Blue series hydrangea cultivation substrate based on water plant sludge and preparation and application thereof

Abstract

The present disclosure belongs to the technical field of ecological landscape and waste resource utilization, and particularly relates to a blue series hydrangea cultivation substrate based on water plant sludge and preparation and application thereof. The present disclosure is aimed at the drawbacks of complicated blue adjusting steps, high time node requirements, and difficult-to-grasp blue adjusting degree of hydrangea, and based on the diagnosis of aluminum occurrence characteristics of water plant sludge, the blue adjusting steps of hydrangea are simplified through the adaptation of acidic peat and other materials and the regulation of main control indexes, the main control indexes such as pH, aluminum content and available phosphorus of hydrangea cultivation substrate are established, and the accurate regulation of different blue series of hydrangea and the high-value land use of water plant sludge are realized. Meanwhile, a method for cultivating hydrangea based on the blue series hydrangea cultivation substrate is also provided, so as to ensure the long-term stable blue flowering performance of hydrangea.

Description

Technical Field

[0001] This disclosure belongs to the field of ecological landscape and waste resource utilization technology, and specifically relates to a blue hydrangea cultivation substrate based on water plant sludge, its preparation and application. Background Technology

[0002] Hydrangea (Hydrangea macrophylla) is an important potted flower and cut flower both domestically and internationally. In my country, its cultivation has reached tens of millions of pots, and it is widely planted in parks, green spaces, courtyards, and balconies. Hydrangeas come in a variety of colors, with blue being the most valued for its ornamental qualities. The blue hue of hydrangeas, besides being influenced by varietal factors, is mainly regulated by soil pH and aluminum ion content: under acidic conditions, delphinidin in anthocyanins combines with aluminum ions to form a blue complex; under alkaline conditions, aluminum loses its activity, resulting in a red flower color. The intensity of hydrangea blue can be categorized into three levels: light blue, standard blue, and deep blue, corresponding to different soil pH and aluminum ion concentrations.

[0003] Hydrangeas thrive in fertile soil but dislike waterlogging. Natural soil is heavy and poorly drained, so soilless substrates made of acidic peat moss, perlite, coconut coir, and organic fertilizer are commonly used in horticulture. However, acidic peat moss and other organic materials have low aluminum content, which is difficult for hydrangeas to absorb. To cultivate blue hydrangeas, specialized blue-inducing treatments are required. Traditional blue-inducing methods involve regularly watering with aluminum salts and adjusting the acidity from the time flower buds emerge in spring until the buds show color. This process is cumbersome, and the degree of blue induction is difficult to control precisely. Commonly used aluminum sulfate can burn leaves, and imported slow-release blue-inducing agents are expensive, limiting their widespread adoption. Hydrangeas are fertilizer-loving plants that require nutrients such as phosphorus. However, excessively high levels of available phosphorus can easily fix aluminum, forming aluminum phosphate precipitates, significantly reducing the content of active aluminum and causing blue-inducing failure. Therefore, strictly controlling the available phosphorus content is crucial for cultivating blue hydrangeas, especially deep blue ones.

[0004] While natural soils have high aluminum content (5%–11%, w / w), the vast majority is in the form of crystalline mineral aluminum, which is difficult for plants to utilize, with very low levels of active aluminum. Although the levels of exchangeable and soluble aluminum are elevated in acidic red soils in southern China, easily leading to aluminum poisoning in common plants, this is insufficient to meet the active aluminum requirements of hydrangea blue foliage. Water treatment plants use aluminum sulfate as a flocculant during purification processes, resulting in sludge with an aluminum content as high as 15%–40% (w / w), 3–8 times that of natural soils. Aluminum toxicity is considered a major obstacle to the land use of water treatment plant sludge.

[0005] Currently, the following technical gaps exist in the cultivation of hydrangea blue-toning hydrangeas: Firstly, existing hydroponic hydrangea cultivation substrates lack effective aluminum sources, and conventional blueing treatment relies on external irrigation with aluminum salts. There are no reports of substrate products that utilize aluminum-rich water plant sludge as a substrate component and rely on the aluminum content of the water plant sludge itself to achieve integrated hydrangea cultivation and basic blueing treatment. Secondly, regarding the release rate of aluminum ions in the aforementioned aluminum-containing matrix and the mitigation of aluminum phosphate precipitation, achieving precise guided cultivation of flower color from light blue to dark blue, no technical solution for effective phosphorus regulation of hydrangea matrix has been disclosed in the existing technology.

[0006] Third, existing hydrangea blue-tuning techniques are mostly based on experience and lack quantitative evaluation indicators for cultivation substrates, making it difficult to accurately control the blue color of hydrangeas. Summary of the Invention

[0007] The objective of this disclosure is achieved through the following technical solution: In a first aspect, this disclosure provides a blue hydrangea cultivation substrate based on water plant sludge, comprising the following components by volume: 0-1 part organic fertilizer; 1 to 1.5 parts perlite; 3-4 parts acidic peat; 0-2 parts decomposed coconut chunks; 0-2 parts decomposed pine bark and pine needles; 1-3 parts water plant sludge.

