A method for strengthening straw decomposition by biochar associated free radicals

Abstract

The present application relates to a kind of biochar associated radical reinforced straw decomposition operation method, belong to agricultural technology field, including the following steps: 1) straw field pretreatment, field straw is crushed to length 2-5 cm;2) high PFRs enrichment biochar preparation and selection, using 400-600 ℃ oxygen-limited pyrolysis process preparation biochar, constant temperature keeps, natural cooling to room temperature;Selection of high PFRs biochar with high surface persistent free radical (PFRs) abundance, developed pore structure, ash content 10%-25%, standby;3) biochar quantitative distribution mixes evenly, weigh high PFRs biochar, evenly spread on the surface of crushed straw;4) field moisture and ventilation control, control soil moisture content to 60%-80% of field water holding capacity, then use soil air blaster in farmland 3 meters interval carries out 50-60cm depth soil ventilation;5) stirring covering soil abiotic decomposition microenvironment, using stirring operation, straw-biochar mixture is turned into 0-20 cm farmland plough layer, and moderate covering soil conservation.

Description

Technical Field

[0001] This invention belongs to the field of agricultural technology, specifically relating to a method for enhancing straw decomposition by biochar-associated free radicals. Background Technology

[0002] Crop straw is rich in lignin, cellulose, hemicellulose and other lignocellulose components. Among them, lignin has a dense structure and strong chemical stability, making it a stubborn and difficult-to-degrade component in the straw decomposition process. Under natural conditions, it relies on native soil microorganisms for a long degradation cycle and slow decomposition rate, which can easily lead to straw retention in the field, affect the sowing and emergence of the next crop, and also easily breed pests and diseases.

[0003] Existing straw return technologies mostly rely on microbial agents, composting agents, chemical conditioners, or deep plowing, all of which are mainly based on biodegradation. They are greatly limited by soil temperature, soil moisture, and microbial community activity, and the decomposition effect is extremely poor in low-temperature seasons and in poor farmland. Moreover, existing technologies cannot break down the molecular structure and cross-linking barriers of stubborn components such as lignin at the non-biological level in advance. The early disintegration of straw is slow and the stubborn components are not completely broken down, which restricts the improvement of straw return quality and efficiency.

[0004] During the oxygen-limited pyrolysis process, biochar accumulates persistent free radicals (PFRs) on its surface and in its pore structure. These free radicals are highly stable, have a long retention period, and possess continuous electron transfer and catalytic reaction capabilities. Current research has not yet systematically applied the mechanism of biochar PFRs catalyzing the generation of reactive oxygen hydroxyl radicals to straw return operations in the field. There is a lack of a standardized field operation process characterized by PFRs as the core and non-biological initiation combined with the oxidative breakdown of stubborn components. Summary of the Invention

[0005] This invention relates to a method for enhancing straw decomposition by biochar-associated free radicals. It utilizes persistent free radicals (PFRs) on the surface of biochar to induce the generation of reactive oxygen hydroxyl radicals, which non-biologically drive and accelerate straw decomposition, thereby achieving a field operation method for the directional oxidative crushing of stubborn components in straw.

[0006] The technical solution of this invention is:

[0007] A method for enhancing straw decomposition by incorporating free radicals in biochar, the key points of which include the following steps:

[0008] 1) Field pretreatment of straw

[0009] After the crops are harvested, the straw in the field is crushed to a length of 2-5 cm, and after removing moldy straw and impurities, it is spread evenly on the surface of the farmland.

[0010] 2) Preparation and screening of biochar enriched with high PFRs

[0011] Biochar was prepared using agricultural and forestry waste as raw material through an oxygen-limited pyrolysis process at 400-600 ℃. The temperature was maintained for 2-4 hours, and the biochar was naturally cooled to room temperature. Biochar with high PFRs, high abundance of persistent surface free radicals (PFRs), well-developed pore structure, and ash content of 10%-25% was screened for later use.

