A composite substrate for rice seedling raising and its preparation method

Abstract

This invention relates to the field of agricultural seedling cultivation technology, and discloses a special composite substrate for rice seedling cultivation and its preparation method. The method includes: preparing a special composite substrate for rice seedling cultivation using physical framework materials, deeply washed ammonium-potassium loaded modified porous minerals, anion-synergistic slow-dissolving sources, highly active trace element precursors, and mineral-derived potassium humate. The modified minerals undergo high-concentration ammonium-potassium ion exchange and deep washing to achieve low conductivity, constructing an ion-exchange nutrient pool under low-salt conditions. The trace element precursor is a manganese-iron oxide with a layered or needle-like structure. The preparation method employs a pre-mixing process of functional packages, framework wetting, and final encapsulation compounding. This invention solves the problems of initial salt damage and seedling burn, and later leaching and nutrient loss in existing substrates. It utilizes the synergistic effect of each component to enhance the substrate's physicochemical buffering capacity, promotes explosive root growth in seedlings, and improves seedling quality and mechanized transplanting survival rate.

Description

Technical Field

[0001] This invention relates to the field of agricultural seedling cultivation technology, specifically to a composite substrate for rice seedling cultivation and its preparation method. Background Technology

[0002] Factory-style rice seedling raising is a key step in achieving full mechanization of rice production. The seedling substrate, as the carrier for seedling growth, determines the quality of the seedlings and the survival rate after transplanting due to its physical and chemical properties. Currently, in order to meet the nutrient requirements of seedlings throughout the entire seedling raising cycle, conventional seedling substrates are prepared with a sufficient amount of fast-acting chemical fertilizers. However, this practice has the following problems in practical applications: On the one hand, the addition of fast-acting fertilizers will lead to an increase in the initial salt content (EC value) of the substrate, resulting in extremely high osmotic pressure, which will inhibit seed germination or cause seedling burn during the seedling stage; on the other hand, seedling substrates are mostly lightweight and porous materials with relatively weak fertilizer retention capacity compared to soil. If the initial fertilizer application is reduced for safety, nutrients are easily depleted due to leaching in the later stages of seedling raising, leading to nutrient deficiency, yellowing, and stunted growth in seedlings, making it difficult to achieve a balanced supply of nutrients throughout the entire cycle.

[0003] Furthermore, existing seedling substrates have shortcomings in terms of micronutrient supply and root environment regulation. Conventionally added inorganic micronutrient salts are easily lost with water or fixed and ineffective by the substrate, resulting in low bioavailability of micronutrients. This makes it difficult to meet the needs of the explosive growth of seedling roots, leading to poor root compaction, fewer white roots, and weak resistance, thus affecting the quality of mechanized transplanting. Simultaneously, existing substrate systems lack acid-base and ion buffers, making them prone to acidification, compaction, and drastic fluctuations in physicochemical properties under frequent spraying operations. This results in uneven seedling growth and difficulty in cultivating uniform and robust standardized seedlings. Therefore, this invention proposes a special composite substrate for rice seedling cultivation and its preparation method to address the shortcomings of existing technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a special composite substrate for rice seedling raising and its preparation method. It solves the contradiction between high salt burning of seedlings in the early stage and leaching and nutrient loss in the later stage caused by the addition of fast-acting fertilizers in existing seedling raising substrates, as well as the problems of poor root cohesion and uneven seedling quality caused by low micronutrient availability and weak physical and chemical buffering capacity of the substrate.

[0005] To achieve the above objectives, the present invention provides the following technical solution: Firstly, the present invention provides a composite substrate specifically for rice seedling raising, employing the following technical solution:

[0006] A composite substrate for rice seedling cultivation is made from the following raw materials in parts by weight: 70 to 95 parts of physical framework material; 10 to 20 parts of deeply washed ammonium potassium-loaded modified porous mineral; 3 to 6 parts of anionic synergistic slow-dissolving source; 1 to 2 parts of highly active trace element precursor; and 0.5 to 1.0 parts of mineral-derived potassium humate.

[0007] By adopting the above technical solution, this invention utilizes the synergistic effect of each component to construct a rhizosphere nutrient environment with high buffering capacity. Its core mechanism of action is as follows:

[0008] Constructing an ion-exchange nutrient pool: Deeply washed ammonium-potassium-loaded modified porous minerals serve as an intelligent nutrient pool. This component utilizes the lattice channels and high cation exchange capacity (CEC) of the porous minerals to pre-adsorb and load high concentrations of ammonium and potassium ions. During seedling cultivation, as rice roots secrete hydrogen ions, the ammonium and potassium nutrients locked within the lattice are slowly released through an ion exchange mechanism, achieving root-demand-driven release. This avoids initial high-salt-induced seedling burn and solves the later problems of yellowing and nutrient deficiency.

[0009] Synergistic regulation of anions and cations: Anions provide phosphate and sulfate ions as a slow-dissolving source, complementing the cation-modified minerals. Fluorapatite powder slowly releases phosphorus in the slightly acidic environment of the rhizosphere, while gypsum dihydrate provides calcium and sulfur and regulates local osmotic pressure. The combination of the two prevents drastic fluctuations in local pH caused by the dissolution of a single fertilizer.

[0010] Trace element redox activation: Highly active trace element precursors (manganese iron oxides) have layered or needle-like microstructures and abundant surface hydroxyl groups. They not only serve as trace element sources but also act as electron shuttles, promoting rhizosphere redox reactions and improving the root system's nutrient absorption efficiency.

