Slow-release fertilizer for saline-alkali soil and preparation method of slow-release fertilizer

Abstract

The invention provides a slow-release fertilizer for saline-alkali soil and a preparation method thereof, and the slow-release fertilizer comprises a granular core which is formed by co-granulation of a basic fertilizer composition and charcoal powder; the first coating layer is formed on the surface of the granular core by a mixture consisting of gamma-polyglutamic acid or a derivative thereof and sodium alginate; the second coating layer is formed on the surface of the first coating layer by sulfur; and the third coating layer is formed on the surface of the second coating layer by an anti-blocking agent. The slow-release fertilizer for the saline-alkali soil is strong in functionality and good in slow-release effect, improves the granular structure of soil, improves the utilization rate of water and fertilizer, synergistically reduces the pH of the saline-alkali soil, increases the content of nutrients and organic matters in the soil, promotes the growth and development of plants, and improves the micro-ecology of the soil.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a slow-release fertilizer for saline-alkali land and a preparation method thereof. Background Art

[0002] Food security is a national priority, and arable land is the root of food security. At present, about 1 billion hectares of land in the world are affected by salinization, accounting for about 7% of the earth's land area. my country is the third largest country in the world in terms of saline-alkali land distribution, and the rational development of saline-alkali land has become an important breakthrough in increasing and improving the area of ​​arable land.

[0003] Saline-alkali land refers to soil with a salt content of more than 0.1%. Generally speaking, when the soil salt content exceeds 0.1%, the growth of ordinary crops begins to be affected; when the soil salt content exceeds 0.3%, the yield of most crops decreases significantly. Domestic and foreign saline-alkali land improvement measures are mainly divided into four categories: engineering measures, agronomic measures, chemical measures and biological measures. For example, deep loosening technology for many years can effectively reduce the pH of soda saline-alkali soil in Songnen Plain and improve soil nutrients; the synergistic effect of preparing modified composite materials using industrial by-products titanium gypsum and biochar as raw materials significantly promotes rice growth and improves soil salinity, and also provides new ideas for the resource utilization of solid waste; some scholars also use tidal flat salt-tolerant plants and salt-tolerant microbial agents as materials, combined with existing salt soil improvement technologies in coastal areas to improve the saline-alkali soil in the Hetao irrigation area of ​​Inner Mongolia, and achieve "salt removal by alkali sedge and soil improvement by sesbania", effectively improving the degree of soil salinization in inland areas. Saline-alkali areas are usually ecologically fragile and sensitive areas, and safety and sustainability are an important prerequisite for the transformation and utilization of saline-alkali land. Therefore, new, green and environmentally friendly improvers / functional fertilizers have become a research hotspot.

[0004] Shi Yang et al. developed a microbial improver for dry land soil in soda saline-alkali land (CN110054531B): 60-80 parts of blocker, 5-6 parts of acidity regulator, 20-30 parts of organic fertilizer, and 0.01-0.03 parts of microbial agent, so as to increase organic nutrients, activate soil vitality, and repair soil ecology, and finally achieve the purpose of accelerating the maturation of the arable layer, inhibiting the recurrence of salinization, and achieving the purpose of curing saline-alkali land. Guo Yongjun et al. developed a fertilizer for improving saline-alkali land, which mainly includes the steps of mixing core chemical fertilizers with trace element fertilizers, fulvic acid, sulfur, superphosphate, microbial strains, and compounding with agricultural wastewater. The reaction raw materials are extensive and the reaction conditions are easy to achieve, but the operation steps are lengthy and cumbersome. Moreover, whether the functional microorganisms survive and play a role is closely related to the actual soil environmental conditions. Studies have pointed out that the main reason for the increase in microbial biomass and diversity after the application of organic fertilizers is the activation of the indigenous microbial community in the soil, and most of the exogenous microorganisms from organic fertilizers cannot survive under soil conditions after a few months. In addition, at present, the fertilizers used to improve saline-alkali land have a high market price and relatively single functions. They cannot improve the soil and promote plant growth at the same time, which brings certain restrictions to the use of fertilizers. Summary of the invention