[0008] In some specific embodiments of this disclosure, the water plant sludge is the sludge generated during the purification of tap water using aluminum sulfate as a flocculant. The water plant sludge meets the following requirements: pH less than 7.8, total aluminum (calculated as Al2O3) content greater than 20% (w / w), and hydroxyl-bound aluminum content greater than 8% (w / w).

[0009] In some specific embodiments of this disclosure, the blue hydrangea cultivation substrate also contains a soil conditioner, which is sulfur powder, and the amount of sulfur powder added is 0.4 g to 0.6 g per liter of dry cultivation substrate.

[0010] In some specific embodiments of this disclosure, the blue hydrangea cultivation substrate should meet the following requirements: pH less than 6.5, organic matter content greater than 15% (w / w), aeration porosity greater than 20%, total aluminum (calculated as Al2O3) content greater than 3%, and aluminum hydroxyl content greater than 5% (w / w).

[0011] In some specific embodiments of this disclosure, when the blue hydrangea cultivation substrate is a light blue hydrangea cultivation substrate, it should meet the following requirements: pH between 5.5 and 6.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 3%, and aluminum hydroxyl content greater than 5%.

[0012] In some specific embodiments of this disclosure, the formula of the light blue hydrangea cultivation substrate (by volume) is: organic fertilizer: perlite: acidic peat: decomposed coconut blocks: water plant sludge = (0.5~1): (1~1.5): (3~4): (1~2): (1~3).

[0013] In some specific embodiments of this disclosure, when the blue hydrangea cultivation substrate is a standard blue hydrangea cultivation substrate, it should meet the following requirements: pH between 5.0 and 5.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 4% (w / w) and hydroxyl aluminum ratio greater than 8% (w / w), and available phosphorus content less than 30 mg / kg.

[0014] In some specific embodiments of this disclosure, the standard blue hydrangea cultivation substrate formula (by volume) is: organic fertilizer: perlite: acidic peat: decomposed pine bark and pine needles: water plant sludge = (0.2~0.5): (1~1.5): (3~4): (1~2): (1.5~3); further, the decomposed pine bark and pine needles include decomposed pine bark and decomposed pine needles, wherein the mass ratio of decomposed pine bark to decomposed pine needles is 1: (0.25~1).

[0015] In some specific embodiments of this disclosure, when the blue hydrangea cultivation substrate is a dark blue hydrangea cultivation substrate, it should meet the following requirements: pH between 4.8 and 5.3, organic matter content greater than 15%, aeration porosity greater than 20%, total aluminum content (calculated as Al2O3) greater than 6% (w / w) and hydroxyaluminum content greater than 10% (w / w), and available phosphorus content less than 18 mg / kg.

[0016] In some specific embodiments of this disclosure, the formula of the deep blue hydrangea cultivation substrate (by volume) is: organic fertilizer: perlite: acidic peat: decomposed pine bark and pine needles: water plant sludge = (0~0.2): (1~1.5): (3~4): (1~2): (2~3); further, the decomposed pine bark and pine needles include decomposed pine bark and decomposed pine needles, wherein the mass ratio of decomposed pine bark to decomposed pine needles is 1: (1~2).

[0017] In a second aspect of this disclosure, a method for preparing the aforementioned blue hydrangea cultivation substrate is provided, comprising the following steps: weighing each raw material component according to the aforementioned defined volume ratio, and adding all components into a mixing device for uniform compounding and mixing to obtain the blue hydrangea cultivation substrate.

[0018] In some embodiments of this disclosure, hydrangeas cultivated in the blue-toned hydrangea cultivation substrate can exhibit a blue flower color without the addition of an additional blue-toned agent, and the color difference ΔE between the petal color and the standard color chart satisfies at least one of the following: Light blue: △E>3; Standard Blue: △E > 3; Dark blue: △E > 3; Wherein, the color difference ΔE is according to ΔE 00The color difference formula is the color difference value measured under a D65 light source and a 10° field of view.

[0019] In a third aspect of this disclosure, a method for cultivating hydrangeas using the aforementioned blue hydrangea cultivation substrate is provided, comprising the following steps: During the routine maintenance of the hydrangea, tap water is used for irrigation. However, after budding in spring, light blue hydrangeas can still be irrigated with tap water, but standard blue and dark blue hydrangeas should be irrigated with an acidic irrigation solution instead of tap water. The regular irrigation cycle is 15-20 days, until the flower buds appear, at which point the irrigation with the acidic irrigation solution is stopped. If the petal color uniformity and the depth of blue coloring do not meet the design specifications, the irrigation cycle is adjusted to 10 days. The acidic irrigation solution is naturally collected rainwater or a citric acid solution with a mass volume fraction (w / v) of 0.05%-0.1%. Specifically, a citric acid solution with a mass volume fraction (w / v) of 0.05% is used for standard blue hydrangeas, and a citric acid solution with a mass volume fraction (w / v) of 0.1% is used for dark blue hydrangeas.