[0011] Organic-inorganic bridging: Potassium humate from mineral sources acts as a biostimulant, forming an organic bridge between the physical framework and inorganic minerals, promoting the formation of aggregate structures, stimulating the growth of root meristems, and improving the root-binding capacity of seedlings.

[0012] Preferably, the physical framework material is a mixture of coconut coir, moss peat, and carbonized rice husk; the weight ratio of the coconut coir, the moss peat, and the carbonized rice husk is (4-6):(2-4):(1-3).

[0013] By adopting the above technical solution, utilizing the water retention of coconut coir, the air permeability of sphagnum peat, and the sterile rigid structure of carbonized rice husk, a suitable water-air coordinated pore structure was constructed. When the mass moisture content of the physical skeleton material was adjusted to 40% to 50%, the optimal air-liquid ratio of the substrate could be maintained, which is conducive to root respiration and root penetration.

[0014] Preferably, the deep-washed ammonium potassium-supported modified porous mineral is selected from one of natural clinoptilolite powder or montmorillonite powder;

[0015] The deeply washed ammonium-potassium supported modified porous mineral is a product obtained after ammonium and potassium ion exchange modification and deep washing to remove free salts. The degree of washing of the deeply washed ammonium-potassium supported modified porous mineral meets the following conditions:

[0016] The deeply washed ammonium potassium-supported modified porous minerals were dispersed in deionized water at a liquid-to-solid ratio of 5:1, stirred for 10 minutes, and filtered. The conductivity of the resulting filtrate was less than 200 μS / cm, or no precipitate was formed when 0.1 mol / L silver nitrate solution and 0.1 mol / L barium chloride solution were added to the resulting filtrate.

[0017] By adopting the above technical solution, deep washing is the key process control point of this invention. Direct mixing of conventional fertilizers will cause the substrate electrical conductivity (EC value) to rise instantly, inhibiting seed germination. This invention forces ammonium and potassium ions into the mineral lattice exchange sites through high-concentration modification, and then thoroughly removes the free salts (such as chloride ions, sulfate ions, etc.) remaining on the particle surface through deep washing. This treatment ensures that the substrate maintains high fertility while maintaining extremely low salinity, providing a safe germination environment for seedlings.

[0018] Preferably, the anionic synergistic slow-dissolving source is composed of fluorapatite micro powder and gypsum dihydrate micro powder; the weight ratio of fluorapatite micro powder to gypsum dihydrate micro powder is (1.5-2.5):1.

[0019] By adopting the above technical solution, fluorapatite is a poorly soluble phosphorus source, and its release is regulated by the feedback of rhizosphere pH. Gypsum dihydrate has slightly soluble properties. When the two are mixed in a specific ratio, they form a slightly soluble colloidal film under the condition of a moist substrate, which continuously and steadily replenishes phosphorus, calcium and sulfur elements to the soil solution. At the same time, calcium ions can replace some of the sodium ions adsorbed by soil colloids, thus improving the rhizosphere saline-alkali environment.

[0020] Preferably, the highly active trace element precursor is selected from one or a mixture of two of the following: hydrated manganese ore type trace element precursor and goethite type trace element precursor; the hydrated manganese ore type trace element precursor is a layered manganese oxide, and the goethite type trace element precursor is iron hydroxyl oxide.

[0021] By employing the above technical solutions, the bioavailability of trace elements can be improved using specific crystal structures:

[0022] Water-sodium manganese mineral precursor: It has a layered structure with moderate interlayer spacing. There are exchangeable metal cations and water molecules in the interlayer. It has redox activity and can decompose organic acid toxins secreted by roots, thus preventing root rot.

[0023] Goethite-type precursors: The surface is rich in active hydroxyl sites, which have specific adsorption and desorption capabilities for anions such as phosphate, and act as a nutrient buffer.

[0024] Preferably, the sodium manganese sulfate type trace element precursor is obtained by the following preparation process: acidified manganese sulfate monohydrate solution is slowly added dropwise to potassium permanganate solution, and an oxidation-reduction precipitation reaction is carried out at room temperature. After the reaction, the solution is aged for 10 to 14 hours, washed until the pH of the filtrate is 6.5 to 7.5 and no sulfate ions are detected, and finally dried under vacuum at 60°C to 70°C.

[0025] The goethite-type trace element precursor is obtained through the following preparation process: potassium hydroxide solution is added to ferric nitrate solution to adjust the pH value to 11.0 to 13.0, the resulting suspension is aged at 50°C to 70°C for 20 to 30 hours, and after the reaction, it is washed to neutral and dried at 70°C to 90°C.

[0026] By adopting the above technical solution, the crystal growth process of the precursor was controlled:

[0027] Regarding the sodium manganese ore type: the sodium manganese ore neutralization reaction pathway is adopted, the precipitation rate is controlled under acidic conditions, and with specific aging time and low-temperature vacuum drying, the collapse of the layered structure is avoided, and a large number of lattice defects and oxygen vacancies are retained, thereby endowing the material with chemical activity.

[0028] Regarding the goethite type: Nucleation is induced by a strong alkaline environment and aged for a long time under medium temperature conditions, which promotes the transformation of amorphous iron oxides into the thermodynamically more stable goethite crystal form, forming needle-like nanostructures with high specific surface area, increasing the contact area with the root system.

