Leafy vegetable water culture organic nutrient solution and preparation method and application method thereof

Abstract

The application discloses a kind of leafy vegetables hydroponic organic nutrient solution and preparation method, application method, belong to organic fertilizer and microbial fertilizer manufacturing technical field, to solve at least one problem in the utilization rate and nutrient solution absorption rate reduction of the nutrient solution caused by nitrate accumulation, precipitation after long-term storage in the prior art.The nutrient solution composition of the application includes:KH2PO4 2.85~2.95, NH4H2PO3 2.78~2.88, MgSO4·7H2O 16.60~16.70, 5Ca (NO3) 2·NH4NO3·10H2O 29.00~29.25, KNO3 25.15~25.25, EDTA-Fe 20.67~0.69, H3BO3 0.08~0.12, MnSO4 0.05~0.10, ZnSO4·7H2O 0.005~0.01, CuSO4·7H2O 0.003~0.005, (NH4) 6MoO 24 ·4H2O 0.001~ 0.002 and water hot cleavage organic nutrient solution 22.0~23.0 by mass percentage.The application can be used for soilless culture of leafy crops.

Description

Technical Field

[0001] This invention belongs to the field of organic fertilizer and microbial fertilizer manufacturing technology, and particularly relates to a hydroponic organic nutrient solution for leafy vegetables and its preparation and application methods. Background Technology

[0002] Hydroponics, a modern agricultural technology that uses water as a nutrient medium and requires no natural soil or substrate, has been widely used in the large-scale production of leafy vegetables due to its advantages such as water conservation, labor saving, high yield, and no geographical limitations.

[0003] Currently, most nutrient solutions used in hydroponic production are entirely inorganic, such as the Japanese Garden Experiment General Formula. While these nutrient solutions are comprehensive in nutrients and have wide applicability, their nitrogen source primarily relies on nitrate nitrogen (NO3). - Studies have shown that if crops absorb large amounts of nitrate nitrogen but the rate of nitrate reduction and assimilation is insufficient, nitrates will accumulate in large quantities in edible parts such as leaves. Hydroponic vegetables grown using entirely inorganic nutrient solutions often suffer from poor taste and nutritional imbalances.

[0004] In recent years, the application of organic nutrient solutions in hydroponics has attracted attention. Organic nutrient solutions typically contain amino acids, organic acids, small-molecule active substances, and various trace elements, which not only provide nutrients to crops but also improve crop quality by regulating the rhizosphere microenvironment and chelating harmful substances. Sun Zhipeng et al. disclosed a method for using a hydrothermal pyrolysis-prepared organic nutrient solution combined with an inorganic nutrient solution for hydroponic lettuce cultivation. However, since both chelate A and chelate B solutions contain hydrothermal pyrolysis organic nutrient solution, precipitation occurs in both solutions after long-term storage, leading to a decrease in the utilization rate and absorption rate of the hydrothermal pyrolysis organic nutrient solution. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a hydroponic organic nutrient solution for leafy vegetables and its preparation and application methods, in order to solve at least one of the following problems in the prior art: nitrate accumulation, precipitation after long-term storage leading to reduced utilization and absorption rates of hydrothermal decomposition organic nutrient solutions, poor taste of cultivated products, and imbalance of nutrients.

[0006] The objective of this invention is mainly achieved through the following technical solutions: This invention provides a hydroponic organic nutrient solution for leafy vegetables, comprising, by mass percentage: KH₂PO₄ 2.85~2.95, NH₄H₂PO₃ 2.78~2.88, MgSO₄·7H₂O 16.60~16.70, 5Ca(NO₃)₂·NH₄NO₃·10H₂O 29.00~29.25, KNO₃ 25.15~25.25, EDTA-Fe 20.67~0.69, H₃BO₃ 0.08~0.12, MnSO₄ 0.05~0.10, ZnSO₄·7H₂O 0.005~0.01, CuSO₄·7H₂O 0.003~0.005, (NH₄)₆MoO₂ 24 • 4H2O 0.001~0.002 and hydrothermal pyrolysis organic nutrient solution 22.0~23.0.

[0007] Furthermore, during storage, the hydroponic organic nutrient solution for leafy vegetables is divided into solution A and solution B for separate storage. Solution A includes KH2PO4, NH4H2PO3, and MgSO4·7H2O; solution B includes 5Ca(NO3)2·NH4NO3·10H2O, KNO3, EDTA-Fe2, H3BO3, MnSO4, ZnSO4·7H2O, CuSO4·7H2O, and (NH4)6MoO. 24 • 4H2O and hydrothermal pyrolysis organic nutrient solution.

[0008] Furthermore, the composition of the hydrothermal pyrolysis organic nutrient solution, by mass percentage, includes 10.50~11.50% organic matter, 6.50~7.50% fulvic acid, 1.60~2.00% N, 0.85~0.95% P2O5, 2.03~2.43% K2O, 13.2~15.0% peptides and amino acid derivatives, 12.2~14.2% plant growth regulators, 5.5~7.5% organic acids and their derivatives, and 8.8~10.8% antibacterial substances. The mass-volume concentration is based on the volume of the hydrothermal pyrolysis organic nutrient solution.

