CN111285740B - Special fertilizer for overcoming soil continuous cropping obstacle - Google Patents
Special fertilizer for overcoming soil continuous cropping obstacle Download PDFInfo
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- CN111285740B CN111285740B CN202010221709.XA CN202010221709A CN111285740B CN 111285740 B CN111285740 B CN 111285740B CN 202010221709 A CN202010221709 A CN 202010221709A CN 111285740 B CN111285740 B CN 111285740B
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- C—CHEMISTRY; METALLURGY
- C05—FERTILISERS; MANUFACTURE THEREOF
- C05B—PHOSPHATIC FERTILISERS
- C05B17/00—Other phosphatic fertilisers, e.g. soft rock phosphates, bone meal
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- C05G—MIXTURES OF FERTILISERS COVERED INDIVIDUALLY BY DIFFERENT SUBCLASSES OF CLASS C05; MIXTURES OF ONE OR MORE FERTILISERS WITH MATERIALS NOT HAVING A SPECIFIC FERTILISING ACTIVITY, e.g. PESTICIDES, SOIL-CONDITIONERS, WETTING AGENTS; FERTILISERS CHARACTERISED BY THEIR FORM
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Abstract
The invention discloses a special fertilizer for overcoming continuous cropping obstacles of soil, which is prepared by the following steps: step I, preparation of gel; II, preparing a fertilizer core; step III, preparing a hydrophobic inner-layer coating; and IV, preparing the water-retaining outer coating. The special fertilizer for overcoming the continuous cropping obstacle of the soil can not only regulate the growth and development of crops and inhibit the growth of pathogenic microorganisms, but also promote the maintenance of nutrient elements and soil fertility, energy conversion and substance circulation, relieve or eliminate the continuous cropping obstacle and maintain the stability and sustainability of a soil system.
Description
Technical Field
The invention relates to the technical field of crop planting, in particular to a special fertilizer for overcoming soil continuous cropping obstacles.
Background
The continuous cropping obstacle of crops is a worldwide problem, and refers to the phenomenon that after the crops of the same family or the same reason are continuously planted on the same soil, even under normal cultivation and management conditions, the crops have poor growth and development, weak growth vigor, reduced yield and quality and aggravated diseases and insect pests. In developed countries with large cultivation areas, modern agricultural scientific and technological means can be used for preventing and treating the continuous cropping obstacles, and the continuous cropping obstacles gradually become bottlenecks limiting the sustainable development of agriculture due to the fact that workers in China lack of knowledge about the continuous cropping obstacles and the planting mode and the management system are relatively lagged behind. The continuous cropping obstacles relate to a plurality of biological and non-biological factors such as crops, soil, environment and the like, are appearance manifestations of comprehensive effects of a plurality of factors in the soil microorganisms and the environment of the crops, and currently, the defects or unbalance of soil nutrients, the damage to the ecological environment of the soil, root secretion and the poison of residues of previous crops are commonly found to be important reasons for the generation of the continuous cropping obstacles. As the root system of the crop can selectively absorb the fertilizer and nutrients, particularly has special requirements on certain medium and trace elements, the continuous cropping of the same crop and the fertilization for a long time have relative fixity, and imbalance of soil nutrients is easily caused, so that the proportion of the nutrients in the crop is disordered and physiological and functional disorders are caused. In facility cultivation, in order to obtain high yield, the fertilizer input exceeds the utilization amount of plants and high evaporation of the facility cultivation, so that nutrients are obviously surface gathered while no rainwater is used for leaching, secondary salinization of soil is easy to generate, and physiological diseases are further aggravated.
The invention of application number 200610130054.5 discloses a biological soil additive formula for overcoming continuous cropping obstacles of vegetables, which comprises two microorganisms, non-metallic minerals, fermented organic fertilizers, industrial and agricultural waste residues and mineral trace elements. The components comprise the following weight ratio: 10% of functional microbial agent of trichoderma, 2% of VA arbuscular mycorrhizal agent, 6% of inorganic nonmetallic mineral zeolite, 69% of fermented organic fertilizer, 4% of shell powder, 7% of calcium superphosphate and 2% of urea. The method is widely applied to vegetable cultivation in a protected area with serious continuous cropping and has the effects of improving soil, promoting nutrient absorption of crops, increasing yield and preventing diseases.
Disclosure of Invention
The technical purpose of the invention is to provide a special fertilizer for overcoming the continuous cropping obstacle of soil, which is expected to play a role in reducing the cost, simplifying the preparation process, improving the soil, providing trace elements, improving the utilization rate of the fertilizer and the like.
