阅读说明：本技术 一种调节碱性土壤的中微量元素肥及其制备方法 (Medium trace element fertilizer for regulating alkaline soil and preparation method thereof ) 是由 高进华 高旺香 张广忠 徐勤政 马瑞成 王婷婷 周丽 高文胜 于 2021-10-30 设计创作，主要内容包括：本发明公开了一种调节碱性土壤的中微量元素肥及其制备方法,按质量分数计,由40-60％含中微量元素物质,30-50％酸性物质,1-10％助剂组成；中微量元素为含有钙、镁、硅、硫、铁、锰、铜、锌、硼、钼中两种或两种以上元素的混合物；酸性物质为硫酸脲、柠檬酸、亚甲基丁二酸、顺丁烯二酸、乙二酸、乙酸、己二烯酸中一种或两种以上混合物；助剂为黄原胶、瓜尔胶、生化黄腐酸、糖蜜、壳寡糖、乙二醇、聚乙二醇、乙醇胺中一种或者两种以上混合物。本发明一方面补充土壤中微量元素,另一方面改善土壤PH值,促进农作物对中微量元素的吸收。(The invention discloses a medium trace element fertilizer for regulating alkaline soil and a preparation method thereof, wherein the medium trace element fertilizer consists of 40-60% of medium trace element-containing substances, 30-50% of acidic substances and 1-10% of auxiliary agents in percentage by mass; the medium trace element is a mixture containing two or more of calcium, magnesium, silicon, sulfur, iron, manganese, copper, zinc, boron and molybdenum; the acidic substance is one or more of urea sulfate, citric acid, itaconic acid, maleic acid, oxalic acid, acetic acid and hexadienoic acid; the auxiliary agent is one or a mixture of more than two of xanthan gum, guar gum, biochemical fulvic acid, molasses, chitosan oligosaccharide, glycol, polyethylene glycol and ethanolamine. The invention supplements trace elements in soil on one hand, improves the pH value of the soil on the other hand, and promotes the absorption of the trace elements in crops.)

1. A medium trace element fertilizer for regulating alkaline soil and a preparation method thereof are characterized in that: the fertilizer consists of, by mass, 40-60% of medium and trace element-containing substances, 30-50% of acidic substances and 1-10% of auxiliaries.

2. The fertilizer as claimed in claim 1, wherein the medium trace element is a mixture of two or more of Ca, Mg, Si, S, Fe, Mn, Cu, Zn, B and Mo.

3. The fertilizer as claimed in claim 1, wherein the acidic substance is one or more of urea sulfate, citric acid, itaconic acid, maleic acid, oxalic acid, acetic acid, and adipic acid.

4. The fertilizer as claimed in claim 1, wherein the adjuvant is one or more of xanthan gum, guar gum, biochemical fulvic acid, molasses, chitosan oligosaccharide, glycol, polyethylene glycol and ethanolamine.

5. The medium trace element fertilizer for regulating alkaline soil and the preparation method thereof as claimed in claim 1, wherein the preparation method of the medium trace element fertilizer for regulating alkaline soil comprises the following steps:

the method comprises the following steps: mixing citric acid, itaconic acid, maleic acid and appropriate amount of water, heating to 50-80 deg.C, reacting for 30 min; adding the auxiliary agent into the mixed solution, reducing the temperature to 40-50 ℃, and continuing to react for 30min to obtain a mixed solution A;

step two: fully mixing the medium trace element substances, and crushing to keep the fineness of about 100 meshes to obtain a mixture B;

step three: putting the mixture B into a disc granulator or a roller granulator, keeping the rotating speed, slowly and uniformly adding the solution A into the granulator to prepare a granulated fertilizer C with the granularity of 1.0-2.0 mm;

step four: heating urea sulfate to molten state, spraying and wrapping onto the granules C to make the wrapping thickness of the surface layer be 0.5-1.5mm, cooling to normal temperature, and making into granules D with granularity of 1.5-3.5 mm.

