A rice machine transplanting strong seedling cultivation method based on a special seedling raising substrate

Abstract

The application provides a rice machine transplanting strong seedling cultivation method based on a special seedling raising substrate, the special seedling raising substrate is added with modified chitosan, the modified chitosan is obtained by the reaction of chitosan-diethylenetriamine pentaacetic acid coupling and maleic anhydride, and then copolymerization with methacryloyloxyethyl trimethyl ammonium chloride and N,N'-methylene bisacrylamide. After the modified chitosan is added into the seedling raising substrate, the three-dimensional network can store and slowly release water, and continuously supply water for seed germination; meanwhile, the three-dimensional network is closely combined with diatomite and bentonite through hydrogen bond, electrostatic adsorption and other effects, so that the water retention and ventilation performance of the substrate is optimized; the polycarboxyl structure cooperates with humic acid to chelate trace elements, so that the nutrient availability is improved; and the quaternary ammonium salt cation is adsorbed on the surface of clay minerals, so that the antibacterial capacity is enhanced, and seed rot and diseases are reduced.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, specifically to a method for cultivating robust rice seedlings by machine transplanting based on a special substrate for seedling raising. Background Technology

[0002] Currently, scholars both domestically and internationally have conducted extensive research on rice seedling raising substrates for machine transplanting, and numerous commercial seedling raising substrate products have emerged in the market. In terms of substrate type, existing technologies mainly include organic-inorganic composite substrates, agricultural waste (such as straw and mushroom residue) substrates, and soilless lightweight substrates. Common basic components include peat, vermiculite, perlite, bentonite, and organic fertilizers. In recent years, some studies have begun to explore adding functional materials such as chitosan, water-retaining agents, and root-promoting agents to the substrate to improve its water and fertilizer retention properties and the seedling growth environment. Regarding seedling raising effects, existing substrates have a certain effect on improving seedling quality, but there is still significant room for improvement in seedling survival rate and seedling uniformity, especially in consistently cultivating robust seedlings that meet the requirements for machine transplanting.

[0003] However, existing rice seedling raising substrates still face many shortcomings in practical applications. First, the seedling raising effects of existing substrate products are inconsistent, with generally low seedling survival rates and uneven seedling growth being prominent issues, making it difficult to meet the requirements of large-scale mechanized rice transplanting production in terms of seedling vigor. Second, the functional integration of substrate formulations is not high, and the synergistic effects in water retention, root promotion, and antibacterial properties need to be strengthened. Third, the cost of commercially available substrates is relatively high, and the seedling quality of some products is unstable. Therefore, there is an urgent need to develop a dedicated seedling raising substrate that combines high seedling survival rates and high seedling uniformity to meet the needs of large-scale rice transplanting applications.

[0004] In conclusion, a new technical solution is urgently needed to address the problems existing in the current technology. Summary of the Invention

[0005] Based on this, the present invention provides a method for cultivating robust rice seedlings by machine transplanting using a special seedling substrate. The special seedling substrate incorporates modified chitosan, which is obtained by reacting chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride, followed by copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide. After being added to the seedling substrate, the modified chitosan's three-dimensional network can store and slowly release moisture, providing a continuous water supply for seed germination. Simultaneously, it tightly binds with diatomaceous earth and bentonite through hydrogen bonding and electrostatic adsorption, optimizing the substrate's water retention and aeration properties. The multi-carboxyl structure synergistically chelates trace elements with humic acid, improving nutrient availability. Quaternary ammonium salt cations adsorb onto the surface of clay minerals, enhancing antibacterial capabilities and reducing seed rot and diseases.

[0006] One object of the present invention is to provide a special substrate for seedling raising, the special substrate for seedling raising comprising the following components in parts by weight: 20-40 parts diatomaceous earth 10-20 parts of aminated bentonite 5-20 parts peat 5-20 parts organic fertilizer Inorganic fertilizer 0.1-1 part 0.1-0.5 parts humic acid 10-20 parts of modified chitosan; in, The modified chitosan is obtained by reacting chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride, followed by copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide.

[0007] Furthermore, the organic fertilizer is selected from one or more of livestock and poultry manure and agricultural waste fermentation products.

