace elements during the 18-day cultivation of single-crop lettuce. Except for molybdenum and copper, which are still sufficient and do not need to be supplemented, the other trace elements are replenished to the initial level.

[0108] Table 4 Trace element consumption and supplementation amounts during the cultivation cycle of a single lettuce under experimental conditions

[0109]

[0110] After the above cultivation process is fixed, the steady-state environmental element correction solution supplemented after each crop of lettuce cultivation should contain 7.68 g of KNO3, 13.80 g of Ca(NO3)2·4H2O, 0.42 g of (NH4)2SO4, 2.96 g of (NH4)2HPO4, 3.15 g of MgSO4·7H2O, 0.38 g of EDTA-NaFe, 0.11 g of MnSO4·H2O, 0.12 g of Na2B4O7·10H2O, and 0.001 g of Na2MoO4·2H2O to replenish the consumed elements as much as possible. The volume of the correction solution is V1 - V2, which is 17.6 L.

[0111] Accordingly, the formula of the steady-state environmental element correction solution is 0.436 g / L KNO3, 0.784 g / L Ca(NO3)2·4H2O, 0.024 g / L (NH4)2SO4, 0.168 g / L (NH4)2HPO4, 0.179 g / L MgSO4·7H2O, 21.59 mg / L EDTA-NaFe, 6.47 mg / L MnSO4·H2O, 6.82 mg / L Na2B4O7·10H2O, and 0.06 mg / L Na2MoO4·2H2O.

[0112] Effect of the method for correcting the nutrient element concentration in the plant factory in Example 2

[0113] From August 2024 to December 2024, a nutrient solution recycling experiment of continuously cultivating five crops of lettuce was carried out.

[0114] The seedling raising method and the planting and cultivation environment are the same as those in Example 1.

[0115] The first crop of deep flow lettuce uses a newly prepared nutrient solution (modified Cornell lettuce nutrient solution, the formula is shown in Table 1). The following two groups are set for the nutrient solution supplementation method after each crop cultivation:

[0116] Treatment group (ECSSE): After each crop cultivation ended, the steady-state environmental element correction solution was added to the remaining nutrient solution until the total volume of the nutrient solution in each cultivation tank reached 80 L. After adjusting the pH of the nutrient solution to the appropriate range, the next crop cultivation was carried out.

[0117] Control group (CK): After each crop cultivation ended, the new-made nutrient solution (modified Cornell lettuce nutrient solution, the formula is shown in Table 1, prepared with mother liquor and deionized water) was added to the remaining nutrient solution by the conventional method. The total volume of the nutrient solution in each cultivation tank was adjusted to 80 L. At the same time, after adjusting the EC and pH of the nutrient solution to the appropriate range, the next crop cultivation was carried out.

[0118] Two replicates were set for each of the above treatments. Each replicate used an independent cultivation system. The cultivation system, planting density and environmental parameters were all consistent with the single-crop cultivation in Example 1.

[0119] Starting from the 0th day of each crop cultivation, the pH and EC in the nutrient solution tank were measured every two days, and 20% KOH solution or 85% H3PO4 solution was added to the nutrient solution tank to adjust the pH to the appropriate range (6.0 - 7.0). Starting from the second crop cultivation, the element concentration of the nutrient solution was measured after each nutrient solution supplementation (the 0th day of planting) to clarify the element balance situation. Four plants with consistent growth trends in the middle of the cultivation tank were selected on the 18th day after planting to measure the lettuce growth indexes.

[0120] The measurement results are as follows:

[0121] 1 Effects of different supplementation methods on the initial element concentration of the nutrient solution in each crop

