A method for preparing a soil amendment, the soil amendment prepared thereby, and methods of application

Abstract

This invention belongs to the field of soil conditioner technology, and relates to a method for preparing a soil conditioner, the resulting soil conditioner, and its application method. The preparation method includes the following steps: mixing brewing sludge and biogas residue with sorghum straw particles to obtain a mixture; adjusting the carbon-to-nitrogen ratio to 20:1 to 40:1; adding an organic material composting agent; aerobic fermentation at 55℃ for ≥15 days; turning and cooling the pile at temperatures >65℃; and fermenting for 15-30 days after cooling to below 50℃ to obtain the soil conditioner. By utilizing the nitrogen source of the biogas residue to neutralize the high-carbon characteristics of the straw, and further enhancing the synergistic decomposition of the two by the organic material composting agent, this invention promotes rapid aerobic fermentation and stable high-temperature fermentation for over 15 days. This ensures harmlessness while avoiding the high-temperature burning of beneficial bacteria in the composting agent and the disruption of the synergistic decomposition of the biogas residue and straw, achieving complementary advantages between the biogas residue and straw, and producing a loose, breathable, nutrient-balanced, and safely composted soil conditioner.

Description

Technical Field

[0001] This invention belongs to the field of soil conditioner technology, and relates to a method for preparing a soil conditioner, the resulting soil conditioner, and its application method. Background Technology

[0002] The production of baijiu (Chinese liquor) involves multiple steps including steaming, fermentation, and distillation, generating a large amount of wastewater. This wastewater contains abundant organic matter such as starch, protein, and sugars. After treatment by a wastewater treatment system, it produces a large amount of brewing sludge. Statistics show that brewing sludge production accounts for approximately 3% of the wastewater treatment volume. After plate and frame dehydration, its moisture content can reach 70%, resulting in a huge annual production volume. Its proper disposal has become a critical environmental issue for sustainable development. Analysis shows that all risk indicators of brewing sludge are better than the Class A standard requirements of the "Pollutant Control Standard for Agricultural Sludge" (GB4284-2018). Its organic matter content reaches 68%, and it is rich in plant nutrients such as nitrogen, phosphorus, and potassium, possessing extremely high resource utilization value. Therefore, promoting the resource utilization of brewing sludge is urgent, and recovering its nutrients through anaerobic digestion and aerobic fermentation is an important way to realize its value.

[0003] Currently, there are four methods for treating brewing sludge: anaerobic digestion, aerobic fermentation, drying and incineration, and direct landfill. Among these, direct landfill does not conform to future development trends and can only serve as a temporary, emergency, transitional disposal technology, not a mainstream one. Drying and incineration technology suffers from high energy consumption, high investment and operational requirements, and the potential to cause secondary environmental pollution.

[0004] The anaerobic digestion process of brewing sludge produces brewing sludge biogas residue, which not only retains the rich organic matter and nutrient content of the raw materials but also achieves partial stabilization and harmlessness during digestion. Its pathogen content is significantly reduced, and its biological safety is improved. These characteristics make brewing sludge biogas residue particularly suitable for land application, creating favorable conditions for the development of high-value soil conditioner products.

[0005] However, brewing sludge and biogas residue have a dense structure, poor air permeability, and low porosity. Direct application can easily cause soil compaction, poor aeration and water permeability, which is not conducive to crop root respiration and growth. Moreover, brewing sludge and biogas residue have a low carbon-nitrogen ratio, a fast degradation rate, and uneven nutrient release. Long-term application can easily lead to soil fertility decline and crop growth restriction. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a soil conditioner, as well as the method for applying the prepared soil conditioner. By utilizing the nitrogen source of biogas residue to neutralize the high carbon content of straw, and using an organic material composting agent to further enhance the synergistic decomposition of the two, the invention promotes rapid initiation and high-temperature stability of aerobic fermentation. During fermentation, the temperature is maintained above 55°C for ≥15 days. If the temperature exceeds 65°C, the compost pile is turned over in time. This ensures harmlessness and avoids the high temperature killing of beneficial bacteria in the composting agent and destroying the synergistic decomposition of biogas residue and straw. It achieves the complementary advantages of biogas residue and straw, resulting in a loose, breathable, nutrient-balanced, and safe composting soil conditioner.

