Monodisperse nano calcium carbonate-based foliar calcium fertilizer as well as preparation method and application thereof

Abstract

The invention discloses a monodisperse nano calcium carbonate based foliar calcium fertilizer, which is mainly prepared from the following raw materials: 1 to 20 parts of monodisperse nano calcium carbonate filter cake, 0.05 to 0.9 part of ethyoxyl modified polytrisiloxane, 0.01 to 0.8 part of modified casein, 0.01 to 0.8 part of enzyme, 0.05 to 0.9 part of sugar alcohol and 10 to 180 parts of water. The raw materials are mixed in two steps according to a certain sequence, stirred and dispersed to obtain the novel monodisperse nano calcium carbonate based foliar calcium fertilizer, and the novel monodisperse nano calcium carbonate based foliar calcium fertilizer is diluted with water until the solid content of calcium carbonate is 0.5%-2% and then used for foliar calcium supplement of various crops and fruit and vegetable crops. The novel foliar calcium fertilizer is safe and non-toxic, can be directly sprayed to the foliar surfaces and fruit surfaces of crops, fruits and vegetables, is used for planting grain crops such as rice, wheat and sorghum and non-grain crops such as cassava, sugarcane, fruits and vegetables, effectively guarantees calcium absorption and utilization of the crops, and achieves the effect of increasing both production and income; the yield of fruits and vegetables can be increased to a certain extent, and certain insect-repelling and disease-preventing effects are achieved.

Description

Technical Field

[0001] The invention belongs to the field of crop foliar fertilizers, and in particular relates to a novel monodisperse nano calcium carbonate-based foliar calcium fertilizer and a preparation method and application thereof. Background Art

[0002] Fruits, vegetables, sugarcane and other non-food crops as well as food crops have a large demand for calcium. The negative impact of calcium deficiency on crops is very significant, and a series of problems such as cracked fruits, diseased fruits, fruit drop, and crop yield reduction will occur. How to conveniently supplement calcium is an urgent problem to be solved in modern agriculture. On the other hand, there are harsh conditions for calcium in the soil to be absorbed and utilized by plants. Crops have no absorption capacity for traditional solid calcium salts. Calcium fertilizers in the soil often need to be converted into water-soluble calcium ions through ion exchange before they can be absorbed and utilized by crop roots. Since the solubility of calcium salts corresponding to most anion types in the soil is not high, even soluble calcium fertilizers are easily fixed by other anions in the soil and become ineffective after root application. In addition, the type and state of calcium fertilizers, the content of other elements such as nitrogen, phosphorus and potassium, and the pH value of the soil will affect the absorption and utilization of calcium ions by crops. For example, in areas with higher pH values, the calcium ion exchange capacity becomes weaker, and the ability of crops to absorb calcium ions is poor; and areas with more macroelements such as nitrogen, phosphorus and potassium in the soil will also inhibit the absorption of calcium ions by crops. In addition, studies have shown that the transport of calcium ions in plants is much more difficult than that of other nutrients. Combined with the long distance of transport from the root absorption system to the leaves and fruits, calcium deficiency at the top of plants becomes the norm. Summary of the invention

[0003] In view of the deficiencies of the above-mentioned prior art, the present invention provides a novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer. The foliar calcium fertilizer is non-toxic, safe and environmentally friendly. When used, it can be directly sprayed on the leaves or fruit surfaces of fruits, vegetables and crops to meet the calcium needs of crops during their growth. When used in fruit planting, it can effectively inhibit fruit cracking and fruit drop, increase the fullness of fruit, increase the calcium content and yield of fruits, and significantly improve the taste and quality of fruits; when used in the planting of crops such as vegetables, sugar cane, and rice, it can significantly improve the quality and yield of crops.

[0004] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0005] A novel monodisperse nano calcium carbonate-based foliar calcium fertilizer comprises the following raw materials by weight: 1-20 parts of monodisperse nano calcium carbonate filter cake, 0.05-0.9 parts of ethoxy-modified polytrisiloxane, 0.01-0.8 parts of modified casein, 0.01-0.8 parts of enzyme, 0.05-0.9 parts of sugar alcohol, and 10-180 parts of water.

[0006] Furthermore, the mass of the monodisperse nano-calcium carbonate filter cake is 15 to 75 times, preferably 15 to 25 times, that of the ethoxy-modified polytrisiloxane.

[0007] Furthermore, the mass of the water is 2 to 60 times, preferably 2 to 11 times, that of the monodisperse nano-calcium carbonate filter cake.

[0008] Furthermore, the mass of the monodisperse nano calcium carbonate filter cake is 18.75 to 50 times, preferably 25 to 50 times, that of the modified casein.

[0009] Furthermore, the mass of the monodisperse nano-calcium carbonate filter cake is 25 to 100 times that of the enzyme, preferably 75 to 100 times.

[0010] Furthermore, the mass of the monodisperse nano calcium carbonate filter cake is 20 to 50 times, preferably 20 to 30 times, that of the sugar alcohol.

[0011] According to the above scheme, the characteristics of the monodisperse nano calcium carbonate filter cake are as follows: the moisture content of the filter cake is 35% to 40%, the calcium carbonate particles are cubic or nearly spherical, the average particle size is between 20 and 100 nm, and the particles with a particle size greater than 100 nm account for less than 5%; the particle surface is clean, in a monodisperse state, has a small surface energy, and its specific surface area is less than 25m 2 / g, the specific surface area is preferably 20 to 23m 2 / g; the content of harmful metal elements such as cadmium in calcium carbonate is less than 200ppm; the monodisperse nano calcium carbonate filter cake can be stirred and dispersed in the aqueous solution without adding any chemical dispersant, and can remain stably suspended. Specifically, the monodisperse nano calcium carbonate filter cake is dispersed in water to obtain a suspension; when the solid content of the suspension is 5% to 30%, it can be stably suspended for more than 14 hours; when the solid content of the suspension is 2%, it can be stably suspended for more than 4 hours.

