CN110590454A

CN110590454A - Slow/controlled release fertilizer and preparation method thereof

Info

Publication number: CN110590454A
Application number: CN201910955834.0A
Authority: CN
Inventors: 周兆媛; 韩德梁; 赵立敏; 王鹤立; 赵欣胜; 李云飞
Original assignee: Beautiful Land (beijing) Ecological Environment Engineering Technology Research Institute Co Ltd
Current assignee: Beautiful Land (beijing) Ecological Environment Engineering Technology Research Institute Co Ltd
Priority date: 2019-10-09
Filing date: 2019-10-09
Publication date: 2019-12-20

Abstract

The invention provides a slow and controlled release fertilizer, which comprises: an inner core of the fertilizer, a binder and an outer coating; wherein, the inner core comprises fertilizer and bentonite, the binder comprises polyvinyl alcohol solution, and the outer coating comprises magnesium ammonium phosphate, super absorbent resin and rooting powder. The slow and controlled release fertilizer comprises the following raw materials in parts by mass: 50-85 parts of chemical fertilizer, 5-10 parts of bentonite, 10-15 parts of binder, 15-25 parts of magnesium ammonium phosphate, 10-20 parts of super absorbent resin and 1-3 parts of rooting powder; the fertilizer comprises a nitrogenous fertilizer, a potash fertilizer and a phosphate fertilizer, and the mass ratio of the nitrogenous fertilizer to the potash fertilizer to the phosphate fertilizer is as follows: (25-38): (12-20): (15-24). The slow-release and controlled-release fertilizer has good slow-release effect.

Description

Slow/controlled release fertilizer and preparation method thereof

Technical Field

The invention belongs to the technical field of slow and controlled release fertilizers, and particularly relates to a slow and controlled release fertilizer and a preparation method thereof.

Background

China is a state with restricted fertilizer resources, the utilization rate of the fertilizer in the season is low, and the utilization rate of the fertilizer is about 30-35 percent, 10-20 percent of the phosphate fertilizer and 35-50 percent of the potash fertilizer. The main components of the fertilizer are nitrogen, phosphorus and potassium, and the fertilizer needs to be extracted from coal mines, phosphorite and potassium ores, but mineral resources in China are limited, particularly the annual inlet amount of potassium fertilizer reaches millions of tons, and the low utilization rate of the fertilizer causes huge resource waste and economic loss. In addition, the average application amount of the fertilizer in China exceeds 440kg/hm²The fertilizer is 3 times of the average application amount of the global fertilizer, and the fertilizer which is not absorbed by crops not only increases the agricultural production cost, but also causes environmental problems such as soil eutrophication, greenhouse effect, water body pollution and the like.

Compared with the traditional fertilizer, the slow-release fertilizer (slow-release fertilizer) has the following advantages: (1) the nutrients are effectively controlled and slowly released, the damage to crop roots due to overhigh local fertilizer concentration is avoided, and the use is safe; (2) the slow controlled release fertilizer is applied once without additional fertilization, thereby reducing the number and times of fertilization and saving labor and cost; (3) nutrient release of the controlled-release fertilizer conforms to the absorption rule of crops, the crops grow more robustly, the stress resistance is improved, and the quality of agricultural products is obviously improved; (4) the slow and controlled release fertilizer can greatly improve the utilization rate of the fertilizer, effectively avoid the volatilization of nitrogen and the loss and fixation of phosphorus and potassium, and reduce the pollution to the environment.

Although the research on the slow and controlled release fertilizer has been greatly advanced, and various fertilizers with good slow and controlled release effects appear, the high production cost is still an important factor for restricting the popularization of the fertilizer. In addition, China is one of countries with water resource shortage, and the total area of arid and semi-arid regions is 455 kilohm²Accounting for 47% of the total area of the homeland. Therefore, the research and development of the biodegradable controlled-release fertilizer with low cost, good slow release property, strong water retention property and biodegradability have important significance for economic development, energy conservation, emission reduction, environmental protection and the like.

A disk granulation method of a granular magnesium ammonium phosphate slow-release fertilizer (CN104150970B) in Chinese patents discloses a disk granulation method of a granular magnesium ammonium phosphate slow-release fertilizer, wherein a magnesium ammonium phosphate material and an acidifier are granulated through a binder, the granular magnesium ammonium phosphate material is dried for 10-30 min at the temperature of 60-100 ℃, and the dried material is screened to obtain a qualified product. The method has the advantages of simple production process and low cost, improves the fertilization efficiency of the magnesium ammonium phosphate, and introduces the acidifying agent to adjust the initial and subsequent nutrient release rates of the magnesium ammonium phosphate according to requirements. The disadvantages are that the method of directly spraying the binder solution for granulation is easy to block the equipment and difficult to spray uniformly, and the formed particles may have non-uniform situation; drying at 60-100 ℃, wherein magnesium ammonium phosphate is decomposed at a temperature higher than 60 ℃ and is dried at 100 ℃ for 30min, so that magnesium ammonium phosphate is almost completely converted into a magnesium hydrogen phosphate product, the ammonium loss is serious, and the effect of slow release fertilizer of magnesium hydrogen phosphate is not reported at present; the technology does not solve the problem of poor fertilizer effect caused by low nutrient content of the magnesium ammonium phosphate slow release fertilizer.

In order to overcome the defects of CN104150970B, the Chinese patent applications of ' a magnesium ammonium phosphate-urea slow release fertilizer and a preparation method thereof ' (CN108467309A) ' a magnesium ammonium phosphate-phosphate fertilizer slow release fertilizer and a preparation method thereof ' (CN108409465A) ' and ' a magnesium ammonium phosphate inorganic-organic cementing fertilizer and a preparation method thereof ' (CN108658662A) use magnesium ammonium phosphate as a wrapping material, and the magnesium ammonium phosphate particles and urea/phosphate fertilizer/organic fertilizer are wrapped by modified starch binder in a layer-by-layer wrapping manner and are granulated to obtain the magnesium ammonium phosphate urea/phosphate fertilizer/organic fertilizer slow release fertilizer. The method has the advantages of solving the technical problems of low nutrient content of the magnesium ammonium phosphate slow release fertilizer, easy blockage of equipment, non-uniform spraying of the binder solution and high-temperature decomposition of magnesium ammonium phosphate, along with simple operation, low cost and capability of effectively controlling the release rate of the fertilizer. The water-absorbing and water-retaining agent has the defects of no water absorbing and water retaining performance and is not suitable for areas with drought, water shortage or large daily evaporation capacity.

