Method for improving acid neutralization capacity of organic fertilizer

Abstract

The present application relates to organic waste composting and acid soil improvement technical field, disclose a kind of method for improving the acid neutralization capacity of organic fertilizer.The method mixes livestock and poultry manure, crop straw and compound microbial inoculant, adjusts carbon-nitrogen ratio to 25~32, moisture content is 60%~70%, adds 100~500mg / kg of nano ferric oxide in the mass of dry matter, after mixing, placed in composting container with gas exchange structure, composting fermentation is carried out under aerobic condition, and water is added and turned over during fermentation, after maturation and screening, obtain organic fertilizer.The obtained organic fertilizer has higher acid neutralization capacity and carbonate content, is more conducive to improving acidity and improving the acid resistance of soil, and is suitable for livestock and poultry manure, crop straw resource utilization and acid soil improvement.

Description

Technical Field

[0001] This invention belongs to the field of organic fertilizer quality improvement, and discloses a method for improving the acid neutralization capacity of organic fertilizer. Background Technology

[0002] Organic fertilizer is an important product of the resource utilization of agricultural organic waste such as livestock and poultry manure and crop straw. When applied to the soil, it replenishes organic matter, nitrogen, phosphorus, potassium, and other nutrients, and improves soil structure, making it widely valuable in green agricultural production and waste recycling. With the expansion of acidic soil areas and the deepening of soil acidification, relying solely on conventional organic fertilizers to supplement nutrients is no longer sufficient to meet the long-term needs of acidic soil improvement. The carbonates and oxygen-containing functional groups contained in organic fertilizers, as acid-base buffering substances, can neutralize soil acidity to a certain extent and alleviate the re-acidification process. Therefore, the acid-neutralizing capacity of organic fertilizers has gradually become one of the important indicators for evaluating their potential for improving acidic soils. How to improve the acid-neutralizing capacity, carbonate content, and acid-base buffering performance of decomposition products during the composting process of organic waste is an important direction for improving the functional utilization level of organic fertilizers.

[0003] Aerobic composting is a common technical approach for treating livestock and poultry manure and crop straw. It involves controlling the carbon-to-nitrogen ratio, moisture content, aeration conditions, turning frequency, and microbial inoculation conditions of the materials to induce organic waste to undergo stages of heating, high-temperature maintenance, cooling maturation, and post-maturation stabilization, thereby obtaining fertilizer products with high maturity, low odor, and reduced pathogen risk. Existing composting control technologies mainly focus on shortening the maturation cycle, increasing the degree of humification, reducing nitrogen loss, reducing greenhouse gas emissions, enhancing nutrient retention capacity, and improving the hygiene and safety of compost. Common control materials include biochar, zeolite, bentonite, phosphate rock powder, iron-based minerals, and other porous or mineral additives. However, these technologies typically prioritize nutrient retention, pollution reduction, or improved maturation quality, paying insufficient attention to the formation process and targeted control of the acid-neutralizing capacity of compost products. The functional stability of compost products in acidic soil improvement still needs improvement.

[0004] In existing research and production practices, acid soil improvement typically relies on exogenous alkaline materials such as lime, dolomite powder, alkaline industrial byproducts, or mineral conditioners. While these materials can raise soil pH, their use can be hampered by issues such as high application rates, difficulty in matching reaction rates to crop needs, the risk of localized alkalization, limited nutrient replenishment capacity, and insufficient synergistic utilization with organic fertilizers. If the acid-neutralizing capacity of organic fertilizers could be directly enhanced during the composting stage, enabling them to provide nutrient supply, organic matter replenishment, and strong acidity buffering, the reliance on subsequent application of alkaline improvement materials alone could be reduced, and the comprehensive utilization value of organic fertilizers in acid soil remediation could be increased. Therefore, developing a method based on conventional composting systems, which can enhance the acid-neutralizing capacity of decomposition products through the regulation of small amounts of functional materials, has significant practical application value.

[0005] Iron-based materials exhibit good environmental adaptability in composting systems. Materials such as magnetite and iron(III) oxide have been used to regulate organic matter transformation, humification processes, nitrogen conversion, and microbial metabolism. Nano-iron(III) oxide, in particular, is considered to have the potential to participate in the regulation of the composting process due to its small particle size, large specific surface area, and ease of dispersion in compost materials. While existing technologies have focused on the effects of nano-iron(III) oxide on composting temperature changes, organic matter decomposition, nitrogen preservation, and humus formation, there is still a lack of clear process designs and operable technical solutions regarding its application in aerobic composting of agricultural organic waste such as cow manure and straw. These solutions aim to enhance the acid neutralization capacity of decomposition products, promote carbonate accumulation, increase the abundance of oxygen-containing functional groups, and improve the acid-soil-improving capacity of the resulting organic fertilizer.

[0006] Therefore, existing organic fertilizer preparation technologies still have the following shortcomings: First, most composting processes only use maturity, nutrient content, and emission reduction effects as the main control indicators, lacking process control methods aimed at improving acid neutralization capacity; second, existing methods for improving acidic soils mostly rely on the addition of alkaline materials, failing to fully utilize the potential of organic fertilizers themselves to form acid buffer components; third, the application of iron-based additives in composting is relatively scattered, and a suitable combination scheme for the addition amount, material ratio, moisture content, turning regime, and post-ripening treatment has not yet been formed to improve the acid neutralization capacity of organic fertilizers and the soil's acid control capacity. Based on the above, it is necessary to propose a method that can improve the acid neutralization capacity of organic fertilizers during conventional aerobic composting, in order to obtain functional organic fertilizers more suitable for improving acidic soils. Summary of the Invention

[0007] To address the problem that existing organic fertilizer preparation technologies mainly focus on composting maturity, nutrient retention, nitrogen loss control, and greenhouse gas emission reduction, while lacking targeted regulation methods aimed at improving the acid neutralization capacity of compost products, this invention provides a method for improving the acid neutralization capacity of organic fertilizers.