6. The fertilizer as claimed in claim 5, wherein the disk granulator comprises a base, a granulation disk, an arc baffle, a splitter plate, a linear baffle, a gantry, a locking device, a motor, a reducer, a connecting rod I, an adjusting gear, a limiting block, an adjusting rack, an adjusting bolt, a fixing plate, an adjusting screw, a connecting rod II, a telescopic plate, a limiting sleeve, a rotating rod and a locking gear, wherein the rotating rod is movably mounted above the base, the locking gear is arranged at one end of the rotating rod, the locking device is arranged outside the locking gear, the gantry is fixedly mounted on the rotating rod, the granulation disk inside the gantry is fixedly mounted at the output end of the reducer, a belt pulley arranged at the input end of the reducer is meshed with a belt pulley arranged at the output end of the motor through a belt, the motor and the reducer are fixedly mounted on the rotating rod, fixed mounting has sharp baffle on the portal frame, sharp baffle one side is equipped with the flow distribution plate, the flow distribution plate is fixed on connecting rod II, II end-to-end connection expansion plates of connecting rod, expansion plate movable mounting is inside spacing sleeve, spacing sleeve fixed mounting is in the portal frame top, II one sides of connecting rod are equipped with connecting rod I, I movable mounting of connecting rod is on the portal frame, I one end of connecting rod is equipped with cowl, other end fixed mounting has adjusting gear, the adjusting gear both sides are equipped with two sets of stoppers, movable mounting has the adjusting rack on the stopper, the adjusting rack is connected with adjusting gear engagement, adjusting rack one end fixed mounting has adjusting screw, adjusting screw movable mounting is on the fixed plate, the fixed plate both sides are equipped with two sets of adjusting bolt, adjusting bolt movable mounting is on adjusting screw.

7. The fertilizer as claimed in claim 6, wherein the locking device comprises a locking cover, a locking rod, a spring, a guide rod, a guide plate, a locking bolt, and a fixed bottom cover, the fixed bottom cover is disposed under the locking gear and fixedly mounted on one side of the base, the locking cover is movably mounted on the fixed bottom cover, the locking bolt is disposed on one side of the locking cover, the guide plate is fixedly mounted on the locking cover, the guide plate is movably mounted on the guide plate, the end of the guide rod is fixedly connected with the locking rod, the spring is disposed between the locking rod and the guide plate, and the locking rods are movably mounted on the locking cover.

Technical Field

The invention belongs to the technical field of fertilizers, and particularly relates to a medium-trace element fertilizer for regulating alkaline soil and a preparation method thereof.

Background

According to data estimated by the national agricultural technology promotion center in 2014, the soil in China is generally lack of medium and trace elements. The contents of calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum and other trace elements in soil in China are respectively 63%, 53%, 40%, 31%, 48%, 25%, 42%, 84% and 59% in the cultivated land area below the critical value. This increased the arable area deficient in medium trace elements by nearly 1-fold compared to the data from the second national soil survey more than 30 years ago.

Because crops have large requirements on a large number of nutrient elements and the influence on the yield is most obvious, the application of medium and trace elements is neglected while only the use of nitrogen, phosphorus and potassium is emphasized in the conventional fertilization habit. However, medium trace elements are very active in plants, widely participate in photosynthesis, respiration, substance transformation and the like of plants, and have no negligible influence on crop quality and yield.

The alkaline soil is soil with the pH value of more than 7. The soil has the advantages of high salt content, drought and waterlogging coexistence, low organic matter content, poor soil physical and chemical properties, poor buffering performance, low water and fertility retention, more anions and cations harmful to crop growth, no contribution to crop growth and low land productivity and bearing capacity.

The alkaline soil has high content of sodium ions due to over high pH value, calcium ions and magnesium ions are replaced to form carbonic acid precipitate, the effectiveness of zinc, iron and manganese elements is reduced, the crop absorption is more difficult, and the alkaline soil is particularly lack of medium and trace elements.

In some medium trace element fertilizers disclosed in the prior art, although medium trace elements are contained, the pH value of soil is not adjusted, and in the process of granulating the fertilizer by using a granulator, bed charge is easy to accumulate and cannot be uniformly dispersed, so that the granulation is not uniform, the inclination angle of a granulation disc cannot be adjusted at will, and the granulation requirements of different specifications cannot be met.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a medium-trace element fertilizer for regulating alkaline soil and a preparation method thereof, which can supplement trace elements in soil, improve the pH value of soil and promote the absorption of medium-trace elements by crops.

