Multifunctional efficient carbon sequestration fertilizer based on addition of iron-based nanoparticles and preparation method of multifunctional efficient carbon sequestration fertilizer

Abstract

The invention provides a multifunctional efficient carbon sequestration fertilizer based on iron-based nanoparticle addition and a preparation method thereof, and belongs to the technical field of agricultural fertilizers. Through multi-element compounding of the raw materials, organic combination of an organic fertilizer and an inorganic fertilizer is achieved, under the condition that sufficient supply of crop nutrients is guaranteed, conversion of organic matter in the organic fertilizer into soil organic matter can be effectively promoted through addition of the iron-based nanoparticles mainly represented by nano ferroferric oxide or nano zero-valent iron, and the soil quality is improved. The soil carbon sequestration capability is obviously improved. The effects of a microbial agent and humic acid are not reduced, the soil microbial activity can be improved, the environment-friendly effect is achieved, plant growth and development can be promoted, and the crop yield and quality are improved. The multi-element fertilizer prepared by the invention is good in slow release effect, long in slow release time, simple in preparation method and low in cost, and has relatively good popularization and application values.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural fertilizers, and particularly to a multifunctional and highly efficient carbon-fixing fertilizer based on the addition of iron-based nanoparticles and a preparation method thereof. Background Art

[0002] Traditional fertilizers face the problem of low nutrient utilization rate in agricultural production. Especially for key nutrient elements such as nitrogen and phosphorus, due to factors such as soil adsorption, leaching or volatilization, the proportion actually absorbed by crops is insufficient. This not only increases the fertilization cost but also may lead to environmental risks such as soil compaction and water eutrophication. To improve the nutrient utilization efficiency, some studies have tried to extend the fertilizer action time by adding slow-release agents or coating materials, but such methods have limited effects on enhancing carbon fixation ability and may affect the fertilizer efficiency stability due to the mismatch between the material degradation rate and crop requirements.

[0003] In recent years, integrating carbon fixation function into the fertilizer system has become a research hotspot. For example, using biochar or organic materials as carriers to adsorb carbon dioxide. However, conventional carbon-fixing materials generally have problems such as fast mineralization rate and short retention period, and are easily decomposed by microbial action in the soil, making it difficult to achieve the long-term carbon fixation goal. At the same time, the binding mode between some materials and fertilizer nutrients is single, and the dynamic balance between carbon fixation and nutrient release cannot be effectively coordinated, resulting in insufficient nutrient supply during the critical growth period of crops and limiting the further improvement of fertilizer efficiency.

[0004] Iron-based materials have received attention in the field of soil improvement due to their environmental friendliness and redox activity. Existing studies have used iron oxides to passivate heavy metals or adjust soil pH value, but traditional iron-based materials have a small specific surface area and insufficient reaction sites, and the synergistic effect with fertilizer components is weak. Although nanotechnology provides a new way to optimize material properties, the application of iron-based nanoparticles in fertilizers still faces technical bottlenecks: on the one hand, nanoparticles are prone to agglomeration due to high surface energy, reducing the dispersion uniformity and the binding efficiency with nutrients; on the other hand, the existing preparation processes are difficult to accurately control the crystal structure and surface modification of nanoparticles, resulting in their migration, stability and nutrient slow-release effect in the soil not reaching the ideal state. These problems have not fully released the potential of iron-based nanomaterials in enhancing fertilizer efficiency and restricted the actual application effect of multifunctional carbon-fixing fertilizers. Summary of the Invention

[0005] The purpose of the present invention is to provide a multifunctional and highly efficient carbon-fixing fertilizer based on the addition of iron-based nanoparticles and a preparation method thereof, which has excellent fertilizer efficiency.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a carbon-fixing multi-component fertilizer, and the raw materials contain by mass parts:

[0008] 35 - 40 parts of corn straw particles, 20 - 25 parts of decomposed pig manure particles, 0.1 - 0.15 parts of nano - ferroferric oxide, 0.08 - 0.12 parts of nano - zero - valent iron, 5 - 6 parts of humic acid, 0.5 - 0.7 parts of compound microbial inoculant, 12 - 15 parts of urea, 6 - 8 parts of potassium dihydrogen phosphate, 5 - 6 parts of potassium chloride, 0.3 - 0.4 parts of boric acid, 0.4 - 0.6 parts of potassium hydroxide, 2.5 - 3 parts of liquid modified hydrophilic polyurethane resin.