[0009] Furthermore, the pH of the hydroponic organic nutrient solution for leafy vegetables is 5.8 to 6.5.

[0010] The present invention also provides a method for preparing a hydroponic organic nutrient solution for leafy vegetables, which is used for preparing a hydroponic organic nutrient solution for leafy vegetables.

[0011] Furthermore, the preparation method includes the following steps: Step 1: Weigh KH2PO4, NH4H2PO3 and MgSO4·7H2O and dissolve them in water. Heat and stir until all the solids are dissolved to obtain solution A. Step 2: Weigh out 5Ca(NO3)2·NH4NO3·10H2O, KNO3, EDTA-Fe2, H3BO3, MnSO4, ZnSO4·7H2O, CuSO4·7H2O, and (NH4)6MoO. 24 • Dissolve 4H2O and hydrothermal pyrolysis organic nutrient solution in water, heat and stir until all solids are dissolved to obtain solution B; Step 3: After cooling solutions A and B to room temperature, filter and sterilize them, then fill and seal them separately to obtain hydroponic organic nutrient solution for leafy vegetables.

[0012] Furthermore, in step 2, the hydrothermal pyrolysis organic nutrient solution is prepared by hydrothermal pyrolysis reaction of biomass as raw material at 150~250℃ and 1.0~2.5MPa.

[0013] Furthermore, in steps 1 and 2, the heating temperature is 75~85℃.

[0014] This invention also provides a method for applying hydroponic organic nutrient solution for leafy vegetables, using the above-mentioned hydroponic organic nutrient solution for leafy vegetable crops for soilless cultivation.

[0015] Furthermore, the application method includes the following steps: Step A: Dilute solution A and solution B of the hydroponic organic nutrient solution for leafy vegetables to obtain diluted solution A and diluted solution B respectively; Step B: Mix diluted solution A and diluted solution B thoroughly to obtain the working nutrient solution; Step C: Apply the working nutrient solution to leafy vegetables.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: A) The hydroponic organic nutrient solution for leafy vegetables provided by this invention is a novel nutrient solution made by compounding inorganic mineral nutrients with small molecule organic nutrient solutions rich in various stress-resistant plant stimulants, organic acids and amino acids. It combines the rapid and high-yield characteristics of inorganic nutrients with the rich and long-lasting functions of organic substances, effectively making up for the shortcomings of pure inorganic nutrient solutions.

[0017] B) The hydroponic organic nutrient solution for leafy vegetables provided by this invention replaces calcium nitrate with ammonium calcium nitrate, which ensures the absorption of nitrate nitrogen by hydroponic leafy vegetables, promotes the absorption of ammonium nitrogen, reduces the amount of nitrate input, and thus reduces the nitrate content in vegetables.

[0018] C) The hydroponic organic nutrient solution for leafy vegetables provided by this invention, for solution A, is a purely inorganic nutrient solution, therefore, it will basically not produce precipitation during long-term storage. For solution B, it is an organic-inorganic nutrient solution, and it will also basically not produce precipitation during long-term storage. This is because, although solution B is an organic-inorganic mixture, firstly, because the formula completely isolates all phosphate sources (KH2PO4, NH4H2PO3) in solution A, solution B, although containing high concentrations of calcium, iron, and other metal ions, has no phosphate, thus preventing phosphate precipitation; secondly, the EDTA-Fe in solution B... 2+ As a powerful chelating agent, it can stably encapsulate trace metal ions such as iron, manganese, zinc, and copper, mitigating their hydrolysis or the formation of slightly soluble substances with sulfate ions. Furthermore, the hydrothermal pyrolysis organic nutrient solution is rich in small-molecule organic acids and amino acids, which not only hinder the contact between calcium ions and sulfate ions through steric hindrance but also maintain the system's pH in a weakly acidic environment, increasing the solubility of salts. The extremely low concentration of sulfate ions among the trace elements is far below the critical solubility product of calcium sulfate. Therefore, through the combined effects of physical isolation, chemical chelation, and organic protection, solution B maintains a highly stable solution state during storage, with virtually no precipitation.

[0019] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0021] Figure 1 This is a bar chart showing the effect of different concentrations of hydroponic solution on the vitamin C and nitrate content of lettuce in Example 1. Figure 2 These are growth diagrams of butter lettuce from different embodiments and comparative examples in Example 1. Figure 3 These are growth diagrams of water spinach in different embodiments and comparative examples in Example 2 of this embodiment; Figure 4 This is a diagram of the root system of water spinach in different embodiments and comparative examples in Example 2. Detailed Implementation