In order to achieve the purpose, the invention adopts the technical scheme that:

a granular fertilizer containing medium-trace elements is prepared from medium-trace element (40-60 wt.%), acidic substance (30-50) and assistant (1-10).

The medium trace elements are mixture of two or more elements selected from calcium, magnesium, silicon, sulfur, ferrum, manganese, copper, zinc, boron and molybdenum. Preferably, the raw materials comprise, by mass, 10-20% of magnesium sulfate monohydrate, 18-25% of sulfur powder, 3-5% of ferrous sulfate, 1-3% of zinc sulfate monohydrate, 1-3% of boric acid, 1-3% of copper sulfate pentahydrate, 1-3% of manganese sulfate monohydrate and 1-3% of ammonium heptamolybdate.

Sulphur is a very beneficial element for plant growth, has a variety of roles in plant metabolism, plays an important role in the formation of amino acid proteins in particular, and has a large influence on the synthesis of crop proteins, fats, vitamins and glucose. In certain cases, sulfur plays an important role in the uptake of phosphate by soil. And after the sulfur powder is applied to soil, the propagation of vulcanized bacteria can be promoted, the dissolution of insoluble phosphate can be promoted, and the utilization efficiency of the fertilizer can be improved.

Copper participates in the growth regulation of plants, improves the resistance of crops to drought, heat damage, frost damage and the like, effectively prolongs the service life of leaves and enhances the photosynthetic capacity of the plants. When the crops lack copper, the plants become short and small, the branches and tillering are reduced, the whole plants are faded and are light green or yellow green.

Boron is a reproductive element and affects reproductive organ development. Boron promotes pollen formation and improves fruit setting rate; promoting cell elongation and tissue differentiation; promoting carbohydrate transport and protein metabolism. When the plant lacks boron, the top stops growing and dies gradually, the new leaf stops growing, and adventitious buds are formed on the petioles; the phenomena of bud falling, flower falling and fruit falling are easy to occur, and flowers are not fruited.

Zinc is involved in the synthesis of auxin and chlorophyll and is a component and activator of various enzymes. In the absence of zinc, the growth of the plants is inhibited, especially the internode growth is seriously inhibited, and the internodal greening or whitening symptoms of the leaves are shown; in general, the zinc deficiency of plants results in the decrease of leaves and the shortening of internodes of branches, which also causes the lightening of leaf vein color.

Manganese is a composition substance of chloroplast, promotes synthesis and photosynthesis of plant chlorophyll, and promotes pollen germination, pollen tube elongation and fruit enlargement. When the crops are lack of manganese, the leaves are soft, the veins are dark green, and various metabolic processes of the plants are easy to be caused to touch the walls, so that the yield is reduced. Manganese is an activator of various enzymes in the plant body and can promote the assimilation of chlorophyll and carbohydrates.

Iron is an important component of cytochrome, heme, ferredoxin and various enzymes, plays a role in transferring electrons in plants, and is an essential substance in chlorophyll synthesis. Iron is not easy to move in the plant body, and is firstly displayed on young leaves when the iron is deficient. It is manifested as a greenish-blue pulse, in severe cases, the whole young leaves are yellow-white, and iron deficiency often occurs in alkaline soil.

Molybdenum is an essential element in the minimum required amount. Molybdate ions are a component of azotase, a component of xanthine dehydrogenase and certain oxidases in abscisic acid synthesis. Molybdenum is particularly required for nitrogen fixation in leguminous plant rhizobia, and the nitrogen-fixing enzyme is composed of ferritin and iron-molybdenum protein. Molybdenum deficiency in plants: malformed, blotchy, spread over the leaves; poor growth and short plant; the lack of molybdenum in leguminous plants can affect nitrogen fixation and the pod grains are not full.