[0012] 3) Apply biochar in a measured amount and mix thoroughly.

[0013] Weigh out 6%-18% of the dry weight of the straw and spread it evenly on the surface of the crushed straw.

[0014] 4) Field water and ventilation regulation

[0015] Adjust the soil moisture content to 60%-80% of field capacity, and then use a soil aerator to aerate the soil to a depth of 50-60cm at 3-meter intervals in the field;

[0016] 5) Mixing the cover soil to create a non-biological decomposition microenvironment

[0017] The straw-biochar mixture is mixed and then turned into the 0-20 cm topsoil layer of the farmland, and then covered with soil to retain moisture.

[0018] In step 1), the straw is crushed using a crusher. The crusher includes a traction machine, a crushing chamber fixed on the traction machine and a crushing blade shaft inside it. An electrostatic generating mechanism is provided on the inner wall of the crushing chamber. The electrostatic generating mechanism includes a set of chemical fiber cloths fixed at one end to the inner wall of the crushing chamber. The chemical fiber cloths are evenly distributed on the inner wall of the crushing chamber.

[0019] The crushing chamber outlet is provided with a discharge channel, the inner wall of the discharge channel is provided with a spiral groove, and an electrostatic generating mechanism is provided on the inner wall of the spiral groove; the discharge channel is inclined, and a transmission mechanism is provided between the traction machine traveling wheel and the discharge channel to make the discharge channel rotate.

[0020] In step 2), the agricultural and forestry waste is any one of corn cobs, rice husks, sawdust, and waste branches; the pyrolysis heating rate is controlled at 5-10 ℃ / min, and the constant temperature pyrolysis holding time is 2-4 h, to obtain functional biochar with an ash content of 10%-25% and high PFR abundance.

[0021] In step 3), the optimal application ratio of biochar is 8%-12% of the dry weight of straw.

[0022] In step 5), the surface straw stubble coverage rate after mixing is controlled to be below 15%.

[0023] The soil aerator includes an air source and an air rod connected thereto. The air rod includes an inner rod and an outer rod. A set of aeration holes are distributed along the length of the inner rod. The outer rod is sleeved on the outer surface of the inner rod and is provided with a connecting hole corresponding to the aeration holes.

[0024] The distance between the air vents is 10cm, and the length of the inner rod is 70cm.

[0025] The mixing operation is carried out by a mixer, which includes a traction machine and a trenching shovel and a mixing unit connected to it. The mixing unit includes a spiral rod with a pointed head, a set of intersecting mixing rods inside the spiral rod, and a rotation drive unit at the tail of the spiral rod.

[0026] The rotary drive unit includes a drive motor and a connected L-shaped rotary support frame. The rotary support frame includes a connected L-shaped support rod and a rotary rod rotatably connected to its horizontal end. The support rod and the rotary rod are driven by a bevel gear mechanism. The uppermost end of the support rod is connected to the drive motor. The stirring unit is fixedly connected to the front end of the rotary rod.

[0027] Beneficial effects

[0028] This invention relies on PFRs on the surface of biochar to catalyze the generation of active oxygen hydroxyl radicals, breaking through the limitations of traditional straw decomposition that depends on microorganisms. It directly initiates and accelerates straw decomposition through a non-biological pathway, overcoming the limitations of insufficient initial microbial activity and is not restricted by low temperature or low microbial activity in barren soil. It can be applied in all seasons.

[0029] The strong oxidizing effect of hydroxyl radicals can precisely achieve the oxidative breakdown of stubborn components such as straw lignin and dense cellulose, breaking molecular bonds and deconstructing cross-linked structures in advance, fundamentally solving the problems of difficult degradation and long decomposition cycle of stubborn components in straw.