[0008] This method uses livestock and poultry manure and crop straw as the main composting raw materials. By adjusting the carbon-nitrogen ratio, moisture content, amount of microbial agents, amount of nano-Fe3O4 added, aerobic fermentation conditions, water replenishment system, turning system, and post-ripening treatment conditions, the compost products can maintain the resource utilization properties of conventional organic fertilizers while having a high acid neutralization capacity, a high carbonate content, and a relatively stable acid-base buffering performance. This solves the technical problems of insufficient acid neutralization capacity of ordinary organic fertilizers for acidic soils, reliance on exogenous alkaline conditioning materials for acidic soil improvement, and single functional regulation target during composting.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0010] This invention provides a method for enhancing the acid neutralization capacity of organic fertilizers, comprising the following steps: First, livestock and poultry manure, crop straw, and compound microbial agents are mixed together, and the carbon-nitrogen ratio of the resulting mixture is adjusted to 25-32, and the moisture content is 60%-70%, to obtain premixed compost material.

[0011] The preferred animal manure is fresh cow manure, and the preferred crop straw is wheat straw. The amount of wheat straw added is determined based on the target carbon-to-nitrogen ratio after mixing the fresh cow manure and wheat straw. Preferably, the carbon-to-nitrogen ratio of the premixed compost is 27–29, more preferably about 28; the moisture content of the premixed compost is 63%–67%, more preferably about 65%.

[0012] The compound microbial agent is preferably an effective compound microbial agent, and its addition amount is 1% to 3% based on the total wet basis mass of livestock and poultry manure and crop straw, more preferably 2%. During mixing, the crop straw can be spread flat on the bearing surface first, and then the livestock and poultry manure and compound microbial agent can be added. The components are then evenly distributed by manual or mechanical mixing. Deionized water is added according to the moisture content test results of the material to bring the material to the set moisture content range.

[0013] Secondly, based on the dry matter mass of the premixed compost material, 100-500 mg / kg of nano-Fe3O4 is added to the premixed compost material and mixed evenly to obtain iron-containing compost material.

[0014] Preferably, the amount of nano-Fe3O4 added is 150–300 mg / kg dry matter; more preferably, the amount of nano-Fe3O4 added is 200 mg / kg dry matter. To improve the uniformity of nano-Fe3O4 distribution in compost materials, nano-Fe3O4 can be premixed with a portion of premixed compost materials to form iron-containing premixed particles, and then the iron-containing premixed particles can be further mixed with the remaining premixed compost materials to obtain iron-containing compost materials.

[0015] Next, the iron-containing compost material is placed in a composting container with a gas exchange structure and composted under aerobic conditions. During the composting process, water is added and the compost is turned over to obtain decomposed material.

[0016] The composting container includes a fermentation tank, a breathable material carrier bag placed inside the fermentation tank, and a perforated cover covering the opening of the fermentation tank. Iron-containing compost material is placed in the breathable material carrier bag and then placed inside the fermentation tank. The perforated cover covers the opening of the fermentation tank to meet the gas exchange requirements during the composting fermentation process and reduce moisture loss. The breathable material carrier bag can be made of non-woven fabric, and the fermentation tank can be made of plastic.

[0017] Composting fermentation is preferably carried out at an ambient temperature of 25–35℃, and more preferably at around 30℃. The total composting fermentation time is 75–105 days, and more preferably 90 days. During the first 30 days of composting fermentation, the moisture content of the material can be tested every 3 days, and deionized water can be added according to the test results to maintain the material at a suitable moisture content for aerobic decomposition. After 30 days of composting fermentation, the moisture content of the material can be gradually adjusted to about 40%, and subsequent decomposition can continue.

[0018] The turning schedule is as follows: turn the compost pile every 3 days for the first 7 days after the start of fermentation, turn it every 7 days from the 7th day to the 45th day of fermentation, and stop turning it after the 45th day, allowing it to continue to decompose. This turning schedule ensures that the compost material maintains good material uniformity and aeration in the early and middle stages of fermentation, and enters a more stable decomposition and post-maturation stage in the later stage.

[0019] Finally, the decomposed material is subjected to post-fermentation and screening to obtain organic fertilizer with enhanced acid neutralization capacity.

[0020] Air drying removes excess moisture from the decomposed material; sieving can be performed using 10-mesh, 60-mesh, or 100-mesh sieves depending on testing or usage requirements. The resulting organic fertilizer has a water extraction pH of 8.80–9.10, an acid neutralization capacity of not less than 70 cmol / kg, and a carbonate content of not less than 10 g / kg. The water extraction pH can be determined by shaking and allowing the air-dried organic fertilizer to stand in a 1:10 mass-to-volume ratio; the acid neutralization capacity can be determined by acid-base titration; and the carbonate content can be determined by gas chromatography.