The acidic substance is one or a mixture of more than two of urea sulfate, citric acid, itaconic acid, maleic acid, oxalic acid, acetic acid and hexadienoic acid. Preferably, the raw materials comprise, by mass, 28-40% of urea sulfate, 2-5% of citric acid, 2-5% of itaconic acid and 2-5% of maleic acid.

The urea sulfate is weakly acidic and is effective in improving alkaline soil. Compared with urea, urea sulfate has slow release property, nutrients are released according to the requirements of crops under the drive of beneficial microbial bacteria, quick-acting nutrients promote the seedling stage of the crops to grow quickly, long-acting nutrients ensure that the fertilizer is not released at the later stage of the crops, and an appropriate environment is provided for the microorganisms, so that deep soil phosphorus and potassium are activated, and the fixation of the phosphorus and potassium is inhibited. The urea sulfate selected by the invention has the molecular ratio of urea to sulfuric acid of 2: 1 is prepared by the following steps.

In the invention, the citric acid is a solid powder product, and the effective content is more than or equal to 98 percent; the itaconic acid is a solid powder product, and the effective content is more than or equal to 98 percent; the maleic acid is a solid powder product, and the effective content is more than or equal to 98 percent.

The auxiliary agent is one or a mixture of more than two of xanthan gum, guar gum, biochemical fulvic acid, molasses, chitosan oligosaccharide, glycol, polyethylene glycol and ethanolamine. Preferably, the raw materials comprise 2-4% of ethylene glycol and 2-5% of polyethylene glycol by mass percentage.

The research shows that the auxiliary agent is compounded with the acidic substance, so that the utilization rate of the acidic substance can be effectively improved, the acidic substance is slowly released, the utilization rate of the fertilizer efficiency is improved, and the problems of soil hardening, soil salinization and the like caused by alkaline soil are effectively solved.

A preparation method of a medium trace element fertilizer for regulating alkaline soil is characterized by comprising the following steps:

the method comprises the following steps: mixing the citric acid, itaconic acid, maleic acid and a proper amount of water, heating to 50-80 ℃, and reacting for 30 min; adding the auxiliary agent into the mixed solution, reducing the temperature to 40-50 ℃, and continuing to react for 30min to obtain a mixed solution A;

step two: fully mixing the medium trace element substances, and crushing to keep the fineness of about 100 meshes to obtain a mixture B;

step three: putting the mixture B into a disc granulator or a roller granulator, keeping the rotating speed, slowly and uniformly adding the solution A into the granulator to prepare a granulated fertilizer C with the granularity of 1.0-2.0 mm;

step four: heating urea sulfate to molten state, spraying and wrapping onto the granules C to make the wrapping thickness of the surface layer be 0.5-1.5mm, cooling to normal temperature, and making into granules D with granularity of 1.5-3.5 mm.

The disc granulator comprises a base, a granulation disc, an arc-shaped baffle plate, a splitter plate, a linear baffle plate, a portal frame, a locking device, a motor, a speed reducer, a connecting rod I, an adjusting gear, a limiting block, an adjusting rack, an adjusting bolt, a fixing plate, an adjusting screw rod, a connecting rod II, a telescopic plate, a limiting sleeve, a rotating rod and a locking gear, wherein the rotating rod is movably arranged above the base, the locking gear is arranged at one end of the rotating rod, the locking device is arranged outside the locking gear, the portal frame is fixedly arranged on the rotating rod, the granulation disc inside the portal frame is fixedly arranged at the output end of the speed reducer, a belt pulley arranged at the input end of the speed reducer is meshed with a belt pulley arranged at the output end of the motor through a belt, the motor and the speed reducer are fixedly arranged on the rotating rod, the linear baffle plate is fixedly arranged on the portal frame, the splitter plate is arranged on one side of the linear baffle plate and is fixed on the connecting rod II, II end-to-end connection expansion plates of connecting rod, expansion plate movable mounting is inside limit sleeve, limit sleeve fixed mounting is in the portal frame top, II one sides of connecting rod are equipped with connecting rod I, I movable mounting of connecting rod is on the portal frame, I one end of connecting rod is equipped with cowl, other end fixed mounting has adjusting gear, the adjusting gear both sides are equipped with two sets of stoppers, movable mounting has the adjusting rack on the stopper, the adjusting rack is connected with adjusting gear engagement, adjusting rack one end fixed mounting has adjusting screw, adjusting screw movable mounting is on the fixed plate, the fixed plate both sides are equipped with two sets of adjusting bolt, adjusting bolt movable mounting is on adjusting screw.