The invention discloses a special fertilizer for overcoming continuous cropping obstacles of soil, which is prepared by the following steps:
preparation of gel in step I: weighing lignin or hydroxymethylated lignin, adding acrylamide, acrylic acid, sodium dihydrogen phosphate, potassium chloride and a crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding ammonium persulfate and ascorbic acid serving as initiators, and stirring for reaction to form hydrogel;
step II, preparation of fertilizer kernels: washing with water to remove unreacted monomer on the surface of the gel, drying, and pulverizing to obtain gel powder; adding copper potassium pyrophosphate, attapulgite clay and urea into the gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, spraying a binder in the granulation process by taking a rosin ethanol solution as a binder, and sieving to form a fertilizer core;
step III, preparation of the hydrophobic inner-layer coating: dissolving a starch-based material and a plasticizer in an organic solvent to prepare a starch-based solution; spraying a starch-based solution on the surface of the fertilizer core obtained in the step II, and forming fertilizer particles with surfaces coated with hydrophobic films after the organic solvent is volatilized;
step IV, preparation of the water-retaining outer-layer coating: coating the water-retaining agent on the outer layer of the fertilizer granules obtained in the step III to form a fertilizer outer layer coating; and drying and sieving the coated fertilizer granules to obtain the special fertilizer for overcoming the continuous cropping obstacle of the soil.
Further, the special fertilizer for overcoming the continuous cropping obstacle of the soil is prepared by the following steps:
preparation of gel in step I: weighing 0.5-2 g of lignin or hydroxymethylated lignin, adding 0.5-2 g of acrylamide, 0.5-2 g of acrylic acid, 0.3-1 g of sodium dihydrogen phosphate, 0.3-1 g of potassium chloride and 0.01-0.03 g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.1-0.3 mL of ammonium persulfate and 0.1-0.3 mL of ascorbic acid serving as initiators, and stirring in a water bath at 50-60 ℃ for reaction to form hydrogel;
step II, preparation of fertilizer kernels: washing with water to remove unreacted monomer on the surface of the gel, drying, and pulverizing to obtain gel powder; adding 0.1-0.3 g of copper potassium pyrophosphate, 5-10 g of attapulgite clay and 5-20 g of urea into 5-15 g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, spraying a binder in the granulation process by taking a rosin ethanol solution with the mass fraction of 20-40% as the binder to form a fertilizer core;
step III, preparation of the hydrophobic inner-layer coating: dissolving a starch-based material and a plasticizer in an organic solvent, wherein the mass of the plasticizer is 0.1-0.4 times that of the starch-based material, and preparing a starch-based solution with the mass fraction of 2-4%; spraying a starch-based solution on the surface of the fertilizer core obtained in the step II, and forming fertilizer particles with surfaces coated with hydrophobic films after the organic solvent is volatilized;
step IV, preparation of the water-retaining outer coating: putting the fertilizer granules obtained in the step III and the water-retaining agent into a disc, rotating the disc, and wrapping the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; and drying and sieving the coated fertilizer granules at 40-70 ℃ to obtain the special fertilizer for overcoming the continuous cropping obstacle of the soil.
Further, the copper potassium pyrophosphate is synthesized according to the following method: respectively preparing a copper sulfate solution with the concentration of 0.1-1 mol/L and pyrophosphoric acid with the concentration of 0.1-1 mol/LA potassium solution; adding the copper sulfate solution into the potassium pyrophosphate solution under stirring until Cu2+And P2O7 4-To a molar ratio of 1: 1; standing the reaction solution at 25-30 ℃ for 16-24 hours, filtering, and collecting a filter cake; and drying the filter cake to obtain the copper potassium pyrophosphate.
The attapulgite clay is a chain layered silicate clay mineral with a nano structure in one dimension, and has larger specific surface area and cation exchange capacity. In addition, it is rich in elements including potassium, phosphorus, calcium, magnesium, silicon, iron, manganese, etc.
Nitrogen, phosphorus and potassium are the three major elements most important for the growth and development of crops. Nitrogen is a major constituent of proteins and plays an important role in the growth of plant stems and leaves and the development of fruits. The phosphorus element can accelerate cell division, promote root system to grow rapidly and improve fruit quality. The potassium element can improve the intensity of photosynthesis, promote the formation of starch and sugar in crops, and enhance the stress resistance and disease resistance of the crops. Copper is a trace element necessary for the normal development of plants, is a component of various enzymes in the plant body, and is closely related to the synthesis of chlorophyll, carbohydrates and proteins. The gel powder, the low water-solubility copper potassium pyrophosphate, the attapulgite clay and the urea are used as the main components of the fertilizer core, so that the environmental hazard caused by the loss of the traditional fertilizer is avoided.
In some embodiments of the present invention, the starch-based material is acetate starch.
Further, the acetate starch is synthesized according to the following method: adding 3-10 g of corn starch into a reaction device, heating to 110-120 ℃, adding 10-30 g of acetic anhydride, and stirring for 20-40 minutes; then, adding 1-2 mL of sodium hydroxide aqueous solution with the mass fraction of 1-5%, and stirring for reaction for 3-6 hours; after the reaction is finished, adding 3-10 g of distilled water into the reaction device, centrifuging for 20-40 minutes at 3000-9000 revolutions per minute, and collecting bottom sediment; washing the precipitate with distilled water until the washing liquid is neutral, drying at 50-60 ℃, and crushing and sieving to obtain the acetate starch.
The method comprises the steps of reacting starch with acetic anhydride to enable hydroxyl on a glucose unit in starch molecules to undergo esterification reaction, so as to prepare acetate starch with high substitution degree, and the acetate starch is used as a novel coating material of the fertilizer. The solubility of the starch in an organic solvent is greatly improved due to the fact that hydrogen bonding between hydroxyl groups of the original starch is broken, and the introduction of ester groups enables the acetate starch to have good hydrophobicity.
