Foliage spraying agent as well as preparation method and application thereof

Abstract

The invention discloses a foliage spraying agent as well as a preparation method and application thereof, and belongs to the technical field of rice planting. The foliage spraying agent comprises zinc salt and nitrogen-fixing cyanobacteria, the mass concentration of the zinc salt is 0.3%-0.6%, and the mass concentration of the nitrogen-fixing cyanobacteria is 10%-20%. In addition, the invention further provides a preparation method of the foliar spraying agent, and the preparation method comprises the following steps: S1, dissolving zinc salt in water to obtain a solution I; s2, adding nitrogen-fixing cyanobacteria into the solution I to obtain the foliage spraying agent. In addition, the invention also provides application of the foliar spraying agent or the foliar spraying agent prepared by the preparation method in rice planting. The foliage spraying agent provided by the invention has a remarkable effect of promoting rice to absorb zinc elements.

Description

Technical Field

[0001] The present invention relates to the field of agricultural biotechnology, and in particular to a foliar spraying agent, a preparation method thereof and an application thereof. Background Art

[0002] Rice is one of the world's most important food crops, but zinc deficiency is widespread. Zinc is an essential trace element for the human body, and zinc deficiency can lead to health problems such as stunted growth and development and weakened immunity. Rice, a staple food, generally contains zinc below the daily zinc requirement (15-25 mg / kg), leading to a serious "hidden hunger" crisis in regions where rice is a staple food.

[0003] Traditional zinc fertilizer application methods (such as soil application) suffer from high soil fixation efficiency, low bioavailability, and high application rates, resulting in resource waste and potential environmental pollution. While foliar zinc spraying can improve zinc absorption, the effectiveness of single zinc fertilizer applications is limited by rice variety, growth period, and environmental conditions, making it difficult to achieve the dual goals of efficient zinc accumulation and stable yield and increased efficiency.

[0004] In recent years, nitrogen-fixing cyanobacteria has been widely used in rice production as a green biofertilizer because of its combined functions of nitrogen fixation, fertilization and secretion of plant hormones. However, existing technologies mostly focus on the single application of nitrogen-fixing cyanobacteria, and insufficient research on the synergistic mechanism between nitrogen-fixing cyanobacteria and zinc fertilizers has resulted in the potential of both in increasing yields and zinc fortification not being fully explored. In addition, existing foliar spraying technology lacks precise adaptation to the type, concentration and application period of zinc fertilizers, making it difficult to balance zinc absorption efficiency, grain enrichment rate and production costs. Therefore, there is an urgent need to develop a new cultivation technology based on the synergistic effect of nitrogen-fixing cyanobacteria and zinc fertilizers to achieve the comprehensive goals of high rice yield, zinc nutrition fortification and environmental friendliness.

[0005] In summary, the development of a foliar spray with simple materials, simple preparation process, and the ability to increase the zinc content in rice grains can not only effectively make up for the shortcomings of existing foliar sprays, but also improve the zinc deficiency in rice grains and significantly increase the zinc content in rice grains, which is of great significance to human zinc nutrition. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above technical deficiencies, provide a foliar spray agent and its preparation method and application, and solve the technical problem of how to significantly increase the zinc content in rice grains in the prior art.

[0007] To achieve the above technical objectives, the technical solution of the present invention provides a foliar spray comprising zinc salt and nitrogen-fixing cyanobacteria, wherein the mass concentration of the zinc salt is 0.3-0.6%, and the mass concentration of the nitrogen-fixing cyanobacteria is 10%-20%.

[0008] In any embodiment, the zinc salt is zinc sulfate heptahydrate.

[0009] In any embodiment, the mass concentration of the zinc sulfate heptahydrate is 0.5%, and the mass concentration of the nitrogen-fixing cyanobacteria is 20%.

[0010] In addition, the present invention also provides a method for preparing the foliar spray, comprising the following steps:

[0011] S1, dissolving zinc salt in water to obtain solution I;

[0012] S2: adding nitrogen-fixing cyanobacteria to the solution I to obtain the foliar spray.

[0013] In addition, the present invention also proposes the use of the foliar spray or the foliar spray prepared by the above preparation method in rice planting.

[0014] In any embodiment, the application comprises the following steps: spraying the foliar spray agent on the plants at the booting stage and the flowering stage respectively.