[0005] In order to solve the problems existing in the background technology, the present invention provides a slow-release fertilizer for saline-alkali land and a preparation method thereof. The slow-release fertilizer has good slow-release effect, can improve soil aggregate structure, improve water and fertilizer utilization rate, synergistically reduce the pH of saline-alkali soil, increase the nutrient and organic matter content in the soil, promote plant growth and development, and improve soil microecology.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] In a first aspect, the present invention provides a slow-release fertilizer for saline-alkali land, comprising:

[0008] a granular core formed by co-granulating a base fertilizer composition with biochar powder;

[0009] A first coating layer, formed on the surface of the granular core, is a mixture of γ-polyglutamic acid or its derivatives and sodium alginate;

[0010] A second envelope layer, formed of sulfur on the surface of the first envelope layer;

[0011] The third coating layer is formed on the surface of the second coating layer by an anti-caking agent.

[0012] According to the above scheme, the added amounts of the biochar, γ-polyglutamic acid or its derivatives, sodium alginate, sulfur and anti-caking agent are 10%-40%, 1‰-10‰, 1‰-10‰, 2%-6% and 5‰-10‰ of the weight of the basic fertilizer composition, respectively.

[0013] According to the above scheme, the particle size of the granular core is 0.2-0.4 cm.

[0014] According to the above scheme, the weight ratio of nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer is 32-45:28-40:15-35.

[0015] According to the above scheme, the nitrogen fertilizer is selected from one or two of urea and ammonium nitrate, the phosphate fertilizer is selected from at least one of superphosphate, diammonium phosphate or monoammonium phosphate, and the potash fertilizer is selected from at least one of potassium sulfate, potassium chloride or potassium dihydrogen phosphate.

[0016] According to the above scheme, the γ-polyglutamic acid or its derivative is one of γ-polyglutamic acid, γ-polyglutamic acid derivative salt, and γ-polyglutamic acid fermentation culture.

[0017] According to the above scheme, the anti-caking agent is at least one of zeolite powder, attapulgite, diatomaceous earth, talc, limestone, and silicon dioxide powder.

[0018] In a second aspect, the present invention provides a method for preparing the above-mentioned slow-release fertilizer for saline-alkali land, comprising the following steps:

[0019] S1. adding the biochar powder to the basic fertilizer composition, stirring evenly, and granulating in a drum granulator to form a granular core;

[0020] S2. After uniformly mixing γ-polyglutamic acid or its derivative with sodium alginate, a powder or solution of a first coating material is obtained, which is preheated to 50-60° C. and sprayed on the surface of the granular core until the surface of the granular core is uniformly coated, dried, and cooled to form a first coating layer on the surface of the granular core;

[0021] S3. spraying sulfur preheated to 60-70°C onto the surface of the first coating layer until the surface of the first coating layer is evenly coated, drying, cooling, and forming a second coating layer on the surface of the first coating layer;

[0022] S4. The anti-caking agent is uniformly coated on the surface of the second coating layer to form a third coating layer.

[0023] The beneficial effects of the present invention are:

[0024] The slow-release fertilizer for saline-alkali land of the present invention has strong functionality and good slow-release effect, improves soil aggregate structure, increases water and fertilizer utilization rate, synergistically reduces saline-alkali soil pH, increases nutrient and organic matter content in the soil, promotes plant growth and development, and improves soil microecology. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with specific embodiments. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] It should be noted that in the description of the embodiments of the present application, the description of the term "some specific embodiments" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0027] In a first aspect, the present invention provides a slow-release fertilizer for saline-alkali land, comprising:

[0028] a granular core formed by co-granulating a base fertilizer composition with biochar powder;

[0029] A first coating layer, formed on the surface of the granular core, is a mixture of γ-polyglutamic acid or its derivatives and sodium alginate;

[0030] A second envelope layer, formed of sulfur on the surface of the first envelope layer;

[0031] The third coating layer is formed on the surface of the second coating layer by an anti-caking agent.

