Stress-resistant water-soluble fertilizer for relieving saline-alkali stress and preparation method thereof

Abstract

The invention belongs to the technical field of functional fertilizers, and discloses a stress-resistant water-soluble fertilizer for alleviating saline-alkali stress and a preparation method thereof, the water-soluble fertilizer is composed of water-soluble macroelement nutrients, mineral regulatory factors, modified bentonite, a plant signal activator and medium trace elements. Calcium nitrate, zinc sulfate and potassium silicate are introduced to regulate the balance of rhizosphere ions, modified bentonite is utilized to selectively adsorb sodium ions and regulate the acid-base environment of the rhizosphere, and methyl salicylate is applied to induce the expression of a plant stress resistance signal channel, so that the synergistic regulation of rhizosphere ion environment optimization and plant endogenous stress resistance improvement is realized. The fertilizer can effectively reduce the proportion of sodium and potassium in crops and improve the growth stability and nutrient absorption efficiency of the crops under saline-alkali conditions, and the preparation method is stable in process and suitable for water and fertilizer integrated application of the crops in saline-alkali areas.

Description

Technical Field

[0001] This invention belongs to the field of functional fertilizer technology, specifically relating to a stress-resistant water-soluble fertilizer for mitigating salt-alkali stress and its preparation method. Background Technology

[0002] my country has a wide distribution of saline-alkali land resources, covering an area of ​​over 100 million mu (approximately 6.67 million hectares), mainly concentrated in the Northeast, Northwest, and North China regions. High soil salinity and alkalinity create a harsh rhizosphere environment for crops, leading to hindered water absorption, exacerbated ion toxicity, nutrient imbalance, and decreased photosynthetic efficiency, severely restricting sustainable agricultural development and the efficient use of arable land resources. To alleviate the adverse effects of saline-alkali stress on crop growth, the development of functional stress-resistant fertilizers has become an important direction for agricultural research and fertilizer management.

[0003] Most water-soluble fertilizers currently on the market primarily contain nitrogen, phosphorus, and potassium, supplemented with micronutrients. While these can meet basic nutritional needs, their effectiveness in alleviating salt-alkali stress, optimizing the rhizosphere environment, and improving crop salt tolerance is limited. Some improved fertilizers, although attempting to incorporate stress regulators or adsorbents, suffer from problems such as single-component formulations, poor ion selectivity, insignificant synergistic effects, and poor stability, failing to meet the complex needs of crop nutrient regulation and slow-release under high stress conditions in saline-alkali soils. Therefore, there is an urgent need to design a novel stress-resistant water-soluble fertilizer that integrates ion buffering regulation, rhizosphere environment improvement, balanced nutrient supply, and signal activation for stress resistance. This type of fertilizer should possess good water solubility and ease of application, along with multi-component synergistic salt-alkali resistance capabilities, effectively enhancing crop stress resistance and nutrient utilization efficiency under salt-alkali stress conditions. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a stress-resistant water-soluble fertilizer for mitigating salt-alkali stress and its preparation method. The fertilizer is composed of water-soluble macroelements, mineral regulators, modified bentonite, plant signal activators, microelements, and solubilizers and stabilizers, which can synergistically improve the rhizosphere ion environment of crops and enhance the crop's salt-alkali resistance and nutrient absorption efficiency.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A stress-resistant water-soluble fertilizer for mitigating salt-alkali stress comprises the following raw materials in parts by weight: 40-65 parts of water-soluble macronutrients, 5-15 parts of mineral regulators, 3-12 parts of modified bentonite, 0.05-1.0 parts of plant signal activator, 3-10 parts of micronutrients, and 1-5 parts of water-soluble solubilizer and stabilizer.

[0007] More preferably, the water-soluble macronutrients are composed of ammonium nitrate, potassium dihydrogen phosphate and potassium sulfate, and the mass ratio of the three is ammonium nitrate: potassium dihydrogen phosphate: potassium sulfate = 1~2:0.5~1.5:1~2.

