Slow-release base fertilizer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of slow-release fertilizers, and particularly discloses a slow-release base fertilizer which comprises a composite base fertilizer inner layer, a middle slow-release layer and a water-retaining outer layer which are sequentially arranged from inside to outside, the composite base fertilizer inner layer is made of a composite base fertilizer inner layer material, the middle slow-release layer is made of a slow-release carrier, and the water-retaining outer layer is made of a water-retaining agent; a chitosan connecting layer is also arranged between the middle slow-release layer and the composite base fertilizer inner layer. According to the slow-release base fertilizer and the preparation method and application thereof, the slow-release base fertilizer plays a slow-release role while increasing the crop yield, so that the nutrient utilization rate of the fertilizer is increased, the raw materials of the slow-release base fertilizer are easy to obtain, the production cost of the slow-release base fertilizer can be effectively controlled, and the slow-release base fertilizer can be popularized and used on a large scale.

Description

Technical Field

[0001] The invention belongs to the technical field of slow-release fertilizers, and in particular relates to a slow-release base fertilizer and a preparation method and application thereof. Background Art

[0002] Food is the foundation of people's livelihood. As the most populous country in the world, China has known since ancient times that "food is the first necessity of the people". Food security and stability are directly related to the long-term stability of the country and the well-being of the people. my country is not only a major food consumer, but also a major food producer. This status plays a vital role in the global agricultural landscape.

[0003] Fertilizer is an important guarantee for increasing grain production. Domestic and foreign practices have proved that among all the factors that increase production, only the amount of fertilizer applied is linearly correlated with grain products. The utilization rate of chemical fertilizers in my country is low, and the utilization rate of fertilizers decreases with the increase of fertilizer application. Moreover, excessive fertilizer application will also cause excess nutrients in the soil. Therefore, scientifically balanced fertilization and improving fertilizer utilization are particularly important for grain production. Therefore, research on fertilizer utilization, especially research on fertilizer controlled release, has become the focus of fertilizer research.

[0004] Water, as the lifeline of agriculture, is also an important factor limiting agricultural production. In my country's arid, semi-arid and desert areas, due to perennial water shortage, water resources are scarce and their utilization rate is low.

[0005] Therefore, how to improve fertilizer nutrients and water resource utilization is crucial to agricultural production and development. Water-retaining slow-release fertilizers are thus produced. The current water-retaining slow-release fertilizers have low water absorption, complex production, high costs, and are difficult to promote and use. Summary of the invention

[0006] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a slow-release basal fertilizer and a preparation method and application thereof. The slow-release basal fertilizer can increase crop yield and improve the nutrient utilization rate of the fertilizer. The raw materials of the slow-release basal fertilizer are easily available, the production cost can be effectively controlled, and it can be promoted and used on a large scale.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, the present invention provides a slow-release base fertilizer, comprising a composite base fertilizer inner layer, a middle slow-release layer and a water-retaining outer layer sequentially arranged from the inside to the outside;

[0009] The material of the inner layer of the composite base fertilizer is the inner layer material of the composite base fertilizer, the material of the middle slow-release layer is a slow-release carrier, and the material of the water-retaining outer layer is a water-retaining agent;

[0010] A chitosan connecting layer is also provided between the intermediate slow-release layer and the inner layer of the composite base fertilizer;

[0011] The composite base fertilizer inner layer material comprises the following raw materials in parts by weight: 10 parts of base fertilizer, 10-40 parts of slow-release carrier, and 4-10 parts of urea-formaldehyde resin;

[0012] The mass ratio of the composite base fertilizer inner layer, the chitosan connecting layer, the middle slow-release layer and the water-retaining outer layer is 1:(0.1-0.2):(1-3):(1-4).

[0013] Furthermore, the base fertilizer is any one or more of urea, ammonium dihydrogen phosphate, and potassium dihydrogen phosphate mixed in any proportion.

[0014] Furthermore, the preparation method of the composite base fertilizer inner layer material comprises the following steps: according to the composite base fertilizer formula, weighing the base fertilizer, slow-release carrier, and urea-formaldehyde resin, mixing the slow-release carrier and base fertilizer and adding them to the reactor, then adding cyclohexane, stirring for a certain period of time, adding a paste of urea-formaldehyde resin adhesive to the mixture, pouring it into a grinder again and mixing it, drying it, and granulating it with a granulator to obtain the composite base fertilizer inner layer material.

