Environment-friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer as well as preparation method and application thereof

Abstract

The invention discloses an environment-friendly straw shell-lac ethyl cellulose-based slow-release nitrogen fertilizer, a preparation method and application, shell-lac and ethyl cellulose are stirred and dissolved in absolute ethyl alcohol, straw and urea mixed powder is added into a shell-lac and ethyl cellulose mixed solution, dehumidification is performed after sufficient stirring, and a primary dehumidification mixed material is obtained after dehumidification is completed; and molding the primarily dehumidified mixed material into a cylindrical strip, and dehumidifying again to obtain a pre-pressed mixed material. And then placing the pre-pressed mixed material in a press machine for tabletting and forming, and continuously carrying out third dehumidification to obtain the primary slow-release nitrogen fertilizer. And uniformly spraying a proper amount of a sealing agent ethyl cellulose ethanol solution on the surface of the primary slow-release nitrogen fertilizer, and standing until the primary slow-release nitrogen fertilizer is naturally air-dried to obtain the environment-friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer. The method is applied to the field of chemical fertilizer preparation, the problem that straw is difficult to treat is solved, waste can be turned into wealth, straw resources are fully utilized, the straw is made into the slow-release nitrogen fertilizer, and the utilization efficiency of the nitrogen fertilizer can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmentally friendly fertilizer preparation methods, and in particular relates to an environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer, and also relates to a preparation method and application of the environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer. Background Art

[0002] Fertilization is an important way to achieve efficient agricultural development. Since conventional fertilizers release nutrients too quickly, they are difficult to be efficiently utilized by crops and will also cause many negative environmental pollution problems. The emergence of fertilizer nutrient slow-release technology provides an important solution for this. Due to the inherent properties of the raw materials, some existing slow-release fertilizers have problems such as poor slow-release performance and mechanical properties during production and field application. It is urgent to produce a low-cost, efficient and environmentally friendly slow-release fertilizer.

[0003] China is one of the world's largest producers of crop straw, with an annual output of more than 700 million tons. There are many disposal problems, such as land occupation due to stacking, pollution caused by burning, and pests and diseases induced by direct return to the field. The high value-added utilization of straw resources needs to be solved. Since straw is rich in cellulose, lignin and hemicellulose, using it as a fertilizer carrier can ensure the mechanical stability and long-lasting slow-release of fertilizers. This can not only solve the problem of straw treatment difficulties, but also achieve high value-added utilization of straw resources. In addition, straw resources are large in quantity, and using it as a skeleton material for slow-release fertilizers can also significantly reduce the production cost of slow-release fertilizers. Shellac is a natural bioadhesive polymer that is soluble in alkaline solutions and organic solvents (for example, anhydrous ethanol). The unique chemical composition and structure of shellac enable it to always maintain adhesion in diverse environments such as wet or dry, ensuring that the substrate it adheres to is not easy to fall off. Ethyl cellulose is a synthetic cellulose derivative with good chemical stability and can withstand chemical reactions such as acid, alkali and oxidation to a certain extent; it also has good biocompatibility and can be used as a coating material to delay the release rate of fertilizer nutrients.

[0004] Cellulose, lignin and hemicellulose contained in straw are the main components of crop straw. Straw fiber, as a slow-release fertilizer carrier, provides a good framework structure for urea powder, adhesive and slow-release agent, and improves the binding stability of various substances. Shellac can fill the pores between straw powder and urea powder, form a dense structure, and reduce the nutrient release channel. Ethyl cellulose coating can also act as a sealant to improve the hydrophobicity of slow-release fertilizers and improve the slow-release performance. Based on the extrusion granulation process, the air in the pores between the materials can be further discharged, the meshing force between the material particles can be improved, and the nitrogen fertilizer has better molding characteristics and mechanical properties. According to the above analysis, based on extrusion granulation and coating methods, the advantages of straw-shellac-ethyl cellulose are combined to produce a good-performance environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer, in order to solve the problems of waste of straw resources, high cost of slow-release fertilizers, and poor effect of ordinary nitrogen fertilizers, and provide a scientific basis for the production of slow-release nitrogen fertilizers in my country. Summary of the invention

[0005] The present invention also aims to provide an environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer.

[0006] The present invention also aims to provide a method for preparing an environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer, thereby solving the problems of waste of straw resources and high cost of slow-release fertilizer.

[0007] The present invention also aims to provide application of environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer.

[0008] The first technical solution adopted by the present invention is: an environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer, wherein the raw materials of the slow-release nitrogen fertilizer include shellac, urea powder, wheat straw powder, and ethyl cellulose. The mass ratio of shellac, urea powder, wheat straw powder, and ethyl cellulose is 0.8-1.2: 2-3: 2.9-3.6: 2.9-3.6.

