Preparation method and application of a biochar-based zinc sulfate fertilizer for relieving zinc deficiency stress of calcareous soil

Abstract

The present application belongs to the technical field of biochar-based fertilizer, and particularly relates to a preparation method and application of a biochar-based zinc sulfate fertilizer for relieving zinc deficiency stress of calcareous soil. The biochar-based zinc sulfate fertilizer comprises a mother granule and a first coating, a second coating and a third coating successively coated on the surface of the mother granule; the mother granule is prepared by mixing and granulating urea, diammonium phosphate and potassium sulfate; the first coating comprises sulfur and bentonite; the second coating comprises zinc oxide powder, ammonium bicarbonate and ammonia water; and the third coating comprises biochar. The biochar-based zinc sulfate fertilizer can quickly and efficiently increase the effective zinc content of calcareous soil in the Loess Plateau, so as to cope with the zinc deficiency stress of the soil and promote crop growth.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of biochar-based fertilizer, and particularly relates to a preparation method and application of a biochar-based zinc sulfate fertilizer for relieving zinc deficiency stress of calcareous soil. BACKGROUND

[0002] Zinc is an essential nutrient element for plants, which can promote the synthesis of indole acetic acid in plants. The lack of available zinc in soil will limit the absorption and utilization of zinc by plants, thereby inhibiting photosynthesis and growth of plants, and easily causing poor development of grains and fruits. The soil in the Loess Plateau region of China is a typical calcareous soil, and the lack of available zinc in the soil is widespread.

[0003] Biochar is a stable solid carbon sequestration product obtained by high-temperature pyrolysis of crop straw and other agricultural and forestry plant waste biomass under anaerobic or limited oxygen conditions at 400-700°C. It has a rich pore structure and a large specific surface area, can adsorb and store nutrients, and slowly release them into the soil to improve fertilizer utilization efficiency. In addition, the functional groups on the surface of biochar can form chemical bonds with nutrient ions, further enhancing the slow-release effect of fertilizer nutrients.

[0004] Sulfur has the functions of alkali regulation and sterilization, and can improve the alkalinity of soil after being mixed with biochar, and can form zinc sulfate with zinc oxide. Zinc sulfate fertilizer can simultaneously improve the zinc and sulfur nutrition of crops, and is one of the most common zinc fertilizers in agricultural production due to its relatively low price, high water solubility, and suitability for most soil types.

[0005] Chinese invention patent CN202111043650.0 discloses a preparation method of a zinc-efficient corn special fertilizer suitable for calcareous soil. The invention increases the spraying of sulfur and zinc oxide powder on the basis of the existing corn fertilizer, and is coated with a bio-based polyurethane film. However, the preparation process of the bio-based polyurethane film in this method is complex and has a high cost, and the existing fertilizer has low efficiency in improving the available zinc in soil. SUMMARY

[0006] The present application aims to provide a preparation method and application of a biochar-based zinc sulfate fertilizer for relieving zinc deficiency stress of calcareous soil, to solve the problems raised in the background art. The application of the biochar-based zinc sulfate fertilizer can significantly improve the available zinc in zinc-deficient soil and weaken the negative effects of calcareous soil on nutrient absorption by plant roots.

[0007] In a first aspect, the present application provides a biochar-based zinc sulfate fertilizer for relieving zinc deficiency stress of calcareous soil, which comprises a mother granule and a first coating, a second coating and a third coating successively coated on the surface of the mother granule.

[0008] The mother granule is made by mixing urea, diammonium phosphate and potassium sulfate and granulating;

[0009] The first coating layer comprises sulfur, bentonite;

[0010] The second coating layer comprises zinc oxide powder, ammonium bicarbonate, ammonia;

[0011] The third coating layer comprises biochar;

[0012] The mass ratio of urea, diammonium phosphate and potassium sulfate in the biochar-based zinc sulfate fertilizer is 7.8-8.0:6.1-6.3:1.7-1.9;

[0013] The mass ratio of sulfur and bentonite is 1.0:0.19-0.21;

[0014] The mass ratio of zinc oxide powder, ammonium bicarbonate and ammonia is 1.0:0.14-0.16:0.09-0.11;

[0015] The mass ratio of urea, sulfur and zinc oxide powder is 7.8-8.0:0.79-8:1.0; the biochar accounts for 5.0%-6.0% of the mass of the biochar-based zinc sulfate fertilizer.