Locking device includes locking lid, check lock lever, spring, guide bar, deflector, locking bolt, fixed bottom is located locking gear below and fixed mounting in base one side, movable mounting has the locking lid on the fixed bottom, locking lid one side is equipped with the locking bolt, locking lid top fixed mounting has the deflector, movable mounting has a plurality of guide bars on the deflector, the terminal fixed connection check lock lever of guide bar, be equipped with the spring between check lock lever and the deflector, a plurality of check lock lever movable mounting cover in the locking.

Compared with the prior art, the invention has the beneficial effects that:

1) the medium-trace element granular fertilizer prepared by the invention is simple and convenient to apply, and can be used in combination with various granular and powdery compound fertilizers for mixed use or single use; the granularity is between 1.5 and 3.5mm, the granules are small, and the condition of uneven or excessive local fertilization is avoided;

2) the medium and trace element substances prepared by the invention are wrapped in the inner core, and the outer membrane isolates air and water, so that the chemical reaction among various element substances can be effectively controlled, namely the medium and trace element substances have low requirements and can be easily absorbed by crops, and meanwhile, the chemical reaction among the selected medium and trace element substances does not need to be considered;

3) the finished product particles are weakly acidic after being dissolved in water, so that bicarbonate in soil can be effectively neutralized, hydrogen ions can be released, the salt content in the soil can be reduced, the saline-alkali property of the soil can be further improved, the absorption efficiency of plants on soil nutrients can be improved, in addition, fixed phosphorus in the soil can be released, and the utilization rate of fertilizers can be enhanced;

4) the medium-trace element granular fertilizer prepared by the invention contains medium-trace nutrient elements such as sulfur, magnesium, boron, copper, zinc, iron, manganese, silicon and molybdenum required by crops, provides nutrition for the whole growth period of the crops, meets the requirements of the crops on the medium-trace elements in the growth period, and improves the quality of the crops;

5) through add cowl and flow distribution plate in the disc granulator, make fertilizer follow disc granulator pivoted in-process, through cowl and flow distribution plate with fertilizer evenly dispersed, prevent to pile up, and accessible adjusting bolt and expansion plate carry out the regulation of position and angle to flow distribution plate and arc, through setting up locking device in rotary rod one side, locking device is through two rows of cross distribution's guide bar and check lock lever, make the granulation disc can be at arbitrary angle locking, with this requirement that satisfies various fertilizer granulation sizes.

Drawings

FIG. 1 is a schematic structural diagram of a medium trace element fertilizer for regulating alkaline soil and a preparation method thereof;

FIG. 2 is a schematic view of a motor structure;

FIG. 3 is a schematic view of the internal structure of a pelletizing disk;

FIG. 4 is a schematic view of an adjustment gear configuration;

FIG. 5 is a schematic view of a lock gear configuration;

FIG. 6 is a schematic view of the guide bar structure;

FIG. 7 is an enlarged view of a portion of FIG. 5 at A;

in the figure: 10. a base; 11. a granulation disc; 12. an arc-shaped baffle plate; 13. a flow distribution plate; 14. a linear baffle plate; 15. a gantry; 16. a locking device; 17. a motor; 18. a speed reducer; 121. a connecting rod I; 122. an adjusting gear; 123. a limiting block; 124. adjusting the rack; 125. adjusting the bolt; 126. a fixing plate; 127. adjusting the screw rod; 131. a connecting rod II; 132. a retractable plate; 133. a limiting sleeve; 151. rotating the rod; 152. a locking gear; 161. a locking cover; 162. a locking lever; 163. a spring; 164. a guide bar; 165. a guide plate; 166. locking the bolt; 167. and fixing the bottom cover.

Detailed Description

For the convenience of understanding of those skilled in the art, the technical solution of the present invention will be further described in detail with reference to fig. 1 to 7.

