Straw compound particles and preparation method thereof

Abstract

The invention discloses a straw compound particle and a preparation method thereof, and relates to the technical field of agriculture, the straw compound particle comprises an organic fertilizer core and a straw layer; the organic fertilizer core is prepared by fermenting straws; the straw layer is prepared from water-absorbent resin, straw powder, carboxymethyl cellulose and plastic starch; the fertilizer can be kept complete in manufacturing, transportation, storage, application and scattering and soil environment, is not easy to pulverize, burst or crack, continuously provides water, nutrients and oxygen, promotes root growth and soil microbial activity, uses a large amount of straws in a core and a shell, realizes high-valued utilization of wastes, reduces fertilizer leaching pollution and water resource waste, and has a wide application prospect. The fertilizer can be used in various environments, and solves the problems of too fast nutrient release, easy leaching loss or volatilization, low utilization rate, poor water retention capacity and frequent irrigation.

Description

Technical Field

[0001] The present invention relates to the technical field of agriculture, and in particular to straw compound particles and a preparation method thereof. Background Art

[0002] Straw is the part of mature crops left after grains are harvested. It contains organic matter, nitrogen, phosphorus, potassium, calcium and other trace elements, and is a renewable agricultural by-product. In terms of utilization, the government emphasizes the "five-material" utilization of straw resources, namely fertilizer, fuel, raw material, feed and base material. Its utilization can be summarized as fertilizer, energy, feed, raw material and base material. Straw is mixed with other organic ingredients or directly used as organic fertilizer to return to the field to restore soil fertility. The use of straw as fertilizer is not limited to returning "single straw" to the field. In practice, straw is often mixed with other organic ingredients to improve the effect of returning to the field or solve the problems of returning straw alone. In the existing technology, returning straw to the field in an environment with huge temperature and humidity changes can easily lead to problems such as delayed or explosive straw release, poor water retention capacity, and excessive nutrient release. Summary of the Invention

[0003] The embodiments of the present application provide a straw compound particle and a preparation method thereof, thereby solving the problem of uneven straw release under abnormal conditions in the prior art, achieving a more uniform straw release rate and higher resistance to abnormal conditions.

[0004] The embodiment of the present application provides a straw compound particle, comprising an organic fertilizer core and a straw layer; The core of the organic fertilizer is made from fermented straw; the straw layer is made from water-absorbing resin, straw powder, carboxymethyl cellulose and plastic starch.

[0005] Furthermore, the straw layer is layered using a sedimentation tank and is made by adsorption from bottom to top through the organic fertilizer core.

[0006] The preparation method of the above-mentioned straw composite particles and the preparation method of the organic fertilizer core are as follows: corn straw is crushed to 3-5 cm, 3% EM bacteria and 1% urea are added, and the humidity is adjusted to 60% with water, and piled into long strips 1.5 meters high and 1.5 meters wide. The temperature is controlled at 50-65°C and fermented for 7 days, and then the temperature is no longer controlled until the temperature drops to room temperature, indicating that the fermentation is complete; granulation is obtained after fermentation, and the particle size is 3 mm.

[0007] Furthermore, the straw layer is prepared as follows: S1, plastic starch is mixed into fine particle water-absorbing resin at a mass ratio of 20% and mixed evenly, and plastic starch is mixed into coarse particle water-absorbing resin at a mass ratio of 15% and mixed evenly; Coarse and fine particles of water-absorbing resin were mixed in a mass ratio of 70:30; a 3% carboxymethyl cellulose aqueous solution was added at a solid-liquid ratio of 1:5; and stirred for 20 minutes to prepare a suspension; S2. Pour the suspension into a sedimentation tank and let it settle for 120 minutes to separate into layers. The upper layer is enriched with fine particles of water-absorbing resin, while the lower layer is enriched with coarse particles of water-absorbing resin. S3. Lay a low-porosity straw layer at the bottom of the sedimentation tank; a transition layer in the middle; and a high-porosity straw layer on the top; The laying process is as follows: 30-60 mesh straw powder is taken, immersed in a 5% carboxymethyl cellulose solution, and ultrasonically treated at 5°C for 20 minutes to form a sticky hydroxyl colloid layer on the straw surface. The straw is then cold-pressed separately. The straw in the low-porosity straw layer is cold-pressed at 10MPa, the straw in the middle layer is cold-pressed at 5MPa, and the straw in the high-porosity straw layer is naturally stacked. S4: The compound fertilizer core is placed at the bottom center of the sedimentation tank; adsorption is sequentially performed from bottom to top, and then an inner anti-expansion layer, a middle layer, and an outer anti-shrinkage layer are sequentially formed to obtain adsorption particles; The adsorbed particles were transferred to a drying device and cured at 70°C for 30 minutes to obtain straw composite particles.

