Water-retaining agent suitable for open-air pepper planting, preparation method and application thereof

Abstract

The application discloses a water-retaining agent suitable for open-air pepper planting and a preparation method and application thereof. The water-retaining agent comprises the following components in parts by weight: 5-12 parts of lignin sulfonate sodium grafted N-vinyl pyrrolidone copolymer, 3-5 parts of 3-indole acetamide, 2-4 parts of a crosslinking agent, 2-3 parts of modified carboxymethyl chitosan, and 2-3 parts of diatomite. The water-retaining agent provided by the application realizes controllable water release, promotes pepper growth, and improves soil structure through the synergistic effect of the lignin sulfonate sodium grafted N-vinyl pyrrolidone copolymer, the 3-indole acetamide, the cassava starch-sodium palmitate compound crosslinking agent, the modified carboxymethyl chitosan, and the diatomite, and meets the core requirements of open-air pepper planting.

Description

Technical Field

[0001] This invention relates to the field of chili pepper cultivation and water-retaining agent technology, specifically to a water-retaining agent suitable for open-field chili pepper cultivation, its preparation method, and its application. Background Technology

[0002] Chili peppers are my country's largest vegetable crop, serving as a vital economic link between growers and consumers due to their rich nutritional content and outstanding economic value, occupying a key position in the agricultural industrial structure. Chili pepper cultivation is widespread and large-scale in my country, forming an important part of the agricultural economy in many regions. However, in open-field chili pepper cultivation, some production areas face inherent soil constraints. Many areas suffer from nutrient-poor soil and poor water retention, resulting in relatively low soil productivity and directly limiting chili pepper yield. Under open-field cultivation, chili pepper growth relies entirely on natural rainfall and the soil's own water retention capacity. These soil deficiencies are further amplified during the dry season, inhibiting chili pepper growth and becoming the primary bottleneck restricting the improvement of quality and efficiency in the chili pepper industry.

[0003] With the continuous growth in market demand for chili peppers and the improvement of economic benefits in chili pepper cultivation, continuous cropping has become increasingly common in chili pepper growing areas across the country. This continuous cropping obstacle has become a significant factor exacerbating the industry's development difficulties. Even under conventional cultivation and management conditions, planting chili peppers on the same plot for multiple consecutive seasons can lead to weakened plant growth, increased frequency of pests and diseases, significantly reduced yields, and a decline in flavor and quality. More seriously, some growers, in pursuit of short-term high yields, have developed an unreasonable planting habit of "heavy use of chemical fertilizers and light use of organic fertilizers." This, coupled with the long-term continuous cropping model, further deteriorates the already poor soil quality, destroys soil aggregate structure, and further reduces water and fertilizer retention capacity. This vicious cycle not only directly leads to a double decline in chili pepper yield and fertilizer utilization, but also seriously affects the unique flavor and quality of chili peppers, hindering the healthy and sustainable development of my country's chili pepper industry and urgently requiring targeted technical solutions.

[0004] Water-retaining agents, as highly efficient chemical water-retaining materials, offer a new direction for solving the water management problems in open-field chili pepper cultivation due to their ability to rapidly absorb hundreds or even thousands of times their own weight in deionized water. In open-field planting scenarios, water-retaining agents can absorb and store large amounts of rainfall during the rainy season and slowly release water during the dry season, effectively maintaining stable soil moisture. Moreover, more than 85% of the absorbed water can be directly absorbed and utilized by plant roots, playing a clear role in promoting chili pepper growth. Currently, the mainstream commercial water-retaining agents in my country mainly include polyacrylic acid superabsorbent resin (PAA) and starch-acrylonitrile graft copolymers, but these products have significant limitations when applied to open-field chili pepper cultivation: on the one hand, the production cost is relatively high, which is not well matched with the economic benefits of chili pepper cultivation; on the other hand, their salt tolerance is poor, making it difficult to adapt to the special soil environment of some production areas, resulting in limited water retention effects and hindering large-scale promotion. Therefore, developing a cost-effective water-retaining agent that is adapted to the soil characteristics and growth needs of open-field chili pepper cultivation has become the key to breaking through the current bottlenecks in the industry's development. Summary of the Invention

[0005] The main objective of this invention is to propose a water-retaining agent suitable for open-field chili pepper cultivation, its preparation method, and its application, aiming to provide a water-retaining agent with good water retention properties that can improve the yield of open-field chili pepper cultivation.