[0016] The biochar-based zinc sulfate fertilizer of the application can improve the utilization efficiency of fertilizer, improve the soil calcareousness while improving the zinc content of crop grains, thereby indirectly improving the effective zinc content of the soil, and the effect is significantly stronger than that of pure zinc sulfate heptahydrate with the same zinc content.

[0017] Further, the diameter of the master batch is 3-5 mm.

[0018] Further, the biochar is corn straw biochar.

[0019] In a second aspect, the application provides a preparation method of the biochar-based zinc sulfate fertilizer for relieving the zinc deficiency stress of calcareous soil, comprising the following steps:

[0020] S1, crushing urea, diammonium phosphate and potassium sulfate, mixing uniformly according to a mass ratio of 7.8-8.0:6.1-6.3:1.7-1.9, and extruding into master batches with a diameter of 3-5 mm;

[0021] S2, mixing sulfur, bentonite and water according to a mass ratio of 1.0:0.19-0.21:5.8-6.2 to form a sulfur mixture; mixing zinc oxide powder, ammonium bicarbonate and ammonia according to a mass ratio of 1.0:0.14-0.16:0.09-0.11 to form a zinc oxide powder solution; preparing biochar with corn straw as raw material, and mixing biochar powder and water to form a biochar suspension;

[0022] S3, spraying the sulfur mixture on the surface of the master batch, and drying to obtain a master batch coated with the first coating layer;

[0023] S4, spraying the zinc oxide powder liquid on the first coating coated master batch, drying to obtain a second coating coated master batch;

[0024] S5, spraying the biochar suspension on the second coating coated master batch, drying to obtain the biochar-based zinc sulfate fertilizer.

[0025] Further, the preparation of the biochar in S2 includes the following steps:

[0026] The corn straw is sequentially crushed, dried, pyrolyzed, steam activated, and cooled and collected to obtain the biochar.

[0027] Further, the pyrolysis conditions are: temperature 480-500℃, pyrolysis time 1.5-2h, and oxygen-free environment; the steam activation conditions are: temperature 850-900℃, activation time 1-1.5h, and water vapor dosage 420-450g·h -1 .

[0028] Further, the moisture content of the first coating coated master batch is less than 15%, and the moisture content of the second coating coated master batch and the biochar-based zinc sulfate fertilizer is less than 1%.

[0029] In a third aspect, the application provides the use of the biochar-based zinc sulfate fertilizer for relieving the zinc deficiency stress of calcareous soil.

[0030] In a fourth aspect, the application provides the use of the biochar-based zinc sulfate fertilizer for promoting growth.

[0031] Further, the crops include calcareous zinc-deficient soil wheat, dry land soil winter wheat, and dry land zinc-deficient soil corn.

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

[0033] 1) The biochar-based zinc sulfate fertilizer can directly increase the soil available zinc by supplementing zinc fertilizer, and can indirectly increase the soil available zinc by reducing the root system pH through sulfur, effectively relieving the zinc deficiency stress of the calcareous soil in the Loess Plateau region of China.

[0034] 2) The biochar-based zinc sulfate fertilizer can supplement the soil available zinc content, and has a high specific surface area and rich surface functional groups after being wrapped with biochar, which can slow down the release of nitrogen, phosphorus and potassium nutrients in the fertilizer and reduce nutrient loss.

[0035] 3) The zinc sulfate fertilizer prepared by taking biochar as the base has the characteristics of being more economical, simpler, and more environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 Flow chart for preparing biochar with corn stalk as raw material.

[0037] Figure 2 Flow chart for ultrasonic spraying of biochar. DETAILED DESCRIPTION

[0038] In order to more clearly illustrate the present application, the technical features, objects and beneficial effects of the present application are more clearly understood, the technical solutions of the present application are described in detail as follows, but cannot be understood as limiting the scope of the present application.