[0012] According to the above scheme, the method for preparing the monodisperse nano calcium carbonate filter cake comprises the following steps:

[0013] S1. Prepare calcium carbonate cooked slurry by calcination, digestion, carbonization and other processes. The calcination process is as follows: select limestone with uniform grain size and harmful heavy metal content of less than 400ppm such as cadmium, lead and chromium as raw material, adopt calcination temperature matching the grain size, and obtain quicklime with ideal activity. The activity of quicklime is between 250 and 300mL (4mol / L HCl, 40±1℃, 10min), and the uniformity and consistency are good; the digestion process is as follows: digest the quicklime obtained by the above calcination in hot water at 50 to 90℃ to obtain lime milk; the aging and impurity removal process is as follows: age the lime milk slurry obtained by digestion for 24 to 48h, and obtain refined raw slurry after filtering and impurity removal; the carbonization process is as follows: add water to the refined raw slurry to adjust the solid content to 5% to 8%, and then carbonize it. The starting temperature of carbonization is 10 to 20℃, and the CO2 content is 20% to 40%. Carbonize until the slurry pH reaches 7.5 to 9.0.

[0014] Finish carbonization and obtain calcium carbonate cooked slurry;

[0015] The calcium carbonate particles in the calcium carbonate cooked slurry are nearly spherical or chain-shaped in shape, the average particle size of the nearly spherical particles is 10 to 60 nm, and the average width of the chain-shaped particles is 10 to 60 nm;

[0016] S2. Add inorganic salt crystal surface reconstructor and organic crystal surface reconstructor to the calcium carbonate slurry obtained in S1, and then keep it warm at 120-140°C for 1-4 hours to obtain a calcium carbonate suspension. Among them, the inorganic crystal surface reconstructor is one or more inorganic salts such as sodium silicate, sodium chloride, aluminum chloride, zinc sulfate, etc., and the amount used is 0.5% to 3% of the dry mass of calcium carbonate; the organic crystal surface reconstructor is one or more organic substances such as ethanol, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl alcohol, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, disodium ethylenediaminetetraacetic acid, etc., and the amount used is 1% to 5% of the dry mass of calcium carbonate;

[0017] S3. The calcium carbonate suspension obtained in S2 is filtered and dehydrated to obtain a calcium carbonate filter cake. The water content of the filter cake is controlled between 35% and 40%, which is a monodisperse nano calcium carbonate filter cake. At this time, it meets the following requirements: "The calcium carbonate particles are cubic or nearly spherical, with an average particle size between 20 and 100 nm, and particles with a particle size greater than 100 nm account for less than 5%; the particle surface is clean, monodisperse, has a small surface energy, and its specific surface area is less than 25 m 2 / g; the content of harmful metal elements such as cadmium in calcium carbonate is less than 200ppm; it can be dispersed after stirring in an aqueous solution without adding any chemical dispersant and remain stably suspended.

[0018] According to the above scheme, the sugar alcohol includes one or more of xylitol, ribitol, mannitol, sorbitol, maltitol, erythritol and lactitol.

[0019] According to the above scheme, the modified casein is a milky white viscous liquid with a solid content of 15% to 25%, a viscosity (20° C.) greater than 100 mPa·s, and a pH value (10% aqueous solution) of 7 to 8.

[0020] According to the above scheme, the enzyme is a commercially available agricultural enzyme, which contains agricultural biological agents, polysaccharides, amino acids and other ingredients.

[0021] The preparation method of the novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer comprises the following steps:

[0022] (1) According to the raw materials and mass proportions of the foliar calcium fertilizer described in the present invention, 1 to 20 parts of monodisperse nano calcium carbonate filter cake, 0.05 to 0.9 parts of ethoxy-modified polytrisiloxane, 0.01 to 0.8 parts of modified casein, 0.01 to 0.8 parts of enzyme, 0.05 to 0.9 parts of sugar alcohol, and 10 to 180 parts of water are prepared;

[0023] (2) placing the monodisperse nano-calcium carbonate filter cake in a small amount of water at a temperature of 5 to 30° C. (the weight of the “small amount of water” is 1 to 2 times the weight of the monodisperse nano-calcium carbonate filter cake in the formula) and dispersing it in a high-speed disperser at room temperature at a linear speed of 80 to 120 m / min for 15 to 40 min;

[0024] (3) After the stirring in step (2) is completed, the remaining other raw materials and excess water are added, and the mixture is dispersed in a high-speed disperser at a linear speed of 80 to 120 m / min for 15 to 30 min to obtain the novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer of the present invention.

[0025] When the novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer of the present invention is used, it can be further diluted according to different application objects. It is recommended to add water to dilute it to a solid content of calcium carbonate of 0.5% to 2% and then spray it directly.

[0026] According to the above scheme, the food crops described in the present invention include rice, wheat, sorghum, etc.; the non-food crops include fruits such as apples, citrus, pears, plums, mangoes, cherry tomatoes, grapes, dragon fruit, oranges, loquats, apricots, kiwis, grapefruits, pomegranates, green dates, guavas, peaches, etc., vegetables such as baby cabbages, cabbages, loofahs, bitter melons, pumpkins, lettuces, and cassava, sugarcane, etc.

[0027] The novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer of the present invention can be used for crop planting, and the application method is as follows: in rainless and dry weather, the foliar calcium fertilizer of the present invention is diluted and sprayed on the leaves of food crops or non-food crops without specifically avoiding fruits. During the growth of crops, it needs to be sprayed 2 to 4 times, and the time interval between two adjacent sprays is 15 to 20 days.

[0028] The present invention selects limestone with uniform grain size and harmful heavy metal content of less than 400ppm such as cadmium, lead, chromium, etc. as the raw material for preparing monodisperse nano calcium carbonate filter cake, and then adopts a calcination temperature matching the grain size to obtain quicklime with moderate and uniform activity, which is digested and carbonized to obtain calcium carbonate slurry. The limestone with uniform grain size is used to adjust the lime activity through the limestone calcination process to avoid partial raw burning and partial overburning caused by porphyritic grains; the lime with good uniformity and moderate activity is conducive to the control of the digestion reaction, and the uniform lime milk with controllable properties is obtained, and then the control of the later carbonization process is realized, so as to obtain calcium carbonate slurry with expected particle size and grain morphology. The content of harmful heavy metals such as cadmium, lead, chromium, etc. in the limestone is less than 400ppm, which can ensure that the content of harmful heavy metals in the prepared monodisperse nano calcium carbonate filter cake is less than 200ppm.