In some technical schemes of the invention, the starch-based material is a compound of acetate starch and organically modified montmorillonite.
The starch-based material is a compound of acetate starch and organic modified montmorillonite, and is obtained by the following method: crushing montmorillonite to the particle size of 100-500 nm; adding the mixture into a 0.1-1 mol/L p-phenylenediamine solution according to a feed-liquid ratio of 1: (40-90) (g/mL) adding nano montmorillonite, stirring for 1-2 hours at 300-600 revolutions per minute, centrifuging for 10-30 minutes at 4000-9000 revolutions per minute, and collecting bottom solids; drying the bottom solid at 50-60 ℃ for 2-4 hours to obtain organic modified montmorillonite; the organic modified montmorillonite and acetate starch are mixed according to the mass ratio (0.02-0.06): 1, uniformly mixing, and stirring at 300-600 rpm for 2-4 hours to obtain the starch-based material which is a compound of acetate starch and organic modified montmorillonite.
The nano montmorillonite filler is effectively distributed in the acetate starch to form an intercalation, more micropores are formed, microphase separation is generated, and the nano montmorillonite nano composite material not only can effectively wrap the fertilizer, but also is beneficial to improving the water retention performance and the fertilizer retention performance of the fertilizer.
Further, the hydroxymethylated lignin is synthesized according to the following method: putting 10-20 g of lignin and 100-300 g of formaldehyde solution with the mass fraction of 2-5% in a reaction device, adjusting the pH of the solution to 10-12 by using 1-10 mol/L sodium hydroxide, and heating to 70-80 ℃; reacting for 3-6 hours at 70-80 ℃, adjusting the pH to 2-3 by using 1-5 mol/L hydrochloric acid, centrifuging for 20-30 minutes at 3000-9000 revolutions/minute, and collecting bottom precipitates; washing the bottom precipitate with water until the washing liquid is neutral, and performing vacuum freeze drying to obtain the hydroxymethylated lignin.
Compared with lignin, hydroxymethylated lignin has enhanced hydrophilicity on one hand, and is beneficial to the release and utilization of fertilizers; on the other hand, hydroxymethylated lignin is a three-dimensional network structure, can play a role in loosening the structure, and improves the coating effect.
Further, the organic solvent is one or a mixture of more of ethyl acetate, n-hexane, toluene, xylene, octane, cyclohexane, cyclohexanone, dichloromethane, methanol, ethanol and isopropanol.
Furthermore, the usage amount of the adhesive in the step II is 1-2% of the mass of the mixture.
Further, the step III plasticizer is glyceryl triacetate and/or citric acid ester. More preferably, the plasticizer is a mixture of triacetin and citric acid ester, wherein the mass ratio of triacetin to citric acid ester is 1: 1.
further, the mass ratio of the acetate starch solution in the step III to the fertilizer core is 1: (10-20).
Further, the mass ratio of the water-retaining agent to the fertilizer granules in the step IV is 1: (20-40).
The present invention solves the following problems: in the prior art, high fertilization level causes low fertilizer utilization rate, and causes serious resource waste and economic loss; and the soil structure is damaged and the water and fertilizer retention capacity is deteriorated due to unreasonable fertilization, and the yield increasing benefit of the fertilizer is reduced; the nitrogen, phosphorus and other elements which are applied to the soil but not utilized are leached and permeated, and are transferred to the water body, so that the water body is eutrophicated.
The invention has the following advantages:
1. the utilization rate of the fertilizer is effectively improved, and the nutrient loss caused by inconsistent fertilization amount and crop absorption is reduced; 2. the fertilizer is safe to use, and the seedling burning phenomenon caused by overlarge local concentration of the fertilizer in the soil due to excessive fertilization can be avoided; 3. the slow release performance of the fertilizer can be adjusted according to the fertilizer requirement rule of crops, so that the nutrient absorption of the root system of the crops is improved, and the leaching and volatilization loss is reduced to the maximum extent; 4. reduce the fertilization number of times, reduce labour cost.
The special fertilizer for overcoming the continuous cropping obstacle of the soil can not only regulate the growth and development of crops and inhibit the growth of pathogenic microorganisms, but also promote the maintenance of nutrient elements and soil fertility, energy conversion and substance circulation, relieve or eliminate the continuous cropping obstacle and maintain the stability and sustainability of a soil system.
Detailed Description
The raw materials in the examples are as follows:
lignin, CAS No.: 8068-05-1, available from Baichuan chemical Co., Ltd.
Acrylamide, CAS No.: 79-06-1.
Acrylic acid, CAS No.: 79-10-7.
Sodium dihydrogen phosphate, CAS No.: 89140-32-9.
Potassium chloride, CAS number: 7447-40-7.
N, N-methylenebisacrylamide, CAS No.: 110-26-9.
Ammonium persulfate, CAS number: 7727-54-0.
Ascorbic acid, CAS number: 50-81-7.
