Nano selenium zinc nutrient agent, preparation method thereof and cultivation method of zinc selenium tea leaves

Abstract

This invention relates to the field of agricultural planting technology, disclosing a nano-selenium-zinc nutrient agent and its preparation method, as well as a cultivation method for zinc-selenium-enriched tea. The preparation method of the nano-selenium-zinc nutrient agent includes the following steps: mixing a selenium source with a zinc source and an auxiliary agent to form a glass precursor material; melting the glass precursor material to form a glass melt; cooling the glass melt to form a solid selenium-enriched zinc glass body; mixing the solid selenium-enriched zinc glass body with deionized water and then wet-milling it under the action of an organosilicon surfactant and a chelating agent to obtain the final product; wherein the selenium source is selenium oxide, and the preparation method of the selenium oxide includes: mixing selenium powder and oxide evenly, followed by calcination under an oxidizing atmosphere to obtain the selenium source selenium oxide. Implementing this invention can solve the problems of low zinc and selenium absorption efficiency, elemental antagonism, and unstable quality in traditional zinc-selenium-enriched tea production, achieving precise control of the zinc and selenium content in tea, and improving tea yield and quality.

Description

Technical Field

[0001] This invention relates to the field of agricultural planting technology, and in particular to a nano-selenium zinc nutrient agent and its preparation method, as well as a cultivation method for zinc- and selenium-enriched tea. Background Technology

[0002] Zinc and selenium are essential trace elements for the human body, playing vital physiological roles. Tea, as a daily beverage, is rich in zinc and selenium, which have positive effects on human health. However, traditional zinc- and selenium-enriched tea production suffers from problems such as low zinc and selenium absorption efficiency, significant inter-element antagonism, and unstable product quality. Current technologies often employ conventional fertilizer application methods, resulting in low zinc and selenium utilization rates and a tendency for elemental antagonism, leading to large fluctuations in zinc and selenium content in tea leaves and making precise control difficult. Furthermore, traditional methods have limited effectiveness in improving tea quality and cannot meet market demand for high-quality zinc- and selenium-enriched tea. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a nano-selenium zinc nutrient agent and its preparation method, as well as a cultivation method for zinc-selenium-enriched tea. This invention can solve the problems of low zinc and selenium absorption efficiency, element antagonism, and unstable quality in traditional zinc-selenium-enriched tea production, and achieve precise control of zinc and selenium content in tea, thereby improving tea yield and quality.

[0004] To address the aforementioned technical problems, the first aspect of this invention provides a method for preparing a nano-selenium-zinc nutrient, comprising the following steps: Selenium source is mixed with zinc source and additives to form glass precursor material; The glass precursor material is melted to form a glass melt; The molten glass is cooled to form a solid selenium-zinc-enriched glass. The solid selenium-rich zinc glass body is mixed with deionized water and then wet-milled under the action of organosilicon surfactants and chelating agents to obtain the final product. The selenium source is selenium oxide, and the preparation method of the selenium oxide includes: mixing selenium powder and oxide in a mass ratio of 1:(1.5-2.5) until uniform, and then calcining in an oxidizing atmosphere to obtain selenium oxide as the selenium source.

[0005] As an improvement to the above scheme, the particle size of the nano-selenium zinc nutrient is 50nm-200nm, and the molar ratio of selenium to zinc in the nano-selenium zinc nutrient is 1:(3-5).

[0006] As an improvement to the above scheme, in the glass precursor material, the mass ratio of the selenium source, zinc source and additives is 1:(2-3):(15-20). The calcination temperature is 350℃-700℃, and the calcination time is 20min-30min; The particle size of the selenium source is 100-300 mesh; The zinc source is zinc oxide, and the particle size of the zinc source is 100 mesh-300 mesh; The oxide is one or more of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and sodium oxide.

[0007] As an improvement to the above scheme, the additives include flux and stabilizer, and the mass ratio of the flux and stabilizer is (3.5-4.5):1; The flux is selected from one or more of sodium carbonate, potassium carbonate, borax, sodium oxide, and calcium oxide; The stabilizer is selected from one or more of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and sodium oxide.

[0008] As an improvement to the above solution, the melting temperature during the melting process is 1250℃-1350℃; The process of mixing the solid selenium-rich zinc glass with deionized water and then performing wet grinding under the action of organosilicon surfactants and chelating agents includes: mixing the solid selenium-rich zinc glass with deionized water and then performing wet grinding, adding organosilicon surfactants and chelating agents during the grinding process to make the glass micro powder uniformly dispersed in the deionized water. The solid selenium-rich zinc glass is mixed with deionized water at a ratio of 1:(10-20); The organosilicon surfactant is a modified methyltrisiloxane; The chelating agent is disodium EDTA.

[0009] A second aspect of the present invention provides a nano-selenium-zinc nutrient, which is prepared according to the preparation method described above.

[0010] A third aspect of this invention provides a method for cultivating zinc- and selenium-enriched tea leaves, comprising the following steps: (1) Diagnose the soil of the tea garden and divide the tea garden into high zinc and high selenium areas, medium zinc and medium selenium areas and low zinc and low selenium areas; (2) The nano-selenium zinc nutrient agent is prepared as a base fertilizer and applied to the soil in each area; (3) The nano-selenium zinc nutrient agent is formulated as a foliar fertilizer and sprayed during the critical growth period of tea trees; (4) Test the selenium and zinc content in the tea leaves to determine the timing of tea harvesting and then harvest the tea leaves.