[0007] In a first aspect, the present invention provides a method for preparing a soil conditioner, comprising the following steps: Fermentation pretreatment: The brewing sludge and biogas residue are mixed with sorghum straw particles to obtain a mixture. The mass ratio of the brewing sludge and biogas residue to the sorghum straw particles is 1:1.5~3. The carbon-nitrogen ratio of the mixture is adjusted to 20:1~40:1. An organic material composting agent is added to the mixture. Temperature-controlled fermentation: Aerobic fermentation in windrows is adopted, maintaining a fermentation time of ≥15 days above 55℃. When the temperature is >65℃, the pile is turned over immediately to cool down. Composting termination: After the temperature stabilizes and drops below 50℃, continue fermentation for 15-30 days to obtain the soil conditioner.

[0008] In some implementations, the sorghum straw particles have a particle size ≤5cm and a carbon-to-nitrogen ratio of 60:1 to 75:1.

[0009] In some implementation schemes, the mass ratio of the brewing sludge / biogas residue to sorghum straw is 1:1.5~2.5.

[0010] In some implementation schemes, the brewing sludge residue is the solid residue after anaerobic digestion and dehydration of brewing sludge, and the brewing sludge residue has a moisture content of 60% to 70% and an organic matter content of ≥40%.

[0011] In some embodiments, the amount of organic material composting agent added is 0.005 to 0.015% of the mass of the mixture.

[0012] In some implementations, the height of the windrow compost pile is 1 to 1.5 m and the width is 1.5 to 2 m.

[0013] Secondly, the present invention provides a soil conditioner prepared by any of the methods described above, wherein the seed germination index of the soil conditioner is ≥100%, and the heavy metal and pathogen indicators meet agricultural safety standards.

[0014] In some embodiments, the soil conditioner has a total nutrient content ≥40 mg / g, whereby the total nutrients include the sum of N, P2O5, and K2O, and the soil conditioner has a bulk density ≤1.2 g / cm³. 3 It has no plant toxicity.

[0015] Thirdly, the present invention provides a method for applying the above-mentioned soil conditioner, comprising: Soil improvement: Before planting, deeply till the soil to a depth of 0-30cm, and mix the soil conditioner evenly with the soil. The volume percentage of the soil conditioner should be 25-75%. Seedling transplanting: Select robust red sorghum seedlings and transplant them with soil attached, with a spacing of 0.8 to 1 foot between holes and 1.5 to 2 feet between rows; Field management: Water when the relative soil moisture content is less than 60% during the jointing, heading, and grain-filling stages, and do not apply chemical fertilizers throughout the entire growth period.

[0016] In some embodiments, the soil pH after improvement with the soil conditioner is 6.9–7.2, and the organic matter content is increased by ≥10%.

[0017] In summary, this application includes at least one of the following beneficial technical effects: After anaerobic digestion, brewing sludge and biogas residue retain abundant organic matter and nutrients such as nitrogen, phosphorus, and potassium. Pathogens are significantly reduced, and the residue remains stable. Sorghum straw has a well-developed fiber skeleton and ample carbon source, which can loosen the compost and improve aeration. The nitrogen source of the biogas residue can neutralize the high carbon content of the straw. The organic material composting agent further enhances the synergistic decomposition of the two, promoting rapid aerobic fermentation and high-temperature stability. Maintaining a high temperature of ≥55℃ for ≥15 days during fermentation, and turning the compost in time when the temperature exceeds 65℃, ensures harmlessness and avoids burning the beneficial bacteria of the composting agent and destroying the synergistic decomposition of biogas residue and straw. This achieves complementary advantages between biogas residue and straw, resulting in a loose, breathable, nutrient-balanced, and safe composting soil conditioner. Attached Figure Description