[0006] To achieve the above objectives, this invention proposes a water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0007] 5-12 parts of sodium lignosulfonate grafted N-vinylpyrrolidone copolymer, 3-5 parts of 3-indoleacetamide, 2-4 parts of crosslinking agent, 2-3 parts of modified carboxymethyl chitosan, and 2-3 parts of diatomaceous earth.

[0008] Preferably, the crosslinking agent is a complex of cassava starch and sodium palmitate, wherein the mass ratio of cassava starch to sodium palmitate is 1:(0.5~0.8).

[0009] Preferably, the method for preparing the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0010] Sodium lignosulfonate was mixed with deionized water and stirred. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere. An initiator was added, the mixture was heated, and the reaction was carried out. Acetone or ethanol was added to precipitate the mixture. The mixture was then filtered and dried under vacuum to obtain a lignosulfonate-grafted N-vinylpyrrolidone copolymer.

[0011] Preferably, the initiator is selected from either ammonium persulfate or potassium persulfate;

[0012] The temperature is raised to 60-80°C, and the reaction time is 2-6 hours.

[0013] The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone to initiator is 1:(1~5):(0.01~0.05).

[0014] Preferably, the preparation method of the modified carboxymethyl chitosan includes the following steps:

[0015] S1. Mix imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide and react for 4.5-5.5 h. Add sodium hydroxide 0.8-1.2 h before the end of the reaction. After the reaction is complete, filter and take the filtrate to obtain intermediate product 1.

[0016] S2. Mix itaconic acid and p-toluenesulfonic acid, stir, add intermediate product 1 dropwise, react to obtain intermediate product 2;

[0017] S3. Mix carboxymethyl chitosan and propylene glycol, adjust the pH to 8.5-9, add intermediate product 2 and ammonium persulfate, react, and dry to obtain modified carboxymethyl chitosan.

[0018] Preferably, in step S1, the reaction temperature is 60~70°C;

[0019] The molar ratio of imidacloprid, glycidyl phenyl ether, tetrabutylammonium bromide and sodium hydroxide is 1:(1~1.5):(0.07~0.09):(0.4~0.6).

[0020] Preferably, in step S2, the reaction temperature is 55~65℃ and the reaction time is 4~6h;

[0021] The dripping rate is 0.6~1.0 ml / min;

[0022] The molar ratio of itaconic acid, p-toluenesulfonic acid and intermediate 1 is 1:(0.08~0.12):(1.1~1.3).

[0023] Preferably, in step S3, the reaction temperature is 75~85℃ and the reaction time is 6~8h;

[0024] The mass ratio of carboxymethyl chitosan, propylene glycol, intermediate product 2, and ammonium persulfate is 1:(4~6):(0.8~1.0):(0.06~0.08).

[0025] This invention also proposes a method for preparing a water-retaining agent suitable for open-field chili pepper cultivation as described above, comprising the following steps:

[0026] S10. Sodium lignosulfonate grafted N-vinylpyrrolidone copolymer is mixed with deionized water to prepare an emulsion. Modified carboxymethyl chitosan and diatomaceous earth are added in proportion, stirred, and the pH is adjusted to neutral to obtain a mixture.

[0027] S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 50~70℃ for 0.8~1.2h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0028] This invention also proposes the application of the water-retaining agent, as described above, suitable for open-field chili cultivation, in chili transplantation. The specific application includes the following steps:

[0029] S30. Use farm tools to harrow the land, and during the harrowing process, cover the organic fertilizer and the water-retaining agent with soil. The mass ratio of the water-retaining agent to the organic fertilizer is 1:(50~100), and the covering thickness is 3~5cm. Make the land into ridges with a ridge width of 20~35cm and a spacing of 15~20cm between adjacent ridges. Then dig planting holes on the ridges with a spacing of 20~30cm between the planting holes, and set them aside for use.