[0029] Secondly, the present invention provides a method for preparing a composite substrate specifically for rice seedling raising, employing the following technical solution:

[0030] A method for preparing a composite substrate specifically for rice seedling raising includes the following steps:

[0031] S1. Functional package premixing: The weighed deep-washed ammonium potassium-loaded modified porous mineral, the anion synergistic slow-dissolving source, the highly active trace element precursor and the mineral-derived potassium humate are added into a mixing device and mixed evenly to obtain functional masterbatch.

[0032] S2. Skeleton pretreatment: Each raw material in the physical skeleton material is put into a mixing device, and deionized water is added while mixing to adjust the mass moisture content of the physical skeleton material.

[0033] S3. Final compounding: Add the functional masterbatch powder obtained in step S1 to the moistened physical skeleton material processed in step S2, and continue stirring and mixing until the material is evenly dispersed.

[0034] By adopting the above technical solution, the present invention employs a specific process path of functional component premixing, skeleton wetting, and encapsulation compounding. First, the functional powder is premixed to form a master powder, ensuring the dispersion of trace components. Second, the moisture content of the physical skeleton is pre-adjusted to form a water film on the skeleton surface. Finally, the functional master powder is added to the wetted skeleton, and the surface tension of the water film is used to uniformly adhere the functional powder to the surface and pores of the physical skeleton, avoiding the problem of dry powder mixing and stratification, and ensuring that each matrix particle has complete nutrient release function.

[0035] Preferably, in step S2, the moisture content of the physical framework material is adjusted to 40% to 50% by mass;

[0036] In step S3, the mixing time is 5 to 10 minutes.

[0037] By adopting the above technical solution, a moisture content of 40% to 50% is the optimal critical range for powder adhesion. Too low a moisture content leads to dust dispersion and poor adhesion, while too high a moisture content causes material clumping and reduced air permeability. Controlling the stirring time to 5 to 10 minutes ensures both uniform mixing and avoids over-stirring which could damage the structural integrity of the physical framework materials (such as peat fiber and carbonized rice husk particles).

[0038] Preferably, the deep-washed ammonium-potassium supported modified porous mineral is prepared by the following process: preparing a mixed modified solution containing ammonium ions and potassium ions, wherein the concentration of ammonium ions is 1.5 mol / L to 2.0 mol / L and the concentration of potassium ions is 0.5 mol / L to 0.8 mol / L;

[0039] Natural porous mineral powder was added to the mixed modified liquid at a liquid-to-solid ratio of 4:1 to 6:1 (mL / g), and the mixture was heated to 50°C to 65°C and reacted at a constant temperature for 3 to 6 hours.

[0040] After the reaction is complete, filter the filter cake and redisperse it in deionized water for repeated washing until the conductivity of the filtrate from the last wash is less than 200 μS / cm. Dry the washed filter cake to constant weight and then crush and sieve it.

[0041] By adopting the above technical solution, the core mechanism of this process section lies in establishing a balance between high-concentration gradient-driven diffusion and thorough cleaning:

[0042] High-concentration modification: Setting a high-concentration ammonium and potassium ion environment (total concentration greater than 2 mol / L) and medium-temperature conditions (50℃-65℃) provides a strong chemical potential driving force, forcing ammonium and potassium ions to overcome diffusion resistance and penetrate deep into the micropores of natural minerals, replacing the originally adsorbed sodium, calcium and other ions, so that the minerals reach an ammonium and potassium saturation state.

[0043] Deep washing: By repeatedly washing until the conductivity is below 200 μS / cm, free salts are removed from the outside of the pores and the macropores. This step transforms the salt-type matrix into an ion-exchange matrix, eliminating the risk of high salt damage to the matrix, while retaining long-lasting nutrients inside the crystal lattice.

[0044] Preferably, the highly active trace element precursor is subjected to physical grinding and classification.

[0045] The specific requirements for the physical grinding and grading process are as follows: the dried high-activity trace element precursor is ground and sieved, and its particle size is controlled to pass through a 300-mesh to 500-mesh sieve.

[0046] By adopting the above technical solutions, efficient activation pathways for manganese and iron were constructed respectively. Grinding through a 300-500 mesh sieve ensured that the precursor powder had a micron-sized particle size, which could provide a relatively larger reaction surface area after being mixed into the matrix, thereby improving the dissolution kinetic rate of trace elements in the rhizosphere environment.

[0047] This invention provides a composite substrate specifically for rice seedling cultivation and its preparation method. It has the following beneficial effects:

[0048] 1. This invention solves the contradiction between high fertility and high salt damage in traditional seedling substrates by introducing deeply washed ammonium-potassium loaded modified porous minerals. The deeply washed ammonium-potassium loaded modified porous minerals, after high-concentration ion exchange saturation and deep washing treatment, create an initial environment with extremely low background salinity in the substrate, which improves the high germination rate of rice seeds. At the same time, the ammonium and potassium ions locked in the mineral lattice are released only through the ion exchange mechanism when the roots secrete hydrogen ions, realizing the on-demand supply of nutrients and avoiding seedling burn in the seedling stage and nutrient deficiency and yellowing in the later stage of seedlings.

