Compound fertilizer for improving acidified soil of sloping cultivated land by using biological soil crust and preparation method thereof

Abstract

The invention discloses a compound fertilizer for improving acidified soil in sloping farmland by using biological soil crusts and a preparation method thereof. Straw debris, crushed citrus waste fruits, cow dung, rapeseed cake and yeast powder are stirred and mixed and then fermented and composted to obtain organic fertilizer A. Then, plant ash and a mixed bacterial solution are incorporated to obtain alkaline organic fertilizer. After the alkaline organic fertilizer is crushed, it is fully mixed and granulated with urea, phosphogypsum, potassium sulfate and superphosphate. The surface of the obtained organic-inorganic compound fertilizer is sprayed with green algae suspension and sodium alginate in sequence and dried at low temperature to obtain the compound fertilizer. The compound fertilizer of the invention can quickly form biological soil crusts when applied to the soil, reduce soil leaching, and at the same time organically combine organic fertilizer, inorganic fertilizer and microbial inoculant, and is made into spherical fertilizer for convenient mechanized fertilization, meeting the nutrient requirements of crops during the whole growth period while improving acidified soil, not only improving the availability of acidified soil, but also promoting the sustainable development of farmland.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizer production, and particularly to a compound fertilizer for improving acidified soil on sloping farmland by using biological soil crust and a preparation method thereof. Background Art

[0002] Soil acidification belongs to the deterioration of soil properties in the classification of soil degradation and is a global soil degradation problem. One of the main causes of soil acidification in humid regions is the severe leaching of soil caused by high rainfall, which leads to a large loss of base cations such as Ca 2+ , Mg 2+ etc. Especially in sloping farmland, the soil and water loss is relatively serious, which is easy to carry away a large amount of cations in the soil, reduce the buffering capacity of soil acidification, and finally form a stable acidified soil dominated by Al. Soil acidification causes an increase in the concentration and activity of toxic elements such as H + , Al 3+ and Mn 2+ etc., resulting in poor root development of crops and seriously affecting the growth and development of crops.

[0003] The existing methods for improving acidified soil mainly include chemical improvement, organic fertilizer improvement and microbial improvement, etc. The corresponding modifiers are mineral-based, organic fertilizers, acid-suppressing microbial inoculants, etc. However, mineral-based modifiers such as quicklime are strong alkaline substances, and directly applying them to the soil may cause a large increase in local pH and damage the soil ecological environment; organic fertilizer modifiers improve soil quality by inputting organic matter. Among them, alkaline organic fertilizers can increase soil pH, but the dosage is large, the short-term effect is not obvious, and the cost is high; acid-suppressing microbial inoculants have an inhibitory effect on soil acidification, but the effect is unstable and cannot be applied to various types of soil.

[0004] CN111943750 A discloses a biological organic fertilizer for preventing soil acidification and hardening, which uses organic materials such as crop residues, mountain soil, poultry manure, livestock manure, etc. as raw material components of the organic fertilizer, but no inorganic materials are incorporated. Although it can improve the soil, it cannot increase the soil pH in the short term to achieve the effect of improving acidified soil.

[0005] CN108863636 A discloses an alkaline compound fertilizer for preventing and improving soil acidification and a preparation method thereof, which is prepared from urea, diammonium phosphate, potassium sulfate, calcium oxide and calcium carbonate, but it can only increase the soil pH and cannot improve the soil quality, and cannot meet the needs of improving the quality of acidified soil.

[0006] CN115536476 A discloses a soil conditioner composition capable of rapidly and long-term improving soil acidification and its preparation method. It combines humic acid substances, calcium-silicate minerals, matured organic substances and biochemical fulvic acid to increase soil pH, improve soil pH buffering capacity and soil quality in a short time. However, its nutrient content is low and cannot meet the nutritional requirements of crop growth.

