Preparation method of novel rare earth lanthanum fertilizer saline alkali soil conditioner

Abstract

The invention discloses a preparation method of a novel rare earth lanthanum fertilizer saline alkali soil conditioner. The rare earth element lanthanum nitrate is used as a rare earth source, glycine and humic acid are jointly used as a chelating agent, the absorption and utilization rate of the lanthanum element is synergistically improved, and a synergistic interaction effect is achieved in the aspects of enhancing plant salt stress resistance and the like; the diammonium hydrogen phosphate and the mineral source potassium fulvate are compounded and introduced into K < + > and the like to act together, so that the conductivity of the soil can be reduced, the water-retaining property is good, drought stress is effectively relieved, the fertility and the productivity of the soil are improved, and the saline-alkali soil conditioner has important significance on improvement and utilization of the saline-alkali soil.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural soil improvement, and in particular to a method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil improver. Background Art

[0002] Lanthanum is a rare earth element with unique chemical properties and biological activities. Lanthanum fertilizers can promote plant growth, enhance photosynthesis efficiency and root development, and strengthen plant resistance to stresses such as drought and salinity. Furthermore, they can promote the proliferation of beneficial microorganisms in the soil, improve the soil microecological environment, and enhance soil fertility. Under conditions of nutrient deficiency, applying lanthanum-containing fertilizers can alter plant root structure, enhance root hydraulic conductivity, and increase root ATPase activity, thereby improving photosynthesis and gas exchange. This allows plants to mitigate the adverse effects of phosphorus deficiency and better absorb nutrients. These effects may be related to lanthanum's ability to reduce oxidative stress and enhance antioxidant enzyme activity in plants. Research has found that rare earth elements are physiologically active chemical elements that can influence plant morphology and growth. Appropriate use of rare earth elements can enhance crop photosynthesis, promote nutrient absorption, and improve plant resistance to environmental stress, thereby significantly increasing crop yields.

[0003] Saline-alkali soil refers to soil with a high salt content and a pH of 8.5 or higher. Saline-alkali soil is found in over 30 countries worldwide, covering 1.381 billion hectares, or 10.7% of the world's total land area. Furthermore, approximately 10% of irrigated farmland and 10% of rain-fed farmland are affected by salinization. In my country, saline-alkali wasteland and saline-alkali land affecting arable land total over 500 million mu (approximately 166 acres). Saline-alkali soils typically have a compact physical structure, with extremely poor aeration and water permeability. This results in reduced porosity and oxygen depletion, significantly inhibiting the growth and development of plant roots. High salinity and alkalinity also interfere with plant nutrient absorption, reduce soil microbial activity, and ultimately weaken soil fertility and ecological functions. This type of soil poses a significant challenge to agricultural production. Therefore, improving and rationally utilizing saline-alkali soils is of paramount importance.

[0004] Sodium in saline-alkali soils can cause multiple hazards, including impairing water absorption. Plant roots absorb water from the soil primarily through osmosis. In saline-alkali soils, excessive sodium ion concentrations increase the osmotic pressure of the soil solution. When the osmotic pressure of the soil solution exceeds that of the plant cell sap, plant roots are unable to absorb water from the soil normally and instead lose water. For example, when the osmotic pressure of the soil solution reaches a certain level, the root cells experience plasmolysis, similar to that seen in high-concentration salt solutions. This causes leaf wilt and growth inhibition. It also affects root development. The presence of sodium ions alters the physical properties of the soil, degrading its structure. Saline-alkali soils are often compact and poorly aerated. Plant roots growing in these environments experience mechanical resistance, resulting in poor root development. This inhibited root growth further reduces the plant's ability to absorb water and nutrients, creating a vicious cycle. Furthermore, high concentrations of sodium ions in the soil can directly toxic root cells, inhibiting their division and elongation. This can lead to short, thin roots and sparse root hairs, severely impacting plants' access to nutrients. In my country's saline-alkali soil improvement efforts, excessive use of soil amendments can lead to the accumulation of rare earth elements (REEs), negatively impacting soil microbial communities and enzyme activity, ultimately affecting the balance of the entire ecosystem.

[0005] Based on this, the present invention provides a preparation method of a novel rare earth lanthanum fertilizer saline-alkali soil conditioner, which compounds rare earth elements with other chemical conditioners (such as amino acids, humic acid, etc.) to improve the improvement effect, allowing lanthanum ions to exchange with sodium ions in the soil, etc., thereby improving the physical properties of the soil and providing a new and effective way to improve saline-alkali soil. Summary of the Invention

[0006] The present invention provides a method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner. In view of the many problems existing in existing saline-alkali soil conditioners, the present invention improves the improvement effect by combining rare earth element lanthanum nitrate with other chemical chelating agents and auxiliary raw materials. Specifically, by selectively selecting glycine and humic acid as chelating agents, the absorption and utilization rate of lanthanum element is synergistically improved, which has a synergistic effect in enhancing plant resistance to salt stress. The compounding of diammonium hydrogen phosphate and mineral source potassium fulvate introduces K + etc., working together, can reduce the electrical conductivity of the soil, have good water retention, effectively alleviate drought stress, improve soil fertility and productivity, and are of great significance to the improvement and utilization of saline-alkali land.