[0009] Preferably, the organic matter content of the decomposed pig manure particles is ≥45%.

[0010] Preferably, the compound microbial inoculant contains Bacillus subtilis and Bacillus mucilaginosus with a viable bacteria number ratio of 2:1.

[0011] Preferably, the specific surface area of the nano - particles of nano - ferroferric oxide or nano - zero - valent iron is ≥50m 2 / g.

[0012] The present invention also provides a preparation method of the above carbon - sequestration multi - element fertilizer, which comprises the following steps:

[0013] (1) Mix and crush corn straw and decomposed pig manure to form a mixed substrate;

[0014] (2) Mix the compound microbial inoculant, urea, nano - ferroferric oxide, nano - zero - valent iron, humic acid, potassium dihydrogen phosphate and potassium chloride, heat to 75 - 85°C and continuously stir at 180 - 220 revolutions per minute for 30 - 50 minutes to obtain a suspension;

[0015] (3) Dilute the suspension obtained in step (2) with water and spray it onto the mixed substrate to obtain a moist material;

[0016] (4) Granulate the moist material in a drum granulator, and add the liquid modified hydrophilic polyurethane resin in portions during the granulation process, with the total addition amount being 2.5% - 3% of the total mass of the material;

[0017] (5) Dry the obtained particles at 35 - 45°C until the moisture content ≤8% to obtain the carbon - sequestration multi - element fertilizer.

[0018] Preferably, in step (1), more than 90% of the particle diameters after crushing are less than 1 cm.

[0019] Preferably, the heating rate in step (2) is 2 - 3°C / min, and the oxygen content in the system is maintained ≤5% during the stirring process.

[0020] Preferably, the granulation temperature in step (4) is controlled at 45 - 55°C, the particle diameter is controlled at 2.5 - 4.5 mm, and the roundness is ≥85%.

[0021] The present invention also provides the application of the above carbon-fixing multi-component fertilizer in crop cultivation. The crops include rice, tomato or corn, and the application method includes combined application of basal application and topdressing.

[0022] Preferably, for rice, the total application amount is 750-850 kg / ha, and the proportion of basal application is 70-80%; for tomato, the total application amount is 900-1100 kg / ha; for corn, the total application amount is 800-1000 kg / ha.

[0023] Technical effects and advantages of the present invention:

[0024] Through the multi-component compounding of raw materials, the present invention realizes the organic combination of organic fertilizer and inorganic fertilizer. While ensuring the sufficient supply of crop nutrients, the addition of iron-based nanoparticles mainly represented by nano-ferroferric oxide or nano-zero valent iron can effectively promote the conversion of organic matter in organic fertilizer into soil organic matter, and significantly improve the soil carbon fixation ability. The present invention does not reduce the efficacy of microbial inoculum and humic acid and can improve the soil microbial activity, is environmentally friendly, and can also promote plant growth and development, improve crop yield and quality. The multi-component fertilizer prepared by the present invention has good fertilizer slow-release effect, long slow-release time, simple preparation method and low cost, and has good popularization and application value.

[0025] The fertilizer of the present invention shows significant dual advantages of carbon fixation and efficiency increase and yield improvement in field experiments. By optimizing the carbon-nitrogen co-release mode, it maintains a more stable soil carbon pool level during the whole growth period of crops, and at the same time extends the effective supply period of nitrogen nutrient, so that the nutrient requirements at the key growth stages of crops such as rice and corn are accurately matched, and finally the synchronous improvement of yield and fruit nutritional quality is achieved, and the environmental emissions are significantly reduced. This technical solution innovatively couples the functions of iron-based materials with agronomic requirements, and solves the core contradiction of the mismatch between the mineralization rate and nutrient release of traditional carbon-fixing fertilizers. Through the collaborative design of the material-soil-crop system, it realizes the synchronous optimization of soil carbon sequestration intensity and fertilizer utilization efficiency without relying on exogenous additives, and provides a new technical carrier with both carbon emission reduction and yield increase potential for agricultural green production. Specific embodiments