[0030] S40. Transplant healthy chili seedlings into planting holes. After the initial flowering stage of the chili peppers, apply high-potassium and high-nitrogen fertilizer. At the same time, combine the insect-repellent activity of modified carboxymethyl chitosan in the water-retaining agent with conventional pesticides for integrated pest management.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) The water-retaining agent provided by this invention achieves the functions of slow and controllable water release, promoting pepper growth, and improving soil structure through the synergistic effect of sodium lignosulfonate grafted with N-vinylpyrrolidone copolymer, 3-indoleacetamide, cassava starch-sodium palmitate complex crosslinking agent, modified carboxymethyl chitosan, and diatomaceous earth, which meets the core needs of open-field pepper planting. This invention constructs a three-dimensional water-retaining network through graft copolymer and crosslinking agent to achieve efficient adsorption and storage of rainwater and irrigation water; modified carboxymethyl chitosan optimizes the stability of the network structure, and at the same time, it works synergistically with diatomaceous earth to improve the soil aggregate structure, thereby enhancing the water-retaining agent's resistance to erosion and degradation in open-field fluctuating environments; 3-indoleacetamide is anchored in the network through hydrogen bonding and slowly released, promoting pepper root development and enhancing the root system's absorption and utilization efficiency of stored water.

[0033] (2) The method for preparing modified carboxymethyl chitosan provided by the present invention firstly involves the ring-opening reaction between the amino group of imidacloprid and the epoxy group of glycidyl phenyl ether to generate a hydroxyl-containing ether derivative, namely intermediate product 1. The introduction of the imidacloprid group enables the final product to have insecticidal activity, thereby increasing the yield of chili peppers and reducing the cost and pollution of pesticides applied alone. The hydroxyl group of intermediate product 1 undergoes an esterification reaction with the carboxyl group of itaconic acid under the action of p-toluenesulfonic acid to obtain intermediate product 2, introducing an unsaturated double bond. Finally, the double bond of intermediate product 2 undergoes graft polymerization with the hydroxyl group on the carboxymethyl chitosan molecular chain, and the final product has both hydrophobic segments (ethyl, phenyl) and hydrophilic groups (carboxyl, amino), which can form a stable interpenetrating network with other components of the water-retaining agent, and at the same time adsorb 3-indoleacetamide through hydrogen bonding.

[0034] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. 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.

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0037] Example 1

[0038] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0039] The mixture consists of 8 parts sodium lignosulfonate grafted N-vinylpyrrolidone copolymer, 4 parts 3-indoleacetamide, 3 parts crosslinking agent, 2.5 parts modified carboxymethyl chitosan, and 2.5 parts diatomaceous earth.

[0040] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0041] S10. A 18% emulsion was prepared by mixing sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer with deionized water. Modified carboxymethyl chitosan and diatomaceous earth were added in proportion, stirred evenly, and the pH was adjusted to neutral to obtain a mixture.

[0042] S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 60°C for 1.0 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0043] The crosslinking agent is a complex of cassava starch and sodium palmitate, with a mass ratio of 1:0.6.

[0044] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0045] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:12 and stirred to dissolve. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere, followed by the initiator ammonium persulfate. The mixture was heated to 70°C and reacted for 4 hours. After the reaction was completed, ethanol was added to precipitate the product. The mixture was then filtered and dried under vacuum to obtain a lignosulfonate-grafted N-vinylpyrrolidone copolymer. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone, and initiator was 1:3:0.03.

[0046] The preparation method of the modified carboxymethyl chitosan includes the following steps:

[0047] S1. Mix imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.3:0.08 and react at 65℃ for 5.0 h. Add sodium hydroxide (molar ratio of imidacloprid to sodium hydroxide is 1:0.5) 1.0 h before the end of the reaction. After the reaction is complete, filter and take the filtrate to obtain intermediate product 1.

[0048] S2. Mix itaconic acid and p-toluenesulfonic acid in a molar ratio of 1:0.1, stir well, add intermediate product 1 dropwise (the molar ratio of itaconic acid to intermediate product 2 is 1:1.2), and react at 60℃ for 5 hours to obtain intermediate product 2.