[0022] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0023] In a first aspect, the present invention provides a hydroponic organic nutrient solution for leafy vegetables, the composition of which, by mass percentage, includes: KH₂PO₄ 2.85~2.95, NH₄H₂PO₃ 2.78~2.88, MgSO₄·7H₂O 16.60~16.70, 5Ca(NO₃)₂·NH₄NO₃·10H₂O 29.00~29.25, KNO₃ 25.15~25.25, EDTA-Fe 20.67~0.69, H₃BO₃ 0.08~0.12, MnSO₄ 0.05~0.10, ZnSO₄·7H₂O 0.005~0.01, CuSO₄·7H₂O 0.003~0.005, (NH₄)₆MoO₂ 24 The organic nutrient solution for leafy vegetables contains 0.001~0.002g of 4H2O and 22.0~23.0g of hydrothermal pyrolysis organic nutrient solution. During storage, the hydroponic organic nutrient solution for leafy vegetables is divided into solution A and solution B and stored separately. Solution A includes KH2PO4, NH4H2PO3 and MgSO4·7H2O; solution B includes 5Ca(NO3)2·NH4NO3·10H2O, KNO3, EDTA-Fe2, H3BO3, MnSO4, ZnSO4·7H2O, CuSO4·7H2O and (NH4)6MoO. 24 • 4H2O and hydrothermal pyrolysis organic nutrient solution.

[0024] Compared with the prior art, the hydroponic organic nutrient solution for leafy vegetables provided by the present invention, on the one hand, is a novel nutrient solution made by combining inorganic mineral nutrients with small molecule organic nutrient solutions rich in various stress-resistant plant stimulants, organic acids and amino acids. It takes into account the rapid and high-yield characteristics of inorganic nutrients and the rich and long-lasting functions of organic substances, effectively making up for the shortcomings of pure inorganic nutrient solutions.

[0025] On the other hand, currently, hydroponic leafy vegetables typically have a high absorption rate of nitrate nitrogen but cannot effectively absorb ammonium nitrogen. This invention replaces calcium nitrate with ammonium calcium nitrate, which ensures the absorption of nitrate nitrogen by hydroponic leafy vegetables while also promoting the absorption of ammonium nitrogen, reducing the amount of nitrate input, and thus reducing the nitrate content in vegetables.

[0026] Specifically, plants absorb ammonium nitrogen and nitrate nitrogen through different ion channels and transport protein mechanisms. The presence of appropriate amounts of ammonium nitrogen in the nutrient solution can not only directly induce the activity of ammonium nitrogen transport proteins in the roots, but also indirectly promote the kinetic parameters of nitrate nitrogen absorption (e.g., absorption rate) by altering the root cell membrane potential. When plants absorb different forms of nitrogen, they secrete different ions extracellularly to maintain intracellular charge balance, thereby changing the rhizosphere pH. Among these, the absorption of nitrate nitrogen (NO3) is affected by these ions. - When OH is present, the root system will secrete OH. - or HCO3 - This leads to an increase in rhizosphere pH, hindering the absorption of ammonium nitrogen (NH4). + When ), the root system secretes H + This leads to a decrease in rhizosphere pH. It should be noted that hydroponic leafy vegetables absorb nitrate nitrogen faster in neutral or slightly alkaline environments, but absorb ammonium nitrogen even faster in slightly acidic environments. Therefore, calcium ammonium nitrate can provide two nitrogen sources at the same time, so that the absorption process of ammonium nitrogen actively lowers the rhizosphere pH, providing a favorable slightly acidic microenvironment for its own and other ammonium nitrogen to be continuously absorbed.

[0027] In addition, the absorption process of nitrate nitrogen itself can promote the absorption of cations such as calcium, magnesium, and potassium. The stability of calcium ions in the cytoplasm can inhibit the ammonium toxicity effect caused by high concentrations of ammonium nitrogen (e.g., cell membrane damage, potassium ion extravasation), thereby increasing the plant's tolerance threshold to ammonium nitrogen.

[0028] On the other hand, solution A is a simple inorganic nutrient solution, so it will basically not produce precipitation during long-term storage. Solution B, on the other hand, is an organic-inorganic nutrient solution, and it will also basically not produce precipitation during long-term storage. This is because, although solution B is a mixture of organic and inorganic solutions, firstly, because the formula completely isolates all phosphate sources (KH₂PO₄, NH₄H₂PO₃) in solution A, solution B, despite containing high concentrations of calcium, iron, and other metal ions, contains no phosphate, thus preventing phosphate precipitation; secondly, the EDTA-Fe in solution B... 2+ As a powerful chelating agent, it can stably encapsulate trace metal ions such as iron, manganese, zinc, and copper, mitigating their hydrolysis or the formation of slightly soluble substances with sulfate ions. Furthermore, the hydrothermal pyrolysis organic nutrient solution is rich in small-molecule organic acids and amino acids, which not only hinder the contact between calcium ions and sulfate ions through steric hindrance but also maintain the system's pH in a weakly acidic environment, increasing the solubility of salts. The extremely low concentration of sulfate ions among the trace elements is far below the critical solubility product of calcium sulfate. Therefore, through the combined effects of physical isolation, chemical chelation, and organic protection, solution B maintains a highly stable solution state during storage, with virtually no precipitation.