[0011] As an improvement to the above scheme, the base fertilizer comprises 6-16 parts of nano-selenium zinc nutrient agent, 19-31 parts of humic acid, 3.5-6.5 parts of microbial agent, 9-16 parts of phosphate rock powder, 9.5-16 parts of potassium magnesium sulfate, 0.8-2 parts of zinc sulfate, 0.8-2 parts of manganese sulfate, and 18-28 parts of auxiliary components.

[0012] As an improvement to the above scheme, the base fertilizer used in the high zinc and high selenium area comprises 9-16 parts of nano-selenium zinc nutrient agent, 24-31 parts of humic acid, 4.8-6.5 parts of microbial agent, 9-13 parts of phosphate rock powder, 9.5-12.5 parts of potassium magnesium sulfate, 1.4-2 parts of zinc sulfate, 1.4-2 parts of manganese sulfate, and 18-26 parts of auxiliary components; The base fertilizer used in the medium zinc and medium selenium zone comprises 7-13 parts of nano-selenium zinc nutrient, 21-29 parts of humic acid, 3.5-5.5 parts of microbial agent, 10-16 parts of phosphate rock powder, 10-16 parts of potassium magnesium sulfate, 1-2 parts of zinc sulfate, 1-2 parts of manganese sulfate, and 21-26 parts of auxiliary components. The base fertilizer used in the low-zinc and low-selenium areas comprises 6-9 parts of nano-selenium zinc nutrient, 19-26 parts of humic acid, 3.5-4.5 parts of microbial agent, 12.5-16 parts of phosphate rock powder, 12-16 parts of potassium magnesium sulfate, 0.8-1.7 parts of zinc sulfate, 0.8-1.7 parts of manganese sulfate, and 26-28 parts of auxiliary components.

[0013] As an improvement to the above scheme, the application rate of the base fertilizer in the soil of each zone is 150 kg / mu to 200 kg / mu; The foliar fertilizer contains 0.8 g / L-1.5 g / L of selenium, 0.5 g / L-1.2 g / L of zinc, and has a pH of 6.5-7.5. At the time of harvest, the selenium content in the tea leaves was 0.25 mg / kg-0.5 mg / kg, and the zinc content was 45 mg / kg-60 mg / kg.

[0014] Implementing this invention has the following beneficial effects: (1) In this invention, selenium powder and oxide are mixed and calcined to form a selenium source, which is then melted with a zinc source and additives to prepare a nano-selenium-zinc nutrient. The nano-selenium-zinc nutrient is nanoscale with a large specific surface area, making it easy to be absorbed through leaves or roots. Moreover, the selenium and zinc elements coexist in the glass network in the nano-selenium-zinc nutrient, which can effectively reduce the competitive absorption of ionic bonds. Furthermore, wet grinding makes the nanoparticles uniformly dispersed in water to form a stable system, which improves the effectiveness of selenium and zinc elements in the nano-selenium-zinc nutrient, ensures the quality of tea, and solves the problems of low zinc and selenium absorption efficiency and obvious inter-element antagonism in existing nano-selenium-zinc nutrient. (2) In this invention, by applying foliar fertilizer in conjunction with soil fertilization during multiple key growth stages of tea trees, the precise regulation and synergistic effect of zinc and selenium content in tea leaves are achieved, so that the selenium and zinc content of finished tea leaves are stabilized within a certain range, while significantly improving the quality and yield of tea leaves. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0017] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0018] To address the above problems, the first aspect of this invention provides a method for preparing a nano-selenium-zinc nutrient, comprising the following steps: S1. Mix the selenium source with the zinc source and additives to form a glass precursor material; S2. The glass precursor material is melted to form a glass melt; S3. Cool the molten glass to form a solid selenium-zinc-rich glass body; S4. The solid selenium-rich zinc glass is mixed with deionized water and then wet-milled under the action of organosilicon surfactant and chelating agent to obtain the final product.

[0019] In this invention, the nano-selenium-zinc nutrient obtained by the above method is nanoscale, with a large specific surface area, making it easy to be absorbed through leaves or roots and efficiently transported within the tea plant. Moreover, the coexistence of selenium and zinc elements in the nano-selenium-zinc nutrient in the glass network can effectively reduce competitive absorption by ionic bonds. At the same time, the organosilicon surfactant and chelating agent can ensure that the nanoparticles are uniformly dispersed in water, forming a stable system, improving the effectiveness of selenium and zinc elements in the nano-selenium-zinc nutrient, and ensuring the quality of tea. Thus, by combining nanomaterial technology with plant absorption, the problems of low zinc and selenium absorption efficiency and significant inter-element antagonism in existing nano-selenium-zinc nutrient are solved.