[0049] S3. Mix carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate in a mass ratio of 1:5:0.9:0.07, adjust the pH to 8.7, react at 80℃ for 7 h, cool to room temperature after the reaction is completed, dialyze, and freeze dry to obtain modified carboxymethyl chitosan.

[0050] Example 2

[0051] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0052] Five parts of sodium lignosulfonate grafted N-vinylpyrrolidone copolymer, three parts of 3-indoleacetamide, two parts of crosslinking agent, two parts of modified carboxymethyl chitosan, and two parts of diatomaceous earth.

[0053] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0054] S10. A 15% emulsion was prepared by mixing sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer with deionized water. Modified carboxymethyl chitosan and diatomaceous earth were added according to the above weight ratio. The mixture was stirred at 300 r / min for 30 min and the pH was adjusted to neutral to obtain a mixture.

[0055] S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 50°C for 1.0 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0056] The crosslinking agent is a complex of cassava starch and sodium palmitate, with a mass ratio of 1:0.5.

[0057] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0058] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:10 and stirred to dissolve. Nitrogen gas was introduced to replace the air in the reaction system. Then, N-vinylpyrrolidone was added dropwise, followed by the initiator ammonium persulfate. The temperature was raised to 60°C and the reaction was kept constant for 2 hours. After the reaction was completed, the reaction solution was slowly added to 3 times the volume of acetone to precipitate the product. After standing for 2 hours, the product was filtered. The filter cake was washed 3 times with acetone and dried under vacuum at 50°C to constant weight to obtain the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer.

[0059] The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone, and initiator is 1:1:0.01.

[0060] The preparation method of the modified carboxymethyl chitosan includes the following steps:

[0061] S1. Imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide are mixed in a mass ratio of 1:1:0.07, heated to 60℃, and stirred at 250 r / min for 4.5 h. Sodium hydroxide (the mass ratio of imidacloprid to sodium hydroxide is 1:0.4) is added 0.8 h before the end of the reaction. The reaction is continued until the endpoint. After cooling to room temperature, the mixture is filtered and the filtrate is used to obtain intermediate product 1.

[0062] S2. Mix itaconic acid and p-toluenesulfonic acid in a molar ratio of 1:0.08, stir well, add intermediate product 1 dropwise (the molar ratio of itaconic acid to intermediate product 2 is 1:1.1), and react at 55℃ for 4 hours to obtain intermediate product 2.

[0063] S3. Mix carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate in a mass ratio of 1:5:0.8:0.06, adjust the pH to 8.5, react at 75°C for 6 hours, cool to room temperature after the reaction is completed, dialyze, and freeze dry to obtain modified carboxymethyl chitosan.

[0064] Example 3

[0065] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0066] Sodium lignosulfonate grafted N-vinylpyrrolidone copolymer 12 parts, 3-indoleacetamide 5 parts, crosslinking agent 4 parts, modified carboxymethyl chitosan 3 parts, diatomaceous earth 3 parts.

[0067] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0068] S10. A 20% emulsion was prepared by mixing sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer with deionized water. Modified carboxymethyl chitosan and diatomaceous earth were added according to the above weight ratio. The mixture was stirred at 400 r / min for 40 min and the pH was adjusted to neutral to obtain a mixture.

[0069] S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 70°C for 1.2 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation;

[0070] The crosslinking agent is a complex of cassava starch and sodium palmitate, with a mass ratio of 1:0.8.

[0071] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0072] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:15, stirred and dissolved, and nitrogen gas was introduced to replace the air in the reaction system. Then, N-vinylpyrrolidone was added dropwise, followed by potassium persulfate as an initiator. The temperature was raised to 80°C and the reaction was maintained at a constant temperature for 6 hours. After the reaction was completed, the reaction solution was slowly added to 4 times its volume of ethanol to precipitate the product. After standing for 3 hours, the product was filtered, and the filter cake was washed 4 times with ethanol and dried under vacuum at 60°C to constant weight to obtain the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone and initiator was 1:5:0.05.

[0073] The preparation method of the modified carboxymethyl chitosan includes the following steps:

[0074] S1. Imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide are mixed in a mass ratio of 1:1.5:0.09, heated to 70℃, and stirred at 300 r / min for 5.5 h. Sodium hydroxide (the mass ratio of imidacloprid to sodium hydroxide is 1:0.6) is added 1.2 h before the end of the reaction. The reaction is continued until the endpoint. After cooling to room temperature, the mixture is filtered and the filtrate is used to obtain intermediate product 1.