[0049] 2. This invention utilizes the synergistic effect of highly active trace element precursors and mineral-derived potassium humate to enhance the bioavailability of trace elements and the stress resistance of roots. The specially formulated layered or needle-like micro / nano structure precursors have abundant surface active sites and excellent redox activity, which can dynamically regulate the redox potential of the rhizosphere microenvironment and promote the absorption of elements such as iron and manganese. Combined with the biostimulatory effect of mineral-derived potassium humate, it can stimulate the growth of root meristems, resulting in whiter, more abundant, and stronger root-binding ability in seedlings, thereby improving the transplant survival rate.

[0050] 3. This invention constructs a matrix system with physicochemical buffering capacity by combining physical framework materials with anionic synergistic slow-dissolving sources. The specific ratio of coconut coir, peat, and carbonized rice husks forms a stable water-air coordinated pore structure, while the slightly soluble system formed by fluorapatite and gypsum dihydrate can continuously buffer the pH fluctuations of the matrix and simultaneously supplement the macro-elements of phosphorus, calcium, and sulfur, preventing matrix acidification and structural compaction caused by leaching during seedling cultivation, and improving the uniformity and robustness of the seedling population. Detailed Implementation

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to preparation examples, examples, comparative examples, and test examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0052] Preparation Examples 1-5:

[0053] Preparation Example 1:

[0054] This preparation example provides a deeply washed ammonium-potassium supported modified zeolite (component B). Deionized water was added to a reaction vessel to dissolve ammonium sulfate and potassium chloride, preparing a mixed modified solution with an ammonium ion concentration of 1.8 mol / L and a potassium ion concentration of 0.6 mol / L. Natural clinoptilolite powder (100-200 mesh) was added to the modified solution at a liquid-to-solid ratio of 5:1 (mL / g). Stirring was started and the system was heated to 60°C and reacted at a constant temperature for 4 hours. After the reaction was completed, the mixture was filtered, and the filter cake was redispersed in deionized water (liquid-to-solid ratio 5:1), stirred for 10 minutes, and then filtered again. This washing operation was repeated 5 times. The filtrate from the last wash was tested. No white precipitate was produced when 0.1 mol / L silver nitrate solution was added, and no white precipitate was produced when 0.1 mol / L barium chloride solution was added. The washed filter cake was dried at 105°C to constant weight, pulverized, and passed through a 100-mesh sieve to obtain component B.

[0055] Preparation Example 2:

[0056] This preparation example provides a deeply washed ammonium-potassium supported modified zeolite (component B). Deionized water is added to a reaction vessel to dissolve ammonium sulfate and potassium chloride, preparing a mixed modified solution with an ammonium ion concentration of 1.5 mol / L and a potassium ion concentration of 0.5 mol / L. Natural clinoptilolite powder (100-200 mesh) is added to the modified solution at a liquid-to-solid ratio of 4:1 (mL / g). Stirring is started and the system is heated to 50°C and reacted at a constant temperature for 6 hours. After the reaction is completed, the mixture is filtered, and the filter cake is redispersed in deionized water (liquid-to-solid ratio 5:1), stirred for 10 minutes, and then filtered again. This washing operation is repeated until the conductivity of the final washing filtrate is less than 200 μS / cm. The washed filter cake is dried at 105°C to constant weight, pulverized, and passed through a 100-mesh sieve to obtain component B.

[0057] Preparation Example 3:

[0058] This preparation example provides a deep-washed ammonium-potassium supported modified montmorillonite (an alternative embodiment of component B). Deionized water is added to a reactor to dissolve ammonium sulfate and potassium chloride, preparing a mixed modification solution with an ammonium ion concentration of 2.0 mol / L and a potassium ion concentration of 0.8 mol / L. Montmorillonite powder (passed through 200 mesh) is added to the above modification solution at a liquid-to-solid ratio of 6:1 (mL / g). Stirring is started and the system is heated to 65°C and reacted at a constant temperature for 3 hours. After the reaction is completed, the mixture is filtered. The filter cake is redispersed in deionized water (liquid-to-solid ratio of 5:1), stirred for 15 minutes, and then filtered again. This washing operation is repeated until no free chloride ions or sulfate ions are detected in the final washing filtrate. The washed filter cake is dried at 105°C to constant weight, pulverized and dispersed, and passed through a 100-mesh sieve to obtain the modified montmorillonite product.

[0059] Preparation Example 4:

[0060] This preparation example provides a highly active sodium manganese ore-type trace element precursor (component D). 22.5 g of potassium permanganate was dissolved in 400 mL of deionized water to prepare solution A. Separately, 32.5 g of manganese sulfate monohydrate was dissolved in 150 mL of deionized water, and 12 mL of concentrated hydrochloric acid was added to adjust the acidity to prepare solution B. Under room temperature and stirring at 450 rpm, solution B was slowly added dropwise to solution A at a rate of 8 mL / min. After the addition was complete, stirring continued for 30 minutes, followed by standing and aging for 12 hours. The black precipitate was collected by filtration and repeatedly washed with deionized water until the pH of the filtrate was 7.0 and no sulfate ions were detected. The filter cake was vacuum dried at 65°C for 12 hours and then ground through a 400-mesh sieve to obtain sodium manganese ore powder.

