Brassica oleracea growth substrate based on construction waste and preparation method thereof

Abstract

The invention discloses a kale growth substrate based on construction waste and a preparation method thereof, and belongs to the technical field of fertilizer synergism. On the basis of preliminarily reducing the salinity and alkalinity of waste concrete and waste brick particles in the substrate, gypsum powder, elemental sulfur and complex microbial inoculant bacteria are adopted to continuously acidify an alkali source in the substrate, so that the content of the alkali source in the substrate is reduced; and residual salt is locked by adopting a nutrient slow-release film, so that the effect of rapidly and persistently reducing alkali and salt of the construction waste particles is realized, and a slightly acidic and low-salt root system environment is provided for the growth of the kale. According to the kale growth substrate based on the construction waste, the pH value is maintained to be 6.2-6.7, the EC value is as low as 1.0 mS.cm <-1 >-1.4 mS.cm <-1 >, the ventilation porosity is larger than or equal to 18%, the water holding porosity is larger than or equal to 45%, total nitrogen is 1.8 g.kg <-1 >-2.2 g.kg <-1 >, available phosphorus is larger than or equal to 35 mg.kg <-1 >, and available potassium is larger than or equal to 250 mg.kg <-1 >.

Description

Technical Field

[0001] This invention relates to the field of plant growth substrate technology, specifically to a kale growth substrate based on construction waste and its preparation method. Background Technology

[0002] Ornamental kale (Brassica oleracea var. acephala) is a biennial foliage plant belonging to the Brassicaceae family and the Brassica genus. Its leaves are purplish-red, creamy-white, or emerald green, and are pinnate, wrinkled, or rosette-shaped. Ornamental kale prefers cool climates and is extremely cold-hardy, tolerating temperatures as low as -10℃ to -15℃. It can withstand multiple short frosts, and its leaves become more vibrant after winter frosts. It can be used in flower beds, borders, potted plants, or eaten fresh for its tender leaves. The ideal soil for planting ornamental kale is loose, fertile, well-draining, and aerated sandy loam, loam, or light clay.

[0003] Commonly used cultivation substrates for kale include peat-based, cassava residue / pine bark substitute, vermicompost, and garden waste substrates. Peat-based substrates, a mixture of peat moss, vermiculite, and perlite, offer advantages such as high porosity and low EC (ecliptic coefficient). However, peat moss is a non-renewable resource, resulting in higher costs. Furthermore, peat moss retains too much water, requiring precise water control during cultivation. Cassava residue / pine bark substitute substrates, a mixture of cassava residue (or pine bark), peat moss, and perlite, utilize waste resources, reducing costs by 30% compared to pure peat moss. This type of substrate has a high organic matter content, resulting in the largest plant crown, the most discolored leaves, and the highest ornamental value. However, it has a high carbon-to-nitrogen ratio, requiring additional nitrogen supplementation in the early stages. If the cassava residue is not thoroughly decomposed, secondary fermentation can lead to root burn. Vermicompost is a mixture of vermicompost, peat moss, and perlite, rich in readily available nutrients and beneficial microorganisms. It can achieve the same yield as pure garden soil and has good buffering properties. However, the source of vermicompost is unstable, and heavy metals and salt content may exceed standards. Garden waste mixture, on the other hand, is a mixture of garden waste, peat moss, and perlite, achieving resource utilization of waste.

[0004] Due to the massive production and stock of construction waste, traditionally 98% is directly landfilled, occupying approximately 300,000 mu (about 20,000 hectares) of land annually, disrupting the soil food chain, and creating permanent environmental risks. Converting construction waste into substrate can provide a large-scale disposal pathway for both existing and new waste, significantly saving landfill land and transportation costs. Traditional substrates rely on non-renewable peat moss, whose price is continuously rising and mining is limited. Bricks, stones, and concrete from construction waste, after crushing and grading, can replace river sand or loam as an inorganic framework. These materials are widely available and have near-zero cost, alleviating reliance on peat moss and reducing substrate prices by 20%–40%, making them particularly economically attractive for projects such as rooftop greening and mine reclamation. However, when bricks and concrete are used as components of the kale growing substrate, the leaching of Ca(OH)₂ and CaSO₄ from waste concrete and bricks leads to a substrate pH of 9–11 and an EC value as high as 4 mS·cm⁻¹. -1~6mS·cm -1 This far exceeds the suitable range for kale (pH value approximately 6.0~6.8, EC value <1.5mS·cm). -1 This leads to the problem of high alkalinity and high salinity in the growth substrate. Summary of the Invention

[0005] This invention provides a kale growth substrate based on construction waste and its preparation method, effectively solving the technical problem that the high salt and alkali content of existing construction waste substrates makes them unsuitable for kale growth. Based on the initial reduction of the salt and alkali content of waste concrete and brick particles in the substrate, this invention uses gypsum powder, elemental sulfur, and compound bacterial agents to continuously acidify the alkaline source inside the substrate. Then, a nutrient slow-release membrane is used to lock in the residual salt. This not only achieves rapid and sustained alkali and salt reduction from construction waste particles but also provides a slightly acidic and low-salt root environment for kale growth.