[0032] In some specific embodiments, the added amounts of the biochar powder, γ-polyglutamic acid or its derivatives, sodium alginate, sulfur and anti-caking agent are 10%-40%, 1‰-10‰, 1‰-10‰, 2%-6% and 5‰-10‰ of the weight of the basic fertilizer composition, respectively.

[0033] In some specific embodiments, the particle size of the granular core is controlled to be 0.2-0.4 cm.

[0034] In some specific embodiments, the basic fertilizer composition is a combination of nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer, which can provide nutrients for plant growth.

[0035] In some specific embodiments, the weight ratio of the nitrogen fertilizer, the phosphorus fertilizer and the potassium fertilizer is 32-45:28-40:15-35. The basic fertilizer composition composed of the nitrogen fertilizer, the phosphorus fertilizer and the potassium fertilizer is stirred and mixed evenly by a mixer and then crushed into powder.

[0036] In some specific embodiments, the nitrogen fertilizer is selected from one or two of urea and ammonium nitrate, the phosphate fertilizer is selected from at least one of superphosphate, diammonium phosphate or monoammonium phosphate, and the potassium fertilizer is selected from at least one of potassium sulfate, potassium chloride or potassium dihydrogen phosphate.

[0037] In some specific embodiments, the biochar powder is any one or more of rice straw, vegetable vine straw, wheat straw, and corn straw, which is carbonized at 300-500° C. for 1-3 hours under sealed conditions, and then the carbonized product is crushed after cooling to room temperature. The particle size of the biochar powder is ≤0.5 mm.

[0038] According to the above scheme, the γ-polyglutamic acid or its derivative is one or a combination of γ-polyglutamic acid, γ-polyglutamic acid derivative salts, and γ-polyglutamic acid fermentation culture.

[0039] The amount of γ-polyglutamic acid or its derivatives added is calculated based on the amount of γ-polyglutamic acid contained, and the molecular weight of γ-polyglutamic acid ranges from 10 to 4000 kDa. γ-polyglutamic acid derivative salts include polyglutamic acid salts chelated with one or more elements such as Na, K, Ca, Mg, Mn, and Si.

[0040] The γ-polyglutamic acid fermentation culture comprises a polyglutamic acid production strain and a polyglutamic acid fermentation broth of a fermentation medium, a concentrate or a dried product of the polyglutamic acid fermentation broth. Further, the polyglutamic acid production strain can be the strain in ZL2019104959886.6.

[0041] According to the above scheme, the anti-caking agent is at least one of zeolite powder, attapulgite, diatomaceous earth, talc, limestone, and silicon dioxide powder.

[0042] In a second aspect, the present invention provides a method for preparing the above-mentioned slow-release fertilizer for saline-alkali land, comprising the following steps:

[0043] S1. adding the biochar powder to the basic fertilizer composition, stirring evenly, and granulating in a drum granulator to form a granular core;

[0044] S2. After uniformly mixing γ-polyglutamic acid or its derivative with sodium alginate, a powder or solution of a first coating material is obtained, which is preheated to 50-60° C. and sprayed on the surface of the granular core until the surface of the granular core is uniformly coated, dried, and cooled to form a first coating layer on the surface of the granular core;

[0045] S3. spraying sulfur preheated to 60-70°C onto the surface of the first coating layer until the surface of the first coating layer is evenly coated, drying, cooling, and forming a second coating layer on the surface of the first coating layer;

[0046] S4. The anti-caking agent is uniformly coated on the surface of the second coating layer to form a third coating layer.

[0047] Biochar is a stable carbon-rich material with high surface area, porous structure, high CEC, oxygen-containing functional groups and high nutrient content produced by pyrolysis of biomass under anaerobic or oxygen-limited conditions (<700°C). It can be used as a soil conditioner to reduce salinity and nutrient loss in saline-alkali soils, improve soil physical and chemical properties and aggregate structure, and increase crop yields. In the present invention, biochar and basic fertilizer are mixed to form a granular core, which not only increases the content of multiple nutrients, but also the rich pore structure and surface groups in the biochar can lock nutrients by physical, chemical and other means, which helps to reduce fertilizer losses and improve fertilizer utilization.