[0007] Biological soil crust is a complex structure formed by the cementation of organisms and soil surface particles (for example, blue / green algae can form symbiotic relationships with other microorganisms in the soil and then form biological soil crust on the soil surface). It has multiple ecological functions. It can reduce rainfall infiltration and thus reduce soil erosion, retain soil cations, provide and improve the acid buffering capacity of the soil, and can also fix the surface soil, reduce soil and water loss, and contribute to the formation of a good soil structure. In addition, symbiosis with other microorganisms can increase the abundance of soil microorganisms and the stability of community structure, improve the soil habitat, and is expected to further alleviate the problem of soil acidification. At present, most biological soil crusts in the soil rely on natural formation, and there is no research on introducing biological soil crusts using fertilizers. The application of blue / green algae as the precursor organisms of biological soil crusts has rarely been reported. Usually, inactivated blue / green algae are used as raw materials or nutrients in organic fertilizers to increase their fertility. However, inactivated blue / green algae cannot form biological soil crusts in the soil and the dosage is large, and the problem of algal toxins needs to be considered. In addition, compound fertilizers themselves, as fertilizers with nutrient components, will also affect the growth of microbial communities and thus affect the formation of biological soil crusts. Therefore, developing new fertilizers and using fertilizers as a medium to accelerate the formation of biological soil crusts on the soil surface, while taking into account the nutrient status of fertilizers and improving soil acidification, is a problem that needs to be overcome.

[0008] In summary, all existing products for improving acidified soil cannot fundamentally solve the problem of soil acidification, and cannot meet the comprehensive requirements of increasing soil pH, improving soil quality and providing nutrients required by crops. It is even more difficult to solve the problems of cation loss and low soil acid buffering capacity caused by soil and water loss on sloping farmland. Summary of the Invention

[0009] The first object of the present invention is to provide a preparation method of a compound fertilizer for improving acidified soil on sloping farmland using biological soil crusts. It combines organic materials, inorganic modifiers, inorganic fertilizers, acid-suppressing microbial agents and algae. While ensuring the increase of soil pH, it improves the soil quality, supplements the missing base ions in the soil, and at the same time rapidly forms a biological soil crust on the soil surface with green algae as the base as a "protective film" to reduce the scouring and leaching of rainwater on the soil, improve the functional effectiveness and long-term nature of the organic-inorganic compound fertilizer, and fundamentally improve acidified soil.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] Preparation method of compound fertilizer for improving acidified soil of sloping cultivated land by using biological soil crust, comprising:

[0012] After stirring and mixing straw debris, crushed citrus waste fruits, cow dung, rapeseed cake and yeast powder, stack them into long strips for fermenting compost to obtain organic fertilizer A;

[0013] Mix wood ash into organic fertilizer A to adjust the pH to above 8.0 to obtain organic fertilizer B, and mix the mixed bacterial solution into organic fertilizer B to obtain alkaline organic fertilizer;

[0014] After crushing the alkaline organic fertilizer, fully mix it with urea, phosphogypsum, potassium sulfate and superphosphate, and add the mixed materials into a granulator for granulation to obtain organic-inorganic compound fertilizer A;

[0015] Place the organic-inorganic compound fertilizer A in a rotary drum, evenly spray the green algae suspension with a spray gun, spray sodium alginate again after spraying, and dry it at low temperature to obtain the compound fertilizer for improving acidified soil by using biological soil crust.

[0016] As a preferred embodiment, the mass ratio of crop straw, cow dung, citrus waste fruits and rapeseed cake is 2-9:1-5:1:3:1-5; the addition amount of yeast powder is 1‰-2‰ of the total mass of crop straw, cow dung, citrus waste fruits and rapeseed cake.

[0017] As a preferred embodiment, the temperature during composting is controlled at 40-55°C, and the humidity is controlled at 45-60%.

[0018] As a preferred embodiment, adjust the composting process according to the proportion of different organic materials; specifically, determine the compost turning time according to the carbon-nitrogen ratio (C / N ratio) of each material, the difficulty of decomposition of raw materials (such as cellulose and lignin with high content in crop straw), the initial active organic carbon content (high content of active organic carbon has high compost fermentation efficiency), and the turning frequency (improving compost air permeability and uniformity).