[0030] The process is simple and compatible with existing mechanized farmland crushing, spreading, and rotary tillage equipment. It requires no additional composting agents or chemical pesticides, resulting in low cost and easy promotion. The applied biochar offers multiple benefits, including soil carbon sequestration, water and fertilizer retention, and improved soil structure, achieving synergistic gains in straw resource utilization, farmland quality improvement, and carbon sequestration and emission reduction. The simple, mechanized process allows for both soil improvement and carbon sequestration, enabling a single application to simultaneously achieve straw resource utilization and farmland quality enhancement.

[0031] By adopting a coupled mode of non-biological free radical pre-crushing and microbial deep decomposition, the straw decomposition rate is significantly improved, effectively avoiding straw retention in the field and the breeding of pests and diseases, and ensuring the normal sowing and growth of the next crop.

[0032] By simultaneously pulverizing and electrostatically charging the straw, the biochar particles are ensured to fully cover and stably adhere to the straw surface, preventing uneven biochar coverage during operation, reducing separation between biochar and straw, and ensuring the stable function of the biochar. Secondly, during soil aeration and loosening operations, the rotation of the outer rod in this invention, with its connecting hole and the aeration hole of the inner rod creating an opening and closing switch, allows for an aerated environment throughout the soil at all depths, significantly enhancing the scope and effectiveness of the subsequent decomposition process. The design of the screw rod in the mixer, taking into account the lightness of the biochar particles, provides a gentle stirring method that mixes the biochar-laden straw with the topsoil while avoiding the flying of biochar particles when using rotary tillage or other methods. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the pulverizer in this invention.

[0034] Figure 2 This is a schematic diagram of the soil aerator in this invention.

[0035] Figure 3 yes Figure 2 This is a magnified structural diagram of A.

[0036] Figure 4 This is a schematic diagram of the mixer in this invention.

[0037] The attached diagram shows: 1. Crushing chamber; 2. Crushing blade shaft; 3. Chemical fiber cloth; 4. Discharge channel; 5. Spiral groove; 6. Air source; 7. Inner rod; 701. Aeration hole; 8. Outer rod; 801. Connecting hole; 9. Trenching shovel; 10. Spiral rod; 11. Stirring rod; 12. Drive motor; 13. Support rod; 14. Rotating rod; 15. Bevel gear mechanism. Detailed Implementation

[0038] This invention relates to a method for enhancing straw decomposition by biochar-associated free radicals, comprising straw pretreatment in the field, preparation and screening of biochar enriched with high PFRs, quantitative application and mixing of biochar, field moisture and aeration regulation, and stirring of the soil to create a non-biodegradable microenvironment for covering. The straw is any one or more of corn straw, wheat straw, and rice straw; the recalcitrant components include straw lignin, dense cellulose, and cross-linked structures between lignin and cellulose or hemicellulose.

[0039] Persistent free radicals (PFRs) enriched on the surface of biochar serve as stable catalytic active centers, continuously undergoing electron transfer reactions in the soil water-air medium system. Within the catalytic system, oxygen and water molecules directionally generate reactive oxygen species and hydroxyl radicals. Hydroxyl radicals possess extremely strong redox potentials and non-selective oxidation capabilities, enabling abiotic initiation and acceleration of straw decomposition without the participation of microorganisms. They preferentially attack the aromatic ring structure of straw lignin, glycosidic bonds of cellulose, and cross-linking bonds between components, achieving oxidative breakage, molecular chain rupture, and skeletal deconstruction of stubborn components in straw. After the structure of stubborn components is broken, the porosity of straw increases and degradable sites are exposed, significantly improving the attachment, colonization, and metabolic degradation efficiency of native soil microorganisms, forming a coupled mode of abiotic free radical pre-breakage + microbial synergistic deep decomposition.

[0040] The operating steps are as follows:

[0041] 1) Field pretreatment of straw

[0042] After the crops are harvested, the straw in the field is crushed to a length of 2-5 cm, and after removing moldy straw and impurities, it is spread evenly on the surface of the farmland.