[0020] The molar ratio of selenium to zinc in the nano-selenium-zinc nutrient is 1:(3-5), which ensures the synergistic absorption of selenium and zinc in tea plants and avoids elemental antagonism. If the ratio is too small, excessive selenium content may lead to selenium toxicity; if the ratio is too large, excessive zinc content may affect tea plant growth and tea quality. Exemplarily, the molar ratio of selenium to zinc in the nano-selenium-zinc nutrient is 1:3, 1:3.5, 1:4, 1:4.5, or 1:5, but is not limited to these.

[0021] Specifically, in step S1, the mass ratio of the selenium source, zinc source and additives in the glass precursor material is 1:(2-3):(15-20). This can fix the ratio of selenium and zinc, ensuring that selenium and zinc can coexist well in the glass system after the melting reaction and are slowly released after application, avoiding problems such as uneven local concentration or asynchronous release, and thus avoiding the antagonistic effect of selenium and zinc.

[0022] Furthermore, the selenium source is selenium oxide, and the preparation method of the selenium oxide includes: mixing selenium powder and oxide uniformly at a mass ratio of 1:(1.5-2.5), and then calcining under an oxidizing atmosphere to obtain the selenium source selenium oxide. In this process, calcination under an oxidizing atmosphere allows the selenium powder to vaporize and react in the oxidizing atmosphere to generate selenium oxide. Compared with commercially available selenium oxide, it has higher activity, better quality control, and more uniform morphology, which may make it more effective in specific applications. Of course, it is understandable that if the performance requirements are not particularly high, commercially available selenium oxide products can be chosen, for example, in foliar fertilizers.

[0023] The selenium source has a particle size of 100-300 mesh, which ensures that the selenium powder is converted into highly active, quality-controllable selenium oxide under an oxidizing atmosphere, and that its morphology is uniform, which is beneficial for its uniform integration into the glass network. In some embodiments, the calcined product can be cooled and crushed to ensure that the particle size of the selenium source meets the requirements.

[0024] Furthermore, the zinc source can be zinc oxide (ZnO), and the particle size of the zinc source is 100-300 mesh.

[0025] Optionally, the oxide is one or more of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and sodium oxide, which can provide sufficient oxygen during the calcination process to completely oxidize the selenium powder into selenium oxide.

[0026] Optionally, the additives include flux and stabilizer, wherein the mass ratio of flux to stabilizer is (3.5-4.5):1. During melt processing, the flux can effectively promote the formation of glass network, effectively fix selenium and zinc, and maintain their synergistic ratio as much as possible during release, reduce the loss of selenium content at high temperature, and maintain a certain mechanical strength to ensure that the structure is not damaged during subsequent wet grinding.

[0027] In some embodiments, the flux is selected from one or more of sodium carbonate, potassium carbonate, borax, sodium oxide, and calcium oxide.

[0028] In some embodiments, the stabilizer is selected from one or more of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and sodium oxide.

[0029] In some embodiments, the calcination temperature is 350℃-700℃ and the calcination time is 20min-30min, which can convert selenium powder into highly active, quality-controllable selenium oxide under an oxidizing atmosphere, and the oxide has a uniform morphology, which is conducive to its uniform integration into the glass network.

[0030] Specifically, in step S2, during the melting process, the melting temperature is 1250℃-1350℃, allowing the glass precursor material to completely melt and form a uniform liquid phase. This results in a uniform and stable glass network, where selenium and zinc are uniformly dispersed in the three-dimensional network. Simultaneously, it inhibits selenium volatilization, maintains the stability of the selenium valence state, and preserves the stability and availability of zinc. Exemplarily, the melting temperature can be 1250℃, 1275℃, 1300℃, 1325℃, or 1350℃, but is not limited to these.

[0031] In some embodiments, the glass precursor material can be placed in a high-temperature resistant crucible and heated until the glass precursor material is completely melted.

[0032] Specifically, in step S3, the cooling rate is 5℃ / min-10℃ / min. If the cooling rate is too fast, it will cause the glass structure to be uneven, while if it is too slow, it may affect the production efficiency.

[0033] In some embodiments, molten glass can be poured into a mold for cooling.

[0034] Specifically, in step S4, the wet grinding of the solid selenium-enriched zinc glass with deionized water under the action of organosilicon surfactants and chelating agents includes: mixing the solid selenium-enriched zinc glass with deionized water and then performing wet grinding; adding organosilicon surfactants and chelating agents during the grinding process to ensure that the glass micropowder is uniformly dispersed in the deionized water. By wet grinding the solid selenium-enriched zinc glass, it reaches the nanoscale, allowing the selenium and zinc sources in the nano-selenium-zinc nutrient to be stably suspended in the water system with specific nanostructures, forming an aqueous suspension of nanoparticles. This allows for better coordination with fertilizers for foliar spraying and soil irrigation fertilization. The addition of organosilicon surfactants can form a protective film on the nanoparticles, blocking their self-aggregation tendency through steric hindrance and enhancing their wettability on tea leaves, enabling rapid spreading and improving leaf absorption efficiency. The addition of chelating agents can combine with other metal ions in the system to form complexes, allowing selenium and zinc to exist stably in a form that can be absorbed by the tea plant, promoting root or leaf absorption and comprehensively maintaining the effectiveness of the nano-selenium-zinc nutrient.