[0009] The second technical solution adopted by the present invention is: a method for preparing an environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer, and the specific operating steps are as follows: Step 1: Weigh a certain amount of shellac into a beaker, add ethyl cellulose, and then use anhydrous ethanol to completely dissolve the two substances to obtain a mixed solution of shellac and ethyl cellulose; Step 2: Crush and sieve the wheat straw for later use, take the wheat straw and urea powder separately, mix them, add them into a beaker containing the mixed solution of shellac and ethyl cellulose, and stir them thoroughly to obtain a uniform mixture; Step 3: placing the mixed material in a constant temperature box for continuous dehumidification, stirring the material once every 0.4h~0.5h, and obtaining a primary dehumidified mixed material after dehumidification; Step 4: shaping the primary dehumidified mixed material into cylindrical strips, and performing secondary dehumidification again to obtain a pre-pressed mixed material; Step 5: directly placing the pre-pressed mixed material obtained in step 4 in a press to form tablets, and then placing it in a constant temperature box for three dehumidifications to obtain a primary slow-release nitrogen fertilizer; Step 6: Use an atomization spraying method to evenly coat the sealing agent on the surface of the primary slow-release nitrogen fertilizer, and after standing at room temperature, the environmentally friendly slow-release nitrogen fertilizer is obtained.

[0010] The present invention is also characterized in that: Furthermore, shellac is an adhesive; and ethyl cellulose is a sustained-release agent.

[0011] Furthermore, the mass ratio of shellac, urea powder, wheat straw powder and ethyl cellulose is 0.8-1.2:2-3:2.9-3.6:2.9-3.6; the mass ratio of ethyl cellulose to anhydrous ethanol in step 1 is 1:20-30.

[0012] Furthermore, the particle size of the urea and wheat straw powder is 0-300 um.

[0013] Furthermore, the single particle weight of the environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer is 0.5-0.6 g, the particle shape is cylindrical, the height is 3.5-15 mm, the diameter is 7-10 mm, and the aspect ratio is 0.5-1.5.

[0014] Furthermore, the first dehumidification time is 3 h ~ 3.5 h, the second dehumidification time is 1 h ~ 1.5 h; the third dehumidification time is 24 h ~ 36 h.

[0015] Furthermore, the tableting process parameters in step 5 are: pressure 2 t ~ 4t, compression time 1min ~ 1.5min.

[0016] Furthermore, the standing time at room temperature in step 6 is 1 d to 1.5 d.

[0017] Furthermore, the sealing agent in step 6 is an ethyl cellulose ethanol solution with a mass concentration of 7% to 12%.

[0018] The third technical solution adopted by the present invention is: application of environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer, applying the environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer to the planting of crops such as lettuce and corn, with the application amount of lettuce being 0.36-1.08 g / plant and the application amount of corn being 240 kg N / hm 2 .

[0019] The beneficial effects of the present invention are: 1. The raw materials required by the present invention are low-priced crop straws, which can reduce the production cost of slow-release fertilizers to a certain extent, and provide a new way for the high-value-added utilization of straw resources, thereby promoting sustainable agricultural development. After the slow-release fertilizers are degraded and their skeletons collapse, the straws are returned to the fields as organic fertilizers, which can also provide nutrients for crops, improve soil quality, and help improve the yield and quality of crops.

[0020] 2. Compared with other production methods, the slow-release agent-binder-urea composite material tablet preparation method of the present invention can produce a large number of tablet fertilizers in a short time, greatly improve production efficiency, and reduce fertilizer production energy consumption. In addition, the aspect ratio of the slow-release nitrogen fertilizer particles in the extrusion granulation method and the pressure during the molding process are optimized, and the optimal aspect ratio and granulation pressure are selected through experiments to enable the slow-release nitrogen fertilizer particles to have better slow-release performance and mechanical properties.

[0021] 3. The adhesive and slow-release agent used in this environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer have good performance and can greatly improve the slow-release performance and molding characteristics of the fertilizer particles. Shellac is a natural material with good biocompatibility, which is relatively friendly to the human body and the environment, and is not easily affected by moisture, temperature changes and chemical substances, and has a certain stability. After the skeleton of the slow-release fertilizer collapses after degradation, shellac can improve the soil structure after entering the soil, increase the water retention and permeability of the soil, promote the activity of microorganisms in the soil, and improve the fertility and water holding capacity of the soil. Ethyl cellulose is a non-toxic and biodegradable polymer with good hydrophobicity and stability, and can effectively slow down the release rate of nutrients in the fertilizer. The above materials are combined with urea powder to create a new type of slow-release nitrogen fertilizer with excellent comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a surface microscopic morphology of the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer sample of the present invention. DETAILED DESCRIPTION

[0023] The specific embodiments of the present invention are described in detail below.