[0029] After the carbonization is completed, there is a process step of reconstructing the surface of the grains, which is to promote the reconstruction of the surface of the grains by adding inorganic surface reconstruction agents and organic surface reconstruction agents and keeping them warm at a certain temperature, so as to make the crystals more complete, the particle surface smoother, and reduce the surface energy, which is conducive to dispersion. Among them, the role of the inorganic surface reconstruction agent is to promote crystal development, repair defects, and make the crystals more complete; the role of the organic surface reconstruction agent is to adjust the surface potential of the particles, control the mutual repulsion of the grains in water, and avoid adhesion during the crystal repair process. The present invention controls the average particle size of the calcium carbonate particles to 20 to 100nm by controlling the temperature and time of the grain surface reconstruction, and is in a highly monodisperse state. This form of calcium carbonate particles can ensure visible light diffraction and transmission, so it does not affect the photosynthesis and surface coloring of crop leaves and fruits, and can effectively absorb ultraviolet light that is harmful to plants (for example, the foliar calcium fertilizer of the present invention is diluted to a solid content of calcium carbonate of 1% and sprayed to form a film, and the absorption of ultraviolet rays can reach more than 80%, and the absorption of visible light is less than 15%). The monodisperse nano calcium carbonate slurry obtained by reconstructing the surface of the crystal particles is then subjected to filter pressing or centrifugation to obtain a monodisperse calcium carbonate filter cake of the desired particle size. Filter pressing and centrifugation can discharge excess water, which is beneficial to the processing and transportation of calcium carbonate, and also rapidly reduce other soluble ions present in the solution during the production process, so as to achieve the purpose of not affecting and interfering with the use and performance of the foliar calcium fertilizer of the present invention.

[0030] On the basis of the above, the present invention uses the monodisperse nano calcium carbonate filter cake as the main raw material, and is compounded with other raw materials and dispersed in water, thereby obtaining the foliar calcium fertilizer of the present invention. The monodisperse nano calcium carbonate filter cake maintains 35% to 40% of water, and maintains a water film and a double electric layer structure between the solid calcium carbonate particles, which can ensure that the surface state and repulsion of the calcium carbonate particles are not destroyed to the greatest extent, and no agglomeration occurs, so that it can be quickly redispersed in the aqueous solution when the disperser assists in stirring, and maintains a stable suspension.

[0031] The present invention processes calcium carbonate into cubic and nearly spherical nanoparticles in a monodisperse state, and utilizes the hydroxyl and carboxyl groups in the long carbon chain fatty acid polymer, the main component in the outermost layer of the leaf, the cuticle, to bond with the calcium ions on the surface of the nano calcium carbonate, so that the calcium ions can effectively penetrate the cuticle and enter the leaf; on the other hand, the small size characteristics of the nano and submicron calcium carbonate particles are utilized to establish a calcium ion fast channel through the pores (diameter of about 10 to 20 μm) on the surface of the leaf, so that the plant can directly absorb solid calcium carbonate as calcium fertilizer through the leaf surface, forming a key technology for direct and rapid calcium supplementation through the leaf surface. In addition, the abundant sugar alcohols on the surface of the fruit can be combined with the free calcium ions on the surface of the nano calcium carbonate and directly transported to the inside of the fruit to form fruit acid calcium, thereby increasing the calcium content in the fruit pulp; at the same time, the sugar alcohols in the foliar calcium fertilizer formula have penetration and wetting functions, which can increase the calcium ion transport effect of the leaf surface.

[0032] The new foliar calcium fertilizer of the present invention can quickly form a light white protective film on the leaf surface of crops, and use nano calcium carbonate particles to trigger the active oxygen wave outside the plant cell membrane to induce the plant to produce "systemic acquired resistance" and "systemic acquired adaptability" responses, thereby obtaining a mechanism for coordinating the balance between plant growth and resistance, so that the crops sprayed with the new foliar calcium fertilizer of the present invention have excellent stress resistance and effectively resist pests and diseases. Due to the special particle size and dispersibility design of calcium carbonate, the protective film does not affect the transmission of visible light, and therefore does not affect the photosynthesis of the fruit; the present invention utilizes the ultraviolet light absorption and infrared radiation characteristics of calcium carbonate, combined with the particle size design of the present invention, can effectively reduce ultraviolet burns to crops and their fruits, reduce the temperature of crops and their fruits, and form effective physical and optical protection.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer of the present invention is safe, environmentally friendly, non-toxic, and can be used for the production of food crops such as rice, wheat, and sorghum, as well as non-food crops such as cassava, sugarcane, fruits, and vegetables. It can effectively ensure the calcium absorption and utilization of crops, meet the calcium demand of crops during growth, and increase production and income. It can effectively inhibit fruit cracking and fruit drop, increase the fullness of fruit, increase the calcium content and yield of fruits, and significantly improve the taste and quality of fruits.

[0035] 2. The novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer of the present invention can be particularly used for the cultivation of fruits (such as apples, pears, plums, oranges, pitaya, mangoes and other fruits). When used, it can be directly sprayed onto the leaves of crops without specifically avoiding the fruits. It can increase the yield while having good physical insect prevention and repellent effects, and can significantly improve the disease resistance and insect resistance of fruits and reduce diseased and worm-infested fruits.

[0036] 3. The novel foliar calcium fertilizer of the present invention can effectively absorb ultraviolet rays, radiate infrared rays, and reduce the temperature of crops. It has no effect on the passage of visible light and does not interfere with the normal photosynthesis of fruit and vegetable crops, and can be used for fruit and vegetable planting. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a scanning electron microscope photograph of calcium carbonate particles in the calcium carbonate slurry prepared in Example 1;

[0038] Figure 2 This is a scanning electron microscope photograph of the monodisperse nano-calcium carbonate prepared in Example 1;

[0039] Figure 3 The effect diagram of using the new foliar calcium fertilizer prepared in Example 1 on baby cabbage and the control effect diagram of spraying clean water;

[0040] Figure 4 This is a scanning electron microscope photograph of calcium carbonate particles in the calcium carbonate slurry prepared in Example 2;

[0041] Figure 5 This is a scanning electron microscope photograph of the monodisperse nano-calcium carbonate prepared in Example 2;

[0042] Figure 6 The effect diagram of the new foliar calcium fertilizer prepared in Example 2 on rice and the control effect diagram of spraying with clear water;

[0043] Figure 7 This is a scanning electron microscope photograph of calcium carbonate particles in the calcium carbonate slurry prepared in Example 3;

[0044] Figure 8 This is a scanning electron microscope image of the monodisperse nano-calcium carbonate obtained in Example 3;

[0045] Fig. 9 This is a diagram showing the effect of using the novel foliar calcium fertilizer prepared in Example 3 on sugarcane;