[0015] Furthermore, the preparation method of the sustained-release carrier is as follows:

[0016] Step 1: purify the bentonite, sieve it, place it at 200-400°C for 2h, and then cool it to room temperature to prepare activated bentonite for later use;

[0017] Step 2: Prepare a chitosan aqueous solution with a concentration of 1-5%, then pipette acetic acid into a beaker, stir to completely dissolve the chitosan, and prepare a chitosan solution for later use;

[0018] Step 3: Evenly mix the prepared chitosan solution and activated bentonite to prepare a mixed solution, wherein the mass ratio of chitosan to activated bentonite in the mixed solution is 1:(1-10), and the mixture is stirred and reacted for 2-4 hours, and the floccules produced after the reaction are washed with deionized water until neutral, and dried at 60-80°C for 12 hours to prepare a sustained-release carrier.

[0019] Furthermore, the preparation method of the water-retaining agent comprises the following steps:

[0020] Step (1): Weigh starch and dissolve it in water to prepare a starch solution for later use;

[0021] Step (2): weigh acrylic acid into a reactor, add deionized water, slowly add sodium hydroxide solution in an ice water bath, then add chitosan, stir to dissolve, prepare a mixed solution A, and set aside;

[0022] Step (3): Mix the mixed solution A with the starch solution, pass nitrogen, heat to 40-60°C, add an initiator and a cross-linking agent, irradiate with ultraviolet light, stir until the solution becomes viscous, stop stirring, and continue to react for 2-6 hours under nitrogen protection. After the reaction product is circulated and washed, it is dried in an oven at 50-90°C for 3-6 hours to prepare a water retaining agent.

[0023] Furthermore, the initiator is ammonium persulfate, and the cross-linking agent is N,N-dimethylacrylamide.

[0024] Furthermore, the ratio of the added amounts of acrylic acid, starch and chitosan is 1:(0.06-0.20):(0.01-0.03);

[0025] The mass ratio of the added amount of the initiator to the total added amount of acrylic acid, starch and chitosan is (0.1-1.0):100, and the mass ratio of the added amount of the crosslinking agent to the total added amount of acrylic acid, starch and chitosan is (0.01-0.05):100.

[0026] Furthermore, the process of the cyclic washing is: firstly, the reaction product is rinsed with deionized water, then immersed in 1% acetic acid solution for 10 seconds, and the above operation is repeated 3-5 times.

[0027] In a second aspect, the present invention provides a method for preparing a slow-release basal fertilizer, the preparation method comprising the following steps:

[0028] S1: According to the formula of slow-release base fertilizer, weigh the inner layer material of composite base fertilizer, slow-release carrier, water retaining agent, and prepare 1-5% chitosan solution;

[0029] S2: using acetic acid vapor to wrap the chitosan solution around the outside of the inner layer of the composite base fertilizer to form a coating material 1;

[0030] S3: coating the sustained-release carrier on the outside of the coating material 1 by passing water vapor to form the coating material 2;

[0031] S4: The water retaining agent is coated on the outside of the coating material 2 by passing water vapor to prepare a slow-release base fertilizer.

[0032] In a third aspect, the present invention provides an application of the slow-release base fertilizer provided by an embodiment of the first aspect of the present invention in agricultural planting.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention provides a slow-release basal fertilizer and a preparation method and application thereof. The slow-release basal fertilizer not only increases crop yield, but also plays a slow-release role, thereby improving the nutrient utilization rate of the fertilizer. The raw materials of the slow-release basal fertilizer are easily available, and its production cost can be effectively controlled, and it can be promoted and used on a large scale.

[0035] 2. In the present invention, the slow-release base fertilizer has a multi-layer structure, the innermost layer is the composite base fertilizer inner layer, which is mainly composed of base fertilizer, slow-release carrier and urea-formaldehyde resin. The slow-release carrier is made of activated bentonite loaded with chitosan as raw material, which not only plays a slow-release role, but also can adsorb heavy metal ions in the soil; the middle layer is the slow-release layer, and its main raw material is the slow-release carrier, which plays a layer-by-layer slow-release role; the outermost layer is the water-retaining outer layer, and its material is a water-retaining agent. The water-retaining agent adopts a chitosan-starch-acrylic acid system, the raw materials are easy to obtain, the preparation process is simple, and it not only has a good water absorption effect, but also can be used in slow-release fertilizers, and can also play a positive role in improving the physical properties of the soil.