[0075] S2. Mix itaconic acid and p-toluenesulfonic acid in a molar ratio of 1:0.12, stir well, add intermediate product 1 dropwise (the molar ratio of itaconic acid to intermediate product 2 is 1:1.3), and react at 65℃ for 6 hours to obtain intermediate product 2.

[0076] S3. Mix carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate in a mass ratio of 1:6:1.0:0.08, adjust the pH to 9, react at 85°C for 8 hours, cool to room temperature after the reaction is completed, dialyze, and freeze dry to obtain modified carboxymethyl chitosan.

[0077] Comparative Example 1

[0078] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0079] Sodium lignosulfonate 4 parts, N-vinylpyrrolidone 4 parts, 3-indoleacetamide 4 parts, crosslinking agent 3 parts, modified carboxymethyl chitosan 2.5 parts, diatomaceous earth 2.5 parts;

[0080] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0081] S10. Mix 4 parts sodium lignosulfonate, 4 parts N-vinylpyrrolidone and deionized water to prepare a mixed emulsion. Add modified carboxymethyl chitosan and diatomaceous earth in proportion, stir evenly, adjust pH to neutral, and obtain a mixture.

[0082] S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 60°C for 1.0 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0083] The crosslinking agent is a complex of cassava starch and sodium palmitate, with a mass ratio of 1:0.6.

[0084] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0085] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:12 and stirred to dissolve. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere, followed by the initiator ammonium persulfate. The mixture was heated to 70°C and reacted for 4 hours. After the reaction was completed, ethanol was added to precipitate the product. The mixture was then filtered and dried under vacuum to obtain a lignosulfonate-grafted N-vinylpyrrolidone copolymer. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone, and initiator was 1:3:0.03.

[0086] The preparation method of the modified carboxymethyl chitosan includes the following steps:

[0087] S1. Mix imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.3:0.08 and react at 65℃ for 5.0 h. Add sodium hydroxide (molar ratio of imidacloprid to sodium hydroxide is 1:0.5) 1.0 h before the end of the reaction. After the reaction is complete, filter and take the filtrate to obtain intermediate product 1.

[0088] S2. Mix itaconic acid and p-toluenesulfonic acid in a molar ratio of 1:0.1, stir well, add intermediate product 1 dropwise (the molar ratio of itaconic acid to intermediate product 2 is 1:1.2), and react at 60℃ for 5 hours to obtain intermediate product 2.

[0089] S3. Mix carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate in a mass ratio of 1:5:0.9:0.07, adjust the pH to 8.7, react at 80℃ for 7 h, cool to room temperature after the reaction is completed, dialyze, and freeze dry to obtain modified carboxymethyl chitosan.

[0090] Compared with Example 1, in Comparative Example 1, 8 parts of sodium lignosulfonate grafted N-vinylpyrrolidone copolymer were replaced with 4 parts of sodium lignosulfonate and 4 parts of N-vinylpyrrolidone in the water-retaining agent.

[0091] Comparative Example 2

[0092] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0093] 8 parts sodium lignosulfonate grafted N-vinylpyrrolidone copolymer, 3 parts crosslinking agent, 2.5 parts modified carboxymethyl chitosan, and 2.5 parts diatomaceous earth;

[0094] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0095] S10. A 18% emulsion was prepared by mixing sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer with deionized water. Modified carboxymethyl chitosan and diatomaceous earth were added in proportion, stirred evenly, and the pH was adjusted to neutral to obtain a mixture.

[0096] S20. Add a crosslinking agent to the mixture, stir at 60°C for 1.0 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0097] The crosslinking agent is a complex of cassava starch and sodium palmitate, with a mass ratio of 1:0.6.

[0098] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0099] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:12 and stirred to dissolve. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere, followed by the initiator ammonium persulfate. The mixture was heated to 70°C and reacted for 4 hours. After the reaction was completed, ethanol was added to precipitate the product. The mixture was then filtered and dried under vacuum to obtain a lignosulfonate-grafted N-vinylpyrrolidone copolymer. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone, and initiator was 1:3:0.03.