[0018] Figure 1 This is a seed germination index (GI) graph of the soil conditioner of this invention; Figure 2 This is a graph showing the nitrogen, phosphorus, and potassium nutrient content of the soil conditioner of this invention. Figure 3 The figure shows the effect of different proportions of the soil conditioner of this invention on the dry weight of sorghum. Detailed Implementation

[0019] The following specific embodiments further illustrate the technical solution of the present invention. These specific embodiments do not represent a limitation on the scope of protection of the present invention. Non-essential modifications and adjustments made by others based on the concept of the present invention still fall within the scope of protection of the present invention.

[0020] All reagents and equipment used in this invention are commercially available.

[0021] The brewing sludge digestate of this invention refers to the solid residue obtained after anaerobic digestion of brewing sludge. Because easily degradable organic matter is decomposed and transformed during anaerobic digestion, the digestate has a low organic matter content and is relatively enriched in inert minerals (such as quartz). Compared with undigested sludge, digestate has the following characteristics: low odor, good dewatering properties, strong acid neutralization ability, and stable chemical properties.

[0022] This application provides a method for preparing a soil conditioner, comprising the following steps: Fermentation pretreatment: The brewing sludge and biogas residue are mixed with sorghum straw particles to obtain a mixture. The mass ratio of brewing sludge and biogas residue to sorghum straw particles is 1:1.5~3. The carbon-nitrogen ratio of the mixture is adjusted to 20:1~40:1. An organic material composting agent is added to the mixture. Temperature-controlled fermentation: Aerobic fermentation in windrows is adopted, maintaining a fermentation time of ≥15 days above 55℃. When the temperature is >65℃, the pile is turned over immediately to cool down. Composting termination: After the temperature of the compost pile stabilizes and drops below 50℃, continue fermentation for 15 to 30 days to obtain a soil conditioner.

[0023] After anaerobic digestion, brewing sludge and biogas residue retain rich organic matter and nitrogen, phosphorus, and potassium nutrients, and the pathogens are significantly reduced and the properties are stable, but the structure is dense and the air permeability is poor. Sorghum straw has a well-developed fiber skeleton and sufficient carbon source, which can loosen the pile and improve air permeability, but its carbon-nitrogen ratio is too high, it decomposes slowly on its own and is prone to nitrogen loss. When the two are mixed in a ratio of 1:1.5 to 3, the nitrogen source of the biogas residue can neutralize the high carbon characteristics of the straw, and the carbon-nitrogen ratio of the mixture is precisely adjusted to the suitable fermentation range of 20:1 to 40:1. The organic material composting agent further enhances the synergistic decomposition of the two, promotes rapid start-up of aerobic fermentation and high-temperature stability. Maintaining a high temperature of 55℃ or above for ≥15 days during fermentation can kill residual pathogens in the biogas residue and insect eggs in the straw, ensuring harmlessness. If the temperature exceeds 65℃, turn the pile in time to avoid burning the beneficial bacteria in the composting agent and disrupting the synergistic decomposition of biogas residue and straw. Continue composting at a temperature below 50℃ for another 15-30 days to allow the nutrients in the biogas residue to be fully converted and the straw fibers to be completely decomposed, solving the problem of dense biogas residue and difficult straw decomposition. Ultimately, this achieves the complementary advantages of biogas residue and straw, producing a loose, breathable, nutrient-balanced, and safe composting soil conditioner.