[0036] 3. In the present invention, the preparation process of the multi-layered slow-release base fertilizer is simple and suitable for large-scale promotion and use of the slow-release base fertilizer. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In a first aspect, the present invention provides a slow-release base fertilizer, comprising a composite base fertilizer inner layer, a middle slow-release layer and a water-retaining outer layer sequentially arranged from the inside to the outside;

[0039] The material of the inner layer of the compound base fertilizer is the inner layer material of the compound base fertilizer, the material of the middle slow-release layer is the slow-release carrier, and the material of the water-retaining outer layer is the water-retaining agent; a chitosan connecting layer is also provided between the middle slow-release layer and the inner layer of the compound base fertilizer;

[0040] The composite base fertilizer inner layer material includes the following raw materials in terms of weight: 10 parts of base fertilizer, 10-40 parts of slow-release carrier, and 4-10 parts of urea-formaldehyde resin; wherein the base fertilizer is any one or more of urea, diammonium phosphate, and dipotassium phosphate mixed in any proportion;

[0041] The mass ratio of the composite base fertilizer inner layer, the chitosan connecting layer, the middle slow-release layer, and the water-retaining outer layer is 1:(0.1-0.2):(1-3):(1-4);

[0042] The preparation method of the composite base fertilizer inner layer material comprises the following steps: according to the composite base fertilizer formula, weighing the base fertilizer, the slow-release carrier and the urea-formaldehyde resin, mixing the slow-release carrier and the base fertilizer and adding them into a reactor, then adding cyclohexane, stirring for a certain time, adding a paste urea-formaldehyde resin adhesive into the mixture, pouring it into a grinder again and mixing it, drying it, and granulating it with a granulator to obtain the composite base fertilizer inner layer material;

[0043] The preparation method of the sustained-release carrier is as follows:

[0044] Step 1: purify the bentonite, sieve it, place it at 200-400°C for 2h, and then cool it to room temperature to prepare activated bentonite for later use;

[0045] Step 2: Prepare a chitosan aqueous solution with a concentration of 1-5%, then pipette acetic acid into a beaker, stir to completely dissolve the chitosan, and prepare a chitosan solution for later use;

[0046] Step 3: uniformly mixing the prepared chitosan solution and activated bentonite to prepare a mixed solution, wherein the mass ratio of chitosan to activated bentonite in the mixed solution is 1:(1-10), stirring and reacting for 2-4 hours, washing the floccules produced after the reaction with deionized water until neutral, and drying at 60-80° C. for 12 hours to prepare a sustained-release carrier;

[0047] The preparation method of the water retaining agent comprises the following steps:

[0048] Step (1): Weigh starch and dissolve it in water to prepare a starch solution for later use;

[0049] Step (2): weigh acrylic acid into a reactor, add deionized water, slowly add sodium hydroxide solution in an ice water bath, then add chitosan, stir to dissolve, prepare a mixed solution A, and set aside;

[0050] Step (3): Mixing the mixed solution A with the starch solution, passing nitrogen, heating to 40-60° C., adding an initiator and a cross-linking agent, irradiating with ultraviolet light, stirring until the solution becomes viscous, stopping stirring, and continuing to react for 2-6 hours under nitrogen protection, washing the reaction product in a cycle, and drying it in an oven at 50-90° C. for 3-6 hours to prepare a water retaining agent;

[0051] In the preparation method of the water-retaining agent, the initiator is ammonium persulfate and the cross-linking agent is N,N-dimethylacrylamide;

[0052] The ratio of the added amount of acrylic acid, starch and chitosan is 1:(0.06-0.20):(0.01-0.03);

[0053] The mass ratio of the added amount of the initiator to the total added amount of acrylic acid, starch and chitosan is (0.1-1.0):100, and the mass ratio of the added amount of the cross-linking agent to the total added amount of acrylic acid, starch and chitosan is (0.01-0.05):100;

[0054] The process of cyclic washing is: first rinse the reaction product with deionized water, then soak it in 1% acetic acid solution for 10 seconds, and repeat the above operation 3-5 times.

[0055] In a second aspect, the present invention provides a method for preparing a slow-release basal fertilizer, the preparation method comprising the following steps:

[0056] S1: According to the formula of slow-release base fertilizer, weigh the inner layer material of composite base fertilizer, slow-release carrier, water retaining agent, and prepare 1-5% chitosan solution;

[0057] S2: using acetic acid vapor to wrap the chitosan solution around the outside of the inner layer of the composite base fertilizer to form a coating material 1;

[0058] S3: coating the sustained-release carrier on the outside of the coating material 1 by passing water vapor to form the coating material 2;

[0059] S4: The water retaining agent is coated on the outside of the coating material 2 by passing water vapor to prepare a slow-release base fertilizer.