[0100] The preparation method of the modified carboxymethyl chitosan includes the following steps:

[0101] S1. Mix imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.3:0.08 and react at 65℃ for 5.0 h. Add sodium hydroxide (molar ratio of imidacloprid to sodium hydroxide is 1:0.5) 1.0 h before the end of the reaction. After the reaction is complete, filter and take the filtrate to obtain intermediate product 1.

[0102] S2. Mix itaconic acid and p-toluenesulfonic acid in a molar ratio of 1:0.1, stir well, add intermediate product 1 dropwise (the molar ratio of itaconic acid to intermediate product 2 is 1:1.2), and react at 60℃ for 5 hours to obtain intermediate product 2.

[0103] S3. Mix carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate in a mass ratio of 1:5:0.9:0.07, adjust the pH to 8.7, react at 80℃ for 7 h, cool to room temperature after the reaction is completed, dialyze, and freeze dry to obtain modified carboxymethyl chitosan.

[0104] Compared with Example 1, Comparative Example 2 lacks 3-indoleacetamide in its water-retaining agent components.

[0105] Comparative Example 3

[0106] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0107] The mixture consists of 8 parts sodium lignosulfonate grafted N-vinylpyrrolidone copolymer, 4 parts 3-indoleacetamide, 2.5 parts modified carboxymethyl chitosan, and 2.5 parts diatomaceous earth.

[0108] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0109] S10. A 18% emulsion was prepared by mixing sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer with deionized water. Modified carboxymethyl chitosan and diatomaceous earth were added in proportion, stirred evenly, and the pH was adjusted to neutral to obtain a mixture.

[0110] S20. Add 3-indoleacetamide to the mixture, stir at 60°C for 1.0 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0111] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0112] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:12 and stirred to dissolve. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere, followed by the initiator ammonium persulfate. The mixture was heated to 70°C and reacted for 4 hours. After the reaction was completed, ethanol was added to precipitate the product. The mixture was then filtered and dried under vacuum to obtain a lignosulfonate-grafted N-vinylpyrrolidone copolymer. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone, and initiator was 1:3:0.03.

[0113] The preparation method of the modified carboxymethyl chitosan includes the following steps:

[0114] S1. Mix imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide in a molar ratio of 1:1.3:0.08 and react at 65℃ for 5.0 h. Add sodium hydroxide (molar ratio of imidacloprid to sodium hydroxide is 1:0.5) 1.0 h before the end of the reaction. After the reaction is complete, filter and take the filtrate to obtain intermediate product 1.

[0115] S2. Mix itaconic acid and p-toluenesulfonic acid in a molar ratio of 1:0.1, stir well, add intermediate product 1 dropwise (the molar ratio of itaconic acid to intermediate product 2 is 1:1.2), and react at 60℃ for 5 hours to obtain intermediate product 2.

[0116] S3. Mix carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate in a mass ratio of 1:5:0.9:0.07, adjust the pH to 8.7, react at 80℃ for 7 h, cool to room temperature after the reaction is completed, dialyze, and freeze dry to obtain modified carboxymethyl chitosan.

[0117] Compared with Example 1, Comparative Example 3 lacks a crosslinking agent in its water-retaining agent components.

[0118] Comparative Example 4

[0119] A water-retaining agent suitable for open-field chili pepper cultivation, comprising the following components by weight:

[0120] The mixture consists of 8 parts sodium lignosulfonate grafted N-vinylpyrrolidone copolymer, 4 parts 3-indoleacetamide, 3 parts crosslinking agent, 2.5 parts carboxymethyl chitosan, and 2.5 parts diatomaceous earth.

[0121] The method for preparing the water-retaining agent suitable for open-field chili pepper cultivation includes the following steps:

[0122] S10. A 18% emulsion was prepared by mixing sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer with deionized water. Carboxymethyl chitosan and diatomaceous earth were added in proportion, stirred evenly, and the pH was adjusted to neutral to obtain a mixture.

[0123] S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 60°C for 1.0 h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

[0124] The crosslinking agent is a complex of cassava starch and sodium palmitate, with a mass ratio of 1:0.6.