[0019] For example: the ratio of crop straw, cow dung, citrus waste fruits and rapeseed cake is 2:1:1:1, and the total composting time is 3-5 months. In the initial stage (the first 1-2 months), turn the compost once a week, and in the later stage (3-5 months), turn the compost once every 2-3 weeks;

[0020] The ratio of crop straw, cow dung, citrus waste fruits and rapeseed cake is 3:3:2:2, and the total composting time is 2-4 months. In the initial stage (the first month), turn the compost once a week, and in the later stage (2-4 months), turn the compost once every 2-4 weeks.

[0021] The ratio of crop straw, cow dung, citrus waste fruits and rapeseed cakes is 7:5:3:5, and composting is carried out for 4 - 6 months. In the initial stage (the 1st - 2nd month), it is turned and raked once a week, and in the later stage (the 3rd - 6th month), it is turned and raked once every 3 - 4 weeks;

[0022] The ratio of crop straw, cow dung, citrus waste fruits and rapeseed cakes is 9:3:3:5, and composting is carried out for 3 - 6 months. In the initial stage (the 1st - 2nd month), it is turned and raked once a week, and in the later stage (the 3rd - 6th month), it is turned and raked once every 2 - 3 weeks.

[0023] As a preferred embodiment, the mixed bacterial liquid is obtained by diluting the bacterial powders of Bacillus subtilis, Bacillus megaterium, Pseudomonas and Saccharomyces cerevisiae after mixing them according to the mass ratio of 3 - 7: 3 - 7: 2 - 6: 2 - 7.

[0024] As a preferred embodiment, the dosage of the mixed bacterial liquid is such that the amount of mixed bacterial powder added to each ton of organic fertilizer B reaches 5 - 7.5 kg.

[0025] As a preferred embodiment, 15 - 25 kg of urea, 20 - 40 kg of phosphogypsum, 15 - 35 kg of potassium sulfate and 10 - 30 kg of superphosphate are added to each ton of alkaline organic fertilizer.

[0026] As a preferred embodiment, the green algae suspension is obtained by diluting the green algae concentrated solution with water, and the dosage of the green algae concentrated solution is 30 - 100 g / t of organic - inorganic compound fertilizer A;

[0027] The biomass dry weight in the green algae suspension is 700 - 800 g / L. Diluting the green algae concentrated solution facilitates uniform spraying.

[0028] As a preferred embodiment, the concentration of the sodium alginate solution is 1 - 3%, and the dosage is 20 - 50 L / t of organic - inorganic compound fertilizer A.

[0029] As a preferred embodiment, after spraying sodium alginate, it is dried at 30 - 40 °C.

[0030] Another object of the present invention is to provide a compound fertilizer prepared by the above - mentioned method.

[0031] The organic-inorganic compound fertilizer provided by the present invention can quickly form a biological crust in the soil while ensuring soil fertility, effectively improve soil acidity, enhance soil quality, and reduce nutrient and soil erosion. The biological crust can effectively prevent rainfall infiltration, reduce soil nutrient leaching, and prevent or delay the process of soil acidification; the organic substances in the fertilizer, including humic acid, can not only improve soil air permeability and water retention capacity, but also promote the formation and maintenance of soil aggregate structures, thus creating a more suitable crop growth environment; Bacillus subtilis and Bacillus megaterium can produce a large amount of extracellular enzymes, which can effectively decompose organic matter in the soil, release amino acids and alkaline substances to neutralize soil acidity, promote the release of soil nutrients, and at the same time can produce substances similar to cytokinins and auxins that can improve plant immune functions; Pseudomonas can produce alkaline substances such as ammonia, which is beneficial to loosening soil structure, especially in soils with low nitrogen and phosphorus contents, it can increase the availability of nutrients; yeast mainly participates in the fermentation process of organic matter in the soil, which helps to increase the diversity and biological activity of soil microorganisms. The inorganic materials in the organic-inorganic compound fertilizer also play an active role in improving the fertilizer nutrient supply capacity and amending soil acidification. The main component of gypsum is CaSO4. When added to variable charge soils, SO4 2- ions are specifically adsorbed, releasing OH - to neutralize H + in the soil, and at the same time, the released Ca 2+ can replace Al 3+ and H + in soil colloids, supplement soil base cations, increase soil cation exchange capacity (CEC), and more stably and continuously amend soil acidity; potassium sulfate can supplement K + leached in large amounts in the soil under high temperature and rainy environments, and can also increase soil CEC, improve soil physical structure, promote the formation of soil aggregate structures, and increase soil air permeability and water retention capacity; superphosphate can not only provide P required for plant growth, but also bring a large amount of Ca 2+ into the soil, improving the degree of soil acidification.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) Aiming at the main causes of soil acidification in sloping farmland soils, the present invention introduces green algae into the fertilizer, so that when the fertilizer is spread, the green algae are used as a pre-biological agent to quickly form a biological crust on the soil surface, effectively reducing the large infiltration of rainwater and other substances, reducing the leaching of soil base particles, and fundamentally preventing or delaying the process of soil acidification.