[0039] The present application provides a preparation method and application of a biochar-based zinc sulfate fertilizer for relieving zinc deficiency stress of calcareous soil, and the inventive concept is as follows:

[0040] Step 1, preparation of biochar from corn stalk (see flow chart for preparation Figure 1 ), the specific steps are as follows:

[0041] Collect and crush corn stalks: collect corn stalks and crush them using a crusher to increase the contact area with the pyrolysis equipment.

[0042] Dry the corn stalks: dry the uniformly crushed stalks at a temperature of 250℃ for 0.8h to reduce the water content of the stalks.

[0043] Anaerobic pyrolysis under high temperature conditions: dry the corn stalks under anaerobic conditions while considering their economic efficiency and biochar quality, set the temperature to 500℃, and pyrolyze for 2h under anaerobic conditions.

[0044] Steam activation: set the temperature to 900℃, and the water vapor dosage to 420-450g·h -1 , let the water vapor at high temperature react with the carbon for 1.5h to increase the porosity and surface area of the biochar.

[0045] Cooling and collection: after pyrolysis, the generated biochar is cooled to room temperature and collected.

[0046] Storage and application: the carbon content of the prepared biochar is about 50%-60%, and it is cold-dried and stored for subsequent production of carbon-based zinc sulfate fertilizer. Step 2, based on the results of the previous winter wheat field networking test, the analysis formula of the biochar-based zinc sulfate fertilizer N-P2O5-K2O-Zn is 25-15-5-4. The raw materials for providing nitrogen, phosphorus, potassium and zinc are urea, diammonium phosphate, potassium sulfate and zinc oxide powder, and their mass fractions in the fertilizer are calculated to be 39.5%, 31%, 9% and 5% respectively, so the mass ratio of the four raw materials in the fertilizer can be 7.8-8.0:6.1-6.3:1.7-1.9:1.0.

[0047] Step 3, based on the actual demand for the increase in the effective zinc content of the northern calcareous soil, the amount of zinc oxide is calculated:

[0048]

[0049] C is the amount of zinc oxide, in kg / hm 2 , X is the increase in the effective zinc content (mg / kg), that is, the target increase in the zinc content after one year of applying the biochar-based zinc sulfate fertilizer. Y is the soil bulk density, in g / cm 3 , Z is the thickness of the plough layer, in cm. 65 is the relative atomic mass of Zn, 81 is the relative molecular mass of ZnO, and 65 / 81 is the mass fraction of zinc in zinc oxide. 10 is a unit conversion constant. The adjustment coefficient A1 is 1.2 to compensate for the adsorption and fixation of zinc by the northern cold climate and calcareous soil.

[0050] Since the mass fraction of pure zinc in the biochar-based zinc sulfate fertilizer is 15%, we have:

[0051]

[0052] Therefore, the amount of fertilizer (kg / hm 2 ) can be calculated as follows:

[0053]

[0054] Step 4, based on the amount of zinc oxide and the actual demand for improving the pH of the soil root system, the amount of sulfur is calculated (for zinc oxide, sulfur is in excess, part of the sulfur is oxidized to form zinc sulfate, and the other part is used for alkali adjustment and sterilization of calcareous soil):

[0055]

[0056] 32 is the relative atomic mass of S, and 81 is the relative molecular mass of ZnO. In the case where the product is zinc sulfate and sulfur is sufficient, the ratio of the amounts of sulfur and zinc oxide is equal to the ratio of their molar masses. The adjustment coefficient A2 is 2.0 to ensure that after the sulfur and zinc oxide are fully reacted, there is still some sulfur available for alkali adjustment and sterilization. According to this formula, the mass ratio of sulfur to zinc oxide powder is 0.79:1.0.

[0057] The method for quantitatively applying sulfur provided by the present application can calculate the required amount of sulfur to be applied according to the target increase in the effective zinc content of the soil, avoiding excessive acidification of the soil by sulfur, resource waste, and other problems.