[0008] More preferably, the mineral regulating factor includes calcium nitrate, zinc sulfate and potassium silicate, with a mass ratio of 1-2:0.5-1.5:0.5-1.5.

[0009] More preferably, the preparation method of modified bentonite specifically includes the following steps:

[0010] S101. After drying the bentonite under heating conditions, it is crushed and sieved to obtain pretreated bentonite;

[0011] S102. Disperse the pretreated bentonite in deionized water, add 5% to 10% by mass of quaternary ammonium salt of bentonite, and react under heating and stirring conditions;

[0012] S103. After washing the modified product until the conductivity is below the preset range, centrifuge and resuspend it in a mixture containing tetraethyl orthosilicate and an alkaline additive, and continue the reaction under constant temperature conditions.

[0013] S104. The coated and modified bentonite is washed, dried and crushed to obtain the final modified bentonite product.

[0014] More preferably, the plant signal activator is methyl salicylate;

[0015] The trace element components include chelated boron, chelated iron, and magnesium sulfate;

[0016] The water-soluble solubilizing stabilizer is selected from one or more of sodium citrate, polyaspartic acid, sodium lignosulfonate, and potassium sodium tartrate.

[0017] A method for preparing a stress-resistant water-soluble fertilizer for mitigating salt-alkali stress includes the following steps:

[0018] S1. Add ammonium nitrate, potassium dihydrogen phosphate and potassium sulfate to pure water in sequence, stir and mix to form a basic nutrient solution;

[0019] S2. Add calcium nitrate, zinc sulfate and potassium silicate to the basic nutrient solution in sequence, while keeping the mixture stirred continuously to form a compound nutrient system;

[0020] S3. Slowly add the modified bentonite to the above mixture and disperse it evenly under the action of the stirring device to form a bentonite suspension system;

[0021] S4. Add methyl salicylate, chelated boron, chelated iron and magnesium sulfate in sequence, stir and mix, then add water-soluble solubilizing stabilizer, and mix evenly to obtain the stress-resistant water-soluble fertilizer.

[0022] More preferably, the time for adding modified bentonite in step S3 is controlled at 10 to 30 minutes, and the stirring speed is maintained at 500 to 1000 revolutions per minute.

[0023] More preferably, after adding methyl salicylate and trace elements in step S4, continue stirring for 10-20 minutes, and then add a water-soluble solubilizing stabilizer.

[0024] More preferably, the stress-resistant water-soluble fertilizer is a liquid formulation or a suspension formulation with both liquid and solid components.

[0025] More preferably, the stress-resistant water-soluble fertilizer is suitable for fertigation via drip irrigation, spraying, or root irrigation.

[0026] The beneficial effects of this invention are:

[0027] This invention introduces mineral regulators and modified bentonite with pH buffering and Na⁺ selective adsorption capabilities into the formulation design. Combined with the plant signaling activator methyl salicylate to induce the plant's own stress resistance response, and supplemented with chelated boron, chelated iron, and magnesium sulfate nutrients to compensate for micronutrient deficiencies caused by salt and alkali stress, this invention constructs a four-in-one functional network of "ion regulation—rhizosphere stability—signal activation—nutrient balance." In the fertilizer aqueous phase system, the addition of modified bentonite with organic intercalation and inorganic silica coating as a directional regulating material not only improves suspension stability but also enhances the adsorption capacity for sodium ions and provides a slow-release support interface, significantly differentiating it from simple adsorption-type inorganic carriers. The accompanying water-soluble solubilizing and stabilizing agent system ensures the compatible dispersion of multiple components in the liquid phase, solving the system stability problem of micronutrients and functional factors. Experiments show that applying the fertilizer of this invention under moderately saline-alkali soil conditions can significantly reduce the electrical conductivity of the rhizosphere soil, increase the activity of salt-resistance-related enzymes in plants, promote root development, and significantly improve growth vigor and yield performance compared with conventional fertilizers. Attached Figure Description

[0028] The invention will now be further described with reference to the accompanying drawings.