[0008] Furthermore, the inorganic fertilizer is selected from one or more of nitrogen fertilizer, phosphorus fertilizer, and potassium fertilizer, or a compound fertilizer containing two or more of nitrogen, phosphorus, and potassium elements.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned seedling-specific substrate, comprising the following steps: S1. Chitosan-diethylenetriaminepentaacetic acid coupling compound and maleic anhydride are mixed and reacted under an inert atmosphere and heated to obtain an intermediate product. S2. The intermediate product, methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide are blended together, an initiator is added, and the mixture is heated under an inert atmosphere to obtain modified chitosan. S3. Mix all components thoroughly to obtain a seedling substrate.

[0010] Further, the chitosan-diethylenetriaminepentaacetic acid coupling compound of the present invention is referenced in: Zhang Shuxiu, Chen Shuhui, Zhang Shouguo, et al. Study on the removal of uranium from the body surface by chitosan-diethylenetriaminepentaacetic acid coupling compound film agent [J]. Military Medicine, 2025, 49(12):905-911.

[0011] Preferably, the preparation method of chitosan-diethylenetriaminepentaacetic acid coupling compound includes the following steps: One part (by weight, the same below) of chitosan was added to 100 parts of acetic acid aqueous solution (volume ratio of 1%) and stirred to dissolve, thus obtaining a chitosan solution. 0.1 parts of diethylenetriaminepentaacetic acid (DTA) was added to 15 parts of water and stirred to dissolve. The pH was adjusted to neutral with 1 wt% sodium hydroxide aqueous solution to obtain a DTA solution. 0.355 parts of NHS and 0.448 parts of EDC were added to the DTA solution and stirred in an ice bath for 30 min. Under ice bath and stirring, the chitosan solution was added dropwise to the DTA solution, and the pH of the reaction system was maintained at 4 with 1% acetic acid aqueous solution (volume ratio). After the addition was complete, the reaction system was placed at 4℃ for 12 h, then placed in a dialysis bag with a molecular weight cutoff of 3500 and dialyzed with deionized water for 48 h, changing the dialysate every 8 h. After dialysis, the solution was centrifuged, the supernatant was collected, and freeze-dried to obtain the chitosan-DTA conjugate.

[0012] Further, in step S1, the mass ratio of the chitosan-diethylenetriaminepentaacetic acid coupling compound to maleic anhydride is 1:(0.1-0.5).

[0013] Furthermore, in step S1, the temperature of the heating reaction is 90-110°C.

[0014] Further, in step S2, the mass ratio of the intermediate product, methacryloyloxyethyltrimethylammonium chloride, and N,N'-methylenebisacrylamide is 1:(0.1-0.9):(0.1-0.5).

[0015] Furthermore, in step S2, the temperature of the heating reaction is 60-80°C.

[0016] Another object of the present invention is to provide the application of the seedling-specific substrate in rice seedling cultivation.

[0017] The present invention has the following beneficial effects: This invention provides a method for cultivating robust rice seedlings by machine transplanting based on a special seedling substrate, wherein modified chitosan is used in the seedling substrate. The invention first reacts a chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride to introduce carbon-carbon double bonds into the molecular chain; finally, it undergoes free radical copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide under the action of an initiator to form a modified chitosan with a three-dimensional network structure, while simultaneously introducing quaternary ammonium salt cationic groups. This modified product retains the biocompatibility and degradability of chitosan, forms a three-dimensional network structure with high water absorption capacity, and the introduction of quaternary ammonium salt cationic groups endows the system with strong antibacterial properties.

[0018] Adding the modified chitosan to the seedling substrate can synergistically enhance seedling performance with other components. Firstly, the superabsorbent polymer (SAP) three-dimensional network of the modified chitosan possesses extremely strong water absorption and retention capabilities, storing large amounts of water and releasing it slowly, providing a continuous and stable water supply for seed germination and promoting root development and robust stem growth. Simultaneously, this three-dimensional network can tightly bind with the negatively charged diatomaceous earth and aminated bentonite surfaces through hydrogen bonding, electrostatic adsorption, and ion exchange, forming a stable organic-inorganic composite system. This further optimizes the substrate's moisture retention and aeration properties, providing a loose and suitable physical environment for root development. Its multi-carboxyl structure can synergistically chelate with the active groups in humic acid, stably delivering trace elements such as iron and zinc, promoting root development, increasing the number of white roots, and improving nutrient availability. Quaternary ammonium cations are adsorbed onto the negatively charged clay mineral surface through electrostatic interactions, enhancing the substrate's antibacterial buffering capacity, effectively inhibiting pathogenic microorganisms, and reducing seed rot and disease occurrence. Modified chitosan, as the core function, effectively integrates various components to create a germination microenvironment with synergistic optimization of moisture, nutrients, air permeability and antibacterial properties. This promotes uniform seedling emergence, neat growth and strong root system, thereby significantly improving the seedling rate and seedling uniformity, and overcoming the defects of existing seedling substrates such as unstable quality and poor seedling growth effect. Detailed Implementation