[0043] Straw crushing is carried out using a crusher, which includes a traction machine, a crushing chamber 1 fixed to the traction machine, and a crushing blade shaft 2 inside the traction machine. An electrostatic generating mechanism is provided on the inner wall of the crushing chamber 1. The electrostatic generating mechanism includes a set of chemical fiber cloth 3 with one end fixed to the inner wall of the crushing chamber 1. The chemical fiber cloth 3 is evenly distributed on the inner wall of the crushing chamber 1. A discharge channel 4 is provided at the outlet end of the crushing chamber 1. A spiral groove 5 is provided on the inner wall of the discharge channel 4. An electrostatic generating mechanism is provided on the inner wall of the spiral groove 5. The discharge channel 4 is inclined. A transmission mechanism is provided between the traction machine's traveling wheel and the discharge channel 4 to rotate the discharge channel 4. The transmission mechanism is a chain drive unit, so that the rotation speed of the traveling wheel is transmitted to the rotational motion of the discharge channel 4 through the chain drive unit. When the traveling wheel stops, the discharge channel 4 also stops, forming a synchronous follow-up of traveling and discharging. After sufficient friction between the crushing chamber 1 and the chemical fiber cloth 3 in the discharge channel 4, the straw becomes statically charged, preparing it for subsequent biochar covering.

[0044] 2) Preparation and screening of biochar enriched with high PFRs

[0045] Biochar was prepared using agricultural and forestry waste as raw materials, including any one of corn cobs, rice husks, sawdust, and waste branches, through an oxygen-limited pyrolysis process at 400-600 ℃. The pyrolysis heating rate was controlled at 5-10 ℃ / min, and the temperature was maintained for 2-4 h before natural cooling to room temperature. High-PFRs biochar with high abundance of persistent surface free radicals (PFRs), well-developed pore structure, and ash content of 10%-25% was selected for later use.

[0046] 3) Apply biochar in a measured amount and mix thoroughly.

[0047] Weigh out 6%-18% of the dry weight of the straw and spread it evenly on the surface of the crushed straw, ensuring that the high-PFRs biochar particles adhere evenly to and coat the surface and pores of the straw. The optimal application ratio of high-PFRs biochar is 8%-12% of the dry weight of the straw.

[0048] 4) Field water and ventilation regulation

[0049] Soil moisture content was adjusted to 60%-80% of field capacity, followed by soil aerators at 3-meter intervals in the farmland to a depth of 50-60cm to maintain an aerobic microenvironment in the topsoil. This provided a liquid medium for the electron transfer reaction of PFRs in biochar and ensured oxygen supply, promoting the continuous catalytic generation of reactive oxygen species (ROS) and hydroxyl radicals by PFRs. PFRs on the biochar surface underwent electron transfer reactions in the soil water-air medium, catalyzing the directional generation of ROS and hydroxyl radicals from oxygen and water molecules. The strong oxidizing effect of hydroxyl radicals non-selectively broke the molecular bonds of straw, achieving the pre-breakdown of stubborn components through a non-biological pathway.

[0050] The soil aerator includes an air source 6 and an air rod connected to it. The air rod includes an inner rod 7 and an outer rod 8. A set of aeration holes 701 are distributed along the length of the inner rod 7. The outer rod 8 is sleeved on the outer surface of the inner rod 7 and is provided with connecting holes 801 corresponding to the aeration holes 701. The spacing between the aeration holes 701 is 10cm. The inner rod 7 is 70cm long and is provided with 6 aeration holes 701 and corresponding connecting holes 801. When inserted into the soil to a depth of 70cm, the outer rod 8 is rotated, and the aeration holes 701 of the inner rod 7 are aligned with the connecting holes 801 of the outer rod 8, forming a gas discharge channel to uniformly improve the aeration of the soil at a depth of 20-70cm.