[0015] In any embodiment, before rice planting, the rice seedlings are transplanted into the field, with 3 to 4 seedlings planted per hole; the total nitrogen application rate is 225 kgN·hm -2 The fertilizers used should be urea with N≥46%, calcium magnesium phosphate fertilizer with P2O5≥12%, and potassium chloride with K2O≥60%; the ratio of nitrogen, phosphorus and potassium fertilizers is 1:0.5:1.

[0016] In any embodiment, 50% of the nitrogen fertilizer is used as base fertilizer, 30% of the nitrogen fertilizer is used as tillering fertilizer, and 20% of the nitrogen fertilizer is used as ear fertilizer.

[0017] In any embodiment, all the phosphorus fertilizer is used as base fertilizer; the potassium fertilizer is applied twice, with the base fertilizer and the ear fertilizer each accounting for 50%.

[0018] In any embodiment, the foliar spray upregulates the expression of OsZIP4 and OsMTP1 genes, and downregulates the expression of OsMT3a, OsMTP9, and OsNAS1 genes.

[0019] Compared with the prior art, the beneficial effects of the present invention include: the foliar spray proposed by the present invention has a good absorption effect on zinc, increases yield and optimizes gene regulation: compared with the limited absorption effect of existing foliar sprays on zinc in rice grains (the zinc absorption efficiency is only 28.6%-35.4%), the foliar spray prepared by this scheme is targeted at the central China region where the soil zinc content is moderate, and its effect of promoting rice to absorb zinc is significant. Through long-term research, the applicant found that compared with the average zinc content of 31.24±2.42 mg / kg in the blank group in this region, the foliar spray of this scheme has an absorption efficiency of zinc in rice grains higher than 70% (the average zinc content of rice grains in Example 1 is 53.88±3.63 mg / kg, and the zinc absorption efficiency of rice grains is 72.46%), so that its content meets the human body's daily zinc requirement threshold of 15-25 mg / kg. In addition, the yield is also increased (16.65% higher than CK). Gene regulation optimization was also carried out, and the expression of zinc transport genes such as OsZIP4 and OsMTP1 were upregulated by 63.43% and 815.28% respectively compared with CK, while the expression of genes such as OsMT3a, OsMTP9, and OsNAS1 were downregulated by 65.69%, 93.45%, and 91.03% respectively compared with CK. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The zinc content in each part (stem, leaf, panicle) of rice 10 days after flowering and at maturity and the zinc transport rate in grains in Example 1, Example 2 and Comparative Examples 1-4 of the present invention are shown. DETAILED DESCRIPTION

[0021] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0023] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0024] This embodiment provides a foliar spray, comprising zinc salt and nitrogen-fixing cyanobacteria, wherein the mass concentration of the zinc salt is 0.3-0.6%, and the mass concentration of the nitrogen-fixing cyanobacteria is 10%-20%. 2+ Producing electrostatic adsorption to capture Zn 2+ , reducing the surface tension of the droplets and achieving the effect of a surfactant, thereby enhancing the adhesion efficiency of zinc fertilizer on the leaf surface and further increasing the zinc content in rice grains.

[0025] In some embodiments, the zinc salt is zinc sulfate heptahydrate.

[0026] In some embodiments, the mass concentration of the zinc sulfate heptahydrate is 0.5%, and the mass concentration of the nitrogen-fixing cyanobacteria is 20%.

[0027] This specific embodiment also provides a method for preparing the above-mentioned foliar spray, comprising the following steps:

[0028] S1, dissolving zinc salt in water to obtain solution I;

[0029] S2: adding nitrogen-fixing cyanobacteria to the solution I to obtain the foliar spray.

[0030] Using this approach, a foliar spray can be quickly prepared with a simple preparation process. Compared to existing foliar sprays, which require multiple pre-preparation stages and result in a lengthy preparation process, the active ingredients of this foliar spray are zinc sulfate heptahydrate and nitrogen-fixing cyanobacteria. This allows for immediate preparation and use of the foliar spray when spraying rice plants is needed, thus avoiding the complex ingredients of existing foliar sprays that require pre-preparation and result in the product being stored for extended periods before use, which reduces its effectiveness. This foliar spray can be prepared and used immediately, allowing the active ingredients in the foliar spray to fully exert their effects, significantly increasing the zinc content of rice grains.