[0026] The present invention provides a carbon-fixing multi-element fertilizer, and the raw materials by mass fraction include: 35-40 parts of corn straw particles, 20-25 parts of decomposed pig manure particles, 0.1-0.15 parts of nano-ferroferric oxide, 0.08-0.12 parts of nano-zero-valent iron, 5-6 parts of humic acid, 0.5-0.7 parts of compound microbial inoculum, 12-15 parts of urea, 6-8 parts of potassium dihydrogen phosphate, 5-6 parts of potassium chloride, 0.3-0.4 parts of boric acid, 0.4-0.6 parts of potassium hydroxide, and 2.5-3 parts of liquid modified hydrophilic polyurethane resin. Preferably, the organic matter content of the decomposed pig manure particles is ≥45%. Preferably, the compound microbial inoculum contains Bacillus subtilis and Bacillus mucilaginosus with a viable bacteria ratio of 2:1. Preferably, the specific surface area of the nano-particles of the nano-ferroferric oxide or nano-zero-valent iron is ≥50m 2 / g.

[0027] The present invention also provides a preparation method of the above carbon-fixing multi-element fertilizer, which includes the following steps: (1) Mix and crush corn straw and decomposed pig manure to form a mixed substrate; (2) Mix the compound microbial inoculum, urea, nano-ferroferric oxide, nano-zero-valent iron, humic acid, potassium dihydrogen phosphate and potassium chloride, heat up to 75-85°C and continuously stir at 180-220 revolutions per minute for 30-50 minutes to obtain a suspension; (3) Dilute the suspension obtained in step (2) with water and spray it onto the mixed substrate to obtain a moist material; (4) Roll and granulate the moist material in a drum granulator, and add the liquid modified hydrophilic polyurethane resin in portions during the granulation process, and the total addition amount is 2.5%-3% of the total mass of the material; (5) Dry the obtained particles at 35-45°C until the moisture content is ≤8% to obtain the carbon-fixing multi-element fertilizer.

[0028] Preferably, in step (1), more than 90% of the particle size after crushing is less than 1 cm. Preferably, the heating rate in step (2) is 2-3°C / min, and the oxygen content in the system is kept ≤5% during the stirring process. Preferably, the granulation temperature in step (4) is controlled at 45-55°C, the particle diameter is controlled at 2.5-4.5 mm, and the roundness is ≥85%. The present invention also provides the application of the above carbon-fixing multi-element fertilizer in crop planting, and the crops include rice, tomato or corn, and the application method includes combined application of base application and topdressing. Preferably, for rice, the total application amount is 750-850 kg / ha, and the base application accounts for 70-80%; for tomato, the total application amount is 900-1100 kg / ha; for corn, the total application amount is 800-1000 kg / ha.

[0029] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0030] Example 1

[0031] This embodiment provides a carbon-fixing multi-element fertilizer based on iron-based nanoparticles and a preparation method thereof. The raw material composition is as follows by mass fraction: 38 parts of corn straw particles, 22 parts of decomposed pig manure particles, 0.12 part of nano-ferroferric oxide, 0.09 part of nano-zero-valent iron, 5.5 parts of humic acid, 0.6 part of compound microbial inoculant (the viable count ratio of Bacillus subtilis to Bacillus mucilaginosus is 2:1), 13.5 parts of urea, 7.2 parts of potassium dihydrogen phosphate, 5.8 parts of potassium chloride, 0.35 part of boric acid, 0.5 part of potassium hydroxide, and 2.8 parts of liquid modified hydrophilic polyurethane resin. The organic matter content of the decomposed pig manure particles is ≥ 45%.

[0032] The preparation method is implemented according to the following steps: Mix the corn straw and the decomposed pig manure and mechanically crush them until the particle size of more than 90% is less than 1 cm to form a mixed substrate; Stir the compound microbial inoculant and urea at 28 ± 2 °C at 180 revolutions per minute for 20 minutes to form a uniform mixture; Add nano-ferroferric oxide, nano-zero-valent iron, humic acid, potassium dihydrogen phosphate, and potassium chloride to the mixture in sequence, heat up to 80 °C, and continuously stir at 200 revolutions per minute for 40 minutes to obtain a viscous suspension; Dilute the suspension according to a mass ratio of 1:1000 with water and evenly spray it onto the mixed substrate, controlling the moisture content of the material within the range of 28% - 32%; Finally, granulate the moist material by rolling in a drum granulator at a rotation speed of 12 revolutions per minute, and evenly add the liquid modified hydrophilic polyurethane resin three times according to 2.8% of the total mass of the material during the granulation process to form regular particles with a diameter of 3 - 4 mm. The finished product is dried by hot air at 40 °C until the moisture content of the particles ≤ 8%.