The potassium copper pyrophosphate was synthesized as follows: respectively preparing a copper sulfate solution with the concentration of 0.1mol/L and a potassium pyrophosphate solution with the concentration of 0.1 mol/L; under the condition of stirring at 100 revolutions per minute, the copper sulfate solution is slowly dripped into the potassium pyrophosphate solution at the speed of 1mL/min until Cu2+And P2O7 4-To a molar ratio of 1: 1; standing the reaction solution at 25 ℃ for 24 hours, filtering by using 200-mesh filter cloth, and collecting a filter cake; and drying the filter cake at 50 ℃ for 12 hours to obtain the copper potassium pyrophosphate.
The attapulgite clay has the granularity of 200 meshes, is provided by a mountain stream town geoid attapulgite processing plant in Mingguang City, and has the chemical composition of a commodity number 8567:
| composition (I) | SiO2 | Al2O3 | CaO | MgO | Fe2O3 | K2O | P2O5 | MnO |
| wt％ | 51.43 | 16.47 | 3.42 | 5.87 | 6.14 | 3.56 | 0.28 | 0.06 |
Urea, offered by environmental protection technologies ltd, xinbi source, Tianjin.
Rosin, CAS No.: 8050-09-7.
Preparation of acetate starch: adding 5g of corn starch into a reaction device, heating to 120 ℃ at the speed of 5 ℃/min, adding 20g of acetic anhydride, and stirring for 20 min at the speed of 100 r/min; then, 1.1mL of a 1% by mass aqueous solution of sodium hydroxide was added dropwise at 0.1mL/min, and the reaction was stirred at 100 rpm for 5 hours; after the reaction is finished, 5g of distilled water is added into the reaction device, the mixture is centrifuged for 20 minutes at 4000 revolutions per minute, and bottom sediment is collected; washing the precipitate with distilled water until the washing liquid is neutral, drying at 50 deg.C for 12 hr, pulverizing, and sieving with 80 mesh sieve to obtain the acetate starch.
Triacetin, CAS No.: 102-76-1.
The montmorillonite is specifically montmorillonite provided by Guangzhou hundred million peaking Industrial technology, Henan, origin, 400 mesh.
P-phenylenediamine, CAS No.: 106-50-3.
Preparation of water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid: dissolving 3g of itaconic acid in 80mL of distilled water in a reaction device provided with a stirrer and an air duct under the protection of nitrogen, adding 5mL of 7mol/L potassium hydroxide aqueous solution, and stirring for 10 minutes at 100 revolutions per minute; subsequently, 12g of acrylamide, 0.08g of ammonium persulfate, 0.04g N, N' -methylenebisacrylamide and 1g of humic acid were added, and stirred at 100 rpm for 30 minutes; finally, 0.1g of guar gum is added, and the mixture is placed in a water bath at the temperature of 75 ℃ to be stirred and react for 3 hours; after the reaction is finished, cooling the reaction liquid to 30 ℃, performing vacuum freeze drying, crushing and sieving with a 150-mesh sieve to obtain the water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid.
Itaconic acid, CAS number: 97-65-4.
Humic acid, CAS number: 1415-93-6.
Guar, CAS number: 9000-30-0.
Preparation of water-retaining agent carboxymethyl cellulose-hydroxyethyl cellulose: dissolving 15g of carboxymethyl cellulose in 750mL of distilled water to obtain a carboxymethyl cellulose aqueous solution; dissolving 7.5g of hydroxyethyl cellulose in 150mL of distilled water to obtain a hydroxyethyl cellulose aqueous solution; uniformly mixing a carboxymethyl cellulose aqueous solution and a hydroxyethyl cellulose aqueous solution, adding 0.7g of citric acid, and stirring at 90 ℃ at 100 revolutions per minute for 2 hours of reaction; after the reaction is finished, cooling the reaction liquid to 30 ℃, freezing and drying in vacuum, crushing and sieving with a 150-mesh sieve to obtain the water retention agent carboxymethyl cellulose-hydroxyethyl cellulose.
Carboxymethyl cellulose, CAS No.: 9004-32-4.
Hydroxyethyl cellulose, CAS No.: 9004-62-0.
Citric acid, CAS No.: 77-92-9.
Preparing a water retention agent carboxymethyl starch-xanthan gum: dissolving 15g of xanthan gum and 8g of carboxymethyl potato starch in 1000mL of distilled water, stirring for 30 minutes at 100 revolutions per minute, adding 0.1g of sodium hydroxide and 0.6g of sodium trimetaphosphate, and reacting for 2 hours at 80 ℃ with stirring at 100 revolutions per minute; after the reaction is finished, cooling the reaction liquid to 30 ℃, performing vacuum freeze drying, crushing and sieving with a 150-mesh sieve to obtain the water-retaining agent carboxymethyl starch-xanthan gum.
Xanthan gum, CAS No.: 11138-66-2.
The carboxymethyl potato starch is prepared by referring to the preparation process and characteristic research of carboxymethyl potato starch (proceedings of university of Gansu agriculture, No. 4 of 8 months, 2011, 118-123) of Yuyu Fei, and the specific process conditions are as follows: the starch milk concentration is 16 percent, the mass ratio of monochloroacetic acid to starch is 0.11, the mass ratio of sodium hydroxide to starch is 0.09, the temperature is 45 ℃, the etherification reaction time is 6 hours, and the degree of substitution is 0.84.