[0035] Furthermore, the particle size of the nano-selenium-zinc nutrient agent is 50nm-200nm. Further controlling the particle size not only fully utilizes its strong migration ability in soil pore water, allowing for better absorption of selenium and zinc by the roots, but also improves the entry of nanoparticles into the tea plant through leaf stomata. This ensures that the nano-selenium-zinc nutrient agent can be applied directly to the soil as a base fertilizer component, and also sprayed onto the tea leaves as a foliar fertilizer. For example, the particle size of the nano-selenium-zinc nutrient agent is 50nm, 75nm, 100nm, 125nm, 150nm, 175nm, or 200nm, but is not limited to these.

[0036] Optionally, the organosilicon surfactant includes, but is not limited to, modified methyltrisiloxane, and its dosage is related to the mass of the finished fertilizer containing nano-selenium zinc nutrients. In some embodiments, the amount of organosilicon surfactant added is 0.1%-0.3% of the total mass of the finished fertilizer, for example, 0.1%, 0.15%, 0.2%, 0.25%, or 0.3%, but is not limited thereto.

[0037] Optionally, the chelating agent includes, but is not limited to, disodium EDTA, and its dosage is related to the mass of the finished fertilizer containing nano-selenium-zinc nutrients. In some embodiments, the amount of the chelating agent added is 0.05%-0.2% of the total mass of the finished fertilizer, and exemplary amounts can be 0.05%, 0.075%, 0.1%, 0.125%, 0.15%, 0.175%, and 0.2%, but are not limited thereto.

[0038] In some embodiments, the solid selenium-zinc glass can be coarsely crushed before wet grinding, which helps to improve efficiency and better control the particle size uniformity of the nano-selenium-zinc nutrient.

[0039] A second aspect of the present invention provides a nano-selenium-zinc nutrient, which is prepared according to the preparation method described above.

[0040] A third aspect of this invention provides a method for cultivating zinc- and selenium-enriched tea leaves, comprising the following steps: (1) Diagnose the soil of the tea garden and divide the tea garden into high zinc and high selenium areas, medium zinc and medium selenium areas and low zinc and low selenium areas; (2) The nano-selenium zinc nutrient agent is prepared as a base fertilizer and applied to the soil in each area; (3) The nano-selenium zinc nutrient is formulated as a foliar fertilizer and sprayed during the critical growth period of tea trees; (4) Test the selenium and zinc content in the tea leaves to determine the timing of tea harvesting and then harvest the tea leaves.

[0041] Specifically, in step (1), the pH value, organic matter content, zinc content, selenium content and trace element content of the tea garden soil are detected and analyzed, and the tea garden is divided into high zinc and high selenium area, medium zinc and medium selenium area and low zinc and low selenium area according to the selenium and zinc content in the soil.

[0042] In some specific and preferred embodiments, the soil in the high zinc and high selenium zone has a selenium content > 0.3 mg / kg and a zinc content > 50 mg / kg; the soil in the medium zinc and medium selenium zone has a selenium content of 0.15 mg / kg-0.3 mg / kg and a zinc content of 30 mg / kg-50 mg / kg; and the soil in the low zinc and low selenium zone has a selenium content < 0.15 mg / kg and a zinc content < 30 mg / kg.

[0043] Specifically, in step (2), the base fertilizer comprises 6-16 parts of nano-selenium zinc nutrient agent, 19-31 parts of humic acid, 3.5-6.5 parts of microbial agent, 9-16 parts of phosphate rock powder, 9.5-16 parts of potassium magnesium sulfate, 0.8-2 parts of zinc sulfate, 0.8-2 parts of manganese sulfate, and 18-28 parts of auxiliary components. The application rate of the base fertilizer in the soil of each area is 150 kg / mu-200 kg / mu. The tea trees in the soil have a high absorption rate of selenium and zinc, which can promote the yield and quality of tea.

[0044] Furthermore, based on the soil zoning results in step (1), specific base fertilizers containing nano-selenium zinc nutrients can be formulated for each zone of tea garden. The soil in the high zinc and high selenium zone already contains a high level of zinc and selenium, so less nano-selenium zinc nutrients are needed. The low zinc and low selenium zone needs more nano-selenium zinc nutrients to supplement the deficiency, so as to ensure that the zinc and selenium content in the tea meets the requirements. This can further promote the absorption of zinc and selenium in the base fertilizer by the tea tree, increase the tea yield, and control the selenium and zinc content in the tea.

[0045] In some embodiments, the base fertilizer used in the high-zinc and high-selenium area comprises 9-16 parts of nano-selenium zinc nutrient, 24-31 parts of humic acid, 4.8-6.5 parts of microbial agent, 9-13 parts of phosphate rock powder, 9.5-12.5 parts of potassium magnesium sulfate, 1.4-2 parts of zinc sulfate, 1.4-2 parts of manganese sulfate, and 18-26 parts of auxiliary components.

[0046] In some embodiments, the base fertilizer used in the zinc-selenium zone comprises 7-13 parts of nano-selenium zinc nutrient, 21-29 parts of humic acid, 3.5-5.5 parts of microbial agent, 10-16 parts of phosphate rock powder, 10-16 parts of potassium magnesium sulfate, 1-2 parts of zinc sulfate, 1-2 parts of manganese sulfate, and 21-26 parts of auxiliary components.