[0046] Fig.10 This is a scanning electron microscope photograph of calcium carbonate particles in the calcium carbonate slurry prepared in Example 4;

[0047] Fig.11 This is a scanning electron microscope image of the monodisperse nano-calcium carbonate obtained in Example 4;

[0048] Fig.12 This is a diagram showing the effect of using the new foliar calcium fertilizer prepared in Example 4 on pears;

[0049] Fig.13 This is a scanning electron microscope photograph of calcium carbonate particles in the calcium carbonate slurry prepared in Example 5;

[0050] Fig.14This is a scanning electron microscope image of the monodisperse nano-calcium carbonate obtained in Example 5;

[0051] Fig.15 This is a diagram showing the effect of using the new foliar calcium fertilizer prepared in Example 5 on apples;

[0052] Fig.16 This is a scanning electron microscope image of the calcium carbonate prepared in Comparative Example 1;

[0053] Fig.17 This is a diagram showing the effect of using the foliar calcium fertilizer prepared in Comparative Example 1 on baby cabbage;

[0054] Fig.18 This is a diagram showing the effect of using the foliar calcium fertilizer prepared in Comparative Example 2 on rice;

[0055] Fig.19 This is a scanning electron microscope image of calcium carbonate obtained in Comparative Example 3;

[0056] Fig. 20 It is a comparison diagram of the effect of calcium carbonate dispersed in water of the embodiment and the comparative example;

[0057] Fig.21 This is a diagram showing the effect of using the foliar calcium fertilizer made of calcium carbonate in Comparative Example 3 on pears;

[0058] Fig. 22 This is a diagram showing the effect of using the foliar calcium fertilizer made of calcium carbonate in Comparative Example 4 on pears;

[0059] Fig.23 This is a diagram showing the effect of using foliar calcium fertilizer made from calcium carbonate in Comparative Example 5 on apples. Specific implementation methods

[0061] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0062] In the following examples, the ethoxy-modified polytrisiloxane is a commercially available product purchased from GE Silicones USA, model Silwet, with an active ingredient content of more than 98%.

[0063] In the following embodiments, the modified casein is an emulsion obtained by dissolving commercially available casein in weak alkaline water at 50-65°C, having a milky white viscous liquid appearance, a solid content of 20.0±2.0%, a viscosity (20°C) greater than 100mPa·s, and a pH value (10% aqueous solution) of 7-8. Casein was purchased from Gansu Hualing Dairy Co., Ltd., model: edible casein.

[0064] In the following embodiments, the enzyme is an agricultural enzyme, the main components of which are agricultural biological agents, polysaccharides, amino acids, etc. It is a commercially available product purchased from Jining Alida Bioengineering Co., Ltd., model: MLQ-Plant Enzyme.

[0065] In the following embodiments, the sugar alcohol is one or more of xylitol, ribitol, mannitol, sorbitol, maltitol, erythritol and lactitol, etc.; the sugar alcohols are all commercially available products, and the effective ingredients are greater than 70%.

[0066] Example 1

[0067] The present embodiment provides a novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer, which is prepared from the following raw materials in parts by weight: 1 part of monodisperse nano-calcium carbonate filter cake, 0.05 parts of ethoxy-modified polytrisiloxane, 0.02 parts of modified casein, 0.01 parts of enzyme, 0.05 parts of mannitol, and 60 parts of clean water.

[0068] The preparation method of the novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer described in this embodiment is as follows: according to the above raw materials and mass fractions, 1 part of monodisperse nano-calcium carbonate filter cake is placed in 2 parts of clean water, and stirred for 40 minutes with a high-speed disperser at a stirring line speed of 80m / min, and then 0.05 parts of ethoxy-modified polytrisiloxane, 0.02 parts of modified casein, 0.01 parts of enzyme, 0.05 parts of mannitol and the remaining 58 parts of clean water are added according to the above formula, and stirring is continued at a stirring line speed of 80m / min for 20 minutes to obtain the foliar calcium fertilizer described in this embodiment, and the solid content of calcium carbonate is about 1%.

[0069] In this embodiment, the preparation steps of the monodisperse nano calcium carbonate filter cake are as follows:

[0070] S1. Prepare calcium carbonate slurry by calcination, digestion, carbonization and other processes. The calcination process is as follows: select limestone with a grain size of 0.2-0.5 mm and a content of harmful heavy metals such as cadmium, lead, chromium and less than 400 ppm as raw material, adopt a calcination temperature of 900°C, calcine for 2 hours, and obtain quicklime with ideal activity; the digestion process is as follows: digest the quicklime obtained by the above calcination with water at 50°C to obtain lime milk, and then remove impurities after aging for 48 hours to obtain refined raw slurry; the carbonization process is as follows: add water to the refined raw slurry obtained by digestion to adjust the solid content to 5%, and then carbonize it. The starting temperature of carbonization is 10°C, the CO2 content is 40%, and the slurry is carbonized until the pH value reaches 7.5-8.0, then the carbonization is terminated to obtain calcium carbonate slurry;

[0071] From the scanning electron microscope photos (see Figure 1 ) It can be observed that the calcium carbonate particles in the obtained cooked slurry are nearly spherical and short rod-shaped particles, and the average particle size is about 15nm;

[0072] S2. The calcium carbonate slurry obtained in S1 was added with 0.5% aluminum chloride, 2% polyvinyl alcohol, 2% polyvinyl pyrrolidone and 1% sodium dodecylbenzene sulfonate on a dry basis of calcium carbonate, and the mixture was kept at 140°C for 1.0h to obtain a calcium carbonate suspension;

[0073] S3. The calcium carbonate suspension obtained in S2 is filtered and dehydrated to obtain a calcium carbonate filter cake. The moisture content of the filter cake is controlled between 35% and 40%, that is, monodisperse nano calcium carbonate. At this time, an appropriate amount of the filter cake is dried at 105°C and then tested and analyzed for composition, specific surface area, micromorphology and particle size. The composition and specific surface area tests are carried out according to the "Calcium Carbonate Analysis Method" (GB / T19281-2014) standard, and the micromorphology and particle size tests are carried out according to the "Nano Calcium Carbonate" (GB / T 19590-2023) standard. The contents of harmful impurities such as cadmium, lead, barium, mercury, and arsenic in the obtained monodisperse nano calcium carbonate are all less than 0.0002%, and the total content of harmful impurities is less than 200ppm; the specific surface area is about 24.66m 2 / g; from the scanning electron microscope photo (see Figure 2 ) It can be clearly seen that the average particle size of the monodisperse nano-calcium carbonate particles obtained is about 30nm, the particles are nearly spherical and cubic, and the surface is flat and clean. The monodisperse nano-calcium carbonate filter cake obtained is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 4 hours. It can still be stably suspended (see Fig. 20 ).