[0060] The third invention provides an application of the slow-release base fertilizer provided by an embodiment of the first aspect of the invention in agricultural planting.

[0061] The following are specific examples. In the following examples, unless otherwise specified, all raw materials can be obtained from commercial sources.

[0062] Example 1

[0063] The present embodiment provides a slow-release base fertilizer, comprising a composite base fertilizer inner layer, an intermediate slow-release layer and a water-retaining outer layer, which are sequentially arranged from the inside to the outside. The material of the composite base fertilizer inner layer is a composite base fertilizer inner layer material, the material of the intermediate slow-release layer is a slow-release carrier, the material of the water-retaining outer layer is a water-retaining agent, and a chitosan connecting layer is further arranged between the intermediate slow-release layer and the composite base fertilizer inner layer. The mass ratio of the composite base fertilizer inner layer, the chitosan connecting layer, the intermediate slow-release layer and the water-retaining outer layer is 1:0.15:2:3.

[0064] The composite base fertilizer inner layer material includes the following raw materials in terms of weight: 10 parts of base fertilizer, 20 parts of slow-release carrier, and 6 parts of urea-formaldehyde resin; wherein the base fertilizer is prepared by mixing urea and diammonium phosphate in a mass ratio of 1:1;

[0065] The preparation method of the composite base fertilizer inner layer material comprises the following steps: according to the composite base fertilizer formula, weighing the base fertilizer, the slow-release carrier, and the urea-formaldehyde resin, mixing the slow-release carrier and the base fertilizer and adding them into the reactor, then adding cyclohexane, stirring for a certain period of time, adding the paste urea-formaldehyde resin adhesive into the mixture, pouring it into a grinder again, mixing it, drying it, and granulating it with a granulator to obtain the composite base fertilizer inner layer material;

[0066] The preparation method of the sustained-release carrier is as follows: purifying bentonite and sieving it, calcining it at 300°C for 2h, and then cooling it to room temperature to prepare activated bentonite for use; preparing a chitosan aqueous solution with a concentration of 2%, then transferring acetic acid to a beaker, stirring to completely dissolve the chitosan, preparing a chitosan solution for use; mixing the prepared chitosan solution and the activated bentonite evenly to prepare a mixed solution, wherein the mass ratio of chitosan to activated bentonite in the mixed solution is 1:5, stirring and reacting for 3h, washing the flocs produced after the reaction with deionized water until neutral, and drying at 70°C for 12h to prepare a sustained-release carrier;

[0067] The preparation method of the water retaining agent comprises the following steps:

[0068] Step (1): Weigh starch and dissolve it in water to prepare a starch solution for later use;

[0069] Step (2): weighing acrylic acid into a reactor, adding deionized water, slowly adding sodium hydroxide solution in an ice water bath, and then adding chitosan, stirring to dissolve, preparing a mixed solution A for standby use; wherein the ratio of the added amounts of acrylic acid, starch and chitosan is 1:0.12:0.02;

[0070] Step (3): Mixing the mixed solution A with the starch solution, passing nitrogen, heating to 50° C., adding an initiator, ammonium persulfate, and a cross-linking agent, N,N-dimethylacrylamide, irradiating with ultraviolet light, stirring until the solution becomes viscous, stopping stirring, and continuing to react for 3 hours under nitrogen protection, and after cyclically washing the reaction product, drying it in an oven at 60° C. for 4 hours to prepare a water retaining agent;

[0071] The mass ratio of the added amount of the initiator to the total added amount of acrylic acid, starch and chitosan is 0.5:100, and the mass ratio of the added amount of the cross-linking agent to the total added amount of acrylic acid, starch and chitosan is 0.02:100.

[0072] The process of cyclic washing is as follows: firstly, the reaction product is rinsed with deionized water, then immersed in 1% acetic acid solution for 10 seconds, and the above operation is repeated 4 times.