[0024] For example, the mass ratio of brewing sludge and biogas residue to sorghum straw particles can be 1:1.5, 1:2, 1:2.5, 1:3, etc., and the carbon-nitrogen ratio of the mixture can be 20:1, 30:1, 40:1, etc. If the biogas residue ratio is lower than 1:3 or the carbon-nitrogen ratio is higher than 40:1, the straw has an excess of carbon source and insufficient nitrogen, which can easily lead to slow fermentation temperature rise, incomplete decomposition, and the finished product has plant toxicity. If the biogas residue ratio is higher than 1:1.5 or the carbon-nitrogen ratio is lower than 20:1, the biogas residue has a prominent dense characteristic and the straw has insufficient loosening effect, resulting in poor air permeability of the pile, easy anaerobic odor, and nutrient loss.

[0025] If the temperature exceeds 55℃ for less than 15 days, pathogens in the biogas residue will not be completely inactivated, insect eggs in the straw will remain, and the conditioner will have poor safety. If the temperature exceeds 65℃ and the pile is not turned, beneficial bacteria will be inactivated, the co-fermentation of biogas residue and straw will stop, and local carbonization will be easy. If the temperature of the pile stabilizes and drops below 50℃, but fermentation continues for less than 15 days, the straw will not decompose sufficiently, the nutrients in the biogas residue will not be stable, and the conditioner will have plant toxicity. If the fermentation time exceeds 30 days, the maturation time is too long, the organic matter will continue to mineralize, resulting in a decrease in content, and it will also increase operating costs and affect the economics of the product.

[0026] Furthermore, the sorghum straw particles have a diameter of ≤5cm and a carbon-to-nitrogen ratio of 60:1 to 75:1.

[0027] Sorghum straw with a particle size of ≤5cm can be evenly mixed with brewing sludge and biogas residue, forming stable pores during high-temperature fermentation at 55℃. This ensures sufficient contact between the nutrients in the biogas residue and the carbon source in the straw, while also facilitating uniform heat transfer and maintaining a constant temperature in the pile, avoiding local overheating or underheating. Its natural carbon-nitrogen ratio of 60:1 to 75:1 complements that of the biogas residue, meeting the nutritional needs of microorganisms during high-temperature fermentation and accelerating the degradation of straw fibers at high temperatures. Combined with the nitrogen source and composting agent in the biogas residue, this allows for efficient high-temperature fermentation and more thorough composting.

[0028] Furthermore, the mass ratio of brewing sludge and biogas residue to sorghum straw is 1:1.5~2.5.

[0029] Under this ratio, the nutrient supply of biogas residue and the loose framework of straw are optimally balanced. During high-temperature fermentation at 55℃, the nitrogen source of biogas residue continuously supplies microorganisms, while the straw maintains the air permeability of the pile and prevents compaction.

[0030] Furthermore, brewing sludge and biogas residue are solid residues after brewing sludge has undergone anaerobic digestion and dewatering. The moisture content of brewing sludge and biogas residue is 60% to 70%, and the organic matter content is ≥40%.

[0031] Anaerobic digestion effectively kills pathogens, removes odors, and stabilizes organic matter, ensuring that the biogas residue meets harmless standards, is stable, and is easy to store and transport. Organic matter content is a crucial indicator of the carbon source abundance of raw materials. The brewing sludge biogas residue selected in this invention has an organic matter content of ≥40%, providing sufficient carbon source for subsequent composting fermentation and ensuring fermentation efficiency and product fertilizer effectiveness.

[0032] Furthermore, the amount of organic material composting agent added is 0.005~0.015% of the mass of the mixture.

[0033] The organic material composting agent can accelerate the fermentation and composting of raw materials, while also increasing beneficial bacteria in the soil, improving fertilizer efficiency, and inhibiting bacterial diseases.

[0034] Furthermore, the height of the windrow compost pile is 1~1.5m and the width is 1.5~2m.

[0035] The pile size is compatible with conventional ventilation, allowing for rapid heating to 55°C in the early stages of fermentation and maintenance of this high temperature for ≥15 days. When the temperature exceeds 65°C, turning the pile and coordinating with ventilation rapidly lowers the temperature, protecting the activity of beneficial bacteria.