Therefore, in the current scientific research and practice, a novel multifunctional slow-release fertilizer with the advantages of sufficient nutrients, good slow release performance, high water absorption, long water retention time, plant stress resistance enhancement, low cost, environmental friendliness and the like needs to be developed.

Disclosure of Invention

The invention provides a slow/controlled release fertilizer and a preparation method thereof, aiming at solving the problems in the prior art.

The invention is realized by the following technical scheme:

aspect I of the invention provides a controlled release fertilizer,

the slow and controlled release fertilizer comprises the following raw materials in parts by mass:

50-85 of chemical fertilizer, 5-10 of bentonite,

10-15 parts of a binder, wherein,

15-25 parts of magnesium ammonium phosphate and 10-20 parts of super absorbent resin;

the fertilizer comprises: nitrogenous fertilizer, potash fertilizer and phosphatic fertilizer.

In some embodiments, the mass ratio of the nitrogenous fertilizer to the potash fertilizer to the phosphate fertilizer is (25-38): (12-20): (15-24).

In some embodiments, the particle size of the nitrogen fertilizer is 1.5-2 mm, the particle size of the potassium fertilizer is 0.1-0.5 mm, and the particle size of the phosphate fertilizer is 0.1-0.5 mm.

In some embodiments, the nitrogen fertilizer is selected from one or more of urea, ammonium sulfate and ammonium nitrate, the potassium fertilizer is selected from one or two of potassium chloride and potassium sulfate, and the phosphate fertilizer is selected from one or two of calcium superphosphate and calcium magnesium phosphate.

In some embodiments, the bentonite is selected from one or both of sodium bentonite and calcium bentonite.

In some embodiments, the binder is a polyvinyl alcohol solution.

In some embodiments, the polyvinyl alcohol solution is an aqueous solution with a mass percentage concentration of 5% to 8%.

In some embodiments, the magnesium ammonium phosphate has a particle size of 0.1 to 0.5 mm.

In some embodiments, the superabsorbent resin is selected from the group consisting of: one or more of sodium polyacrylate, sodium polyacrylate grafted starch, sodium polyacrylate grafted sodium alginate and polyacrylamide.

In some embodiments, the raw materials of the controlled release fertilizer comprise, by mass: 1-3 parts of rooting powder.

In some embodiments, the rooting powder is selected from the group consisting of: one or more of ABT1, ABT2, ABT3, ABT4, ABT5, ABT6, ABT7, ABT8, ABT9 and ABT10 rooting powder.

In some embodiments, the structure of the slow/controlled release fertilizer comprises, in order from the inside to the outside: the core, wrap up the second layer outside the said core, wrap up the third layer outside the said second layer and wrap up the fourth layer outside the said third layer;

the material of the inner core comprises nitrogen fertilizer;

the material of the second layer comprises bentonite and potash fertilizer;

the third layer is made of bentonite and phosphate fertilizer; and

the material of the fourth layer comprises a binder, magnesium ammonium phosphate and a high water absorption resin;

preferably, the material of the fourth layer of the controlled release fertilizer also comprises rooting powder.

Aspect II of the present invention provides a slow/controlled release fertilizer, which comprises the following components in sequence from inside to outside: the inner core, the second layer, the third layer and the fourth layer;

the material of the inner core comprises nitrogen fertilizer;

the material of the second layer comprises bentonite and potash fertilizer;

the third layer is made of bentonite and phosphate fertilizer; and

in some embodiments, the material of the fourth layer further comprises a rooting powder.

In some embodiments, the materials and amounts of the nitrogen fertilizer, the bentonite, the potash fertilizer, the phosphate fertilizer, the binder, the magnesium ammonium phosphate, the super absorbent resin and the rooting powder are respectively the materials and amounts defined in the controlled release fertilizer of aspect I of the present invention.

The preparation method of the controlled-release fertilizer in aspect I or aspect II of the invention is characterized in that: the method comprises the following steps:

the preparation method of the fertilizer core comprises the following steps: performing first coating treatment on a nitrogen fertilizer by using the bentonite and the potash fertilizer to obtain first coating particles; secondly, carrying out secondary coating treatment on the first coated particles by using the bentonite and the phosphate fertilizer to obtain the fertilizer inner core;

fertilizer granule preparation: and coating the fertilizer kernel by using the four materials of the binder, the magnesium ammonium phosphate, the super absorbent resin and the rooting powder or the three materials of the binder, the magnesium ammonium phosphate and the super absorbent resin to obtain the slow/controlled release fertilizer particles.

In some embodiments, in the fertilizer core preparation step, the first coating treatment comprises: adding the nitrogen fertilizer into a disc granulator, and spraying atomized water to wet the surface of the nitrogen fertilizer; then adding powder formed by mixing the bentonite and the potash fertilizer; and then repeatedly spraying atomized water and adding powder formed by mixing the bentonite and the potash fertilizer until the potash fertilizer is used up to obtain the first coating particles.

In some embodiments, the total mass of the powder formed by mixing the bentonite and the potash fertilizer added each time is the same, and the mass ratio of the bentonite and the potash fertilizer added each time is the same.

In some embodiments, in the fertilizer core preparation step, the second coating treatment comprises: spraying atomized water to wet the surface of the first coated particle, and adding powder formed by mixing bentonite and phosphate fertilizer; and then repeatedly spraying atomized water and adding powder formed by mixing bentonite and a phosphate fertilizer until the phosphate fertilizer is used up, and drying to obtain the fertilizer kernel.

In some embodiments, the total mass of the powder formed by mixing bentonite and phosphate fertilizer is the same for each addition, and the mass ratio of bentonite to phosphate fertilizer is the same for each addition.

In some embodiments, in the fertilizer granule preparation step, the coating treatment comprises: adding the fertilizer core into a disc granulator, spraying the binder to wet the surface of the fertilizer core, adding the three materials of magnesium ammonium phosphate powder, super absorbent resin and rooting powder or the two materials of magnesium ammonium phosphate powder and super absorbent resin, and coating; and then repeatedly spraying the binder, adding the magnesium ammonium phosphate powder, the super absorbent resin and the rooting powder or the magnesium ammonium phosphate powder and the super absorbent resin, coating, and drying to obtain the slow controlled release fertilizer particles.

In some embodiments, the total mass of the magnesium ammonium phosphate powder, the super absorbent resin and the rooting powder added each time is the same, the mass ratio of the magnesium ammonium phosphate powder, the super absorbent resin and the rooting powder added each time is the same, or: the total mass of the magnesium ammonium phosphate powder and the total mass of the super absorbent resin which are added each time are the same, and the mass ratio of the magnesium ammonium phosphate powder to the super absorbent resin which are added each time is also the same.