[0033] Example 2

[0034] This embodiment provides a carbon-fixing multi-element fertilizer based on iron-based nanoparticles and a preparation method thereof. The raw material composition is as follows by mass fraction: 35 parts of corn straw particles, 25 parts of decomposed pig manure particles, 0.15 part of nano-ferroferric oxide, 0.12 part of nano-zero-valent iron, 6.0 parts of humic acid, 0.8 part of compound microbial inoculant (the viable count ratio of Bacillus subtilis to Bacillus mucilaginosus is 2:1), 15 parts of urea, 6.8 parts of potassium dihydrogen phosphate, 6.2 parts of potassium chloride, 0.40 part of boric acid, 0.6 part of potassium hydroxide, and 3.0 parts of liquid modified hydrophilic polyurethane resin. The organic matter content of the decomposed pig manure particles is ≥ 45%.

[0035] The preparation method is implemented according to the following steps: Mix corn straw with decomposed pig manure and mechanically crush it until more than 90% of the particle size is less than 1 cm to form a mixed substrate; Mix the compound microbial inoculant and urea and stir at 200 revolutions per minute for 25 minutes at 30 ± 2 °C to form a uniform mixture; Sequentially add nano-ferroferric oxide, nano-zero-valent iron, humic acid, potassium dihydrogen phosphate and potassium chloride to the mixture, heat up to 85 °C and continuously stir at 220 revolutions per minute for 45 minutes to obtain a viscous suspension; Dilute the suspension with water according to a mass ratio of 1:1200 and evenly spray it onto the mixed substrate, controlling the moisture content of the material within the range of 30% - 34%; Finally, roll and granulate the wet material in a drum granulator at a rotational speed of 15 revolutions per minute, and evenly add liquid modified hydrophilic polyurethane resin three times according to 3.0% of the total mass of the material during the granulation process to form regular particles with a diameter of 3 - 5 mm. The finished product is dried by hot air at 45 °C until the moisture content of the particles ≤ 8%.

[0036] Example 3

[0037] This example provides a carbon-fixing multi-element fertilizer based on iron-based nanoparticles and its preparation method. The raw material composition is as follows by mass fraction: 40 parts of corn straw particles, 20 parts of decomposed pig manure particles, 0.10 part of nano-ferroferric oxide, 0.08 part of nano-zero-valent iron, 5.0 parts of humic acid, 0.5 part of compound microbial inoculant (the viable count ratio of Bacillus subtilis to Bacillus mucilaginosus is 2:1), 12 parts of urea, 7.5 parts of potassium dihydrogen phosphate, 5.5 parts of potassium chloride, 0.30 part of boric acid, 0.4 part of potassium hydroxide, and 2.5 parts of liquid modified hydrophilic polyurethane resin. The organic matter content of the decomposed pig manure particles ≥ 45%.

[0038] The preparation method is implemented according to the following steps: Mix corn straw with decomposed pig manure and mechanically crush it until more than 90% of the particle size is less than 1 cm to form a mixed substrate; Mix the compound microbial inoculant and urea and stir at 150 revolutions per minute for 15 minutes at 25 ± 2 °C to form a uniform mixture; Sequentially add nano-ferroferric oxide, nano-zero-valent iron, humic acid, potassium dihydrogen phosphate and potassium chloride to the mixture, heat up to 75 °C and continuously stir at 180 revolutions per minute for 35 minutes to obtain a viscous suspension; Dilute the suspension with water according to a mass ratio of 1:800 and evenly spray it onto the mixed substrate, controlling the moisture content of the material within the range of 26% - 30%; Finally, roll and granulate the wet material in a drum granulator at a rotational speed of 10 revolutions per minute, and evenly add liquid modified hydrophilic polyurethane resin three times according to 2.5% of the total mass of the material during the granulation process to form regular particles with a diameter of 2 - 3 mm. The finished product is dried by hot air at 35 °C until the moisture content of the particles ≤ 8%.