[0006] The first objective of this invention is to provide a method for preparing a kale growth substrate based on construction waste, comprising the following steps: Using waste concrete and waste brick particles as base materials, wet particles are obtained by alternating leaching with citric acid and sulfuric acid. These wet particles are then mixed with gypsum powder and stacked, followed by spraying with phosphoric acid. The calcium in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0007] Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35℃~40℃. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0008] The compound microbial agent is composed of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1×10⁻⁶. 9 CFU·mL -1 .

[0009] A water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates. Then, decomposed cassava residue compost and nutrient solution are added, stacked and covered with a film, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0010] In a preferred embodiment, the mass concentrations of both citric acid and sulfuric acid are 0.3% to 0.5%, the mass ratio of the substrate to citric acid is 1:1.5 to 2, and the mass ratio of the substrate to sulfuric acid is 1:1.5 to 2. To further reduce the salinity and alkalinity of the substrate surface, the present invention limits the amounts of citric acid and sulfuric acid used as described above, thereby ensuring suitable salinity and alkalinity of the growth substrate.

[0011] As a preferred embodiment, the amount of gypsum powder used is 1 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 ~2kg·m -3 The phosphoric acid has a mass concentration of 2% to 4%, and the amount of phosphoric acid used is 1 kg·m³. -3 ~2kg·m -3 To further reduce the salinity and alkalinity of the base material, the present invention has limited the amounts of gypsum powder and phosphoric acid used as described above, so as to reduce the Ca content in the gypsum powder. 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release yields a premixed matrix. In this step, the calcium in the gypsum powder replaces and removes sodium ions from the surface of the wet particles, further achieving a desalination effect. This invention appropriately matches the amounts of gypsum powder and phosphoric acid, thereby effectively reducing the alkalinity of the matrix without introducing other factors that increase the salinity and alkalinity of the matrix.

[0012] In a preferred embodiment, the amount of the compound microbial agent is 0.8 L·m³, based on the volume of the kale growth substrate based on construction waste. -3 ~1.2L·m -3 The amount of elemental sulfur used is 0.3 kg·m³. -3 ~0.6kg·m -3 Since the thiobacilli in the compound microbial agent use elemental sulfur as an energy source to metabolize and produce acid, thereby further reducing the alkalinity of waste concrete and waste brick particles, the dosage of elemental sulfur and compound microbial agent must be properly matched to ensure the appropriate alkalinity of the substrate.

[0013] In a preferred embodiment, the nutrient solution is composed of a mixture of monoammonium phosphate (20 g / L), potassium sulfate (15 g / L), calcium nitrate (10 g / L), and magnesium sulfate (5 g / L).

[0014] In one preferred embodiment, the nutrient solution is used at a volume of 50 L·m³, based on the volume of the kale growing substrate based on construction waste. -3 ~60L·m -3 .

[0015] As a preferred embodiment, the amount of water-retaining agent used is 80 g / m³, based on the volume of the kale growth substrate based on construction waste. -3 ~120g·m -3 .

[0016] In a preferred embodiment, based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% to 22% of the mass, the waste brick particles account for 13% to 17% of the mass, the decomposed cassava residue compost accounts for 40% to 50% of the mass, and the perlite accounts for 8% to 12% of the mass.

[0017] A second objective of this invention is to provide a kale growth substrate based on construction waste, prepared using any of the preparation methods described above.

[0018] In a preferred embodiment, the kale growth substrate based on construction waste has a pH value of 6.2-6.7 and an EC value of 1.0 mS·cm. -1 ~1.4 mS·cm -1 .