[0074] When used for foliar spraying of baby cabbage: During the rosette stage, the foliar calcium fertilizer prepared in this embodiment is directly and evenly sprayed on the leaves of baby cabbage. After spraying, take photos to record the growth status of the whole baby cabbage plant, and observe it regularly every week thereafter. The baby cabbage needs to be sprayed 1 to 2 times before entering the heading stage. If the rainfall reaches 120 mm or more for more than 3 days, it needs to be sprayed again after the rain.

[0075] The effect of using the foliar calcium fertilizer of this embodiment on baby cabbage is shown in the figure below. Figure 3 shown.

[0076] The results of the calcium content test on the aerial part of the baby cabbage after spraying the foliar calcium fertilizer of this embodiment (set-1) and after spraying with clean water (ck-1) are shown in Table 1. The calcium content in the aerial part increased by 22.87% after spraying the new foliar calcium fertilizer of this embodiment.

[0077] Example 2

[0078] The present embodiment provides a novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer, which is prepared from the following raw materials in the following mass proportions: 20 parts of monodisperse nano-calcium carbonate filter cake, 0.9 parts of ethoxy-modified polytrisiloxane, 0.5 parts of modified casein, 0.8 parts of enzyme, 0.9 parts of xylitol, and 40 parts of clean water.

[0079] The preparation method of the novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer described in this embodiment is as follows: according to the above raw materials and mass fractions, 20 parts of monodisperse nano-calcium carbonate filter cakes are placed in 28 parts of clean water, and stirred for 40 minutes with a high-speed disperser at a stirring line speed of 100m / min, and then 0.9 parts of ethoxy-modified polytrisiloxane, 0.5 parts of modified casein, 0.8 parts of enzyme, 0.9 parts of xylitol and the remaining 12 parts of clean water are added according to the above formula, and stirring is continued at a stirring line speed of 120m / min for 15 minutes to obtain the foliar calcium fertilizer described in this embodiment, and the solid content of calcium carbonate is about 20%. Among them, the preparation steps of the monodisperse nano calcium carbonate filter cake are different from those of Example 1 in that the digestion temperature of step S1 is 90°C, the aging time is 24h, the carbonization starting temperature during the carbonization process is 20°C, the CO2 content is 33%, and the carbonization is terminated when the pH reaches 7.5 to 8.5. After the carbonization is completed, the microscopic morphology of the calcium carbonate particles in the obtained cooked slurry is characterized, and it can be observed that the calcium carbonate particles are nearly spherical or short rod-shaped, with an average particle size of about 31nm (see Figure 4 ); Step S2: During the grain surface reconstruction process, 1.5% sodium chloride, 0.5% zinc sulfate, 1% sodium silicate, 0.5% ethanol and 0.5% disodium ethylenediaminetetraacetate were added to the calcium carbonate dry basis mass, and the mixture was kept warm at 130°C for 3.0h.

[0080] The same test method as in Example 1 was used to test and analyze the composition, specific surface area, microscopic morphology and particle size of the monodisperse nano calcium carbonate filter cake obtained in this example. The contents of harmful impurities such as cadmium, lead, barium, mercury and arsenic in the monodisperse nano calcium carbonate were all less than 0.0002%, and the total content of harmful impurities was less than 200 ppm; the specific surface area was about 19.82 m 2 / g; From the SEM photos (see Figure 5 ) It can be clearly seen that the average particle size of the monodisperse nano calcium carbonate particles obtained is about 66nm, the particles are cubic, and the surface is flat and clean. The monodisperse nano calcium carbonate filter cake obtained is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 4 hours. It can still be stably suspended (see Fig. 20 ).

[0081] Application test: The novel foliar calcium fertilizer prepared by the present embodiment is used for rice planting, specifically: in the tillering stage and the growth period, from late March to early April and June each year, in rainless weather, the novel foliar calcium fertilizer is diluted 10 times (the solid content of calcium carbonate is about 2%) and sprayed on the rice leaves, and the growth status of the whole rice plant is recorded by taking a photo after spraying, and then regularly observed once a month. If the rainfall reaches 120 mm or more for more than 3 days within less than 24 hours after spraying, it is necessary to spray again after the rain.

[0082] The effect of using the foliar calcium fertilizer of this embodiment on rice is shown in the figure below: Figure 6 shown.

[0083] The results of the calcium content test on the edible part of rice after spraying the foliar calcium fertilizer of this embodiment (set-2) and after spraying with clean water (ck-2) are shown in Table 1. The calcium content in the edible part of rice increased by 15.53% after spraying the new foliar calcium fertilizer of this embodiment.

[0084] Example 3

[0085] The present embodiment provides a novel monodisperse nano-calcium carbonate-based foliar calcium fertilizer, which is prepared from the following raw materials in parts by weight: 15 parts of monodisperse nano-calcium carbonate filter cake, 0.2 parts of ethoxy-modified polytrisiloxane, 0.8 parts of modified casein, 0.2 parts of enzyme, 0.6 parts of erythritol, and 45 parts of clean water.

[0086] The preparation method of the novel foliar calcium fertilizer described in this embodiment is as follows: according to the above raw materials and mass fractions, 15 parts of monodisperse nano calcium carbonate filter cake are placed in 20 parts of clean water, and stirred for 30 minutes with a high-speed disperser at a stirring line speed of 90m / min, and then 0.2 parts of ethoxy-modified polytrisiloxane, 0.8 parts of modified casein, 0.2 parts of enzyme, 0.6 parts of erythritol and the remaining 25 parts of clean water are added according to the above formula, and stirring is continued at a stirring line speed of 110m / min for 25 minutes to obtain the foliar calcium fertilizer described in this embodiment, and the solid content of calcium carbonate is about 15%. The preparation steps of the monodisperse nano-calcium carbonate filter cake are different from those in Example 1 in that the solid content of the refined raw pulp in the carbonization process of step S1 is 6%, the carbonization starting temperature is 15°C, the CO2 content is 35%, and the carbonization is terminated when the pH reaches 8.0-9.0. After the carbonization is completed, the microscopic morphology of the calcium carbonate particles in the obtained cooked pulp is characterized, and it can be observed that the calcium carbonate particles are short-chain with an average width of about 21 nm (see Figure 7 ); Step S2: During the grain surface reconstruction process, 0.2% zinc sulfate, 0.5% sodium silicate, 1.4% polyethylene glycol and 0.6% hexadecyltrimethylammonium bromide were added to the calcium carbonate dry basis mass and kept at 120°C for 6h.