[0021] In a preferred embodiment, 13 kg of fresh cow manure is placed in a composting container system, wheat straw is added, and the carbon-nitrogen ratio is adjusted to approximately 28. The moisture content is adjusted to approximately 65%, 2% effective microbial compound inoculant is added, and nano-Fe3O4 is added at a dosage of 200 mg / kg dry matter. After thorough mixing, the mixture is placed in a non-woven bag and then placed in a fermentation tank. The fermentation tank is covered with a perforated plastic lid, and aerobic composting fermentation is carried out at an ambient temperature of 30°C. During the composting fermentation, the above-mentioned water replenishment and turning system is followed. After fermentation and post-ripening for 90 days, an organic fertilizer with improved acid neutralization capacity is obtained.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects.

[0023] 1. This invention uses livestock and poultry manure and crop straw as basic raw materials. A small amount of nano Fe3O4 is added to the conventional aerobic composting process. With specific carbon-nitrogen ratio, moisture content, amount of microbial agent added, fermentation temperature, water replenishment system and turning system, it can obtain organic fertilizer with high acid neutralization capacity without the need to introduce a large amount of lime, dolomite powder or other alkaline mineral conditioning materials. The process flow is well compatible with existing agricultural organic waste composting systems.

[0024] 2. This invention uses a nano-Fe3O4 addition amount of 100–500 mg / kg dry matter, preferably 200 mg / kg dry matter, to enhance the acid neutralization capacity of organic fertilizer without disrupting the composting temperature succession process. According to experimental results, after adding nano-Fe3O4, the composting system still experiences a rapid heating phase, a high-temperature maintenance phase, and a later cooling and stabilization phase, and the temperature above 45°C can be maintained for a considerable period, indicating that this addition scheme is suitable for aerobic composting decomposition processes.

[0025] 3. The organic fertilizer obtained by this invention has a high acid neutralization capacity. Experimental results show that at the end of 90 days of composting, the acid neutralization capacity of the decomposition products treated with nano-Fe3O4 was 97.21 cmol / kg, higher than the 85.08 cmol / kg of the untreated products, indicating that the method of this invention can improve the neutralization capacity of compost products against acidic substances.

[0026] 4. The organic fertilizer obtained by this invention has a high carbonate content. Experimental results show that at the end of 90 days of composting, the carbonate content of the decomposition products treated with nano-Fe3O4 reached 13.18 g / kg, higher than the 9.01 g / kg in the untreated product. The increased organic functional groups and carbonate content are beneficial for enhancing the buffering and amendment capacity of the organic fertilizer for acidic soils.

[0027] 5. The decomposition products obtained by this invention exhibit strong organic functional group response characteristics. Fourier transform infrared spectroscopy analysis results show that the decomposition products treated with nano-Fe3O4 show strong response characteristics at 3430 cm⁻¹. -1 2920cm-1 1640cm -1 and 1080cm -1 The peak areas at all points were higher than those without treatment, indicating that the signals of hydroxyl groups, aliphatic structures, and oxygen-containing functional groups in the obtained decomposition products were enhanced, which is beneficial to improving the acid-base buffering performance of the compost products.

[0028] 6. The organic fertilizer obtained by this invention is suitable for improving acidic soils. The results of acidic soil incubation showed that after applying the decomposition products obtained from the treatment with added nano-Fe3O4, the soil pH at the end of 45 days was 4.89, higher than the 4.49 of the soil control alone and the 4.82 of the treatment without added nano-Fe3O4 decomposition products; simultaneously, its soil acid neutralization capacity reached 4.38 cmol / kg at the end of incubation, higher than the soil control alone and the treatment without addition. Therefore, the organic fertilizer obtained by this invention can slow down the pH decline of acidic soils and maintain a good acid neutralization capacity.

[0029] 7. This invention involves adding nano-Fe3O4 to an aerobic composting system of livestock and poultry manure and crop straw, and controlling the material ratio, moisture content, microbial agent dosage, fermentation conditions, water replenishment, and turning process to obtain organic fertilizer with enhanced acid neutralization capacity. This method has a wide range of raw material sources, clear operating steps, low addition amounts, and strong compatibility with conventional composting equipment and processes. The resulting organic fertilizer has the functions of replenishing organic matter, supplying nutrients, and buffering and improving acidic soils, making it suitable for widespread application in the resource utilization of agricultural organic waste and the improvement of acidic soils. Attached Figure Description

[0030] Figure 1 This refers to the temperature changes during the aerobic composting process of the present invention. Figure 2 The pH change during the aerobic composting process of this invention; Figure 3 This invention relates to the change in acid neutralization capacity during aerobic composting. Figure 4 This invention relates to the change in carbonate content during aerobic composting. Figure 5 Fourier transform infrared spectroscopy analysis of the decomposition products of the present invention; Figure 6 The changes in pH (A), acid neutralization capacity (B), organic matter (C), and soluble organic carbon (D) during soil culture using decomposition products according to the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. These embodiments are used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or conventional adjustments made based on the raw material types, addition amounts, moisture content, carbon-nitrogen ratio, fermentation conditions, turning regimes, and detection methods disclosed in the present invention shall fall within the scope of protection of the present invention.

[0032] This invention provides a method for enhancing the acid neutralization capacity of organic fertilizer. It uses livestock and poultry manure and crop straw as basic composting raw materials, compound microbial agents as fermentation initiation materials, and nano-Fe3O4 as composting regulation additives. During the aerobic composting process, by controlling the carbon-nitrogen ratio, moisture content, amount of nano-Fe3O4 added, fermentation temperature, turning frequency, and post-ripening time of the materials, organic fertilizer with enhanced acid neutralization capacity can be obtained.