[0048] γ-Polyglutamic acid has super hydrophilicity and water retention capacity, which greatly improves water / fertilizer utilization, balances soil pH, and improves soil pH. Sodium alginate is a commonly used immobilization carrier with excellent film-forming and ball-forming capabilities and is non-toxic to the environment. It can be used as a natural soil conditioner to promote the formation of soil aggregate structure, improve the internal pore space of the soil, coordinate the ratio of solid, liquid and gas in the soil, restore the natural colloid balance lost due to excessive soil burden and chemical pollution, increase soil biological activity, promote the release of fast-acting nutrients, facilitate root growth, and improve the stress resistance and resistance to continuous cropping of crops.

[0049] Sulfur can produce acidic substances under the action of microorganisms or hydrolysis, thereby neutralizing alkaline substances in saline-alkali soil, further reducing soil pH, improving soil structure and normal crop growth. In addition, sulfur, as one of the essential elements for plant growth and development, plays an important role in plant growth and development, and can also improve the effectiveness of other nutrients in the soil, improve plant nutritional conditions, and promote crop yields.

[0050] The present invention wraps sulfur with a highly hygroscopic outer layer of γ-polyglutamic acid / sodium alginate, which is not prone to moisture absorption; and the γ-polyglutamic acid / sodium alginate polymer is combined with insoluble sulfur and sprayed on the surface of the core particles to form a slow-release fertilizer, which can not only control the release of nutrients in the fertilizer to achieve a good slow-release effect, but also synergistically reduce the pH of saline-alkali land. In addition, all the raw materials used can be degraded to become high-quality organic materials, which are absorbed and utilized by microorganisms and crops, helping plants to improve quality and increase production, and effectively improving the soil environment of saline-alkali land.

[0051] The slow-release fertilizer for saline-alkali land of the present invention has strong functionality and good slow-release effect, improves soil aggregate structure, increases water and fertilizer utilization rate, synergistically reduces saline-alkali soil pH, increases nutrient and organic matter content in the soil, promotes plant growth and development, and improves soil microecology.

[0052] On the basis of the above-mentioned embodiments, the present invention provides the following specific examples to further illustrate the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. The experimental methods without specifying specific conditions in the following examples are usually based on the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by mass.

[0053] Embodiment 1:

[0054] This embodiment provides a slow-release fertilizer for saline-alkali land, and the preparation method thereof is as follows:

[0055] The weight ratio of nitrogen (urea) / phosphorus (superphosphate) / potassium (potassium sulfate) fertilizer is 35:30:20. Stir evenly and press into powder for later use.

[0056] The amount of biochar added was 10% of the fertilizer weight. The straw waste was carbonized at 500°C for 1 h under sealed conditions, and after cooling to room temperature, the carbonized product was crushed into biochar powder with a particle size of ≤0.5 mm.

[0057] The biochar powder was added to the nitrogen / phosphorus / potassium fertilizers, tumbled and stirred for 20 minutes, and granulated in a drum granulator to form granular cores with a particle size of less than 0.4 cm.

[0058] After 1‰ and 1‰ γ-polyglutamic acid and sodium alginate are uniformly mixed to obtain the first coating material powder / liquid. After preheating to 50-60°C, the first coating material powder / liquid is sprayed onto the surface of the granular core through an atomizing nozzle to form a first coating layer on the surface of the granular core.

[0059] Preheat 2% sulfur powder by weight of the fertilizer to 60-70° C., spray the sulfur powder on the surface of the first coating layer until the surface is evenly coated, and then form a second coating layer on the surface of the first coating layer.

[0060] The intermediate fertilizer particles with the second coating layer formed after cooling are transported to a coating machine and coated with 5‰ anti-caking agent (attapulgite) to obtain a slow-release fertilizer for saline-alkali land.