Compared with the prior art, the invention has the following advantages:

1. the slow and controlled release fertilizer can provide nutrients and moisture required by growth for plants, has the effect of promoting water and fertilizer mutually, and can maximize the effects of water and fertilizer. The main component of bentonite is phyllosilicate mineral montmorillonite (shown in figure 1), so that the bentonite has a lamellar structure, and the bentonite has strong dispersibility, absorbability and cation exchange property; the bentonite is used as a carrier of the fertilizer, and the magnesium ammonium phosphate and the super absorbent resin are used as auxiliary materials to achieve an internal and external dual-control type slow release effect, so that not only can the physical properties of the fertilizer be improved, but also the loss of nutrients of the fertilizer in soil can be reduced, the release of the nutrients in the fertilizer is controlled, the utilization rate of the fertilizer is improved, the use amount of the fertilizer is reduced, and the damage of excessive fertilization to soil and water is reduced; the fertilizer nutrients are released evenly and meet the requirements of plants, and the leaching loss of nutrients, microbial decomposition and soil fixation are reduced; the fertilizer has good water and fertilizer retention and provides a good growing environment for plants; promote the development of plant root system and enhance the stress resistance of plants.

2. The slow-release fertilizer has the advantages that as the bentonite in the raw materials has better slow-release performance on nitrogen, phosphorus and potassium, the release rate of nitrogen is fastest, the release rate of potassium is second, and phosphorus is slowest; therefore, when the fertilizer core is prepared, the nitrogenous fertilizer, the potash fertilizer and the phosphate fertilizer are wrapped in layers from inside to outside, so that the nutrient supply of the fertilizer is better balanced.

3. The dissolving process of magnesium ammonium phosphate adopted by the slow and controlled release fertilizer is matched with each growth stage of plants, the nutrient release of the fertilizer meets the requirements of the plants, and the leaching loss of nutrients, microbial decomposition and soil fixation are reduced.

4. The super absorbent resin adopted by the slow and controlled release fertilizer can effectively improve the water absorption and water retention of the fertilizer, improve the water retention of soil, improve the soil structure and reduce the irrigation frequency, and is suitable for wide arid and semi-arid areas in China.

5. The rooting powder adopted by the slow controlled release fertilizer can promote the plants to rapidly root, so that the main roots are thick and strong, the fibrous roots are increased, and various elements such as solidified phosphorus, potassium and the like in the soil can be dissolved for the plants to absorb and utilize.

6. The slow controlled release fertilizer adopts bentonite as a fertilizer carrier, and has wide sources and low price; magnesium ammonium phosphate is used as a coating material, so that the recovery of elements such as nitrogen, phosphorus, magnesium and the like is promoted, and the waste is changed into valuable.

7. The high molecular material polyvinyl alcohol and the super absorbent resin adopted by the slow controlled release fertilizer are nontoxic, have good biodegradability and can not cause secondary environmental pollution.

8. The slow controlled release fertilizer has the advantages of proper material selection, proportioning composition, preparation method steps and parameter selection, and better supplement and synergistic effects among the materials, thereby jointly enhancing the technical effect.

9. The sustained and controlled release fertilizer has simple preparation process and low production cost, and is convenient for large-scale popularization and use.

Drawings

FIG. 1 is a schematic diagram of the crystal structure of montmorillonite in bentonite.

Detailed Description

In a first aspect, the present invention provides a controlled release fertilizer comprising: an inner core of the fertilizer, a binder and an outer coating; wherein, the inner core comprises fertilizer and bentonite, the binder comprises polyvinyl alcohol solution, and the outer coating comprises magnesium ammonium phosphate, super absorbent resin and rooting powder.

50-85 of chemical fertilizer, 5-10 of bentonite,

10-15 parts of a binder, wherein,

15 ~ 25 of magnesium ammonium phosphate, 10 ~ 20 of super absorbent resin, preferably still include: 1-3 parts of rooting powder;

the fertilizer comprises a nitrogenous fertilizer, a potash fertilizer and a phosphate fertilizer, and the mass ratio of the nitrogenous fertilizer to the potash fertilizer to the phosphate fertilizer is as follows: (25-38): (12-20): (15-24).

The dosage of the binder is determined according to the dosages of the magnesium ammonium phosphate, the super absorbent resin and the rooting powder, and the coating effect is directly influenced when too much or too little; the slow release time and effect of the fertilizer are influenced by the dosage of magnesium ammonium phosphate, the slow release effect cannot be realized when the dosage is too small, and the release speed of the fertilizer is too slow due to too much dosage, so that the plant growth requirement cannot be met.

The particle size of the nitrogen fertilizer is 1.5-2 mm, the particle size of the potassium fertilizer is 0.1-0.5 mm, the particle size of the phosphate fertilizer is 0.1-0.5 mm, and the particle size of the bentonite is 0.1-0.5 mm. The nitrogenous fertilizer is used as a fertilizer inner core, and the grain size is relatively large for better adsorption of an outer layer wrapping material; the grain diameters of the potash fertilizer, the phosphate fertilizer and the bentonite are small enough to be combined more tightly, so that the slow release effect of the bentonite is fully exerted, and the slow release effect is improved.

The nitrogen fertilizer is selected from one or more of urea, ammonium sulfate and ammonium nitrate, the potassium fertilizer is selected from one or two of potassium chloride and potassium sulfate, and the phosphate fertilizer is selected from one or two of calcium superphosphate and calcium magnesium phosphate.

The demand of plants on three elements of nitrogen, phosphorus and potassium is the most. The nitrogen fertilizer can increase chlorophyll and strengthen the vegetative growth of plants, the plants are thin and small due to lack of the nitrogen fertilizer, the leaves are yellow green and slow in growth and cannot bloom, too much nitrogen fertilizer can cause the plant tissues to be soft and the stems and leaves to grow excessively, the plants are easy to be invaded by diseases and pests, and the cold resistance is reduced; the phosphate fertilizer can promote flower bud formation and fruit precocity, can enable plants to grow well and grow more new roots, improves cold resistance and drought resistance, is insufficient in phosphate fertilizer, slow in plant growth, small in leaves, branches or tillers, small in flowers and fruits, late in maturity, too much phosphate fertilizer can cause plant precocity, small in seeds and low in yield; the potash fertilizer can improve the plant ability of resisting disease, insect, cold, drought and lodging, promote the root to develop, the bulb to increase, and can promote the fruit to enlarge, the lack of potassium can cause the plant leaf margin to appear the necrotic spot, then the scorched necrosis takes place, the potash fertilizer excess can cause the plant to dwarfed, the leaf color turns yellow, even withers.