[0020] In some embodiments of this disclosure, the step of preparing a corresponding blue-toned hydrangea cultivation substrate according to the target blue color is also included when repotting the hydrangea.

[0021] In a fourth aspect, this disclosure provides the aforementioned blue hydrangea cultivation substrate, its preparation method, and the application of the aforementioned hydrangea cultivation method in the regulation of blue hydrangea flower color.

[0022] The technical solution provided in this disclosure has the following technical contributions: (1) Compared with traditional hydrangea blue-adjusting technology, the present invention is simple in process and easy to operate, and does not require the cumbersome treatment of adding aluminum salts. The developed cultivation substrate can achieve the dual purpose of simple acid adjustment and aluminum supply in one step. While meeting the growth needs of different blue hydrangeas, it expands the land use pathway of waterworks sludge and realizes the high-value resource utilization of waterworks sludge.

[0023] (2) This disclosure clarifies the key indicator requirements of different blue hydrangea cultivation substrates, quantifies the main control parameters such as pH, aluminum content and available phosphorus of hydrangea cultivation substrates, and ensures that the regulation of active aluminum content in the substrate can achieve more precise directional regulation of different blue hydrangea flower colors.

[0024] (3) This disclosure clarifies the raw material requirements and key formulas for preparing different blue hydrangea cultivation substrates from water plant sludge, and provides fine-tuning formulas that can be flexibly adjusted according to the differences in the properties of raw materials. It is highly practical and has good technical guidance value.

[0025] (4) Based on literature review, this disclosure is the first to systematically diagnose the occurrence characteristics of different forms of aluminum in water plant sludge. In view of the shortcomings of existing technologies, such as the fact that most aluminum in natural soil is difficult for plants to absorb, the high content of active aluminum in some acidic soils is still insufficient to meet the blue color of hydrangeas, and the fact that aluminum sulfate irrigation can easily burn leaves or cause aluminum poisoning if the dosage is too high, this invention utilizes the characteristic that the active aluminum in water plant sludge is mainly hydroxyl aluminum and is easy to convert and absorb. By adapting the pH and available phosphorus content of the cultivation substrate, while meeting the phosphorus nutrient requirements of hydrangeas, this invention reduces the fixation of aluminum by phosphorus, and at the same time gradually supplies and converts the hydroxyl aluminum in water plant sludge in a balanced manner. This avoids the risk of aluminum sulfate burning leaves in traditional blue color adjustment methods and ensures the demand for exchangeable aluminum for blue color of hydrangeas. Attached Figure Description

[0026] Figure 1 The hydrangea colors cultivated in the blue hydrangea cultivation substrate of this disclosure are light blue, standard blue, and dark blue from left to right. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to specific embodiments to enable those skilled in the art to understand it. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, all reagents used in the embodiments are commercially available analytical grade, and all experimental methods used are conventional methods.

[0028] The present disclosure is further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present disclosure in any way.

[0029] Example 1: Preparation of blue hydrangea cultivation substrate based on water plant sludge 1. Selection of raw materials for cultivation substrates that meet quality requirements In addition to meeting the requirements of hydrangeas' preference for fertile soil, providing comprehensive nutrients, and meeting the quality requirements of the agricultural industry standard "Organic Fertilizer" (NY / T 525) with a total nutrient content greater than 4%, the organic fertilizer is required to have a pH < 8.2 to control the pH of the substrate. At the same time, to control the available phosphorus content, cow manure with a relatively low available phosphorus content is selected.

[0030] To improve the drainage performance of the substrate, perlite with a large particle size of 5-10 mm should be used; to control the pH, it should be less than 7.5; to control the salt content of the substrate, the perlite should be washed with clean water to ensure that EC is less than 0.2 mS / cm.

[0031] In addition to requiring an organic matter content greater than 50%, acidic peat requires a pH of less than 5.5, preferably between 3.5 and 5.0, because other raw materials have a slightly higher pH, and aluminum is only active under acidic conditions. To simplify the acidification process that needs to be carried out simultaneously during the bluening of hydrangeas, it is recommended that the pH of the acidic peat be between 3.5 and 5.0, and white peat with a low available phosphorus content is preferred.

[0032] To meet the drainage requirements of hydrangeas, the coconut blocks here need to have a large particle size of 10-35 mm and be fully decomposed. To control the salt content of the substrate, it is required to undergo salt washing treatment, with EC < 0.6 mS / cm.

[0033] Pine bark and pine needles should be fully decomposed, with a pH between 4.0 and 5.5. The pH of pine needles should be slightly lower than that of pine bark. Depending on the degree of bluening, the ratio of pine bark to pine needles should be between 1:(0.25~2). The deeper the blue color, the higher the proportion of pine needles.