[0047] In some embodiments, the base fertilizer used in the low-zinc and low-selenium areas comprises 6-9 parts of nano-selenium zinc nutrient, 19-26 parts of humic acid, 3.5-4.5 parts of microbial agent, 12.5-16 parts of phosphate rock powder, 12-16 parts of potassium magnesium sulfate, 0.8-1.7 parts of zinc sulfate, 0.8-1.7 parts of manganese sulfate, and 26-28 parts of auxiliary components.

[0048] Understandably, topdressing can be applied appropriately to the soil in high-zinc and high-selenium areas, medium-zinc and medium-selenium areas, and low-zinc and low-selenium areas, depending on the growth of the tea trees.

[0049] By appropriately adjusting the content of components such as nano-selenium-zinc nutrients and humic acid based on the selenium and zinc content in the soil, several advantages can be achieved. First, it allows for precise control of selenium and zinc nutrition, avoiding the risk of over-application: the amount of nano-selenium-zinc nutrients added can be adjusted according to the zinc and selenium content in the soil, preventing excessive selenium from causing plant toxicity and excessive zinc from affecting crop growth. Second, it can improve the bioavailability of selenium and zinc: by adjusting components such as humic acid, the soil environment can be improved, increasing the solubility and availability of selenium and zinc. Third, it can promote crop absorption and quality improvement: humic acid can stimulate crop root growth, improve the efficiency of crop absorption of selenium and zinc, thereby promoting crop quality improvement.

[0050] Optionally, the auxiliary components may be silicates, phosphates, mixtures of trace elements, etc., used to improve the physicochemical properties of fertilizers and promote nutrient absorption. Those skilled in the art can add them reasonably according to the actual situation, and this application does not make specific limitations in this regard.

[0051] Specifically, in step (3), the foliar fertilizer is prepared by mixing nano-selenium zinc nutrient agent with deionized water at a ratio of 1: (8-22). By stirring evenly, the selenium content in the foliar fertilizer is 0.8g / L-1.5g / L, the zinc content is 0.5g / L-1.2g / L, and the pH is 6.5-7.5. Controlling the pH of the foliar fertilizer to 6.5-7.5 can promote the absorption of active nutrients in the foliar fertilizer by the leaves. Controlling the selenium and zinc content can have a synergistic effect with the root absorption in the soil. Controlling the selenium content in the tea leaves at harvest time to be stable at 0.25-0.5mg / kg and the zinc content to be stable at 45-60mg / kg. Furthermore, the mass ratio of the nano-selenium zinc nutrient to deionized water is 1:(10-20). Too small a water ratio will lead to uneven grinding, while too large a water ratio will reduce the concentration of nanoparticles and affect the effect.

[0052] In some specific and preferred embodiments, spraying during the critical growth period of tea trees includes: (31) Before the spring tea buds sprout, the tea trees are pruned. Three to seven days after pruning, the tea tree canopy is sprayed with foliar fertilizer for the first time. In this step, the pruned tea trees are generally controlled to a height of 2cm-5cm; the foliar fertilizer is a diluted solution diluted 3-12 times, with a dosage of 300mL / mu-600mL / mu. In some embodiments, the foliar fertilizer is a diluted solution diluted 8 times, with a dosage of 500mL / mu. It should be noted that the mL / mu unit in the foliar fertilizer dosage refers to the dosage per mu of tea trees.

[0053] Understandably, the period before spring tea buds sprout generally refers to early February.

[0054] (32) When the new shoots of the tea tree have sprouted to the stage of one bud and one leaf at the beginning of unfolding, spray the tea tree canopy with foliar fertilizer for the second time; In this step, the foliar fertilizer is a diluted solution diluted 3-12 times, and the dosage is 300mL / mu-600mL / mu. In some embodiments, the foliar fertilizer is a diluted solution diluted 8 times, and the dosage is 500mL / mu.

[0055] (33) Apply foliar fertilizer to the tea tree canopy for the third time 3-7 days after each tea harvest; In this step, the foliar fertilizer is a diluted solution diluted 3-12 times, and the dosage is 300mL / mu-600mL / mu. In some embodiments, the foliar fertilizer is a diluted solution diluted 8 times, and the dosage is 400mL / mu.

[0056] In this invention, by combining soil fertilization with foliar fertilization at multiple key stages of tea tree growth, precise regulation and synergistic effects of zinc and selenium content in tea are achieved, ensuring that the selenium and zinc content of the finished tea is stabilized within a certain range, while significantly improving tea quality and yield.

[0057] Specifically, in step (4), the selenium and zinc content in the tea leaves is dynamically monitored. According to the dynamic monitoring results, the optimal harvesting time is when the selenium content in the tea leaves is 0.25 mg / kg-0.5 mg / kg and the zinc content is 45 mg / kg-60 mg / kg. In some embodiments, a method for cultivating zinc- and selenium-rich tea further includes: after the first harvest of summer tea leaves, conducting a second soil diagnosis and zoning of the tea garden, and adjusting the ratio of base fertilizer and topdressing fertilizer according to the diagnosis results.

[0058] It is understood that the nano-selenium zinc nutrient and the cultivation method of zinc- and selenium-enriched tea leaves in this invention are applicable to tea varieties including but not limited to Yunnan large-leaf variety.