The bentonite is selected from one or two of sodium bentonite and calcium bentonite. The main component of bentonite is the phyllosilicate mineral montmorillonite. Montmorillonite is widely used as a slow-controlled release fertilizer carrier due to the special 2:1 layered nano structure and unique water absorption expansion, dispersion, suspension, ion exchange, adsorption and other properties. China has abundant bentonite resources, the total reserve is 2 nd in the world, and the bentonite is distributed in more than 80 counties (cities) of 26 provinces (autonomous regions) in China, and is cheap and easy to obtain.

The binder is polyvinyl alcohol solution, preferably aqueous solution with mass percentage concentration of 5-8%. Polyvinyl alcohol is a water-soluble high molecular polymer with strong hydrophilicity, no toxicity and no irritation, and the formed hydrogel has certain viscosity, high water content, good strength, low toxicity, easy processing and the like, belongs to a biodegradable high molecular material, has good biocompatibility with rhizosphere microorganisms, can be produced in a large scale by a non-petroleum route, and has low price.

The particle size of the magnesium ammonium phosphate is 0.1-0.5 mm, the particle size is small enough to better play a slow release role, and if the particle size is too large, the effect similar to the shortage of the magnesium ammonium phosphate is caused. The magnesium ammonium phosphate recovered from wastewater containing phosphorus, nitrogen, magnesium and the like is a good slow-release fertilizer, is insoluble in water, cannot burn roots, and reduces the loss of the fertilizer along with water. Magnesium ammonium phosphate can be slowly dissolved by organic acid (citric acid, lycium acid, oxalic acid, etc.) secreted by plant root system. When the plant is in vegetative and reproductive growth periods, the root system secretes a large amount of organic acid, and the other periods secrete less organic acid. When plants need a large amount of fertilizer, the two stages of vegetative growth and reproductive growth are mainly carried out. The dosage of magnesium ammonium phosphate influences the slow release time and effect of the fertilizer: the excessive use amount can cause the fertilizer release speed to be too slow, the plant growth requirement cannot be met, the plant growth is inhibited, and certain negative effects are generated on the root system and the yield of the plant; the slow-release effect cannot be achieved due to too small dosage, the crop root system is damaged due to too high local fertilizer concentration in the early stage of fertilization, and the plant growth and yield are influenced due to insufficient fertilizer supply in the later stage.

The super absorbent resin is selected from: one or more of sodium polyacrylate, sodium polyacrylate grafted starch, sodium polyacrylate grafted sodium alginate and polyacrylamide. The super absorbent resin is a novel functional polymer material, has a low crosslinking degree network structure, has a large amount of hydrophilic groups such as carboxyl, hydroxyl and the like, can absorb and keep water which is hundreds of times or even thousands of times of the self weight, can repeatedly absorb and discharge water, and has the effects of regulating water, saving water, reasonably using water, slowly releasing nutrients and improving the soil structure.

The slow and controlled release fertilizer comprises the following raw materials in parts by mass: 1-3 parts of rooting powder. The rooting powder is selected from: one or more of ABT 1-No. 10 rooting powder. The rooting powder can promote the plants to rapidly root, so that the main roots are thick and strong, the fibrous roots are increased, and various elements such as solidified phosphorus, potassium and the like in soil can be dissolved for the plants to absorb and utilize.

The types and the dosage proportion of the raw materials of the slow controlled release fertilizer are properly selected, and the slow controlled release fertilizer has better supplement effect and synergistic effect: the bentonite with special lamellar structure and strong dispersibility, adsorbability and cation exchange property is used as a carrier of the fertilizer, and magnesium ammonium phosphate and super absorbent resin are used as auxiliary materials to achieve an internal and external dual-control type slow release effect, so that not only can the physical properties of the fertilizer be improved, but also the loss of nutrients in the fertilizer in soil can be reduced, the release of the nutrients in the fertilizer is controlled, and the utilization rate of the fertilizer is improved. The bentonite, the polyvinyl alcohol and the super absorbent resin have good water absorption and retention properties. The super absorbent resin and the rooting powder can improve the stress resistance of plants and promote the growth of plant roots.

In a second aspect, the present invention provides a slow/controlled release fertilizer, which comprises the following components in sequence from inside to outside: the inner core, the second layer, the third layer and the fourth layer;

the inner core is made of nitrogen fertilizer, the second layer is made of bentonite and potash fertilizer, and the third layer is made of bentonite and phosphate fertilizer; and the material of the fourth layer comprises a binder, magnesium ammonium phosphate and a super absorbent resin, and the fourth layer preferably comprises rooting powder. The hierarchy is so arranged that: the release rate of nitrogen is fastest, potassium is second, and phosphorus is slowest. If the hierarchical structure is changed, for example, the packaging is carried out in the sequence of phosphorus, nitrogen and potassium from inside to outside, the fertilizer efficiency release of potassium fertilizer and nitrogen fertilizer is too fast, and the fertilizer efficiency release of phosphate fertilizer is too slow, so that the fertilizer nutrient supply is unbalanced; excessive potash fertilizer in the early stage can cause poor plant growth, and insufficient phosphate fertilizer can cause slow plant growth, small leaves, branches or tillering reduction, small flowers and fruits and reduced yield.

Wherein, the specific materials and the dosages of the nitrogenous fertilizer, the bentonite, the potash fertilizer, the phosphate fertilizer, the adhesive, the magnesium ammonium phosphate, the super absorbent resin and the rooting powder are respectively as described in the first aspect.

In a third aspect, the present invention provides a method for preparing the controlled release fertilizer of the first aspect or/and the second aspect, comprising:

step one, preparing a fertilizer kernel: carrying out first coating treatment on a nitrogen fertilizer by using the bentonite and the potash fertilizer to obtain first coating particles; and then the bentonite and the phosphate fertilizer are used for carrying out second coating treatment on the first core particles to obtain the fertilizer core.

The first packet is processed including: adding the nitrogen fertilizer into a disc granulator, and spraying atomized water to wet the surface of the nitrogen fertilizer; adding the powder formed by mixing the bentonite and the potash fertilizer; and repeating the operation of spraying atomized water and adding the powder formed by mixing the bentonite and the potash fertilizer for 2-5 times, until the mixed powder of the potash fertilizer and the bentonite is used up and completely coated, thereby obtaining the first coated particle.

Preferably, the amount of the mixed powder of bentonite and potash fertilizer added each time is the same, and the mass ratio of bentonite to potash fertilizer in the mixed powder added each time is the same, so that the fertilizer effect is more uniformly released, and the operation is convenient.