[0024] Example 1 1.0g of shellac and 3.0g of ethyl cellulose were added to a beaker containing 60ml of anhydrous ethanol, and a magnetic stirrer was used to completely dissolve the shellac and ethyl cellulose; 3.0g of wheat straw powder with a particle size of 0-100um was mixed with 3.0g of urea powder with a particle size of 0-100um, and 6.0g of the straw-urea mixture was added to the mixed solution of shellac and ethyl cellulose. After sufficient stirring, the mixture was placed in a 35℃ constant temperature box for dehumidification for 3h, and the material was stirred every 0.5h to prevent it from agglomerating. After dehumidification, the primary dehumidified mixed material was obtained. The obtained primary dehumidified mixed material was then molded into a cylindrical strip and placed in a constant temperature box for secondary dehumidification for 1.5h to obtain a pre-pressed mixed material.

[0025] Clean the customized compression mold, take 0.5g of pre-compressed mixed material in a cylindrical compression mold with an inner cavity height of 5mm, a diameter of 10mm, and an aspect ratio of 0.5, place the mold in the specified position of the compressor, tighten the pressure relief valve, and manually pressurize to 4t for pressure holding operation. After continuous compression for 1-1.5min, release the pressure relief valve and take out the sample. Put it in a 35℃ constant temperature box for three dehumidifications for 1d to obtain a primary slow-release nitrogen fertilizer. Finally, an appropriate amount of sealant (ethyl cellulose ethanol solution) is evenly wrapped on the surface of the primary slow-release nitrogen fertilizer by atomization spraying method, and left to stand at room temperature for 1d to obtain the environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer described in the present invention.

[0026] The slow-release nitrogen fertilizer prepared by the present invention has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its slow-release performance and compressive strength are shown in Tables 1 and 2 below.

[0027] Comparative Example 1-1 Comparative Example 1-1 is different from Example 1 in that the component ratio, straw type and particle size are different, and the specific description is as follows: 0.8 g of shellac and 2.0 g of ethyl cellulose were added to a beaker containing 60 ml of anhydrous ethanol, and the shellac and ethyl cellulose were completely dissolved using a magnetic stirrer; 3.6 g of corn stalk powder with a particle size of 0-100 um was mixed with 3.6 g of urea powder with a particle size of 0-100 um, and 7.2 g of the stalk urea mixture was added to the mixed solution of shellac and ethyl cellulose. The subsequent preparation process and parameter settings were exactly the same as those in Example 1, and will not be repeated here.

[0028] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its slow-release performance and compressive strength are shown in Tables 1 and 2 below.

[0029] Comparative Example 1-2 Comparative Example 1-2 is different from Example 1 in that the component ratio, straw type and particle size are different, and the specific description is as follows: 1.2 g of shellac and 2.5 g of ethyl cellulose were added to a beaker containing 60 ml of anhydrous ethanol, and the shellac and ethyl cellulose were completely dissolved using a magnetic stirrer; 3.15 g of rice straw powder with a particle size of 0-100 um was mixed with 3.15 g of urea powder with a particle size of 0-100 um, and 6.3 g of the straw-urea mixture was added to the mixed solution of shellac and ethyl cellulose. The subsequent preparation process and parameter settings were exactly the same as those in Example 1, and will not be repeated here.

[0030] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its slow-release performance and compressive strength are shown in Tables 1 and 2 below.

[0031] Comparative Examples 1-3 Comparative Examples 1-3 differ from Example 1 in that the component ratios, straw types and particle sizes are different, and are specifically described as follows: 1.2 g of shellac and 2.0 g of ethyl cellulose were added to a beaker containing 60 ml of anhydrous ethanol, and the shellac and ethyl cellulose were completely dissolved using a magnetic stirrer; 3.4 g of wheat straw powder with a particle size of 100-200 um was mixed with 3.4 g of urea powder with a particle size of 0-100 um, and 6.8 g of the straw urea mixture was added to the mixed solution of shellac and ethyl cellulose. The subsequent preparation process and parameter settings were exactly the same as those in Example 1, and will not be repeated here.

[0032] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its slow-release performance and compressive strength are shown in Tables 1 and 2 below.

[0033] Comparative Examples 1-4 Comparative Examples 1-4 differ from Example 1 in that the component ratios, straw types and particle sizes are different, and are specifically described as follows: 0.8 g of shellac and 2.5 g of ethyl cellulose were added to a beaker containing 60 ml of anhydrous ethanol, and the shellac and ethyl cellulose were completely dissolved using a magnetic stirrer; 3.35 g of wheat straw powder with a particle size of 200-300 um was mixed with 3.35 g of urea powder with a particle size of 0-100 um, and 6.7 g of the straw urea mixture was added to the mixed solution of shellac and ethyl cellulose. The subsequent preparation process and parameter settings were exactly the same as those in Example 1, and will not be repeated here.