[0061] Embodiment 2:

[0062] This embodiment provides a slow-release fertilizer for saline-alkali land, and the preparation method thereof is as follows:

[0063] The weight ratio of nitrogen (ammonium nitrate) / phosphorus (diammonium phosphate) / potassium (potassium chloride) fertilizer is 40:35:30. Stir evenly and press into powder for later use.

[0064] The amount of biochar added was 20% of the fertilizer weight. The straw waste was carbonized at 400°C for 2 h under sealed conditions, and after cooling to room temperature, the carbonized product was crushed into biochar powder with a particle size of ≤0.5 mm.

[0065] The biochar powder was added to the nitrogen / phosphorus / potassium fertilizers, tumbled and stirred for 30 minutes, and granulated in a drum granulator to form granular cores with a particle size of less than 0.4 cm.

[0066] After 5‰ and 5‰ γ-polyglutamic acid and sodium alginate are uniformly mixed to obtain a first coating material powder / liquid, and the first coating material powder / liquid is sprayed onto the surface of the granular core to form a first coating layer on the surface of the granular core.

[0067] Preheat 3% sulfur powder by weight of the fertilizer to 60-70° C., spray the sulfur powder on the surface of the first coating layer until the surface is evenly coated, and then form a second coating layer on the surface of the first coating layer.

[0068] The intermediate fertilizer particles with the second coating layer formed after cooling are transported to a coating machine and coated with a 7‰ anti-caking agent (attapulgite) to obtain a slow-release fertilizer for saline-alkali land.

[0069] Embodiment 3:

[0070] This embodiment provides a slow-release fertilizer for saline-alkali land, and the preparation method thereof is as follows:

[0071] The weight ratio of nitrogen (urea) / phosphorus (diammonium phosphate) / potassium (potassium sulfate) fertilizer is 45:40:35. Stir evenly and press into powder for later use.

[0072] The amount of biochar added was 20% of the fertilizer weight. The straw waste was carbonized at 300°C for 3 h under sealed conditions, and after cooling to room temperature, the carbonized product was crushed into biochar powder with a particle size of ≤0.5 mm.

[0073] The biochar powder was added to the nitrogen / phosphorus / potassium fertilizers, tumbled and stirred for 30 minutes, and granulated in a drum granulator to form granular cores with a particle size of less than 0.4 cm.

[0074] After 10‰ and 10‰ γ-polyglutamic acid and sodium alginate are uniformly mixed to obtain a first coating material powder / liquid, and the first coating material powder / liquid is sprayed onto the surface of the granular core to form a first coating layer on the surface of the granular core.

[0075] Preheat 5% sulfur powder by weight of the fertilizer to 60-70° C., spray the sulfur powder on the surface of the first coating layer until the surface is evenly coated, and then form a second coating layer on the surface of the first coating layer.

[0076] The intermediate fertilizer particles with the second coating layer formed after cooling are transported to a coating machine and coated with 10‰ anti-caking agent (diatomaceous earth, talcum powder) to obtain a slow-release fertilizer for saline-alkali land.

[0077] Fertilizer application test:

[0078] A randomized block design plot experiment was carried out in saline-alkali soil in Chongming, Shanghai. Each plot was 1m×1.5m, with a total of 12 plots. Soil background values: pH 8.94, organic matter 2.37%, total nitrogen 0.70g / kg, total phosphorus (P 2 O 5 )0.84g / kg, total potassium (K 2 O) 12.15g / kg, total salt content 2.24g / kg.

[0079] Shanghai green was used as the planting object. Base fertilizer was applied before planting green vegetables. No fertilizer was applied during the entire growth period. Other field management activities were the same. The fertilization treatments were: application of conventional compound fertilizer treatment (nitrogen (urea) / phosphorus (superphosphate) / potassium (potassium sulfate) fertilizer, 20 kg / mu, CF), and a 30% reduction in the application of the slow-release fertilizer for saline-alkali land prepared in Examples 1-3 (14 kg / mu, T1, T2, T3). Three parallels were set up for each group. The planting period was 30 days, and the soil salinity, pH value, organic matter, green vegetable yield, vitamin C, nitrate nitrogen content and other parameters were measured at the harvest period. The specific results are shown in Tables 1 and 2.