Example 1:

a preparation method of a medium trace element fertilizer capable of adjusting alkaline soil comprises the following steps:

1) mixing 2g of citric acid, 2g of itaconic acid, 5g of maleic acid and a proper amount of water, heating to 50-80 ℃, and reacting for 30 min; adding 3g of ethylene glycol and 2g of polyethylene glycol into the mixed solution, reducing the temperature to 40-50 ℃, and continuing to react for 30min to obtain a mixed solution A;

2) uniformly mixing 15g of magnesium sulfate monohydrate, 20g of sulfur powder, 5g of ferrous sulfate, 2g of zinc sulfate monohydrate, 2g of boric acid, 2g of copper sulfate pentahydrate, 2g of manganese sulfate monohydrate and 2g of ammonium heptamolybdate, and grinding to about 100 meshes to obtain a mixture B;

3) putting the mixture B into a disc granulator or a roller granulator, keeping the rotating speed, slowly and uniformly adding the solution A into the granulator to prepare a granulated fertilizer C with the granularity of 1.0-2.0 mm;

the disc granulator comprises a base 10, a granulation disc 11, an arc baffle 12, a splitter plate 13, a linear baffle 14, a portal frame 15, a locking device 16, a motor 17, a speed reducer 18, a connecting rod I121, an adjusting gear 122, a limiting block 123, an adjusting rack 124, an adjusting bolt 125, a fixing plate 126, an adjusting screw 127, a connecting rod II 131, an expansion plate 132, a limiting sleeve 133, a rotating rod 151 and a locking gear 152, wherein the rotating rod 151 is movably installed above the base 10, the locking gear 152 is arranged at one end of the rotating rod 151, the locking device 16 is arranged outside the locking gear 152, the portal frame 15 is fixedly installed on the rotating rod 151, the granulation disc 11 inside the portal frame 15 is fixedly installed at the output end of the speed reducer 18, a belt pulley arranged at the input end of the speed reducer 18 is meshed with a belt pulley arranged at the output end of the motor 17 through a belt, the motor 17 and the speed reducer 18 are fixedly installed on the rotating rod 151, fixed mounting has sharp baffle 14 on portal frame 15, sharp baffle 14 one side is equipped with flow distribution plate 13, flow distribution plate 13 is fixed on connecting rod II 131, connecting rod II 131 end-to-end connection expansion plate 132, expansion plate 132 movable mounting is inside stop sleeve 133, stop sleeve 133 fixed mounting is in portal frame 15 top, connecting rod II 131 one side is equipped with connecting rod I121, connecting rod I121 movable mounting is on portal frame 15, connecting rod I121 one end is equipped with cowl 12, other end fixed mounting has adjusting gear 122, adjusting gear 122 both sides are equipped with two sets of stopper 123, movable mounting has adjusting rack 124 on the stopper 123, adjusting rack 124 is connected with adjusting gear 122 meshing, adjusting rack 124 one end fixed mounting has adjusting screw 127, adjusting screw 127 movable mounting is on fixed plate 126, fixed plate 126 both sides are equipped with two sets of adjusting bolt 125, adjusting bolt 125 movable mounting is on adjusting screw 127.

Locking device 16 includes locking lid 161, locking lever 162, spring 163, guide bar 164, deflector 165, locking bolt 166, fixed bottom 167 is located locking gear 152 below and fixed mounting in base 10 one side, movable mounting has locking lid 161 on the fixed bottom 167, locking lid 161 one side is equipped with locking bolt 166, locking lid 161 top fixed mounting has guide plate 165, movable mounting has a plurality of guide bars 164 on the deflector 165, the terminal fixed connection locking lever 162 of guide bar 164, be equipped with spring 163 between locking lever 162 and the guide plate 165, a plurality of locking levers 162 movable mounting are on locking lid 161.

4) Heating 36g urea sulfate to molten state, spraying to wrap the granules C to make the thickness of the surface layer wrap between 0.5-1.5mm, and cooling to normal temperature to obtain granules D with the granularity of 1.5-3.5 mm.