The second packet processing includes: spraying atomized water to wet the surface of the first coated particle, and adding powder formed by mixing the bentonite and the phosphate fertilizer; and then repeating the operation of spraying atomized water and adding the powder formed by mixing the bentonite and the phosphate fertilizer for 2-5 times totally until the mixed powder of the bentonite and the phosphate fertilizer is used up and completely wrapped, taking out the obtained granules from a disc granulator, and drying at 60-80 ℃ to obtain the fertilizer core.

Preferably, the amount of the mixed powder of bentonite and phosphate fertilizer added each time is the same, and the mass ratio of bentonite to phosphate fertilizer in the mixed powder added each time is the same, so that the fertilizer effect is more uniformly released, and the operation is convenient.

Because the bentonite has better slow release performance on nitrogen, phosphorus and potassium, the release rate of nitrogen is fastest, potassium is second and phosphorus is slowest, therefore, when preparing the fertilizer core, the nitrogen fertilizer, the potassium fertilizer and the phosphate fertilizer are wrapped in layers from inside to outside, and the nutrient supply of the fertilizer is better and balanced.

Step two, fertilizer granule preparation: and coating the dried fertilizer kernel with the binder, magnesium ammonium phosphate, super absorbent resin or rooting powder to obtain the slow controlled release fertilizer granules.

The coating treatment comprises the following steps: adding the dried fertilizer kernel into a disc granulator, spraying the polymeric binder, adding the magnesium ammonium phosphate and the super absorbent resin or further comprising rooting powder, and coating; and then repeating the operation of spraying the polyvinyl alcohol solution, adding the magnesium ammonium phosphate powder, the high water absorption resin or the rooting powder and coating for 4-6 times, and then naturally drying the obtained granules or drying the granules at 20-40 ℃ (magnesium ammonium phosphate can be decomposed at the temperature higher than 60 ℃ and can affect the component content and the structure of the slow release fertilizer, so the drying temperature at the position cannot be too high), wherein the particle size after drying is 3.5-5 mm, and the slow release fertilizer granules are obtained.

Preferably, the total mass of the binder, magnesium ammonium phosphate, super absorbent resin or the rooting powder is the same, and the mass ratio of the binder, the magnesium ammonium phosphate, the super absorbent resin or the rooting powder is the same.

In each coating/enveloping treatment, the total mass of the added mixed powder and the mass ratio of each raw material are proper, the adding amount in each time is not excessive, and the mixed powder is preferably just coated by one layer, and the adding amount in each time is determined according to the mass parts of the raw materials.

The following detailed description is provided for the purpose of illustrating the invention and the accompanying advantages, and is not intended to limit the scope of the invention.

Example 1

urea 32, potassium chloride 16, calcium superphosphate 20, sodium bentonite 8,

a 7% polyvinyl alcohol aqueous solution 13,

magnesium ammonium phosphate 20, sodium polyacrylate 15, ABT3 rooting powder 2;

material sources are as follows: the sodium bentonite is provided by Shandong Yousio chemical engineering Co., Ltd, and has a product number I9310211; the polyvinyl alcohol aqueous solution is provided by Tata chemical Co., Ltd, No. 1788; sodium polyacrylate is supplied by Qingdao first family New Material Co., Ltd, cat # 1023; the ABT3 rooting powder is provided by Beijing Zhongling good Cheng technology Co.

Wherein the particle size of urea is 1.8mm, the particle size of potassium chloride is 0.3mm, the particle size of calcium superphosphate is 0.3mm, the particle size of sodium bentonite is 0.3mm, and the particle size of magnesium ammonium phosphate is 0.3 mm.

The preparation method of the controlled release fertilizer comprises the following steps:

(1) preparing a fertilizer core:

1) adding urea particles into a disc granulator, and spraying atomized water to wet the surfaces of the urea particles.

2) Rotating the disc, and adding the materials in a mass ratio of 1: 4, repeating the operation of spraying atomized water and adding the mixture of the sodium bentonite and the potassium chloride for 4 times, wherein the total mass of the mixture of the sodium bentonite and the potassium chloride added each time is the same, the mass ratio of the sodium bentonite to the potassium chloride in the mixture added each time is also the same, and obtaining the first coated particle after the potassium chloride is used up.

3) Spraying atomized water to wet the surface of the first coated particle, and adding a mixture of the atomized water and the water in a mass ratio of 1: 5, repeating the operation of spraying atomized water, adding sodium bentonite and calcium superphosphate and mixing for 4 times, wherein the total mass of the sodium bentonite and the calcium superphosphate added each time is the same, the mass ratio of the sodium bentonite to the calcium superphosphate added each time is also the same, rotating the disc until the coating is complete, taking out the prepared particles, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder, sodium polyacrylate and ABT No. 3 rooting powder with the particle size of 0.3mm, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, sodium polyacrylate and ABT No. 3 rooting powder and continuously coating for 5 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate and the ABT No. 3 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate and the ABT No. 3 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain the coated particles.

2) And drying the coated particles at 30 ℃ to obtain the slow/controlled release fertilizer particles, wherein the average particle size of the particles is 4 mm.

Detection example 1

Test 1:

3g of the dried controlled-release fertilizer prepared in example 1, 5 parts in total, were accurately weighed, and each was placed in a non-woven fabric bag, buried about 5cm below the surface layer of 3kg of the air-dried soil collected in the same batch, and left at room temperature with the soil humidity kept at 60%. Taking out a non-woven cloth bag after 1, 7, 14, 21 and 28 days respectively, airing, taking out fertilizer particles in the cloth bag, measuring the content of potassium by an ICP emission spectrometer, and measuring the content of nitrogen and phosphorus by an ultraviolet visible spectrophotometer.

In parallel, the release rates of the three elements in the soil were measured by the same test method using fertilizers with the same nutrient content (the content of nitrogen, phosphorus and potassium is the same as that of example 1) as a control group, and the results are shown in table 1.

The control group comprises the following raw materials in parts by mass: urea 32, potassium chloride 16, and calcium superphosphate 20.

Table 1: the release rate of nitrogen, phosphorus and potassium in the slow and controlled release fertilizer is percent

As can be seen from Table 1, the release rate of the controlled release fertilizer prepared in example 1 is significantly reduced compared to the release rates of nitrogen, phosphorus and potassium in the control fertilizer. The release rates of nitrogen, phosphorus and potassium were 10.3%, 43.8% and 68.6%, respectively, 4.2%, 18.6% and 27.7%, respectively, and 9.5%, 30.4% and 44.8%, respectively, at 1, 14 and 28 days after application to the soil. Therefore, the slow-release fertilizer has better slow release property, can improve the utilization efficiency of plant nutrients and reduce the loss of the nutrients.