[0034] (2) By strictly controlling the proportion of inorganic substances in compound fertilizer granulation and spraying sodium alginate on the surface for the preservation of green algae, the present invention realizes the application of green algae as a pre - biological crust into the soil through fertilizers, while improving the soil habitat and accelerating the formation of biological crust on the soil surface, which is more conducive to controlling soil acidification.

[0035] (3) The present invention is designed for acidified soil on sloping farmland. It uses gypsum, plant ash, etc. to neutralize soil acidity and increase soil pH value. At the same time, potassium sulfate and superphosphate are used as the supply of soil potassium and phosphorus, while bringing in calcium, potassium, etc. to supplement the missing base cations in acidified soil, and exchanging Al 3+ and H + on the surface of soil colloids, so that they can flow away with water, which can not only reduce soil acidity but also improve soil CEC and nutrient supply capacity.

[0036] (4) The present invention combines a variety of organic and inorganic materials and microbial inoculants, providing a more comprehensive nutrient supply capacity for crop growth, better meeting the diverse nutritional needs of plants. The materials used are all relatively mild components, continuously improving the physical and chemical properties of the soil, and can improve the stability and abundance of the soil microbial community, avoiding strong stimulation to soil organisms in the original soil environment.

[0037] (5) The present invention combines organic materials and inorganic materials to increase the nutrient content in fertilizers. Through disk granulation, it can achieve one - time mechanized fertilization, avoiding secondary fertilization after the application of traditional organic fertilizers. The inorganic substances in the fertilizer provide a large amount of quick - acting nutrients, and the nutrients in the organic fertilizer are released through slow decomposition, which can meet the nutrient requirements of crops throughout the growth period. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 shows the biological crust situation on the soil surface of each treatment in the corn pot experiment. DETAILED DESCRIPTION OF THE INVENTION

[0039] It should be noted that the following detailed description is illustrative and aims to provide further explanation for the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0040] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in combination with specific embodiments.

[0041] The test materials used in the embodiments of the present invention are all conventional test materials in the art and can be obtained through commercial channels.

[0042] Bacillus subtilis, Bacillus megaterium, Pseudomonas and yeast (all in powder form) used in the examples were purchased from Hubei Xingdongcheng Chemical Co., Ltd.

[0043] The green algae concentrate used in the examples was purchased from Foster Biotechnology (Taizhou) Co., Ltd. Among them, 60 - 70% was Chlorella vulgaris, and the dry weight of the green algae concentrate was 700 - 800 g / L. The dry weight refers to the biomass weight obtained after drying the concentrate per unit volume to a constant weight.