[0034] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its slow-release performance and compressive strength are shown in Tables 1 and 2 below.

[0035] Tables 1 and 2 show that when Example 1 is used, that is, wheat straw is selected, the particle size is 0-100 um, and the material component ratio is 1:3:3:3 by mass of adhesive (shellac), urea powder, wheat straw powder, and slow-release agent (ethyl cellulose). This formula is the best choice. At this time, the environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer formed by extrusion granulation has a longer slow-release duration and better mechanical properties, and can provide nutrients to crops better and more continuously.

[0036] Table 1 Dynamic cumulative release rate of nutrients from environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer

[0037] Table 2 Compressive strength of environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer

[0038] Example 2 1.0g of shellac and 3.0g of ethyl cellulose were added to a beaker containing 60ml of anhydrous ethanol, and a magnetic stirrer was used to completely dissolve the shellac and ethyl cellulose; 3.0g of wheat straw powder with a particle size of 0-100um was mixed with 3.0g of urea powder with a particle size of 0-100um, and 6.0g of the straw-urea mixture was added to the mixed solution of shellac and ethyl cellulose. After sufficient stirring, the mixture was placed in a 35℃ constant temperature box for dehumidification for 3h, and the material was stirred every 0.5h to prevent it from agglomerating. After dehumidification, the primary dehumidified mixed material was obtained. The obtained primary dehumidified mixed material was then molded into a cylindrical strip and placed in a constant temperature box for secondary dehumidification for 1.5h to obtain a pre-pressed mixed material.

[0039] Clean the customized compression mold, take 0.5g of the mixed material that is stirred evenly into a cylindrical compression mold with an inner cavity height of 8mm, a diameter of 8mm, and an aspect ratio of 1, place the mold in the specified position of the compressor, tighten the pressure relief valve, and manually pressurize to 4t for pressure holding operation. After continuous compression for 1 to 1.5 minutes, release the pressure relief valve and take out the sample. Put it in a 35℃ constant temperature box for three dehumidifications for 1d to obtain a primary slow-release nitrogen fertilizer. Finally, an appropriate amount of sealant (ethyl cellulose ethanol solution) is evenly wrapped on the surface of the primary slow-release nitrogen fertilizer by an atomization spraying method, and left to stand at room temperature for 1d to obtain the environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer described in the present invention.

[0040] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its mechanical indicators and slow-release properties are shown in Tables 3 and 4.

[0041] Comparative Example 2-1 Comparative Example 2-1 is different from Example 2 in that the compressor pressure during tableting is 2t, as follows: The preliminary preparation scheme is exactly the same as that in Example 2 and will not be repeated here. Clean the customized compression mold, take 0.5g of the evenly stirred mixture into a cylindrical compression mold with an inner cavity height of 8mm, a diameter of 8mm, and an aspect ratio of 1, place the mold in the specified position of the compressor, tighten the pressure relief valve, and manually pressurize to 2t for pressure maintenance. After the compression time is 1 to 1.5 minutes, release the pressure relief valve and take out the sample. The subsequent preparation scheme is also exactly the same as that in Example 2 and will not be repeated here.

[0042] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, and a relatively flat surface. Its mechanical indicators and slow-release properties are shown in Tables 3 and 4.

[0043] Comparative Example 2-2 Comparative Example 2-2 is different from Example 2 in that the compressor pressure during the granulation process is 3t, as follows: The preliminary preparation scheme is exactly the same as that in Example 2 and will not be repeated here. Clean the customized compression mold, take 0.5g of the mixed material that has been stirred evenly into a cylindrical compression mold with an inner cavity height of 8mm, a diameter of 8mm, and an aspect ratio of 1, place the mold in the specified position of the compressor, tighten the pressure relief valve, and manually pressurize to 3t for pressure maintenance. After the compression time is 1 to 1.5 minutes, release the pressure relief valve and take out the sample. The subsequent preparation scheme is also exactly the same as that in Example 2 and will not be repeated here.

[0044] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, a relatively flat surface, and its mechanical indicators and slow-release properties are shown in Tables 3 and 4. As shown in Tables 3 and 4, when Example 2 is adopted, that is, when the pressure of the compressor tablet is 4t, the better the compression resistance of the slow-release fertilizer, the better the mechanical stability, and the better the nutrient slow-release effect.