[0073] This embodiment also provides a method for preparing a slow-release basal fertilizer, which comprises the following steps:

[0074] S1: According to the formula of slow-release base fertilizer, weigh the inner layer material of composite base fertilizer, slow-release carrier, water retaining agent, and prepare 1-5% chitosan solution;

[0075] S2: using acetic acid vapor to wrap the chitosan solution around the outside of the inner layer of the composite base fertilizer to form a coating material 1;

[0076] S3: coating the sustained-release carrier on the outside of the coating material 1 by passing water vapor to form the coating material 2;

[0077] S4: The water retaining agent is coated on the outside of the coating material 2 by passing water vapor to prepare a slow-release base fertilizer.

[0078] Example 2

[0079] The present embodiment provides a slow-release base fertilizer, comprising a composite base fertilizer inner layer, an intermediate slow-release layer and a water-retaining outer layer, which are sequentially arranged from the inside to the outside. The material of the composite base fertilizer inner layer is a composite base fertilizer inner layer material, the material of the intermediate slow-release layer is a slow-release carrier, the material of the water-retaining outer layer is a water-retaining agent, and a chitosan connecting layer is further arranged between the intermediate slow-release layer and the composite base fertilizer inner layer. The mass ratio of the composite base fertilizer inner layer, the chitosan connecting layer, the intermediate slow-release layer and the water-retaining outer layer is 1:0.2:1:4.

[0080] The composite base fertilizer inner layer material includes the following raw materials in terms of weight: 10 parts of base fertilizer, 10 parts of slow-release carrier, and 10 parts of urea-formaldehyde resin; wherein the base fertilizer is prepared by mixing urea and diammonium dihydrogen phosphate in a mass ratio of 1:1;

[0081] The preparation method of the composite base fertilizer inner layer material comprises the following steps: according to the composite base fertilizer formula, weighing the base fertilizer, the slow-release carrier, and the urea-formaldehyde resin, mixing the slow-release carrier and the base fertilizer and adding them into the reactor, then adding cyclohexane, stirring for a certain period of time, adding the paste urea-formaldehyde resin adhesive into the mixture, pouring it into a grinder again, mixing it, drying it, and granulating it with a granulator to obtain the composite base fertilizer inner layer material;

[0082] The preparation method of the sustained-release carrier is as follows: purifying bentonite and sieving it, calcining it at 200°C for 2h, and then cooling it to room temperature to prepare activated bentonite for use; preparing a chitosan aqueous solution with a concentration of 1%, then transferring acetic acid to a beaker, stirring to completely dissolve the chitosan, preparing a chitosan solution for use; mixing the prepared chitosan solution and the activated bentonite evenly to prepare a mixed solution, wherein the mass ratio of chitosan to activated bentonite in the mixed solution is 1:1, stirring and reacting for 2h, washing the flocs produced after the reaction with deionized water until neutral, and drying at 60°C for 12h to prepare a sustained-release carrier;

[0083] The preparation method of the water retaining agent comprises the following steps:

[0084] Step (1): Weigh starch and dissolve it in water to prepare a starch solution for later use;

[0085] Step (2): weighing acrylic acid into a reactor, adding deionized water, slowly adding sodium hydroxide solution in an ice water bath, and then adding chitosan, stirring to dissolve, preparing a mixed solution A for standby use; wherein the ratio of the added amounts of acrylic acid, starch and chitosan is 1:0.06:0.03;

[0086] Step (3): Mixing the mixed solution A with the starch solution, passing nitrogen, heating to 40° C., adding an initiator, ammonium persulfate, and a cross-linking agent, N,N-dimethylacrylamide, irradiating with ultraviolet light, stirring until the solution becomes viscous, stopping stirring, and continuing to react for 2 hours under nitrogen protection, and after cyclically washing the reaction product, drying it in an oven at 50° C. for 6 hours to prepare a water retaining agent;

[0087] The mass ratio of the added amount of the initiator to the total added amount of acrylic acid, starch and chitosan is 0.1:100, and the mass ratio of the added amount of the cross-linking agent to the total added amount of acrylic acid, starch and chitosan is 0.05:100.

[0088] The process of cyclic washing is as follows: firstly, the reaction product is rinsed with deionized water, then immersed in 1% acetic acid solution for 10 seconds, and the above operation is repeated 3 times.

[0089] This embodiment also provides a method for preparing a slow-release basal fertilizer, which comprises the following steps:

[0090] S1: According to the formula of slow-release base fertilizer, weigh the inner layer material of composite base fertilizer, slow-release carrier, water retaining agent, and prepare 1-5% chitosan solution;

[0091] S2: using acetic acid vapor to wrap the chitosan solution around the outside of the inner layer of the composite base fertilizer to form a coating material 1;

[0092] S3: coating the sustained-release carrier on the outside of the coating material 1 by passing water vapor to form the coating material 2;

[0093] S4: The water retaining agent is coated on the outside of the coating material 2 by passing water vapor to prepare a slow-release base fertilizer.