[0080] Table 1 Soil parameters at harvest time

[0081]

[0082] Table 2 Parameters of green vegetables during harvest

[0083]

[0084] It can be seen that the above slow-release fertilizers used in saline-alkali land can reduce soil salinity and pH, among which T2 and T3 treatments have significant effects (P<0.05); increase soil organic matter content, among which T3 treatment has significant effect (P<0.05); and do not significantly affect soil catalase and sucrase activities. When fertilizer application is reduced by 30%, the plant height, spread, plant weight and yield of green vegetables are not significantly affected, and the yield increase range is 0.50%-3.97%; improve the quality of green vegetables, among which the vitamin C content of green vegetables in the T2 and T3 treatment groups is significantly increased (P<0.05), and the nitrate nitrogen content of green vegetables in the T1, T2 and T3 treatment groups is significantly reduced (P<0.05).

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A slow-release fertilizer for saline-alkali land, characterized in that: include: a granular core formed by co-granulating a base fertilizer composition with biochar powder; A first coating layer, formed on the surface of the granular core, is a mixture of γ-polyglutamic acid or its derivatives and sodium alginate; A second envelope layer, formed of sulfur on the surface of the first envelope layer; The third coating layer is formed on the surface of the second coating layer by an anti-caking agent.

2. The slow-release fertilizer for saline-alkali land according to claim 1, characterized in that: The added amounts of the biochar, γ-polyglutamic acid or its derivatives, sodium alginate, sulfur and anti-caking agent are 10%-40%, 1‰-10‰, 1‰-10‰, 2%-6% and 5‰-10‰ of the weight of the basic fertilizer composition, respectively.

3. The slow-release fertilizer for saline-alkali land according to claim 1, characterized in that: The particle size of the granular core is 0.2-0.4 cm.

4. The slow-release fertilizer for saline-alkali land according to any one of claims 1 to 3, characterized in that: The basic fertilizer composition is a composition of nitrogen fertilizer, phosphorus fertilizer and potassium fertilizer.

5. The slow-release fertilizer for saline-alkali land according to claim 4, characterized in that: The weight ratio of the nitrogen fertilizer, the phosphorus fertilizer and the potash fertilizer is 32-45:28-40:15-35.

6. The slow-release fertilizer for saline-alkali land according to claim 4, characterized in that: The nitrogen fertilizer is selected from one or two of urea and ammonium nitrate, the phosphate fertilizer is selected from at least one of superphosphate, diammonium phosphate or monoammonium phosphate, and the potash fertilizer is selected from at least one of potassium sulfate, potassium chloride or potassium dihydrogen phosphate.

7. The slow-release fertilizer for saline-alkali land according to any one of claims 1 to 3, characterized in that: The γ-polyglutamic acid or its derivative is any one of γ-polyglutamic acid, γ-polyglutamic acid derivative salts, and γ-polyglutamic acid fermentation culture.

8. The slow-release fertilizer for saline-alkali land according to any one of claims 1 to 3, characterized in that: The anti-caking agent is at least one of zeolite powder, attapulgite, diatomaceous earth, talc, limestone and silicon dioxide powder.

9. The method for preparing a slow-release fertilizer for saline-alkali land according to any one of claims 1 to 7, characterized in that: The steps include: S1. adding the biochar powder to the basic fertilizer composition, stirring evenly, and granulating in a drum granulator to form a granular core; S2. After γ-polyglutamic acid or its derivative is evenly mixed with sodium alginate, a powder or solution of a first coating material is obtained, which is sprayed on the surface of the granular core until the surface of the granular core is evenly coated, dried, and cooled to form a first coating layer on the surface of the granular core; S3. spraying sulfur preheated to 60-70°C onto the surface of the first coating layer until the surface of the first coating layer is evenly coated, drying, cooling, and forming a second coating layer on the surface of the first coating layer; S4. The anti-caking agent is uniformly coated on the surface of the second coating layer to form a third coating layer.

Images