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing a kale growth substrate based on construction waste. Using waste concrete and waste brick particles as base materials, the substrate is sequentially leached with alternating citric acid and sulfuric acid to obtain wet particles. This step of alternating leaching with citric acid and sulfuric acid removes alkaline powder and soluble salts from the surface of the base materials, achieving preliminary alkali and salt reduction. The wet particles are then mixed and stacked with gypsum powder, and then phosphoric acid is sprayed in. The calcium in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - The calcium in the gypsum powder displaces and removes sodium ions from the surface of the wet particles, further reducing salt content. Elemental sulfur is then added to the premixed matrix, along with a compound inoculant of sulfur-containing bacteria and Bacillus. Aerobic fermentation is then carried out at 35°C–40°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+The mixture is hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates. In this step, the sulfur bacteria in the compound microbial agent use elemental sulfur as an energy source to metabolize and produce acid, thereby further reducing the alkalinity of waste concrete and waste brick particles and maintaining the pH of the growth substrate at 6-7. A water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, followed by the addition of well-rotted cassava residue compost and nutrient solution. The mixture is then stacked, covered, and compounded with perlite to obtain a kale growth substrate based on construction waste. In this step, the mucopolysaccharides secreted by Bacillus in the compound microbial agent and the water-retaining agent form a slow-release nutrient film on the particle surface, adsorbing ions such as calcium, magnesium, phosphorus, and potassium needed by plants from the compost and nutrient solution. This not only prevents nutrients from being leached by water but also allows them to be released for absorption by root hairs at any time. This invention, based on the initial reduction of the salinity and alkalinity of waste concrete and waste brick particles in the matrix, uses gypsum powder + elemental sulfur + compound bacterial agent to continuously acidify the alkaline source inside the matrix, and then uses a nutrient slow-release membrane to lock in the residual salt. This not only achieves the effect of rapid and lasting reduction of alkali and salt in construction waste particles, but also provides a slightly acidic and low-salt root environment for the growth of kale.

[0020] The kale growth substrate based on construction waste provided by this invention exhibits structural stability in the Ca-Al-Si complex layer formed by gypsum powder and aluminum hydroxyl and silicon oxide anions on the surface of wet particles. Simultaneously, the generated CaHPO4·2H2O film can persist long-term within the substrate, continuously sealing hydration sites and preventing OH- in the environment of plant roots and microbial secretion of organic acids. - Release, achieving long-term alkali control. The compound microbial agent uses a combination of obligate sulfur-oxidizing bacteria and Bacillus. Their symbiotic system forms a dominant microbial community during aerobic fermentation, which can competitively inhibit the growth of miscellaneous bacteria and is not easily eliminated by other microorganisms. At the same time, elemental sulfur, as an obligate energy substance, can continuously drive the metabolism of sulfur bacteria to produce acid, ensuring that the alkali source inside the substrate is continuously acidified, thereby maintaining a suitable pH range of 6.2 to 6.7 for a long time.

[0021] The kale growth substrate based on construction waste provided by this invention maintains a pH value of 6.2-6.7 and an EC value as low as 1.0 mS·cm. -1 ~1.4 mS·cm -1 Aeration porosity ≥18%, water-holding porosity ≥45%, total nitrogen 1.8 g·kg -1 ~2.2g·kg -1 Available phosphorus ≥ 35 mg·kg -1 Available potassium ≥250mg·kg -1 . Attached Figure Description

[0022] Figure 1 This is a comparison chart of the EC values ​​of the growth substrates in the embodiments, comparative examples, and blank control groups of the present invention.

[0023] Figure 2 This is a comparison chart of the SPAD values ​​of kale grown in the substrates of the embodiments, comparative examples, and blank control groups of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0025] When using bricks and concrete as components of the existing kale growing substrate, the leaching of Ca(OH)2 and CaSO4 from waste concrete and bricks leads to a substrate pH of 9-11 and an EC value as high as 4-6 mS·cm. -1 This far exceeds the suitable range for kale (pH value approximately 6.0~6.8, EC value <1.5mS·cm). -1 This leads to the problem of high alkalinity and salinity in the growth substrate. The present invention provides a kale growth substrate based on construction waste and its preparation method.

[0026] The technical solution of the present invention will be described in detail below.

[0027] This invention provides a method for preparing a kale growth substrate based on construction waste, comprising the following steps: Using waste concrete and waste brick particles as base materials, wet particles are obtained by alternating leaching with citric acid and sulfuric acid. These wet particles are then mixed with gypsum powder and stacked, followed by spraying with phosphoric acid. The calcium in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0028] Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35℃~40℃. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0029] The compound microbial agent is composed of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1×10⁻⁶. 9 CFU·mL-1 .

[0030] A water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates. Then, decomposed cassava residue compost and nutrient solution are added, stacked and covered with a film, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0031] In the above technical solution, after initially reducing the salinity and alkalinity of waste concrete and brick particles in the substrate by alternating leaching with citric acid and sulfuric acid, gypsum powder, elemental sulfur, and compound bacterial agents are used to continuously acidify the alkaline source inside the substrate. Then, a nutrient slow-release membrane is used to lock in the residual salts. This not only achieves rapid and sustained reduction of alkali and salt in construction waste particles but also provides a slightly acidic and low-salt root environment for kale growth. The pH value of the construction waste-based kale growth substrate provided by this invention is maintained at 6.2-6.7, and the EC value is as low as 1.0 mS·cm. -1 ~1.4 mS·cm -1 Aeration porosity ≥18%, water-holding porosity ≥45%, total nitrogen 1.8 g·kg -1 ~2.2g·kg -1 Available phosphorus ≥ 35 mg·kg -1 Available potassium ≥250mg·kg -1 .