[0122] During the cultivation of five crops of lettuce, the nutrient solution was supplemented 4 times, which were used for the cultivation of the second, third, fourth and fifth crops respectively. The initial concentrations of macronutrients (potassium, calcium, magnesium, sulfur, nitrogen and phosphorus) after each supplementation are shown in Figure 2 . Generally speaking, during the continuous cultivation, the changes in the element concentration of the nutrient solution in the two treatments showed a certain consistency, both showing potassium deficiency and the accumulation of calcium, magnesium and sulfur, while nitrogen and phosphorus were maintained near SC. Specifically, however, the accumulation of calcium, magnesium and sulfur in CK was more serious. When supplemented three times, significant differences began to appear in the three elements of magnesium, sulfur and nitrogen in the two treatments. Among them, the contents of magnesium and sulfur in CK increased by 44.1% and 16.3% respectively compared with the ECSSE treatment, and the nitrogen element decreased by 7.7% compared with the ECSSE treatment. After four supplements, the differences in magnesium and sulfur between the two treatments further increased. The contents of magnesium and sulfur in CK accumulated by 113.1% and 74.1% respectively compared with SC, and the accumulation degree was much higher than 46.4% and 37.6% of the ECSSE treatment. These indicate that the ECSSE treatment played a role in element correction compared with CK. The differences between the concentrations of each element in the nutrient solution and the SC concentration after four supplements with different nutrient solution supplementation methods are shown in Figure 3, the curves in the figure are drawn based on element concentrations to visually show the concentration differences. The closer the curve is to the SC curve, the closer the element concentration in the treatment is to the SC concentration. As mentioned above, the differences in macronutrients before and after the four-time supplementation of the nutrient solution for each treatment all showed potassium deficiency and calcium, magnesium, and sulfur accumulation. Among the micronutrients, the concentrations of iron and zinc elements in each treatment decreased significantly compared to SC, while copper and molybdenum elements showed varying degrees of accumulation. It is worth noting that the concentration of manganese element in CK decreased significantly by 63.6% compared to SC, while there was no significant difference in the concentration of manganese element between the ECSSE treatment and SC. This indicates that in the continuous recycling of the nutrient solution for five consecutive crops, CK caused a serious deficiency of manganese element in the nutrient solution.

[0123] 2 Effects of Different Supplementation Methods on the Growth of Lettuce in Each Crop

[0124] The growth conditions of lettuce in the second to fifth crops are as Figure 4 and Figure 5 shown, and the specific parameters are shown in Tables 5 and 6.

[0125] Table 5 Effects of Different Supplementary Solution Methods on Stem Thickness, Plant Height, Leaf Area, Number of Leaves, and Biomass of Lettuce in Each Crop

[0126]

[0127] Note: Different lowercase letters after the data in the same column indicate significant differences at the 5% level.

[0128] As can be seen from Table 5, in the second and third crops of lettuce, except that the plant height of the ECSSE treatment was significantly higher than that of CK, there were no significant differences in the other indicators. Until the fourth crop, the ECSSE treatment began to show an advantage over CK. Its stem thickness, aboveground fresh weight, underground fresh weight, number of leaves, and leaf area were significantly increased by 13.6%, 32.7%, 43.1%, 10.6%, and 32.8% respectively compared to CK, indicating that the elemental composition of the nutrient solution affected the growth of lettuce in this crop. In the fifth crop, the ECSSE treatment still maintained an advantage over CK, and its stem thickness, aboveground fresh weight, and underground fresh weight were significantly increased by 19.1%, 29.3%, and 36.7% respectively compared to CK.

[0129] Table 6 Effects of Different Supplementation Methods on Root Morphological Indexes of Lettuce in Each Crop

[0130]

[0131]

[0132] Note: Different lowercase letters after the data in the same column indicate significant differences at the 5% level.

[0133] The root growth of lettuce in the second to fifth crops is as Figure 5As shown in Table 6, with the increase of the number of cultivation crops, the root growth of CK gradually became inferior to that of ECSSE treatment. In the second crop of lettuce, the total root length, root surface area, root volume and branch number of CK were better than those of ECSSE treatment, with significant increases of 14.2%, 14.0%, 13.7% and 21.0% respectively. However, in the fourth crop, the ECSSE treatment surpassed it, and its root surface area, root volume and branch number were significantly increased by 27.9%, 38.2% and 30.3% respectively compared with CK. In the fifth crop, the total root length and branch number of ECSSE treatment were significantly increased by 15.0% and 29.8% respectively compared with CK. This change shows that in multiple crop cultivation, ECSSE treatment has greater potential to promote plant root growth.

[0134] In summary, although there are still deviations in the ECSSE treatment and it is impossible to achieve complete supplementation of nutrient elements, overall, the concentrations of various elements in the ECSSE treatment are closer to SC than those in CK. More importantly, the element composition during the recycling of the nutrient solution is more suitable for lettuce growth.

[0135] Beneficial effects of the present invention:

[0136] 1. Once the cultivation environment and operation procedures are fixed, it is only necessary to test the content of each element in the newly prepared nutrient solution and the nutrient solution at the end of the first cultivation, and to determine the supplementary solution suitable for multiple cultivations, so as to achieve a good nutrient solution element correction effect. During this period, there is no need to perform element detection again, which reduces the cost of element correction and extends the service life of the nutrient solution during the recycling of the nutrient solution.