[0034] The water plant sludge should have a pH less than 7.8, a total aluminum (calculated as Al2O3) content greater than 20% (w / w), and a hydroxyl-bound aluminum content greater than 8% (w / w). The requirement for the water plant sludge to be neutral to slightly acidic is to control the substrate's pH, with pH < 7.5 being ideal. Since hydrangeas have high requirements for cultivation soil, the amount of water plant sludge added should not be too large. At the same time, to ensure the aluminum content required for hydrangea cultivation over many years, the aluminum content (calculated as Al2O3) of the water plant sludge is generally greater than 20% (w / w), which can meet the aluminum source requirements; greater than 30% is preferred. Since the active aluminum in the water plant sludge is mainly hydroxyl aluminum (greater than 80%), and hydroxyl-bound aluminum itself has low toxicity to plants, it avoids direct toxicity to hydrangeas. Furthermore, under acidic conditions, it is easily converted into exchangeable and soluble aluminum that is easily absorbed and utilized by plants, thus becoming a major aluminum source for hydrangeas.

[0035] 2. Prepare a suitable hydrangea cultivation substrate. Based on the various indicators of raw materials and the different blue color requirements of hydrangeas, a suitable pH and aluminum content hydrangea cultivation substrate was prepared. The formula is: organic fertilizer: perlite: acidic peat: decomposed coconut blocks: decomposed pine bark and needles: water plant sludge = (0~1): (1~1.5): (3~4): (0~2): (0~2): (1~3). The cultivation substrate also contains sulfur powder as a soil conditioner. The amount of sulfur powder added is 0.4 g to 0.6 g per liter of dry cultivation substrate, mainly for long-term pH reduction. The specific proportions of each component in the formula can be appropriately adjusted according to the different blue color requirements of hydrangeas and the properties of available raw materials.

[0036] The light blue hydrangea has relatively low requirements for the pH, aluminum content, and available phosphorus of the cultivation substrate. In addition to using acidic peat with a relatively high pH (4.5~5.5) and water plant sludge with a relatively low aluminum content (20~30%, w / w), the relatively expensive pine bark and pine needles can be omitted. There is no mandatory control over the available phosphorus content of organic fertilizer and water plant sludge. The formula can be adjusted to organic fertilizer: perlite: acidic peat: decomposed coconut blocks: water plant sludge = (0.5~1): (1~1.5): (3~4): (1~2): (1~3.0). The cultivation substrate also contains sulfur powder as a soil conditioner, and the amount of sulfur powder added is 0.4 g per liter of dry cultivation substrate.

[0037] The deep blue hydrangea variety has high requirements for the pH, aluminum content, and available phosphorus of the cultivation substrate. It is recommended to use highly acidic (pH 3.5~5.0) and low-phosphorus (available phosphorus less than 20mg / kg) acidic peat, and water plant sludge with high aluminum content (preferably greater than 30%, w / w). It is also recommended to use pine bark and pine needles instead of coconut blocks, increase the amount of water plant sludge, and avoid using organic fertilizer or use a small amount of low-phosphorus organic fertilizer. The specific formula can be adjusted to organic fertilizer: perlite: acidic peat: decomposed pine bark and pine needles: water plant sludge = (0~0.2): (1~1.5): (3~4): (1~2): (2~3), where the mass ratio of decomposed pine bark to decomposed pine needles can be adjusted to 1: (1~2). The cultivation substrate also contains sulfur powder as a soil conditioner, and the amount of sulfur powder added is 0.6 g per liter of dry cultivation substrate.

[0038] The raw material quality requirements and proportions of the standard blue hydrangea cultivation substrate can be adjusted between light and dark color requirements. The formula is: organic fertilizer: perlite: acidic peat: decomposed pine bark and pine needles: water plant sludge = (0.2~0.5): (1~1.5): (3~4): (1~2): (1.5~3). In addition, regarding the characteristics of the available acidic peat and water treatment plant sludge, when the pH of acidic peat is <4.0, the dosage can be reduced to 30% (w / w); when the pH of acidic peat is >4.5, the dosage can be increased to 35-40% (w / w); when the aluminum content of water treatment plant sludge is less than 25% (w / w), the dosage can be increased to 30-40% (w / w); when the aluminum content of water treatment plant sludge is >35% (w / w) or the soluble aluminum content is high, the dosage can be reduced to between 15-25% (w / w); when the available phosphorus content of organic fertilizer is greater than 120 mg / kg, the dosage should be reduced, and for Deep Blue or Standard Blue, organic fertilizer may not even be necessary, and the dosage of acidic peat can be appropriately increased.

[0039] 3. Technical requirements for the cultivation substrate of blue hydrangeas To more accurately achieve the goal of controlling the blue color of hydrangeas, the final general-purpose cultivation substrate for blue hydrangeas should meet the following requirements: pH less than 6.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 3% (w / w) and hydroxyaluminum content greater than 5% (w / w).

[0040] The main control indicators for different blue hydrangea cultivation substrates vary slightly.

[0041] The light blue hydrangea cultivation substrate should meet the following requirements: pH between 5.5 and 6.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 3% (w / w) and hydroxyaluminum content greater than 5% (w / w).

[0042] The standard blue hydrangea cultivation substrate should meet the following requirements: pH between 5.0 and 5.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 4% (w / w) and hydroxyl aluminum ratio greater than 8% (w / w), and available phosphorus content less than 30 mg / kg.