[0029] Figure 1 Figures showing the growth indicators of wheat seedlings after 14 days of fertilizer treatment in the examples and comparative cases.

[0030] Figure 2 Comparison of soil EC and pH values ​​between different treatment groups;

[0031] Figure 3A comparison of the K⁺ / Na⁺ ratios of wheat seedlings in different treatment groups;

[0032] Figure 4 A comparison chart of yield traits in wheat from different treatment groups. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] I. Preparation of Modified Bentonite

[0036] Take 100 g of natural sodium-based bentonite and dry it at 105℃ for 6 hours. After drying, mechanically pulverize it using a pulverizer and pass it through a 120-mesh sieve. Set aside for later use. Add 2000 mL of deionized water to a flask and slowly add 6 g of hexadecyltrimethylammonium bromide while stirring. Heat to 60℃ to fully dissolve the bromide and form a modifier solution. Slowly add the pretreated bentonite to the modification solution (solid-liquid mass ratio 1:20), stir at 500 rpm at 60℃ and react for 4 hours. After the reaction, allow the slurry to settle and discard the supernatant. Centrifuge the precipitate and wash it repeatedly with deionized water 3 times until the conductivity of the washing solution drops to less than 100 μS / cm. Resuspend the washed modified bentonite in 1000 mL of deionized water, add a mixture of 8 mL of tetraethyl orthosilicate and 3 mL of ammonia (25%), adjust the pH of the system to 9-10, and react at 50℃ for 3 hours. After the reaction was completed, the slurry was centrifuged and separated. The resulting solid was washed twice with water and dried in an oven at 80°C for 12 hours. After drying, it was pulverized using a pulverizer and passed through a 120-mesh sieve to obtain the modified bentonite.

[0037] II. Preparation of Stress-Resistant Water-Soluble Fertilizers

[0038] The stress-resistant water-soluble fertilizer contains the following raw materials in parts by weight: 40 parts water-soluble macronutrients, 5 parts mineral regulators, 3 parts modified bentonite, 0.05 parts plant signal activator, 3 parts micronutrients, and 1 part water-soluble solubilizer and stabilizer.

[0039] The preparation steps of the stress-resistant water-soluble fertilizer are as follows:

[0040] S1. Add 1000 mL of deionized water to a clean reaction vessel, and add 20 g of ammonium nitrate, 10 g of potassium dihydrogen phosphate and 10 g of potassium sulfate in sequence at 600 rpm under normal temperature conditions. Stir for 15 minutes to form a uniform and transparent basic nutrient solution.

[0041] S2. In the basic nutrient solution, continue to add 2.5 g of calcium nitrate, 1.25 g of zinc sulfate and 1.25 g of potassium silicate in sequence, keep the stirring temperature at 30℃ and the speed unchanged, and continue stirring for 10 minutes to form a stable compound nutrient system.

[0042] S3. Slowly add 3.0 g of modified bentonite to the above compound nutrient system, adding it evenly under continuous stirring. The addition time should be controlled within 5 minutes. After adding, continue stirring for 15 minutes, and increase the stirring speed to 800 rpm.

[0043] S4. While maintaining stirring, add 0.05 g of methyl salicylate (pre-dissolved in 2 mL of ethanol), 1.0 g of chelated boron, 1.0 g of chelated iron, and 1.0 g of magnesium sulfate sequentially, and continue stirring for 10 minutes until fully dissolved. Then add 1.0 g of sodium citrate and stir for 5 minutes until a clear, transparent, or slightly turbid stable liquid fertilizer is formed, thus obtaining the stress-resistant water-soluble fertilizer.

[0044] Example 2

[0045] The preparation method and steps of the modified bentonite are the same as those in Example 1.

[0046] The stress-resistant water-soluble fertilizer contains the following raw materials in parts by weight: 65 parts water-soluble macronutrients, 15 parts mineral regulators, 12 parts modified bentonite, 1.0 part plant signal activator, 10 parts micronutrients, and 5 parts water-soluble solubilizer and stabilizer.