[0094] Example 3

[0095] The present embodiment provides a slow-release base fertilizer, comprising a composite base fertilizer inner layer, an intermediate slow-release layer and a water-retaining outer layer, which are sequentially arranged from the inside to the outside. The material of the composite base fertilizer inner layer is a composite base fertilizer inner layer material, the material of the intermediate slow-release layer is a slow-release carrier, the material of the water-retaining outer layer is a water-retaining agent, and a chitosan connecting layer is further arranged between the intermediate slow-release layer and the composite base fertilizer inner layer. The mass ratio of the composite base fertilizer inner layer, the chitosan connecting layer, the intermediate slow-release layer and the water-retaining outer layer is 1:0.1:3:1.

[0096] The composite base fertilizer inner layer material includes the following raw materials in terms of weight: 10 parts of base fertilizer, 40 parts of slow-release carrier, and 4 parts of urea-formaldehyde resin; wherein the base fertilizer is prepared by mixing urea and diammonium dihydrogen phosphate in a mass ratio of 1:1;

[0097] The preparation method of the composite base fertilizer inner layer material comprises the following steps: according to the composite base fertilizer formula, weighing the base fertilizer, the slow-release carrier, and the urea-formaldehyde resin, mixing the slow-release carrier and the base fertilizer and adding them into the reactor, then adding cyclohexane, stirring for a certain period of time, adding the paste urea-formaldehyde resin adhesive into the mixture, pouring it into a grinder again, mixing it, drying it, and granulating it with a granulator to obtain the composite base fertilizer inner layer material;

[0098] The preparation method of the sustained-release carrier is as follows: purifying bentonite and sieving it, calcining it at 400°C for 2h, and then cooling it to room temperature to prepare activated bentonite for use; preparing a chitosan aqueous solution with a concentration of 5%, then transferring acetic acid to a beaker, stirring to completely dissolve the chitosan, preparing a chitosan solution for use; mixing the prepared chitosan solution and the activated bentonite evenly to prepare a mixed solution, wherein the mass ratio of chitosan to activated bentonite in the mixed solution is 1:10, stirring and reacting for 4h, washing the flocs produced after the reaction with deionized water until neutral, and drying at 80°C for 12h to prepare a sustained-release carrier;

[0099] The preparation method of the water retaining agent comprises the following steps:

[0100] Step (1): Weigh starch and dissolve it in water to prepare a starch solution for later use;

[0101] Step (2): Weigh acrylic acid into a reactor, add deionized water, slowly add sodium hydroxide solution in an ice water bath, then add chitosan, stir to dissolve, and prepare a mixed solution A for standby use; wherein the ratio of the added amounts of acrylic acid, starch and chitosan is 1:0.20:0.01;

[0102] Step (3): Mixing the mixed solution A with the starch solution, passing nitrogen, heating to 60° C., adding an initiator, ammonium persulfate, and a cross-linking agent, N,N-dimethylacrylamide, irradiating with ultraviolet light, stirring until the solution becomes viscous, stopping stirring, and continuing to react for 6 hours under nitrogen protection, washing the reaction product in a cycle, and drying it in an oven at 90° C. for 3 hours to prepare a water retaining agent;

[0103] The mass ratio of the added amount of the initiator to the total added amount of acrylic acid, starch and chitosan is 1.0:100, and the mass ratio of the added amount of the cross-linking agent to the total added amount of acrylic acid, starch and chitosan is 0.01:100.

[0104] The process of cyclic washing is as follows: firstly, the reaction product is rinsed with deionized water, then immersed in 1% acetic acid solution for 10 seconds, and the above operation is repeated 5 times.

[0105] This embodiment also provides a method for preparing a slow-release basal fertilizer, which comprises the following steps:

[0106] S1: According to the formula of slow-release base fertilizer, weigh the inner layer material of composite base fertilizer, slow-release carrier, water retaining agent, and prepare 1-5% chitosan solution;

[0107] S2: using acetic acid vapor to wrap the chitosan solution around the outside of the inner layer of the composite base fertilizer to form a coating material 1;

[0108] S3: coating the sustained-release carrier on the outside of the coating material 1 by passing water vapor to form the coating material 2;

[0109] S4: The water retaining agent is coated on the outside of the coating material 2 by passing water vapor to prepare a slow-release base fertilizer.