[0032] The invention will now be described in detail through the following embodiments and comparative examples.

[0033] In subsequent embodiments of the present invention, the particle size of the waste concrete and waste brick particles used is 0.5mm~4mm, and the decomposed cassava residue fertilizer is purchased from Shandong Linqu Huamao Feed Co., Ltd.; the sulfur-oxidizing thiobacillus is purchased from Wuhan Huarna Biotechnology Co., Ltd., the ferrooxidizing thiobacillus is purchased from Beijing Bio-Biotech Co., Ltd., the Bacillus subtilis is purchased from Shandong Pulan Bioengineering Co., Ltd., the mucilage spores are purchased from Jinan Jinyuyuan Biotechnology Co., Ltd., and the megaterium is purchased from Hubei Xinghengye Technology Co., Ltd.

[0034] Example 1 A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:1.5 and the mass ratio of the base material to sulfuric acid 1:2, alternately leaching with citric acid and sulfuric acid, both with a mass concentration of 0.3%, to obtain wet particles; the wet particles are mixed with gypsum powder and stacked, then phosphoric acid is sprayed in, and the Ca in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2-A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0035] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0036] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥2.1 × 10⁻⁶. 9 CFU·mL -1 .

[0037] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0038] The amount of gypsum powder used is 1 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1 kg·m³. -3 The dosage of the compound microbial agent is 1.2 L·m -3 The amount of elemental sulfur used is 0.5 kg·m³. -3 The amount of nutrient solution used is 52 L·m -3 The dosage of the water-retaining agent is 100 g·m³. -3 .

[0039] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% of the mass, the waste brick particles account for 17% of the mass, the decomposed cassava residue compost accounts for 42% of the mass, and the perlite accounts for 10% of the mass.

[0040] Example 2 A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:2 and the mass ratio of the base material to sulfuric acid 1:1.5, alternately leaching with citric acid and sulfuric acid, both with a mass concentration of 0.5%, to obtain wet particles; the wet particles are mixed with gypsum powder and stacked, then phosphoric acid is sprayed in, and the Ca in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0041] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 40°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0042] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1.8 × 10⁻⁶. 9 CFU·mL -1 .

[0043] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0044] The amount of gypsum powder used is 2 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 2 kg·m³. -3 The dosage of the compound microbial agent is 0.8 L·m -3 The amount of elemental sulfur used is 0.3 kg·m³. -3 The amount of nutrient solution used is 60 L·m -3 The dosage of the water-retaining agent is 80 g·m³. -3 .

[0045] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 20% of the mass, the waste brick particles account for 14% of the mass, the decomposed cassava residue compost accounts for 50% of the mass, and the perlite accounts for 8% of the mass.

[0046] Example 3 A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:1.8 and the mass ratio of the base material to sulfuric acid 1:2, alternately leaching with citric acid and sulfuric acid, both with a mass concentration of 0.4%, to obtain wet particles; the wet particles are mixed and stacked with gypsum powder, and then phosphoric acid is sprayed in, reducing the Ca in the gypsum powder. 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0047] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 38°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0048] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1.5 × 10⁻⁶. 9 CFU·mL -1 .

[0049] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0050] The amount of gypsum powder used is 1.5 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1.2 kg·m³. -3 The dosage of the compound microbial agent is 1.0 L·m -3The amount of elemental sulfur used is 0.4 kg·m³. -3 The amount of nutrient solution used is 50 L·m -3 The dosage of the water-retaining agent is 120 g·m³. -3 .

[0051] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 22% of the mass, the waste brick particles account for 13% of the mass, the decomposed cassava residue compost accounts for 40% of the mass, and the perlite accounts for 12% of the mass.

[0052] Example 4 A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:2 and the mass ratio of the base material to sulfuric acid 1:1.7, alternately leaching with citric acid and sulfuric acid, both with a mass concentration of 0.5%, to obtain wet particles; the wet particles are mixed with gypsum powder and stacked, then phosphoric acid is sprayed in, and the Ca in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0053] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 36°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0054] The compound microbial agent is composed of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1×10⁻⁶. 9 CFU·mL -1 .

[0055] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0056] The amount of gypsum powder used, based on the volume of the kale growth substrate based on construction waste, is 1.3 kg·m³. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1.8 kg·m³. -3 The dosage of the compound microbial agent is 0.8 L·m -3 The amount of elemental sulfur used is 0.6 kg·m³. -3 The amount of nutrient solution used is 54 L·m -3 The dosage of the water-retaining agent is 90 g·m³. -3 .