[0047] The preparation steps of the stress-resistant water-soluble fertilizer are as follows:

[0048] S1. Add 1000 mL of deionized water to the reactor and start stirring at room temperature with a stirring speed of 600 rpm. Add 32.5 g of ammonium nitrate, 16.25 g of potassium dihydrogen phosphate, and 16.25 g of potassium sulfate in sequence, and continue stirring for 20 minutes until completely dissolved to form a high-concentration basic nutrient solution.

[0049] S2. Add 7.5 g of calcium nitrate, 3.75 g of zinc sulfate and 3.75 g of potassium silicate to the basic nutrient solution in sequence. Control the stirring temperature at 35℃, maintain the stirring speed, and stir for 15 minutes to form a stable composite solution.

[0050] S3. Slowly add 12.0 g of modified bentonite to the above composite liquid, adding it evenly while stirring. The feeding process should be completed within 8 minutes, and then the stirring speed should be increased to 900 rpm.

[0051] S4. Add 1.0 g of methyl salicylate (pre-dissolved in 3 mL of ethanol), 3.33 g of chelated boron, 3.33 g of chelated iron, and 3.33 g of magnesium sulfate sequentially, and continue stirring for 15 minutes to ensure that all functional factors are fully dissolved. Finally, add 5.0 g of polyaspartic acid and stir for 10 minutes to make the entire system clear and homogeneous, thus obtaining the stress-resistant water-soluble fertilizer.

[0052] Example 3

[0053] The preparation method and steps of the modified bentonite are the same as those in Example 1.

[0054] The stress-resistant water-soluble fertilizer contains the following raw materials in parts by weight: 52.5 parts water-soluble macronutrients, 10 parts mineral regulators, 7.5 parts modified bentonite, 0.525 parts plant signal activator, 6.5 parts micronutrients, and 3 parts water-soluble solubilizer and stabilizer.

[0055] The preparation steps of the stress-resistant water-soluble fertilizer are as follows:

[0056] S1. Add 1000 mL of deionized water to a clean reactor, start the stirring device, and set the speed to 600 rpm. Under room temperature conditions, add 26.25 g of ammonium nitrate, 13.125 g of potassium dihydrogen phosphate, and 13.125 g of potassium sulfate in sequence, and continue stirring for 15 minutes until the three water-soluble macroelements are completely dissolved to form a homogeneous basic nutrient solution.

[0057] S2. Continue to add 5.0 g calcium nitrate, 2.5 g zinc sulfate and 2.5 g potassium silicate to the basic nutrient solution. Set the stirring temperature to 32℃ and maintain stirring for about 12 minutes to allow the mineral components to fully dissolve and form a stable composite nutrient system.

[0058] S3. Slowly add 7.5 g of modified bentonite to the composite solution, adding it gradually while stirring, and complete the addition within 6 minutes. After the addition is complete, increase the stirring speed to 850 rpm and continue stirring for 20 minutes to form a grayish-white uniform suspension system.

[0059] S4. To the above suspension system, add 0.525 g of methyl salicylate (pre-dissolved in 2 mL of ethanol), 2.17 g of chelated boron, 2.17 g of chelated iron, and 2.17 g of magnesium sulfate sequentially, and stir continuously for 10 minutes to ensure thorough mixing. Then add 3.0 g of sodium lignosulfonate as a water-soluble solubilizing stabilizer, and continue stirring for 5 minutes to obtain the stress-resistant water-soluble fertilizer.

[0060] Comparative Example 1

[0061] The stress-resistant water-soluble fertilizer contains the following raw materials in parts by weight: 52.5 parts water-soluble macronutrients, 10 parts mineral regulators, 0.525 parts plant signal activator, 6.5 parts micronutrients, and 3 parts water-soluble solubilizer and stabilizer.

[0062] The preparation steps of the stress-resistant water-soluble fertilizer are as follows:

[0063] S1. Add 1000 mL of deionized water to the reactor, turn on the stirrer, and set the speed to 600 rpm. At room temperature, add 26.25 g of ammonium nitrate, 13.125 g of potassium dihydrogen phosphate, and 13.125 g of potassium sulfate in sequence, and stir continuously for 15 minutes to ensure complete dissolution, thus obtaining the basic nutrient solution.