[0045] Table 3 Compressive strength of environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer

[0046] Table 4 Dynamic cumulative release rate of nutrients from environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer

[0047] Example 3 1.0g of shellac and 3.0g of ethyl cellulose were added to a beaker containing 60ml of anhydrous ethanol, and the shellac and ethyl cellulose were completely dissolved by a magnetic stirrer; 3.0g of wheat straw powder with a particle size of 0-100um was mixed with 3.0g of urea powder with a particle size of 0-100um, and 6.0g of the straw urea mixture was added to the mixed solution of shellac and ethyl cellulose. After sufficient stirring, the mixture was placed in a 35℃ constant temperature box for dehumidification for 3h, and the material was stirred every 0.5h to prevent it from agglomerating. After dehumidification, the primary dehumidified mixed material was obtained. The obtained primary dehumidified mixed material was then molded into a cylindrical strip and placed in a constant temperature box for secondary dehumidification for 1.5h to obtain a pre-pressed mixed material.

[0048] The customized compression mold was cleaned, and 0.5g of the mixed material was placed in a cylindrical compression mold with an inner cavity height of 8mm, a diameter of 8mm, and an aspect ratio of 1. The mold was placed in the specified position of the compressor, the pressure relief valve was tightened, and the pressure was maintained when the pressure was manually increased to 4t. After the compression time was 1-1.5min, the pressure relief valve was released and the sample was taken out. It was placed in a 35℃ constant temperature box for further dehumidification for 1d. After the dehumidification was completed, an appropriate amount of ethyl cellulose ethanol solution was evenly sprayed on its surface, and it was left to stand for 1d to dry naturally to obtain an environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer. The aspect ratio of the slow-release nitrogen fertilizer obtained met the requirements, the shape was regular, and the surface was relatively flat. Its mechanical indicators and slow-release performance results are shown in Tables 5 and 6.

[0049] Comparative Example 3-1 Comparative Example 3-1 is different from Example 3 in that the dimensions of the compression mold during tableting are 5 mm in height, 10 mm in diameter, and 0.5 in aspect ratio, as follows: The early preparation scheme is exactly the same as Example 3, and no further details are given. The customized compression mold is cleaned, 0.5g of the mixed material stirred is taken in a cylindrical compression mold with an inner cavity height of 5mm, a diameter of 10mm, and an aspect ratio of 0.5, and the mold is placed in a specified position of the compressor, and the pressure relief valve is tightened. When manually pressurized to 4t, a pressure-maintaining operation is performed, and after a continuous compression time of 1 to 1.5min, the pressure relief valve is released and the sample is taken out. Afterwards, the preparation scheme is also exactly the same as Example 3, and no further details are given. The aspect ratio of the obtained slow-release nitrogen fertilizer meets the requirements, and the shape is regular, and the surface is relatively flat, and its mechanical indexes and slow-release performance results are as shown in Tables 5 and 6.

[0050] Comparative Example 3-2 Comparative Example 3-2 is different from Example 3 in that the dimensions of the compression mold during tableting are 10.5 mm in height, 7 mm in diameter, and 1.5 in aspect ratio, as follows: The preliminary preparation scheme is exactly the same as that in Example 3 and will not be repeated here. Clean the customized compression mold, take 0.5g of the mixed material that has been stirred evenly into a cylindrical compression mold with an inner cavity height of 10.5mm, a diameter of 7mm, and an aspect ratio of 1.5, place the mold in the specified position of the compressor, tighten the pressure relief valve, and manually pressurize to 4t for pressure maintenance. After the compression time is 1 to 1.5 minutes, release the pressure relief valve and take out the sample. The subsequent preparation scheme is also exactly the same as that in Example 3 and will not be repeated here.

[0051] The obtained slow-release nitrogen fertilizer has an aspect ratio that meets the requirements, a regular shape, a relatively flat surface, and its mechanical indicators and slow-release performance are shown in Tables 5 and 6. It can be seen from Tables 5 and 6 that when Example 3 is adopted, that is, when the aspect ratio of the compression mold size is 1, the better the compression resistance of the slow-release fertilizer, the better the mechanical stability, and the better the nutrient slow-release effect.

[0052] Table 5 Compressive strength of environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer

[0053] Table 6 Dynamic cumulative release rate of nutrients from environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer

[0054] Example 4 The environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer prepared in Example 2 was applied to lettuce planting. The lettuce variety was loose leaf lettuce (fast-growing). This variety of lettuce has the characteristics of vigorous growth, good comprehensive resistance, cold resistance, and high yield, and is more suitable for planting in northern greenhouses. The fertilizer application effect of the present invention was evaluated by the lettuce growth index. After the lettuce was planted, 0.36 g of the environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer was added to the soil of each lettuce at one time during the lettuce seedling stage, and the physiological related indicators of lettuce growth were measured, and the yield quality related indicators of lettuce were measured during the harvest period. The application effect of the slow-release fertilizer on lettuce is shown in Tables 7 to 9.

[0055] Comparative Example 4-1 According to the method in Example 4, after the lettuce is planted, conventional urea with the same nitrogen application amount is added to the soil at the seedling stage. The same method is used to measure the growth physiology and yield quality related indicators of the lettuce, and the application effects are shown in Tables 7 to 9.