[0057] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 19% of the mass, the waste brick particles account for 16% of the mass, the decomposed cassava residue compost accounts for 46% of the mass, and the perlite accounts for 11% of the mass.

[0058] Example 5 A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:1.5 and the mass ratio of the base material to sulfuric acid 1:1.5, the materials are alternately leached with citric acid and sulfuric acid, both with a mass concentration of 0.3%, to obtain wet particles; the wet particles are mixed with gypsum powder and stacked, and then phosphoric acid is sprayed in, reducing the Ca content in the gypsum powder. 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0059] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 40°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0060] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥3.2 × 10⁻⁶. 9 CFU·mL -1 .

[0061] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0062] The amount of gypsum powder used is 1.8 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1.5 kg·m³. -3 The dosage of the compound microbial agent is 1.2 L·m -3 The amount of elemental sulfur used is 0.45 kg·m³. -3 The amount of nutrient solution used is 58 L·m -3 The dosage of the water-retaining agent is 110 g·m³. -3 .

[0063] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 21% of the mass, the waste brick particles account for 15% of the mass, the decomposed cassava residue compost accounts for 44% of the mass, and the perlite accounts for 9% of the mass.

[0064] Example 6 A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:2 and the mass ratio of the base material to sulfuric acid 1:2, the materials are alternately leached with citric acid and sulfuric acid, both with a mass concentration of 0.4%, to obtain wet particles; the wet particles are then mixed with gypsum powder and piled up, and then phosphoric acid is sprayed in, reducing the Ca content in the gypsum powder. 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0065] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0066] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1.2 × 10⁻⁶. 9 CFU·mL -1 .

[0067] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0068] The amount of gypsum powder used is 1.5 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 2 kg·m³. -3 The dosage of the compound microbial agent is 1.0 L·m -3 The amount of elemental sulfur used is 0.3 kg·m³. -3 The amount of nutrient solution used is 56 L·m -3 The dosage of the water-retaining agent is 105 g·m³. -3 .

[0069] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 20% of the mass, the waste brick particles account for 15% of the mass, the decomposed cassava residue compost accounts for 48% of the mass, and the perlite accounts for 10% of the mass.

[0070] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows: Comparative Example 1 The difference from Example 1 is that citric acid rinsing is not used; instead, the base material is rinsed with an equal amount of sulfuric acid and citric acid as in Example 1.

[0071] A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, leaching with 0.3% sulfuric acid at a mass ratio of 1:3.5 to the base materials, yields wet particles; these wet particles are then mixed with gypsum powder and piled up, followed by spraying with phosphoric acid to remove the Ca from the gypsum powder. 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH-- Release to obtain a premixed matrix.

[0072] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0073] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥2.1 × 10⁻⁶. 9 CFU·mL -1 .

[0074] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0075] The amount of gypsum powder used is 1 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1 kg·m³. -3 The dosage of the compound microbial agent is 1.2 L·m -3 The amount of elemental sulfur used is 0.5 kg·m³. -3 The amount of nutrient solution used is 52 L·m -3 The dosage of the water-retaining agent is 100 g·m³. -3 .

[0076] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% of the mass, the waste brick particles account for 17% of the mass, the decomposed cassava residue compost accounts for 42% of the mass, and the perlite accounts for 10% of the mass.

[0077] Comparative Example 2 The difference compared to Example 1 is that the plaster powder is removed.

[0078] A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:1.5 and the mass ratio of the base material to sulfuric acid 1:2, the wet particles are obtained by alternating rinsing with citric acid and sulfuric acid, both with a mass concentration of 0.3%; the wet particles are then stacked and sprayed with phosphoric acid to obtain a premixed matrix.

[0079] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0080] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥2.1 × 10⁻⁶. 9 CFU·mL -1 .

[0081] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0082] The phosphoric acid concentration is 3% by volume of the kale growth substrate based on construction waste, and the amount of phosphoric acid used is 1 kg·m³. -3 The dosage of the compound microbial agent is 1.2 L·m -3 The amount of elemental sulfur used is 0.5 kg·m³. -3 The amount of nutrient solution used is 52 L·m -3 The dosage of the water-retaining agent is 100 g·m³. -3 .

[0083] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% of the mass, the waste brick particles account for 17% of the mass, the decomposed cassava residue compost accounts for 42% of the mass, and the perlite accounts for 10% of the mass.

[0084] Comparative Example 3 The difference compared to Example 1 is that sulfur has been removed.