[0007] One aspect of the present invention provides a method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner, the preparation method comprising the following steps: S1. Raw material preparation: Select rare earth lanthanum source, chelating agent, auxiliary raw materials and deionized water; According to the mass ratio, the rare earth lanthanum source is 3-8 parts of lanthanum nitrate; The chelating agents are humic acid and glycine, with 15-25 parts of humic acid and 8-16 parts of glycine; The auxiliary raw materials are diammonium hydrogen phosphate and mineral-source potassium fulvate, wherein diammonium hydrogen phosphate is 1-3 parts and mineral-source potassium fulvate is 7-13 parts; Deionized water is 800-1200 parts; S2. Thoroughly mix lanthanum nitrate and glycine, add half of deionized water, and stir on a magnetic stirrer to dissolve, to obtain Liquid A; S3. Thoroughly mix the humic acid and mineral-derived potassium fulvate, add the remaining deionized water, and stir on a magnetic stirrer to dissolve, to obtain Liquid B; S4. Add diammonium hydrogen phosphate to liquid B, stir on a magnetic stirrer to dissolve it, and obtain liquid C; S5. Mix liquid A and liquid C together, place them on a magnetic stirrer and continue stirring and dissolving to obtain the novel rare earth lanthanum fertilizer saline-alkali soil conditioner.

[0008] Glycine is a natural amino acid with excellent chelating ability. Compared with other amino acids, it can form more stable chelates, preventing lanthanum precipitation and ineffectiveness while promoting transmembrane absorption. When compounded, since glycine itself is a precursor for the synthesis of important osmotic regulating substances such as proline and glutathione in plants, lanthanum can induce plants to enhance proline synthesis after compounding. At the same time, the directly provided glycine can also be quickly utilized by plants, significantly accelerating the activation of plant systems, and showing good synergistic effects in enhancing plant resistance to salt stress, promoting photosynthesis, and improving nutrient absorption.

[0009] Humic acid is a natural organic macromolecule with complex functional groups. The combined action of multiple functional groups has a better chelating effect. It is a natural binder that can improve water permeability and air permeability and improve soil compaction and hardening. In addition, it can activate plant antioxidant enzymes and strengthen co-oxidation capacity to jointly improve the absorption rate of N, P, K and various trace elements in the soil.

[0010] As a preferred solution, the raw material dosage is 6 parts of lanthanum nitrate, 20 parts of humic acid, 12 parts of glycine, 2 parts of diammonium hydrogen phosphate, 10 parts of mineral potassium fulvate, and 1000 parts of deionized water in terms of mass ratio.

[0011] As a preferred solution, the stirring in step S2 is 10-20 minutes, the stirring in step S3 is 2-4 hours, and the stirring in steps S4 and S5 is 20-40 minutes respectively.

[0012] As a preferred solution, the method also includes S6, which tests the performance indicators of the rare earth lanthanum fertilizer saline-alkali soil conditioner obtained in S5, including the effects on plant germination rate and roots, stems and leaves, pH, salt content, chlorophyll, sodium content, chromium, mercury, aluminum, nickel ion testing and soil morphology analysis.

[0013] The second aspect of the present invention also provides a rare earth lanthanum fertilizer saline-alkali soil conditioner prepared by a method for preparing the rare earth lanthanum fertilizer saline-alkali soil conditioner.

[0014] The third aspect of the present invention provides a use of a rare earth lanthanum fertilizer saline-alkali soil conditioner in improving saline-alkali soil for alfalfa plants.

[0015] As a preferred solution, the application is to improve the saline-alkali soil for cultivating alfalfa plants, and the improver is applied to the soil once every 3 days.

[0016] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: (1) The present invention provides a method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner. In view of the many problems existing in existing saline-alkali soil conditioners, the improvement effect is improved by combining the rare earth element lanthanum nitrate with other chemical chelating agents and auxiliary raw materials. Specifically, through ion exchange, sodium ions in the soil are replaced, reducing their damage to the soil structure. Lanthanum can also promote the leaching of salt in the soil, reduce the salt content of the soil, and significantly reduce the electrical conductivity of the soil. The lanthanum nitrate compound fertilizer saline-alkali soil conditioner has good water retention, effectively alleviates drought stress, and improves soil fertility and productivity. The process is simple and has important significance for the improvement and utilization of saline-alkali land.

[0017] (2) The present invention selects lanthanum nitrate as a rare earth source, which can promote the formation of soil aggregates and improve the common problems of saline-alkali soil such as compaction and poor air permeability. Moreover, the use of lanthanum nitrate as a rare earth source is acidic. On the one hand, it can neutralize the alkalinity in saline-alkali soil during use. On the other hand, it can also stimulate plant roots to secrete organic acid substances including citric acid and oxalic acid, further neutralize alkaline substances, and achieve the effect of effectively lowering pH. Moreover, it can be used to replace sodium ions (Na + ) to improve soil structure and reduce soil salinization.

[0018] Rare earth lanthanum ions (La 3+ ) and the sodium ions in the soil (Na + ) for exchange. Since the lanthanum ion has a charge of +3 and the sodium ion has a charge of +1, three sodium ions are required to exchange for one lanthanum ion. This process effectively reduces the sodium ion concentration in the soil, thereby reducing the adverse effects of sodium ions on plant growth and soil structure.