[0033] In this invention, fresh cow manure is preferred as the livestock and poultry manure, and wheat straw is preferred as the crop straw. Before use, fresh cow manure is cleaned of stones, plastics, metal debris, and other obvious non-compostable impurities. Wheat straw is chopped or crushed before use to ensure it can be evenly mixed with the cow manure. The amount of wheat straw added is determined based on the target carbon-to-nitrogen ratio after mixing the cow manure and straw. The target carbon-to-nitrogen ratio is 25–32, preferably 27–29, and more preferably about 28.

[0034] In this invention, the compound microbial agent is preferably an effective microbial compound agent, and its addition amount is 1% to 3% based on the total wet weight of livestock and poultry manure and crop straw, preferably 2%. The compound microbial agent can be premixed with a small amount of composting raw materials before being mixed with all the composting raw materials to ensure the uniform distribution of the agent in the materials.

[0035] In this invention, the amount of nano-Fe3O4 added is 100–500 mg / kg dry matter, preferably 150–300 mg / kg dry matter, and more preferably 200 mg / kg dry matter, based on the dry matter mass of the premixed compost material. When adding nano-Fe3O4, a portion of the premixed compost material is first mixed with nano-Fe3O4 to form an iron-containing premixed material. Then, the iron-containing premixed material is repeatedly stirred with the remaining premixed compost material to obtain the iron-containing compost material. This premixing method avoids the agglomeration of nanoparticles in localized areas, resulting in a more uniform dispersion of the added material in the composting system.

[0036] The composting container used in this invention may include a fermentation tank, a breathable material carrier bag, and a perforated lid. The breathable material carrier bag is placed inside the fermentation tank; iron-containing compost material is loaded into the breathable material carrier bag and then placed inside the fermentation tank. The perforated lid covers the opening of the fermentation tank. The breathable material carrier bag can be made of non-woven fabric, and the perforated lid can be made of plastic with multiple small holes to meet the gas exchange requirements during composting and reduce excessive moisture loss from the compost pile. A digital thermometer can be installed in the center of the fermentation tank to record temperature changes in the compost pile.

[0037] The aerobic composting fermentation of the present invention can be carried out at an ambient temperature of 25 to 35°C, preferably at an ambient temperature of 30°C. The total composting time is 75 to 105 days, preferably 90 days. In the first 30 days after the start of composting fermentation, the water content can be detected every 3 days and deionized water is added to keep the water content of the pile at a level suitable for microbial activities. After 30 days of composting, as the temperature of the pile decreases and the intensity of microbial activities changes, the water content can be gradually reduced to about 40%, and the post-composting incubation is continued.

[0038] The pile turning system is as follows: within the first 7 days after the start of composting fermentation, turn the pile once every 3 days; from the 7th day to the 45th day after the start of composting fermentation, turn the pile once every 7 days; after the 45th day, stop turning the pile, and continue static decomposition and after-ripening. When turning the pile, take out the air-permeable material bag from the fermentation barrel, open it and fully turn the materials from the outside to the inside and from top to bottom, then put the materials back into the air-permeable material bag and place it back into the fermentation barrel. After turning the pile, re-cover the perforated cover and continue fermentation at the set temperature.

[0039] After composting is completed, the decomposed material is taken out and subjected to after-ripening treatment to obtain an organic fertilizer with improved acid neutralization capacity. Air-drying can be carried out under ventilated and cool conditions until the mass of the sample is substantially constant; sieving can be carried out with 10-mesh, 60-mesh or 100-mesh sieve according to subsequent uses. When applied to the field, the material sieved with a 10-mesh sieve can be used; for physical and chemical index determination or spectral analysis, the sample sieved with 60-mesh or 100-mesh can be further used.

[0040] Example 1: Preparation of organic fertilizer with improved acid neutralization capacity by cattle manure-straw composting treated with nano-Fe3O4 This example uses fresh cattle manure and wheat straw to construct a cattle manure-straw aerobic composting system. Weigh 13 kg of fresh cattle manure and place it in the composting system equipped with a 15-liter plastic composting tank; according to the carbon and nitrogen composition of fresh cattle manure and wheat straw, add 2 kg of wheat straw to adjust the carbon-nitrogen ratio of the mixture to about 28. Spread the quantified wheat straw and fresh cattle manure on the bearing surface and turn repeatedly to mix the straw and cattle manure evenly.

[0041] Add an effective microbial composite inoculant to the above mixture, and the addition amount is 2% of the total wet mass of livestock and poultry manure and crop straw. After adding the inoculant, continue turning to make the inoculant evenly distributed in the material. Then add deionized water to the mixture to adjust the water content to about 65%, so as to obtain the premixed composting material.

[0042] Nano Fe3O4 is added to the premixed compost material based on its dry matter mass. Specifically, in this embodiment, 1.05g of nano Fe3O4 is added at the composting scale, corresponding to an addition level of 200mg / kg dry matter. During addition, a portion of the premixed compost material is first premixed with nano Fe3O4 to obtain iron-containing premixed material; then, the iron-containing premixed material is added back to the remaining premixed compost material, and the mixture is repeatedly stirred until no obvious powder accumulation area is observed visually, thus obtaining the iron-containing compost material.