Example 2

Compared with the embodiment 1, the preparation method of the medium trace element fertilizer capable of regulating the alkaline soil comprises the following steps:

1) mixing 3g of citric acid, 3g of itaconic acid, 3g of maleic acid and a proper amount of water, heating to 50-80 ℃, and reacting for 30 min; adding 2g of ethylene glycol and 3g of polyethylene glycol into the mixed solution, reducing the temperature to 40-50 ℃, and continuing to react for 30min to obtain a mixed solution A;

2) uniformly mixing 17g of magnesium sulfate monohydrate, 18g of sulfur powder, 6g of ferrous sulfate, 2g of zinc sulfate monohydrate, 2g of boric acid, 2g of copper sulfate pentahydrate, 2g of manganese sulfate monohydrate and 2g of ammonium heptamolybdate, and grinding to about 100 meshes to obtain a mixture B;

3) putting the mixture B into a disc granulator or a roller granulator, keeping the rotating speed, slowly and uniformly adding the solution A into the granulator to prepare a granulated fertilizer C with the granularity of 1.0-2.0 mm;

4) heating 35g urea sulfate to molten state, spraying and wrapping onto the granule C to make the wrapping thickness of the surface layer be 0.5-1.5mm, cooling to normal temperature, and making into granule D with particle size of 1.5-3.5 mm.

Example 3

Compared with the embodiment 1, the preparation method of the medium trace element fertilizer capable of regulating the alkaline soil comprises the following steps:

1) mixing 2g of citric acid, 2g of itaconic acid, 5g of maleic acid and a proper amount of water, heating to 50-80 ℃, and reacting for 30 min; adding 3g of ethylene glycol and 3g of polyethylene glycol into the mixed solution, reducing the temperature to 40-50 ℃, and continuing to react for 30min to obtain a mixed solution A;

2) uniformly mixing 16g of magnesium sulfate monohydrate, 18g of sulfur powder, 5g of ferrous sulfate, 2g of zinc sulfate monohydrate, 2g of boric acid, 2g of copper sulfate pentahydrate, 2g of manganese sulfate monohydrate and 2g of ammonium heptamolybdate, and grinding to about 100 meshes to obtain a mixture B;

3) putting the mixture B into a disc granulator or a roller granulator, keeping the rotating speed, slowly and uniformly adding the solution A into the granulator to prepare a granulated fertilizer C with the granularity of 1.0-2.0 mm;

4) heating 36g urea sulfate to molten state, spraying to wrap the granules C to make the thickness of the surface layer wrap between 0.5-1.5mm, and cooling to normal temperature to obtain granules D with the granularity of 1.5-3.5 mm.

Example 4

Compared with the embodiment 1, the preparation method of the medium trace element fertilizer capable of regulating the alkaline soil comprises the following steps:

1) mixing 4g of citric acid, 2g of itaconic acid, 3g of maleic acid and a proper amount of water, heating to 50-80 ℃, and reacting for 30 min; adding 3g of ethylene glycol and 33g of polyethylene glycol into the mixed solution, reducing the temperature to 40-50 ℃, and continuing to react for 30min to obtain a mixed solution A;

2) uniformly mixing 17g of magnesium sulfate monohydrate, 17g of sulfur powder, 5g of ferrous sulfate, 2g of zinc sulfate monohydrate, 2g of boric acid, 2g of copper sulfate pentahydrate, 2g of manganese sulfate monohydrate and 2g of ammonium heptamolybdate, and grinding to about 100 meshes to obtain a mixture B;

3) putting the mixture B into a disc granulator or a roller granulator, keeping the rotating speed, slowly and uniformly adding the solution A into the granulator to prepare a granulated fertilizer C with the granularity of 1.0-2.0 mm;

4) heating 36g urea sulfate to molten state, spraying to wrap the granules C to make the thickness of the surface layer wrap between 0.5-1.5mm, and cooling to normal temperature to obtain granules D with the granularity of 1.5-3.5 mm.

The foregoing is merely exemplary and illustrative of the present invention and various modifications, additions and substitutions may be made by those skilled in the art to the specific embodiments described without departing from the scope of the present invention as defined in the accompanying claims.