Sodium trimetaphosphate, CAS number: 7785-84-4.
Example 1
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of lignin, adding 0.5g of acrylamide, 1.5g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, stirring and reacting for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and forming gel through free radical polymerization;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving acetate starch and plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the acetate starch, and preparing an acetate starch solution with the mass fraction of 3%; and (3) spraying an acetate starch solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the acetate starch solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Example 2
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of lignin, adding 1.0g of acrylamide, 1.0g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, stirring and reacting for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and forming gel through free radical polymerization;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving acetate starch and plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the acetate starch, and preparing an acetate starch solution with the mass fraction of 3%; and (3) spraying an acetate starch solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the acetate starch solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Example 3
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of lignin, adding 1.5g of acrylamide, 0.5g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, stirring and reacting for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and forming gel through free radical polymerization;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving acetate starch and plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the acetate starch, and preparing an acetate starch solution with the mass fraction of 3%; and (3) spraying an acetate starch solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the acetate starch solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Comparative example 1
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of lignin, adding 2g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid serving as initiators, stirring and reacting for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and forming gel through free radical polymerization;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving acetate starch and plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the acetate starch, and preparing an acetate starch solution with the mass fraction of 3%; and (3) spraying an acetate starch solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the acetate starch solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Comparative example 2
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of lignin, adding 2g of acrylamide, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, stirring and reacting for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and forming gel through free radical polymerization;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving acetate starch and plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the acetate starch, and preparing an acetate starch solution with the mass fraction of 3%; and (3) spraying an acetate starch solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the acetate starch solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Example 4
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of hydroxymethylated lignin, adding 1.0g of acrylamide, 1.0g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, carrying out stirring reaction for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and carrying out free radical polymerization to form gel;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving acetate starch and plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the acetate starch, and preparing an acetate starch solution with the mass fraction of 3%; and (3) spraying an acetate starch solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the acetate starch solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
The hydroxymethylated lignin is synthesized according to the following method: placing 12g of lignin and 100g of formaldehyde solution with the mass fraction of 2% in a reaction device, adjusting the pH of the solution to 11 by using 1mol/L sodium hydroxide, and heating to 80 ℃ at the speed of 2 ℃/min; after reacting at 80 ℃ for 3 hours, adjusting the pH to 2 by using 5mol/L hydrochloric acid, centrifuging at 4000 rpm for 30 minutes, and collecting bottom sediment; washing the bottom sediment with deionized water until the washing liquor is neutral, and carrying out vacuum freeze drying to obtain the hydroxymethylated lignin.
Example 5
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of hydroxymethylated lignin, adding 1.0g of acrylamide, 1.0g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, carrying out stirring reaction for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and carrying out free radical polymerization to form gel;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving a starch-based material and a plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the starch-based material, and preparing a starch-based solution with the mass fraction of 3%; and (3) spraying a starch-based solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the starch-based solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water-retaining agent guar gum-poly (itaconic acid-acrylamide) -humic acid into a disc, wherein the mass ratio of the guar gum-poly (itaconic acid-acrylamide) -humic acid to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Hydroxymethylated lignin was synthesized according to the following method: placing 12g of lignin and 100g of formaldehyde solution with the mass fraction of 2% in a reaction device, adjusting the pH of the solution to 11 by using 1mol/L sodium hydroxide, and heating to 80 ℃ at the speed of 2 ℃/min; after reacting at 80 ℃ for 3 hours, adjusting the pH to 2 by using 5mol/L hydrochloric acid, centrifuging at 4000 rpm for 30 minutes, and collecting bottom sediment; washing the bottom sediment with deionized water until the washing liquor is neutral, and carrying out vacuum freeze drying to obtain the hydroxymethylated lignin.
The starch-based material is a compound of acetate starch and organic modified montmorillonite, and is obtained by the following method: montmorillonite is crushed to the particle size of 100 nm; adding the mixture into a 1mol/L p-phenylenediamine solution according to a feed-liquid ratio of 1: adding nano montmorillonite into 50(g/mL), stirring for 2 hours at 300 r/min, centrifuging for 30 minutes at 4000 r/min, and collecting the bottom solid; drying the bottom solid at 60 ℃ for 4 hours to obtain the organic modified montmorillonite; organically modified montmorillonite and acetate starch are mixed according to a mass ratio of 0.06: 1, and stirring for 2 hours at 300 r/min to obtain the starch-based material which is a compound of acetate starch and organic modified montmorillonite.
Example 6
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of hydroxymethylated lignin, adding 1.0g of acrylamide, 1.0g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, carrying out stirring reaction for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and carrying out free radical polymerization to form gel;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving a starch-based material and a plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the starch-based material, and preparing a starch-based solution with the mass fraction of 3%; and (3) spraying a starch-based solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the starch-based solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water retention agent of carboxymethyl cellulose-hydroxyethyl cellulose in a disc, wherein the mass ratio of the carboxymethyl cellulose to the hydroxyethyl cellulose to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Hydroxymethylated lignin was synthesized according to the following method: placing 12g of lignin and 100g of formaldehyde solution with the mass fraction of 2% in a reaction device, adjusting the pH of the solution to 11 by using 1mol/L sodium hydroxide, and heating to 80 ℃ at the speed of 2 ℃/min; after reacting at 80 ℃ for 3 hours, adjusting the pH to 2 by using 5mol/L hydrochloric acid, centrifuging at 4000 rpm for 30 minutes, and collecting bottom sediment; washing the bottom sediment with deionized water until the washing liquor is neutral, and carrying out vacuum freeze drying to obtain the hydroxymethylated lignin.