[0008] Furthermore, the particle size of the coarse water-absorbing resin is 50-100 μm, and the particle size of the fine water-absorbing resin is 1-10 μm.

[0009] Furthermore, the porosity of the straw in the porous straw layer is 30%, the porosity of the straw in the transition layer is 45%, and the porosity of the straw in the high-porosity straw layer is 60%.

[0010] Furthermore, the straw laying process is as follows: 30-60 mesh straw powder is taken, immersed in 5% carboxymethyl cellulose solution, ultrasonically treated at 5°C for 20 min, and a sticky hydroxyl colloid layer is generated on the surface of the straw, and then polar cold pressing is performed to form the powder.

[0011] Furthermore, the straw in the low-porosity straw layer is cold-pressed at 10 MPa, the straw in the middle layer is cold-pressed at 5 MPa, and the straw in the high-porosity straw layer can be naturally stacked.

[0012] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: By using plastic starch and water-absorbing resin, the straw compound particles remain intact during manufacturing, transportation, storage, spreading and soil environment, and are not easily pulverized, burst or cracked. They continuously provide water, nutrients and oxygen, promote root growth and soil microbial activity, and use a large amount of straw in both the core and the shell, achieving high-value utilization of waste, reducing fertilizer leaching pollution and water resource waste. They can be used in various environments and solve the problems of rapid nutrient release, easy leaching or volatilization, low utilization rate, poor water retention capacity, and frequent irrigation. DETAILED DESCRIPTION

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains; the terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more of the associated listed items.

[0014] Example 1: A straw compound particle comprising an organic fertilizer core and a straw layer; The core of the organic fertilizer is made from fermented corn stalks. Specifically, corn stalks are crushed to 3-5cm, 3% EM bacteria and 1% urea are added, and the humidity is adjusted to 60% with water. The stalks are then piled into strips 1.5 meters high and 1.5 meters wide. The temperature is controlled at 50-65°C and fermented for 7 days. The temperature is then no longer controlled until the temperature drops to room temperature, which means the fermentation is complete (approximately 30-45 days). After fermentation, the granules are granulated to obtain the product, with a particle size of 3mm. The straw layer is made of absorbent resin, straw powder, carboxymethyl cellulose and plastic starch. It is layered in a sedimentation tank and adsorbed from the bottom up by the organic fertilizer core, or coated into a shell by itself. The specific steps are as follows: S1. Plastic starch (thermoplastic starch) is mixed into fine-grained water-absorbing resin at a mass ratio of 20% and mixed evenly. Plastic starch is mixed into coarse-grained water-absorbing resin at a mass ratio of 15% and mixed evenly. Coarse and fine particles of water-absorbent resin (SAP) were mixed in a mass ratio of 70:30; a 3% carboxymethyl cellulose (CMC) aqueous solution was added at a solid-liquid ratio of 1:5; and the mixture was stirred (200 rpm) for 20 minutes to form a suspension. The particle size of the coarse particles of water-absorbent resin was 50-100 μm, and the particle size of the fine particles of water-absorbent resin was 1-10 μm. S2. Pour the suspension into a sedimentation tank (length-to-diameter ratio 5:1); let it settle for 120 minutes (temperature 25±2°C) to separate into layers; the upper layer is enriched with fine SAP particles (sedimentation rate 0.01 mm / s); the lower layer is enriched with coarse SAP particles (sedimentation rate 0.1 mm / s).