[0043] The iron-containing compost material is placed into non-woven bags, which are then placed inside a plastic fermentation tank. For convenient periodic sampling, an additional 500g of the mixed compost material can be used as a sampling unit, placed into a 200-mesh nylon bag, for a total of five sampling bags. These bags are then buried in the compost material. A digital thermometer is placed in the center of the fermentation tank, and the opening of the tank is covered with a perforated plastic lid to ensure gas exchange and reduce moisture loss.

[0044] Fermentation tanks containing iron-containing compost materials are placed in an ambient temperature of 30℃ for aerobic composting. For the first 30 days of composting, the moisture content is measured every 3 days, and deionized water is added as needed to maintain a suitable moisture level. Initially, the compost pile is turned every 3 days; from one week to day 45, it is turned every 7 days; after day 45, turning is stopped, and the pile is allowed to continue its static decomposition and maturation. After 30 days of composting, the activity of microorganisms in the pile gradually decreases, the pile temperature begins to drop, and the moisture content gradually decreases to approximately 40%, continuing incubation for another 60 days. The total composting time is 90 days.

[0045] Samples from the corresponding nylon bags were collected on days 0, 3, 9, 30, and 90 of the composting process. After each sampling, the samples were air-dried and passed through 10-mesh, 60-mesh, and 100-mesh sieves for pH, acid neutralization capacity, carbonate content, and Fourier transform infrared spectroscopy analysis.

[0046] The organic fertilizer prepared by the above method can reach a pH of about 8.98 after water leaching at the end of 90 days of composting, an acid neutralization capacity of 97.21 cmol / kg, and a carbonate content of 13.18 g / kg, making it suitable as a functional organic fertilizer for improving acidic soils.

[0047] Example 2: Implementation under different amounts of nano-Fe3O4 addition This embodiment is based on Example 1, only changing the amount of nano Fe3O4 added, while keeping the other raw material types, carbon-nitrogen ratio, moisture content, amount of microbial agent added, compost container, fermentation temperature, turning system, post-ripening time, and screening method the same.

[0048] Based on the dry matter mass of the premixed compost material, nano-Fe3O4 addition levels were set at 100 mg / kg dry matter, 150 mg / kg dry matter, 200 mg / kg dry matter, 300 mg / kg dry matter, 400 mg / kg dry matter, and 500 mg / kg dry matter. Nano-Fe3O4 was added to all treatments using a premixing method, i.e., nano-Fe3O4 was first mixed with a small amount of premixed compost material, and then thoroughly mixed with the entire premixed compost material.

[0049] Within the range of 100–500 mg / kg dry matter addition, the resulting compost materials can all complete decomposition and post-maturation according to the aerobic composting process described in Example 1. The preferred addition amount is 150–300 mg / kg dry matter, more preferably 200 mg / kg dry matter. At the 200 mg / kg dry matter addition level, the composting process did not disrupt the ability to maintain the high-temperature stage, and the acid neutralization capacity and carbonate content of the final compost product were both higher than those of the control treatment without nano-Fe3O4 addition.

[0050] Example 3: Implementation under different carbon-nitrogen ratios and moisture contents This embodiment is based on Example 1, but the carbon-nitrogen ratio and initial moisture content of the premixed compost material are adjusted, while the other conditions remain the same.

[0051] Fresh cow manure was mixed with wheat straw, and the amount of wheat straw added was adjusted to control the carbon-to-nitrogen ratio of the premixed compost at approximately 25, 28, and 32, respectively. Simultaneously, the initial moisture content of the premixed compost was adjusted to 60%, 65%, and 70%, respectively. 2% effective microbial compound inoculant was added to each treatment, along with nano-Fe3O4 at a concentration of 200 mg / kg dry matter.

[0052] When the carbon-to-nitrogen ratio is controlled at 25–32 and the initial moisture content is controlled at 60%–70%, the compost material can complete decomposition under aerobic conditions. Preferably, when the carbon-to-nitrogen ratio is controlled at 27–29 and the initial moisture content is controlled at 63%–67%, the compost material has good mixing uniformity, and the moisture content of the pile is suitable for turning and aeration. More preferably, when the carbon-to-nitrogen ratio is about 28 and the initial moisture content is about 65%, it can be matched with the 30°C, 90-day composting regime in Example 1 to obtain organic fertilizer with improved acid neutralization capacity.

[0053] Example 4: Organic Fertilizer Post-treatment and Quality Testing Methods The decomposed material obtained in Example 1 or Example 2 was removed from the fermentation tank, spread on a clean tray, and air-dried naturally to constant weight under ventilated, rain-protected, and pollution-free conditions. After air-drying, the samples were sieved. 10-mesh sieve samples were used for soil culture experiments, 60-mesh sieve samples were used for pH, acid neutralization capacity, and carbonate content determination, and 100-mesh sieve samples were used for infrared spectroscopy analysis.

[0054] For pH measurement, weigh 4.0g of air-dried organic fertilizer sample, add deionized water at a ratio of 1:10, shake on a shaker at 200rpm / min for 30 minutes, let stand for 30 minutes, and then take the supernatant for pH measurement.

[0055] Carbonate content was determined using the gas chromatography method. Before measurement, the sample was ground uniformly to ensure the particle size met the detection requirements. During measurement, the carbonate content was calculated based on the amount of gas produced by the reaction between the sample and the acid, and the result was expressed in grams per kilogram.