[0044] Example 1

[0045] The compound fertilizer was prepared by the following steps:

[0046] (1) The crop straw was dried at 50 - 55 °C until the water content was about 4%, and then cut into 1 - 3 cm debris using a straw chopper. At the same time, the defective citrus fruits were pulverized in a special pulverizing device. Subsequently, the treated crop straw, cow dung, defective citrus fruits and rapeseed cake were mixed in a weight ratio of 3:3:2:2, and yeast powder was added in a ratio of 1‰ (mass ratio), diluted with water to ensure uniform mixing, and fully stirred in a stirring container to ensure uniform distribution of the components.

[0047] The mixed materials were stacked into long strips and subjected to a 3 - month fermentation composting process. During the fermentation, a temperature and humidity monitor was used to regularly detect the temperature and humidity of the compost, ensuring a test depth of 20 cm. During the fermentation process, the compost temperature was controlled at 40 - 55 °C and the humidity at 45% - 60%. In the initial stage of composting (the first month), turning and raking were carried out once a week; in the later stage (the second and third months), it was adjusted to turning and raking once every three weeks to promote full fermentation and decomposition of the materials. After fermentation was completed, the compost was sun - dried to control the final water content between 30% - 40% to obtain organic fertilizer A.

[0048] (2) Wood ash was added to organic fertilizer A to adjust the pH value of organic fertilizer A to 8.0 to obtain organic fertilizer B. Then, the powder of Bacillus subtilis, Bacillus megaterium, Pseudomonas and yeast was mixed in a ratio of 5:5:6:4, and according to the ratio of adding 5 kg of the mixed bacterial powder per ton of organic fertilizer B, the mixed bacterial powder was diluted and evenly added to organic fertilizer B and fully stirred to ensure that the microorganisms were evenly distributed throughout the compost, thus obtaining an alkaline organic fertilizer.

[0049] (3) Dry the alkaline organic fertilizer to a moisture content of about 30% and then pulverize it. Add 15 kg, 30 kg, 25 kg, and 30 kg of urea, potassium sulfate, superphosphate, and phosphogypsum (all in powder form) per ton respectively. Mix them thoroughly in a mixer, add the mixture to a disk granulator, adopt the conventional granulation method, adjust the inclination angle of the disk granulator to 45°, adjust the rotation speed to 21 r / min, and spray the binder into the disk granulator during the granulation process. The granulation time is 20 min, and at the same time, ensure that the thickness of the material layer in the disk is 20 cm. After completion, screen it through a 2 - 7 mm steel sieve, and obtain spherical organic-inorganic compound fertilizer A after drying.

[0050] (4) Place the spherical organic-inorganic compound fertilizer A in a rotating drum and evenly spray the green algae suspension using a spray gun. The green algae suspension is prepared by diluting the purchased green algae concentrate 100 times with water according to the dosage of 50 g / t of organic-inorganic compound fertilizer A (the dry weight of the green algae concentrate is 730 g / L). After spraying, to ensure the stability and activity of the green algae on the surface of the fertilizer, spray sodium alginate again using a spray gun. The concentration of the sodium alginate solution is set at 2% (mass ratio), and the spraying amount per ton of organic-inorganic compound fertilizer A is 35 L. After spraying, dry it at 30 - 40 °C to obtain the special organic-inorganic compound fertilizer for acidified soil improvement.

[0051] Example 2

[0052] Prepare the compound fertilizer by the following steps:

[0053] (1) Dry the crop straw at 50 - 55 °C until the water content is about 3%, and then use a straw cutter to cut it into 1 - 3 cm debris. At the same time, pulverize the citrus defective fruits in a special pulverizing device. Subsequently, mix the treated crop straw, cow dung, citrus defective fruits, and rapeseed cake according to the weight ratio of 7:5:3:5, and add yeast powder at a ratio of 1.5‰ (mass ratio, dilute it with water to ensure uniform mixing), and stir thoroughly in a stirring container to ensure uniform distribution of the components.