[0125] The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps:

[0126] Sodium lignosulfonate and deionized water were mixed at a mass ratio of 1:12 and stirred to dissolve. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere, followed by the initiator ammonium persulfate. The mixture was heated to 70°C and reacted for 4 hours. After the reaction was completed, ethanol was added to precipitate the product. The mixture was then filtered and dried under vacuum to obtain a lignosulfonate-grafted N-vinylpyrrolidone copolymer. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone and the initiator was 1:3:0.03.

[0127] Compared with Example 1, in Comparative Example 4, the water-retaining agent component modified carboxymethyl chitosan was replaced with carboxymethyl chitosan.

[0128] Test methods and results

[0129] 1. Test the water retention performance of the water-retaining agents in Examples 1-3 and Comparative Examples 1-4, including water absorption ratio and soil water holding capacity.

[0130] The water absorption ratio test method is as follows: using the tea bag method, 3g of water-retaining agent is placed in a tea bag and soaked in deionized water and salt solution, and the water absorption ratio of the water-retaining agent (the weight of water that a unit mass of water-retaining agent can absorb) is measured. The results are shown in Table 1. Each treatment has 3 replicates, and the average value is given.

[0131] Table 1. Water absorption ratio (g / g) of each group of water-retaining agents

[0132]

[0133] Maximum soil water holding capacity: Weigh 100g of air-dried soil that has passed through a 2mm sieve, mix it evenly with 4g of water-retaining agent, fill a 100 cubic millimeter soil ring, weigh it and record the weight as M1, then soak it in distilled water for 12 hours, weigh it again and record the weight as M2. The maximum water holding capacity is M2-M1. The results are shown in Table 2. The control group contained only 100g of soil and no water-retaining agent was added.

[0134]

[0135] 2. The effects of the water-retaining agents in Examples 1-3 and Comparative Examples 1-4 on the yield of open-field chili peppers were tested.

[0136] Experimental Site: The experiment was conducted in a vegetable planting demonstration garden. The land was leveled using farm tools. During leveling, organic fertilizer and the aforementioned water-retaining agent were covered with soil at a mass ratio of 1:80, with a covering thickness of 4 cm. The land was then divided into ridges, 30 cm wide, with a spacing of 18 cm between adjacent ridges. Planting holes were then dug on the ridges, with a spacing of 25 cm between planting holes. Healthy pepper seedlings were transplanted into the planting holes. Simultaneously, combined with the insecticidal activity of modified carboxymethyl chitosan in the water-retaining agent, conventional pesticides were used for integrated pest management. The organic fertilizer contained 3.4% nitrogen, 2.71% phosphorus, and 2.15% potassium.

[0137] Experimental Design: The experiment consisted of 8 blocks, each spaced 50 cm apart, with 3 replicates per treatment, randomly distributed. One block served as a control group, applying only organic fertilizer and no water-retaining agent. The other blocks applied water-retaining agents and organic fertilizers as described in Examples 1-3 and Comparative Examples 1-4, respectively. Water management and pest and disease control were identical across all blocks, following local chili pepper cultivation practices. After harvest, the yield per chili pepper plant, the number of peppers per plant, and the yield per acre were measured for each of the 8 blocks. The results are shown in Table 3.

[0138] Table 3. Statistical results of single chili pepper plant yield, number of peppers per plant, and yield per mu for each group.

[0139]

[0140] As can be seen from the data in Tables 1-3 above, compared with Comparative Examples 1-4, the components of the water-retaining agent prepared by this invention have a synergistic effect, which improves the water-retaining performance of the water-retaining agent and achieves the effect of increasing the yield of chili peppers.