[0064] S2. Add 5.0 g of calcium nitrate, 2.5 g of zinc sulfate and 2.5 g of potassium silicate to the above solution in sequence. Keep the stirring temperature at 32℃ and the stirring speed constant. Continue stirring for 12 minutes to fully dissolve the mineral regulator and form a compound nutrient system.

[0065] S3. Add 0.525 g of methyl salicylate (pre-dissolved in 2 mL of ethanol), 2.17 g of chelated boron, 2.17 g of chelated iron and 2.17 g of magnesium sulfate, stir for 10 minutes to mix thoroughly, then add 3.0 g of sodium lignosulfonate and continue stirring for 5 minutes to obtain a transparent liquid fertilizer solution, which is the stress-resistant water-soluble fertilizer.

[0066] Comparative Example 2

[0067] The preparation method and steps of the modified bentonite are the same as those in Example 1.

[0068] The stress-resistant water-soluble fertilizer contains the following raw materials in parts by weight: 52.5 parts water-soluble macronutrients, 10 parts mineral regulators, 7.5 parts modified bentonite, 6.5 parts micronutrients, and 3 parts water-soluble solubilizer and stabilizer.

[0069] The preparation steps of the stress-resistant water-soluble fertilizer are as follows:

[0070] S1. Add 1000 mL of deionized water to the reactor, turn on the stirrer, and set the speed to 600 rpm. Add 26.25 g of ammonium nitrate, 13.125 g of potassium dihydrogen phosphate, and 13.125 g of potassium sulfate in sequence, and stir at room temperature for 15 minutes to ensure that the three nutrients are completely dissolved to form the basic nutrient solution.

[0071] S2. Continue to add 5.0 g calcium nitrate, 2.5 g zinc sulfate and 2.5 g potassium silicate to the base solution, stir at 32℃ for 12 minutes to obtain a homogeneous compound nutrient system.

[0072] S3. Slowly add 7.5 g of modified bentonite, maintain stirring, and control the feeding time within 6 minutes. Then increase the stirring speed to 850 rpm and continue stirring for 20 minutes to form a stable and dispersed bentonite suspension system.

[0073] S4. Add 2.17 g of chelated boron, 2.17 g of chelated iron and 2.17 g of magnesium sulfate to the suspension system, stir for 10 minutes until completely dissolved, then add 3.0 g of sodium lignosulfonate and stir for 5 minutes to obtain a slightly turbid and transparent liquid fertilizer, which is the stress-resistant water-soluble fertilizer.

[0074] Performance testing

[0075] 1. Test methods for plant seedling growth indicators

[0076] Wheat was selected as the test crop. Artificially prepared moderately saline-alkali stress soil (pH 8.5, electrical conductivity 3.5 mS / cm) was filled into nutrient pots. After sowing, five treatment groups were set up: Examples 1-3 and Comparative Examples 1-2, with three replicates per group. Ten wheat seeds were sown per pot. Liquid fertilizer for each treatment was applied starting on the third day after sowing, diluted 200 times, every three days for 14 consecutive days. On the 14th day, growth indicators were measured, including average seedling height, average taproot length, aboveground fresh weight, and dry weight. Dry weight was measured after drying at 80℃ to constant weight, and the average values ​​were recorded. The results are shown in Table 1 below.