[0058] Step 4, based on the research and previous test results of others, the spraying coating amount of biochar in 100 kg biochar-based zinc sulfate fertilizer can be 5% to 10% of the total weight, i.e. 5 kg to 10 kg. Considering that biochar, zinc oxide and sulfur in the product will be used as a coating together, in order to avoid the coating being too thick, only 5.0% to 6.0% of the total mass of biochar-based zinc sulfate fertilizer is used:

[0059] Biochar dosage (kg / hm 2 ) = Fertilizer dosage (kg / hm 2 ) x 5.0%.

[0060] Step 5, mix sulfur, bentonite and water according to the mass ratio of 1.0:0.19-0.21:5.8-6.2 to form a sulfur mixture; mix zinc oxide powder, ammonium bicarbonate and ammonia water according to the mass ratio of 1.0:0.14-0.16:0.09-0.11 to form a zinc oxide powder solution.

[0061] Step 6, crush urea, diammonium phosphate and potassium sulfate, screen through a 50-100 mesh screen to ensure fine and uniform particles, then mix them evenly. Next, use an extruder to extrude the mixed material into fertilizer masterbatch with a diameter of 3-5 mm;

[0062] Step 7, place the fertilizer masterbatch into a rotating drum, set the rotation speed to 300-350 rpm, and evenly spray the sulfur mixture while rotating, then dry to a moisture content of less than 15% after spraying is complete, to obtain the first fertilizer product;

[0063] Step 8, place the first fertilizer product into a rotating drum, set the rotation speed to 300-350 rpm, and evenly spray the zinc oxide powder solution while rotating, then place it in a drying box for complete drying (moisture content not higher than 1%), to obtain the second fertilizer product;

[0064] Step 9, use ultrasonic spraying technology to spray biochar onto the surface of the second fertilizer product to obtain the final product of biochar-based zinc sulfate fertilizer (see flowchart Figure 2 ), the specific steps are as follows:

[0065] Prepare biochar and fertilizer masterbatch, mix the powdered biochar with water according to a solid-liquid mass ratio of 25 wt% to form a uniform suspension, and set the frequency of the ultrasonic waves (generally 30 kHz to 120 kHz) to adapt to the viscosity of the suspension.

[0066] Place the fertilizer masterbatch into the ultrasonic spraying equipment.

[0067] The liquid flow rate is set to 50 mL / min, the gas pressure flow rate is adjusted, the gas pressure is stabilized at 0.5-1.0 bar, the gas flow rate is set to 10 L / min, and the ultrasonic frequency is adjusted.

[0068] The ultrasonic generator is turned on to atomize the biochar, and the molding gas guide spray is turned on to atomize and spray the biochar suspension to the surface of the fertilizer master batch. After spraying, the uniformity of the coating and whether the thickness reaches 150 μm (in the case of uniform coating, the sulfur-zinc oxide-biochar coating accounts for 14-16% of the total weight of the fertilizer master batch) are checked. If it does not meet the standard, secondary spraying is performed. If it meets the standard, it is dried in a drying oven until completely dry, and is stored or applied.

[0069] The application will be described in detail below in conjunction with specific examples, but should not be understood as limiting the application. If not specifically stated, the technical means used in the following examples are conventional means familiar to those skilled in the art, and the materials, reagents, etc. used in the following examples, if not specifically stated, can be obtained from commercial channels.

[0070] Example 1

[0071] A method for applying biochar-based zinc sulfate fertilizer to improve the available zinc content of a loess plateau calcareous zinc-deficient soil. The biochar-based zinc sulfate is uniformly spread on the ground, and a rotary tiller is used to mix and turn the soil to a depth of 20-30 cm.

[0072] The test site is a typical zinc-deficient calcareous soil with a soil bulk density of 1.22 g / cm 3 , an available zinc content of 0.45 mg / kg, and a pH of 8.30.

[0073] The biochar-based zinc sulfate fertilizer is applied on September 19, 2022, and the soil is turned to a depth of 26 cm.

[0074] The target soil nutrient content is an available zinc content of (0.45+4.00) mg / kg.