The starch-based material is a compound of acetate starch and organic modified montmorillonite, and is obtained by the following method: montmorillonite is crushed to the particle size of 100 nm; adding the mixture into a 1mol/L p-phenylenediamine solution according to a feed-liquid ratio of 1: adding nano montmorillonite into 50(g/mL), stirring for 2 hours at 300 r/min, centrifuging for 30 minutes at 4000 r/min, and collecting the bottom solid; drying the bottom solid at 60 ℃ for 4 hours to obtain the organic modified montmorillonite; organically modified montmorillonite and acetate starch are mixed according to a mass ratio of 0.06: 1, and stirring for 2 hours at 300 r/min to obtain the starch-based material which is a compound of acetate starch and organic modified montmorillonite.
Example 7
The special fertilizer for overcoming the continuous cropping obstacle of soil is prepared by the following steps:
preparation of gel in step I: weighing 1g of hydroxymethylated lignin, adding 1.0g of acrylamide, 1.0g of acrylic acid, 0.5g of sodium dihydrogen phosphate, 0.5g of potassium chloride and 0.02g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.2mL of ammonium persulfate and 0.2mL of ascorbic acid as initiators, carrying out stirring reaction for 2 hours in a water bath at 50 ℃ at 100 revolutions per minute, and carrying out free radical polymerization to form gel;
step II, preparation of fertilizer kernels: washing the gel with deionized water 70 times the weight of the gel to remove unreacted monomers on the surface of the gel, drying at 60 ℃ for 4 hours, and crushing into powder with the granularity of 300 meshes by using a crusher to obtain gel powder; adding 0.25g of copper potassium pyrophosphate, 6g of attapulgite clay and 8g of urea into 10g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, taking a rosin ethanol solution with the mass fraction of 30% as an adhesive, spraying the adhesive in the granulation process, and sieving to form a fertilizer core with the particle size of 2mm, wherein the usage amount of the adhesive is 2% of the weight of the mixture;
III, preparation of a hydrophobic inner-layer coating: dissolving a starch-based material and a plasticizer glyceryl triacetate in ethyl acetate, wherein the addition amount of the glyceryl triacetate is 0.2 times of the mass of the starch-based material, and preparing a starch-based solution with the mass fraction of 3%; and (3) spraying a starch-based solution on the surface of the fertilizer core obtained in the step (II), wherein the mass ratio of the starch-based solution to the fertilizer core is 1: 10, after ethyl acetate volatilizes, forming fertilizer particles with surfaces coated with hydrophobic films;
IV, preparation of the water-retaining outer coating: placing the fertilizer particles obtained in the step III and a water retention agent carboxymethyl starch-xanthan gum into a disc, wherein the mass ratio of the carboxymethyl starch-xanthan gum to the fertilizer particles is 1: 20, rotating the disc to wrap the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying the coated fertilizer granules at 45 ℃ for 6 hours, and sieving to obtain the special fertilizer with the granularity of 3mm and capable of overcoming the continuous cropping obstacle of the soil.
Hydroxymethylated lignin was synthesized according to the following method: placing 12g of lignin and 100g of formaldehyde solution with the mass fraction of 2% in a reaction device, adjusting the pH of the solution to 11 by using 1mol/L sodium hydroxide, and heating to 80 ℃ at the speed of 2 ℃/min; after reacting at 80 ℃ for 3 hours, adjusting the pH to 2 by using 5mol/L hydrochloric acid, centrifuging at 4000 rpm for 30 minutes, and collecting bottom sediment; washing the bottom sediment with deionized water until the washing liquor is neutral, and carrying out vacuum freeze drying to obtain the hydroxymethylated lignin.
The starch-based material is a compound of acetate starch and organic modified montmorillonite, and is obtained by the following method: montmorillonite is crushed to the particle size of 100 nm; adding the mixture into a 1mol/L p-phenylenediamine solution according to a feed-liquid ratio of 1: adding nano montmorillonite into 50(g/mL), stirring for 2 hours at 300 r/min, centrifuging for 30 minutes at 4000 r/min, and collecting the bottom solid; drying the bottom solid at 60 ℃ for 4 hours to obtain the organic modified montmorillonite; organically modified montmorillonite and acetate starch are mixed according to a mass ratio of 0.06: 1, and stirring for 2 hours at 300 r/min to obtain the starch-based material which is a compound of acetate starch and organic modified montmorillonite.
Example 8
Essentially the same as example 7, except that: the plasticizer is replaced by citric acid ester from glyceryl triacetate.