[0039] Example 4

[0040] This embodiment provides a carbon-fixing multi-element fertilizer based on iron-based nanoparticles and a preparation method thereof. The raw material composition is as follows by mass fraction: 36 parts of corn straw particles, 24 parts of decomposed pig manure particles, 0.14 parts of nano-ferroferric oxide, 0.10 parts of nano-zero-valent iron, 5.8 parts of humic acid, 0.7 parts of compound microbial inoculum (the viable bacteria number ratio of Bacillus subtilis to Bacillus mucilaginosus is 2:1), 14 parts of urea, 7.0 parts of potassium dihydrogen phosphate, 6.0 parts of potassium chloride, 0.38 parts of boric acid, 0.55 parts of potassium hydroxide, and 2.9 parts of liquid modified hydrophilic polyurethane resin. The organic matter content of the decomposed pig manure particles is ≥45%.

[0041] The preparation method is implemented according to the following steps: Mix the corn straw and the decomposed pig manure and mechanically crush them until the particle size of more than 90% of the particles is less than 1 cm to form a mixed substrate; Stir the compound microbial inoculum and urea at 29±2 °C at a speed of 190 revolutions per minute for 22 minutes to form a uniform mixture; Add nano-ferroferric oxide, nano-zero-valent iron, humic acid, potassium dihydrogen phosphate and potassium chloride to the mixture in sequence, heat up to 82 °C and continuously stir at a speed of 210 revolutions per minute for 42 minutes to obtain a viscous suspension; Dilute the suspension with water according to a mass ratio of 1:1100 and evenly spray it onto the mixed substrate, and control the moisture content of the material within the range of 29% - 31%; Finally, roll and granulate the wet material in a drum granulator at a speed of 13 revolutions per minute, and evenly add the liquid modified hydrophilic polyurethane resin three times according to 2.9% of the total mass of the material during the granulation process to form regular particles with a diameter of 3.5 - 4.5 mm. The finished product is dried with hot air at 42 °C until the moisture content of the particles ≤8%.

[0042] Example 5

[0043] This embodiment provides a carbon-fixing multi-element fertilizer based on iron-based nanoparticles and a preparation method thereof. The raw material composition is as follows by mass fraction: 37 parts of corn straw particles, 23 parts of decomposed pig manure particles, 0.13 parts of nano-ferroferric oxide, 0.09 parts of nano-zero-valent iron, 5.6 parts of humic acid, 0.65 parts of compound microbial inoculum (the viable bacteria number ratio of Bacillus subtilis to Bacillus mucilaginosus is 2:1), 13.8 parts of urea, 7.3 parts of potassium dihydrogen phosphate, 5.9 parts of potassium chloride, 0.36 parts of boric acid, 0.52 parts of potassium hydroxide, and 2.85 parts of liquid modified hydrophilic polyurethane resin. The organic matter content of the decomposed pig manure particles is ≥45%.

[0044] The preparation method is implemented according to the following steps: Mix corn straw with decomposed pig manure and mechanically crush it until more than 90% of the particle size is less than 1 cm to form a mixed substrate; Stir the compound microbial inoculant and urea at 27 ± 2 °C at 175 revolutions per minute for 18 minutes to form a uniform mixture; Add nano-ferroferric oxide, nano-zero valent iron, humic acid, potassium dihydrogen phosphate, and potassium chloride to the mixture in sequence, heat up to 78 °C, and continuously stir at 195 revolutions per minute for 38 minutes to obtain a viscous suspension; Dilute the suspension with water according to a mass ratio of 1:950 and evenly spray it onto the mixed substrate, controlling the moisture content of the material within the range of 27% - 29%; Finally, granulate the moist material by rolling in a drum granulator at a rotation speed of 11 revolutions per minute. During the granulation process, add liquid modified hydrophilic polyurethane resin evenly in three portions according to 2.7% of the total mass of the material to form regular particles with a diameter of 3.2 - 3.8 mm. The finished product is dried with hot air at 38 °C until the moisture content of the particles ≤ 8%.