[0036] Furthermore, this application also provides a soil conditioner prepared by any of the methods described above, wherein the seed germination index of the soil conditioner is ≥100%, and the heavy metal and pathogen indicators meet agricultural safety standards.

[0037] By relying on the complementary materials of biogas residue and straw, the synergistic process of composting agent, sterilization at 55℃ for ≥15 days, and composting at 50℃ for 15-30 days, the biogas residue is rendered harmless, the straw is loosened, the composting agent promotes composting and the temperature sterilization composting are superimposed, the conditioner is fully composted and has no plant toxicity, the germination index is ≥100%, and the heavy metals and pathogens meet the standards, thus achieving safe and efficient co-resource utilization of waste.

[0038] Furthermore, the total nutrient content of the soil conditioner is ≥40mg / g, and the total nutrients include the sum of N, P2O5, and K2O. The bulk density of the soil conditioner is ≤1.2g / cm³. 3 It has no plant toxicity.

[0039] Biogas residue provides nutrients, straw loosens structure, and composting agents promote conversion. Combined with high-temperature decomposition at 55℃ and nutrient solidification during the composting period, these three factors work synergistically with the temperature-time process. The total nutrients from the improver are ≥40mg / g, and the bulk density is ≤1.2g / cm³. 3 It combines fertility and loosening properties, and its application improves soil structure and enhances fertility.

[0040] Furthermore, this application also provides a method for applying a soil conditioner, comprising: Soil improvement: Before planting, deeply till the soil to a depth of 0-30cm, and mix the soil conditioner evenly with the soil. The volume percentage of the soil conditioner should be 25-75%. Seedling transplanting: Select robust red sorghum seedlings and transplant them with soil attached, with a spacing of 0.8 to 1 foot between holes and 1.5 to 2 feet between rows; Field management: Water when the relative soil moisture content is less than 60% during the jointing, heading, and grain-filling stages, and do not apply chemical fertilizers throughout the entire growth period.

[0041] Soil conditioner is prepared from biogas residue and straw. It provides long-lasting nutrients and has a loose structure. It is mixed with soil at a volume ratio of 25% to 75%. For example, the volume ratio of soil conditioner can be 25%, 35%, 45%, 50%, 60%, 65%, 70%, 75%, etc. It synergistically improves soil aeration and water retention, enhances fertility, and is suitable for sorghum growth. Under the condition of no need for topdressing, the long-lasting nutrient supply from the conditioner promotes root growth and enhances stress resistance. If the proportion of conditioner is inappropriate, the synergistic improvement with the soil will be unbalanced; if the transplanting parameters are not compatible, the conditioner will not match the improved soil environment, thus affecting sorghum growth.

[0042] Furthermore, the pH of the soil improved by the aforementioned soil conditioner is 6.9–7.2, and the organic matter content increases by ≥10%.

[0043] The synergistic effect of biogas residue pH adjustment, straw organic matter supplementation, and temperature-time process nutrient activation, combined with soil conditioner balancing soil pH and increasing organic matter, promotes the accumulation of sorghum dry matter, achieving a win-win situation of waste resource utilization and increased yield.

[0044] Example 1 A method for preparing a soil conditioner includes the following steps: Step 1, Fermentation Pretreatment: Mix brewing sludge and biogas residue with sorghum straw particles at a mass ratio of 2:3 to obtain a mixture. Adjust the carbon-nitrogen ratio of the mixture to 20:1. Add an organic material composting agent to the mixture at a mass ratio of 0.01% of the mixture. Adjust the moisture content to 60%. Ferment using a windrow aerobic composting method. The windrow dimensions are 1-1.5m high and 1.5-2m wide.