[0051] 5) Mixing the cover soil to create a non-biological decomposition microenvironment

[0052] The straw-biochar mixture is incorporated into the 0-20 cm topsoil layer of farmland using a mixing process, followed by appropriate soil covering to retain moisture. After mixing, the surface straw stubble coverage is controlled below 15%. Utilizing a closed, warm, and humid microenvironment, the PFRs on the biochar surface continuously exert a catalytic effect, stably generating hydroxyl radicals. This non-biologically initiates the straw decomposition process, continuously oxidizing and breaking down the stubborn components such as straw lignin and dense cellulose.

[0053] The mixing operation is carried out by a mixer, which includes a traction machine and a trenching shovel 9 connected to it, and a mixing unit. The mixing unit includes a spiral rod 10 with a pointed head, and a set of intersecting mixing rods 11 are arranged inside the spiral rod 10. A rotary drive unit is arranged at the tail of the spiral rod 10. The rotary drive unit includes a drive motor 12 and an L-shaped rotary support frame connected to it. The rotary support frame includes an L-shaped support rod 13 connected to it and a rotating rod 14 rotatably connected to its horizontal end. The support rod 13 and the rotating rod 14 are driven by a bevel gear mechanism 15. The uppermost end of the support rod 13 is connected to the drive motor 12. The mixing unit is fixedly connected to the front end of the rotating rod 14.

[0054] During operation, shallow trenches are first created using the trenching shovel 9 to reduce resistance for the subsequent mixing unit. Then, the auger 10 thoroughly mixes the straw and soil containing biochar within a 0-20cm range. The drive motor 12 transmits power to the bevel gear mechanism 15 after passing through a reducer. The bevel gear mechanism 15 is located inside the rotating support frame. The support rod 13 is rotatably connected to the rotating rod 14. The bevel gear mechanism 15 transmits power to the rotating rod 14, thereby driving the auger 10 in the mixing unit to rotate. The soil and straw containing biochar are spirally mixed. The mixing rod 11 mixes the mixture again as it passes inside the auger 10. Throughout the process, the soil and straw are gently oriented, avoiding the separation of biochar caused by other methods such as rotary tillage.

[0055] After being broken down by hydroxyl radical oxidation, the cross-linking barrier of stubborn components in straw is broken, the tissue structure is loose, and easily degradable carbon sources are exposed. Soil native lignin-degrading bacteria and cellulose-decomposing bacteria quickly colonize and accumulate, and then complete the biological metabolic degradation of the remaining components of straw, achieving rapid and complete decomposition and return of straw to the field.

[0056] Example 1

[0057] A method for enhancing straw decomposition by incorporating free radicals into biochar, comprising the following steps:

[0058] 1) Select wheat straw, crush it to 3 cm in the field, remove moldy impurities, and spread it evenly on the ground surface;

[0059] 2) High PFRs biochar was prepared by heating corn cobs at a rate of 8 ℃ / min under oxygen-limited conditions, heating to 500 ℃ and holding at that temperature for 3 h, and then naturally cooling.

[0060] 3) Apply biochar at 10% of the dry weight of wheat straw, and mechanically harrow the land to mix it evenly so that the biochar fully adheres to the surface of the straw;

[0061] 4) Regulate the soil moisture content to 70% of field capacity to maintain an aerobic environment in the topsoil;

[0062] 5) Rotary tillage turns the mixture into the 0-18 cm tillage layer, covers it with soil to retain moisture, and utilizes the PFRs on the surface of biochar to catalyze the generation of active oxygen hydroxyl radicals, which non-biologically initiate and accelerate the decomposition of straw, completing the oxidative crushing of stubborn components such as lignin and dense cellulose.

[0063] 6) Let it sit naturally, relying on the soil's native microorganisms to complete the subsequent deep decomposition.

[0064] Example 2

[0065] A method for enhancing straw decomposition by incorporating free radicals into biochar, comprising the following steps:

[0066] 1) Select corn stalks, crush them to 4 cm, remove impurities, and spread them in the field;

[0067] 2) High PFRs biochar was prepared by using rice husks as raw material, heating rate of 6 ℃ / min, and oxygen-limited pyrolysis at 450 ℃ for 2.5 h.