And (3) testing 2:

in order to examine the effect of the fertilizer, tomatoes were planted in inner Mongolia test plots, the dried controlled release fertilizer of example 1 and the control fertilizer of test example 1 were used, the same plots were used, the varieties of tomatoes were the same, the field management was the same, 10 plants were dug out after 20 days of seedling growth and the results were compared, as shown in Table 2 (the values are average values).

Table 2: contrast of root growth of seedling

As can be seen from Table 2, compared with the control group fertilizer, the slow/controlled release fertilizer has an obvious effect of promoting the growth of plant roots, so that the number of root hairs is increased, and the length of the roots is increased. The tomato yield per mu of the experimental group is 4040 kg/mu and the tomato yield per mu of the control group is 3400 kg/mu after the seeds are sowed for 120 days, so that the tomato yield per mu of the experimental group is improved by 18.8 percent compared with the tomato yield per mu of the control group.

Example 2

The difference from example 1 is that: the rooting powder is not used, and the selection and the dosage of other raw materials, the preparation steps, the operation and the parameters are the same.

The same method as that of test example 1 was used to determine the release rate of the three elements in the soil, and the results were comparable to example 1, and the root system and yield of the tomatoes were reduced compared with example 1.

Example 3

urea 27, potassium chloride 18, calcium superphosphate 17, sodium bentonite 6,

a 6% polyvinyl alcohol aqueous solution 14,

magnesium ammonium phosphate 22, sodium polyacrylate 17, ABT4 # rooting powder 1.5;

the material source was the same as in example 1.

Wherein the particle size of urea is 2mm, the particle size of potassium chloride is 0.4mm, the particle size of calcium superphosphate is 0.4mm, the particle size of sodium bentonite is 0.4mm, and the particle size of magnesium ammonium phosphate is 0.4 mm.

(1) preparing a fertilizer core:

1) the same operation as in the example.

2) Rotating the disc, and adding the materials in a mass ratio of 3: 18, repeating the operation of spraying atomized water and adding a mixture of sodium bentonite and potassium chloride for 4 times, wherein the total mass of the mixture of sodium bentonite and potassium chloride added each time is the same, the mass ratio of sodium bentonite to potassium chloride in the mixture added each time is also the same, and obtaining the first coated particle after the potassium chloride is used up.

3) Spraying atomized water to wet the surface of the first coated particle, and adding a mixture of the atomized water and the water in a mass ratio of 3: 17, repeating the operation of spraying atomized water, adding sodium bentonite and calcium superphosphate and mixing for 4 times, wherein the total mass of the sodium bentonite and the calcium superphosphate added each time is the same, the mass ratio of the sodium bentonite to the calcium superphosphate added each time is also the same, rotating the disc until the coating is complete, taking out the prepared particles, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder, sodium polyacrylate and ABT No. 4 rooting powder with the particle size of 0.4mm, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, sodium polyacrylate and ABT No. 4 rooting powder and continuously coating for 5 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate and the ABT No. 4 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate and the ABT No. 4 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain the coated particles.

2) And drying the coated particles at 40 ℃ to obtain the slow/controlled release fertilizer particles, wherein the average particle size of the particles is 4 mm.

The same method as in test example 1 was used to measure the release rates of the three elements in the soil, and the effect equivalent to that of example 1 was obtained for all of them, and the effect equivalent to that of example 1 was also obtained for the root system and yield per mu of tomato.

Example 4

ammonium sulfate 36, potassium sulfate 15, calcium superphosphate 23, sodium bentonite 9,

a polyvinyl alcohol aqueous solution 15 with the mass percentage concentration of 8 percent,

magnesium ammonium phosphate 18, polyacrylamide 19, ABT5 rooting powder 3;

the polyacrylamide was obtained from Shandong Youx chemical technology, Inc., cat 2130111, and other sources were found in example 1.

Wherein the particle size of ammonium sulfate is 1.6mm, the particle size of potassium sulfate is 0.2mm, the particle size of calcium superphosphate is 0.2mm, the particle size of sodium bentonite is 0.2mm, and the particle size of magnesium ammonium phosphate is 0.2 mm.

(1) preparing a fertilizer core:

1) ammonium sulfate granules are added into a disc granulator, and atomized water is sprayed to wet the surface of the disc granulator.

2) Rotating the disc, and adding the materials in a mass ratio of 3: 10, repeating the operation of spraying atomized water and adding a mixture of sodium bentonite and potassium sulfate for 3 times, wherein the total mass of the mixture of sodium bentonite and potassium sulfate added each time is the same, the mass ratio of sodium bentonite to potassium sulfate in the mixture added each time is also the same, and obtaining the first coating particles after the potassium sulfate ingredients are used up.

3) Spraying atomized water to wet the surface of the first coated particle, and then adding a mixture of the atomized water and the water in a mass ratio of 9: 46, repeating the operation of spraying atomized water, adding sodium bentonite and calcium superphosphate and mixing for 4 times, wherein the total mass of the sodium bentonite and the calcium superphosphate added each time is the same, the mass ratio of the sodium bentonite to the calcium superphosphate added each time is also the same, rotating the disc until the coating is complete, taking out the prepared granules, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder, polyacrylamide and ABT5 rooting powder, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, polyacrylamide and ABT5 rooting powder and continuously coating for 4 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the polyacrylamide and the ABT5 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the polyacrylamide and the ABT5 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain coated particles.

Example 5

38 parts of ammonium nitrate, 20 parts of potassium sulfate, 24 parts of calcium magnesium phosphate fertilizer, 10 parts of sodium bentonite,

magnesium ammonium phosphate 24, polyacrylamide 18, ABT9 # rooting powder 2.5;

Wherein the grain size of ammonium nitrate is 1.7mm, the grain size of potassium sulfate is 0.1mm, the grain size of calcium magnesium phosphate fertilizer is 0.1mm, the grain size of sodium bentonite is 0.1mm, and the grain size of magnesium ammonium phosphate is 0.1 mm.

(1) preparing a fertilizer core:

1) ammonium nitrate granules are added into a disk granulator, and atomized water is sprayed to wet the surface of the disk granulator.

2) Rotating the disc, and adding the materials in a mass ratio of 5: 20, repeating the operation of spraying atomized water and adding the mixture of the sodium bentonite and the potassium sulfate for 4 times, wherein the total mass of the mixture of the sodium bentonite and the potassium sulfate added each time is the same, the mass ratio of the sodium bentonite to the potassium sulfate in the mixture added each time is also the same, and obtaining the first coating particles after the potassium sulfate ingredients are used up.