[0029] In practical applications, neither solution A nor solution B will precipitate after being stored for 14 days.

[0030] Furthermore, in order to further address the problem of insufficient utilization of hydrothermal pyrolysis organic nutrient solution, the hydrothermal pyrolysis organic nutrient solution is, by mass percentage, composed of 10.50-11.50% organic matter, 6.50-7.50% fulvic acid, 1.60-2.00% N, 0.85-0.95% P2O5, 2.03-2.43% K2O, 13.2-15.0% peptides and amino acid derivatives, 12.2-14.2% plant growth regulators, 5.5-7.5% organic acids and their derivatives, and 8.8-10.8% antibacterial substances. It should be noted that the mass-volume concentration of the above substances is based on the volume of the hydrothermal pyrolysis organic nutrient solution.

[0031] Furthermore, to promote nutrient absorption and improve the overall performance of the hydroponic organic nutrient solution for leafy vegetables, the pH of the aforementioned hydroponic organic nutrient solution for leafy vegetables is 5.8–6.5. This is because this pH range perfectly matches the microenvironmental requirements of hydroponic leafy vegetables for the absorption of different forms of nitrogen. It maintains suitable slightly acidic conditions for the absorption of ammonium nitrogen without excessively acidifying and inhibiting the absorption efficiency of nitrate nitrogen. At the same time, this pH range also allows the trace elements chelated by EDTA to remain stable, reducing the precipitation of metal ions and further improving the stability and bioavailability of the nutrient solution components.

[0032] Secondly, the present invention provides a method for preparing a hydroponic organic nutrient solution for leafy vegetables, which is used in the preparation of the hydroponic organic nutrient solution for leafy vegetables provided in the first aspect.

[0033] The preparation method includes the following steps: Step 1: Weigh KH2PO4, NH4H2PO3 and MgSO4·7H2O and dissolve them in water (e.g., deionized water). Heat and stir until all the solids are dissolved to obtain solution A. Step 2: Weigh out 5Ca(NO3)2·NH4NO3·10H2O, KNO3, EDTA-Fe2, H3BO3, MnSO4, ZnSO4·7H2O, CuSO4·7H2O, and (NH4)6MoO. 24 • 4H2O and hydrothermal pyrolysis organic nutrient solution are dissolved in water (e.g., deionized water), and heated and stirred until all the solids are dissolved to obtain solution B; Step 3: After cooling solutions A and B to room temperature, filter them through a microfiltration membrane (pore size 0.22μm) for sterilization, then fill and seal them separately to obtain hydroponic organic nutrient solution for leafy vegetables.

[0034] Compared with the prior art, the preparation method of the hydroponic organic nutrient solution for leafy vegetables provided by the present invention has basically the same beneficial effects as the hydroponic organic nutrient solution for leafy vegetables provided in the first aspect, and will not be described in detail here.

[0035] It should be noted that in step 2 above, the hydrothermal pyrolysis organic nutrient solution is prepared by hydrothermal pyrolysis reaction of biomass as raw material at 150~250℃ and 1.0~2.5MPa.

[0036] Furthermore, to address the issue of low raw material dissolution efficiency, the heating temperature in steps 1 and 2 is 75~85℃. This temperature range accelerates the dissolution rate of solid raw materials, reduces agglomeration and deposition, and prevents the decomposition and deactivation of small molecule active substances in the hydrothermal pyrolysis organic nutrient solution due to excessively high temperatures, thus balancing dissolution efficiency and the stability of active ingredients.

[0037] Thirdly, the present invention also provides a method for applying hydroponic organic nutrient solution for leafy vegetables, using the hydroponic organic nutrient solution for leafy vegetables provided in the first aspect for soilless cultivation of leafy vegetable crops.

[0038] The application method includes the following steps: Step A: Dilute solution A and solution B of the hydroponic organic nutrient solution for leafy vegetables to obtain diluted solution A and diluted solution B respectively; Step B: Mix diluted solution A and diluted solution B thoroughly to obtain the working nutrient solution; Step C: Apply the working nutrient solution to leafy vegetables.

[0039] Compared with the prior art, the beneficial effects of the application method of the hydroponic organic nutrient solution for leafy vegetables provided by the present invention are basically the same as those of the hydroponic organic nutrient solution for leafy vegetables provided in the first aspect, and will not be elaborated here.