[0019] (3) In the selection of chelating agents, the present invention specifically selects glycine and humic acid as chelating agents to synergistically enhance the efficacy. Both glycine and humic acid can react with lanthanum nitrate to exert their efficacy. After the combination, the small molecule glycine is easily absorbed and can achieve amino-carboxyl chelation to form a neutral chelate. The humic acid macromolecule exerts a sustained release effect. The multifunctional groups form a strong and stable network chelation. The small molecule amino acid glycine is combined with the large molecule organic matter humic acid to jointly exert a short-term rapid supplement and long-term complementary mechanism of long-term supply, thereby reducing the risk of lanthanum loss. In terms of soil improvement, glycine can promote the secretion of organic acids by the root system and neutralize alkalinity; while humic acid can achieve the overall adsorption of sodium ions and improve the structure of the plow layer. The two also have a better effect on soil improvement. Therefore, the combined effect of glycine and humic acid is better.

[0020] (4) In the compounding of raw materials, auxiliary raw materials are further added. For example, diammonium hydrogen phosphate can provide nitrogen and phosphorus nutrients, and mineral potassium fulvate can provide organic potassium and humic acid. Fulvic acid can strongly complex lanthanum through carboxyl and phenolic hydroxyl groups, reduce the fixation of phosphorus, and prevent precipitation caused by phosphate ions and lanthanum. After compounding, it can protect the efficacy of lanthanum and phosphorus. The nutrients contain rich nitrogen, phosphorus, and potassium, which enhance the application efficacy of the above nutrients. Fulvic acid can also absorb free sodium in the soil and lanthanum nitrate to reduce the ion poisoning suffered by plant roots.

[0021] (5) The novel rare earth lanthanum fertilizer saline-alkali soil conditioner provided by the present invention has a good use effect. Experimental studies have shown that the rare earth lanthanum fertilizer soil conditioner prepared by the present invention has a germination rate of up to 97%, can promote the growth of plant rhizomes, and increase the length of roots and leaves; can effectively reduce pH and conductivity, and the sodium content in saline-alkali soil is reduced to 0.336 mg / kg; heavy metal chromium and mercury are reduced to below the instrument precision, nickel content is reduced to 10.292 mg / kg, and aluminum content is reduced to 20.525 mg / kg. It can effectively improve soil morphology and soil pore structure. Compared with unimproved soil, the pore volume is larger at the same pore width, and the soil specific surface area can be increased. The raw material compatibility of the rare earth lanthanum fertilizer saline-alkali soil conditioner is reasonable, and it has good prospects for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a graph of the root, stem and leaf length and germination rate of plants grown with different ingredients of improvers.

[0023] Figure 2 This is a graph showing the changes in soil pH and electrical conductivity after soil amendments with different components are used.

[0024] Figure 3 These are pictures of plants grown with different components of improvers (top view on the left, main view on the right).

[0025] Figure 4 This is a graph showing the changes in germination rate and leaf area of ​​plants grown with modifiers of different ingredients.

[0026] Figure 5 This is a graph showing changes in chlorophyll content in plants grown with different ingredients of modifiers.

[0027] Figure 6 This is a graph showing changes in soil pH and salinity after soil amendments of different composition are applied.

[0028] Figure 7 This is a graph showing changes in sodium content in soils improved with amendments of different compositions.

[0029] Figure 8 This is a graph showing the heavy metal content in soil improved by amendments of different compositions.

[0030] Figure 9 This is a diagram of the unamended soil sampling structure.

[0031] Figure 10 This is a diagram of the sampling structure of the upper soil after improvement with rare earth lanthanum nitrate compound fertilizer improver.

[0032] Figure 11 This is a diagram of the sampling structure of the lower soil after improvement with rare earth lanthanum nitrate compound fertilizer improver.

[0033] Figure 12 This is a comparison chart of the specific surface area of ​​unimproved and improved soil. DETAILED DESCRIPTION

[0034] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0035] The present invention may also be implemented or applied through different specific embodiments, and the details in this specification may also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other in the absence of conflict. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods; the materials and reagents used are all commercially available materials and reagents unless otherwise specified.

[0037] Example 1 A method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner, the method comprising the following steps: S1. Raw material preparation: Select rare earth lanthanum source, chelating agent, auxiliary raw materials and deionized water; The rare earth lanthanum source is 0.6g of lanthanum nitrate; The chelating agents are humic acid and glycine, 2g humic acid and 1.2g glycine; The auxiliary raw materials are diammonium hydrogen phosphate and mineral-source potassium fulvic acid, including 0.2g diammonium hydrogen phosphate and 1g mineral-source potassium fulvic acid; Deionized water is 100ml; S2. Thoroughly mix lanthanum nitrate and glycine, add half of the deionized water, and stir on a magnetic stirrer for 15 minutes to dissolve them, to obtain Liquid A; S3. Thoroughly mix the humic acid and mineral-derived potassium fulvate, add the remaining deionized water, and stir on a magnetic stirrer for 3 hours to dissolve them, to obtain Liquid B; S4. Add diammonium hydrogen phosphate to Liquid B, stir on a magnetic stirrer for 30 minutes to dissolve it, and obtain Liquid C; S5. Mix liquid A and liquid C together, place them on a magnetic stirrer and continue stirring for 30 minutes to dissolve them, to obtain the novel rare earth lanthanum fertilizer saline-alkali soil conditioner.