[0077] Table 1. Growth indicators of wheat seedlings under different treatments

[0078] Processing group Seedling height (cm) Root length (cm) Fresh weight of above-ground parts (g) Dry weight of aboveground parts (g) Example 1 12.3 10.6 1.85 0.39 Example 2 16.1 14.3 2.65 0.62 Example 3 14.2 12.7 2.30 0.51 Comparative Example 1 10.5 8.8 1.48 0.30 Comparative Example 2 11.0 9.1 1.55 0.32

[0079] Table 1 shows that wheat seedlings in Examples 1-3 were superior to the control group in terms of seedling height, root length, and biomass. Example 2, in particular, showed the best performance across all indicators, demonstrating that a high-ratio, stress-resistant water-soluble fertilizer can significantly promote plant growth. In contrast, after removing modified bentonite from Control Example 1, root length and dry matter accumulation decreased significantly, indicating that this component played an important role in regulating rhizosphere salinity and improving root development. Similarly, removing methyl salicylate from Control Example 2 also led to a decrease in seedling height and fresh weight, reflecting the positive role of plant signaling activators in enhancing plant stress resistance.

[0080] 2. Salt-alkali stress relief ability test

[0081] On the day of plant harvest (day 14 of treatment), soil samples were collected from the rhizosphere within 5 cm of the potted wheat plants in each treatment. After mixing, the samples were extracted by shaking at a ratio of 1:5 (air-dried soil to deionized water) for 30 minutes. After settling, the conductivity (EC value, mS / cm) of the supernatant was measured using a conductivity meter, reflecting the rhizosphere salt concentration. The soil pH of another sample was measured using the glass electrode method. Each group was replicated in triplicate, and the average value was recorded. The results are shown in Table 2 below.

[0082] Table 2. EC and pH values ​​of rhizosphere soil in different treatment groups

[0083] Processing group Root zone EC value (mS / cm) rhizosphere pH Example 1 2.89 8.15 Example 2 2.32 7.85 Example 3 2.51 8.00 Comparative Example 1 3.41 8.42 Comparative Example 2 3.26 8.35

[0084] As shown in Table 2, the rhizosphere electrical conductivity (EC value) of the treatment groups in Examples 1-3 was significantly lower than that of Comparative Examples 1 and 2, indicating that the stress-resistant water-soluble fertilizer prepared in this invention has good salt regulation ability, can effectively reduce rhizosphere salt concentration, and alleviate ion toxicity. Among them, Example 2 had the lowest EC value, at 2.32 mS / cm, indicating that the Na⁺ selective adsorption of modified bentonite was more significant under high-ratio conditions, and a good ion buffering effect was produced by combining with weakly acidic trace components. In terms of pH value, the Example groups were also lower than the Comparative Examples, showing that the fertilizer has a certain alkaline neutralization function. In contrast, Comparative Examples 1 and 2 had poor soil salinity restoration ability.

[0085] 3. Ion selective absorption test

[0086] Wheat seedlings harvested on day 14 were processed. Aboveground tissue and 5 cm of rhizosphere soil were collected separately, dried, and ground into powder. 0.2 g of plant sample was weighed, digested with a nitric acid-perchloric acid mixture, and after volume adjustment, the Na⁺, K⁺, and Ca²⁺ contents were determined by atomic absorption spectrometry (AAS). The K⁺ / Na⁺ ratio was used to measure the selective absorption capacity of potassium ions; a higher ratio indicates that the plant can better maintain ion balance under high-salt conditions, thus enhancing salt tolerance. Each group was replicated in triplicate, and the average value was recorded. The results are shown in Table 3 below.

[0087] Table 3. Ion content and K⁺ / Na⁺ ratio in wheat from different treatment groups

[0088] Processing group Na⁺ (mg / g) K⁺ (mg / g) Ca²⁺ (mg / g) K⁺ / Na⁺ ratio Example 1 6.21 15.38 4.52 2.48 Example 2 4.95 17.82 5.10 3.60 Example 3 5.38 16.45 4.88 3.06 Comparative Example 1 8.14 12.30 3.87 1.51 Comparative Example 2 7.62 13.00 4.01 1.71