[0075] Based on the calculation formula, the amounts of zinc oxide, fertilizer, biochar, and sulfur are determined; based on the ratio of the quantitative components, the amounts of nitrogen, phosphorus, and potassium raw materials, urea, diammonium phosphate, and potassium sulfate, are determined. All raw material dosages are accurate to one decimal place:

[0076]

[0077] Biochar dosage (kg / hm 2 ) = 101.1 x 5.0% = 5.1 (kg / hm 2 ).

[0078] The mass ratio of urea, diammonium phosphate, potassium sulfate, and zinc oxide powder in the fertilizer is 7.8-8.0:6.1-6.3:1.7-1.9:1.0. Other raw materials are added except for zinc oxide powder, and the final fertilizer dosage is (101.1±5%) kg / hm 2 . Based on the fact that the mass fraction of pure zinc in the biochar-based zinc sulfate fertilizer is 15%, in the control group, zinc sulfate heptahydrate with a pure zinc content of 22.0% is applied at the same dosage of (101.1±5%) kg / hm 2 .

[0079] Table 1 Effect of applying zinc fertilizer on soil available zinc content and pH

[0080]

[0081] Note: The data in this table is from the test on the dry land on the terrace in Shilipu Village, Dingjia Town, Changwu County (measured on September 16, 2023). “—” indicates that the data is not included.

[0082] After applying the biochar-based zinc sulfate fertilizer for one year, the soil available zinc content is improved, and the soil pH is reduced. Among them, the improvement value of the soil available zinc content is roughly close to the theoretical target value, and the effect is relatively ideal.

[0083] Example 2

[0084] A method for applying biochar-based zinc sulfate fertilizer to promote growth in a loess plateau calcareous zinc-deficient soil. The biochar-based zinc sulfate is uniformly applied to the ground, and the mixture is turned into the soil using a rotary tiller, with a tillage depth of 20-30 cm.

[0085] The test crop is winter wheat in a calcareous zinc-deficient soil, with a soil bulk density of 1.25 g / cm 3 , a soil available zinc content of 0.53 mg / kg, a pH of 8.25, a winter wheat grain zinc content of 27.7 mg / kg, and a grain zinc content of.

[0086] The biochar-based zinc sulfate fertilizer is applied on September 15, 2022, and the tillage soil depth is 25 cm.

[0087] The target winter wheat yield is (28.2+5.0) mg / kg for winter wheat grain zinc content, and (2097+500) kg / hm 2 .

[0088] Based on the calculation formula, the dosages of zinc oxide, fertilizer, biochar, and sulfur are determined; based on the proportioning of quantitative components, the dosages of nitrogen, phosphorus, and potassium raw materials, urea, diammonium phosphate, and potassium sulfate, are determined. All raw material dosages are accurate to one decimal place:

[0089]

[0090] Biochar dosage (kg / hm 2 ) = 100.0 x 5.0% = 5.0 (kg / hm 2 ).

[0091] The mass ratio of urea, diammonium phosphate, potassium sulfate, and zinc oxide powder in the fertilizer is 7.8-8.0:6.1-6.3:1.7-1.9:1.0, and other raw materials are added except for zinc oxide powder, so that the final fertilizer dosage is (100.0±5%) kg / hm 2 . Based on the fact that the mass fraction of pure zinc in the biochar-based zinc sulfate fertilizer is 15%, in the control group, zinc sulfate heptahydrate with a pure zinc content of 22.0% is applied, and the application amount is also (100.0±5%) kg / hm 2 .

[0092] Table 2 Effect of zinc fertilizer application on winter wheat grain yield and grain zinc content

[0093]

[0094] Note: The data in this table is measured from the dry land on the terrace in Shilipu Village, Dingjia Town, Changwu County (measured on September 13, 2023)

[0095] It should be noted that when the present application claims involving numerical ranges, both endpoints of each numerical range and any number between the two endpoints can be selected. In order to prevent repetition, the present application describes preferred embodiments.