[0056] (1) Growth indicators: plant height, total root length, total root surface area, total root volume, etc., as shown in Table 7.

[0057] Table 7 Growth index of lettuce

[0058] (2) Physiological indicators: relative chlorophyll SPAD content, photosynthetic parameters (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration and transpiration rate, etc.), as shown in Table 8.

[0059] Table 8 Physiological indicators of lettuce

[0060] (3) The yield (fresh weight and dry weight) and quality indicators (vitamin C, soluble sugar and soluble protein content, etc.) at the harvest period are shown in Table 9.

[0061] Table 9 Lettuce yield and quality indicators

[0062] It can be seen from Tables 7 to 9 that when Example 4 is adopted, that is, the lettuce growth physiology is better, the yield is higher, and the nutrients are richer than those of conventional urea, so the present invention significantly improves the growth of lettuce.

[0063] Example 5 The environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer prepared in Example 2 was applied to lettuce planting. After the lettuce was planted, 1.08 g of the environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer was added to the soil of each lettuce plant at one time during the seedling stage, and the growth physiological related indicators of the lettuce were measured, and the yield and quality related indicators of the lettuce were measured during the harvest period. The application effect of the slow-release fertilizer on lettuce is shown in Tables 10 to 12.

[0064] Comparative Example 5-1 The environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer prepared in Example 2 was applied to lettuce planting. After the lettuce was planted, 0.36 g of the environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer was added to the soil of each lettuce plant at one time during the seedling stage, and the growth physiological related indicators of the lettuce were measured, and the yield and quality related indicators of the lettuce were measured during the harvest period. The application effect of the slow-release fertilizer on lettuce is shown in Tables 10 to 12.

[0065] Comparative Example 5-2 The environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer prepared in Example 2 was applied to lettuce planting. After the lettuce was planted, 0.72 g of the environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer was added to the soil of each lettuce plant at one time during the seedling stage, and the growth physiological related indicators of the lettuce were measured, and the yield quality related indicators of the lettuce were measured during the harvest period. The application effect of the slow-release fertilizer on lettuce is shown in Tables 10 to 12.

[0066] (1) Growth indicators: plant height, total root length, total root surface area, total root volume, etc., as shown in Table 10.

[0067] Table 10 Growth index of lettuce

[0068] (2) Physiological indicators: relative chlorophyll SPAD content, photosynthetic parameters (net photosynthetic rate, stomatal conductance, intercellular carbon dioxide concentration and transpiration rate, etc.), as shown in Table 11.

[0069] Table 11 Physiological indicators of lettuce

[0070] (4) The yield (fresh weight and dry weight) and quality indicators (vitamin C, soluble sugar and soluble protein content, etc.) at the harvest period are shown in Table 12.

[0071] Table 12 Lettuce yield and quality indicators

[0072] It can be seen from Tables 10 to 12 that when the environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer is used at an application rate of 1.08 g per lettuce, the yield is higher and the nutrients are richer. Therefore, the increase in the application rate of the fertilizer in the present invention significantly improves the growth of lettuce.

[0073] Example 6 The environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer prepared in Example 2 was applied to corn planting, using a wide-narrow row and a belt-two-row planting method, with a narrow row spacing of 40 cm and a wide row spacing of 1.2 m. Drip irrigation was used for irrigation, and the irrigation level was 100% of the actual evapotranspiration (ETC) of the crop. The application rate of the environmentally friendly straw / shellac / ethyl cellulose-based slow-release nitrogen fertilizer was 240 kg N / hm 2 The conventional urea application rate is also 240kg N / hm 2 At the harvest stage, the stem diameter, relative chlorophyll content of leaves, organ dry matter mass, yield and quality-related indicators of corn were measured. The results are shown in Table 13 below.

[0074] Comparative Example 6-1 According to the method in Example 6, 240 kg N / hm2 of 2 The conventional urea was used, and the rest of the planting method, irrigation method, etc. were exactly the same as those in Example 6. At the harvest time, the corn stem diameter, leaf relative chlorophyll content, organ dry matter mass, yield and quality related indicators were measured, and the results are shown in Table 13 below.

[0075] Table 13 Corn related indicators

[0076] As can be seen from Table 13, the corn using the environmentally friendly straw / shellac / ethyl cellulose based slow-release nitrogen fertilizer grows better than the corn using conventional urea, accumulates more dry matter, has a higher yield, and is richer in nutrients. Therefore, the present invention significantly improves the growth of corn.

