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

Abstract

The invention belongs to the technical field of charcoal-based fertilizers, and particularly relates to a preparation method and application of a charcoal-based zinc sulfate fertilizer for relieving calcareous soil zinc deficiency stress. The biochar-based zinc sulfate fertilizer comprises a master batch, and a first coating, a second coating and a third coating which are sequentially coated on the surface of the master batch, the master batch 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; the third coating comprises biochar; the charcoal-based zinc sulfate fertilizer can quickly and efficiently increase the effective zinc content of the loess plateau calcareous soil so as to cope with the zinc deficiency stress of the soil and promote the growth of crops.

Description

Technical Field

[0001] The invention belongs to the technical field of biochar-based fertilizers, and particularly relates to a preparation method and application of a biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil. Background Art

[0002] Zinc is an essential nutrient for plants and can promote the synthesis of indoleacetic acid in plants. The lack of effective zinc in the soil will limit the absorption and utilization of zinc in plants, thereby inhibiting plant photosynthesis and growth, and easily causing symptoms such as poor development of seeds and fruits. The soil in the Loess Plateau region of my country is a typical calcareous soil, and the lack of effective zinc in the soil is common.

[0003] Biochar refers to a stable solid carbon product obtained by thermal cracking crop straw and other agricultural and forestry plant waste biomass under anaerobic or oxygen-limited conditions at 400-700℃. It has a rich pore structure and a large specific surface area. It 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 also form chemical bonds with nutrient ions, further enhancing the slow-release effect of fertilizer nutrients.

[0004] Sulfur has the functions of adjusting alkali and sterilizing. When mixed with biochar, it can improve soil alkalinity and form zinc sulfate with zinc oxide. Zinc sulfate fertilizer can improve the zinc and sulfur nutrition of crops at the same time. It is one of the most common zinc fertilizers in agricultural production because of its relatively low price, high water solubility and suitability for most soil types.

[0005] Chinese invention patent CN202111043650.0 discloses a method for preparing a zinc-efficient corn fertilizer suitable for calcareous soil. The invention adds spraying of sulfur and zinc oxide powder to the existing corn fertilizer, and coats it with a bio-based polyurethane film. However, the preparation process of the bio-based polyurethane film in this method is complicated and costly, and the efficiency of existing fertilizers in improving effective zinc in the soil is not high. Summary of the invention

[0006] The present invention aims to provide a preparation method and application of a biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil, so as to solve the problems raised in the above background technology. By applying the biochar-based zinc sulfate fertilizer, the effective zinc in zinc-deficient soil is significantly increased, and the negative effect of calcareous soil on nutrient absorption by plant roots is weakened.

[0007] In a first aspect, the present invention provides a biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil, comprising a masterbatch and a first coating, a second coating, and a third coating sequentially coated on the surface of the masterbatch;

[0008] The masterbatch is prepared by mixing urea, diammonium phosphate and potassium sulfate;

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

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

[0011] The third coating 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 to bentonite is 1.0:0.19-0.21;

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

[0015] The mass ratio of the 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 present invention can improve fertilizer utilization efficiency. The fertilizer can improve soil calcareousness while increasing the zinc content of crop grains, thereby indirectly increasing the effective zinc content of the soil, and the increasing effect is significantly stronger than that of zinc sulfate heptahydrate fertilizer with the same pure zinc content.

[0017] Furthermore, the diameter of the masterbatch is 3mm-5mm.

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

[0019] In a second aspect, the present invention provides a method for preparing the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil, comprising the following steps:

[0020] S1. Crush urea, diammonium phosphate and potassium sulfate, mix them in a mass ratio of 7.8-8.0:6.1-6.3:1.7-1.9, and extrude them into master batches with a diameter of 3 mm-5 mm;

[0021] S2, sulfur, bentonite and water are mixed in a mass ratio of 1.0: 0.19-0.21: 5.8-6.2 to form a sulfur mixed liquid; zinc oxide powder, ammonium bicarbonate and ammonia water are mixed in a mass ratio of 1.0: 0.14-0.16: 0.09-0.11 to form a zinc oxide powder liquid; corn stalks are used as raw materials to prepare biochar, and the biochar powder is mixed with water to form a biochar suspension;

[0022] S3, spraying the sulfur mixed liquid on the surface of the masterbatch, and drying to obtain the masterbatch coated with the first coating;

[0023] S4, spraying the zinc oxide powder liquid on the masterbatch coated with the first coating layer, and drying to obtain the masterbatch coated with the second coating layer;

[0024] S5. Spraying the biochar suspension onto the masterbatch coated with the second coating layer, and drying to obtain the biochar-based zinc sulfate fertilizer.

[0025] Furthermore, the preparation of biochar of S2 comprises the following steps:

[0026] The corn stalks are sequentially subjected to crushing, drying, pyrolysis, steam activation, cooling and collection processes to obtain the biochar.