[0045] Brewing sludge digestate is obtained by dewatering brewing sludge after anaerobic digestion. Testing revealed that the digestate has a pH of 7.02, an organic matter (TOM) content of 43.14%, a total nitrogen (TN) content of 29.64 g / kg, a total phosphorus (TP) content of 10.27 g / kg, and a total potassium (TK) content of 6.95 g / kg. It also contains inorganic mineral components such as carbonates, oxides, and clay minerals. Compared to the original sludge, this digestate exhibits significantly reduced odor, excellent dewatering performance, strong acid neutralization capacity, and stable properties, which is beneficial for the stable operation of subsequent composting processes.

[0046] The particle size of sorghum straw pellets is ≤5cm. The basic properties of brewing sludge and biogas residue and sorghum straw pellets are shown in Table 1 below: Table 1. Basic properties of brewing sludge residue and sorghum straw pellets

[0047] The organic material composting agent is a multifunctional compound bio-fertilizer fermentation agent produced by Zhengzhou Haowangnong Biotechnology Co., Ltd. The height of the windrow compost pile is 1-1.5m, and the width is 1.5-2m.

[0048] Step 2, temperature-controlled fermentation: During the fermentation period, the temperature of the upper, middle and lower parts of the pile is measured daily and the average value is taken. The temperature is maintained above 55℃ for ≥15 days. When the pile temperature is higher than 65℃, the pile is turned over to cool down immediately.

[0049] Step 3, Termination of composting: After the temperature of the pile stabilizes and drops below 50℃, continue fermentation for 15 to 30 days until the material turns dark brown, has a loose texture and no odor, then terminate the fermentation to obtain soil conditioner A.

[0050] Example 2 A method for preparing a soil conditioner, based on Example 1, involves adjusting the mass ratio of brewing sludge residue to sorghum straw particles to 4:9 to obtain a mixture. The carbon-nitrogen ratio of the mixture is adjusted to 25:1, and the remaining conditions and steps are the same as in Example 1, to obtain soil conditioner B.

[0051] Comparative Example 1 A method for preparing a soil conditioner, based on Example 1, involves adjusting the mass ratio of brewing sludge residue to sorghum straw particles to 2:7 to obtain a mixture. The carbon-nitrogen ratio of the mixture is then adjusted to 30:1. The remaining conditions and steps are the same as in Example 1, resulting in soil conditioner C.

[0052] Performance Analysis (1) Seed germination index (GI) analysis Soil conditioners A, B, and C were tested for maturity and phytotoxicity. The seed germination index (GI) was used to assess the maturity and biocompatibility of the conditioners. The experimental methods and results are as follows: Seed germination index (GI) is an important indicator for assessing compost maturity and phytotoxicity of compost products. Radish seeds were selected as the experimental material to evaluate the maturity of the finished compost. 10g each of amendments A, B, and C were weighed and added to 100mL of deionized water. The mixture was incubated at 25℃ with shaking for 1 hour, allowed to stand for 0.5 hours, and then filtered through filter paper to collect the supernatant. Ten plump, uniformly sized radish seeds were selected, with three replicates per group. The seeds were evenly spread in petri dishes lined with qualitative filter paper, and 10mL of the corresponding extract was added to each. The dishes were incubated at 25℃ in the dark for 48 hours. Germination rate was recorded, taproot length was measured, and GI values ​​were calculated.

[0053] The results are as follows Figure 1 As shown: In the initial stage of composting, i.e., day 1 of temperature-controlled fermentation, the germination index (GI) values ​​of seeds planted with soil conditioners A, B, and C were all below 70%, indicating significant phytotoxicity. After composting, the GI values ​​of soil conditioners A, B, and C were all above 100%, significantly better than the 70% maturity limit specified in the "Organic Fertilizer" (NY / T525-2021) standard. This indicates that soil conditioners A, B, and C have reached a high degree of maturity and have no phytotoxicity.

[0054] (2) Nutrient content analysis To determine the nitrogen, phosphorus, and potassium nutrient contents of soil conditioners A, B, and C and evaluate their nutrient supply capacity, the total nitrogen (TN) content was determined using an organic elemental analyzer. The total phosphorus and total potassium contents were determined by spectrophotometry (as P2O5) and flame photometry, respectively, after treatment with sulfuric acid-hydrogen peroxide digestion.