[0056] Acid neutralization capacity was determined using acid-base titration. A measured amount of air-dried organic fertilizer sample was taken, a measured amount of acid solution was added to react, and the neutralization capacity of the sample was calculated by back titration with alkali solution. The result was expressed as centimoles per kilogram. During the determination process, at least one parallel sample was prepared for the same treatment to reduce errors caused by sample inhomogeneity.

[0057] Fourier transform infrared spectroscopy (FTIR) was performed using the potassium bromide pellet method. The air-dried sample, after being sieved through a 100-mesh sieve, was mixed with potassium bromide, pelleted, and then scanned using a Fourier transform infrared spectrometer. The readings were recorded at 3430 cm⁻¹. -1 2920cm -1 1640cm -1 and 1080cm -1 The absorption peak area at a certain point is used to characterize the changes in signals related to hydroxyl groups, aliphatic structures, and oxygen-containing functional groups in the decomposition products.

[0058] Comparative Example 1: Cow manure-straw composting treatment without the addition of nano-Fe3O4 This comparative example is essentially the same as Example 1, except that nano-Fe3O4 is not added. Specifically, 13 kg of fresh cow manure was weighed, and 2 kg of wheat straw was added to adjust the carbon-to-nitrogen ratio to approximately 28. 2% of an effective microbial compound inoculant was added to adjust the moisture content to approximately 65%. The mixture was then placed in a non-woven bag and placed in a plastic fermentation tank for 90 days of aerobic composting at an ambient temperature of 30°C. During composting, the watering and turning procedures were followed as in Example 1.

[0059] After composting, the decomposition products were air-dried, sieved, and used for physicochemical index determination. The results showed that the untreated product, without nano-Fe3O4, had a water extraction pH of approximately 8.80, an acid neutralization capacity of approximately 85.08 cmol / kg, and a carbonate content of approximately 9.01 g / kg at the end of 90 days of composting. Compared to Example 1, the decomposition products obtained in Comparative Example 1 had lower acid neutralization capacity and carbonate content, indicating that nano-Fe3O4 treatment is beneficial for obtaining organic fertilizer with higher acid neutralization capacity.

[0060] Experimental Example 1: Verification of Compost Temperature Changes During the composting process of Example 1 and Comparative Example 1, the temperature of the compost pile was monitored using a digital thermometer, and temperature data were recorded daily at 9:00 and 20:00. Example 1 corresponds to nano-Fe3O4 treatment, while Comparative Example 1 corresponds to no treatment.

[0061] The results show that ( Figure 1 Both treatments exhibited a rapid heating process, followed by high-temperature maintenance and then a stable cooling process. The initial temperature of the untreated group was 39.50℃, while the initial temperature of the nano-Fe3O4 treatment was 40.75℃. Both treatments reached their peak temperatures on day 8, with the highest temperature in the untreated group reaching 50.85℃ and the highest temperature in the nano-Fe3O4 treatment reaching 52.15℃. The duration of temperatures above 45℃ for both treatments was 9 days. In the later stages of composting, the temperatures of both treatments gradually decreased and tended to stabilize.

[0062] The above results show that after adding nano-Fe3O4 according to the method of the present invention, the composting system can still maintain the normal aerobic composting temperature succession process and will not weaken the ability to maintain the high temperature stage.

[0063] Experimental Example 2: Verification of pH, acid neutralization capacity and carbonate content of compost products Air-dried samples obtained at different composting stages from Example 1 and Comparative Example 1 were used to determine pH, acid neutralization capacity, and carbonate content.

[0064] pH measurement results showed that ( Figure 2 The initial pH of the untreated group was 8.40, while the initial pH of the nano-Fe3O4 treated group was approximately 8.62. During the early stages of composting, the pH of both treatments increased; by day 30, the pH of both treatments was approximately 8.90. At the end of 90 days of composting, the pH of the untreated group decreased to approximately 8.80, while the pH of the nano-Fe3O4 treated group increased to approximately 8.98.

[0065] The results of the acid neutralization capacity determination showed that ( Figure 3 The initial acid neutralization capacity without treatment was 60.04 cmol / kg, and the initial acid neutralization capacity with nano-Fe3O4 treatment was 63.46 cmol / kg. By day 30, the acid neutralization capacities of the untreated and nano-Fe3O4-treated groups reached 83.54 cmol / kg and 85.98 cmol / kg, respectively. By day 90, the acid neutralization capacity of the untreated group was 85.08 cmol / kg, and the acid neutralization capacity of the nano-Fe3O4-treated group was 97.21 cmol / kg, an increase of 14.3%.

[0066] The results of the carbonate content determination showed that ( Figure 4The initial carbonate content was 6.93 g / kg for the untreated sample and 6.33 g / kg for the nano-Fe3O4-treated sample. By day 30, the carbonate contents were 7.86 g / kg for the untreated sample and 10.93 g / kg for the nano-Fe3O4-treated sample. By day 90, the carbonate content was 9.01 g / kg for the untreated sample and 13.18 g / kg for the nano-Fe3O4-treated sample, an increase of 46.3%.

[0067] Table 1 Comparison of key indicators at the end of composting

[0068] Depend on Figures 1 to 4 As shown in Table 1, the organic fertilizer prepared by the method of the present invention has a high acid neutralization capacity and a high carbonate content at the end of composting, which meets the requirements for the use of organic fertilizer with improved acid neutralization capacity.