Example 9
Essentially the same as example 7, except that: replacing the plasticizer with a mixture of glyceryl triacetate and citric acid ester from glyceryl triacetate, wherein the mass ratio of the glyceryl triacetate to the citric acid ester is 1: 1.
test example 1
The special fertilizer for overcoming the soil continuous cropping obstacle in the embodiments 1-4 and the comparative examples 1-2 is subjected to a soil leaching test, and the specific operation steps are as follows: a PVC cylindrical pipe with the diameter of 10cm and the height of 30cm is adopted, the bottom of the pipe is sealed by 200-mesh gauze, and 25g of sand is filled; loading 250g of soil dried at 80 ℃ and sieved by a 200-mesh sieve, tightly filling, loading 250g of soil-fertilizer mixture (400mg N/kg soil) into the pipe with the same compactness, and loading 25g of sand into the pipe to prevent the soil from scattering after being dissolved by water; adding 150mL of water on day 1, culturing at room temperature, and adding 200mL of water for leaching every 3 days; sampling is carried out for 28 days, and soil columns without fertilizers are taken as reference.
The specific test results are shown in table 1.
Table 1 soil leaching test result table
The special fertilizer for overcoming the continuous cropping obstacle of the soil has the nitrogen, phosphorus and potassium release rates of over 96 percent, 93 percent and 85 percent respectively within 28 days. As can be seen from table 1, the fertilizer special for overcoming the continuous cropping obstacle of the soil in the examples 1 to 3 has a smaller initial release rate and a longer slow release time than those in the comparative examples 1 to 2, which is probably due to the formation of a pore structure with a uniform and regular size when the mass ratio of acrylic acid to acrylamide is 1:1, and the pore structure facilitates the absorption, retention and transportation of the fertilizer; and the lower the toughness of the formed hydrogel colloid is, the more easily the hydrogel colloid is cracked, so that the contact area of the hydrogel is increased, and the release of nutrients is accelerated.
Test example 2
The soil water holding capacity of the special fertilizer for overcoming the soil continuous cropping obstacle in the embodiment 2 and the embodiments 4 to 9 is measured: uniformly mixing a sample to be detected with 200g of dry soil (passing through a 26-mesh screen), placing the sample to be detected and the dry soil in a polyvinyl chloride tube with the diameter of 4.5cm in a mass ratio of 3%, sealing the bottom of the tube by using 100-mesh non-woven fabric, weighing the earth pillar and recording as W1. Slowly adding a certain amount of tap water from the upper end of the soil column until water begins to seep out from the bottom, namely reaching the maximum water holding capacity of the soil, standing for 2 weeks, and weighing the soil column again (marked as W) when no more water seeps out from the bottom of the soil column2). Blank experiments (without the sample to be tested) were performed under the same conditions.
The maximum water holdup (WH%) of the soil was recorded as calculated as follows: WH% ((W))2-W1)×100/200。
The specific test results are shown in table 2.
Table 2 table of maximum water holding rate test results of soil
As can be seen from Table 2, by using a combination of hydrophobic starch acetate and a water retaining agent in the present invention, a film with moderate toughness is formed on the surface of the fertilizer core. Moreover, by controlling the compositions of the plasticizer and the hydrophobic substance, the water absorption and retention capacity of the soil is effectively improved, and the aim of controlling the release of nutrients and effectively retaining water is fulfilled.
Test example 3
And (3) carrying out crop planting tests on the special fertilizer for overcoming the soil continuous cropping obstacle in the embodiment 2 and the embodiments 4-9, wherein the test crops specifically adopt Haifeng No. 27 hot peppers.
The soil to be tested is soil for continuous cropping of a greenhouse for 10 years, and the basic indexes are as follows: pH5.80, 29.7g/kg of organic matter, 2.60g/kg of total nitrogen, 136.5g/kg of quick-acting phosphorus and 374.8g/kg of quick-acting potassium.
The operation steps are as follows:
firstly, white plastic pots with the size of 25cm multiplied by 8cm multiplied by 6cm are used as cultivation vessels, each pot is filled with crushed and sieved with air-dried soil 2.5kg, and the soil is lightly compacted in the filling process. The mass percentage of the special fertilizer for overcoming the soil continuous cropping obstacle and the soil is 2%, the special fertilizer for overcoming the soil continuous cropping obstacle of the embodiment 2 and the embodiments 4-9 are respectively applied, each small pot carries 4 seedlings, and each treatment is repeated for 3 times.
Seed disinfection and germination acceleration: rinsing the selected seeds with distilled water, washing off surface dirt, drying with filter paper, wrapping with clean gauze, soaking in ethanol with volume fraction of 70% for 30 s, sterilizing with 1% potassium permanganate for 2 times, each time for 10 min, rinsing with sterile water, and sowing in quartz sand for germination acceleration, and taking care of water and illumination management.
Management and seedling transplantation in seedling stage: and when the seedlings grow to 2-3 true leaves, dividing the seedlings, and transplanting 4 seedlings of the pepper which are disease-free, robust and uniform in growth vigor in each pot.
Collecting and measuring plant samples: and when the pepper seedlings grow for 3 months, collecting the root systems of the plants without diseases and insect pests and the leaves of the same growing parts to measure the growth vigor of the plants.