[0015] S3: Lay a low-porosity straw layer (30% porosity, 1mm thickness) at the bottom of the sedimentation tank; a transition layer (45% porosity, 1mm thickness) in the middle; and a high-porosity straw layer (60% porosity, 1mm thickness) on the top. The laying process is as follows: take 30-60 mesh straw powder, immerse it in 5% carboxymethyl cellulose solution (solid-liquid ratio 1:8), and ultrasonically treat it at 5°C for 20 minutes to form a sticky hydroxyl colloid layer on the straw surface. Then, cold press the straw in the low-porosity straw layer using 10MPa cold press, the straw in the middle layer using 5MPa cold press, and the straw in the high-porosity straw layer can be naturally stacked. S4: The compound fertilizer core is placed at the bottom center of the sedimentation tank; adsorption is sequentially performed from bottom to top, and then an inner anti-expansion layer, a middle layer, and an outer anti-shrinkage layer are sequentially formed to obtain adsorption particles; The adsorbed particles were transferred to a drying device and cured at 70°C for 30 minutes to obtain straw composite particles.

[0016] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: The core function of plastic starch (thermoplastic starch) is to act as a binder. It is evenly blended into coarse and fine SAP particles. During the subsequent drying and curing process, the thermoplastic starch melts or softens, flowing and wrapping the SAP particles and straw powder. The molten TPS forms bonding bridges and a continuous bonding network between SAP particles, between SAP and straw powder, and within the straw powder itself. Through its bonding effect, TPS helps maintain the pore structure of the straw layer formed by cold pressing, preventing it from collapsing during subsequent handling and application. After plasticization, TPS forms an amorphous state with a coiled molecular chain conformation. The molecular chain segments absorb stress through β relaxation (secondary relaxation), which also ensures increased interfacial forces under large environmental changes and protects the integrity of the structure. The cured TPS network firmly bonds the various components of the shell together to form a monolithic structure. Even when SAP absorbs water and swells or loses water and shrinks, it effectively prevents the shell from disintegrating or flaking, fixing the porous skeleton formed by the straw powder, and maintaining the designed low-, medium-, and high-porosity structures and fulfilling their functions.

[0017] The core function of water-absorbing resin (SAP) is to absorb and lock a large amount of water. It slowly releases or absorbs water according to the ambient humidity and soil moisture conditions. The absorbed water dissolves the nutrients released by the core of the organic fertilizer. SAP slowly releases water and nutrients at the same time, achieving slow release of water and fertilizer, improving utilization efficiency, reducing leaching, maintaining the humidity of the soil around the particles, and creating more favorable conditions for microbial activity and root growth. The significant difference between coarse-grained SAP (50-100μm) with fast sedimentation (0.1mm / s) and fine-grained SAP (1-10μm) with slow sedimentation (0.01mm / s) is utilized to form a natural gradient distribution of particle size from coarse to fine from bottom to top. Coarse-grained SAP has a large water absorption capacity, but a relatively slow swelling rate. The volume expansion after moisture absorption is relatively small. It is located outside the core, absorbing a large amount of water released by the core, buffering its volume expansion stress, and effectively preventing the core from excessive swelling and causing the particle shell to rupture. Fine particles of SAP have a large specific surface area and a fast swelling rate, but the water absorption of a single particle is relatively small. They are located in the outermost layer and shrink faster and more obviously when the environment is dry. The outer layer enriched with fine particles shrinks rapidly to form a relatively dense "shell" to prevent the internal moisture from dissipating too quickly, maintain the internal humidity of the particles, and prevent the particles as a whole from shrinking and cracking violently due to rapid water loss. The outer fine particles respond quickly to water absorption and swelling while allowing water to penetrate inward; the inner coarse particles absorb most of the water and swell slowly to avoid a sudden increase in internal pressure; when retaining water: the anti-shrinkage layer formed on the outer layer reduces water evaporation loss; when releasing water / drying: the outer fine particles quickly lose water and shrink to form a protective dense layer, which slows down the release rate of internal water and achieves a more lasting sustained-release effect; it avoids the problem that the outer shell of a single coarse particle swells slowly, has good anti-swelling properties, but has slow water loss and shrinkage, and poor crack resistance; it also avoids the problem that the outer shell of a single fine particle swells quickly, is easy to break, and has fast water loss and shrinkage, resulting in poor water retention.

[0018] The laying of straw layers ensures the continuous mineralization and decomposition of the core organic fertilizer and the activity of microorganisms, avoiding the production of harmful substances in the anaerobic environment. The high porosity of the outer layer is conducive to rapid water absorption, and the low porosity of the inner layer reduces ineffective leakage, thereby enhancing the overall water retention. The gradient pore structure combined with CMC bonding and cold pressing gives the outer shell good overall strength.