[0077] The key innovative features of the present invention include: 1. As a bonding agent, shellac, in addition to acting as a resin to bond, can also effectively strengthen the adhesion between straw fibers, improve the tensile strength and tear resistance of straw fibers, and thus improve the mechanical strength of fertilizers; shellac itself has a certain tolerance to environmental factors (such as temperature, humidity, pH, etc.), and its structure is relatively stable and is not affected by factors such as moisture, thus avoiding the agglomeration and adhesion between fertilizers, making it easy to store and extending its shelf life; its slow-release effect is also relatively long-lasting; in addition, shellac is used as a slow-release carrier material, and there are a large number of hydroxyl groups on the surface of straw fibers. Hydrogen bonds can be formed between the hydroxyl groups of shellac molecules and the hydroxyl groups on the surface of straw fibers. The hydrogen bonds have a strong force, which can make the shellac and straw tightly bonded together, and have good mechanical and slow-release properties; shellac is soluble in alcohol, and will gradually dry and solidify after the alcohol solvent evaporates. In this process, the distance between shellac molecules decreases and the interaction between molecules increases. Its molecular chains are entangled and cross-linked with each other, forming a continuous bonding layer with straw fibers, ethyl cellulose and other materials, thereby bonding different materials together; since the surface of the straw material is relatively rough, shellac penetrates into the tiny pores and depressions on the surface of the straw material, and through mechanical interlocking, the bonding force between the materials is enhanced.

[0078] 2. The mass ratio of shellac, urea powder, wheat straw powder and ethyl cellulose in the present application is 0.8~1.2:2~3:2.9~3.6:2.9~3.6; relative to the prior art, under this ratio, the nitrogen content of the fertilizer prepared is moderate, which meets the nitrogen requirements of conventional crops. The overall material adhesion and mechanical properties are in a better range, which is conducive to the slow release of nutrients. Good mechanical properties ensure that the fertilizer is not easily damaged during production and transportation, and can maintain good stability during field soil application, and is not easily affected by storage, extrusion or mechanical tillage. Under this ratio, the obtained mixture has the best fluidity and ductility, which is conducive to the extrusion molding process. The composite material formed under this ratio has suitable adhesion, which is more conducive to the bonding effect between the materials.

[0079] 3. The binder, slow-release agent, urea and straw of the present invention can better penetrate each other, form a relatively tight structure after drying, improve the overall bonding strength of the material, and make the structure more stable. Shellac is a degradable material, and wheat straw is a biomass material, thereby giving the nitrogen fertilizer of the present invention a certain toughness and degradability. Ethyl cellulose, as a cellulose derivative, can enhance the flexibility and tensile strength of the material. Within the range of this ratio, the components interact with each other, so that the product achieves a better balance between toughness and strength, ensuring that the fertilizer product has a certain strength while improving the degradation and environmental protection of the fertilizer. Among the above-mentioned components, shellac is relatively expensive, but the dosage ratio is small. Urea is a product with huge industrial production capacity and relatively low cost. Wheat straw powder is a renewable agricultural waste with a wide source and relatively low cost. Under the conditions of this formula, the production cost of the entire material can be reduced by reasonably increasing the proportion of urea and straw components in the ratio while ensuring product quality and slow-release performance, which has certain economic advantages. Shellac, urea powder, wheat straw powder and ethyl cellulose are within a given ratio range, and the physical and chemical properties of each component are coordinated with each other, so that they can be dispersed more evenly during the mixing process. For example, in processing techniques such as stirring or extrusion, the components will not agglomerate or separate due to imbalance in the ratio, which may make the processing process smoother and improve production efficiency compared to the existing technology.

[0080] 4. The key process in the preparation method of this application is: (1) Dissolution and stirring process and parameters Add shellac and ethyl cellulose to anhydrous ethanol, use a magnetic stirrer to completely dissolve them, add the urea-straw mixture and stir thoroughly to ensure that the shellac, ethyl cellulose, straw, and urea powder are fully contacted and mixed, and evenly dispersed or dissolved in the ethanol solution. This is conducive to exerting the synergistic effect of each component in the slow-release nitrogen fertilizer, forming a slow-release nitrogen fertilizer with stable performance, and ensuring the consistency of fertilizer performance.

[0081] (2) Dehumidification process (primary dehumidification, secondary dehumidification, tertiary dehumidification) The purpose of primary dehumidification is to remove excess anhydrous ethanol, and the material gradually changes from liquid-viscous liquid to soft solid (i.e. primary dehumidified mixed material), making preliminary preparations for extrusion molding.

[0082] Purpose of secondary dehumidification: The primary dehumidified material is shaped into a cylindrical strip to facilitate entering the compression mold, but the humidity is still too high at this time, and extrusion will squeeze out anhydrous ethanol. And too much humidity will cause the internal structure to be not dense enough, so secondary dehumidification is performed.