[0087] The composition, specific surface area, microscopic morphology and particle size of the monodisperse nano calcium carbonate filter cake obtained in this embodiment were tested and analyzed by the same test method as in Example 1. The contents of harmful impurities such as cadmium, lead, barium, mercury and arsenic in the monodisperse nano calcium carbonate were all less than 0.0002%, and the total content of harmful impurities was less than 200 ppm; the specific surface area was about 22.82 m 2 / g; From the SEM photos (see Figure 8) It can be clearly seen that the average particle size of the monodisperse nano calcium carbonate particles obtained is about 45nm, the particles are cubic, and the surface is flat and clean. The monodisperse nano calcium carbonate filter cake obtained is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 4 hours. It can still be stably suspended (see Fig. 20 ).

[0088] Application test: The new foliar calcium fertilizer prepared in this embodiment is used for sugarcane planting, specifically: during the tillering and growth period, from late March to early April and June each year, in rainless weather, the new foliar calcium fertilizer is diluted 10 times (solid content of calcium carbonate is about 1.5%) and sprayed on the sugarcane leaves. After spraying, the growth status of the whole sugarcane plant is recorded by taking pictures, and then regularly observed once a month. If the rainfall reaches 120 mm or more for more than 3 days within less than 24 hours after spraying, it is necessary to spray again after the rain.

[0089] The effect of using the foliar calcium fertilizer of this embodiment on sugarcane is shown in the figure below. Fig. 9 shown.

[0090] The results of the calcium content test on the edible part of sugarcane after spraying the foliar calcium fertilizer of this embodiment (set-3) and after spraying with clean water (ck-3) are shown in Table 1. After spraying the new foliar calcium fertilizer of this embodiment, the calcium content in the edible part of sugarcane increased by 11.11%.

[0091] Example 4

[0092] The present embodiment provides a novel foliar calcium fertilizer, which is prepared in the following weight ratios: 5 parts of monodisperse nano calcium carbonate filter cake, 0.3 parts of ethoxy-modified polytrisiloxane, 0.2 parts of modified casein, 0.05 parts of enzyme, 0.1 parts of lactitol, and 55 parts of clean water.

[0093] The preparation method of the novel foliar calcium fertilizer described in this embodiment is as follows: according to the above raw materials and mass fractions, 5 parts of monodisperse nano calcium carbonate filter cake are placed in 10 parts of clean water, and stirred for 15 minutes with a high-speed disperser at a stirring line speed of 120m / min, and then 0.3 parts of ethoxy-modified polytrisiloxane, 0.2 parts of modified casein, 0.05 parts of enzyme, 0.1 parts of lactitol and the remaining 45 parts of clean water are added according to the above formula, and stirring is continued at a stirring line speed of 90m / min for 30 minutes to obtain the foliar calcium fertilizer described in this embodiment, and the solid content of calcium carbonate is about 5%. Among them, the preparation steps of the monodisperse nano calcium carbonate filter cake are different from those in Example 1 in that the digestion temperature in step S1 is 70°C, the aging time is 36h, the solid content of the refined raw pulp during the carbonization process is 7%, the carbonization starting temperature is 12°C, the CO2 content is 30%, and the carbonization is terminated when the pH reaches 8.0-8.5. After the carbonization is completed, the microscopic morphology of the calcium carbonate particles in the obtained cooked pulp is characterized, and it can be observed that the calcium carbonate particles are chain-shaped with an average width of about 25nm (see Fig.10 ); Step S2: During the grain surface reconstruction process, 0.5% sodium silicate and 1.5% aluminum chloride, 0.5% sodium dodecylbenzene sulfonate and 2% sodium dodecyl sulfate were added on a dry basis of calcium carbonate and kept warm at 140°C for 2h.

[0094] The composition, specific surface area, microscopic morphology and particle size of the monodisperse nano calcium carbonate filter cake obtained in this embodiment were tested and analyzed by the same test method as in Example 1. The contents of harmful impurities such as cadmium, lead, barium, mercury and arsenic in the monodisperse nano calcium carbonate were all less than 0.0002%, and the total content of harmful impurities was less than 200 ppm; the specific surface area was about 21.15 m 2 / g; From the SEM photos (see Fig.11 ) It can be clearly seen that the average particle size of the monodisperse nano calcium carbonate particles obtained is about 56nm, the particles are cubic, and the surface is flat and clean. The monodisperse nano calcium carbonate filter cake obtained is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 4 hours. It can still be stably suspended (see Fig. 20 ).

[0095] When used for pear planting: before the pear fruit expansion period, the new foliar calcium fertilizer prepared in this embodiment is diluted 10 times (solid content of calcium carbonate is about 0.5%) and sprayed on the leaves of the pear tree. After spraying, take photos to record the growth status of the whole pear tree, and observe it regularly once a week thereafter. Spraying 1 to 2 times during the pear ripening process is required. If the rainfall reaches 120 mm or more for more than 3 days, it is necessary to spray once after the rain, and ensure that there will be no rainfall for 24 hours before spraying.

[0096] The effect of the new foliar calcium fertilizer prepared in this embodiment on pears is shown in the figure below: Fig.12As shown, the new foliar calcium fertilizer can spread quickly and adhere evenly on the leaves of pear trees.

[0097] The results of the calcium content test on the pear pulp after spraying the new foliar calcium fertilizer prepared in this embodiment (set-4) with water (ck-4) are shown in Table 1. After spraying the new foliar calcium fertilizer in this embodiment, the calcium content in the pear pulp increased by 173.17%.

[0098] Example 5

[0099] The present embodiment provides a novel foliar calcium fertilizer, which is prepared in the following weight ratios: 20 parts of monodisperse nano calcium carbonate filter cake, 0.8 parts of ethoxy-modified polytrisiloxane, 0.8 parts of modified casein, 0.2 parts of enzyme, 0.7 parts of maltitol, and 180 parts of clean water.