[0043] The dark blue cultivation substrate should meet the following requirements: pH between 4.8 and 5.2, organic matter content greater than 15%, aeration porosity greater than 20%, total aluminum content (calculated as Al2O3) greater than 6% (w / w) and hydroxyl aluminum ratio greater than 10% (w / w), and available phosphorus content less than 18 mg / kg.

[0044] If the above-mentioned indicators cannot be met, acidic peat and water plant sludge raw materials can be screened or their proportions adjusted appropriately to meet the relevant requirements. Furthermore, depending on the application scenario, such as potted hydrangeas or terrestrial cultivation, acidic peat and water plant sludge are used as the main raw materials, while other materials can be fine-tuned according to site conditions.

[0045] Example 2: Blue Hydrangea Tuning The shade of blue in hydrangeas isn't a fixed number; it can be broadly categorized into three types: light blue, standard blue (cobalt blue), and dark blue (purple-blue). Light blue hydrangeas typically appear in slightly acidic soil with low aluminum ion levels or when acidification is delayed, resulting in a soft, grayish-white hue. Standard blue hydrangeas generally appear in acidic soil (pH 5.0-5.5), with sufficient aluminum and slightly low available phosphorus content, exhibiting high saturation. Dark blue hydrangeas require strongly acidic soil (pH 4.8-5.2), excessive aluminum ions, and extremely low available phosphorus content.

[0046] Since hydrangeas are perennial flowers, they absorb some aluminum each year during flowering. The amount of aluminum absorbed varies depending on the cultivation substrate and the blue variety. Measurements show that the aluminum content in leaves and buds is approximately: light blue 300 mg / kg, standard blue 800 mg / kg, and dark blue 1200 mg / kg. Based on a 10-liter volume of 2-year-old hydrangea seedlings with a crown width of 50-60 cm, and assuming an annual dry weight of 1.5 kg after pruning, each plant absorbs approximately: light blue 450 mg, standard blue 1200 mg, and dark blue 1800 mg of aluminum annually. Using the cultivation substrate provided in Example 1, the total aluminum content of the light blue, standard blue, and dark blue substrates, converted to standard blue substrates, is 0.3 kg, 0.4 kg, and 0.6 kg, respectively, with aluminum hydroxyl content of approximately 15 g, 32 g, and 60 g, respectively, which can meet the aluminum requirements of hydrangeas for 20-33 years. It is evident that as long as the cultivation substrate meets the technical requirements, the aluminum content can satisfy the long-term cultivation needs of hydrangeas. However, long-term irrigation with tap water or ordinary river water will lead to an increase in the pH of the cultivation substrate. In addition to adding sulfur powder (0.4~0.6 g / L substrate) during substrate preparation to lower the pH in the long term, it is recommended to use rainwater for irrigation throughout the entire maintenance period, especially during the spring hydrangea germination and bud formation stage, to regularly adjust the acidity to quickly lower the pH and ensure the rapid release of heavy hydroxyl aluminum from water plant sludge to exchangeable aluminum. For standard blue hydrangeas, a 0.05% w / v citric acid solution can be used every 15~20 days until buds appear; for dark blue hydrangeas, a 0.1% w / v citric acid solution can be used, and the irrigation frequency can be increased to once every 10 days if necessary. Normal maintenance at other times can also achieve a good blue-toning effect.

[0047] In addition, for potted hydrangeas that are grown year-round, the blue coloring effect can still be achieved by preparing a new cultivation substrate according to the above requirements and maintaining it in accordance with the above care.

[0048] Example 3: Preparation of standard blue hydrangea cultivation substrate using sludge from a water plant in Shanghai 1. Sampling and analysis of sludge from water treatment plants Sampling and analysis of sludge from a typical water plant in Shanghai revealed a pH of 7.41 and a total aluminum content (calculated as Al2O3) of 35.8%, with soluble aluminum (mg / kg) at 0.644 mg / kg, indicating a low likelihood of direct aluminum toxicity. The active aluminum composition consisted of exchangeable aluminum (Ex-Al) 1.11 mg / kg, organically bound aluminum (Or-Al) 671 mg / kg, inorganic adsorbed aluminum (In-Al) 39.1 mg / kg, hydrated oxides and hydroxides of aluminum (Hy-Al) 57400 mg / kg, and aluminum humate (Ha-Al) 6190 mg / kg. Hydroxy-aluminum accounted for 89.27% ​​of the active aluminum and 16.03% of the total aluminum, meeting the requirements of this invention for the resource utilization of water plant sludge. In addition, the sludge from the water plant was tested for the content of eight heavy metals, namely copper 35.5 mg / kg, chromium 58 mg / kg, nickel 31 mg / kg, zinc 108 mg / kg, lead 18.8 mg / kg, cadmium 0.14 mg / kg, arsenic 33.2 mg / kg, and mercury 0.070 mg / kg. This indicates that the sludge from the water plant is clean and safe, and meets the heavy metal limit requirements of "Green Planting Soil" (CJ / T 340-2016).