[0083] The purpose of three dehumidifications: After extrusion molding, if the initial slow-release nitrogen fertilizer has too much humidity, it will affect the density of the fertilizer and thus affect the slow-release performance. Secondly, excessive humidity will also affect the mechanical properties of the fertilizer. The higher the humidity, the faster the nutrient release will be. Finally, excessive humidity will affect the viscosity of the sealant in subsequent steps, and the sealant will not be easy to adhere firmly to the surface of the fertilizer. If the humidity is too high, the cracks on the surface of the fertilizer will be occupied by the alcohol solution, and the sealant will not be able to fully fill the superficial gaps in the fertilizer, that is, the nutrient transmission and diffusion channels are not effectively closed, which will lead to excessive nutrient release.

[0084] Therefore, the three dehumidification processes have different purposes, but they complement each other and are indispensable, and together determine the physical and chemical properties of fertilizers. Through gradual dehumidification, the humidity of the material can be effectively controlled to avoid material agglomeration. At the same time, it helps to form a dense structure in the subsequent molding process, improve the molding characteristics and mechanical properties of the fertilizer, and also have a certain positive effect on the slow release performance of nutrients.

[0085] (3) Tablet forming process Through optimized pressure and aspect ratio, the materials can be tightly combined to ensure better mechanical stability of the fertilizer and form slow-release nitrogen fertilizer particles with better slow-release performance.

[0086] (4) Spray sealing process The atomization spray method is used to evenly wrap the surface of the primary slow-release nitrogen fertilizer with an ethyl cellulose ethanol solution with a mass concentration of 7%-12% as a sealant. The ethyl cellulose ethanol solution as a sealant can improve the hydrophobicity of the slow-release fertilizer, block the superficial cracks of the compressed fertilizer, seal the nutrient diffusion channel, further improve the slow-release performance, and make the fertilizer nutrient release slower and more lasting, thereby better meeting the growth needs of crops.

Claims

1. Environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer, characterized in that: The organic slow-release nitrogen fertilizer raw materials include shellac, urea powder, wheat straw powder and ethyl cellulose; the mass ratio of the shellac, urea powder, wheat straw powder and ethyl cellulose is 0.8-1.2:2-3:2.9-3.6:2.9-3.

6.

2. A method for preparing an environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer, characterized in that: The specific steps are as follows: Step 1: Weigh a certain amount of shellac into a beaker, add ethyl cellulose, and then use anhydrous ethanol to completely dissolve the two substances to obtain a mixed solution of shellac and ethyl cellulose; Step 2: Crush and sieve the wheat straw for later use, take the wheat straw and urea powder separately, mix them, add them into a beaker containing the mixed solution of shellac and ethyl cellulose, and stir them thoroughly to obtain a uniform mixture; Step 3: placing the mixed material in a constant temperature box for continuous dehumidification, stirring the material once every 0.4h~0.5h, and obtaining a primary dehumidified mixed material after dehumidification; Step 4: shaping the primary dehumidified mixed material into cylindrical strips, and performing secondary dehumidification again to obtain a pre-pressed mixed material; Step 5: directly placing the pre-pressed mixed material obtained in step 4 in a press to form tablets, and then placing it in a constant temperature box for three dehumidifications to obtain a primary slow-release nitrogen fertilizer; Step 6: Use an atomization spraying method to evenly coat the sealing agent on the surface of the primary slow-release nitrogen fertilizer, and obtain the environmentally friendly slow-release nitrogen fertilizer after standing at room temperature.

3. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The mass ratio of the shellac, urea powder, wheat straw powder and ethyl cellulose is 0.8-1.2:2-3:2.9-3.6:2.9-3.6; the mass ratio of the ethyl cellulose and anhydrous ethanol in step 1 is 1:20-30.

4. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The particle size of the urea and wheat straw powder is 0-300um.

5. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer has a single grain weight of 0.5-0.6 g, a cylindrical grain shape, a height of 3.5-15 mm, a diameter of 7-10 mm, and an aspect ratio of 0.5-1.

5.

6. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The first dehumidification time is 3 h ~ 3.5 h, the second dehumidification time is 1 h ~ 1.5 h; the third dehumidification time is 24 h ~ 36 h.

7. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The tableting process parameters in step 5 are: pressure 2 t ~ 4t, compression time 1min ~ 1.5min.

8. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The room temperature standing time in step 6 is 1 d to 1.5 d.

9. The method for preparing the environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer according to claim 2, characterized in that: The sealing agent in step 6 is an ethyl cellulose ethanol solution with a mass concentration of 7% to 12%.

10. Application of environmentally friendly straw shellac ethyl cellulose based slow-release nitrogen fertilizer, characterized in that: Environmentally friendly straw shellac ethyl cellulose-based slow-release nitrogen fertilizer was applied to crop planting, with the application rate for lettuce being 0.36-1.08 g / plant and for corn being 240 kg N / hm 2 .

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