[0045] Comparative Example 1

[0046] This comparative example provides a carbon-fixing multi-component fertilizer based on iron-based nanoparticles and its preparation method. The raw material composition is calculated by mass as follows: 38 parts of corn straw particles, 22 parts of decomposed pig manure particles, 5.5 parts of humic acid, 0.6 part of compound microbial inoculant (the viable bacteria number ratio of Bacillus subtilis to Bacillus mucilaginosus is 2:1), 13.5 parts of urea, 7.2 parts of potassium dihydrogen phosphate, 5.8 parts of potassium chloride, 0.35 part of boric acid, 0.5 part of potassium hydroxide, and 2.8 parts of liquid modified hydrophilic polyurethane resin. The organic matter content of the decomposed pig manure particles ≥ 45%.

[0047] The preparation method is implemented according to the following steps: Mix corn straw with decomposed pig manure and mechanically crush it until more than 90% of the particle size is less than 1 cm to form a mixed substrate; Stir the compound microbial inoculant and urea at 28 ± 2 °C at 180 revolutions per minute for 20 minutes to form a uniform mixture; Add humic acid, potassium dihydrogen phosphate, and potassium chloride to the mixture in sequence, heat up to 80 °C, and continuously stir at 200 revolutions per minute for 40 minutes to obtain a viscous suspension; Dilute the suspension with water according to a mass ratio of 1:1000 and evenly spray it onto the mixed substrate, controlling the moisture content of the material within the range of 28% - 32%; Finally, granulate the moist material by rolling in a drum granulator at a rotation speed of 12 revolutions per minute. During the granulation process, add liquid modified hydrophilic polyurethane resin evenly in three portions according to 2.8% of the total mass of the material to form regular particles with a diameter of 3 - 4 mm. The finished product is dried with hot air at 40 °C until the moisture content of the particles ≤ 8%.

[0048] Experimental Example

[0049] I. Experimental Design and Implementation

[0050] To systematically verify the comprehensive effects of this fertilizer on soil improvement, nutrient slow release, and crop yield and quality improvement, three representative crops, namely rice, tomato, and corn, were selected for field trials. The experimental field is located in the warm temperate monsoon climate zone at 32°18′ north latitude, with an average annual temperature of 14.6°C and an annual precipitation of 920 mm. Three treatment groups were set up: Group T1 applied the carbon-fixing multi-element fertilizer prepared in Example 1, Group T2 applied the control fertilizer with iron-based nanoparticles removed (Comparative Example 1), and Group CK applied a commercially available 15-15-15 compound fertilizer. The application rates of all treatment groups were calculated according to the principle of equal nitrogen (the difference in total nitrogen content ≤ 2.5%). Each treatment had 4 replicates, and a randomized block arrangement was adopted, with a plot area of 30 m 2 . The basic fertility of the experimental field was uniform (coefficient of variation < 8%). Before sowing, 15 t / ha of well-rotted cow dung was uniformly applied and plowed to a depth of 25 cm.

[0051] II. Crop Planting and Management Plan

[0052] (I) Rice Field Trial

[0053] The japonica rice variety Ningjing 7 was selected. Dry nursery seedlings were raised on April 10, and mechanical transplanting was carried out on May 20 with a row spacing of 25 cm × 13 cm. In Group T1, 600 kg / ha of fertilizer was applied as basal fertilizer, and 150 kg / ha was topdressed during the tillering stage; in Group CK, 480 kg / ha of compound fertilizer was applied as basal fertilizer, and 75 kg / ha of urea was topdressed during the tillering stage. Shallow water layer management (3 - 5 cm) was implemented throughout the growth period, and the field was drained and dried for 7 days at the end of the tillering stage to control tillering. The tiller number, plant height, and SPAD value of the second-to-last leaf were measured 30 days, 60 days, and 90 days after transplanting, respectively. Rhizosphere soil samples were collected at the harvest stage, and the organic carbon content in the 0 - 20 cm soil layer was measured.

[0054] (II) Tomato Protected Cultivation Trial

[0055] The tomato variety Jinpeng 8 was selected. Plug seedlings were raised on February 15 and transplanted into a solar greenhouse on March 25, adopting double-row high-ridge cultivation (plant spacing 45 cm, row spacing 60 cm). In Group T1, 800 kg / ha of fertilizer was applied as basal fertilizer, and 200 kg / ha was topdressed at the initial flowering stage; in Group CK, 640 kg / ha of compound fertilizer was applied as basal fertilizer, and 90 kg / ha of urea was topdressed. The soil water content was monitored by a tensiometer to maintain the field water holding capacity at 70% - 80%. Rhizosphere soil of the plants was collected at the fruit setting stage and color turning stage, respectively, to measure the microbial biomass carbon and phosphatase activity, and the soluble solids and vitamin C content of the fruits were measured at the maturity stage.