[0061] Preparation Example 5:

[0062] This preparation example provides a goethite-type trace element precursor (an alternative embodiment of component D). 500 mL of a 1.0 mol / L ferric nitrate solution was prepared, and a 5.0 mol / L potassium hydroxide solution was slowly added to it while continuously stirring until the pH of the system reached 12.0. The resulting reddish-brown suspension was transferred to a polytetrafluoroethylene-lined high-pressure reactor and aged at 60°C for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the precipitate was repeatedly washed with deionized water until the filtrate was neutral. The filter cake was dried at 80°C for 24 hours and ground through a 400-mesh sieve to obtain goethite powder.

[0063] Examples 1-4:

[0064] Example 1:

[0065] This embodiment provides a composite substrate for rice seedling raising based on a dual response mechanism of rhizosphere pH-Eh (the combined effect of acidity / alkalinity and redox potential), comprising the following raw materials in parts by weight: 80 parts of physical framework material (component A), 15 parts of deeply washed ammonium potassium-loaded modified zeolite (obtained in Preparation Example 1), 4.5 parts of anionic synergistic slow-dissolving source (component C), 1.5 parts of highly active sodium manganese ore-type trace element precursor (obtained in Preparation Example 4), and 0.8 parts of mineral-derived potassium humate (component E). The physical framework material is composed of coconut coir, sphagnum peat, and carbonized rice husk in a weight ratio of 5:3:2; the anionic synergistic slow-dissolving source is composed of fluorapatite micro powder and gypsum dihydrate micro powder in a weight ratio of 2:1.

[0066] The preparation method of this embodiment includes the following steps:

[0067] Functional package premix: Weigh the deep-washed ammonium potassium-supported modified zeolite, anionic synergistic slow-dissolving source, highly active sodium manganese ore-type trace element precursor and mineral-derived potassium humate into a three-dimensional motion mixer and mix at 20 rpm for 15 minutes to obtain functional masterbatch.

[0068] Skeleton pretreatment: Coconut coir, moss peat and carbonized rice husks are added into a horizontal ribbon mixer in proportion. Deionized water is added by spraying while mixing to adjust the material moisture content to 45%.

[0069] Final compounding: Evenly sprinkle the functional masterbatch powder obtained in the functional package premixing step into the moist skeleton material after the skeleton pretreatment step, and continue to stir and mix for 8 minutes until the material is evenly dispersed and free of agglomeration.

[0070] Packaging: The mixed matrix is ​​metered, dispensed, and sealed.

[0071] Example 2:

[0072] This embodiment provides a composite substrate for rice seedling raising based on a dual response mechanism of rhizosphere pH-Eh, focusing on a high skeleton ratio formulation, comprising the following raw materials in parts by weight: 95 parts of physical skeleton material (component A), 10 parts of deeply washed ammonium potassium-loaded modified zeolite (obtained in preparation example 2), 3 parts of anionic synergistic slow-dissolving source (component C), 1 part of highly active sodium manganese ore-type trace element precursor (obtained in preparation example 4), and 0.5 parts of mineral-derived potassium humate (component E). The physical skeleton material is composed of coconut coir, sphagnum peat, and carbonized rice husk in a weight ratio of 5:3:2; the anionic synergistic slow-dissolving source is composed of fluorapatite micro powder and gypsum dihydrate micro powder in a weight ratio of 2:1.

[0073] The preparation method of this embodiment includes the following steps:

[0074] Functional package premix: Weigh the deep-washed ammonium potassium-supported modified zeolite, anionic synergistic slow-dissolving source, highly active sodium manganese ore-type trace element precursor and mineral-derived potassium humate into a V-type mixer and mix at 15 rpm for 10 minutes to obtain functional masterbatch.

[0075] Skeleton pretreatment: Put all raw materials of the physical skeleton material into a mixer, and spray water to adjust the mass moisture content to 40%;

[0076] Final compounding: Add the functional masterbatch to the moistened skeleton material and stir for 5 minutes;

[0077] Packaging: The mixed matrix is ​​metered, dispensed, and sealed;

[0078] Example 3:

[0079] This embodiment provides a special composite substrate for rice seedling raising based on the rhizosphere pH-Eh dual response mechanism, focusing on a high nutrient reserve formula, and using modified montmorillonite and goethite, including the following raw materials in parts by weight: physical framework material (component A) 70 parts, deep-washed ammonium potassium-loaded modified montmorillonite (obtained in preparation example 3) 20 parts, anionic synergistic slow-dissolving source (component C) 6 parts, goethite-type trace element precursor (obtained in preparation example 5) 2 parts, mineral-derived potassium humate (component E) 1.0 part, wherein the physical framework material is composed of coconut coir, sphagnum peat, and carbonized rice husk in a weight ratio of 5:3:2; the anionic synergistic slow-dissolving source is composed of fluorapatite micro powder and gypsum dihydrate micro powder in a weight ratio of 2:1.

[0080] The preparation method of this embodiment includes the following steps:

[0081] Functional package premix: Weigh the deep-washed ammonium potassium-loaded modified montmorillonite, anionic synergistic slow-dissolving source, goethite-type trace element precursor and mineral-derived potassium humate into a mixer and mix at 25 rpm for 15 minutes to obtain functional masterbatch.