[0055] The results are as follows Figure 2 As shown: In the initial stage of composting, i.e., day 1 of temperature-controlled fermentation, the total nutrient (N+P2O5+K2O) contents of improvers A, B, and C were 30.40 mg / g, 24.43 mg / g, and 22.35 mg / g, respectively. During composting, the total mass of the compost pile continuously decreased due to the mineralization and decomposition of organic matter, and the increased microbial activity and accelerated enzymatic reactions promoted the relative enrichment of nutrients such as nitrogen, phosphorus, and potassium due to the concentration effect. At the end of composting, the total nutrient (N+P2O5+K2O) contents of improvers A and B were 48.14 and 44.36 mg / g, respectively, which are higher than the minimum limit of 40 mg / g in the organic fertilizer industry standard (NY525—2021). The total nutrient (N+P2O5+K2O) content of improver C was lower, at 38.78 mg / g.

[0056] (3) Safety testing To assess the agricultural safety of soil conditioners and ensure that heavy metals and pathogens meet national standards, a qualified third-party testing agency was commissioned to conduct tests according to the "Standard for Pollutant Control of Agricultural Sludge" (GB4284-2018), including indicators such as total cadmium, total mercury, total lead, total chromium, total arsenic, total nickel, total zinc, total copper, benzo(a)pyrene, and ascarid egg mortality. Because soil conditioner C had a low total nutrient (N+P2O5+K2O) content, failing to meet the minimum limits in the organic fertilizer industry standard (NY525—2021), subsequent safety tests were only conducted on soil conditioners A and B. The results are shown in Table 2. Table 2. Third-party test data and standard limits for compost products

[0057] Note: ND means Not Detected.

[0058] As shown in Table 2, the heavy metal content of soil conditioner A and soil conditioner B is far below the GB4284-2018 Class A limit, the mortality rate of Ascaris eggs reaches 100%, and the benzo(a)pyrene content is only 0.29~0.58 mg / g. The results indicate that the soil conditioner of this invention has low heavy metal content, is hygienic and safe, and can be safely used for agricultural soil improvement.

[0059] (4) Field application effect test of sorghum To verify the soil amendment effect on actual soil and its promoting effect on sorghum growth, a planting experiment was conducted on barren soil in uncultivated wasteland in a certain area of ​​Guizhou Province. The test crop was red tassel sorghum, and the test soil was yellow limestone soil with a gravelly sandy loam texture, a pH of 7.26, an EC conductivity of 203 μs / cm, poor water and fertilizer retention capacity, and low nutrient availability.

[0060] Soil conditioner A and soil conditioner B were thoroughly mixed with the target topsoil layer (0-30cm) at volume ratios of 0% (control), 25%, 50%, and 75%, respectively. During the sorghum seedling stage, robust sorghum seedlings with uniform growth were selected for transplanting using a hole-planting method, with two seedlings per hole, a hole spacing of 0.8-1 foot, and a row spacing of 1.5-2 feet. No other fertilizers or conditioner materials were applied during the planting period. At the sorghum maturity stage, soil and sorghum plant samples were collected for testing. Soil physicochemical indicators and sorghum dry matter mass were measured at maturity. The results of the soil physicochemical indicator tests are shown in Table 3. Table 3 Soil Physicochemical Indicators

[0061] Table 3 shows that, compared with the control (CK), the application of soil conditioners A and B of this invention significantly improved the soil's physical and chemical properties: the soil pH increased from slightly acidic to near neutral, effectively alleviating soil acidification; the contents of soil organic matter, total nitrogen, total potassium, available nitrogen, and available potassium all significantly increased, with the 50% conditioner A treatment and the 75% conditioner B treatment showing the most significant improvement; the soil bulk density increased from 1.28 g / cm³. 3 Reduced to 1.08~1.20 g / cm³ 3 The soil moisture content decreased by 6.3% to 15.6%, and the soil looseness was significantly improved, creating a favorable physical environment for crop root growth. These results demonstrate that the soil conditioner described in this invention can effectively improve soil physicochemical properties and enhance soil fertility.