[0056] (III) Corn Field Trial

[0057] Cultivated variety: Fumin 985, mechanically precision sown on April 25th (density 67,500 plants / ha). In group T1, 700 kg / ha was applied as basal fertilizer and 200 kg / ha was topdressed at the large bell-mouth stage; in group CK, 560 kg / ha of compound fertilizer was applied as basal fertilizer and 105 kg / ha of urea was topdressed. At the jointing stage, tasseling stage, and filling stage, plant height, stem diameter, and leaf area index were measured, and leachate at a depth of 20 cm was collected synchronously to analyze the dynamic changes of ammonium nitrogen. After harvesting, the crude protein content of grains was measured.

[0058] III. Dynamic Monitoring and Analysis Methods

[0059] (I) Soil Parameter Detection

[0060] Organic carbon content: The external heating method with potassium dichromate was used. In each plot, a 0-20 cm mixed soil sample was collected by the five-point sampling method, dried at 105°C, and passed through a 0.25 mm sieve. The average value was determined by measuring three replicates.

[0061] Microbial activity: Microbial biomass carbon was determined by the chloroform fumigation-K2SO4 extraction method, phosphatase activity was measured by the p-nitrophenyl phosphate method, and urease activity was characterized by the amount of NH4 + -N generated after 24 hours of cultivation.

[0062] Dynamic nutrient release: Ceramic head leachometers were buried at a depth of 20 cm in each plot. Leachate was collected weekly. Ammonium nitrogen was determined by the Nessler's reagent colorimetric method, nitrate nitrogen was determined by the ultraviolet spectrophotometry (double-wavelength correction), and available phosphorus was determined by the molybdenum antimony resistance colorimetric method.

[0063] (II) Crop Index Determination

[0064] Yield components: For rice, actual yield was measured in 5 m 2 harvested areas, and the number of effective panicles, grains per panicle, and 1000-grain weight were determined; for tomatoes, the number of fruits per plant and single fruit weight were counted by harvesting the middle two rows; for corn, the ear length, barren tip length, and 100-grain weight were determined by harvesting the middle four rows.

[0065] Quality analysis: The amylose content of rice was determined according to GB / T 15683, the soluble solids of tomatoes were measured with a digital refractometer, and the crude protein content of corn was determined by the Kjeldahl method (conversion factor 6.25).

[0066] IV. Experimental Results and Data Analysis

[0067] Table 1 Dynamic Changes in Soil Improvement Effects (Paddy Field)

[0068]

[0069]

[0070] Table 2 Correlation between Tomato Quality and Rhizosphere Microenvironment

[0071] Index Group T1 Group T2 Group CK Soluble solids (°Brix) 5.82±0.26a 5.17±0.29b 4.88±0.23c Vitamin C (mg / 100g) 22.3±1.7a 19.5±1.5b 17.1±1.3c <![CDATA[Actinomycetes (×10 4 CFU / g)]]> 8.6±0.5a 6.2±0.4b 4.8±0.3c Phosphatase activity (μmol / g / h) 4.08±0.27a 3.53±0.23b 2.95±0.20c

[0072] Table 3 Nutrient Release Characteristics during the Growth Period of Maize

[0073]

[0074] Table 4 Effects of Improving Crop Yield and Quality

[0075]

[0076]

[0077] V. Conclusion Verification and Mechanism of Action

[0078] Soil carbon sequestration and efficiency improvement: After rice harvest, the soil organic carbon content in the T1 group reached 16.8 g / kg, which was 33.3% higher than that in the CK group (p < 0.01), and the difference was already apparent at the full tillering stage (14.7 vs 12.8 g / kg), indicating that iron-based nanoparticles can accelerate the conversion of organic matter. The microbial biomass carbon and urease activity increased by 46.4% and 30.6% respectively, verifying the biological pathway for promoting carbon fixation.

[0079] Nutrient slow-release characteristics: At the jointing stage of maize, the soil ammonium nitrogen concentration in the T1 group (8.4 mg / L) was 51.4% lower than that in the CK group, and it remained at 6.9 mg / L during the filling stage, indicating that the fertilizer release period was extended by 35 - 40 days. The nitrogen use efficiency was increased to 61.2%, and the nitrogen loss was reduced by 28.6% compared with conventional fertilization.