[0082] Skeleton pretreatment: Put all raw materials of the physical skeleton into a mixer and spray water to adjust the moisture content to 50% by mass;

[0083] Final compounding: Add the functional masterbatch to the moistened skeleton material and stir for 10 minutes;

[0084] Packaging: The mixed matrix is ​​metered, dispensed, and sealed;

[0085] Example 4:

[0086] This embodiment provides a composite substrate for rice seedling raising based on a rhizosphere pH-Eh dual response mechanism. It adopts a mixed Eh (redox potential) response component, including the following raw materials in parts by weight: 85 parts of physical framework material (component A), 12 parts of deeply washed ammonium potassium-loaded modified zeolite (obtained in Preparation Example 1), 4 parts of anionic synergistic slow-dissolving source (component C), 1.5 parts of trace element precursor composition, and 0.6 parts of mineral-derived potassium humate (component E). The physical framework material is composed of coconut coir, sphagnum peat, and carbonized rice husk in a weight ratio of 5:3:2; the anionic synergistic slow-dissolving source is composed of fluorapatite micro powder and gypsum dihydrate micro powder in a weight ratio of 2:1; and the trace element precursor composition is composed of a highly active sodium manganese ore type trace element precursor (obtained in Preparation Example 4) and a goethite type trace element precursor (obtained in Preparation Example 5) in a weight ratio of 1:1.

[0087] The preparation method of this embodiment includes the following steps:

[0088] Functional package premix: The raw materials of each functional component are put into a mixer and mixed evenly to obtain functional masterbatch;

[0089] Skeleton pretreatment: Put all raw materials of the physical skeleton material into a mixer, and spray water to adjust the mass moisture content to 45%;

[0090] Final compounding: Add the functional masterbatch to the moistened skeleton material and stir for 8 minutes;

[0091] Packaging: The mixed matrix is ​​metered, dispensed, and sealed.

[0092] Comparative Examples 1-5:

[0093] Comparative Example 1: Compared with Example 1, the difference is that components B, C and D are not added. Instead, urea, superphosphate and potassium sulfate powder with the same total nitrogen, total phosphorus and total potassium content as in Example 1 are added to the physical framework material. All other aspects are the same.

[0094] Comparative Example 2: Compared with Example 1, the difference is that components B, C and D are not added. Instead, a commercially available resin-coated compound slow-release fertilizer with a total nutrient content equivalent to that in Example 1 is added to the physical framework material. All other aspects are the same.

[0095] Comparative Example 3: Compared with Example 1, the difference is that the deep washing and desalination step of component B was omitted in the preparation process. That is, after the natural clinoptilolite powder undergoes ion exchange reaction, only solid-liquid separation is performed. It is not repeatedly washed with deionized water. The filter cake with residual mother liquor is directly dried, crushed and used. Everything else is the same.

[0096] Comparative Example 4: Compared with Example 1, the difference is that commercially available manganese sulfate monohydrate powder with an equivalent manganese content was used to replace component D (highly active sodium manganese ore type trace element precursor), and all other aspects are the same.

[0097] Comparative Example 5: Compared with Example 1, the difference is that component D (highly active sodium manganese ore type trace element precursor) was not added, and all other aspects are the same.

[0098] Test Example 1-2:

[0099] Test Example 1: Verification of Matrix Physicochemical Properties and Response Mechanism

[0100] pH-responsive static leaching experiment: 100.0 g of the composite matrix sample prepared in Example 1 was packed into a 5 cm inner diameter glass chromatography column, with a quartz sand filter bed at the bottom. Four sets of eluents were prepared, and the pH of deionized water was adjusted to 7.0, 6.0, 5.0, and 4.0 using hydrochloric acid and sodium hydroxide, respectively. The matrix column was continuously eluted at a flow rate of 2.5 mL / min, and the eluent was collected. Elution was stopped when the eluent volume reached 500 mL. The concentration of ammonium nitrogen in the eluent was determined by the Kjeldahl method, and the concentration of potassium ions was determined by flame photometry. Each treatment was repeated three times, and the average value was taken.

[0101] For the redox potential (Eh) response and trace element release experiments, 200.0 g of each of the matrix samples prepared in Example 1, Comparative Example 4, and Comparative Example 5 were placed in 500 mL wide-mouth bottles, and deionized water was added until the liquid level was 2 cm above the matrix surface to create a submerged environment. High-purity nitrogen gas was continuously purged into the bottles for 30 minutes to remove dissolved oxygen. The bottles were then sealed and placed in a 25°C constant temperature incubator in the dark to simulate the rhizosphere reducing environment during rice seedling cultivation. On days 0, 3, 7, and 14 of cultivation, the redox potential (Eh value) of the matrix slurry was measured using a portable ORP meter (platinum electrode). At the same time, the supernatant was extracted, filtered, and the concentration of water-soluble manganese ions in the solution was measured using an atomic absorption spectrophotometer.

[0102] Experimental data:

[0103] Table 1. Detection data of cumulative nitrogen and potassium release in the matrix of Example 1 under different pH rinsing conditions

[0104]

[0105] Table 2. Data on the changes in matrix redox potential and water-soluble manganese ion concentration under simulated flooding anaerobic conditions.

[0106]

[0107] Conclusion Analysis:

[0108] Based on the data analysis in Table 1, the substrate of Example 1 exhibited extremely low nitrogen and potassium leaching rates under a neutral environment of pH 7.0. This indicates that after deep washing, component B removed physically adsorbed free salts, resulting in low background release and avoiding salt stress in the early stages of seedling cultivation. As the pH of the leaching solution decreased (simulating increased proton secretion from root systems), the release of ammonium nitrogen and potassium ions showed a significant non-linear increasing trend. This confirms that the zeolite loaded with ammonium and potassium in the substrate has a hydrogen-metal ion exchange mechanism, and nutrient release is dominated by environmental acidity, exhibiting rhizosphere pH response characteristics.