[0038] Example 2 A method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner, the method comprising the following steps: S1. Raw material preparation: Select rare earth lanthanum source, chelating agent, auxiliary raw materials and deionized water; The rare earth lanthanum source is 0.8g of lanthanum nitrate; The chelating agents are humic acid and glycine, 2.5g humic acid and 1.6g glycine; The auxiliary raw materials are diammonium hydrogen phosphate and mineral-source potassium fulvic acid, including 0.3g diammonium hydrogen phosphate and 1.3g mineral-source potassium fulvic acid; Deionized water is 120ml; S2. Thoroughly mix lanthanum nitrate and glycine, add half of the deionized water, and stir on a magnetic stirrer for 15 minutes to dissolve them, to obtain Liquid A; S3. Thoroughly mix the humic acid and mineral-derived potassium fulvate, add the remaining deionized water, and stir on a magnetic stirrer for 3 hours to dissolve them, to obtain Liquid B; S4. Add diammonium hydrogen phosphate to Liquid B, stir on a magnetic stirrer for 30 minutes to dissolve it, and obtain Liquid C; S5. Mix liquid A and liquid C together, place them on a magnetic stirrer and continue stirring for 30 minutes to dissolve them, to obtain the novel rare earth lanthanum fertilizer saline-alkali soil conditioner.

[0039] Example 3 A method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner, the method comprising the following steps: S1. Raw material preparation: Select rare earth lanthanum source, chelating agent, auxiliary raw materials and deionized water; The rare earth lanthanum source is 0.3g of lanthanum nitrate; The chelating agents are humic acid and glycine, 1.5 g humic acid and 0.8 g glycine; The auxiliary raw materials are diammonium hydrogen phosphate and mineral-source potassium fulvic acid, including 0.1g diammonium hydrogen phosphate and 0.7g mineral-source potassium fulvic acid; Deionized water is 80ml; S2. Thoroughly mix lanthanum nitrate and glycine, add half of the deionized water, and stir on a magnetic stirrer for 15 minutes to dissolve them, to obtain Liquid A; S3. Thoroughly mix the humic acid and mineral-derived potassium fulvate, add the remaining deionized water, and stir on a magnetic stirrer for 3 hours to dissolve them, to obtain Liquid B; S4. Add diammonium hydrogen phosphate to Liquid B, stir on a magnetic stirrer for 30 minutes to dissolve it, and obtain Liquid C; S5. Mix liquid A and liquid C together, place them on a magnetic stirrer and continue stirring for 30 minutes to dissolve them, to obtain the novel rare earth lanthanum fertilizer saline-alkali soil conditioner.

[0040] Experimental example 1. Research Methods 1.1 Study on the performance of rare earth lanthanum composite amendment in hydroponic alfalfa plants.

[0041] (1) Water environment treatment: Pour water into the flower pot.

[0042] (2) Seed treatment: Select alfalfa seeds of uniform size and fullness, soak them in clean water for 12 hours to allow them to fully absorb water and swell, thereby increasing the germination rate.

[0043] (3) Sowing: Sprinkle the soaked alfalfa seeds evenly on the water surface grid of each flower pot, sowing the same amount in each pot so that the seeds are closely combined with the water surface, and then spray water with a watering can to keep the seeds moist.

[0044] (4) Fertilization treatment: Apply rare earth lanthanum nitrate composite improver as required.

[0045] 1.2 Testing of soil-cultured alfalfa plants using rare earth lanthanum compound amendment to improve saline-alkali soil.

[0046] (1) Soil treatment: Put saline-alkali soil into the flower pot.

[0047] (2) Seed treatment: Select alfalfa seeds of uniform size and fullness, soak them in clean water for 12 hours to allow them to fully absorb water and swell, thereby increasing the germination rate.

[0048] (3) Sowing: Sow the soaked alfalfa seeds evenly on the soil surface of each pot, sowing the same amount in each pot, and then cover with a thin layer of soil, about 0.5 cm thick. Gently compact the soil so that the seeds are tightly combined with the soil, and then spray water with a watering can to keep the soil moist.

[0049] (4) Fertilization treatment: Apply rare earth lanthanum nitrate composite improver as required.

[0050] 2. Treatment method Experiment 3.1-3.2 Treatment Groups Treatment 1: Plants without amendments Treatment 2: Plants with pure lanthanum nitrate amendment Treatment 3: Plants with lanthanum nitrate and glycine amendments Treatment 4: Plants treated with mineral-derived potassium fulvic acid, humic acid, and diammonium phosphate amendments Treatment 5: Plants treated with rare earth lanthanum nitrate compound fertilizer (the solution of the present invention) Note: An equal amount of deionized water was used as a substitute for treatment 1; the amount added to treatments 2-4 was the same as the total amount of active ingredients in treatment 1 (the total amount of lanthanum nitrate in treatment 2 was 5 g, glycine in treatment 3 was 4.4 g, rare earth lanthanum nitrate was 0.6 g, humic acid in treatment 4 was 3.8 g, potassium fulvate from mineral source was 1 g, and diammonium hydrogen phosphate was 0.2 g. The rest were the same as in Example 1).