[0096] Although preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they understand the basic inventive concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0097] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. Application of a biochar-based zinc sulfate fertilizer to alleviate zinc deficiency stress in calcareous soils in promoting wheat growth and increasing zinc content in wheat grains, characterized in that, The biochar-based zinc sulfate fertilizer comprises a master granule and a first coating, a second coating and a third coating coated on the surface of the master granule in sequence; The master granule is made by mixing urea, diammonium phosphate and potassium sulfate and granulating; The first coating comprises sulfur and bentonite; The second coating comprises zinc oxide powder, ammonium bicarbonate and ammonia water; The third coating comprises biochar; The mass ratio of urea, diammonium phosphate and potassium sulfate in the biochar-based zinc sulfate fertilizer is 7.8-8.0:6.1-6.3:1.7-1.9; The mass ratio of sulfur and bentonite is 1.0:0.19-0.21; The mass ratio of zinc oxide powder, ammonium bicarbonate and ammonia water is 1.0:0.14-0.16:0.09-0.11; The mass ratio of urea, sulfur and zinc oxide powder is 7.8-8.0:0.79-8:1.0; and the biochar accounts for 5.0%-6.0% of the mass of the biochar-based zinc sulfate fertilizer.

2. The use of the biochar-based zinc sulfate fertilizer according to claim 1 for alleviating zinc deficiency stress in calcareous soil to promote the growth of wheat and increase the zinc content in wheat grains, characterized in that, The diameter of the master granule is 3-5 mm.

3. The use of the biochar-based zinc sulfate fertilizer according to claim 2 for alleviating zinc deficiency stress in calcareous soil to promote the growth of wheat and increase the zinc content in wheat grains, characterized in that, The biochar is corn straw biochar.

4. The use of the biochar-based zinc sulfate fertilizer of claim 3 for alleviating zinc deficiency stress in calcareous soils in promoting the growth of wheat and increasing the zinc content of wheat grains, characterized in that, The preparation of the biochar-based zinc sulfate fertilizer comprises the following steps: S1, crushing urea, diammonium phosphate and potassium sulfate, uniformly mixing them according to a mass ratio of 7.8-8.0:6.1-6.3:1.7-1.9, and extruding them into master granules with a diameter of 3-5 mm; S2, mixing sulfur, bentonite and water according to a mass ratio of 1.0:0.19-0.21:5.8-6.2 to form a sulfur mixture; mixing zinc oxide powder, ammonium bicarbonate and ammonia water according to a mass ratio of 1.0:0.14-0.16:0.09-0.11 to form a zinc oxide powder solution; and preparing biochar from corn straw, mixing biochar powder and water to form a biochar suspension; S3, spraying the sulfur mixture on the surface of the master granule, drying to obtain a first coating coated master granule; S4, spraying the zinc oxide powder solution on the first coating coated master granule, drying to obtain a second coating coated master granule; S5, spraying the biochar suspension on the second coating coated master granule, drying to obtain the biochar-based zinc sulfate fertilizer.

5. The use of a biochar-based zinc sulfate fertilizer according to claim 4 for alleviating zinc deficiency stress in calcareous soils to promote wheat growth and increase zinc content in wheat grains, characterized in that, The preparation of the biochar in S2 comprises the following steps: The corn straw is sequentially crushed, dried, pyrolyzed, steam activated and cooled and collected to obtain the biochar.

6. The use of a biochar-based zinc sulfate fertilizer according to claim 5 for alleviating zinc deficiency stress in calcareous soils to promote wheat growth and increase zinc content in wheat grains, characterized in that, The pyrolysis conditions are: temperature 480-500℃, pyrolysis time 1.5-2h, oxygen-free environment; the steam activation conditions are: temperature 850-900℃, activation time 1-1.5h, water vapor amount 420-450g·h -1 .

7. The use of a biochar-based zinc sulfate fertilizer according to claim 6 for alleviating zinc deficiency stress in calcareous soils to promote wheat growth and increase zinc content in wheat grains, characterized in that, The water content of the first coating coated master granule is less than 15%, and the water content of the second coating coated master granule and the biochar-based zinc sulfate fertilizer is less than 1%.

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