[0110] Comparative Example 1

[0111] This comparative example provides a slow-release base fertilizer, which is different from Example 1 in that, in this comparative example, the chitosan connecting layer, the middle slow-release layer, and the water-retaining outer layer are removed, leaving only the inner layer of the composite base fertilizer.

[0112] Comparative Example 2

[0113] This comparative example provides a slow-release basal fertilizer, which is different from Example 1 in that the water-retaining outer layer is removed in this comparative example.

[0114] This comparative example also provides a method for preparing a slow-release basal fertilizer, which is different from that provided in Example 1 in that the preparation method in this comparative example removes step S4.

[0115] Comparative Example 3

[0116] This comparative example provides a base fertilizer, which is different from Example 1 in that, in this comparative example, the base fertilizer is prepared by mixing urea and diammonium dihydrogen phosphate in a mass ratio of 1:1.

[0117] Experimental example

[0118] The performance of the basal fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the relevant test items and test procedures were as follows:

[0119] Test 1: Determination of the slow-release performance of basal fertilizer

[0120] The determination method refers to GB / T 23348-2009, and the experimental results are shown in Table 1;

[0121] The test results are shown in Table 1;

[0122] Table 1

[0123]

[0124] It can be seen from the results in Table 1 that Examples 1-3 are slow-release basal fertilizers prepared by the present invention, and their slow-release effects are all due to the basal fertilizers provided by Comparative Examples 1-2.

[0125] Test 2: Soil water retention capacity determination

[0126] Mix the basal fertilizer and dry soil (below 26 mesh) in a mass ratio of 1:100 and put them into an open container. Slowly add tap water, where the mass ratio of tap water to dry soil is 1:1. Weigh (marked as W1), place at room temperature, and weigh once every 3 days, which is W1. n , observe continuously for 21 days, and the evaporation rate of water in the soil (i.e. W%) is calculated according to the following formula:

[0127] W%=(W1-W n )×100%;

[0128] Table 2

[0129]

[0130] It can be seen from the data in Table 2 that when the basal fertilizers prepared in Examples 1-3 of the present invention are added to the soil, the water evaporation rates are 71.45%, 68.33% and 74.58% respectively, while the basal fertilizers provided in Comparative Examples 1-3 have soil water evaporation rates of more than 85%, namely 90.76%, 86.26% and 95.98% respectively, indicating that the slow-release basal fertilizer provided by the present invention, after being added to the soil, not only has good water absorption capacity, but also has good water retention capacity, can slow down the evaporation of water in the soil, slowly release the stored water, can improve the utilization rate of water resources, and has good application prospects in arid, semi-arid and desert areas;

[0131] In addition, the slow-release fertilizer was applied to the crop (corn) for plant height and root length testing after germination, with no fertilization as a blank control. The results showed that the slow-release basal fertilizer provided in Comparative Examples 1-3 was applied to the crop (corn), and its plant height and root length were higher than those of the blank control group. The slow-release basal fertilizer provided in Examples 1-3 of the present invention was applied to the crop (corn), and its plant height and root length were higher than those of the slow-release basal fertilizer provided in Comparative Examples 1-3; specifically, the slow-release basal fertilizer provided in Comparative Example 3 was applied to the crop (corn), and its plant height and root length were 1.51 times and 4.26 times those of the blank control group, respectively; the slow-release basal fertilizer provided in Example 1 was applied to the crop (corn), and its plant height and root length were 2.24 times and 1.14 times those of the comparative example 3, respectively.

[0132] The invention provides a slow-release base fertilizer and a preparation method and application thereof. The slow-release base fertilizer can improve crop yield and at the same time play a slow-release role, thereby improving the nutrient utilization rate of the fertilizer. The raw materials of the slow-release base fertilizer are easily available, the production cost can be effectively controlled, and the slow-release base fertilizer can be promoted and used on a large scale.

[0133] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0134] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A slow-release basal fertilizer, characterized in that: It includes a composite base fertilizer inner layer, a middle slow-release layer and a water-retaining outer layer which are sequentially arranged from the inside to the outside; The material of the inner layer of the composite base fertilizer is the inner layer material of the composite base fertilizer, the material of the middle slow-release layer is a slow-release carrier, and the material of the water-retaining outer layer is a water-retaining agent; A chitosan connecting layer is also provided between the intermediate slow-release layer and the inner layer of the composite base fertilizer; The composite base fertilizer inner layer material comprises the following raw materials in parts by weight: 10 parts of base fertilizer, 10-40 parts of slow-release carrier, and 4-10 parts of urea-formaldehyde resin; The mass ratio of the composite base fertilizer inner layer, the chitosan connecting layer, the middle slow-release layer and the water-retaining outer layer is 1:(0.1-0.2):(1-3):(1-4).