[0085] A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:1.5 and the mass ratio of the base material to sulfuric acid 1:2, alternately leaching with citric acid and sulfuric acid, both with a mass concentration of 0.3%, to obtain wet particles; the wet particles are mixed with gypsum powder and stacked, then phosphoric acid is sprayed in, and the Ca in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0086] S2, a compound bacterial agent containing sulfur-containing bacteria and Bacillus is sprayed into the premixed matrix, and aerobic fermentation is carried out at 35°C to obtain microaggregates.

[0087] The compound microbial agent consists of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥2.1 × 10⁻⁶. 9 CFU·mL -1 .

[0088] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0089] The amount of gypsum powder used is 1 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1 kg·m³. -3 The dosage of the compound microbial agent is 1.2 L·m -3 The amount of nutrient solution used is 52 L·m -3 The dosage of the water-retaining agent is 100 g·m³. -3 .

[0090] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% of the mass, the waste brick particles account for 17% of the mass, the decomposed cassava residue compost accounts for 42% of the mass, and the perlite accounts for 10% of the mass.

[0091] Comparative Example 4 The difference compared to Example 1 is that the compound bacterial agent contains Thiobacillus ferrooxidans.

[0092] A method for preparing a kale growth substrate based on construction waste includes the following steps: S1, using waste concrete and waste brick particles as base materials, and according to the mass ratio of the base material to citric acid 1:1.5 and the mass ratio of the base material to sulfuric acid 1:2, alternately leaching with citric acid and sulfuric acid, both with a mass concentration of 0.3%, to obtain wet particles; the wet particles are mixed with gypsum powder and stacked, then phosphoric acid is sprayed in, and the Ca in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release to obtain a premixed matrix.

[0093] S2, Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35°C. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It is then hydrolyzed to generate Fe(OH)3 colloid, resulting in micro-aggregates.

[0094] The compound microbial agent consists of 47% *Thiobacillus thiooxidans*, 27% *Bacillus subtilis*, 13% *Bacillus mucilaginosus*, and 13% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥2.0 × 10⁻⁶. 9 CFU·mL -1 .

[0095] S3, a water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates, and then well-rotted cassava residue compost and nutrient solution (a mixture of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate and 5 g / L magnesium sulfate) are added, stacked and covered, and compounded with perlite to obtain a kale growth substrate based on construction waste.

[0096] The amount of gypsum powder used is 1 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 The phosphoric acid has a mass concentration of 3% and the amount of phosphoric acid used is 1 kg·m³. -3 The dosage of the compound microbial agent is 1.2 L·m -3 The amount of elemental sulfur used is 0.5 kg·m³. -3 The amount of nutrient solution used is 52 L·m -3 The dosage of the water-retaining agent is 100 g·m³. -3 .

[0097] Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% of the mass, the waste brick particles account for 17% of the mass, the decomposed cassava residue compost accounts for 42% of the mass, and the perlite accounts for 10% of the mass.

[0098] The kale growth substrate based on construction waste provided in the above embodiments and comparative examples was tested, and the testing process and results are as follows.

[0099] I. Experimental Preparation: Kale variety preparation: The present invention uses “Green Feather” edible kale as the test variety, the variety being “Jingyu Green No. 5”, purchased from the Beijing Academy of Agricultural and Forestry Sciences.

[0100] II. Experimental Design: Kale seedlings of uniform size were collected and 11 experimental groups were set up, designated as Experiment 1, Experiment 2, Experiment 3, Experiment 4, Experiment 5, Experiment 6, Control 1, Control 3, Control 4, and Blank Control Group. Each group had 5 replicates, with 5 plants per replicate, for a total of 25 plants / treatment. Experiment 1 to Experiment 6 used the kale growth substrate based on construction waste from Examples 1 to 6, respectively. Control 1 to Control 4 used the kale growth substrate based on construction waste from Comparative Examples 1 to 4, respectively. The blank control group used only the same amount of waste concrete and waste brick particles as in Example 1. All plants were placed in 15cm x 15cm plastic pots, each filled with 1.5L of the growing medium from each of the above treatment groups. They were cultivated under natural light at 15℃~20℃, 60%~70% humidity, and a photoperiod of 12h / d, with watering twice a week to keep the medium moist but not waterlogged. Before cultivation, seedlings were raised in peat moss substrate. When the seedlings were 8cm~10cm tall and had 4~6 true leaves, they were transplanted to the above treatment groups. Relevant parameters were measured 30 days after transplanting.

[0101] III. Analysis of Experimental Results: As shown in Tables 1 and 2.

[0102] Table 1. Comparison of growth substrate performance between embodiments and comparative examples of the present invention.

[0103] Table 2. Growth of kale in embodiments and comparative examples of the present invention.