[0100] The preparation method of the novel foliar calcium fertilizer described in this embodiment is as follows: according to the above raw materials and mass fractions, 20 parts of monodisperse nano calcium carbonate filter cake are placed in 20 parts of clean water, and stirred for 20 minutes with a high-speed disperser at a stirring line speed of 110m / min, and then 0.8 parts of ethoxy-modified polytrisiloxane, 0.8 parts of modified casein, 0.2 parts of enzyme, 0.7 parts of maltitol and the remaining 160 parts of clean water are added according to the above formula, and stirring is continued at a stirring line speed of 100m / min for 20 minutes to obtain the foliar calcium fertilizer described in this embodiment, and the solid content of calcium carbonate is about 6%. Among them, the preparation steps of the monodisperse nano calcium carbonate filter cake are different from those in Example 1 in that the digestion temperature in step S1 is 80°C, the aging time is 30h, the solid content of the refined raw pulp during the carbonization process is 8%, the carbonization starting temperature is 10°C, the CO2 content is 35%, and the carbonization is terminated when the pH reaches 7.5 to 8.0. After the carbonization is completed, the microscopic morphology of the calcium carbonate particles in the obtained cooked pulp is characterized, and it can be observed that the calcium carbonate particles are chain-shaped with an average width of about 45nm (see Fig.13 ); Step S2: During the grain surface reconstruction process, 1.5% of zinc sulfate and 2% of disodium ethylenediaminetetraacetate by dry weight of calcium carbonate were added and kept warm at 135° C. for 5 hours.

[0101] The same test method as in Example 1 was used to test and analyze the composition, specific surface area, microscopic morphology and particle size of the monodisperse nano calcium carbonate filter cake obtained in this example. The contents of harmful impurities such as cadmium, lead, barium, mercury and arsenic in the monodisperse nano calcium carbonate were all less than 0.0002%, and the total content of harmful impurities was less than 200 ppm; the specific surface area was about 19.31 m 2 / g; From the SEM photos (see Fig.14) It can be clearly seen that the average particle size of the monodisperse nano calcium carbonate particles obtained is about 85nm, the particles are cubic, and the surface is flat and clean. The monodisperse nano calcium carbonate filter cake obtained is dispersed in clean water to obtain a suspension with a solid content of 2%, and then the suspension effect is observed after standing for 4 hours. It can still be stably suspended (see Fig. 20 ).

[0102] When used for apple planting: Before the apple fruit expansion period, the new foliar calcium fertilizer prepared in this embodiment is diluted 6 times (solid content of calcium carbonate is about 1.0%) and sprayed on the leaves of the apple tree. After spraying, take photos to record the growth status of the whole apple tree, and observe it regularly once a week thereafter. Spraying 1 to 2 times during the ripening process of apples is required. If the rainfall reaches 120 mm or more for more than 3 days, it is necessary to spray once after the rain, and ensure that there will be no rainfall for 24 hours before spraying.

[0103] The effect of the new foliar calcium fertilizer prepared in this embodiment on apples is shown in the figure below: Fig.15 As shown in the figure, the new foliar calcium fertilizer can spread quickly and evenly adhere to the leaves of apple trees.

[0104] The calcium content of apple pulp was tested by spraying the novel foliar calcium fertilizer prepared in this embodiment on apples (set-5) and spraying with clean water (ck-5). The results are shown in Table 2. The calcium content of apple pulp increased by 58.80%.

[0105] Comparative Example 1

[0106] Comparative Example 1 has the same formula as Example 1, except that no inorganic grain surface reconstructor is added in the preparation method of calcium carbonate. The microscopic morphology of the obtained product is shown in FIG. Fig.16 .

[0107] In Comparative Example 1, because no inorganic crystal surface reconstructor was added, the surface of the calcium carbonate crystals was rough, the dispersibility between the particles was relatively poor, and the particles were connected to each other, resulting in reduced dispersion stability in water. In addition, due to the hard agglomeration of the particles, the dispersion was uneven when sprayed on the leaves of the baby cabbage (such as Fig.17 As shown in the figure, the local concentration is high, which leads to the blockage of leaf stomata and weakens the calcium absorption ability of baby cabbage.

[0108] Comparative Example 2

[0109] The calcium carbonate preparation method of Comparative Example 2 is the same as that of Example 2. The calcium carbonate filter cake prepared in Example 2 is directly used as foliar calcium fertilizer without adding auxiliary materials such as ethoxy-modified polytrisiloxane, modified casein, enzyme, and mannitol.

[0110] In Comparative Example 2, because no auxiliary materials were added, the foliar calcium fertilizer did not infiltrate the rice leaves during the spraying process, resulting in the failure to spray the foliar calcium fertilizer evenly. Fig.18As shown, and calcium absorption is poor.

[0111] Comparative Example 3

[0112] Comparative Example 3 has the same formula as Example 4, except that no organic crystal surface reconstruction agent is added in the preparation method of calcium carbonate. The microscopic morphology of the obtained product is shown in FIG. Fig.19 .

[0113] In Comparative Example 2, since no organic crystal surface reconstructor was added, the surface of the calcium carbonate crystals was clean, but the dispersion between the particles was still relatively poor, and connections were formed between the particles, resulting in reduced dispersion stability in water. Fig. 20 As shown in the figure, due to the hard agglomeration of particles, it is not possible to achieve uniform adhesion when sprayed on pear trees. Fig.21 As shown, there are more spots on the surface of the pear fruit and the calcium absorption effect is poor.

[0114] Comparative Example 4

[0115] Comparative Example 4 has the same formula as Example 4, except that the preparation method of the foliar calcium fertilizer is not carried out according to the two-step dispersion step, but 5 parts of monodisperse nano calcium carbonate filter cake are directly added to 55 parts of clean water, stirred for 15 minutes at a stirring line speed of 120 m / min using a high-speed disperser, and after stirring evenly, ethoxy-modified polytrisiloxane, modified casein, enzyme and lactitol are added according to the ingredient relationship, and stirring is continued at a stirring line speed of 100 m / min for 15 minutes.

[0116] Comparative Example 5 has no high-concentration stirring step, resulting in poor dispersion of calcium carbonate. When used for calcium supplementation of pears, it cannot be evenly attached and there are local differences in density, such as Fig. 22 As shown, most of them are accumulated in the fruit pedicle, resulting in more spots on the surface of the mature fruit and a higher fruit drop rate of the pear.