[0059] The present invention will be further described below with reference to specific embodiments: Example 1 This embodiment provides a nano-selenium-zinc nutrient agent, the preparation method of which includes the following steps: S1. After mixing selenium powder and oxide in a mass ratio of 1:2, calcine them at 500°C for 25 minutes to generate selenium oxide as a selenium source; then mix the selenium source with zinc source and additives to form a glass precursor material. The amount of selenium source added is 1.5 parts, the amount of zinc source added is 3.5 parts, and the amount of additives added is 25 parts. S2. Place the glass precursor material into a high-temperature resistant crucible and heat it to 1300℃ to form a uniform glass melt. S3. Pour the molten glass into a mold and let it cool to form a solid selenium-rich zinc glass body. S4. After mixing the solid selenium-rich zinc glass with deionized water, wet grinding is carried out under the action of organosilicon surfactants and chelating agents to obtain... The nano-selenium-zinc nutrient obtained in this embodiment has a particle size of 100 nm and a molar ratio of selenium to zinc of 1:4.

[0060] Application Example 1 This application example provides a cultivation method for zinc- and selenium-enriched tea leaves. The method involves preparing basal fertilizer and foliar fertilizer using the nano-selenium-zinc nutrient solution obtained in Example 1, and includes the following steps: (1) Diagnose the soil of the tea garden and divide the tea garden into high zinc and high selenium areas, medium zinc and medium selenium areas and low zinc and low selenium areas; (2) The nano-selenium-zinc nutrient agent is prepared as a base fertilizer and applied to the soil in each area at a rate of 180 kg per mu; wherein, The base fertilizer formulation for high-zinc and high-selenium areas is as follows: 10% nano-selenium zinc nutrient, 25% humic acid, 5% microbial inoculant, 12% phosphate rock powder, 12% potassium magnesium sulfate, 1.5% zinc sulfate, 1.5% manganese sulfate, and 20% auxiliary components; The base fertilizer formulation for medium-zinc and medium-selenium areas is as follows: 8% nano-selenium zinc nutrient, 22% humic acid, 4% microbial inoculant, 13% phosphate rock powder, 13% potassium magnesium sulfate, 1.2% zinc sulfate, 1.2% manganese sulfate, and 22% auxiliary components; The base fertilizer formulation for low-zinc and low-selenium areas is as follows: 5% nano-selenium zinc nutrient, 20% humic acid, 3% microbial inoculant, 15% phosphate rock powder, 15% potassium magnesium sulfate, 1% zinc sulfate, 1% manganese sulfate, and 25% auxiliary components.

[0061] (3) The nano-selenium-zinc nutrient agent is formulated as a foliar fertilizer and sprayed during the critical growth period of tea trees. The foliar fertilizer contains 1.2 g / L of selenium, 0.8 g / L of zinc, and has a pH of 7.0. Specifically: (31) Before the spring tea buds sprout (early February), the tea trees are pruned to a height of 2-5cm. On the 5th day after the tea trees are pruned, the tea tree canopy is sprayed with foliar fertilizer for the first time at a rate of 500mL / mu, diluted 8 times before spraying. (32) When the new shoots of the tea tree have sprouted to the stage of one bud and one leaf unfolding, the foliar fertilizer should be sprayed on the canopy of the tea tree for the second time. The amount is 500 mL / mu, diluted 8 times before spraying. (33) On the 5th day after each tea picking, water-soluble foliar fertilizer was sprayed on the canopy of the tea trees. The amount of water-soluble foliar fertilizer was 400 mL / mu, diluted 8 times before spraying.

[0062] (4) Test the selenium and zinc content in the tea leaves to determine the timing of tea harvesting and then harvest the tea leaves.

[0063] Application Example 2 This application example provides a cultivation method for zinc- and selenium-enriched tea leaves. The nano-selenium-zinc nutrient solution obtained in Example 1 is used to prepare both base fertilizer and foliar fertilizer. An experiment was conducted in a Pu'er tea producing area in Yunnan Province, selecting mature tea gardens of the "Yunnan Large Leaf" variety with consistent growth conditions. The method includes the following steps: (1) Diagnose the soil of the tea garden and divide the tea garden into high zinc and high selenium areas, medium zinc and medium selenium areas and low zinc and low selenium areas; (2) The nano-selenium-zinc nutrient agent is prepared as a base fertilizer and applied to the soil in each area at a rate of 180 kg per mu; wherein, The base fertilizer formulation for high-zinc and high-selenium areas is as follows: 15% nano-selenium zinc nutrient, 30% humic acid, 6% microbial inoculant, 10% phosphate rock powder, 10% potassium magnesium sulfate, 2% zinc sulfate, 2% manganese sulfate, and 25% auxiliary components; The base fertilizer formulation for medium-zinc and medium-selenium areas is as follows: 12% nano-selenium zinc nutrient, 28% humic acid, 5% microbial inoculant, 11% phosphate rock powder, 11% potassium magnesium sulfate, 1.8% zinc sulfate, 1.8% manganese sulfate, and 25% auxiliary components; The base fertilizer formulation for low-zinc and low-selenium areas is as follows: 8% nano-selenium zinc nutrient, 25% humic acid, 4% microbial inoculant, 13% phosphate rock powder, 13% potassium magnesium sulfate, 1.5% zinc sulfate, 1.5% manganese sulfate, and 27% auxiliary components. Apply 200 kg per acre to the soil.