[0040] Furthermore, in order to further address the issue of insufficient utilization of hydroponic organic nutrient solution for leafy vegetables, the concentration of the aforementioned hydroponic organic nutrient solution for leafy vegetables varies at different stages of the crop's growth. For example, the growth cycle of leafy vegetables is divided into early stage (7-10 days), middle stage (7-10 days), and late stage (7-10 days). Based on this growth cycle, the application method includes the following steps: Step A: Perform initial dilution, intermediate dilution, and final dilution of solution A in the hydroponic organic nutrient solution for leafy vegetables to obtain solution A after initial dilution, solution A after intermediate dilution, and solution A after final dilution; Solution B of the hydroponic organic nutrient solution for leafy vegetables was diluted in the early stage, the middle stage, and the late stage to obtain solution B after the early stage dilution, solution B after the middle stage dilution, and solution B after the late stage dilution. It should be noted that the volume ratio of solution A to water gradually increases in solution A after initial dilution, solution A after intermediate dilution, and solution A after final dilution; similarly, the volume ratio of solution B to water gradually increases in solution B after initial dilution, solution B after intermediate dilution, and solution B after final dilution. Step B: Mix the previously diluted solution A and the previously diluted solution B thoroughly to obtain the initial nutrient solution; The intermediate-term diluted solution A and intermediate-term diluted solution B are mixed evenly to obtain the intermediate-term nutrient solution; The diluted solution A and diluted solution B are mixed evenly to obtain the nutrient solution for the later stage. Step C: Apply early-stage nutrient solution in the early growth stage of leafy vegetables; apply mid-stage nutrient solution in the middle growth stage of leafy vegetables; apply late-stage nutrient solution in the later growth stage of leafy vegetables.

[0041] In this way, on the one hand, adopting a phased, progressively increasing dilution concentration (lowest in the early stage, moderate in the middle stage, and higher in the later stage) can precisely match the dynamic nutrient requirements of leafy vegetables based on their S-shaped growth pattern. The low concentration in the early stage effectively alleviates root water loss and potassium deficiency caused by excessively high osmotic pressure. + / Na + The imbalanced inhibitory effect ensures that seedlings take root firmly; the moderate concentration in the middle stage provides a large amount of mineral elements needed for rapid nutrient growth; and the excessive accumulation of nitrate nitrogen in the leaves in the later stage can be effectively controlled. Through the concentration gradient, a precise supply is achieved to promote survival in the early stage, promote growth in the middle stage, and maintain quality in the later stage.

[0042] On the other hand, the low concentration environment in the early stage is conducive to the absorption of ammonium nitrogen, and the roots actively secrete H2. + The rhizosphere pH was finely adjusted to slightly acidic to create conditions for the subsequent activation of nitrate nitrogen uptake channels; during the intermediate concentration increase, the organic acids in the organic nutrient solution continuously complexed OH-. - This stabilizes the pH at 6.5±0.2, ensuring efficient absorption of cations such as calcium and magnesium. In the later stages, appropriate concentrations of organic acids can control the overexpression of nitrate transporter genes and reduce the passive transport of nitrate to leaves.

[0043] For example, after initial dilution, the volume ratio of solution A to water in solution A is 0.4~0.5:100, and the volume ratio of solution B to water in solution B is 0.4~0.5:100; after intermediate dilution, the volume ratio of solution A to water in solution A is 0.6~0.7:100, and the volume ratio of solution B to water in solution B is 0.6~0.7:100; after final dilution, the volume ratio of solution A to water in solution A is 0.7~0.8:100, and the volume ratio of solution B to water in solution B is 0.7~0.8:100.

[0044] Example 1 The lettuce variety used in this embodiment of the invention is butter lettuce, and the seeds were purchased commercially from the market; the hydroponic nutrient solution is a general formula for garden trials (standard formula of Okitsu Horticultural Experiment Station, Japan), which is a commercially available product; the hydrothermal pyrolysis organic nutrient solution (pH: 6.32, EC: 74.30 mS / cm, organic matter 50.10 g / L, total nitrogen, phosphorus and potassium 14.35 g / L) was prepared by Huanqing Agricultural Technology Co., Ltd. of Haiyang City, Yantai, Shandong Province.

[0045] This embodiment was carried out in a solar greenhouse from September 3 to October 1 of that year, with a light duration of 10 h·d. -1 The daytime and nighttime temperatures were 25℃ / 15℃, and the average daily relative humidity was 80%. A modular, soilless cultivation system was used for large-scale hydroponic cultivation of butter lettuce. The treatments were divided into three phases: 0-10 days (early stage), 11-19 days (mid-stage), and 20-28 days (late stage). Two implementation examples (Example 1-1 and Example 1-2) and one comparative example (Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3) were set up, as detailed in Table 1. Each treatment was repeated three times, with 16 plants per replicate.

[0046] The formula for hydroponic organic nutrient solution for leafy vegetables is as follows: Solution A: 8.5g KH2PO4, 8.3g NH4H2PO3, 49.3g MgSO4·7H2O and 1L deionized water, chelated at 80℃ until all solids are dissolved.

[0047] Liquid B: 5Ca(NO3)2·NH4NO3·10H2O 86.4g, KNO374.6g, EDTA-Fe22.0g, H3BO30.29g, MnSO40.21g, ZnSO4·7H2O 0.02g, CuSO4·7H2O 0.01g, (NH4)6MoO 24 • 0.002g of 4H2O, 66.67ml of hydrothermal pyrolysis organic nutrient solution, and 1L of deionized water were chelated at 80℃ until the solid was completely dissolved.