[0049] 2. Key indicators of raw materials Based on the production requirements for cultivating standard blue hydrangeas, the key indicators of raw materials were determined. These included: organic fertilizer with a pH of 8.01, total nutrients of 4.78%, and available phosphorus content of 90.3 mg / kg; perlite with a particle size of 8-10 mm, a pH of 7.45, and an EC of 0.18 mS / cm; acidic peat with a pH of 4.47, organic matter of 72.8%, and a C / N ratio of 21; well-rotted pine bark:pine needles in a 1:1 ratio with a pH of 5.12; and sulfur powder from commonly used horticultural varieties.

[0050] 3. Prepare the blue hydrangea cultivation substrate according to the formula. The formula is organic fertilizer: perlite: acidic peat: decomposed pine bark and needles: water plant sludge = 0.2: 1.5: 4: 2: 2.3; the cultivation substrate also contains sulfur powder as a soil conditioner, and the amount of sulfur powder added is 0.4 g per liter of dry cultivation substrate.

[0051] The main indicators of the cultivation substrate were determined to be: pH 5.12, organic matter 24.62%, aeration porosity 26.48%, aluminum content (calculated as Al2O3) 6.81%, hydroxyaluminum content 9.45 g / mg (accounting for 13.52% of total aluminum content), and available phosphorus content 16.34 mg / kg, which meet the technical requirements of the standard blue hydrangea cultivation substrate specified in this invention.

[0052] 4. 3-year maintenance of blue hydrangeas In early spring, select the Endless Summer and Jiacheng varieties for cultivation, and follow the guidelines of 5g / cm 3 Add a slow-release, low-phosphorus compound fertilizer (NPK 7-3-7) in the correct proportion, and maintain it as usual throughout the growing season. To avoid raising the pH of the growing medium with tap water, irrigate with collected rainwater throughout the growing season. From mid-April, flower buds begin to form until late April when the flowers begin to open, showing a hint of blue. By mid-May, the flowers are in full bloom, with a very rich blue color. To conserve nutrients, prune the flowering branches in early June after flowering to control the plant size and make it suitable for the pot.

[0053] Because the hydrangea pot was large, it wasn't repotted the following year. However, in the spring of that year, it was potted with 5g / cm³ of fertilizer. 3 Add a low-phosphorus compound fertilizer (NPK 7-3-7) and a small amount of low-phosphorus organic fertilizer in the correct proportions, and irrigate with collected rainwater throughout the entire maintenance period. It was observed that from mid-April when flower buds began to form until late April when the flowers began to open, showing initial blue hues, the flowers were in full bloom by mid-May, maintaining a rich blue color. Routine maintenance remained the same as in previous years. In the third year, considering the large size of the hydrangea and the limitations imposed by the original pot, a larger pot was chosen. The same proportions of the growing medium were added, and this process was repeated, combined with repotting and the addition of new growing medium. It was found that the hydrangea consistently maintained its standard blue flowering effect.

[0054] Example 4: Blue-toning cultivation of three types of blue hydrangea A horticulture company had display requirements for hydrangeas in different color schemes. They selected the Endless Summer variety and set production requirements for three types of blue hydrangeas: light blue, standard blue, and dark blue.

[0055] 1. Raw material screening Raw material screening was conducted at the beginning of 2026. The available water plant sludge had the following main properties: pH 7.76, total aluminum (calculated as Al2O3) 27.82%, of which the soluble aluminum content (mg / kg) was 0.789 mg / kg, indicating a low possibility of direct aluminum toxicity. The hydroxyl aluminum content was 38724 mg / kg, accounting for approximately 13.93% of the total aluminum, meeting the requirements of this invention for the resource utilization of water plant sludge. To meet the production requirements for cultivating different shades of blue hydrangea, and to facilitate production and reduce costs, all materials were standardized except for acidic peat, which had different peat raw material sources. The organic fertilizer has a pH of 8.14, a total nutrient content of 4.56%, and an available phosphorus content of 120 mg / kg; the perlite has a particle size of 8-10 mm, a pH of 7.37, and an EC of 0.176 mS / cm; the coconut block has a particle size of 20-30 mm and an EC of 0.567 mS / cm; the decomposed pine bark has a pH of 5.35; the decomposed pine needles have a pH of 4.82; the sulfur used is a commonly used horticultural variety; different pH peats are selected according to different blue requirements, with light blue hydrangea using high-grade white peat with a pH of 4.78 and an available phosphorus content of 20.35 mg / kg; and standard blue and dark blue using high-grade white peat with a pH of 4.25 and an available phosphorus content of 15.37 mg / kg.

[0056] 2. Three blue-toned matrix formulas The three blue-toned matrix formulas are as follows: The cultivation substrate formula for the light blue hydrangea is as follows: organic fertilizer: perlite: acidic peat: decomposed coconut blocks: water plant sludge = 1:1:3.5:2:2.5. The substrate also contains sulfur powder, added at a rate of 0.4g per liter of dry substrate. The main indicators of the cultivation substrate formulated according to the above ratio were measured, specifically: pH 5.98, organic matter 21.86%, aeration porosity 28.64%, aluminum content (calculated as Al2O3) 6.95%, and aluminum hydroxyl content 7.21g / mg (10.37%). This cultivation substrate meets the relevant requirements for light blue hydrangea cultivation substrates specified in this invention.