[0019] The organic fertilizer core provides basic nutrients, while the SAP-TPS-straw shell absorbs, retains, and slowly releases water, regulating the rate of nutrient dissolution, achieving integrated long-term slow-release of water and fertilizer. The nutrient release of the core is regulated by the moisture in the shell, and the water retention capacity of the shell depends on the core and soil to provide water, preventing it from being washed away in the rainy season and retaining moisture in the dry season. The inner layer (coarse SAP) is resistant to expansion, the outer layer (fine SAP) is resistant to shrinkage, TPS is bonded and solidified, and the straw skeleton supports the pellets, all of which ensure the structural integrity of the pellets under dry-wet cycles, preventing them from bursting or cracking. The outer high-porous straw layer absorbs water quickly, the SAP gradient layer efficiently holds water, and the straw porosity gradient layer optimizes the water transfer path and rate within the particles and to the soil, achieving efficient water absorption, strong water retention, and on-demand water release (for plants and microorganisms). The gaps between the outer high-porous straw layer and the SAP particles ensure oxygen supply, while the inner SAP and straw layers lock in moisture, creating an ideal moist and breathable microenvironment for the continuous mineralization and decomposition of the organic fertilizer core and the activity of beneficial microorganisms.

[0020] The straw compound pellets remain intact during manufacturing, transportation, storage, spreading and soil environment, are not easily powdered, burst or cracked, and continuously provide water, nutrients and oxygen, promoting root growth and soil microbial activity. A large amount of straw is used in both the core and the shell, achieving high-value utilization of waste, reducing fertilizer leaching pollution and water resource waste, and can be used in various environments, solving the problems of rapid nutrient release, easy leaching or volatilization, low utilization rate, poor water retention capacity, and the need for frequent irrigation.

[0021] The functions of the straw compound pellets were verified and grouped into experiments, including the CK group (blank soil without fertilizer), the CF group (using 45% ordinary compound fertilizer with N:P:K=15:15:15), the OF group (pure organic fertilizer core pellets without shell), the TPS group (complete pellets with plastic starch removed), the SAP- group (complete pellets with all SAP removed), the SAP-C group (only coarse SAP for the shell), the SAP-F group (only fine SAP for the shell), the SAP-Mix group (homogeneous shell with coarse and fine SAP mixed but not stratified), and the EXP group (complete straw compound pellets). The experiment included testing the content of soil organic matter, alkaline-hydrolyzable nitrogen, available phosphorus, and available potassium (conventional chemical methods, referencing NY / T 1121.6-2006 Soil Testing Part 6: Determination of Soil Organic Matter, LY / T 1228-2015 Determination of Forest Soil Nitrogen, NY / T 1121.7-2014 Determination of Soil Available Phosphorus, and NY / T 889-2004 Determination of Soil Available and Slowly Available Potassium), the residual mass of grain shells (residue recovery and weighing method), the number of nitrogen-fixing bacteria and cellulolytic bacteria (selective culture medium plate count method), the particle breakage rate after dry-wet cycles (screening method, percentage of particles >2 mm), and changes in soil moisture during drought (TDR soil moisture meter). The experimental procedure was as follows: sandy loam soil, 10 kg of soil per pot, corn (3 plants per pot), nitrogen fertilizer applied at a rate of 150 kg N / ha, buried to a depth of 5 cm, and irrigated quantitatively (twice a week, 100 mL each time). A simulated drought period (no water for 14 days starting from the fourth week) was simulated by soaking for 12 hours on the 50th day and then drying at 60°C for 12 hours, simulating a dry-wet cycle, which was repeated five times. The results are shown in Tables 1, 2, and 3.

[0022] Table 1 Soil nutrients and straw degradation rate (mean) at 90 days

[0023] Table 2 Microbial count and particle stability at 60 days and particle breakage rate at 55 days after dry-wet cycle

[0024] Table 3 Changes in soil moisture during the drought period (14 days after water withdrawal)

[0025] Example 2: This example provides a method for using the straw composite particles in Example 1, specifically: On a non-rainy day 15 days before spring sowing, use a deep trough fertilizer spreader (trough depth ≥ 15 cm) at a rate of 200 kg / mu for sandy soil, 150 kg / mu for loam, and 100 kg / mu for clay. Adjust the feed port pressure to ≤ 0.1 MPa and the conveyor belt speed to ≤ 2 m / s for fertilizer return. The row spacing is 40 cm and the furrow width is 20 cm. The granule distribution method is: bottom layer: 60% of the total amount of granules (placed at a depth of 10-15 cm), middle layer: 40% of the total amount of granules (placed at a depth of 5-10 cm). Immediately after application, drip irrigation / micro-spraying is carried out for 20 m 3 / mu.