[0109] Analysis of the data in Table 2 shows that the redox potential values ​​of all groups decreased over time during the anaerobic culture process. Comparative Example 5, lacking high-valence manganese iron oxides and electron acceptor buffering, experienced a rapid drop in Eh value to a strongly reducing state below -200mV. Example 1, with the addition of a highly active sodium manganese oxide-type trace element precursor (component D), showed a relatively gradual decrease in redox potential, remaining near a positive value on day 14. This indicates that component D, acting as an electron acceptor, consumed environmental reducing power and buffered the rhizosphere redox potential.

[0110] Regarding the characteristics of manganese ion release, Comparative Example 4 used readily soluble manganese sulfate, with an initial concentration as high as 185.43 mg / L, far exceeding the suitable range for rice seedlings and easily causing manganese poisoning. In Example 1, the manganese ion concentration slowly increased with the extension of cultivation time (i.e., the degree of reduction deepened), reaching 15.62 mg / L on the 14th day. This satisfied the supply of trace elements while avoiding the toxicity of instantaneous high concentrations. This indicates that component D underwent reductive dissolution under reducing conditions, achieving Eh-responsive on-demand release of trace elements. Meanwhile, in Example 1, the manganese ion concentration did not increase linearly with the reduction of component D. It is speculated that some of the released manganese ions were re-adsorbed and buffered by component B (modified zeolite) through ion exchange, verifying the synergistic regulation mechanism among components within the system.

[0111] Test Example 2: Rice Seedling Pot Experiment

[0112] Experimental method: The japonica rice variety “Nanjing 9108” was selected as the test crop. Standard machine-transplanted seedling trays with a size of 58cm×28cm×3cm were used. The substrates prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were filled into the seedling trays respectively, with a filling thickness of 2.0cm-2.5cm in each tray.

[0113] Soak and germinate the rice seeds until they sprout. Sow 120g (dry weight) per tray. After sowing, cover with a 0.5cm thick substrate and spray with water until saturated. Place all seedling trays in the same plastic greenhouse for seedling management. Control the daytime temperature to 25℃-30℃ and the nighttime temperature to 15℃-20℃. Keep the trays moist during the seedling period and do not apply any additional fertilizer.

[0114] On the 7th day after sowing, the number of seedlings was counted and the emergence rate was calculated. On the 25th day of seedling raising (the suitable transplanting period), 3 trays were randomly selected from each treatment, and 20 seedlings were randomly selected from each tray to measure the plant height (from the base to the highest leaf tip) and the stem base width (the width of the stem base in the flat direction).

[0115] To measure root cohesion force: Lift the seedling block as a whole, keeping one end suspended in the air, and measure the tensile force required for the seedling block to break. Alternatively, use a digital push-pull force gauge to lift the seedling vertically upwards until the seedling block leaves the ground or breaks, and record the maximum peak force.

[0116] The second leaf from the top of the seedlings was collected, washed, blanched, dried, and digested. The manganese content of the leaves was then determined using inductively coupled plasma mass spectrometry (ICP-MS).

[0117] Experimental data:

[0118] Table 3. Detection data of agronomic traits and physiological indicators of rice seedlings in each group.

[0119]

[0120] Conclusion Analysis:

[0121] Analysis of the data in Table 3 shows that the germination rate directly reflects the initial salt safety of the substrate. The germination rates of Comparative Example 1 (with added fast-acting fertilizer) and Comparative Example 3 (with unwashed component B) were both below 75%, significantly lower than those of the Example group. This confirms that residual free salts in fast-acting fertilizers or unwashed modified zeolite can cause high osmotic pressure, leading to difficulty in seed water absorption or seedling dehydration and burn. Examples 1, 2, 3, and 4 used deeply washed ion exchange components to construct a low-salt background, with germination rates all exceeding 90%, verifying the necessity of the pretreatment process.

[0122] Regarding seedling quality, the plant height of the example group remained stable between 15.4cm and 17.2cm, within the optimal height range for machine transplanting. Combined with a relatively thick stem base, this exhibited the characteristics of short, sturdy, and high-quality seedlings. In contrast, Comparative Examples 1 and 3, affected by initial high salt stress, showed significantly inhibited plant height (12.1cm and 13.5cm respectively), exhibiting stunted growth. While Comparative Example 4 had a plant height close to the normal range, its stem base was thin and weak, resulting in insufficient biomass accumulation. Furthermore, the stem base width and root cohesion index of the example group were superior to those of Comparative Example 2 (conventional slow-release fertilizer). Conventional slow-release fertilizer's nutrient release is mainly controlled by temperature and moisture, resulting in a low degree of temporal and spatial matching with root growth. The example substrate, however, utilizes hydrogen ions secreted by the roots to drive nutrient release, forming a localized nutrient-rich zone in the dense root area (i.e., a region with high hydrogen ion concentration), inducing further root proliferation and cohesion, significantly improving root cohesion and meeting the requirements of machine transplanting for the integrity of the seedling block.