3) Spraying atomized water to wet the surface of the first coated particle, and adding a mixture of the atomized water and the water in a mass ratio of 5: 24, repeating the operation of spraying atomized water and adding sodium bentonite and calcium magnesium phosphate fertilizer to mix for 4 times, wherein the total mass of the sodium bentonite and the calcium magnesium phosphate fertilizer added each time is the same, the mass ratio of the sodium bentonite to the calcium magnesium phosphate fertilizer in the mixture added each time is also the same, rotating the disc until the coating is complete, taking out the prepared granules, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder, polyacrylamide and ABT9 rooting powder, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, polyacrylamide and ABT9 rooting powder and continuously coating for 3 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the polyacrylamide and the ABT9 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the polyacrylamide and the ABT9 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain coated particles.

Example 6

35 parts of ammonium nitrate, 14 parts of potassium chloride, 16 parts of calcium magnesium phosphate fertilizer, 7 parts of sodium bentonite,

a 7% polyvinyl alcohol aqueous solution 12,

magnesium ammonium phosphate 16, sodium polyacrylate 11, ABT8 rooting powder 2;

see example 1 for sources of the above starting materials.

Wherein the grain size of ammonium nitrate is 1.9mm, the grain size of potassium sulfate is 0.5mm, the grain size of calcium magnesium phosphate fertilizer is 0.5mm, the grain size of sodium bentonite is 0.5mm, and the grain size of magnesium ammonium phosphate is 0.5 mm.

(1) preparing a fertilizer core:

2) Rotating the disc, and adding the materials according to the mass ratio of 7: 28, repeating the operation of spraying atomized water and adding a mixture of sodium bentonite and potassium chloride for 4 times, wherein the total mass of the mixture of sodium bentonite and potassium chloride added each time is the same, the mass ratio of sodium bentonite to potassium chloride in the mixture added each time is also the same, and obtaining the first coated particle after the potassium chloride is used up.

3) Spraying atomized water to wet the surface of the first coated particle, and adding a mixture of the atomized water and the water in a mass ratio of 3.5: 16, repeating the operation of spraying atomized water and adding sodium bentonite and calcium magnesium phosphate fertilizer to mix for 4 times, wherein the total mass of the sodium bentonite and the calcium magnesium phosphate fertilizer added each time is the same, the mass ratio of the sodium bentonite to the calcium magnesium phosphate fertilizer in the mixture added each time is also the same, rotating the disc until the coating is complete, taking out the prepared granules, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder, sodium polyacrylate and ABT No. 8 rooting powder, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, sodium polyacrylate and ABT No. 8 rooting powder and continuously coating for 4 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate and the ABT No. 8 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate and the ABT No. 8 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain the coated granules.

Example 7

25 portions of urea, 12 portions of potassium chloride, 15 portions of calcium superphosphate, 5 portions of calcium bentonite,

a 7% polyvinyl alcohol aqueous solution 10,

magnesium ammonium phosphate 25, sodium polyacrylate grafted starch 15, ABT3 # rooting powder 2;

material sources are as follows: the calcium bentonite is provided by a Lingshou county Langtai mineral product processing factory, with a product number of 1001; the above mentioned sodium polyacrylate grafted starch is HMH, obtained from Beijing Lingbao scientific and technological Co., Ltd, and the sources of other raw materials are the same as those in example 1.

Wherein the particle size of urea is 1.8mm, the particle size of potassium chloride is 0.3mm, the particle size of calcium superphosphate is 0.3mm, the particle size of calcium bentonite is 0.3mm, and the particle size of magnesium ammonium phosphate is 0.3 mm.

(1) preparing a fertilizer core:

2) Rotating the disc, and adding the materials in a mass ratio of 5: 24, repeating the operation of spraying atomized water and adding the mixture of the calcium bentonite and the potassium chloride for 4 times, wherein the total mass of the mixture of the calcium bentonite and the potassium chloride added each time is the same, the mass ratio of the calcium bentonite to the potassium chloride in the mixture added each time is also the same, and obtaining the first coated particle after the potassium chloride is used up.

3) Spraying atomized water to wet the surface of the first coated particle, and adding a mixture of the atomized water and the water in a mass ratio of 1: 6, repeating the operation of spraying atomized water, adding calcium bentonite and calcium superphosphate and mixing for 4 times, wherein the total mass of the calcium bentonite and the calcium superphosphate added each time is the same, the mass ratio of the calcium bentonite to the calcium superphosphate in the mixture added each time is also the same, rotating the disc until the coating is complete, taking out the prepared particles, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder with the particle size of 0.3mm, sodium polyacrylate grafted starch and ABT No. 3 rooting powder, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, sodium polyacrylate grafted starch and ABT No. 3 rooting powder and continuously coating for 5 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate grafted starch and the ABT No. 3 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate grafted starch and the ABT No. 3 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain the coated particles.

Example 8

urea 32, potassium chloride 16, calcium superphosphate 20, calcium bentonite 8,

a 7% polyvinyl alcohol aqueous solution 13,

magnesium ammonium phosphate 20, sodium polyacrylate grafted sodium alginate 15, ABT3 # rooting powder 2;

material sources are as follows: the calcium bentonite is provided by a Lingshou county Langtai mineral product processing factory, with a product number of 1001; the sodium polyacrylate grafted sodium alginate is prepared by the method of Chinese patent application (application number 201510035395.3) 'sodium polyacrylate grafted sodium alginate embedded probiotic microcapsule and preparation method thereof'; the other raw materials were derived from the same sources as in example 1.

(1) preparing a fertilizer core:

2) Rotating the disc, and adding the materials in a mass ratio of 1: 4, repeating the operation of spraying atomized water and adding the mixture of the calcium bentonite and the potassium chloride for 4 times, wherein the total mass of the mixture of the calcium bentonite and the potassium chloride added each time is the same, the mass ratio of the calcium bentonite to the potassium chloride in the mixture added each time is also the same, and obtaining the first coated particle after the potassium chloride is used up.

3) Spraying atomized water to wet the surface of the first coated particle, and adding a mixture of the atomized water and the water in a mass ratio of 1: 5, repeating the operation of spraying atomized water, adding calcium bentonite and calcium superphosphate and mixing for 4 times, wherein the total mass of the calcium bentonite and the calcium superphosphate added each time is the same, the mass ratio of the calcium bentonite to the calcium superphosphate in the mixture added each time is also the same, rotating the disc until the coating is complete, taking out the prepared particles, and drying at 70 ℃ to obtain the fertilizer core.