[0048] Butter lettuce seedlings with three true leaves and uniform growth vigor were selected and transplanted individually into separate nutrient solution tanks, ensuring that each tank could only support one plant. Each treatment group maintained a nutrient solution volume of 50L at different growth stages, with the solution being replaced every 10 days. The pH and conductivity (EC) of the solution were monitored daily, maintaining the pH stably within the range of 6.5 ± 0.2 to ensure the bioavailability of key elements such as iron and phosphorus. Intermittent aeration was applied twice daily, once in the morning and once in the evening, for one hour each time, to alleviate root hypoxia stress.

[0049] Table 1. Experimental Treatments for Hydroponic Lettuce

[0050] In the hydroponic lettuce experiment, on days 14, 21, and 28 after transplanting, 10 plants with synchronized growth and uniform phenotype were randomly selected from each example and comparative example. Their plant height (height of the above-ground part in its natural extended state), root length (natural extension length of the taproot), stem diameter (stem diameter near the base), leaf width (lateral distance at the widest point of the leaf), leaf length (longitudinal distance from the leaf tip to the base of the petiole), and total number of leaves were measured. See Table 2 and... Figure 2 .

[0051] The determination and calculation of aboveground / belowground dry and fresh weights were performed according to the method of Zhang Qinghang et al. The conductivity of the hydroponic solution was measured using a conductivity meter (Leici DDS-307A). The relative chlorophyll content (SPAD value) and nitrogen content were determined using a handheld chlorophyll meter (SPAD-502 chlorophyll meter, manufactured by Deens Instruments Technology Co., Ltd.). Vitamin C content was determined using the 2,6-dichlorophenolindophenol titration method. Nitrate content was determined using the salicylic acid-sulfuric acid colorimetric method. The test results are shown in Table 3.

[0052] Table 2. Effects of different application methods of hydroponic solution on lettuce growth at 14, 21, and 28 days after transplanting.

[0053] Note: Different lowercase letters in the same column indicate significant differences (ρ < 0.05) between different treatments at the same time after transplanting, and the same applies below.

[0054] Table 3. Effects of different treatments at 14, 21, and 28 days after transplanting on SPAD and nitrogen content in lettuce.

[0055] As shown in Table 2, the effects of different application methods of hydroponic solution on the growth of lettuce were different at 14 days, 21 days and 28 days after transplanting.

[0056] Table 3 shows that different concentrations of hydroponic solution had different effects on SPAD and nitrogen content in lettuce leaves at 14, 21, and 28 days after transplanting. At 14 days of growth, the SPAD values ​​of treatments T1-1, T1-2, and CK-1 were significantly higher than those of treatments T1-3 and T1-4, with treatment T1-1 showing the highest SPAD value at 17.51. There were no significant differences in nitrogen content among the various examples and comparative examples. At 21 days of growth, both SPAD and nitrogen content increased in all examples and comparative examples, with no significant differences between them. At 28 days of growth, treatment T1-2 showed the highest SPAD and nitrogen content, with increases of 10.81% and 16.12% respectively compared to treatment CK-1.

[0057] The effects of different concentrations of hydroponic nutrient solution on the biomass of individual lettuce plants vary (see Table 4). Table 4 shows that different concentrations of hydroponic nutrient solution have different effects on the biomass of individual lettuce plants. In terms of aboveground fresh weight, treatments T1-1 and T1-2 were significantly better than the other three control groups, increasing by 8.21g and 7.73g respectively compared to CK-1, representing increases of 12.07% and 11.37%. Treatments T1-3 and T1-4 had the smallest aboveground fresh weight, significantly lower than the other three control groups. In terms of underground fresh weight, treatments T1-1, T1-2, and CK-1 had 18.23g, 17.61g, and 18.94g respectively, significantly higher than treatments T1-3 and T1-4. Similar to fresh weight, aboveground and underground dry weights were better in treatments T1-1, T1-2, and CK-1 than in treatments T1-3 and T1-4.

[0058] Table 4. Effects of different concentrations of hydroponic solution on lettuce biomass.

[0059] See the table for vitamin C and nitrate content of lettuce at different concentrations. Figure 1 .from Figure 1 It can be seen that the vitamin C content of the T1-1 to T1-4 treatments was significantly higher than that of the CK-1 treatment, with an increase of 9.66% to 13.71%. Compared with the CK-1 treatment, the nitrate content of the T1-1 to T1-4 treatments was significantly reduced, with a decrease of 11.40% to 24.69%. The nitrate content of the T1-1 to T1-4 treatments was ranked as follows: T1-1 < T1-2 < T1-3 < T1-4.

[0060] Experiments showed that the biomass of lettuce at T1-3 and T1-4 concentrations was lower than that of the other three treatments throughout the entire growth cycle. The reason for this might be that in the early stages of growth, the EC value in the hydroponic nutrient solution was too high, and the osmotic pressure of the nutrient solution was higher than the concentration of the root cell sap. This caused water molecules in the root cell sap to permeate into the nutrient solution, resulting in osmotic dehydration of the root cells. Simultaneously, the potassium content in the root cells... ＋ / Na ＋ Imbalance leads to ion toxicity and nutrient absorption blockage, which in turn inhibits growth, slows growth, and results in low biomass.