[0064] (3) The nano-selenium-zinc nutrient agent is formulated as a foliar fertilizer and sprayed during the critical growth period of tea trees. The foliar fertilizer contains 1.5 g / L of selenium, 1.2 g / L of zinc, and has a pH of 7.2. Specifically: (31) Before the spring tea sprouts (early February), the tea trees are pruned to a height of 2-5cm. On the third day after the tea trees are pruned, the tea tree canopy is sprayed with foliar fertilizer for the first time. The amount of foliar fertilizer is 600mL / mu, diluted 10 times before spraying. (32) When the new shoots of the tea tree have sprouted to the stage of one bud and one leaf unfolding, the foliar fertilizer should be sprayed on the canopy of the tea tree for the second time. The amount of water-soluble foliar fertilizer is 600 mL / mu, diluted 10 times before spraying. (33) On the third day after each tea picking, water-soluble foliar fertilizer was sprayed on the canopy of the tea trees. The amount of water-soluble foliar fertilizer was 500 mL / mu, diluted 10 times before spraying.

[0065] (4) Test the selenium and zinc content in the tea leaves to determine the timing of tea harvesting and then harvest the tea leaves.

[0066] Application Example 3 This application example provides a cultivation method for zinc- and selenium-enriched tea leaves. The nano-selenium-zinc nutrient solution obtained in Example 1 is used to prepare both basal fertilizer and foliar fertilizer, which is basically the same as Application Example 1, except that: (1) The nano-selenium zinc nutrient is prepared as a base fertilizer and applied to the soil at a rate of 180 kg per mu; wherein the base fertilizer ratio is: 12% nano-selenium zinc nutrient, 28% humic acid, 5% microbial agent, 11% phosphate rock powder, 11% potassium magnesium alum, 1.8% zinc sulfate, 1.8% manganese sulfate and 25% auxiliary components.

[0067] (2) Same as application example 1; (3) Test the selenium and zinc content in the tea leaves to determine the timing of tea harvesting and then harvest the tea leaves.

[0068] Application Example 4 This application example provides a cultivation method for zinc- and selenium-enriched tea leaves, which is basically the same as Application Example 1, except that: Base fertilizers were prepared using the nano-selenium-zinc nutrient agent obtained in Example 1. Step (3) is not included, that is, foliar fertilization at different stages is not carried out.

[0069] Application Example 5 This application example provides a cultivation method for zinc- and selenium-enriched tea leaves, which is basically the same as Application Example 1, except that: Foliar fertilizer was formulated using the nano-selenium-zinc nutrient solution obtained in Example 1; Step (2) Use conventional compound fertilizer (common compound fertilizer N:P:K=15-15-15) as base fertilizer and apply it to the soil of each area at a rate of 180 kg per mu.

[0070] Application Example 6 This application example provides a method for producing zinc- and selenium-enriched tea, which is basically the same as application example 1, except that: Step (2) Prepare a standard selenium-zinc nutrient solution (commercially available selenium-zinc nutrient solution: selenium content 0.5%, zinc content 1.5%) as a base fertilizer and apply it to the soil in each area; The selenium content and virginity of the fresh tea leaves harvested, corresponding to test cases 1-6, were measured, and the yield increase rate was calculated. The quality was then scored using a 1-10 point scale, with the specific criteria as follows: 9.0-10.0 points: Rich aroma, fresh and refreshing taste, bright liquor color, and tender green tea leaves; 8.0-8.9 points: Strong aroma, fresh taste, bright liquor color, and green tea leaves; 7.0-7.9 points: Aroma is average, taste is fairly fresh, liquor color is average, and tea leaves are average; 6.0-6.9 points: weak aroma, bland taste, dark liquor, and old tea leaves; 5.0-5.9 points: Poor aroma, poor taste, cloudy liquor, and poor tea leaves.

[0071] The results are shown in Table 1.

[0072] Table 1. Detection results of tea obtained from Application Examples 1-6

[0073] The results above show that by using the nano-selenium-zinc nutrient agent of this invention to formulate base fertilizer and foliar fertilizer, and in conjunction with the cultivation method described in this application, precise regulation and control of zinc- and selenium-rich tea can be achieved, significantly increasing the zinc and selenium content in tea, while also improving tea yield and quality.

[0074] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a nano-selenium-zinc nutrient, characterized in that, Includes the following steps: Selenium source is mixed with zinc source and additives to form glass precursor material; The glass precursor material is melted to form a glass melt; The molten glass is cooled to form a solid selenium-zinc-enriched glass. The solid selenium-rich zinc glass body is mixed with deionized water and then wet-milled under the action of organosilicon surfactants and chelating agents to obtain the final product. The selenium source is selenium oxide, and the preparation method of the selenium oxide includes: mixing selenium powder and oxide in a mass ratio of 1:(1.5-2.5) until uniform, and then calcining in an oxidizing atmosphere to obtain selenium oxide as the selenium source.