[0104] As shown in Table 1, the kale growth substrate based on construction waste provided by this invention initially reduces the salinity of waste concrete and brick particles in the substrate under alternating leaching with citric acid and sulfuric acid. The substrate's internal alkalinity is continuously acidified using gypsum powder, elemental sulfur, and a compound bacterial agent. A slow-release nutrient membrane then locks in the residual salts. This not only achieves rapid and sustained reduction of alkali and salt in the construction waste particles but also provides a slightly acidic and low-salt root environment for kale growth. Adjustments to the composition or preparation method of the growth substrate in Example 1 significantly affected its pH, EC, total nitrogen, available phosphorus, and available potassium values. The reasons are analyzed below: In Comparative Example 1, the step of citric acid rinsing in the preparation of the kale growth substrate based on construction waste was removed. Since the present invention first uses citric acid and sulfuric acid to alternately rinsing the base material of waste concrete and waste brick particles, it can remove alkaline powder and soluble salts from the surface of the base material, thereby achieving the initial effect of reducing alkali and salt. Although sulfuric acid can achieve the effect of reducing salt and alkali to a certain extent after removing the citric acid rinsing step, the present invention achieves the synergistic effect of reducing salt and alkali by alternating citric acid and sulfuric acid rinsing. After removing the citric acid rinsing, although the amount of sulfuric acid used in Comparative Example 1 is the same as the amount of citric acid + sulfuric acid in Example 1, it still cannot achieve the same effect of reducing salt and alkali as Example 1.

[0105] In Comparative Example 2, removing the gypsum powder from the kale growth substrate based on construction waste in Example 1 also significantly affected the properties of the substrate. In this invention, wet particles formed from washed waste concrete and waste brick particles are mixed with gypsum powder and piled up, then phosphoric acid is sprayed in. The Ca in the gypsum powder... 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - The gypsum powder is released to obtain a premixed matrix. In this step, the calcium in the gypsum powder displaces and removes sodium ions from the surface of the wet particles, further achieving a desalination effect. The gypsum powder interacts strongly with both the wet particles and phosphoric acid, and their synergistic effect further reduces the salt and alkali content of the growth matrix. In Comparative Example 2, the gypsum powder was removed, which obviously disrupted the synergistic relationship described above, thus significantly affecting the pH and EC values ​​of the growth matrix.

[0106] In Comparative Examples 3 and 4, sulfur and *Athiobacillus ferrooxidans* were removed from the kale growth substrate based on construction waste in Example 1. Since sulfur and *Athiobacillus ferrooxidans* have a mutually dependent relationship, elemental sulfur and *Athiobacillus ferrooxidans* have a synergistic effect on continuous acidification and salt conversion. The absence of either will affect the salinity and alkalinity of the final growth substrate, thus affecting the various indicators of the growth substrate in Table 1.

[0107] The available phosphorus and readily available potassium in Comparative Examples 1 and 4 decreased significantly, which is related to the lack of colloidal formation (Fe(OH)3) and slow-release membrane structure. Comparative Example 2 had the lowest available phosphorus (22 mg / kg), which verifies the important role of the CaHPO4·2H2O film formed by gypsum powder and phosphoric acid in phosphorus fixation.

[0108] Table 2 shows that using the growth substrate of the present invention to cultivate kale can effectively improve the growth status of kale. All growth indicators in the examples are significantly better than those in the control group, indicating that the growth substrate of the present invention can effectively promote the vegetative growth of kale. Comparative Example 1 (without citric acid leaching) and Comparative Example 2 (without gypsum powder) showed the worst growth, indicating that initial salt and alkali reduction and structural improvement are crucial for root development. Comparative Example 3 (without sulfur) and Comparative Example 4 (without *Thiobacillus ferrooxidans*) showed slightly better growth than Comparative Examples 1 and 2, but not as good as the examples, indicating that continuous acidification still has an important impact on mid-to-late stage growth. The chlorophyll SPAD value of kale is positively correlated with the nitrogen content of leaves, reflecting photosynthetic capacity. The SPAD value of the example group was the highest, indicating sufficient nutrient supply and high absorption efficiency. The blank control group had the lowest value, indicating that high salt and alkali stress inhibits chlorophyll synthesis. Regarding the nitrogen, phosphorus, and potassium content in kale leaves, the nutrient content of the example group was the highest, indicating that the slow-release membrane structure and the activation effect of the microbial agent of the present invention promoted nutrient absorption. Comparative Example 2 showed the lowest phosphorus content in its leaves, confirming the crucial role of gypsum powder in phosphorus fixation. Comparative Examples 1 and 4 had low phosphorus and potassium contents, consistent with the decreasing trend of available phosphorus and potassium in the matrix (see Table 1). The control group had the lowest nutrient content, indicating that untreated construction waste cannot provide effective nutrients.