[0026] By returning the fertilizer to the fields, the release of its fertility can be delayed until the crop growth period, reducing the number of topdressing times. By layered deep burial protection and utilizing the gradient structure of the particles, the microorganisms and the slow-release function of the particles can be activated simultaneously to synergistically enhance their effectiveness.

[0027] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A straw composite pellet, characterized in that: Includes organic fertilizer core and straw layer; The core of the organic fertilizer is made from fermented straw; the straw layer is made from water-absorbing resin, straw powder, carboxymethyl cellulose and plastic starch.

2. The straw composite particle according to claim 1, characterized in that: The straw layer is layered using a sedimentation tank and is made by adsorption from bottom to top through the organic fertilizer core.

3. The method for preparing the straw composite particles according to any one of claims 1 to 2, characterized in that: The preparation method of the organic fertilizer core is as follows: crush the corn straw into 3-5cm, add 3% EM bacteria and 1% urea, and adjust the humidity to 60% with water, pile it into a long strip 1.5 meters high and 1.5 meters wide, control the temperature at 50-65℃, ferment for 7 days, and then no longer control the temperature until the temperature drops to room temperature, which means the fermentation is complete; granulate it after fermentation, and the particle size is 3mm.

4. The method for preparing straw composite particles according to claim 3, wherein: The preparation method of the straw layer is as follows: S1, plastic starch is mixed into fine particle water-absorbing resin at a mass ratio of 20% and mixed evenly, and plastic starch is mixed into coarse particle water-absorbing resin at a mass ratio of 15% and mixed evenly; Coarse and fine particles of water-absorbing resin were mixed in a mass ratio of 70:30; a 3% carboxymethyl cellulose aqueous solution was added at a solid-liquid ratio of 1:5; and stirred for 20 minutes to prepare a suspension; S2, the suspension is injected into the sedimentation tank; Let it settle for 120 minutes to allow it to separate into layers; Upper layer: enriched with fine particle water-absorbing resin; lower layer: enriched with coarse particle water-absorbing resin; S3. Lay a low-porosity straw layer at the bottom of the sedimentation tank; a transition layer in the middle; and a high-porosity straw layer on the top; The laying process is as follows: 30-60 mesh straw powder is taken, immersed in a 5% carboxymethyl cellulose solution, and ultrasonically treated at 5°C for 20 minutes to form a sticky hydroxyl colloid layer on the straw surface. The straw is then cold-pressed separately. The straw in the low-porosity straw layer is cold-pressed at 10MPa, the straw in the middle layer is cold-pressed at 5MPa, and the straw in the high-porosity straw layer is naturally stacked. S4: The compound fertilizer core is placed at the bottom center of the sedimentation tank; adsorption is sequentially performed from bottom to top, and then an inner anti-expansion layer, a middle layer, and an outer anti-shrinkage layer are sequentially formed to obtain adsorption particles; The adsorbed particles were transferred to a drying device and cured at 70°C for 30 minutes to obtain straw composite particles.

5. The method for preparing straw composite particles according to claim 4, wherein: The particle size of the coarse-grained water-absorbing resin is 50-100 μm, and the particle size of the fine-grained water-absorbing resin is 1-10 μm.

6. The method for preparing straw composite particles according to claim 4, wherein: The porosity of the straw in the porous straw layer is 30%, the porosity of the straw in the transition layer is 45%, and the porosity of the straw in the high-porosity straw layer is 60%.

7. The method for preparing straw composite particles according to claim 4, wherein: The straw laying process is as follows: take 30-60 mesh straw powder, immerse it in 5% carboxymethyl cellulose solution, ultrasonically treat it at 5℃ for 20 minutes, generate a sticky hydroxyl colloid layer on the straw surface, and then polar cold press it into shape.

8. The method for preparing straw composite particles according to claim 7, wherein: The straw in the low-porosity straw layer is cold-pressed at 10 MPa, the straw in the middle layer is cold-pressed at 5 MPa, and the straw in the high-porosity straw layer can be naturally stacked.

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