[0051] Experiment 3.3-3.4 Treatment groups Treatment 1: soil amended with a rare earth lanthanum nitrate composite amendment (No. 1, solution of the present invention); Treatment 2: soil amended with pure rare earth lanthanum nitrate amendment (No. 2); Treatment 3: soil amended with rare earth lanthanum nitrate + glycine amendment (No. 3); Treatment 4: soil amended with humic acid + mineral-derived potassium fulvate + diammonium phosphate amendment (No. 4); Treatment 5: Unamended soil (No. 5).

[0052] Note: In treatment 5, an equal amount of deionized water was used as a substitute; the amount added in each group of treatments 2-4 was the same as the total amount of active ingredients in treatment 1 (wherein, in treatment 2, a total amount of lanthanum nitrate was 5 g, in treatment 3, lanthanum nitrate was 0.6 g, glycine was 4.4 g, in treatment 4, humic acid was 3.8 g, potassium fulvate from minerals was 1 g, and diammonium phosphate was 0.2 g; the rest were the same as in Example 1).

[0053] 3. Research Results 3.1 Hydroponic experiment on plants grown with rare earth lanthanum nitrate composite modifier By changing only the number of days and keeping all other factors unchanged, we can study the effect of the single factor of days on the experimental results. Figure 1 The plants in (a) were treated 1-5 to study the hydroponic effects.

[0054] 3.1.1 Effects on plant germination rate and roots, stems and leaves like Figure 1 As shown in (b), the germination rate of sample No. 5 is 97%, which is higher than that of sample No. 3, which is 85%, which is higher than that of sample No. 2, which is 83%, which is higher than that of sample No. 4, which is 81%, and which is higher than that of sample No. 1, which is 80%. The germination rate first increases, then decreases, and finally increases rapidly with the different components. At the same time, the germination rate of plants applied with rare earth lanthanum nitrate is higher than that of plants without rare earth lanthanum nitrate, especially the germination rate of plants applied with rare earth lanthanum nitrate improver is the highest. Therefore, the application of rare earth lanthanum nitrate compound fertilizer improver can better promote the germination rate of plants.

[0055] Roots are the main organs for plants to absorb water and nutrients, and changes in their length can reflect the plant's ability to absorb nutrients in fertilizers. Figure 1 The root lengths of the plants shown in (c) are as follows: Sample 5 (3 cm), Sample 2 (2.1 cm), Sample 3 (2 cm), Sample 4 (1.7 cm), and Sample 1 (1.4 cm). Root lengths first increase, then decrease, and finally rise sharply depending on the fertilizer composition. Plants treated with the rare earth lanthanum nitrate compound fertilizer amendment have longer roots than those without it. In particular, plants treated with the rare earth lanthanum nitrate amendment exhibited vigorous growth and significantly longer roots. This suggests that the nutrients in the fertilizer promote root development, allowing roots to penetrate deeper into the soil and expand their absorption area, thereby providing more water and nutrients for the plants.

[0056] Leaves are the main site for photosynthesis in plants. Changes in their length can affect the photosynthesis efficiency of plants. Figure 1 As shown in (c), the leaf lengths of the plants are as follows: the leaf length of sample No. 5 is 1.1 cm > the leaf length of sample No. 3 is 0.7 cm > the leaf length of sample No. 2 is 0.6 cm > the leaf length of sample No. 4 is 0.6 > the leaf length of sample No. 1 is 0.5 cm. according to Figure 1The stem lengths of the plants shown in (c) are as follows: the stem length of sample No. 5 is 1.7 cm > the stem length of sample No. 3 is 1 cm > the stem length of sample No. 2 is 0.8 cm > the stem length of sample No. 4 is 0.7 cm > the stem length of sample No. 1 is 0.5 cm. The application of rare earth lanthanum nitrate compound fertilizer can promote the growth of stems, so the stems of alfalfa plants applied with rare earth lanthanum nitrate compound fertilizer are longer, indicating that rare earth lanthanum nitrate compound fertilizer can better promote the growth of roots and stems of plants. In summary, the sample modifier of treatment 5 of the present invention not only promotes the growth of stems, but also significantly increases the length of roots and leaves, indicating that it has a positive effect on the overall growth of plants. At the same time, by comparing samples No. 1 and No. 4 without rare earth application with samples No. 2, No. 3 and No. 5 with rare earth lanthanum application, it is highlighted that rare earth lanthanum nitrate promotes plant growth while also promoting the absorption of other components.

[0057] 3.1.2 Effects on pH and conductivity like Figure 2 As shown in (a), application of rare earth lanthanum nitrate compound fertilizer significantly reduced the pH of the hydroponic liquid. Treatment 1 had the highest pH, approaching 7.9. Treatment 2 had a slightly lower pH, approximately 7.6. Treatment 3 had a further decrease, approximately 7.3. Treatment 4 had a slightly higher pH, approximately 7.7. Treatment 5 had the lowest pH, approximately 7.1. The goal of improving saline-alkali soils is to lower the pH to near neutral (approximately 7). This was also true in the water experiment; sample 5 had the lowest pH, indicating its greatest pH-lowering effect. This demonstrates that the rare earth lanthanum nitrate amendment can effectively reduce the salt content in the samples and alleviate the stress caused by salinity and alkali on plants.