[0141] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A water-retaining agent suitable for open-field chili pepper cultivation, characterized in that, By weight, it includes the following components: Sodium lignosulfonate grafted N-vinylpyrrolidone copolymer 5-12 parts, 3-indoleacetamide 3-5 parts, crosslinking agent 2-4 parts, modified carboxymethyl chitosan 2-3 parts, diatomaceous earth 2-3 parts; The crosslinking agent is a complex of cassava starch and sodium palmitate, wherein the mass ratio of cassava starch to sodium palmitate is 1:(0.5~0.8). The preparation method of the sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer includes the following steps: Sodium lignosulfonate was mixed with deionized water and stirred. N-vinylpyrrolidone was added dropwise under a nitrogen atmosphere, followed by the addition of an initiator. The mixture was heated and reacted. Acetone or ethanol was added to precipitate the mixture. The mixture was then filtered and dried under vacuum to obtain a sodium lignosulfonate-grafted N-vinylpyrrolidone copolymer. The initiator was selected from either ammonium persulfate or potassium persulfate. The mass ratio of sodium lignosulfonate, N-vinylpyrrolidone, and initiator was 1:(1~5):(0.01~0.05). The preparation method of the modified carboxymethyl chitosan includes the following steps: S1. Mix imidacloprid, glycidyl phenyl ether and tetrabutylammonium bromide and react for 4.5-5.5 h. Add sodium hydroxide 0.8-1.2 h before the end of the reaction. After the reaction is complete, filter and take the filtrate to obtain intermediate product 1. S2. Mix itaconic acid and p-toluenesulfonic acid, stir, add intermediate product 1 dropwise, react to obtain intermediate product 2; S3. Mix carboxymethyl chitosan and propylene glycol, adjust the pH to 8.5-9, add intermediate product 2 and ammonium persulfate, react, and dry to obtain modified carboxymethyl chitosan; the molar ratio of imidacloprid, glycidyl phenyl ether, tetrabutylammonium bromide and sodium hydroxide is 1:(1-1.5):(0.07-0.09):(0.4-0.6); the molar ratio of itaconic acid, p-toluenesulfonic acid and intermediate product 1 is 1:(0.08-0.12):(1.1-1.3); the mass ratio of carboxymethyl chitosan, propylene glycol, intermediate product 2 and ammonium persulfate is 1:(4-6):(0.8-1.0):(0.06-0.08).

2. The water-retaining agent suitable for open-field chili pepper cultivation according to claim 1, characterized in that, The temperature is raised to 60-80°C, and the reaction time is 2-6 hours.

3. The water-retaining agent suitable for open-field chili pepper cultivation according to claim 1, characterized in that, In step S1, the reaction temperature is 60~70℃.

4. The water-retaining agent suitable for open-field chili pepper cultivation according to claim 1, characterized in that, In step S2, the reaction temperature is 55~65℃ and the reaction time is 4~6h; The dripping rate is 0.6~1.0 ml / min.

5. The water-retaining agent suitable for open-field chili pepper cultivation according to claim 1, characterized in that, In step S3, the reaction temperature is 75~85℃ and the reaction time is 6~8h.

6. A method for preparing a water-retaining agent suitable for open-field chili pepper cultivation as described in claim 1, characterized in that, Includes the following steps: S10. Sodium lignosulfonate grafted N-vinylpyrrolidone copolymer is mixed with deionized water to prepare an emulsion. Modified carboxymethyl chitosan and diatomaceous earth are added in proportion, stirred, and the pH is adjusted to neutral to obtain a mixture. S20. Add cross-linking agent and 3-indoleacetamide to the mixture, stir at 50~70℃ for 0.8~1.2h, dry, and pulverize to obtain a water-retaining agent suitable for open-field chili pepper cultivation.

7. The application of a water-retaining agent suitable for open-field chili cultivation as described in any one of claims 1 to 5 in chili transplantation, characterized in that, The specific application includes the following steps: S30. Use farm tools to harrow the land, and during the harrowing process, cover the organic fertilizer and the water-retaining agent with soil. The mass ratio of the water-retaining agent to the organic fertilizer is 1:(50~100), and the covering thickness is 3~5cm. Make the land into ridges with a ridge width of 20~35cm and a spacing of 15~20cm between adjacent ridges. Then dig planting holes on the ridges with a spacing of 20~30cm between the planting holes, and set them aside for use. S40. Transplant healthy chili seedlings into planting holes. After the initial flowering stage of the chili peppers, apply high-potassium and high-nitrogen fertilizer. At the same time, combine the insect-repellent activity of modified carboxymethyl chitosan in the water-retaining agent with conventional pesticides for integrated pest management.

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