And (3) sample determination: harvesting after culturing for 3 months, measuring the plant height by a conventional method, recording the fresh weight of the plant, deactivating enzyme, drying at 70 ℃ to constant weight, and measuring the dry weight of the plant; the TTC method is used for measuring the activity of the plant root system; measuring the green content of leaves by SPAD-502 provided by Hangzhou Hui Er Instrument and Equipment Co., Ltd, measuring 10 points on each leaf, avoiding veins during measurement, and measuring the relative content of chlorophyll by taking the average value as a result; the malondialdehyde content was measured spectrophotometrically.
The specific tests are shown in Table 3.
TABLE 3 Table of pepper plant assay results
It should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art will be able to make the description as a whole, and the embodiments may be appropriately combined to form other embodiments as will be appreciated by those skilled in the art.
Claims (7)
1. The special fertilizer for overcoming the continuous cropping obstacle of soil is characterized by being prepared by the following steps:
preparation of gel in step I: weighing 0.5-2 g of hydroxymethylated lignin, adding 0.5-2 g of acrylamide, 0.5-2 g of acrylic acid, 0.3-1 g of sodium dihydrogen phosphate, 0.3-1 g of potassium chloride and 0.01-0.03 g of crosslinking agent N, N-methylene bisacrylamide, uniformly mixing, adding 0.1-0.3 mL of ammonium persulfate and 0.1-0.3 mL of ascorbic acid serving as initiators, and stirring in a water bath at 50-60 ℃ for reaction to form hydrogel;
step II, preparation of fertilizer kernels: washing with water to remove unreacted monomer on the surface of the gel, drying, and pulverizing to obtain gel powder; adding 0.1-0.3 g of copper potassium pyrophosphate, 5-10 g of attapulgite clay and 5-20 g of urea into 5-15 g of gel powder, and uniformly mixing to obtain a mixture; putting the mixture into a disc granulator, spraying a binder in the granulation process by taking a rosin ethanol solution with the mass fraction of 20-40% as the binder to form a fertilizer core;
step III, preparation of the hydrophobic inner-layer coating: dissolving a starch-based material and a plasticizer in an organic solvent, wherein the mass of the plasticizer is 0.1-0.4 times that of the starch-based material, and preparing a starch-based solution with the mass fraction of 2-4%; spraying a starch-based solution on the surface of the fertilizer core obtained in the step II, and forming fertilizer particles with surfaces coated with hydrophobic films after the organic solvent is volatilized;
step IV, preparation of the water-retaining outer coating: putting the fertilizer granules obtained in the step III and the water-retaining agent into a disc, rotating the disc, and wrapping the water-retaining agent on the outer layer of the fertilizer granules to form a fertilizer outer layer coating; drying and sieving the coated fertilizer granules at 40-70 ℃ to obtain the special fertilizer for overcoming the continuous cropping obstacle of the soil;
the hydroxymethylated lignin is synthesized according to the following method: putting 10-20 g of lignin and 100-300 g of formaldehyde solution with the mass fraction of 2-5% in a reaction device, adjusting the pH of the solution to 10-12 by using 1-10 mol/L sodium hydroxide, and heating to 70-80 ℃; reacting for 3-6 hours at 70-80 ℃, adjusting the pH to 2-3 by using 1-5 mol/L hydrochloric acid, centrifuging for 20-30 minutes at 3000-9000 revolutions/minute, and collecting bottom precipitates; washing the bottom precipitate with water until the washing liquid is neutral, and performing vacuum freeze drying to obtain hydroxymethylated lignin;
the starch-based material is a compound of acetate starch and organically modified montmorillonite.
2. The special fertilizer for overcoming the continuous cropping obstacle of the soil as claimed in claim 1, wherein the potassium copper pyrophosphate is synthesized by the following method: respectively preparing a copper sulfate solution with the concentration of 0.1-1 mol/L and a potassium pyrophosphate solution with the concentration of 0.1-1 mol/L; adding the copper sulfate solution into the potassium pyrophosphate solution under the stirring condition until the molar ratio of Cu2+ to P2O 74-reaches 1: 1; standing the reaction solution at 25-30 ℃ for 16-24 hours, filtering, and collecting a filter cake; and drying the filter cake to obtain the copper potassium pyrophosphate.
3. The special fertilizer for overcoming the soil continuous cropping obstacle as recited in claim 1, wherein the organic solvent is one or a mixture of ethyl acetate, n-hexane, toluene, xylene, octane, cyclohexane, cyclohexanone, dichloromethane, methanol, ethanol and isopropanol.
4. The special fertilizer for overcoming the continuous cropping obstacle of soil as claimed in claim 1, wherein the usage amount of the binder in the step II is 1-2% of the mass of the mixture.
5. The special fertilizer for overcoming the soil continuous cropping obstacle as recited in claim 1, wherein said step III plasticizer is triacetin and/or citrate.
6. The special fertilizer for overcoming the soil continuous cropping obstacle as claimed in claim 1, wherein the mass ratio of the acetate starch solution in the step III to the fertilizer core is 1: (10-20).
7. The special fertilizer for overcoming the continuous cropping obstacle of soil as claimed in claim 1, wherein the mass ratio of the water retention agent to the fertilizer granules in step IV is 1: (20-40).
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