[0068] 3) Apply biochar at 12% of the dry weight of straw and mix thoroughly by mechanical stirring;

[0069] 4) Adjust the soil moisture content to 75% of field capacity;

[0070] 5) Deeply plow into the 0-20 cm tillage layer, cover with soil to retain moisture, and rely on PFRs to continuously generate hydroxyl radicals, which non-biologically drive the decomposition of straw and break down stubborn components.

[0071] 6) Microbial synergistic decomposition and return to the field under normal temperature and natural conditions.

[0072] Example 3

[0073] A method for enhancing straw decomposition by incorporating free radicals into biochar, comprising the following steps:

[0074] 1) Crush rice straw to 2.5 cm and spread it evenly in the field;

[0075] 2) Using sawdust as raw material, the PFRs-enriched biochar was prepared by heating at a rate of 10 ℃ / min and holding at 550 ℃ under oxygen-limited pyrolysis for 2 h.

[0076] 3) Apply biochar at 8% of the dry weight of straw and harrow to mix it evenly;

[0077] 4) Adjust the soil moisture content to 65% of field capacity;

[0078] 5) Rotary tillage into the 0-19 cm tillage layer, sealing and retaining moisture, hydroxyl radicals are generated through PFRs catalysis, non-biological initiation of straw decomposition and oxidative crushing of stubborn components;

[0079] 6) Microorganisms naturally colonize and degrade the straw, completing the full return of straw to the field.

[0080] The above embodiments are all based on the technical solution of the present invention. The following comparative examples are comparative experiments that differ from the technical solution of this application:

[0081] Comparative Example 1

[0082] Conventional straw return to the field treatment: The straw is crushed to the same length and directly rotary tilled back into the field. No biochar is added and no free radical regulation is carried out. It relies on the natural decomposition by native microorganisms.

[0083] Comparative Example 2

[0084] Conventional biochar return to the field: ordinary low-PFRs commercial biochar is added, without precise water control, and there is no directional hydroxyl radical generation process. It relies solely on the physical adsorption of biochar and natural degradation by microorganisms.

[0085] Experimental results data

[0086] Under the same field climate, soil texture, and straw application conditions, the following were the results of continuous 90-day decomposition monitoring:

[0087] 1) Decomposition residue rate: The straw decomposition residue rate after 90 days in Examples 1-3 was 18.2%-22.5%; the residue rate in Comparative Example 1 was 41.6%, and the residue rate in Comparative Example 2 was 35.8%.

[0088] 2) Degradation rate of stubborn components: In the examples, the degradation rate of lignin and dense cellulose reached 65.3%-71.8%; in Comparative Example 1, it was 32.5%, and in Comparative Example 2, it was 40.2%.

[0089] 3) Decomposition initiation time: The non-biological approach of this invention can initiate significant decomposition in 3-5 days; conventional microbial treatment requires 12-18 days to enter the rapid decomposition stage;

[0090] 4) Improvement of soil organic matter: The organic matter in the topsoil increased by 8.6% to 11.3% after treatment with this invention, which is significantly better than the two comparative examples.

[0091] Experiments show that this invention, through the catalytic production of hydroxyl radicals by biochar PFRs, non-biologically initiates and accelerates the decomposition of straw and breaks down stubborn components, which can significantly reduce the straw residue rate, improve the degradation efficiency of recalcitrant components, shorten the decomposition initiation cycle, and effectively increase the soil organic matter content. The application effect is significantly better than the existing conventional return-to-field technology.