[0061] The SPAD value of leaves, as a non-destructive monitoring indicator, characterizes the relative chlorophyll content in plant leaves. When chlorophyll concentration increases, the amount of light-harvesting pigment-protein complexes involved in light energy capture also increases, significantly enhancing the leaf's ability to absorb visible light, promoting organic matter synthesis, and achieving efficient accumulation of dry matter within the plant, thus providing a physiological basis for crop yield formation and quality optimization. In this experiment, the SPAD values ​​and nitrogen content of leaves treated with T1-1 and T1-2 at 14d, 21d, and 28d were significantly better than those treated with T1-3 and T1-4, indicating that their growth potential was superior to that of T1-3 and T1-4.

[0062] Economic analysis: The input costs for treatments T1-1, T1-2, T1-3, T1-4, and CK-1 are RMB 8.84, RMB 10.40, RMB 11.96, RMB 13.52, and RMB 20.50, respectively. Under the same yield conditions, the input costs for producing 1 kg of lettuce are RMB 5.85, RMB 6.96, RMB 10.19, RMB 11.52, and RMB 14.74, respectively.

[0063] In summary, T1-1 and T1-2 significantly optimize growth traits, increase yield and quality, and enhance economic benefits in the early, middle, and late stages of lettuce growth, demonstrating the best overall performance and making them the recommended nutrient solution formulas for large-scale lettuce production in plant factories.

[0064] Example 2 The water spinach variety used in this embodiment of the invention is three-forked water spinach, and the seeds were purchased commercially from the market; the hydroponic nutrient solution is a general formula for garden trials (standard formula of Okitsu Horticultural Experiment Station in Japan), which is a commercially available product; the hydrothermal pyrolysis organic nutrient solution (pH: 6.32, EC: 74.30 mS / cm, organic matter 50.10 g / L, total nitrogen, phosphorus and potassium 14.35 g / L) was prepared by Huanqing Agricultural Technology Co., Ltd. of Haiyang City, Yantai, Shandong Province.

[0065] This embodiment was carried out in a solar greenhouse from September 5th to October 4th of that year, with a light duration of 10 hours per day. -1 The daytime and nighttime temperatures were 25℃ / 15℃, and the average daily relative humidity was 80%. A modular, soilless cultivation system was used for large-scale hydroponic cultivation of butter lettuce. The treatments were divided into three phases: 0-10 days (early stage), 11-19 days (mid-stage), and 20-28 days (late stage). Two implementation examples (Example 2-1 and Example 2-2) and one comparative example (Comparative Example 2-1, Comparative Example 2-2, and Comparative Example 2-3) were set up, as detailed in Table 5. Each treatment was repeated three times, with 16 plants per replicate.

[0066] The formula for hydroponic organic nutrient solution for leafy vegetables is as follows: Solution A: 8.6g KH2PO4, 8.4g NH4H2PO3, 49.5g MgSO4·7H2O and 1L deionized water, chelated at 85℃ until all solids are dissolved.

[0067] Liquid B: 5Ca(NO3)2·NH4NO3·10H2O 86.5g, KNO374.7g, EDTA-Fe22.1g, H3BO30.30g, MnSO40.22g, ZnSO4·7H2O 0.02g, CuSO4·7H2O 0.02g, (NH4)6MoO 24 • 0.002g of 4H2O, 66.72ml of hydrothermal pyrolysis organic nutrient solution, and 1L of deionized water were chelated at 85℃ until the solid was completely dissolved.

[0068] Water spinach seedlings with four true leaves and uniform growth vigor were selected and transplanted individually into separate nutrient solution tanks, ensuring that each tank could only support one plant. Each treatment group maintained a nutrient solution volume of 50L at different growth stages, with the solution being changed every 10 days. The pH and conductivity (EC) of the solution were monitored daily, maintaining the pH stably within the range of 6.5±0.2 to ensure the bioavailability of key elements such as iron and phosphorus. Intermittent aeration was applied twice daily, once in the morning and once in the evening, for one hour each time, to alleviate root hypoxia stress.

[0069] Table 5. Experimental Treatments for Hydroponic Water Spinach

[0070] The effects of different treatments on the biological traits of hydroponically grown water spinach are shown in Table 6. Figure 3 and Figure 4 As shown, in terms of plant height, treatments T2-1, T2-2, T2-4, and CK-2 were all around 30 cm tall, with no significant differences. Regarding stem diameter, T2-1 was the thickest, with increases of 3.64%, 29.5%, 16.3%, and 7.55% compared to the other four treatments, respectively. In terms of root length, T2-1 was the longest, reaching 20.42 cm, while treatments T2-2 and CK-2 were both around 19 cm, with no significant differences.

[0071] Table 6 Effects of different treatments on the biological traits of water spinach

[0072] Note: Different lowercase letters in the same column indicate significant differences between different treatments after transplanting. ρ <0.05), the same applies below.