[0019] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0020] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0021] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0022] The present invention uses the following raw materials: Diatomaceous earth: purchased from Shandong Zhengxing New Materials Co., Ltd.

[0023] Bentonite: Purchased from Tianmen Hengchang Chemical Co., Ltd.

[0024] The preparation method of aminated bentonite includes the following steps: M1. Pass the bentonite through a 200-mesh sieve, disperse 5 g of the sieved bentonite in 95 mL of deionized water, add acetic acid to adjust the pH to 4, and stir in a 65℃ constant temperature water bath at 300 rpm for 1 h to obtain a bentonite suspension. M2. Add 1g of γ-aminopropyltriethoxysilane to 50 mL of a mixed ethanol-water solution (ethanol to deionized water volume ratio of 3:1) and stir thoroughly to obtain a silane hydrolysate. Heat the bentonite suspension to 80℃ and stir continuously at 300 rpm. Add the silane hydrolysate dropwise to the bentonite suspension. After the addition is complete, let it stand for 8 h. Separate the solid and liquid, wash the solid multiple times, dry it at 60℃ for 12 h, grind it and pass it through a 200-mesh sieve to obtain aminated bentonite. Peat: Peat soil, purchased from Guangzhou Xiwang Agricultural Development Co., Ltd.

[0025] Organic fertilizer: a 1:1 mixture of fermented cow dung and fermented straw.

[0026] The preparation method of fermented cow dung includes the following steps: Raw materials: The mass ratio of fresh cow dung, water and cow dung fermentation agent (purchased from Weifang Ruichen Biotechnology Co., Ltd.) is 500:10:1; Fermentation conditions: composting at 50-70℃ for 3 months; The moisture content of the final fermented cow dung is controlled at 20wt%.

[0027] The method for preparing fermented straw products includes the following steps: Raw materials: The mass ratio of straw, soybean cake, and straw composting agent (purchased from Shandong Yihao Biotechnology Co., Ltd.) is 100:2:0.1, and the moisture content of the materials is 70 wt%; Fermentation conditions: Fermentation at 50-70℃ for 1 month.

[0028] Inorganic fertilizer: a ternary compound fertilizer with a nitrogen, phosphorus and potassium element mass ratio of 15:15:15, purchased from Stanley Agricultural Group Co., Ltd.

[0029] Humic acid: purchased from Jingzhou Yinjie Chemical Co., Ltd.

[0030] Chitosan: Brand name S52720, purchased from Shanghai Yuanye.

[0031] All water used in this invention is deionized water.

[0032] In this invention, "parts" refers to parts by mass.

[0033] Preparation Example 1 A seedling raising substrate, the seedling raising substrate comprising the following components in parts by weight: 30 parts of diatomaceous earth 15 parts of aminated bentonite 10 parts peat 15 parts organic fertilizer 0.5 parts inorganic fertilizer 0.3 parts humic acid 15 parts modified chitosan; in, The modified chitosan is obtained by reacting chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride, followed by copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide.

[0034] The preparation method of the seedling-specific substrate includes the following steps: S1. Using an aqueous acetic acid solution (volume ratio of 1%) as a solvent, 1 part of the chitosan-diethylenetriaminepentaacetic acid coupling compound and 0.1 part of maleic anhydride were mixed and reacted under a nitrogen atmosphere at 100°C for 8 h. After removing the solvent, the intermediate product was obtained. S2. Using water as a solvent, the intermediate product, methacryloyloxyethyltrimethylammonium chloride, and N,N'-methylenebisacrylamide were blended (the mass ratio of the intermediate product, methacryloyloxyethyltrimethylammonium chloride, and N,N'-methylenebisacrylamide was 1:0.3:0.1), and sodium persulfate (1% of the total mass of the reactants) was added as an initiator. The mixture was reacted under a nitrogen atmosphere at 80°C for 10 h. After removing the solvent, modified chitosan was obtained. S3. Mix all components evenly according to the above mass proportions to obtain a seedling substrate.