[0054] Stack the mixed materials into long strips and carry out a 4-month fermentation composting process. During the fermentation period, use a temperature and humidity monitor to regularly detect the temperature and humidity of the compost, ensuring that the test depth is 20 cm. Control the compost temperature at 40 - 55 °C and the humidity at 45% - 60% during the fermentation process. In the initial stage of composting (the first 1.5 months), turn the compost once a week; in the later stage (2.5 - 4 months), adjust it to turn the compost once every three weeks to promote the full fermentation and decomposition of the materials. After the fermentation is completed, sun-dry the compost and control the final water content between 30% - 40% to obtain organic fertilizer A.

[0055] (2) Add plant ash to organic fertilizer A to adjust the pH value of organic fertilizer A to 8.0, obtaining organic fertilizer B. Then, mix Bacillus subtilis, Bacillus megaterium, Pseudomonas, and Saccharomyces cerevisiae in a ratio of 3:7:2:2. According to the ratio of adding 7.5 kg of the mixed bacterial powder per ton of organic fertilizer B, dilute the mixed bacterial powder and evenly add it to organic fertilizer B, and stir well to ensure that the microorganisms are evenly distributed throughout the compost, thereby obtaining alkaline organic fertilizer.

[0056] (3) Dry the alkaline organic fertilizer to a moisture content of about 35% and then pulverize it. The amounts of urea, potassium sulfate, superphosphate, and phosphogypsum (all in powder form) added per ton are 25, 15, 30, and 40 kg respectively. Mix them thoroughly in a mixer, add them to a disc granulator, and use the conventional granulation method. Adjust the tilt angle of the disc granulator to 45°, adjust the rotation speed to 18 r / min, and spray the binder into the disc granulator during the granulation process. The granulation time is 25 min, and at the same time, ensure that the thickness of the material layer in the disc is 20 cm. After completion, screen it through a 2 - 7 mm steel sieve, and dry it to obtain spherical organic-inorganic compound fertilizer A.

[0057] (4) Place spherical organic-inorganic compound fertilizer A in a rotary drum and evenly spray the green algae suspension using a spray gun. The green algae suspension is prepared by diluting the purchased green algae concentrate 100 times with water according to the dosage of 100 g / t of organic-inorganic compound fertilizer A (the dry weight of the green algae concentrate is 730 g / L). After spraying, to ensure the stability and activity of the green algae on the fertilizer surface, spray sodium alginate again using a spray gun. The concentration of the sodium alginate solution is set at 1%, and the spraying amount per ton of organic-inorganic compound fertilizer A is 50 L. After spraying, dry it at 30 - 40 °C to obtain the special organic-inorganic compound fertilizer for acidified soil improvement.

[0058] Example 3

[0059] Prepare the compound fertilizer by the following steps:

[0060] (1) Dry the crop straw at 50 - 55 °C until the water content is about 3%, and then use a straw chopper to cut it into 1 - 3 cm debris. At the same time, crush the citrus defective fruits in a special crushing device. Subsequently, mix the processed crop straw, citrus defective fruits with cow dung and rapeseed cake in a weight ratio of 2:1:1:1, and add yeast powder at a ratio of 2‰ (mass ratio, dilute it with water to ensure uniform mixing), and stir well in a stirring container to ensure uniform distribution of the components.

[0061] Stack the mixed materials into long strips and carry out a 4-month fermentation composting process. During the fermentation period, use a temperature and humidity monitor to regularly detect the temperature and humidity of the compost, ensuring a test depth of 20 cm. Control the compost temperature at 40 - 55 °C and the humidity at 45% - 60% during the fermentation process. In the initial stage of composting (the first 1.5 months), turn the rake once a week; in the later stage (2.5 - 4 months), adjust to turning the rake once every three weeks to promote the full fermentation and decomposition of the materials. After fermentation is completed, dry the compost and control the final water content between 30% - 40% to obtain organic fertilizer A.

[0062] (2)Adjust the pH value of organic fertilizer A to 8.0 with plant ash to obtain organic fertilizer B. Then mix Bacillus subtilis, Bacillus megaterium, Pseudomonas, and Saccharomyces cerevisiae in a ratio of 7:3:3:7. According to the ratio of adding 7.5 kg of the mixed bacterial powder per ton of composted organic fertilizer B, dilute the mixed bacterial powder and evenly add it to organic fertilizer B and stir well to ensure that the microorganisms are evenly distributed throughout the compost, thus obtaining alkaline organic fertilizer.