[0073] The effects of different concentrations on the yield of hydroponically grown water spinach are shown in Table 7. Harvesting was conducted three times: the first and second harvests were selective, and the third harvest was complete. The total fresh weight of water spinach was highest for T2-1 (1991.35g), followed by T2-2 (1834.89g). The fresh weight of T2-1 water spinach increased by 792.75g, 747.19g, and 199.36g compared to T2-3, T2-4, and CK-2, respectively.

[0074] Table 7. Effects of different treatments on water spinach yield

[0075] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydroponic organic nutrient solution for leafy vegetables, characterized in that, The composition, by mass percentage, includes: KH₂PO₄ 2.85~2.95, NH₄H₂PO₃ 2.78~2.88, MgSO₄·7H₂O 16.60~16.70, 5Ca(NO₃)₂·NH₄NO₃·10H₂O 29.00~29.25, KNO₃ 25.15~25.25, EDTA-Fe 20.67~0.69, H₃BO₃ 0.08~0.12, MnSO₄ 0.05~0.10, ZnSO₄·7H₂O 0.005~0.01, CuSO₄·7H₂O 0.003~0.005, (NH₄)₆MoO 24 • 4H2O 0.001~0.002 and hydrothermal pyrolysis organic nutrient solution 22.0~23.

0.

2. The hydroponic organic nutrient solution for leafy vegetables according to claim 1, characterized in that, During storage, the hydroponic organic nutrient solution for leafy vegetables is divided into solution A and solution B and stored separately. Solution A includes KH2PO4, NH4H2PO3, and MgSO4·7H2O; solution B includes 5Ca(NO3)2·NH4NO3·10H2O, KNO3, EDTA-Fe2, H3BO3, MnSO4, ZnSO4·7H2O, CuSO4·7H2O, and (NH4)6MoO. 24 • 4H2O and hydrothermal pyrolysis organic nutrient solution.

3. The hydroponic organic nutrient solution for leafy vegetables according to claim 1, characterized in that, The composition of the hydrothermal pyrolysis organic nutrient solution, by mass percentage, includes 10.50-11.50% organic matter, 6.50-7.50% fulvic acid, 1.60-2.00% N, 0.85-0.95% P2O5, 2.03-2.43% K2O, 13.2-15.0% peptides and amino acid derivatives, 12.2-14.2% plant growth regulators, 5.5-7.5% organic acids and their derivatives, and 8.8-10.8% antibacterial substances. The mass-volume concentration is based on the volume of the hydrothermal pyrolysis organic nutrient solution.

4. The hydroponic organic nutrient solution for leafy vegetables according to claim 1, characterized in that, The pH of the organic nutrient solution for hydroponic leafy vegetables is 5.8-6.

5.

5. A method for preparing a hydroponic organic nutrient solution for leafy vegetables, characterized in that, Used for the preparation of hydroponic organic nutrient solution for leafy vegetables as described in any one of claims 1 to 4.

6. The method for preparing hydroponic organic nutrient solution for leafy vegetables according to claim 5, characterized in that, The preparation method includes the following steps: Step 1: Weigh KH2PO4, NH4H2PO3 and MgSO4·7H2O and dissolve them in water. Heat and stir until all the solids are dissolved to obtain solution A. Step 2: Weigh out 5Ca(NO3)2·NH4NO3·10H2O, KNO3, EDTA-Fe2, H3BO3, MnSO4, ZnSO4·7H2O, CuSO4·7H2O, and (NH4)6MoO. 24 • Dissolve 4H2O and hydrothermal pyrolysis organic nutrient solution in water, heat and stir until all solids are dissolved to obtain solution B; Step 3: After cooling solutions A and B to room temperature, filter and sterilize them, then fill and seal them separately to obtain hydroponic organic nutrient solution for leafy vegetables.

7. The method for preparing hydroponic organic nutrient solution for leafy vegetables according to claim 6, characterized in that, In step 2, the hydrothermal pyrolysis organic nutrient solution is prepared by hydrothermal pyrolysis reaction of biomass as raw material at 150~250℃ and 1.0~2.5MPa.

8. The method for preparing hydroponic organic nutrient solution for leafy vegetables according to claim 6, characterized in that, In steps 1 and 2, the heating temperature is 75~85℃.

9. A method for applying a hydroponic organic nutrient solution for leafy vegetables, characterized in that, Soilless cultivation of leafy vegetables is carried out using the hydroponic organic nutrient solution for leafy vegetables as described in any one of claims 1 to 4.

10. The method of applying the hydroponic organic nutrient solution for leafy vegetables according to claim 9, characterized in that, The application method includes the following steps: Step A: Dilute solution A and solution B of the hydroponic organic nutrient solution for leafy vegetables to obtain diluted solution A and diluted solution B respectively; Step B: Mix diluted solution A and diluted solution B thoroughly to obtain the working nutrient solution; Step C: Apply the working nutrient solution to leafy vegetables.

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