[0035] Preparation Example 2 A seedling raising substrate, the seedling raising substrate comprising the following components in parts by weight: 20 parts of diatomaceous earth 10 parts of aminated bentonite 8 parts peat 13 parts organic fertilizer 0.4 parts inorganic fertilizer 0.3 parts humic acid 11 parts modified chitosan; in, The modified chitosan is obtained by reacting chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride, followed by copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide.

[0036] The preparation method of the seedling-specific substrate is the same as that in Preparation Example 1.

[0037] Preparation Example 3 A seedling raising substrate, the seedling raising substrate comprising the following components in parts by weight: 40 parts of diatomaceous earth 20 parts of aminated bentonite 15 parts peat 20 parts organic fertilizer 0.8 parts inorganic fertilizer 0.5 parts humic acid 20 parts modified chitosan; in, The modified chitosan is obtained by reacting chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride, followed by copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide.

[0038] The preparation method of the seedling-specific substrate is the same as that in Preparation Example 1.

[0039] Comparative Preparation Example 1 A special substrate for seedling cultivation. The difference between this comparative example and preparation example 1 is that in step S1, the chitosan-diethylenetriaminepentaacetic acid coupling compound is replaced with chitosan by mass, while the other steps and dosages are the same as in preparation example 1.

[0040] Comparative Preparation Example 2 A special substrate for seedling raising. The difference between this comparative example and preparation example 1 is that step S2 is modified as follows: S2. Using water as a solvent, methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide were blended (the mass ratio of methacryloyloxyethyltrimethylammonium chloride to N,N'-methylenebisacrylamide was 0.3:0.1), and sodium persulfate (1% of the total mass of the reactants) was added as an initiator. The mixture was reacted under a nitrogen atmosphere at 80°C for 10 h. After removing the solvent, a polymer was obtained. The polymer was then blended with an intermediate product (the mass ratio of the polymer to the intermediate product was 0.4:1) to obtain modified chitosan. The other steps and dosages are the same as in Preparation Example 1.

[0041] Comparative preparation example 3 A special substrate for seedling raising. The difference between this comparative example and preparation example 1 is that in step S3, the mass of the methacryloyloxyethyltrimethylammonium chloride is replaced with ethyl methacrylate, while the other steps and dosages are the same as in preparation example 1.

[0042] Examples 1-3 A method for cultivating robust rice seedlings by machine transplanting based on a special seedling substrate includes the following steps: L1. Select sun-dried, plump rice seeds, disinfect and soak them for 2 days, then drain and set aside. L2. Add 4 L of seedling-specific substrate to a 9-inch seedling tray, with a bottom soil depth of 2 cm. Sow 100 rice seeds evenly in each 10×10 cm area. Cover the surface of the germinated seeds with seedling-specific substrate by 0.5-0.6 cm, water thoroughly, and raise seedlings using a darkened tray seedling raising method. Control the temperature at 30-32℃ and the humidity at 93%. After 48 hours of seedling emergence, place the seedling trays on the dry soil in the greenhouse and manage the water uniformly. When the seedlings grow to the three-leaf stage, they can be transplanted by machine. in, The seedling-specific substrates used in Examples 1-3 were prepared in Preparation Examples 1-3, respectively.

[0043] Comparative Examples 1-3 The difference between Comparative Examples 1-3 and Example 1 is that the seedling-specific substrate used in Comparative Examples 1-3 was prepared by Comparative Examples 1-3 respectively; the other steps and dosages are the same as in Example 1.

[0044] Test case The performance of Example 1 and Comparative Examples 1-3 was tested.

[0045] Test method: At 20 days old, the seedling survival rate, seedling uniformity, and disease incidence were assessed.

[0046] (1) The seedling survival rate is calculated as follows: ; (2) Seedling uniformity: Refer to “Wang Yaliang, Zhu Defeng, Li Hui, et al. Effects of rice seedling tray raising on seedling growth characteristics and uniformity [J]. Hybrid Rice, 2022, 37(2):118-122.DOI:10.16267 / j.cnki.1005-3956.20210814.291.”.