[0080] Crop quality improvement mechanism: The number of actinomycetes in the tomato rhizosphere was significantly positively correlated with the vitamin C content (r = 0.796, p < 0.05), and the phosphatase activity in the T1 group was 38.3% higher than that in the CK group, confirming that iron-based nanoparticles promote nutrient activation by regulating the microbial community, thereby improving the nutritional quality of fruits.

[0081] Comprehensive yield increase effect: The yield increase of the three types of crops reached 9.2% - 11.5%. Among them, the effective panicle number of rice increased by 14.2% (T1: 325 panicles / m 2 vs CK: 285 panicles / m 2 ), the 100-grain weight of maize increased by 6.8% (T1: 36.4 g vs CK: 34.1 g), and the differences in all quality indexes reached a significant level (p < 0.05).

[0082] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A carbon-fixing multi-element fertilizer, characterized in that, The raw materials contain, by mass parts: 35 - 40 parts of corn straw particles, 20 - 25 parts of decomposed pig manure particles, 0.1 - 0.15 parts of nano - ferroferric oxide, 0.08 - 0.12 parts of nano - zero - valent iron, 5 - 6 parts of humic acid, 0.5 - 0.7 parts of compound microbial inoculum, 12 - 15 parts of urea, 6 - 8 parts of potassium dihydrogen phosphate, 5 - 6 parts of potassium chloride, 0.3 - 0.4 parts of boric acid, 0.4 - 0.6 parts of potassium hydroxide, and 2.5 - 3 parts of liquid modified hydrophilic polyurethane resin.

2. The carbon-fixing multi-component fertilizer according to claim 1, wherein The organic matter content of the decomposed pig manure particles is ≥ 45%.

3. The carbon-fixing multi-element fertilizer according to claim 1, characterized in that, The compound microbial inoculum contains Bacillus subtilis and Bacillus mucilaginosus with a viable bacteria number ratio of 2:

1.

4. The carbon-fixing multi-element fertilizer according to claim 1, wherein The specific surface area of the nanoparticles of nano-sized magnetite or nano-sized zero-valent iron ≥ 50 m 2 / g.

5. A method for preparing the carbon-fixing multi-component fertilizer according to any one of claims 1 to 4, characterized in that, It includes the following steps: (1) Mix and crush corn straw and decomposed pig manure to form a mixed substrate; (2) Mix the compound microbial inoculum, urea, nano - ferroferric oxide, nano - zero - valent iron, humic acid, potassium dihydrogen phosphate and potassium chloride, heat up to 75 - 85 °C and continuously stir at 180 - 220 revolutions per minute for 30 - 50 minutes to obtain a suspension; (3) Dilute the suspension obtained in step (2) with water and spray it onto the mixed substrate to obtain a moist material; (4) Granulate the moist material in a drum granulator, and add the liquid modified hydrophilic polyurethane resin in portions during the granulation process, with the total addition amount being 2.5% - 3% of the total mass of the material; (5) Dry the obtained particles at 35 - 45 °C until the moisture content ≤ 8% to obtain the carbon - sequestering multi - element fertilizer.

6. The preparation method according to claim 5, characterized in that In step (1), more than 90% of the particle size after crushing is less than 1 cm.

7. The preparation method according to claim 5, characterized in that, The heating rate in step (2) is 2 - 3 °C / min, and the oxygen content in the system is kept ≤ 5% during the stirring process.

8. The preparation method according to claim 5, characterized in that The granulation temperature in step (4) is controlled at 45 - 55 °C, the particle diameter is controlled at 2.5 - 4.5 mm, and the roundness is ≥ 85%.

9. Use of the carbon-fixing multi-element fertilizer according to any one of claims 1 to 3 in crop cultivation, characterized in that, The crops include rice, tomato or corn, and the application method includes combined application of basal application and topdressing.

10. The application according to claim 9, wherein For rice, the total application amount is 750 - 850 kg / ha, and the basal application accounts for 70 - 80%; for tomato, the total application amount is 900 - 1100 kg / ha; For corn, the total application amount is 800 - 1000 kg / ha.

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