2. A slow-release basal fertilizer according to claim 1, characterized in that: The base fertilizer is any one or more of urea, ammonium dihydrogen phosphate, and potassium dihydrogen phosphate mixed in any proportion.

3. A slow-release basal fertilizer according to claim 1, characterized in that: The preparation method of the composite base fertilizer inner layer material comprises the following steps: according to the composite base fertilizer formula, weighing the base fertilizer, slow-release carrier and urea-formaldehyde resin, mixing the slow-release carrier and the base fertilizer and adding them into a reactor, then adding cyclohexane, stirring for a certain period of time, adding a paste urea-formaldehyde resin adhesive into the mixture, pouring it into a pulverizer again and mixing it, drying it, and granulating it with a granulator to obtain the composite base fertilizer inner layer material.

4. A slow-release basal fertilizer according to claim 1, characterized in that: The preparation method of the sustained-release carrier is as follows: Step 1: purify the bentonite, sieve it, place it at 200-400°C for 2h, and then cool it to room temperature to prepare activated bentonite for later use; Step 2: Prepare a chitosan aqueous solution with a concentration of 1-5%, then pipette acetic acid into a beaker, stir to completely dissolve the chitosan, and prepare a chitosan solution for later use; Step 3: Evenly mix the prepared chitosan solution and activated bentonite to prepare a mixed solution, wherein the mass ratio of chitosan to activated bentonite in the mixed solution is 1:(1-10), and the mixture is stirred and reacted for 2-4 hours, and the floccules produced after the reaction are washed with deionized water until neutral, and dried at 60-80°C for 12 hours to prepare a sustained-release carrier.

5. A slow-release basal fertilizer according to claim 1, characterized in that: The preparation method of the water-retaining agent comprises the following steps: Step (1): Weigh starch and dissolve it in water to prepare a starch solution for later use; Step (2): weigh acrylic acid into a reactor, add deionized water, slowly add sodium hydroxide solution in an ice water bath, then add chitosan, stir to dissolve, prepare a mixed solution A, and set aside; Step (3): Mix the mixed solution A with the starch solution, pass nitrogen, heat to 40-60°C, add an initiator and a cross-linking agent, irradiate with ultraviolet light, stir until the solution becomes viscous, stop stirring, and continue to react for 2-6 hours under nitrogen protection. After the reaction product is circulated and washed, it is dried in an oven at 50-90°C for 3-6 hours to prepare a water retaining agent.

6. A slow-release basal fertilizer according to claim 5, characterized in that: The initiator is ammonium persulfate, and the cross-linking agent is N,N-dimethylacrylamide.

7. A slow-release basal fertilizer according to claim 5, characterized in that: The ratio of the added amounts of acrylic acid, starch and chitosan is 1:(0.06-0.20):(0.01-0.03); The mass ratio of the added amount of the initiator to the total added amount of acrylic acid, starch and chitosan is (0.1-1.0):100, and the mass ratio of the added amount of the crosslinking agent to the total added amount of acrylic acid, starch and chitosan is (0.01-0.05):

100.

8. A slow-release basal fertilizer according to claim 5, characterized in that: The process of the cyclic washing is: firstly, the reaction product is rinsed with deionized water, then immersed in 1% acetic acid solution for 10 seconds, and the above operation is repeated 3-5 times.

9. A method for preparing the slow-release basal fertilizer according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1: According to the formula of slow-release base fertilizer, weigh the inner layer material of composite base fertilizer, slow-release carrier, water retaining agent, and prepare 1-5% chitosan solution; S2: using acetic acid vapor to wrap the chitosan solution around the outside of the inner layer of the composite base fertilizer to form a coating material 1; S3: coating the sustained-release carrier on the outside of the coating material 1 by passing water vapor to form the coating material 2; S4: The water retaining agent is coated on the outside of the coating material 2 by passing water vapor to prepare a slow-release base fertilizer.

10. Use of the slow-release base fertilizer according to any one of claims 1 to 8 in agricultural planting.

Images