[0047] Seedling uniformity is measured by seedling height uniformity (U). sg The measurement and calculation method are as follows: ; ; Among them, S sh The standard deviation of seedling height; xi sh This represents the observed seedling height. sh This represents the average height of the seedlings.

[0048] (3) The incidence rate is calculated as follows: .

[0049] (4) Standards for robust seedlings: seedlings 20 days old, with 3.0-4.0 leaves, 17-22 cm tall, thick and flat base (base diameter ≥ 0.25 cm) with elasticity, more than 10 white roots per plant, uniform growth, upright seedlings with green leaves, long leaves and short sheaths, no yellow leaves, no pests or diseases, and firmly coiled root system that does not crumble when lifted. Calculate the robust seedling rate based on the above standards, which is the proportion of seedlings that meet the robust seedling standards to the total number of seedlings.

[0050] The test results are shown in Table 1.

[0051] Table 1 Performance Test Results .

[0052] Test results show that the performance of Example 1 is significantly better than that of Comparative Examples 1-3, indicating that the seedling substrate prepared by the modified chitosan of the present invention can effectively improve the seedling survival rate and seedling uniformity of rice transplanting, reduce the incidence of disease, increase the seedling vigor rate, and the overall seedling effect is better than that of the unmodified control substrate.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for cultivating robust rice seedlings by machine transplanting based on a special seedling substrate, characterized in that, Includes the following steps: L1. Take rice seeds, sun-dry them, disinfect them, soak them in water, and then set them aside for later use. L2. Add the special seedling substrate to the seedling tray as the bottom soil, sow rice seeds in the seedling tray, cover with the special seedling substrate, water, and raise seedlings using the dark chamber stacked tray seedling raising method; after emergence, place the seedling tray on the dry soil of the greenhouse, use uniform water management, and when the seedlings grow to three leaves and one heart, they can be transplanted by machine. The seedling-specific substrate includes modified chitosan; The modified chitosan is obtained by reacting chitosan-diethylenetriaminepentaacetic acid coupling compound with maleic anhydride, followed by copolymerization with methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide. The seedling-specific substrate comprises the following components in parts by weight: 20-40 parts diatomaceous earth 10-20 parts of aminated bentonite 5-20 parts peat 5-20 parts organic fertilizer Inorganic fertilizer 0.1-1 part 0.1-0.5 parts humic acid 10-20 parts of modified chitosan; The preparation method of the seedling-specific substrate includes the following steps: S1. Chitosan-diethylenetriaminepentaacetic acid coupling compound and maleic anhydride are mixed and reacted under an inert atmosphere and heated to obtain an intermediate product. S2. The intermediate product, methacryloyloxyethyltrimethylammonium chloride and N,N'-methylenebisacrylamide are blended together, an initiator is added, and the mixture is heated under an inert atmosphere to obtain modified chitosan. S3. Mix all components thoroughly to obtain a seedling substrate; In step S1, the mass ratio of the chitosan-diethylenetriaminepentaacetic acid coupling compound to maleic anhydride is 1:(0.1-0.5); In step S2, the mass ratio of the intermediate product, methacryloyloxyethyltrimethylammonium chloride, and N,N'-methylenebisacrylamide is 1:(0.1-0.9):(0.1-0.5).

2. The method for cultivating robust rice seedlings by machine transplanting based on a special substrate for seedling raising, as described in claim 1, is characterized in that... The organic fertilizer is selected from one or more of livestock and poultry manure and agricultural waste fermentation products.

3. The method for cultivating robust rice seedlings by machine transplanting based on a special substrate for seedling raising, as described in claim 1, is characterized in that... The inorganic fertilizer is selected from one or more of nitrogen fertilizer, phosphorus fertilizer, and potassium fertilizer, or a compound fertilizer containing two or more of nitrogen, phosphorus, and potassium elements.

4. The method for cultivating robust rice seedlings by machine transplanting based on a special seedling substrate according to claim 1, characterized in that, In step S1, the temperature of the heating reaction is 90-110℃.

5. The method for cultivating robust rice seedlings by machine transplanting based on a special substrate for seedling raising, as described in claim 1, is characterized in that... In step S2, the temperature of the heating reaction is 60-80℃.