[0057] The standard blue hydrangea cultivation substrate formula is as follows: organic fertilizer: perlite: acidic peat: decomposed pine bark and needles: water plant sludge = 0.3:1.2:3.8:2:2.7. The substrate also contains sulfur powder, added at a rate of 0.4 g per liter of dry substrate, with a decomposed pine bark:decomposed pine needles mass ratio of 2:1. The main indicators of the cultivation substrate formulated according to the above ratio were measured, specifically: pH 5.34, organic matter 18.92%, aeration porosity 27.37%, aluminum content (calculated as Al2O3) 7.10%, aluminum hydroxyl content 8.23 ​​mg / kg (11.59%), and available phosphorus content 22.34 mg / kg. This cultivation substrate meets the relevant requirements for blue hydrangea cultivation substrates specified in this invention.

[0058] The cultivation substrate formula for Deep Blue Hydrangea is as follows: perlite: acidic peat: decomposed pine bark and needles: water plant sludge = 1:4:2:3. The substrate also contains sulfur powder, added at a rate of 0.6 g per liter of dry substrate. The mass ratio of decomposed pine bark to decomposed pine needles can be adjusted to 1:2. The main indicators of the cultivation substrate formulated according to the above ratio were measured, specifically: pH 4.98, organic matter 22.45%, aeration porosity 22.21%, aluminum content (calculated as Al2O3) 8.34%, aluminum hydroxyl content 10.73 g / mg (12.87%), and available phosphorus content 16.78 mg / kg. This cultivation substrate meets the relevant requirements for Deep Blue Hydrangea cultivation substrates specified in this invention.

[0059] 3. Care instructions for three types of blue hydrangeas Choose a 10-liter pot and plant a 2-year-old Endless Summer variety, according to 5g / cm 3 Add low-phosphorus compound fertilizer in appropriate proportions. To avoid raising the pH of the cultivation substrate with tap water, irrigate with collected rainwater throughout the maintenance period. In addition to routine maintenance, the hydrangeas were cultivated in a large pot greenhouse to meet the requirements of the May Day display, ensuring that the daytime temperature was around 20-25°C and the nighttime temperature was around 16-18°C. Flower buds began to appear from mid-to-late March, and by mid-April, different blue petals had appeared in the hydrangeas cultivated in different cultivation substrates. By the end of April, the flowers basically showed different gradients of blue, reaching full bloom during the May Day display period.

[0060] 4. Hydrangea Blue Toning Effect To determine the blue-toning effect of hydrangeas, typical hydrangea samples of different blue hues were selected for measurement of plant aluminum ion content and leaf color difference. The specific results are shown in Table 1. Table 1 shows that the aluminum content in leaves and flower buds of different blue hydrangea varieties differed significantly. P <0.01), regardless of the aluminum ion content in leaves or flower buds, the order is dark blue > standard blue > light blue.

[0061] Table 1 Comparison of aluminum content and flower color difference in hydrangea plants of different blue hues Note: ** indicates a highly significant difference (P<0.01) between different columns in rows 2-3. Table 1 also shows that the color differences (L*brightness, a*red-green value, and b*yellow-blue value) of petals among different blue hues are significant and conform to the Endless Summer flower color laboratory reference standards (see Table 2). Table 1 further shows that the total color difference (ΔE) values ​​among different blue hues vary considerably and can be directly discerned by the naked eye (see Table 3). Specifically, the total color differences (ΔE) for light blue, standard blue, and dark blue are 98.48, 3.97, and 40.94, respectively, indicating significant color differences, even though they belong to the same blue family, reaching the level of different color systems.

[0062] Table 2 Endless Summer Flower Color Laboratory Reference Standards Table 3. Grading and Evaluation Standards for Total Color Difference ΔE Values ​​(Human Eye Resolution Threshold) The above specific embodiments are merely illustrative of the content of this disclosure and do not represent a limitation thereof. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A blue hydrangea cultivation substrate based on water plant sludge, characterized in that, The components include the following volume parts: 0-1 part organic fertilizer; 1 to 1.5 parts perlite; 3-4 parts acidic peat; 0-2 parts decomposed coconut chunks; 0-2 parts decomposed pine bark and pine needles; 1-3 parts water plant sludge.

2. The blue hydrangea cultivation substrate according to claim 1, characterized in that: The water plant sludge is the sludge generated during the purification of tap water using aluminum sulfate as a flocculant. The water plant sludge meets the following requirements: pH less than 7.8, total aluminum (calculated as Al2O3) content greater than 20% (w / w), and hydroxyl-bound aluminum content greater than 8% (w / w).

3. The blue hydrangea cultivation substrate according to claim 1, characterized in that: The blue hydrangea cultivation substrate also contains a soil conditioner, which is sulfur powder, and the amount of sulfur powder added is 0.4 g to 0.6 g per liter of dry cultivation substrate.