[0117] Comparative Example 5

[0118] The formula of Comparative Example 5 is the same as that of Example 5, except that in the preparation method of calcium carbonate, filter pressing is not performed to obtain a monodisperse calcium carbonate filter cake of a special form, but the slurry obtained after the surface of the grains is directly formulated according to the proportions described in Example 1.

[0119] In Comparative Example 5, because no filtration was performed to remove the soluble ions in the slurry, the slurry could not be evenly attached when used for apple planting, resulting in more spots and cracks on the surface of the apples after they matured. Fig.23 shown.

[0120] The calcium content in the edible part of the fruits and vegetables in the above embodiments and comparative examples was determined in accordance with GB 5009.268-2016.

[0121] Table 1

[0122]

[0123]

[0124] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and changes without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A monodisperse nano calcium carbonate-based foliar calcium fertilizer, characterized in that: The raw material composition includes, by weight: 1 to 20 parts of monodisperse nano calcium carbonate filter cake, 0.05 to 0.9 parts of ethoxy-modified polytrisiloxane, 0.01 to 0.8 parts of modified casein, 0.01 to 0.8 parts of enzyme, 0.05 to 0.9 parts of sugar alcohol, and 10 to 180 parts of water; The water content of the monodisperse nano calcium carbonate filter cake is 35% to 40%, the average particle size of the calcium carbonate particles is between 20 and 100 nm, the particles with a particle size greater than 100 nm are less than 5%, and the specific surface area is less than 25 m 2 / g; and the monodisperse nano calcium carbonate filter cake is stirred and dispersed in the aqueous solution without adding any chemical dispersant, and remains stably suspended.

2. A monodisperse nano calcium carbonate-based foliar calcium fertilizer according to claim 1, characterized in that: The method for preparing the monodisperse nano calcium carbonate filter cake comprises the following steps: S1. Prepare calcium carbonate pulp by processes including calcination, digestion and carbonization; S2. Adding an inorganic salt crystal surface reconstructor and an organic crystal surface reconstructor to the calcium carbonate slurry obtained in S1, and then keeping the mixture at 120 to 140° C. for 1.0 to 4.0 h to obtain a calcium carbonate suspension; S3. The calcium carbonate suspension obtained in S2 is dehydrated by hydraulic filtration to obtain a calcium carbonate filter cake, wherein the water content of the filter cake is controlled between 35% and 40%, i.e., a monodisperse nano calcium carbonate filter cake.

3. A monodisperse nano calcium carbonate-based foliar calcium fertilizer according to claim 2, characterized in that: The calcination process is as follows: limestone with uniform grain size and harmful heavy metal content less than 400ppm is selected as raw material, and calcined to obtain quicklime, the activity of which is in the range of 250 to 300mL; The digestion process is as follows: the quicklime obtained by the calcination is digested in hot water at 50-90°C to obtain lime milk, which is then aged for 24-48 hours and filtered to remove impurities to obtain refined raw pulp; The carbonization process is as follows: add water to the refined raw pulp to adjust the solid content to 5% to 8%, and then carbonize it. The starting temperature of carbonization is 10 to 20°C, the CO2 content is 20% to 40%, and the pulp is carbonized until the pH value reaches 7.5 to 9.

0. Then the carbonization is terminated to obtain calcium carbonate cooked pulp.

4. A monodisperse nano calcium carbonate-based foliar calcium fertilizer according to claim 1, characterized in that: The inorganic grain surface reconstruction agent is one or more of the inorganic salt sodium silicate, sodium chloride, aluminum chloride, and zinc sulfate, and the dosage is 0.5% to 3% of the dry basis mass of calcium carbonate; the organic grain surface reconstruction agent is one or more of ethanol, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl alcohol, sodium dodecylbenzene sulfonate, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, and disodium ethylenediaminetetraacetate, and the dosage is 1% to 5% of the dry basis mass of calcium carbonate.

5. A monodisperse nano calcium carbonate-based foliar calcium fertilizer according to claim 1, characterized in that: The monodisperse nano calcium carbonate filter cake is stirred and dispersed in an aqueous solution without adding any chemical dispersant to obtain a suspension. When the solid content of the suspension is 5% to 30%, the suspension can be stably suspended for more than 14 hours.

6. A monodisperse nano calcium carbonate-based foliar calcium fertilizer according to claim 1, characterized in that: The sugar alcohol includes one or more of xylitol, ribitol, mannitol, sorbitol, maltitol, erythritol and lactitol; and the enzyme is a commercially available agricultural enzyme.

7. The method for preparing the monodisperse nano-calcium carbonate-based foliar calcium fertilizer according to any one of claims 1 to 6, characterized in that: The steps include: (1) According to the raw materials and their weight parts, prepare 1 to 20 parts of monodisperse nano calcium carbonate filter cake, 0.05 to 0.9 parts of ethoxy-modified polytrisiloxane, 0.01 to 0.8 parts of modified casein, 0.01 to 0.8 parts of enzyme, 0.05 to 0.9 parts of sugar alcohol, and 10 to 180 parts of water; (2) placing the monodisperse nano calcium carbonate filter cake in a portion of water at a temperature of 5 to 30° C. and dispersing it in a high-speed disperser at a linear speed of 80 to 120 m / min for 15 to 40 min; (3) After the stirring in step (2) is completed, other raw materials and the remaining water are added, and the mixture is dispersed in a high-speed disperser at a linear speed of 80 to 120 m / min for 15 to 30 min to obtain the monodisperse nano-calcium carbonate-based foliar calcium fertilizer.

8. The method for preparing the monodisperse nano-calcium carbonate-based foliar calcium fertilizer according to claim 7, characterized in that: In step (2), the amount of water used to disperse the monodisperse nano-calcium carbonate filter cake is 1 to 2 times the weight of the monodisperse nano-calcium carbonate filter cake.

9. The method for applying the monodisperse nano-calcium carbonate-based foliar calcium fertilizer according to any one of claims 1 to 6, characterized in that: Dilute with water to a solid content of calcium carbonate of 0.5% to 2% and then spray directly.

10. The method for applying the monodisperse nano-calcium carbonate-based foliar calcium fertilizer according to claim 9, characterized in that: In rainless and dry weather, the foliar calcium fertilizer is diluted and sprayed on the leaves of grain crops or vegetable and fruit crops without avoiding the fruits. It needs to be sprayed 2 to 4 times during the growth of the crops.

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