[0109] In summary, the kale growth substrate based on construction waste provided by this invention utilizes alternating leaching with citric acid and sulfuric acid to effectively remove alkaline powder and soluble salts from the surface of waste concrete and brick particles, thus initially reducing the salinity and alkalinity of the substrate. A complex layer and phosphoric acid film are formed using gypsum powder and phosphoric acid to block OH-. - It releases and fixes phosphorus; it uses elemental sulfur and compound microbial agents to achieve continuous acidification and colloidal aggregation, enhancing salt conversion and slow nutrient release; it uses water-retaining agents, compost and nutrient solution to provide nutrients and form a slow-release system to maintain a low-salt and high-fertilizer environment.

[0110] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a kale growth substrate based on construction waste, characterized in that, Includes the following steps: Using waste concrete and waste brick particles as base materials, wet particles are obtained by alternating rinsing with citric acid and sulfuric acid. The wet granules and gypsum powder are mixed and piled up, and then phosphoric acid is sprayed in. The Ca in the gypsum powder 2+ The aluminum hydroxyl groups and silicon oxide anions on the surface of the wet particles form a Ca-Al-Si complex layer, sealing the hydration sites. Simultaneously, Ca(OH)₂ and PO₃ are formed. 2- A CaHPO4·2H2O film is formed to prevent OH- - Release, and a premixed matrix is ​​obtained; Elemental sulfur is sprinkled into the premixed substrate and a compound inoculant of sulfur-containing bacteria and Bacillus is sprayed in. Aerobic fermentation is carried out at 35℃~40℃. The elemental sulfur oxidizes the ferrous iron in the sulfur-containing bacteria. 2+ Converted to Fe 3+ It also hydrolyzes to generate Fe(OH)3 colloid, yielding micro-aggregates; The compound microbial agent is composed of 35% *Thiobacillus thiooxidans*, 25% *Thiobacillus ferrooxidans*, 20% *Bacillus subtilis*, 10% *Bacillus mucilaginosus*, and 10% *Bacillus megaterium* by weight percentage, and the total viable count of the compound microbial agent is ≥1×10⁻⁶. 9 CFU·mL -1 ; A water-retaining agent is used to form a hydrogel layer on the surface of the micro-aggregates. Then, decomposed cassava residue compost and nutrient solution are added, stacked and covered with a film, and compounded with perlite to obtain a kale growth substrate based on construction waste.

2. The method for preparing a kale growth substrate based on construction waste according to claim 1, characterized in that, The mass concentrations of citric acid and sulfuric acid are both 0.3% to 0.5%, the mass ratio of the base material to citric acid is 1:1.5 to 2, and the mass ratio of the base material to sulfuric acid is 1:1.5 to 2.

3. The method for preparing a kale growth substrate based on construction waste according to claim 1, characterized in that, The amount of gypsum powder used is 1 kg·m³, based on the volume of the kale growth substrate based on construction waste. -3 ~2kg·m -3 The phosphoric acid has a mass concentration of 2% to 4%, and the amount of phosphoric acid used is 1 kg·m³. -3 ~2kg·m -3 .

4. The method for preparing a kale growth substrate based on construction waste according to claim 1, characterized in that, Based on the volume of the kale growth substrate based on construction waste, the dosage of the compound microbial agent is 0.8 L·m³. -3 ~1.2L·m -3 The amount of elemental sulfur used is 0.3 kg·m³. -3 ~0.6kg·m -3 .

5. The method for preparing a kale growth substrate based on construction waste according to claim 1, characterized in that, The nutrient solution is composed of 20 g / L monoammonium phosphate, 15 g / L potassium sulfate, 10 g / L calcium nitrate, and 5 g / L magnesium sulfate.

6. The method for preparing a kale growth substrate based on construction waste according to claim 5, characterized in that, The amount of nutrient solution used is 50 L·m³, based on the volume of the kale growing substrate based on construction waste. -3 ~60L·m -3 .

7. The method for preparing a kale growth substrate based on construction waste according to claim 1, characterized in that, The amount of water-retaining agent used is 80 g / m³, based on the volume of the kale growing substrate based on construction waste. -3 ~120g·m -3 .

8. The method for preparing a kale growth substrate based on construction waste according to claim 1, characterized in that, Based on the mass of the kale growth substrate based on construction waste, the waste concrete accounts for 18% to 22% of the mass, the waste brick particles account for 13% to 17% of the mass, the decomposed cassava residue compost accounts for 40% to 50% of the mass, and the perlite accounts for 8% to 12% of the mass.

9. A kale growth substrate based on construction waste, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The kale growth substrate based on construction waste according to claim 9, characterized in that, The kale growth substrate based on construction waste has a pH of 6.2–6.7 and an EC value of 1.0 mS·cm. -1 ~1.4 mS·cm -1 .

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