4. The blue hydrangea cultivation substrate according to claim 1, characterized in that: The blue hydrangea cultivation substrate should meet the following requirements: pH less than 6.5, organic matter content greater than 15% (w / w), aeration porosity greater than 20%, total aluminum (calculated as Al2O3) content greater than 3%, and aluminum hydroxyl content greater than 5% (w / w).

5. The blue hydrangea cultivation substrate according to any one of claims 1 to 4, characterized in that: When the blue hydrangea cultivation substrate is a light blue hydrangea cultivation substrate, it should meet the following requirements: pH between 5.5 and 6.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 3%, and aluminum hydroxyl content greater than 5%.

6. The blue hydrangea cultivation substrate according to claim 5, characterized in that: The formula for the light blue hydrangea cultivation substrate (by volume) is: organic fertilizer: perlite: acidic peat: decomposed coconut blocks: water plant sludge = (0.5~1): (1~1.5): (3~4): (1~2): (1~3).

7. The blue hydrangea cultivation substrate according to any one of claims 1 to 4, characterized in that: When the blue hydrangea cultivation substrate is a standard blue hydrangea cultivation substrate, it should meet the following requirements: pH between 5.0 and 5.5, organic matter content greater than 15%, aeration porosity greater than 20%, aluminum content (calculated as Al2O3) greater than 4% (w / w) and hydroxyl aluminum ratio greater than 8% (w / w), and available phosphorus content less than 30 mg / kg.

8. The blue hydrangea cultivation substrate according to claim 7, characterized in that: The standard blue hydrangea cultivation substrate formula (by volume) is: organic fertilizer: perlite: acidic peat: decomposed pine bark and pine needles: water plant sludge = (0.2~0.5): (1~1.5): (3~4): (1~2): (1.5~3); further, the decomposed pine bark and pine needles include decomposed pine bark and decomposed pine needles, wherein the mass ratio of decomposed pine bark to decomposed pine needles is 1: (0.25~1).

9. The blue hydrangea cultivation substrate according to claim 1, characterized in that: When the blue hydrangea cultivation substrate is a dark blue hydrangea cultivation substrate, it should meet the following requirements: pH between 4.8 and 5.3, organic matter content greater than 15%, aeration porosity greater than 20%, total aluminum content (calculated as Al2O3) greater than 6% (w / w) and hydroxyaluminum content greater than 10% (w / w), and available phosphorus content less than 18 mg / kg.

10. The blue hydrangea cultivation substrate according to claim 9, characterized in that: The formula for the cultivation substrate of Deep Blue Hydrangea (by volume) is: organic fertilizer: perlite: acidic peat: decomposed pine bark and pine needles: water plant sludge = (0~0.2): (1~1.5): (3~4): (1~2): (2~3); further, the decomposed pine bark and pine needles include decomposed pine bark and decomposed pine needles, wherein the mass ratio of decomposed pine bark to decomposed pine needles is 1: (1~2).

11. The method for preparing the blue hydrangea cultivation substrate according to any one of claims 1 to 10, characterized in that, The method includes the following steps: weighing each raw material component according to the volume ratio defined in any one of claims 1 to 10, and putting all components into a mixing device for uniform compounding and mixing to obtain the blue hydrangea cultivation substrate.

12. The preparation method according to claim 11, characterized in that: Hydrangeas grown in the aforementioned blue-toned hydrangea cultivation substrate can exhibit a blue flower color without the addition of additional blue-toned agents, and the color difference ΔE between the petal color and the standard color chart satisfies at least one of the following: Light blue: △E>3; Standard Blue: △E > 3; Dark blue: △E > 3; Wherein, the color difference ΔE is according to ΔE 00 The color difference formula is the color difference value measured under a D65 light source and a 10° field of view.

13. The method for cultivating hydrangeas using the blue hydrangea cultivation substrate according to any one of claims 1 to 10, characterized in that, Includes the following steps: During the routine maintenance of hydrangeas, tap water can be used for irrigation. However, after budding in spring, light blue hydrangeas can still be irrigated with tap water. But standard blue and dark blue hydrangeas should be irrigated with acidic irrigation solution instead of tap water. The regular irrigation cycle is 15 to 20 days, until the flower buds appear and then the acidic irrigation solution is stopped. If the petal color uniformity and the blue coloring depth do not meet the design specifications, the irrigation cycle is adjusted to 10 days. The acidic irrigation solution is naturally collected rainwater or a citric acid solution with a mass-volume fraction (w / v) of 0.05% to 0.1%; wherein, the standard blue hydrangea uses a citric acid solution with a mass-volume fraction (w / v) of 0.05%; and the dark blue hydrangea uses a citric acid solution with a mass-volume fraction (w / v) of 0.1%.

14. The hydrangea cultivation method according to claim 13, characterized in that: It also includes the step of preparing the corresponding blue-toned hydrangea cultivation substrate according to the target blue color when repotting hydrangeas.

15. The application of the blue hydrangea cultivation substrate according to any one of claims 1 to 10, the preparation method according to claim 11 or 12, and the hydrangea cultivation method according to claim 13 or 14 in the control of blue hydrangea flower color.

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