[0031] In addition, this specific embodiment also proposes the use of a foliar spray or a foliar spray prepared by the above preparation method in rice planting, comprising the following steps:

[0032] Before planting rice, transplant the seedlings into the field, planting 3 to 4 seedlings per hole with a row spacing of (24-25) cm × (14-15) cm; the total nitrogen application rate is 225 kg N·hm -2 The fertilizers used should be urea with N≥46%, calcium magnesium phosphate fertilizer with P2O5≥12%, and potassium chloride with K2O≥60%; the ratio of nitrogen, phosphorus and potassium fertilizers is 1:0.5:1; 50% nitrogen fertilizer is used as base fertilizer, 30% nitrogen fertilizer is used as tillering fertilizer, and 20% nitrogen fertilizer is used as ear fertilizer; all phosphorus fertilizer is used as base fertilizer; potassium fertilizer is applied twice, with base fertilizer and ear fertilizer each accounting for 50%.

[0033] The foliar spray is applied to rice plants during the booting and flowering stages, respectively. The foliar spray is applied once during both the booting and flowering stages, with the spray amount applied each time being sufficient to moisten the rice leaves without dripping. Using this solution, the foliar spray, which is easy to apply, can not only moisten the rice leaves and fully exert its effect, but also ensure that the foliar spray remains on the rice leaves for a long time without dripping, thereby reducing the cost of applying the foliar spray. Furthermore, by promoting the absorption and accumulation of zinc in rice during these two critical growth periods, the zinc content in rice grains is increased, allowing the cultivated rice to meet the human daily zinc requirement threshold of 15-25 mg / kg. The foliar spray is applied at 4:00 p.m. in calm weather conditions. Using this solution prevents the foliar spray from reducing its effectiveness due to climatic factors.

[0034] In some embodiments, the foliar spray upregulates the expression of the zinc transport genes OsZIP4 and OsMTP1, and downregulates the expression of the genes OsMT3a, OsMTP9, and OsNAS1.

[0035] The present invention relates to a zinc-nitrogen-fixing cyanobacteria synergistic foliar spray agent and an application method thereof. The present invention significantly increases the zinc content in rice grains by optimizing the foliar spraying strategy and the synergistic application of nitrogen-fixing cyanobacteria. The specific method is as follows: foliar spraying is performed once during the rice booting stage and the flowering stage, and the spraying liquid is a zinc sulfate heptahydrate solution (ZnSO4·7H2O); at the same time, a composite bacterial liquid containing 20% ​​nitrogen-fixing cyanobacteria (such as Anabaena sp. or Chlorella sp.) is applied (complex enzyme activation is required). The nitrogen-fixing cyanobacteria preparation is purchased from Hubei Liangtian Yulu Biotechnology Co., Ltd. and contains a composite bacterial community of Anabaena sp. and Chlorella sp. activated by complex enzymes, and the live bacterial concentration is ≥1.0×10 5 CFU / mL (determined according to GB 20287-2006). The supporting complex enzyme activator is provided by the same supplier, and its main components are amino acids and trace elements. Spray and cover the front and back of the leaves (50L / mu is recommended for field use). The nitrogen-fixing cyanobacteria may capture Zn by electrostatic adsorption through the polysaccharides secreted by extracellular secretions (EPS). 2+ , reducing the surface tension of the droplets, achieving the effect of a surfactant to enhance the adhesion efficiency of zinc fertilizer on the leaf surface, thereby achieving foliar spraying to promote the accumulation and transport of zinc elements in rice and regulate the expression of related zinc genes, thereby increasing the zinc content in rice grains.

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] In the present invention, references to “some embodiments”, “this embodiment”, examples, etc. describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

[0038] If similar descriptions of "first / second" appear in the application documents, the following explanation is added. In the following description, the terms "first\second\third" are merely used to distinguish similar objects and do not represent a specific order of the objects. It can be understood that "first\second\third" can be interchanged with the specific order or sequence where permitted, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein.

[0039] In this embodiment, the term "and / or" is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, object A and / or object B may represent three situations: object A exists alone, object A and object B exist at the same time, and object B exists alone.

[0040] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0041] In the following examples, Example 1 demonstrates the use of a foliar spray comprising a mixture of zinc sulfate heptahydrate and nitrogen-fixing cyanobacteria to increase the zinc content of rice grains; Example 2 and Comparative Examples 1-3 demonstrate the use of a foliar spray comprising a mixture of zinc sulfate heptahydrate and other foliar spray elements or biofertilizers to increase the zinc content of rice grains; and Comparative Example 4 demonstrates the use of a plain water control to increase the zinc content of rice grains. The differences between the foliar sprays in Example 1, Example 2, and Comparative Examples 1-4 are shown in Table 1. Using Examples 1 and 2 as examples, the foliar sprays of this solution and their use in increasing the zinc content of rice grains are described.