[0069] Experimental Example 3: Verification of Functional Group Characteristics of Corrosion Products The 90-day decomposition products obtained in Example 1 and Comparative Example 1 were air-dried, ground, and passed through a 100-mesh sieve. Fourier transform infrared spectroscopy analysis was performed using the potassium bromide pellet method. Recordings were taken at 1080 cm⁻¹. -1 1640cm -1 2920cm -1 and 3430cm -1 The characteristic peak area at [location]. The results are shown in Table 2 below. Figure 5 As shown.

[0070] Table 2 Comparison of characteristic peak areas of organic fertilizers

[0071] Table 2 shows that, compared with the untreated product, the decomposition products treated with nano-Fe3O4 at 1080 cm⁻¹... -1 1640cm -1 2920cm -1 and 3430cm -1 The peak areas at these locations are all higher. These results indicate that the decomposition products prepared using the method of this invention possess richer signals related to hydroxyl groups, aliphatic structures, and oxygen-containing functional groups, corresponding to their higher acid neutralization capacity.

[0072] Experiment Example 4: Verification of the effect of acid soil improvement An acidic soil incubation experiment was conducted to verify the acidic soil improvement capacity of the organic fertilizer obtained in Example 1. Three treatment groups were set up: a soil control treatment only, a treatment with the decomposition products obtained in Comparative Example 1, and a treatment with the decomposition products obtained in Example 1. Each treatment was configured with three independent replicates.

[0073] Weigh 500g of air-dried, sieved acidic soil into a 1L plastic cup. The initial pH of the soil is approximately 4.7. First, adjust the soil moisture content to 40% of field capacity, mix thoroughly, and then seal the cup with plastic wrap. Make three small holes evenly spaced in the plastic wrap to allow for gas exchange and reduce moisture loss. Place all soil samples in a 25℃ constant temperature incubator and pre-culture in the dark for 7 days to stabilize soil microbial activity and respiration levels.

[0074] After pre-cultivation, different decomposition products were added to plastic cups of the corresponding treatments according to the isocarbon addition method of 4.0 g / kg dry soil. During application, the decomposition products were first pre-mixed with a small amount of soil, and then thoroughly mixed with all the soil in the cup to ensure uniform distribution of the decomposition products in the soil. After mixing, deionized water was added to adjust the soil moisture content to 60% of field capacity, and then thoroughly mixed again. The cups were then sealed with perforated plastic wrap and placed in a 25℃ constant temperature incubator for 45 days in the dark. During cultivation, the soil was weighed every 3 days, and deionized water was added to restore the initial weight to maintain a relatively constant soil moisture content. Samples were taken on days 0, 1, 3, 7, 14, 21, 30, and 45 of cultivation to determine soil pH, acid neutralization capacity, organic matter, and soluble organic carbon content.

[0075] The culture results showed that ( Figure 6 A) The soil pH in the control treatment decreased from an initial 4.75 to 4.49 on day 45, a decrease of 0.26 units; the soil pH in the treatment with Comparative Example 1 decomposition products decreased from 4.99 to 4.82, a decrease of 0.17 units; and the soil pH in the treatment with Example 1 decomposition products decreased from approximately 4.98 to 4.89, a decrease of 0.09 units. At the end of the incubation period, the pH in the Example 1 decomposition product treatment was 0.44 pH units higher than the soil control treatment alone and approximately 0.07 pH units higher than the Comparative Example 1 decomposition product treatment, indicating that the application of Example 1 decomposition products was more beneficial in improving the soil's resistance to acidification.

[0076] The results of the acid neutralization capacity determination showed that ( Figure 6 (B) On day 1 of incubation, the acid neutralization capacities of the soil control treatment, the treatment with the decomposition product of Comparative Example 1, and the treatment with the decomposition product of Example 1 were 4.19 cmol / kg, 4.43 cmol / kg, and 4.33 cmol / kg, respectively. After 45 days of incubation, the acid neutralization capacities of the soil control treatment and the treatment with the decomposition product of Comparative Example 1 decreased to 3.35 cmol / kg and 3.65 cmol / kg, respectively, while the acid neutralization capacity of the treatment with the decomposition product of Example 1 was 4.38 cmol / kg, which was 30.7% higher than that of the soil control treatment and 20.0% higher than that of the treatment with the decomposition product of Comparative Example 1. This also indicates that applying the decomposition product of Example 1 is more beneficial to improving the soil's resistance to acidification.

[0077] The results of organic matter determination showed that ( Figure 6 (C) On day 1 of incubation, the organic matter content of the soil control treatment, the treatment with decomposition products of Comparative Example 1, and the treatment with decomposition products of Example 1 were 15.18 g / kg, 18.06 g / kg, and 18.54 g / kg, respectively. After 45 days of incubation, the organic matter content of the soil control treatment and the treatment with decomposition products of Comparative Example 1 decreased to 14.26 g / kg and 16.96 g / kg, respectively, while the organic matter content of the treatment with decomposition products of Example 1 increased to 19.19 g / kg, which was 34.6% and 13.1% higher than the control and Comparative Example 1 treatments, respectively. This indicates that applying the decomposition products of Example 1 is more beneficial to improving the soil's organic carbon sequestration capacity.