[0058] Electrical conductivity is an indicator of the soluble salt content in the soil. The lower the electrical conductivity, the less soluble salt content and the lower the degree of salinization. Figure 2 The following points can be observed in (b): Sample 1 has the highest conductivity, which is about 1060 us / cm. The conductivity of sample 2 dropped significantly, which is about 1020 us / cm. The conductivity of sample 3 increased slightly, which is about 1040 us / cm. The conductivity of sample 4 dropped again, which is about 1030 us / cm. The conductivity of sample 5 is the lowest, which is about 1010 us / cm. For the improvement of saline-alkali soil, the goal is to reduce the conductivity of the soil and reduce the soluble salt content in the soil. The same is true for experiments in water. From this point of view, sample 5 has the lowest conductivity, indicating that it is the most effective in reducing soil conductivity and is beneficial to plant growth. Combined with the above data, rare earth lanthanum nitrate improver works best in hydroponics.

[0059] 3.2 Soil culture experiment of plants cultivated with rare earth lanthanum nitrate composite amendment The experiment set up fertilizers with different compositions as controls, and through soil culture experiments, found the best composition as fertilizer for improving saline-alkali soil. Figure 3 The plants in the figure are soil culture experimental samples after treatments 1-5.

[0060] 3.2.1 Effects on plant germination rate and leaf area like Figure 4 As shown, application of rare earth lanthanum nitrate compound fertilizer significantly improved seed germination rates. Ten days after sowing, the germination rate of sample 5 was 95%, higher than that of sample 3 (85%), sample 2 (83%), sample 4 (82%), and sample 1 (80%). The germination rate curves showed an initial increase, then a decrease, and finally a rapid increase, depending on the composition of the amendment. The germination rate reached over 96% after application of rare earth lanthanum nitrate compound fertilizer, while the germination rate in unamended soil was only 80%. This indicates that rare earth lanthanum nitrate compound fertilizer amendment significantly alleviates the inhibitory effect of saline-alkali soil on seed germination and promotes seed germination in highly saline-alkali environments. Rare earth lanthanum nitrate compound fertilizer may improve seed germination rates by reducing salt stress in the soil.

[0061] Leaf area is an important indicator for measuring plant growth. The larger the leaf area, the higher the efficiency of photosynthesis in plants, which helps to increase the growth rate and yield of plants. Figure 4 As can be seen in the results, Sample 1 had the smallest leaf area, approximately 0.06 cm². Sample 2 had an increased leaf area, approximately 0.4 cm². Sample 3 had a slightly decreased leaf area, approximately 0.15 cm². Sample 4 had a further decrease, approximately 0.1 cm². Sample 5 had the largest leaf area, approximately 0.9 cm². Application of the rare earth lanthanum nitrate compound fertilizer amendment significantly increased the leaf area of ​​the plants. Ten days after application, the leaf area of ​​Sample 5 was 0.9 cm², which was significantly greater than Sample 2 (0.45 cm²), Sample 3 (0.18 cm²), Sample 4 (0.09 cm²), and Sample 1 (0.06 cm²). The average leaf area of ​​plants treated with the rare earth lanthanum nitrate compound fertilizer amendment reached 0.9 cm², while that of plants in unamended soil was only 0.06 cm². This indicates that rare earth lanthanum nitrate fertilizer significantly promotes plant leaf growth, increases leaf area, and thus improves plant photosynthesis efficiency. Therefore, rare earth lanthanum nitrate compound fertilizer increases the leaf area and improves the growth ability of the plant.

[0062] 3.2.2 Experiment on the effect on plant chlorophyll like Figure 5As shown, the chlorophyll content of the samples from large to small is No. 5> No. 3> No. 2> No. 1> No. 4. The chlorophyll content of the plants cultivated with the unmodified samples is 12.3 mg / L, the chlorophyll content of the plants with pure lanthanum nitrate as the improver is 15.3 mg / L, the chlorophyll content of the plants with lanthanum nitrate plus glycine as the improver is 25.4 mg / L, the chlorophyll content of the plants with mineral potassium fulvic acid, humic acid, and diammonium phosphate as the improver is 8.3 mg / L, and the chlorophyll content of the plants with rare earth lanthanum nitrate compound fertilizer as the improver is 27.5 mg / L, among which the chlorophyll content of the plants treated with rare earth lanthanum nitrate compound amendment increased the most, which indicates that rare earth lanthanum nitrate compound amendment can significantly alleviate the inhibitory effect of saline-alkali soil on plant chlorophyll synthesis and enhance the photosynthesis capacity of plants. Therefore, rare earth lanthanum nitrate compound amendment is the best ingredient, indicating that the ingredients of rare earth lanthanum nitrate compound amendment have the same effect on the hydroponic and soil culture results of alfalfa, and the hydroponic experiment can provide theoretical support for the soil culture experiment.