(2) Preparing slow/controlled release fertilizer particles:

1) putting the fertilizer kernel particles into a disc granulator, rotating the disc, spraying a polyvinyl alcohol aqueous solution, and wetting the surface of the fertilizer kernel preferably to completely wet the surface of the fertilizer kernel without dripping water; adding magnesium ammonium phosphate powder with the particle size of 0.3mm, sodium polyacrylate grafted starch and ABT No. 3 rooting powder, coating, repeating the operation of spraying polyvinyl alcohol solution, adding magnesium ammonium phosphate powder, sodium polyacrylate grafted sodium alginate and ABT No. 3 rooting powder and continuously coating for 5 times, wherein the total mass of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate grafted sodium alginate and the ABT No. 3 rooting powder added each time is the same, the mass ratio of the polyvinyl alcohol aqueous solution, the magnesium ammonium phosphate powder, the sodium polyacrylate grafted sodium alginate and the ABT No. 3 rooting powder added each time is also the same, and rotating the disc until the coating is complete to obtain the coated particles.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. A slow and controlled release fertilizer is characterized in that:

50-85 parts of chemical fertilizer, 5-10 parts of bentonite, 10-15 parts of binder, 15-25 parts of magnesium ammonium phosphate and 10-20 parts of super absorbent resin;

the fertilizer comprises: nitrogenous fertilizer, potash fertilizer, phosphate fertilizer;

preferably, the mass ratio of the nitrogenous fertilizer to the potash fertilizer to the phosphate fertilizer is (25-38): (12-20): (15-24).

2. The slow/controlled release fertilizer of claim 1, characterized in that:

the particle size of the nitrogen fertilizer is 1.5-2 mm, the particle size of the potassium fertilizer is 0.1-0.5 mm, and the particle size of the phosphate fertilizer is 0.1-0.5 mm;

preferably, the nitrogen fertilizer is selected from one or more of urea, ammonium sulfate and ammonium nitrate, the potassium fertilizer is selected from one or two of potassium chloride and potassium sulfate, and the phosphate fertilizer is selected from one or two of calcium superphosphate and calcium magnesium phosphate.

3. The slow/controlled release fertilizer of claim 1, characterized in that:

the bentonite is selected from one or two of sodium bentonite and calcium bentonite; preferably, the binder is a polyvinyl alcohol solution;

preferably, the polyvinyl alcohol solution is an aqueous solution with the mass percentage concentration of 5-8%;

preferably, the particle size of the magnesium ammonium phosphate is 0.1-0.5 mm;

preferably, the super absorbent resin is selected from: one or more of sodium polyacrylate, sodium polyacrylate grafted starch, sodium polyacrylate grafted sodium alginate and polyacrylamide;

preferably, the slow/controlled release fertilizer comprises the following raw materials in parts by mass: 1-3 parts of rooting powder;

more preferably, the rooting powder is selected from: one or more of ABT1, ABT2, ABT3, ABT4, ABT5, ABT6, ABT7, ABT8, ABT9 and ABT10 rooting powder.

4. The controlled release fertilizer of any one of claims 1-3, wherein:

the structure of the slow and controlled release fertilizer sequentially comprises from inside to outside: the core, wrap up the second layer outside the said core, wrap up the third layer outside the said second layer and wrap up the fourth layer outside the said third layer;

the material of the inner core comprises nitrogen fertilizer;

the material of the second layer comprises bentonite and potash fertilizer;

the third layer is made of bentonite and phosphate fertilizer; and

5. A slow and controlled release fertilizer is structurally and sequentially composed of: the inner core, the second layer, the third layer and the fourth layer;

the material of the inner core comprises nitrogen fertilizer;

the material of the second layer comprises bentonite and potash fertilizer;

the third layer is made of bentonite and phosphate fertilizer; and

preferably, the material of the fourth layer further comprises rooting powder.

6. The controlled release fertilizer of claim 5, wherein:

the materials and the dosage of the nitrogen fertilizer, the bentonite, the potash fertilizer, the phosphate fertilizer, the binder, the magnesium ammonium phosphate, the super absorbent resin and the rooting powder are respectively the materials and the dosage defined by the slow controlled release fertilizer of any one of claims 1-3.

7. The method of preparing a controlled release fertilizer of any one of claims 1-6, characterized in that: the method comprises the following steps:

8. The method according to claim 7, wherein:

in the fertilizer core preparation step, the first coating treatment comprises: adding the nitrogen fertilizer into a disc granulator, and spraying atomized water to wet the surface of the nitrogen fertilizer; then adding powder formed by mixing the bentonite and the potash fertilizer; then repeatedly spraying atomized water and adding powder formed by mixing bentonite and a potash fertilizer until the potash fertilizer is used up to obtain the first coating particles;

preferably, the total mass of the powder formed by mixing the bentonite and the potash fertilizer added each time is the same, and the mass ratio of the bentonite and the potash fertilizer added each time is also the same.

9. The method according to claim 7, wherein:

in the fertilizer core preparation step, the second coating treatment comprises: spraying atomized water to wet the surface of the first coated particle, and adding powder formed by mixing bentonite and phosphate fertilizer; then repeatedly spraying atomized water and adding powder formed by mixing bentonite and a phosphate fertilizer until the phosphate fertilizer is used up, and drying to obtain the fertilizer kernel;

preferably, the total mass of the powder formed by mixing the bentonite and the phosphate fertilizer is the same in each adding, and the mass ratio of the bentonite to the phosphate fertilizer is the same in each adding.

10. The method according to claim 7, wherein:

in the fertilizer granule preparation step, the coating treatment comprises: adding the fertilizer core into a disc granulator, spraying the binder to wet the surface of the fertilizer core, adding the three materials of magnesium ammonium phosphate powder, super absorbent resin and rooting powder or the two materials of magnesium ammonium phosphate powder and super absorbent resin, and coating; then repeatedly spraying the binder, adding the three materials of magnesium ammonium phosphate powder, super absorbent resin and rooting powder or the two materials of magnesium ammonium phosphate powder and super absorbent resin, coating, and drying to obtain the slow controlled release fertilizer particles;

preferably, the total mass of the magnesium ammonium phosphate powder, the super absorbent resin and the rooting powder added each time is the same, and the mass ratio of the magnesium ammonium phosphate powder, the super absorbent resin and the rooting powder added each time is also the same, or: the total mass of the magnesium ammonium phosphate powder and the total mass of the super absorbent resin which are added each time are the same, and the mass ratio of the magnesium ammonium phosphate powder to the super absorbent resin which are added each time is also the same.