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

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

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

[0030] In a fourth aspect, the present invention provides the use of the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil in promoting plant growth.

[0031] Furthermore, the crops include wheat grown in calcareous zinc-deficient soil, winter wheat grown in dryland soil, and corn grown in dryland zinc-deficient soil.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1) Biochar-based zinc sulfate fertilizer can directly increase soil available zinc by supplementing zinc fertilizer, and can also indirectly increase soil available zinc by lowering root pH through sulfur, effectively alleviating zinc deficiency stress in calcareous soils in the Loess Plateau region of my country.

[0034] 2) Biochar-based zinc sulfate fertilizer not only supplements the effective zinc content in the soil, but also, with the high specific surface area and rich surface functional groups after being wrapped in biochar, has a slow-release effect on nitrogen, phosphorus and potassium nutrients in the fertilizer and reduces nutrient loss.

[0035] 3) Zinc sulfate fertilizer prepared with biochar as the base is more economical, simpler and more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Flow chart of biochar preparation using corn stover as raw material.

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

[0038] In order to more clearly illustrate the present invention and have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

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

[0040] Step 1: Preparation of biochar from corn stalks (see the production flow chart) 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] Drying corn stalks: Dry the evenly crushed stalks at 250°C for 0.8h to reduce the moisture content of the stalks.

[0043] Anaerobic pyrolysis under high temperature conditions: The dried corn stalks were heated under anaerobic conditions. Considering its economy and biochar quality, the temperature was set to 500 °C and the pyrolysis time was 2 h in an anaerobic environment.

[0044] Steam activation: set the temperature to 900°C, steam dosage 420-450g·h -1 , allowing high temperature water vapor to react with the charcoal for 1.5 hours to activate it, increasing 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 obtained biochar is about 50% to 60%, and it is stored in cold and dry conditions for subsequent production of carbon-based zinc sulfate fertilizer. Step 2, based on the results of the previous winter wheat field networking test, the analytical 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. After calculation, their mass fractions in the fertilizer are 39.5%, 31%, 9%, and 5%, respectively. 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: Calculate the amount of zinc oxide based on the actual demand for the increase in the effective zinc content in the northern calcareous soil:

[0048]

[0049] C is the amount of zinc oxide, in kg / hm 2 , X is the increase in effective zinc content (mg / kg), that is, the target increase in zinc content after one year of application of biochar-based zinc sulfate fertilizer. Y is the soil bulk density, in g / cm 3 , Z is the thickness of the tillage 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 the unit conversion constant. The adjustment coefficient A1 is 1.2 to compensate for the adsorption and fixation of zinc by the cold climate and calcareous soil in the north.

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

[0051]

[0052] From this, the fertilizer dosage (kg / hm 2 ):

[0053]

[0054] Step 4, based on the amount of zinc oxide and the actual need to improve the soil root pH, calculate the amount of sulfur (for zinc oxide, sulfur is excessive, part of the sulfur is oxidized into acid and then reacts with zinc oxide 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. When the product is zinc sulfate and sulfur is sufficient, the dosage ratio of sulfur to zinc oxide is equal to the ratio of their molar masses. The adjustment coefficient A2 is 2.0, so that after sulfur and zinc oxide fully react, some sulfur can still be used 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 invention can calculate the amount of sulfur required to be applied according to the amount of increase in the target effective zinc content in the soil, thereby avoiding problems such as excessive acidification of the soil by sulfur and waste of resources.

[0058] Step 4, based on the research of others and the results of previous tests, the amount of biochar spray coating in 100kg of biochar-based zinc sulfate fertilizer can be 5% to 10% of the total weight, that is, 5kg to 10kg. Considering that the biochar, zinc oxide and sulfur in this product will be used together as a coating, in order to avoid excessive coating thickness, only 5.0% to 6.0% of the total weight of biochar-based zinc sulfate fertilizer is used:

[0059] Biochar dosage (kg / hm 2 ) = fertilizer dosage (kg / hm 2 )×5.0%.

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

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

[0062] Step 7, putting the fertilizer masterbatch into a rotating drum, setting the rotating speed of the rotating drum to 300-350 rpm, spraying the sulfur mixed liquid evenly while rotating, and drying to a water content of less than 15% after spraying, to obtain a first fertilizer product;

[0063] Step 8, placing the first fertilizer product in a rotating drum again, setting the rotating speed of the drum to 300-350 rpm, spraying the zinc oxide powder liquid evenly while rotating, and then placing it in a drying oven to be completely dried (water content is not higher than 1%), so as to obtain a second fertilizer product;

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

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

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

[0067] Set the liquid flow rate to 50 mL / min, adjust the gas pressure flow rate, stabilize the gas pressure between 0.5 and 1.0 bar, and set the ultrasonic frequency at a gas flow rate of 10 L / min.