[0042] Example 1

[0043] This embodiment provides a foliar spray that effectively increases the zinc content in rice grains. The active ingredients include zinc sulfate heptahydrate and nitrogen-fixing cyanobacteria. The mass concentration of zinc sulfate heptahydrate in the foliar spray of this embodiment is 0.5%; the mass concentration of nitrogen-fixing cyanobacteria is 20% (containing a complex enzyme whose main components are a complex of amino acids and trace elements).

[0044] Example 2

[0045] This embodiment provides a foliar spray that effectively increases the zinc content of rice grains. The active ingredients include zinc sulfate heptahydrate and nitrogen-fixing cyanobacteria. The mass concentration of zinc sulfate heptahydrate in the foliar spray of this embodiment is 0.5%; the mass concentration of nitrogen-fixing cyanobacteria is 10% (containing a complex enzyme whose main components are a complex of amino acids and trace elements).

[0046] Table 1 Differences in foliar sprays among Example 1, Example 2 and Comparative Examples 1 to 4

[0047]

[0048] Examples 1 and 2 also provide a method for preparing a foliar spray, which specifically comprises the following steps:

[0049] S1: Dissolve zinc sulfate heptahydrate in water and stir to obtain solution I;

[0050] S2: Add nitrogen-fixing cyanobacteria to the above solution I, stir and mix evenly to obtain a foliar spray agent.

[0051] The preparation method of the foliar spray of Comparative Examples 1-2 is similar to that of Examples 1 and 2, and specifically comprises the following steps:

[0052] T1: Dissolve zinc sulfate heptahydrate in water and stir to obtain solution I;

[0053] T2: Add sodium metasilicate to the above solution I, stir and mix evenly to obtain the foliar spray agent.

[0054] The preparation method of the foliar spray of Comparative Example 3 specifically comprises the following steps: dissolving zinc sulfate heptahydrate in water and stirring uniformly to obtain solution I; solution I is the foliar spray.

[0055] Test Example 1: Effect of Foliar Spraying on Improving Zinc Content in Rice Grains

[0056] The foliar sprays prepared in Example 1, Example 2, and Comparative Examples 1-4 were applied to rice crops where the zinc content in rice grains needed to be increased. The spraying method of the foliar sprays was as follows:

[0057] Step 1: Before planting rice, select uniformly growing seedlings and transplant them into the field by machine. The spacing between rows and plants is 15cm×25cm, and 3 to 4 seedlings are planted in each hole. The total nitrogen application rate is 225kgN·hm -2 The nitrogen, phosphorus, and potassium fertilizer ratio was 1:0.5:1. 50% of the nitrogen fertilizer was used as base fertilizer, 30% as tillering fertilizer, and 20% as panicle fertilizer. All of the phosphorus fertilizer was used as base fertilizer. Potassium fertilizer was applied twice, with 50% each for base fertilizer and panicle fertilizer. All other rice seedling cultivation, water and fertilizer management, and pest and disease management were carried out in accordance with local agronomic practices. The foliar sprays of each example and comparative example were applied to three rice plantations.

[0058] Step 2: Spray the leaves twice during the booting stage and flowering stage respectively; the amount of each spray should be enough to make the leaves moist but not dripping; choose a windless and rainless day for spraying, and spray at 16:00 in the afternoon.