[0063] (3)Dry the alkaline organic fertilizer to a water content of about 35% and crush it. The amounts of urea, potassium sulfate, superphosphate, and phosphogypsum (all in powder form) added per ton are 20, 35, 10, and 20 kg respectively. Mix well in a mixer and add it to a disk granulator. Use the conventional granulation method, adjust the inclination angle of the disk granulator to 45°, adjust the rotation speed to 18 r / min, and spray the binder into the disk granulator during the granulation process. The granulation time is 25 min, and at the same time, ensure that the thickness of the material layer in the disk is 20 cm. After completion, pass through a 2 - 7 mm steel sieve and dry it to obtain spherical organic-inorganic compound fertilizer A.

[0064] (4)Place the spherical organic-inorganic compound fertilizer A in a rotating drum and evenly spray the green algae suspension with a spray gun. The green algae suspension is prepared by diluting the purchased green algae concentrate 100 times with water according to the dosage of 30 g / t of organic-inorganic compound fertilizer A (the dry weight of the green algae concentrate is 730 g / L). After spraying, to ensure the stability and activity of the green algae on the fertilizer surface, spray sodium alginate again with a spray gun. The concentration of the sodium alginate solution is set at 3%, and the spraying amount per ton of organic-inorganic compound fertilizer A is 20 L. After spraying, dry it at 30 - 40 °C to obtain the special organic-inorganic compound fertilizer for acidified soil improvement.

[0065] Example 4 Maize Field Plot Experiment

[0066] To verify the effect of the advantageous compatibility of microorganisms - inorganic materials - organic materials of the present invention in improving soil acidification of sloping cultivated land, maize pot and field plot experiments were carried out as follows:

[0067] 1. Test method:

[0068] Pot experiment: A total of five treatments were set up in the experiment, namely CKC (conventional chemical fertilizer combined with green algae), MC (self-made organic fertilizer combined with green algae); GBC (conventional chemical fertilizer combined with gypsum, acid-suppressing microorganisms and green algae); MBC (self-made organic compost combined with acid-suppressing organisms and green algae) and MGBC (special organic-inorganic compound fertilizer for acidified soil prepared according to Example 1) (Note: Except for the MGBC treatment, in all other treatments, green algae were sprayed on the surface of the fertilizer and immediately applied to the soil). Each treatment was set with 3 replicates. The pots used for potting were 40 cm in height and 48 cm in diameter. One corn plant was planted in each pot. A randomized block design was used, and each group was managed under the same conditions. During the planting process, the growth status of biological soil crust on the soil surface was observed.

[0069] Field experiment: A total of six treatments were set up in the experiment, namely CK (conventional chemical fertilizer treatment); CKC (conventional chemical fertilizer combined with green algae), MC (alkaline organic fertilizer in Example 1 combined with green algae); GBC (conventional chemical fertilizer combined with gypsum, acid-suppressing microorganisms and green algae); MBC (self-made organic compost combined with acid-suppressing organisms and green algae) and MGBC (special organic-inorganic compound fertilizer for acidified soil prepared according to Example 1) (Note: Except for the MGBC treatment, in all other treatments with green algae application, green algae were sprayed on the surface of the fertilizer and immediately applied to the soil). Each treatment had 3 replicates, and the area of each plot was set to 50 m 2 , with a randomized block design. The planting density of corn was 4,000 plants per mu. Each group was managed under the same conditions. During the planting process, the pH of the soil was measured, and the yields of each group were statistically analyzed after the corn was harvested.

[0070] In this experiment, the organic fertilizer in the MBC treatment was the alkaline organic fertilizer (not granulated) prepared according to steps (1) and (2) in Example 1, and the organic fertilizer in the MC treatment was the alkaline organic fertilizer (not granulated and without adding mixed bacterial solution) prepared according to steps (1) and (2) in Example 1.