[0063] 3.2.3 Experiments on the effects of soil pH and salinity like Figure 6 As shown in (a), soil pH decreased significantly after application of the rare earth lanthanum nitrate compound fertilizer amendment. Sample 1 had the highest pH, approaching 8.9. After application of the lanthanum nitrate amendment, the pH of Sample 2 dropped significantly, reaching approximately 8.4. The pH of Sample 3 dropped further, reaching approximately 8.3. The pH of Sample 4 continued to decline, reaching approximately 8.2. Sample 5 had the lowest pH, at approximately 8.1. The goal of improving saline-alkali soils is to lower the pH to near neutral (approximately pH 7). From this perspective, Sample 5 had the lowest pH, indicating its greatest effectiveness in lowering soil pH. This demonstrates that the rare earth lanthanum nitrate amendment can effectively reduce soil salt content and alleviate the stress caused by salinity and alkali on plants.

[0064] Salt content refers to the total content of all soluble salts in the soil, including sodium salts (such as sodium chloride, sodium sulfate, etc.) and other salts (such as calcium salts, magnesium salts, etc.). It is an overall measure of the soluble salts in the soil. Salt content is an indicator of the soluble salt content in the soil. The lower the salt content, the less soluble salt content in the soil and the lower the degree of soil salinization. Figure 6The following points can be observed in (b): Sample 1 has the highest salt content, which is about 4.5 mg / kg. The salt content of Sample 2 has dropped significantly, which is about 1.4 mg / kg. The conductivity of Sample 3 has increased, which is about 1.5 mg / kg. The salt content of Sample 4 has rebounded to about 2.1 mg / kg, and the salt content of Sample 5 is the lowest, which is about 1.2 mg / kg. For the improvement of saline-alkali soil, the goal is to reduce the salt content of the soil and reduce the soluble salt content in the soil. From this point of view, Sample 5 has the lowest salt content, indicating that it is the most effective in reducing the salt content of the soil, which is beneficial to plant growth. Combined with the above data, rare earth lanthanum nitrate improver is most effective in soil improvement.

[0065] 3.3 Analysis of the effect of rare earth lanthanum nitrate composite modifier on sodium content in saline-alkali soil Sodium content refers to the content of sodium ions (Na⁺) in the soil. It is the part of salt content related to sodium and reflects the amount of sodium ions alone. Figure 7 The sodium content in the unamended soil (sample 5) was 1.52 mg / kg. After adding the rare earth lanthanum nitrate composite amendment sample 1, the sodium content dropped to 0.336 mg / kg. The sodium content in the soil amended with amendment sample 2 reached 1.10 mg / kg, the sodium content in the soil amended with amendment sample 3 reached 1.05 mg / kg, and the sodium content in the soil amended with amendment sample 4 reached 1.34 mg / kg. This demonstrates that amendments containing rare earth elements are more effective at reducing sodium content than those without, and also demonstrates that rare earth elements promote the absorption of other components. The soil amended with the rare earth lanthanum nitrate composite amendment exhibits significant advantages in improving soil quality, attributed to the rational combination of the rare earth source, chelating agent, and auxiliary raw materials in the amendment.

[0066] 3.4 Analysis of heavy metal content in saline-alkali soil using rare earth lanthanum nitrate composite modifier Table 1 Heavy metal content in soil

[0067] As shown in Table 1 and Figure 8As shown in Table 1, after applying the rare earth lanthanum nitrate composite modifier, the heavy metal chromium content in the soil decreased from 14.36 mg / kg to below the instrument precision, and the mercury content decreased from 0.159 mg / kg to below the instrument precision. The remaining heavy metals all decreased, the nickel content decreased from 84.872 mg / kg to 10.292 mg / kg, and the aluminum content decreased from 39.035 mg / kg to 20.525 mg / kg. According to the heavy metal content table in Table 1 and the following scanning electron microscope images and X-ray fluorescence spectrometers, it is characterized and proved. Under the technical solution of the present invention, the heavy metal content in saline-alkali soil can be significantly reduced. Controlling the heavy metal content in saline-alkali soil is of great significance to ensuring ecological safety and agricultural product quality safety.

[0068] 3.5 Characterization and analysis of soil morphology The soil structure was analyzed after treatment with the condition modifier of the present invention. Figure 9 It can be clearly seen that the unimproved saline-alkali soil is compacted and hard, with particles squeezed against each other and almost no visible pores. This soil structure indicates that the compaction phenomenon is very serious, in stark contrast to the normal loose soil structure. The degree of soil compaction in the figure has seriously hindered the performance of these basic functions. Figure 10 It can be seen that the improved upper soil has a more obvious structure, with evenly distributed pores and regular shapes. The soil is loose and porous, with larger pore diameters and optimized soil structure, which helps to improve soil aeration and water retention capacity, and is also conducive to the expansion of the root system and the absorption of nutrients. Figure 11 The study demonstrated that the subsoil modified with the rare earth lanthanum nitrate composite modifier exhibited a higher porosity than unmodified soil, facilitating the circulation of water and air, thereby promoting plant root growth and nutrient absorption. This improved soil structure is a key advantage. The increased pore size significantly enhances soil aeration and water permeability, allowing air and water to flow freely, creating an optimal growth environment for plant roots. This allows roots to penetrate deeper, absorb more water and nutrients, and enhance plant resistance to drought.