[0089] As shown in Table 3, the Na⁺ content in wheat treated in Examples 1-3 was significantly lower than that in the comparative examples, while the K⁺ and Ca²⁺ contents were significantly increased. In particular, the K⁺ / Na⁺ ratio in Example 2 reached 3.60, far exceeding that of Comparative Examples 1 and 2. This indicates that the stress-resistant water-soluble fertilizer of this invention can significantly enhance the selective absorption capacity of potassium ions and effectively inhibit sodium ion accumulation. This performance stems from the modified bentonite introduced into the formula, which possesses Na⁺ selective adsorption characteristics, rapidly capturing free sodium ions in the rhizosphere and alleviating ion toxicity. Simultaneously, the combination of calcium nitrate and zinc sulfate optimizes intracellular ion balance and enhances membrane channel regulation. Furthermore, plant signaling activators such as methyl salicylate can also indirectly improve potassium uptake efficiency by inducing the expression of ion transport channels. The synergistic effect of these mechanisms enables crops to maintain a high K⁺ / Na⁺ ratio under salt-alkali stress, thereby enhancing salt tolerance and homeostasis regulation capabilities.

[0090] 4. Plant physiological stress resistance test

[0091] Wheat functional leaves were collected on day 14 of treatment, and 0.5 g of fresh leaves were weighed for physiological index determination. Relative water content (RWC) of leaves was calculated by weighing fresh weight, saturated weight, and dry weight using the formula RWC = (fresh weight - dry weight) / (saturated weight - dry weight) × 100%. SOD, CAT, POD activities, and MDA content were determined using commercially available kits (photometric method), following the instructions. Each treatment was repeated in triplicate, and the data were averaged. The results are shown in Table 4 below.

[0092] Table 4 Physiological stress resistance indicators of plants in different treatment groups

[0093] Processing group RWC (%) SOD (U / g FW) CAT (U / g FW) POD (U / g FW) MDA (nmol / g FW) Example 1 77.2 128.3 9.6 21.5 8.25 Example 2 84.6 152.1 12.3 26.8 5.42 Example 3 81.0 141.7 11.0 24.1 6.38 Comparative Example 1 69.5 102.4 7.4 17.3 10.61 Comparative Example 2 71.2 108.6 7.9 18.6 9.94

[0094] As shown in Table 4, the relative water content (RWC) and antioxidant enzyme activities (SOD, CAT, POD) of wheat leaves in Examples 1-3 were significantly higher than those in Comparative Examples 1 and 2, while the MDA content was significantly lower. Example 2, in particular, showed the best performance among all indicators, demonstrating significant advantages in antioxidant protection and water retention. This result is attributed to the introduction of methyl salicylate as a plant signal activator in this invention, which can induce the expression of stress-related enzymes and enhance free radical scavenging ability. Simultaneously, calcium nitrate and zinc sulfate provide essential elements for enzyme activity, and the modified bentonite improves water absorption efficiency by optimizing the rhizosphere ionic environment, synergistically alleviating osmotic stress and oxidative damage. In contrast, Comparative Example 1 lacked the bentonite adsorption-regulating structure, resulting in limited osmotic regulation; Comparative Example 2 lacked signal activating components, leading to insufficient endogenous defense mechanisms in the plant.

[0095] 5. Final yield and field performance

[0096] Wheat was sown under controlled greenhouse conditions, and artificial salt-alkali stress conditions were established (soil pH approximately 8.5, electrical conductivity approximately 3.5 mS / cm). The entire cultivation period lasted 110 days until the grain-filling and maturity stages. Water-soluble fertilizers from Examples 1-3 and Comparative Examples 1-2 were applied, with three replicates per group and 10 wheat plants per group. At harvest, the number of effective tillers per plant (tillers forming ears) was counted, and the grains were harvested, dried, and weighed. The dry weight of grains per plant was recorded as a yield trait indicator. The results are shown in Table 5 below.

[0097] Table 5. Yield traits of wheat in different treatment groups

[0098] Processing group Number of effective tillers (per plant) Dry weight of seeds per plant (g) Example 1 3.8 2.91 Example 2 5.2 4.15 Example 3 4.5 3.62 Comparative Example 1 2.9 2.10 Comparative Example 2 3.1 2.34

[0099] As shown in Table 5, the number of effective tillers and the dry weight of grains per plant in the wheat treatment groups of Examples 1 to 3 were significantly higher than those in Comparative Example 1 and Comparative Example 2. Among them, the number of tillers in Example 2 reached 5.2 per plant and the dry weight of grains per plant was 4.15 g, showing the best yield traits.