2. The preparation method of the nano-selenium-zinc nutrient agent as described in claim 1, characterized in that, The nano-selenium zinc nutrient has a particle size of 50nm-200nm, and the molar ratio of selenium to zinc in the nano-selenium zinc nutrient is 1:(3-5).

3. The preparation method of the nano-selenium-zinc nutrient agent as described in claim 1 or 2, characterized in that, In the glass precursor material, the mass ratio of the selenium source, zinc source and additives is 1:(2-3):(15-20). The calcination temperature is 350℃-700℃, and the calcination time is 20min-30min; The particle size of the selenium source is 100-300 mesh; The zinc source is zinc oxide, and the particle size of the zinc source is 100 mesh-300 mesh; The oxide is one or more of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and sodium oxide.

4. The preparation method of the nano-selenium-zinc nutrient agent as described in claim 1 or 3, characterized in that, The additives include flux and stabilizer, and the mass ratio of the flux and stabilizer is (3.5-4.5):1; The flux is selected from one or more of sodium carbonate, potassium carbonate, borax, sodium oxide, and calcium oxide; The stabilizer is selected from one or more of silicon dioxide, aluminum oxide, calcium oxide, magnesium oxide, and sodium oxide.

5. The preparation method of the nano-selenium-zinc nutrient agent as described in claim 1, characterized in that, During the aforementioned melting process, the melting temperature is 1250℃-1350℃; The process of mixing the solid selenium-rich zinc glass with deionized water and then performing wet grinding under the action of organosilicon surfactants and chelating agents includes: mixing the solid selenium-rich zinc glass with deionized water and then performing wet grinding, adding organosilicon surfactants and chelating agents during the grinding process to make the glass micro powder uniformly dispersed in the deionized water. The solid selenium-rich zinc glass is mixed with deionized water at a ratio of 1:(10-20); The cooling rate is 5-10℃ / min; The organosilicon surfactant is a modified methyltrisiloxane; The chelating agent is disodium EDTA.

6. A nano-selenium-zinc nutrient, characterized in that, It is prepared according to the preparation method described in any one of claims 1-5.

7. A method for cultivating zinc- and selenium-enriched tea leaves, characterized in that, Includes the following steps: (1) Diagnose the soil of the tea garden and divide the tea garden into high zinc and high selenium areas, medium zinc and medium selenium areas and low zinc and low selenium areas; (2) The nano-selenium zinc nutrient agent as described in claim 6 is formulated as a base fertilizer and applied to the soil in each area; (3) The nano-selenium zinc nutrient agent as described in claim 6 is formulated as a foliar fertilizer and sprayed during the critical growth period of tea trees; (4) Test the selenium and zinc content in the tea leaves to determine the timing of tea harvesting and then harvest the tea leaves.

8. The cultivation method for zinc- and selenium-enriched tea leaves as described in claim 7, characterized in that, The base fertilizer comprises 6-16 parts of nano-selenium zinc nutrient agent, 19-31 parts of humic acid, 3.5-6.5 parts of microbial agent, 9-16 parts of phosphate rock powder, 9.5-16 parts of potassium magnesium sulfate, 0.8-2 parts of zinc sulfate, 0.8-2 parts of manganese sulfate, and 18-28 parts of auxiliary components.

9. The cultivation method for zinc- and selenium-enriched tea leaves as described in claim 8, characterized in that, The base fertilizer used in the high zinc and high selenium areas comprises 9-16 parts of nano-selenium zinc nutrient agent, 24-31 parts of humic acid, 4.8-6.5 parts of microbial agent, 9-13 parts of phosphate rock powder, 9.5-12.5 parts of potassium magnesium sulfate, 1.4-2 parts of zinc sulfate, 1.4-2 parts of manganese sulfate, and 18-26 parts of auxiliary components. The base fertilizer used in the medium zinc and medium selenium zone comprises 7-13 parts of nano-selenium zinc nutrient, 21-29 parts of humic acid, 3.5-5.5 parts of microbial agent, 10-16 parts of phosphate rock powder, 10-16 parts of potassium magnesium sulfate, 1-2 parts of zinc sulfate, 1-2 parts of manganese sulfate, and 21-26 parts of auxiliary components. The base fertilizer used in the low-zinc and low-selenium areas comprises 6-9 parts of nano-selenium zinc nutrient, 19-26 parts of humic acid, 3.5-4.5 parts of microbial agent, 12.5-16 parts of phosphate rock powder, 12-16 parts of potassium magnesium sulfate, 0.8-1.7 parts of zinc sulfate, 0.8-1.7 parts of manganese sulfate, and 26-28 parts of auxiliary components.

10. The cultivation method for zinc- and selenium-enriched tea leaves as described in claim 8, characterized in that, The application rate of the base fertilizer in the soil of each region is 150 kg / mu to 200 kg / mu; The foliar fertilizer contains 0.8 g / L-1.5 g / L of selenium, 0.5 g / L-1.2 g / L of zinc, and has a pH of 6.5-7.

5. At the time of harvest, the selenium content in the tea leaves was 0.25 mg / kg-0.5 mg / kg, and the zinc content was 45 mg / kg-60 mg / kg.

Images