[0137] 2. Although this method still has deviations and cannot achieve complete replenishment of consumed nutrients, overall, the concentration of each element is closer to the average concentration of the newly prepared nutrient solution than the control group, especially the replenishment of macroelements calcium, magnesium and sulfur and trace element manganese.

[0138] 3. The element composition during the nutrient solution recycling process using this method is more suitable for lettuce growth. Starting from the fourth crop, the growth of lettuce treated with ECSSE showed significant differences from the control group that only adjusted EC. Its stem diameter, aboveground fresh weight, underground fresh weight, leaf number and leaf area were significantly increased by 13.6%, 32.7%, 41.2%, 10.2% and 32.8% respectively compared with the control group; the root surface area, root volume and branch number were significantly increased by 27.9%, 38.2% and 30.3% respectively compared with the control group. By the fifth crop, the ECSSE treatment still maintained its advantage over the control group. Its stem diameter, aboveground fresh weight and underground fresh weight were significantly increased by 19.1%, 29.3% and 36.7% respectively compared with the control group; the total root length and branch number were significantly increased by 15.0% and 29.8% respectively compared with the control group.

[0139] The above has described the present invention in detail. For those skilled in the art, without departing from the gist and scope of the present invention and without the need for unnecessary experiments, the present invention can be implemented within a relatively wide range under equivalent parameters, concentrations, and conditions. Although specific embodiments of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application intends to cover any modifications, uses, or improvements to the present invention, including those that depart from the scope disclosed in this application but are made using conventional techniques known in the art. Some basic features can be applied according to the scope of the appended claims below.

Claims

1. A method for correcting nutrient solution elements, characterized in that, The method includes the step of adding a steady-state environmental element correction solution to the remaining nutrient solution after each crop has completed a specific growth stage of the plant during the process of multi-crop hydroponic cultivation of plants in a stable environment condition of a plant factory, and then proceeding to the next growth stage of the next crop of plants; The steady-state environmental element correction solution is a solution for supplementing the consumption of elements in the nutrient solution after cultivating the plant in a single crop with the initial nutrient solution under the stable environmental condition.

2. The method according to claim 1, wherein The preparation method of the steady-state environmental element correction solution specifically includes steps A1, A2, and A3: A1. Detect the concentration and volume of each element in the initial nutrient solution under the stable environmental condition, and detect the concentration and volume of each element in the remaining nutrient solution after cultivating the plant in a single crop to complete the growth stage. Calculate the consumption of each element using formula 1: n = C1V1 - C2V21 In the formula, n is the consumption of a certain element in the nutrient solution; C1 is the concentration of the element in the initial nutrient solution; V1 is the volume of the initial nutrient solution at the start of single-crop cultivation; C2 is the concentration of the element in the remaining nutrient solution after completing the growth stage in a single crop; V2 is the volume of the remaining nutrient solution after completing the growth stage in a single crop; A2. Preset the EC of the steady-state environmental element correction solution according to formula 2: where ECs is the EC of the preset steady-state environmental element calibration solution; EC o is the target EC after adding the steady-state environmental element calibration solution, the same as the EC of the initial nutrient solution; EC r is the EC of the remaining nutrient solution after completing the growth stage for a single crop; f is the percentage of the volume V2 of the remaining nutrient solution after completing the growth stage in a single crop to the total volume of the nutrient solution of the next crop; A3. Based on the calculation results of A1 and A2, design the components and dosages of the steady-state environmental element correction solution. At the same time, based on formula 3, with the goal of making the ECs reach or approach the EC of the steady-state environmental element correction solution preset in A2, adjust the dosages of each component to achieve that the element content and EC in the nutrient solution after supplementing the remaining nutrient solution to the volume of the initial nutrient solution are the same as or close to those of the initial nutrient solution, and complete the correction of the nutrient solution elements; In the formula, is the sum of the products of the concentrations and valences of the respective cations in the steady-state environmental element calibration solution.

3. The method according to claim 1 or 2, characterized in that, The plant is a vegetable, flower, or medicinal material suitable for hydroponic production.