[0068] Turn on the ultrasonic generator to atomize the biochar, turn on the forming gas to guide the spraying, atomize the biochar suspension and spray it onto the surface of the fertilizer masterbatch. After spraying, check the uniformity of the coating and whether the thickness reaches 150μm (when the coating is sprayed evenly, the sulfur-zinc oxide-biochar coating accounts for 14% to 16% of the total weight of the fertilizer masterbatch). If it does not meet the standard, perform a second spray. If it meets the standard, dry it in a drying oven until it is completely dry, and store or use it.

[0069] The present invention is described in detail below in conjunction with specific examples, but it should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0070] Example 1

[0071] A method for applying biochar-based zinc sulfate fertilizer to calcareous zinc-deficient soil on the Loess Plateau to increase the effective zinc content of the soil. The biochar-based zinc sulfate is evenly spread on the surface of the ground, and the mixture is turned into the soil using a rotary tiller, with a tillage depth of 20 cm to 30 cm.

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

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

[0074] Target soil nutrient content: soil available zinc is (0.45+4.00) mg / kg.

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

[0076]

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

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

[0079] Table 1 Effects of zinc fertilizer application on soil available zinc content and pH

[0080]

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

[0082] After one year of applying biochar-based zinc sulfate fertilizer, the soil effective zinc content increased and the soil pH decreased. The increase in soil effective zinc content was roughly close to the theoretical target value, and the effect was relatively ideal.

[0083] Example 2

[0084] A method for promoting the growth of plants by applying biochar-based zinc sulfate fertilizer to calcareous zinc-deficient soil on the Loess Plateau. The biochar-based zinc sulfate is evenly spread on the ground surface, and the mixture is turned into the soil using a rotary tiller, with a tillage depth of 20 cm to 30 cm.

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

[0086] The biochar-based zinc sulfate fertilizer was applied on September 15, 2022, and the soil was plowed to a depth of 25 cm.

[0087] Target winter wheat yield: Winter wheat grain zinc content is (28.2+5.0) mg / kg, winter wheat yield is (2097+500) kg / hm 2 .

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

[0089]

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

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

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

[0093]

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

[0095] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0096] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

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

Claims

1. A biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil, characterized in that: It comprises a masterbatch and a first coating, a second coating and a third coating sequentially coated on the surface of the masterbatch; The masterbatch is prepared by mixing urea, diammonium phosphate and potassium sulfate; The first coating layer 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 to bentonite is 1.0:0.19-0.21; The mass ratio of the zinc oxide powder, ammonium bicarbonate and ammonia water is 1.0: 0.14-0.16: 0.09-0.11; The mass ratio of the 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.

2. The biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 1, characterized in that: The diameter of the masterbatch is 3mm-5mm.

3. The biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 2, characterized in that: The biochar is corn straw biochar.

4. The method for preparing the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 3, characterized in that: The following steps are involved: S1. Crush urea, diammonium phosphate and potassium sulfate, mix them in a mass ratio of 7.8-8.0:6.1-6.3:1.7-1.9, and extrude them into master batches with a diameter of 3 mm-5 mm; S2, mixing sulfur, bentonite and water in a mass ratio of 1.0:0.19-0.21:5.8-6.2 to form a sulfur mixed liquid; mixing zinc oxide powder, ammonium bicarbonate and ammonia water in a mass ratio of 1.0:0.14-0.16:0.09-0.11 to form a zinc oxide powder liquid; Using corn stalks as raw materials, biochar is prepared by mixing biochar powder with water to form a biochar suspension; S3, spraying the sulfur mixed liquid on the surface of the masterbatch, and drying to obtain the masterbatch coated with the first coating; S4, spraying the zinc oxide powder liquid on the masterbatch coated with the first coating layer, and drying to obtain the masterbatch coated with the second coating layer; S5. Spraying the biochar suspension onto the masterbatch coated with the second coating layer, and drying to obtain the biochar-based zinc sulfate fertilizer.

5. The method for preparing the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 4, characterized in that: The preparation of biochar of S2 comprises the following steps: The corn stalks are sequentially subjected to crushing, drying, pyrolysis, steam activation, cooling and collection processes to obtain the biochar.

6. The method for preparing the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 5, characterized in that: The pyrolysis conditions are: temperature 480-500°C, pyrolysis time 1.5-2h, oxygen-free environment; the steam activation conditions are: temperature 850-900°C, activation time 1-1.5h, water vapor dosage 420-450g·h -1 .

7. The method for preparing the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 6, characterized in that: The moisture content of the masterbatch coated with the first coating is less than 15%, and the moisture content of the masterbatch coated with the second coating and the biochar-based zinc sulfate fertilizer is less than 1%.

8. Use of the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to any one of claims 1 to 3 in alleviating zinc deficiency stress in calcareous soil.

9. Use of the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to any one of claims 1 to 3 in promoting plant growth.

10. Use of the biochar-based zinc sulfate fertilizer for alleviating zinc deficiency stress in calcareous soil according to claim 9 in promoting crop growth.

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