Claims

1. A method for enhancing straw decomposition by generating free radicals from biochar, characterized in that, Includes the following steps: 1) Field pretreatment of straw After the crops are harvested, the straw in the field is crushed to a length of 2-5 cm, and after removing moldy straw and impurities, it is spread evenly on the surface of the farmland. 2) Preparation and screening of biochar enriched with high PFRs Biochar was prepared using agricultural and forestry waste as raw material through an oxygen-limited pyrolysis process at 400-600 ℃. The temperature was maintained for 2-4 h, and the biochar was naturally cooled to room temperature. High PFRs biochar with high abundance of persistent surface free radicals (PFRs), well-developed pore structure, and ash content of 10%-25% was selected for later use. 3) Apply biochar in a measured amount and mix thoroughly. Weigh out 6%-18% of the dry weight of straw and spread it evenly on the surface of the crushed straw. 4) Field water and ventilation regulation Adjust the soil moisture content to 60%-80% of field capacity, and then use a soil aerator to aerate the soil to a depth of 50-60cm at 3-meter intervals in the field; 5) Mixing the cover soil to create a non-biological decomposition microenvironment The straw-biochar mixture is mixed and then turned into the 0-20 cm topsoil layer of the farmland, and then covered with soil to retain moisture.

2. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 1, characterized in that, In step 1), the straw is crushed using a crusher. The crusher includes a traction machine, a crushing chamber (1) fixed on the traction machine and a crushing blade shaft (2) inside it. An electrostatic generating mechanism is provided on the inner wall of the crushing chamber (1). The electrostatic generating mechanism includes a set of chemical fiber cloth (3) with one end fixed on the inner wall of the crushing chamber (1). The chemical fiber cloth (3) is evenly distributed on the inner wall of the crushing chamber (1).

3. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 2, characterized in that, The crushing chamber (1) is provided with a discharge channel (4) at the outlet end. The inner wall of the discharge channel (4) is provided with a spiral groove (5). An electrostatic generating mechanism is provided on the inner wall of the spiral groove (5). The discharge channel (4) is inclined. A transmission mechanism is provided between the traction machine's traveling wheel and the discharge channel (4) to make the discharge channel (4) rotate.

4. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 1, characterized in that, In step 2), the agricultural and forestry waste is any one of corn cobs, rice husks, sawdust, and waste branches; the pyrolysis heating rate is controlled at 5-10 ℃ / min, and the constant temperature pyrolysis holding time is 2-4 h, to obtain functional biochar with an ash content of 10%-25% and high PFR abundance.

5. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 1, characterized in that, In step 3), the optimal application ratio of biochar is 8%-12% of the dry weight of straw.

6. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 1, characterized in that, In step 5), the surface straw stubble coverage rate after mixing is controlled to be below 15%.

7. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 1, characterized in that, The soil aerator includes an air source (6) and an air rod connected thereto. The air rod includes an inner rod (7) and an outer rod (8). A set of aeration holes (701) are distributed along the length direction on the inner rod (7). The outer rod (8) is sleeved on the outer surface of the inner rod (7) and has a connecting hole (801) corresponding to the aeration hole (701).

8. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 7, characterized in that, The distance between the air vents (701) is 10cm, and the length of the inner rod (7) is 70cm.

9. The method for enhancing straw decomposition with biochar associated with free radicals according to claim 1, characterized in that, The mixing operation is carried out by a mixer, which includes a traction machine and a trenching shovel (9) connected to it, and a mixing unit. The mixing unit includes a spiral rod (10) with a pointed head, a set of intersecting mixing rods (11) inside the spiral rod (10), and a rotation drive unit at the tail of the spiral rod (10).

10. The method for enhancing straw decomposition with associated free radicals using biochar according to claim 9, characterized in that, The rotary drive unit includes a drive motor (12) and a connected rotary support frame. The rotary support frame includes a connected L-shaped support rod (13) and a rotary rod (14) rotatably connected to its horizontal end. The support rod (13) and the rotary rod (14) are driven by a bevel gear mechanism (15). The uppermost end of the support rod (13) is connected to the drive motor (12). The stirring unit is fixedly connected to the front end of the rotary rod (14).

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