[0100] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0101] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A stress-resistant water-soluble fertilizer for mitigating saline-alkali stress, characterized in that, It contains the following raw materials by weight: 40-65 parts of water-soluble macronutrients, 5-15 parts of mineral regulators, 3-12 parts of modified bentonite, 0.05-1.0 parts of plant signal activator, 3-10 parts of micronutrients, and 1-5 parts of water-soluble solubilizer and stabilizer.

2. The stress-resistant water-soluble fertilizer according to claim 1, characterized in that, The water-soluble macronutrients consist of ammonium nitrate, potassium dihydrogen phosphate, and potassium sulfate, with a mass ratio of ammonium nitrate: potassium dihydrogen phosphate: potassium sulfate = 1-2: 0.5-1.5: 1-2.

3. The stress-resistant water-soluble fertilizer according to claim 1, characterized in that, The mineral regulating factors include calcium nitrate, zinc sulfate, and potassium silicate, with a mass ratio of 1–2:0.5–1.5:0.5–1.

5.

4. The stress-resistant water-soluble fertilizer according to claim 1, characterized in that, The preparation method of the modified bentonite specifically includes the following steps: S101. After drying the bentonite under heating conditions, it is crushed and sieved to obtain pretreated bentonite; S102. Disperse the pretreated bentonite in deionized water, add 5% to 10% by mass of quaternary ammonium salt of bentonite, and react under heating and stirring conditions; S103. After washing the modified product until the conductivity is below the preset range, centrifuge and resuspend it in a mixture containing tetraethyl orthosilicate and an alkaline additive, and continue the reaction under constant temperature conditions. S104. The coated and modified bentonite is washed, dried and crushed to obtain the final modified bentonite product.

5. The stress-resistant water-soluble fertilizer according to claim 1, characterized in that: The plant signal activator is methyl salicylate; The trace element components include chelated boron, chelated iron, and magnesium sulfate; The water-soluble solubilizing stabilizer is selected from one or more of sodium citrate, polyaspartic acid, sodium lignosulfonate, and potassium sodium tartrate.

6. A method for preparing a stress-resistant water-soluble fertilizer for mitigating salt-alkali stress, wherein the stress-resistant water-soluble fertilizer is as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Add ammonium nitrate, potassium dihydrogen phosphate and potassium sulfate to pure water in sequence, stir and mix to form a basic nutrient solution; S2. Add calcium nitrate, zinc sulfate and potassium silicate to the basic nutrient solution in sequence, while keeping the mixture stirred continuously to form a compound nutrient system; S3. Slowly add the modified bentonite to the above mixture and disperse it evenly under the action of the stirring device to form a bentonite suspension system; S4. Add methyl salicylate, chelated boron, chelated iron and magnesium sulfate in sequence, stir and mix, then add water-soluble solubilizing stabilizer, and mix evenly to obtain the stress-resistant water-soluble fertilizer.

7. The method for preparing the stress-resistant water-soluble fertilizer according to claim 6, characterized in that, In step S3, the time for adding modified bentonite is controlled to be 10 to 30 minutes, and the stirring speed is maintained at 500 to 1000 revolutions per minute.

8. The method for preparing the stress-resistant water-soluble fertilizer according to claim 6, characterized in that, In step S4, after adding methyl salicylate and trace elements, continue stirring for 10-20 minutes, and then add a water-soluble solubilizing stabilizer.

9. The stress-resistant water-soluble fertilizer according to claim 1, characterized in that, The stress-resistant water-soluble fertilizer is a liquid preparation or a suspension preparation in which liquid and solid coexist.

10. The stress-resistant water-soluble fertilizer according to claim 1, characterized in that, The stress-resistant water-soluble fertilizer is suitable for fertigation via drip irrigation, spraying, or root irrigation.

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