[0059] Step 3: 10 days after rice flowering and at maturity, rice stalks, leaves, panicles and brown rice were collected (the rice husk was removed from the panicle grains at maturity), and their mass was weighed after drying. The stalks, leaves, panicles and brown rice were separated and crushed through a 100-mesh sieve, and stored in a ziplock bag. The stalks, leaves, panicles and brown rice powders were digested under high pressure and fixed to volume, and the zinc content was determined by inductively coupled plasma mass spectrometry; the foliar sprays prepared in Example 1, Example 2, and Comparative Examples 1-4 were repeated 3 times for rice planting, and the concentration of zinc in the stalks, leaves, panicles and brown rice, as well as the rice yield and other data were measured, and the results were displayed as mean values ​​and standard errors; the foliar sprays prepared in Example 1 and Comparative Example 4 were sprayed on rice. The zinc content of each part (stalk, leaf, panicle) of rice 10 days after flowering and at maturity and the transport rate of grain zinc were as follows: Figure 1 As shown, Figure 1 a The zinc content of each part (stem, leaf, panicle) of rice 10 days after flowering, wherein ZnM2 and ZnM1 are the zinc contents of each part (stem, leaf, panicle) of rice 10 days after flowering in Example 1 and Example 2, respectively, and ZnSi2, ZnSi1, Zn, and CK are the zinc contents of each part (stem, leaf, panicle) of rice 10 days after flowering in Comparative Examples 1-4; Figure 1 b is the zinc content of each part (stalk, leaf, panicle) of rice at maturity in the embodiment, wherein ZnM2 and ZnM1 are the zinc contents of each part (stalk, leaf, panicle) of rice at maturity in Example 1 and Example 2, respectively, and ZnSi2, ZnSi1, Zn, and CK are the zinc contents of each part (stalk, leaf, panicle) of rice at maturity in Comparative Examples 1-4; Figure 1c represents the zinc transport efficiency of rice grains in the examples, where ZnM2 and ZnM1 represent the zinc transport efficiency of rice grains in Examples 1 and 2, respectively, and ZnSi2, ZnSi1, Zn, and CK represent the zinc transport efficiency of rice grains in Comparative Examples 1-4. Sequence numbers 1-3 in Table 2 represent three replicates. The differences in the effects of foliar sprays on rice treated with Example 1, Example 2, and Comparative Examples 1-4 are detailed in Table 2.

[0060] Table 2 Differences in the effects of foliar spraying of Example 1, Example 2, and Comparative Examples 1-4 in the field test

[0061]

[0062]

[0063] The zinc content and actual yield of rice grains obtained by spraying water in comparative example 4 were 31.24 mg / kg and 355.05 kg / 667 m 2 .

[0064] In Example 1, Example 2 and Comparative Examples 1-4, different foliar sprays in combination with 0.5% zinc sulfate heptahydrate were used to prepare the foliar sprays. Foliar spraying was performed once at the heading stage and the maturity stage of rice, respectively. The results showed that the zinc content in the rice stems, leaves, ears and grains was effectively increased, but the zinc transport rate in the grains was reduced ( Figure 1 ); in particular, 20% nitrogen-fixing cyanobacteria, when mixed with 0.5% zinc sulfate heptahydrate to form a foliar spray, can not only significantly increase the zinc content in rice grains (specifically, the zinc content of rice grains in Example 1 reaches 53.88 mg / kg, which meets the human body's daily zinc requirement threshold of 15-25 mg / kg), but also help to increase the actual rice yield, achieving the purpose of improving rice quality and increasing rice yield.

[0065] The foliar spraying of 20% nitrogen-fixing cyanobacteria in Example 1 (average value, 53.88 ± 3.63 mg / kg) significantly increased the zinc content of brown rice. Compared with the blank group of Comparative Example 4 (average value, 31.24 ± 2.42 mg / kg), the foliar spraying of 20% nitrogen-fixing cyanobacteria in Example 1 increased the zinc content of brown rice by 72.46%. Although the other foliar sprays in Comparative Examples 1-3 and Example 2 can increase the zinc content in rice grains, their effects are relatively weak. Therefore, 0.5% zinc sulfate heptahydrate + 20% nitrogen-fixing cyanobacteria has a more significant effect in increasing the zinc content of rice grains. The applicant conducted a field test using the foliar spray prepared in Example 1 and obtained the expected effect. Therefore, the foliar spray of this scheme enables the cultivation of high-zinc rice that meets the daily zinc requirement threshold of the human body in central China, thereby achieving the effect of improving quality and increasing yield.

[0066] Step 4: Harvest rice panicles 10 days after flowering and store at -80°C. Hull the kernels from the panicles on dry ice, and use Trizol to extract and reverse transcribe the resulting grains. PCR analysis is then performed using real-time fluorescence quantitative analysis. Sequence numbers 1-3 in Table 3 represent three replicates. The expression levels of zinc-related genes after foliar spraying in Example 1, Example 2, and Comparative Examples 1-4 are detailed in Table 3.

[0067] Table 3 Differences in expression levels of zinc-related genes in the experimental field treated with foliar sprays of Example 1, Example 2, and Comparative Examples 1-4

[0068]

[0069]

[0070]

[0071] The experimental data showed that in Comparative Example 4, when spraying clean water, the expression levels of OsZIP4, OsMTP1, OsMT3a, OsMTP9 and OsNAS1 genes were all 1±0.00.