4. The method according to claim 3, wherein The plant is a leafy vegetable.

5. The method according to claim 4, wherein The plant is lettuce, the stable environmental conditions are a temperature of 22 ± 0.5 °C, the light source is LED full-spectrum white light, the light-dark period is 16 h / 8 h, the canopy effective photosynthetic radiation is 200 μmol·m -2 ·s -1 , the relative humidity is (65 ± 10)%, the carbon dioxide concentration is 400 ± 50 μmol / mol, the initial nutrient solution is the modified Cornell lettuce nutrient solution, the growth stage is from 14 days of seedling age to harvest, the cultivation is deep flow nutrient solution cultivation for 18 days, then the formula of the steady-state environmental element correction solution is: 0.436 g / L KNO3, 0.784 g / L Ca(NO3)2·4H2O, 0.024 g / L (NH4)2SO4, 0.168 g / L (NH4)2HPO4, 0.179 g / L MgSO4·7H2O, 21.59 mg / L EDTA-NaFe, 6.47 mg / L MnSO4·H2O, 6.82 mg / L Na2B4O7·10H2O and 0.06 mg / L Na2MoO4·2H2O.

6. A method for preparing a steady-state environmental element calibration solution, characterized in that, It is to detect the consumption of nutrient solution elements of a plant in a single crop to complete a certain growth stage under stable environmental conditions, and to formulate a steady-state environmental element correction solution with the goal of supplementing this consumption, so that it can supplement the content of each element in the nutrient solution and the volume of the nutrient solution to reach or approach the initial state before cultivation. It specifically includes steps A1, A2, and A3: A1. Detect the concentration and volume of each element in the initial nutrient solution under the stable environmental condition, and detect the concentration and volume of each element in the remaining nutrient solution after cultivating the plant in a single crop to complete the growth stage. Calculate the consumption of each element using formula 1: n = C1V1 - C2V21 Where n is the consumption of a certain element in the nutrient solution; C1 is the concentration of the element in the initial nutrient solution; V1 is the volume of the initial nutrient solution at the start of single-crop cultivation; C2 is the concentration of the element in the remaining nutrient solution after the single crop has completed the growth stage 1 ; V2 is the volume of the remaining nutrient solution after the single crop has completed the growth stage; A2. Preset the EC of the steady-state environmental element correction solution according to formula 2: Wherein, EC o is the target EC after adding the steady-state environmental element correction liquid, which is the same as the EC of the initial nutrient solution; EC r is the EC of the remaining nutrient solution after completing the growth stage for a single crop; ECs is the EC of the preset steady-state environmental element correction liquid; f is the percentage of the volume V2 of the remaining nutrient solution after completing the growth stage in a single crop to the total volume of the nutrient solution of the next crop; A3. Based on the calculation results of A1 and A2, design the components and dosages of the steady-state environmental element correction solution. At the same time, based on Formula 3, with the goal of making the ECs reach or approach the EC of the steady-state environmental element correction solution preset in A2, adjust the dosages of each component to achieve that the element content, EC in the nutrient solution after supplementing the remaining nutrient solution to the initial nutrient solution volume with the steady-state environmental element correction solution are the same as or close to those in the initial nutrient solution, thus completing the correction of nutrient solution elements; In the formula, is the sum of the products of the concentrations of each cation in the steady-state environmental element calibration solution and their valences; The EC is calculated based on the concentrations of potassium, calcium, magnesium and ammonium nitrogen elements in the nutrient solution to represent K + , Ca 2+ , Mg 2+ and NH4 + cation concentrations.

7. A steady-state environmental element correction solution produced by the preparation method according to Claim 6.

8. The steady-state environmental element calibration solution according to claim 7, wherein It is a steady-state environmental element correction solution for the industrialized production of lettuce, and its formula is 0.436 g / L KNO3, 0.784 g / L Ca(NO3)2·4H2O, 0.024 g / L (NH4)2SO4, 0.168 g / L (NH4)2HPO4, 0.179 g / L MgSO4·7H2O, 21.59 mg / L EDTA-NaFe, 6.47 mg / L MnSO4·H2O, 6.82 mg / L Na2B4O7·10H2O, and 0.06 mg / L Na2MoO4·2H2O.

9. Application of the nutrient solution element correction method according to any one of Claims 1-5 or the preparation method of the steady-state environmental element correction solution according to Claim 6 in the industrialized production of plants.

10. Application of the steady-state environmental element correction solution according to Claim 8 in the industrialized production of lettuce.

Images