[0071] 2. Test results:

[0072] The biological soil crust conditions on the soil surface of each treatment in the pot experiment are as Figure 1 shown. The application of organic fertilizer significantly increased the coverage of biological soil crust on the soil surface. The MGBC treated with preservation was more beneficial to the growth of biological soil crust, and could form a "protective film" on the soil surface layer, reducing soil leaching caused by rainfall and other factors, thereby fundamentally delaying or solving soil acidification.

[0073] The pH and yield results of each treatment during the corn growth period in the field are shown in Table 1. It can be seen that after applying the special organic-inorganic compound fertilizer for acidified soil improvement of the present invention, the soil pH at each corn stage can be significantly increased, and the corn yield is increased by 35.48% compared with that of applying only chemical fertilizer.

[0074] Table 1 Soil pH and maize yield at the seedling stage and filling stage in maize field plots

[0075] Treatment Soil pH at seedling stage Soil pH at filling stage Yield (kg / mu) CK 4.28 3.94 476.83 CKC 4.28 3.96 473.55 MC 4.43 4.39 448.16 GBC 4.41 4.62 465.82 MBC 4.38 4.36 479.92 MGBC 4.63 5.01 646.01

[0076] The above are all preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. Preparation method of compound fertilizer for improving acidified soil of sloping cultivated land by using biological soil crust, characterized in that, Including: Mix straw debris, crushed citrus waste fruits, cow dung, rapeseed cake and yeast powder, stack them into long strips for fermentation composting to obtain organic fertilizer A; Adjust the pH of organic fertilizer A above 8.0 by adding plant ash to obtain organic fertilizer B, and add a mixed bacterial solution to organic fertilizer B to obtain alkaline organic fertilizer; Crush the alkaline organic fertilizer, mix it thoroughly with urea, phosphogypsum, potassium sulfate and superphosphate, and add the mixed materials to a granulator for granulation to obtain organic-inorganic compound fertilizer A; Place organic-inorganic compound fertilizer A in a rotary drum, evenly spray a chlorella suspension using a spray gun, spray sodium alginate again after spraying, and dry it at low temperature to obtain the compound fertilizer for improving acidified soil on sloping cultivated land using biological crusts; the chlorella is Chlorella vulgaris.

2. The method according to claim 1, wherein The mass ratio of crop straw, cow dung, citrus waste fruits and rapeseed cake is 2-9:1-5:1:3:1-5; the addition amount of yeast powder is 1‰-2‰ of the total mass of straw, cow dung, citrus waste fruits and rapeseed cake.

3. The method according to claim 1, wherein During composting, the temperature is controlled at 40-55°C and the humidity is controlled at 45-60%.

4. The method according to claim 1, wherein The mixed bacterial solution is obtained by mixing the bacterial powders of Bacillus subtilis, Bacillus megaterium, Pseudomonas and yeast according to the mass ratio of 3-7: 3-7: 2-6: 2-7 and diluting.

5. The method according to claim 4, wherein The dosage of the mixed bacterial solution is such that the amount of mixed bacterial powder added per ton of organic fertilizer B reaches 5-7.5 kg.

6. The method according to claim 1, wherein Add 15-25 kg of urea, 20-40 kg of phosphogypsum, 15-35 kg of potassium sulfate and 10-30 kg of superphosphate to each ton of alkaline organic fertilizer.

7. The method according to claim 1, characterized in that, The chlorella suspension is obtained by diluting the chlorella concentrate with water, and the dosage of the chlorella concentrate is 30-100 g / t of organic-inorganic compound fertilizer A; The biomass dry weight in the chlorella concentrate is 700-800 g / L.

8. The method according to claim 1, wherein The concentration of the sodium alginate solution is 1-3%, and the dosage is 20-50 L / t of organic-inorganic compound fertilizer A.

9. The method according to claim 1, wherein After spraying sodium alginate, dry it at 30-40°C.

10. The compound fertilizer prepared by the method according to any one of claims 1 to 9.

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