[0072] In Example 1, Example 2, and Comparative Examples 1-4, different foliar sprays containing 0.5% zinc sulfate heptahydrate were used to prepare the expression levels of zinc-related genes. Further analysis revealed that Example 1 optimized gene regulation. Example 1 upregulated the expression of zinc transport genes OsZIP4 and OsMTP1 by 63.43% and 815.28%, respectively, compared with Comparative Example 4, and downregulated the expression of genes such as OsMT3a, OsMTP9, and OsNAS1 by 65.69%, 93.45%, and 91.03%, respectively, thereby optimizing the absorption, transport, and storage efficiency of zinc.

[0073] Other beneficial effects include:

[0074] 1) Compared with the complex ingredients of existing foliar sprays, the active ingredients of this foliar spray are zinc sulfate heptahydrate and nitrogen-fixing cyanobacteria. Among them, nitrogen-fixing cyanobacteria may capture Zn through the polysaccharides secreted by extracellular secretions (EPS) through electrostatic adsorption. 2+ , reducing the surface tension of the droplets, achieving the effect of a surfactant to enhance the adhesion efficiency of zinc fertilizer on the leaf surface, thereby achieving foliar spraying to promote the accumulation and transport of zinc elements in rice and regulate the expression of related zinc genes, thereby increasing the zinc content in rice grains.

[0075] 2) Wide range of applications: Compared with existing foliar sprays, which have limited effects on the absorption and accumulation of zinc by rice and thus have a narrow scope of application, this solution has a significant effect on the accumulation of zinc by rice, making the foliar spray prepared by this solution widely applicable to soils with various zinc backgrounds, significantly improving the zinc nutritional quality of rice.

[0076] 3) Low cost: The mass fractions of zinc and nitrogen-fixing cyanobacteria in the foliar spray of this solution are 0.5% and 20%, respectively, which can fully exert the role of rice in absorbing and accumulating zinc. The applicant's experiments found that spraying only zinc fertilizer in the foliar spray will weaken the effect. However, the synergistic application of nitrogen-fixing cyanobacteria and zinc fertilizer will further increase the zinc content in rice grains. Therefore, this solution preferably configures the foliar spray with a concentration of 0.5% zinc and 20% nitrogen-fixing cyanobacteria. This can not only fully increase the zinc content in rice grains, but also effectively increase rice yield and optimize gene regulation, thereby achieving the effect of improving quality and increasing yield.

[0077] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A foliar spray, characterized in that The invention comprises zinc salt and nitrogen-fixing cyanobacteria, wherein the mass concentration of the zinc salt is 0.3-0.6%, and the mass concentration of the nitrogen-fixing cyanobacteria is 10%-20%.

2. The foliar spray according to claim 1, characterized in that The zinc salt is zinc sulfate heptahydrate.

3. The foliar spray according to claim 2, characterized in that The mass concentration of the zinc sulfate heptahydrate is 0.5%, and the mass concentration of the nitrogen-fixing cyanobacteria is 20%.

4. A method for preparing the foliar spray according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, dissolving zinc salt in water to obtain solution I; S2: adding nitrogen-fixing cyanobacteria to the solution I to obtain the foliar spray.

5. Use of the foliar spray according to any one of claims 1 to 3 or the foliar spray prepared by the preparation method according to claim 4 in rice cultivation.

6. The use according to claim 5, characterized in that The following steps are involved: The foliar spraying agent is respectively used for foliar spraying at the booting stage and the flowering stage.

7. The use according to claim 6, characterized in that Before planting rice, transplant the rice seedlings into the field, planting 3 to 4 seedlings per hole; the nitrogen application rate during the whole growth period is 225 kg N·hm -2 The fertilizers used should be urea with N≥46%, calcium magnesium phosphate fertilizer with P2O5≥12%, and potassium chloride with K2O≥60%; the N:P2O5:K2O fertilizer ratio is 1:0.5:

1.

8. The use according to claim 7, characterized in that 50% nitrogen fertilizer is used as base fertilizer, 30% nitrogen fertilizer is used as tillering fertilizer, and 20% nitrogen fertilizer is used as ear fertilizer.

9. The use according to claim 7, characterized in that All phosphorus fertilizers are used as base fertilizers; potassium fertilizers are applied twice, with base fertilizer and ear fertilizer each accounting for 50%.

10. The use according to claim 6, characterized in that The foliar spray upregulates the expression of zinc transport genes OsZIP4 and OsMTP1, and downregulates the expression of antagonistic genes OsMT3a, OsMTP9, and OsNAS1.

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