[0069] 3.6 Characterization and analysis of soil specific surface area Depend on Figure 12 It can be seen that as the pore width increases, the pore volume also increases. The pore structure of the soil improved by rare earth lanthanum nitrate compound fertilizer has a larger pore volume than the unimproved soil at the same pore width. Figure 12(b) shows the pore size distribution of the compound fertilizer sample. The pore size is primarily concentrated in the 50-100 nm range, indicating that the sample has a rich mesoporous structure, which is crucial for the adsorption and nutrient release properties of the compound fertilizer. The pore volume change rate (black squares and red dots) represents the pore volume change rate under different conditions. The pore volume change rate is higher in the 50-100 nm range, indicating that there are more pores in this range, which contributes significantly to the specific surface area of ​​the rare earth lanthanum nitrate compound fertilizer. Figure 12 (a) is the adsorption-desorption isotherm diagram, and the adsorption-desorption behavior is as follows Figure 12 (b) shows the nitrogen adsorption-desorption isotherms of the compound fertilizer sample. The isotherms are typical type IV isotherms, indicating that the sample has a mesoporous structure. The adsorption amount changes in the stage of relative pressure P / P0<0.50, and the adsorption amount increases, indicating the presence of micropores; in the stage of 0.50≤P / P0≤0.88, the adsorption amount increases significantly, indicating the presence of a large number of mesopores; at high relative pressure P / P0>0.88, the adsorption amount increases sharply, indicating the presence of a small number of macropores. The hysteresis between the adsorption and desorption curves indicates the presence of capillary condensation, which further confirms the existence of a mesoporous structure. When P / P0>0.92, there will be a leap on the isotherm, and the adsorption and desorption curves of the two groups are close to parallel, indicating that there are a small number of macropores inside, but according to the adsorption volume of the two groups of curves, it can be seen that the addition of rare earth lanthanum nitrate compound fertilizer increases the adsorption amount and the volume of each pore size, but the unimproved soil group has a significant decline in adsorption volume. Figure 12 (b) It can be seen that the total pore volume of the two groups shows a trend of first increasing and then decreasing. When the pore volume is 0.5%, the difference in pore width between the two groups is small. Figure 12 (b) shows that the pore sizes of both groups are primarily distributed between 30 and 130 nm, with an average pore size of 75 nm, indicating typical mesoporous materials. Within the pore size range of 0-30 nm, the pore volume rise curves for different pore sizes become steeper with increasing amounts of rare earth lanthanum nitrate compound fertilizer. The pore volume of the group containing rare earth lanthanum nitrate compound fertilizer increases to varying degrees compared to the group without rare earth lanthanum nitrate compound fertilizer.

[0070] The above description is only a specific 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 any technician familiar with this technical field within the technical scope disclosed in the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner, characterized in that: The preparation method comprises the following steps: S1. Raw material preparation: Select rare earth lanthanum source, chelating agent, auxiliary raw materials and deionized water; According to the mass ratio, the rare earth lanthanum source is 3-8 parts of lanthanum nitrate; The chelating agents are humic acid and glycine, with 15-25 parts of humic acid and 8-16 parts of glycine; The auxiliary raw materials are diammonium hydrogen phosphate and mineral-source potassium fulvate, wherein diammonium hydrogen phosphate is 1-3 parts and mineral-source potassium fulvate is 7-13 parts; Deionized water is 800-1200 parts; S2. Thoroughly mix lanthanum nitrate and glycine, add half of deionized water, and stir on a magnetic stirrer to dissolve, to obtain Liquid A; S3. Thoroughly mix the humic acid and mineral-derived potassium fulvate, add the remaining deionized water, and stir on a magnetic stirrer to dissolve, to obtain Liquid B; S4. Add diammonium hydrogen phosphate to liquid B, stir on a magnetic stirrer to dissolve it, and obtain liquid C; S5. Mix liquid A and liquid C together, place them on a magnetic stirrer and continue stirring and dissolving to obtain the novel rare earth lanthanum fertilizer saline-alkali soil conditioner.

2. The method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner according to claim 1, wherein: According to the mass ratio, the raw material dosage is 6 parts of lanthanum nitrate, 20 parts of humic acid, 12 parts of glycine, 2 parts of diammonium hydrogen phosphate, 10 parts of mineral potassium humate, and 1000 parts of deionized water.

3. The preparation method of a novel rare earth lanthanum fertilizer saline-alkali soil conditioner according to claim 1, characterized in that: The stirring step S2 is performed for 10-20 minutes, the stirring step S3 is performed for 2-4 hours, and the stirring steps S4 and S5 are performed for 20-40 minutes respectively.

4. The method for preparing a novel rare earth lanthanum fertilizer saline-alkali soil conditioner according to claim 1, wherein: The method further includes S6, performing performance index testing on the rare earth lanthanum fertilizer saline-alkali soil conditioner obtained in S5, including the effects on plant germination rate and roots, stems and leaves, pH, salt content, chlorophyll, sodium content, chromium, mercury, aluminum, nickel ion testing and soil morphology analysis.

5. A rare earth lanthanum fertilizer saline-alkali soil conditioner prepared by the preparation method of the novel rare earth lanthanum fertilizer saline-alkali soil conditioner according to any one of claims 1 to 4.

6. Use of the rare earth lanthanum fertilizer saline-alkali soil conditioner according to claim 5 in improving saline-alkali soil for alfalfa plants.

7. The use according to claim 6, characterized in that The application is to improve saline-alkali soil for alfalfa cultivation, and the improver is applied to the soil once every three days.

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