[0062] The dry matter analysis results of sorghum are as follows: Figure 3 As shown, when soil conditioner A was applied, the total dry matter content of sorghum increased by 86.05%–115.09% compared to the control group (0% application); when soil conditioner B was applied, the increase was 92.44%–102.22%. Furthermore, the promoting effect of soil conditioners on different growth parts of sorghum varied. The effect on the dry matter content of sorghum leaves was relatively small, with an increase of 16.99%–28.12%; while the effect on the dry matter content of stems and ears was relatively large, with increases of 74.30%–133.35%, respectively. These data indicate that biogas residue soil conditioners can effectively promote sorghum growth, especially showing significant improvements in the growth of stems and ears.

[0063] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for preparing a soil conditioner, characterized in that, Includes the following steps: Fermentation pretreatment: The brewing sludge and biogas residue are mixed with sorghum straw particles to obtain a mixture. The mass ratio of the brewing sludge and biogas residue to the sorghum straw particles is 1:1.5~3. The carbon-nitrogen ratio of the mixture is adjusted to 20:1~40:

1. An organic material composting agent is added to the mixture. Temperature-controlled fermentation: Aerobic fermentation in windrows is adopted, maintaining a fermentation time of ≥15 days above 55℃. When the temperature is >65℃, the pile is turned over immediately to cool down. Composting termination: After the temperature stabilizes and drops below 50℃, continue fermentation for 15-30 days to obtain the soil conditioner.

2. The method for preparing the soil conditioner as described in claim 1, characterized in that, The sorghum straw particles have a particle size of ≤5cm and a carbon-nitrogen ratio of 60:1 to 75:

1.

3. The method for preparing the soil conditioner as described in claim 1, characterized in that, The mass ratio of brewing sludge / biogas residue to sorghum straw is 1:1.5~2.

5.

4. The method for preparing the soil conditioner as described in claim 1, characterized in that, The brewing sludge residue is the solid residue after anaerobic digestion and dewatering of brewing sludge. The water content of the brewing sludge residue is 60% to 70%, and the organic matter content is ≥40%.

5. The method for preparing the soil conditioner as described in claim 1, characterized in that, The amount of organic material composting agent added is 0.005~0.015% of the mass of the mixture.

6. The method for preparing the soil conditioner as described in claim 1, characterized in that, The height of the windrow compost pile is 1~1.5m and the width is 1.5~2m.

7. A soil conditioner, characterized in that, Prepared by the method described in any one of claims 1 to 6, the soil conditioner has a seed germination index ≥ 100%, and the heavy metal and pathogen indicators meet agricultural safety standards.

8. The soil conditioner according to claim 7, characterized in that, The soil conditioner has a total nutrient content ≥40 mg / g, where the total nutrients include the sum of N, P2O5, and K2O, and the soil conditioner has a bulk density ≤1.2 g / cm³. 3 It has no plant toxicity.

9. A method for applying the soil conditioner according to claim 7 or 8, characterized in that, include: Soil improvement: Before planting, deeply till the soil to a depth of 0-30cm, and mix the soil conditioner evenly with the soil. The volume percentage of the soil conditioner should be 25-75%. Seedling transplanting: Select robust red sorghum seedlings and transplant them with soil attached, with a spacing of 0.8 to 1 foot between holes and 1.5 to 2 feet between rows; Field management: Water when the relative soil moisture content is less than 60% during the jointing, heading, and grain-filling stages, and do not apply chemical fertilizers throughout the entire growth period.

10. The application method according to claim 9, characterized in that, The soil pH after improvement with the aforementioned soil conditioner is 6.9–7.2, and the organic matter content increases by ≥10%.

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