[0123] Regarding micronutrient regulation, the manganese content in the leaves of Comparative Example 4 (with added soluble manganese) reached as high as 985.6 mg / kg, which is close to or exceeds the manganese toxicity threshold of rice. Moreover, its stem base is wide and thin, showing a toxicity inhibition effect. The manganese content in the leaves of Comparative Example 5 (without manganese source) was only 34.2 mg / kg, which is on the verge of nutrient deficiency. The manganese content in the leaves of Example 1 was 215.3 mg / kg, which is within the suitable nutrient range. This indicates that component D releases manganese ions in a controlled manner under the rhizosphere reducing environment, which avoids the toxicity caused by high concentration dissolution in the early stage and prevents nutrient deficiency in the later stage. This verifies the effectiveness and safety of the Eh-responsive micronutrient precursor.

Claims

1. A composite substrate specifically for rice seedling raising, characterized in that, Made from the following ingredients in parts by weight: 70 to 95 parts of physical framework material; 10 to 20 parts of deeply washed ammonium potassium-supported modified porous minerals; 3 to 6 parts of anionic synergistic slow-dissolving source; 1 to 2 parts of highly active trace element precursors; 0.5 to 1.0 parts of mineral-derived potassium humate; The deep-washed ammonium potassium-loaded modified porous mineral is selected from either natural clinoptilolite powder or montmorillonite powder. The deep-washed ammonium-potassium loaded modified porous mineral is a product that has been modified by ammonium ion and potassium ion exchange and then deep-washed to remove free salts. The washing degree of the deeply washed ammonium potassium-supported modified porous minerals meets the following conditions: the deeply washed ammonium potassium-supported modified porous minerals are dispersed in deionized water at a liquid-to-solid ratio of 5:1, stirred for 10 minutes, and filtered. The conductivity of the resulting filtrate is less than 200 μS / cm, or no precipitation is produced when 0.1 mol / L silver nitrate solution and 0.1 mol / L barium chloride solution are added to the resulting filtrate. The anion-synergistic slow-dissolving source is a mixture of fluorapatite micro powder and gypsum dihydrate micro powder; The weight ratio of the fluorapatite micro powder to the gypsum dihydrate micro powder is (1.5-2.5):1; The highly active trace element precursor is selected from one or a mixture of two of the following: sodium manganese ore type trace element precursor and goethite type trace element precursor. The sodium manganese ore type trace element precursor is a layered manganese oxide, and the goethite type trace element precursor is iron hydroxide. The sodium manganese ore-type trace element precursor is a product obtained through the following preparation process: Acidified manganese sulfate monohydrate solution was slowly added dropwise to potassium permanganate solution to carry out redox precipitation reaction at room temperature. After the reaction, the solution was aged for 10 to 14 hours, washed until the pH of the filtrate was 6.5 to 7.5 and no sulfate ions were detected, and finally dried under vacuum at 60 to 70°C to obtain the final product. The goethite-type trace element precursor is obtained through the following preparation process: potassium hydroxide solution is added to ferric nitrate solution to adjust the pH value to 11.0 to 13.0, the resulting suspension is aged at 50°C to 70°C for 20 to 30 hours, and after the reaction, it is washed to neutral and dried at 70°C to 90°C.

2. The composite substrate for rice seedling raising according to claim 1, characterized in that, The physical framework material is a mixture of coconut coir, moss peat, and carbonized rice husks; The weight ratio of the coconut coir, the moss peat, and the carbonized rice husk is (4-6):(2-4):(1-3).

3. A method for preparing the composite substrate for rice seedling raising as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Functional package premixing: Weigh the deep-washed ammonium potassium-loaded modified porous minerals, anionic synergistic slow-dissolving source, highly active trace element precursor and mineral-derived potassium humate into the mixing equipment and mix evenly to obtain functional masterbatch. S2. Skeleton pretreatment: Put each raw material in the physical skeleton material into the mixing equipment, and add deionized water while mixing to adjust the mass moisture content of the physical skeleton material. S3. Final compounding: Add the functional masterbatch powder obtained in the functional package premixing step to the moistened physical skeleton material after the skeleton pretreatment step, and continue stirring and mixing until the material is evenly dispersed.

4. The method for preparing a composite substrate specifically for rice seedling raising according to claim 3, characterized in that, In step S2, the moisture content of the physical framework material is adjusted to 40% to 50%. In step S3, the mixing time is 5 to 10 minutes.

5. The method for preparing a composite substrate specifically for rice seedling raising according to claim 3, characterized in that, The deep-washed ammonium potassium-supported modified porous mineral is prepared through the following process: Prepare a mixed modified solution containing ammonium ions and potassium ions, wherein the concentration of ammonium ions is 1.5 mol / L to 2.0 mol / L and the concentration of potassium ions is 0.5 mol / L to 0.8 mol / L; Natural porous mineral powder is added to the mixed modified liquid at a liquid-solid ratio of 4:1 to 6:1, and the mixture is heated to 50°C to 65°C and reacted at a constant temperature for 3 to 6 hours. After the reaction is complete, filter the filter cake and redisperse it in deionized water for repeated washing until the conductivity of the filtrate from the last wash is less than 200 μS / cm. Dry the washed filter cake to constant weight and then crush and sieve it.

6. The method for preparing a composite substrate specifically for rice seedling raising according to claim 3, characterized in that, The highly active trace element precursor was subjected to physical grinding and classification. The specific requirements for the physical grinding and grading process are as follows: the dried high-activity trace element precursor is ground and sieved, and the particle size of the high-activity trace element precursor is controlled to pass through a 300-mesh to 500-mesh sieve.

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