[0078] The results of the soluble organic carbon determination showed that ( Figure 6 (D) The soluble organic carbon content on day 1 of the soil control treatment, the treatment with the decomposition product of Comparative Example 1, and the treatment with the decomposition product of Example 1 were 52.98 mg / kg, 67.69 mg / kg, and 68.65 mg / kg, respectively. After 45 days of cultivation, the soluble organic carbon content in the soil control treatment decreased to 47.86 mg / kg, while the content in the treatment with the decomposition product of Comparative Example 1 increased to 71.95 mg / kg, an increase of only 6.29% compared to day 1. However, the soluble organic carbon content in the treatment with the decomposition product of Example 1 increased to 77.76 mg / kg, an increase of 13.3% compared to day 1, indicating that the application of the decomposition product of Example 1 was more beneficial in improving soil organic carbon activity.

[0079] Table 3. Changes in key indicators on day 1 and day 45 of acidic soil incubation.

[0080] As shown in Table 3, when the organic fertilizer prepared by the method of the present invention is applied to acidic soil, the soil pH can be maintained at a high level at the end of the cultivation, and the soil acid neutralization capacity, organic matter and water-soluble organic carbon can be improved and maintained for a long time. This indicates that the obtained organic fertilizer has a stronger effect on stabilizing soil organic matter and acid neutralization capacity, and has a better effect on soil acid control.

[0081] For large-scale preparation, the raw material ratios, moisture content, nano-Fe3O4 addition amount, and fermentation regime in Example 1 can be scaled up proportionally according to compost batch scale. Specifically, the moisture content, total carbon, and total nitrogen content of livestock and poultry manure and crop straw are first tested, and then the amount of straw to be added is calculated according to the target carbon-nitrogen ratio of 25-32. After the materials are mixed evenly in a mixer, 1%-3% of effective microbial compound inoculant is added, and the moisture content is adjusted to 60%-70%. Subsequently, 100-500 mg / kg of dry matter nano-Fe3O4 is added, and uniform dispersion is achieved using a two-stage premixing method.

[0082] Large-scale composting can be carried out using fermentation tanks, fermentation vessels, or windrow composting equipment with ventilation structures. Regardless of the equipment used, it is essential to ensure that the composting system is in an aerobic state and that the turning schedule is matched to changes in material temperature. Preferably, a high turning frequency is maintained in the initial stage of composting, the turning frequency is appropriately reduced in the middle stage, and turning is stopped in the later stage, entering a static maturation phase. After composting, the compost is air-dried, sieved, and tested to obtain an organic fertilizer product with improved acid neutralization capacity.

[0083] In summary, this invention, by adding nano-Fe3O4 to an aerobic composting system of cow manure and straw, and by adjusting the carbon-nitrogen ratio, moisture content, microbial agent dosage, fermentation temperature, water replenishment schedule, turning schedule, and post-ripening treatment, enables the compost product to possess high acid neutralization capacity, high carbonate content, and strong acid soil buffering capacity. This method has clear operational steps, uses widely available raw materials, and can be integrated with conventional livestock and poultry manure and straw resource utilization composting processes, making it suitable for preparing functional organic fertilizers for acid soil improvement.

Claims

1. A method for enhancing the acid neutralization capacity of organic fertilizer, characterized in that, Includes the following steps: Animal manure, crop straw and compound microbial agents are mixed and the carbon-nitrogen ratio of the mixture is adjusted to 25-32 and the moisture content is 60%-70% to obtain premixed compost material. Based on the dry matter mass of the premixed compost material, 100-500 mg / kg of nano Fe3O4 dry matter is added to the premixed compost material and mixed evenly to obtain iron-containing compost material. The iron-containing compost material is placed in a composting container with a gas exchange structure and composted under aerobic conditions. Water is added and the compost is turned during the composting process to obtain decomposed material. The decomposed material is subjected to post-fermentation, air drying and sieving to obtain organic fertilizer with enhanced acid neutralization capacity.

2. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 1, characterized in that, The livestock and poultry manure is fresh cow manure, and the crop straw is wheat straw. The amount of wheat straw added is determined according to the target carbon-nitrogen ratio after the fresh cow manure and the wheat straw are mixed.

3. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 1, characterized in that, The premixed compost material has a carbon-to-nitrogen ratio of 27-29 and a moisture content of 63%-67%.

4. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 1, characterized in that, The compound microbial agent is an effective compound microbial agent, and the amount of the compound microbial agent added is 1% to 3% based on the total wet basis mass of livestock and poultry manure and crop straw.

5. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 4, characterized in that, The amount of the compound microbial agent added is 2% based on the total wet weight of livestock and poultry manure and crop straw.

6. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 1, characterized in that, The amount of nano-Fe3O4 added is 150-300 mg / kg dry matter.

7. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 6, characterized in that, The amount of nano-Fe3O4 added is 200 mg / kg dry matter, and the nano-Fe3O4 is first premixed with a portion of the premixed compost material, and then mixed with the remaining premixed compost material.

8. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 1, characterized in that, The composting container includes a fermentation tank, a breathable material carrier bag placed inside the fermentation tank, and a perforated cover covering the opening of the fermentation tank. The iron-containing compost material is loaded into the breathable material carrier bag and then placed inside the fermentation tank.

9. The method for enhancing the acid neutralization capacity of organic fertilizer according to claim 1, characterized in that, The composting fermentation is carried out at an ambient temperature of 25-35℃, and the total fermentation time is 75-105 days. The compost pile is turned over every 3 days during the first 7 days after the start of the fermentation. From the 7th day to the 45th day of the fermentation, the compost pile is turned over every 7 days. Turning is stopped after the 45th day.

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