阅读说明：本技术 一种尿素包衣腐植酸复合颗粒肥及其制备方法 (Urea-coated humic acid composite granular fertilizer and preparation method thereof ) 是由 赵新巍 赵建亮 曹培顺 纪玲玲 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种尿素包衣腐植酸复合颗粒肥及其制备方法。本发明包括以下原料：尿素5-50份,腐植酸或其盐5-10份,其它氮肥5-20份,磷肥10-60份,钾肥20-50份,微量元素0.5-5份,复合粘结剂1-5份,复合粘结剂包括以下组分：羟甲基纤维素8-12份,黄原胶8-12份,木质素磺酸钠6-8份,十二烷基硫酸钠5-7份,十二烷基苯磺酸钠2-4份,去离子水60-65份。本发明的复合颗粒肥具有核壳结构,优先释放氮元素,随后氮磷钾依次释放,最终释放腐植酸钾和微量元素,满足了作物不同时期对营养元素的不同需求,防结块性能好,在植物生长过程中可以实现精准施肥,提高了肥料的利用率,达到了减肥增产的效果。(The invention discloses a urea-coated humic acid composite granular fertilizer and a preparation method thereof. The invention comprises the following raw materials: 5-50 parts of urea, 5-10 parts of humic acid or salt thereof, 5-20 parts of other nitrogenous fertilizers, 10-60 parts of phosphate fertilizers, 20-50 parts of potash fertilizers, 0.5-5 parts of trace elements and 1-5 parts of composite binders, wherein the composite binders comprise the following components: 8-12 parts of hydroxymethyl cellulose, 8-12 parts of xanthan gum, 6-8 parts of sodium lignosulfonate, 5-7 parts of sodium dodecyl sulfate, 2-4 parts of sodium dodecyl benzene sulfonate and 60-65 parts of deionized water. The composite granular fertilizer disclosed by the invention has a core-shell structure, preferentially releases nitrogen elements, then sequentially releases nitrogen, phosphorus and potassium, and finally releases potassium humate and trace elements, so that different requirements of crops on nutrient elements in different periods are met, the anti-caking performance is good, the accurate fertilization can be realized in the plant growth process, the utilization rate of the fertilizer is improved, and the effects of losing weight and increasing yield are achieved.)

1. The urea-coated humic acid composite granular fertilizer is characterized by comprising the following raw materials in parts by weight:

5-50 parts of urea, 5-10 parts of humic acid or salt thereof, 5-20 parts of other nitrogenous fertilizers, 10-60 parts of phosphate fertilizers, 20-50 parts of potash fertilizers, 0.5-5 parts of trace elements and 1-5 parts of composite binders;

the composite binder comprises the following components in parts by weight: 8-12 parts of hydroxymethyl cellulose, 8-12 parts of xanthan gum, 6-8 parts of sodium lignosulfonate, 5-7 parts of sodium dodecyl sulfate, 2-4 parts of sodium dodecyl benzene sulfonate and 60-65 parts of deionized water.

2. The urea-coated humic acid composite granular fertilizer according to claim 1, which is characterized in that:

the other nitrogen fertilizer is any one or more of potassium nitrate, ammonium sulfate, monoammonium phosphate and diammonium phosphate;

the phosphate fertilizer is one or more of monoammonium phosphate, monopotassium phosphate and diammonium phosphate;

the potash fertilizer is any one or more of potassium sulfate, potassium nitrate and potassium dihydrogen phosphate;

the trace elements are any one or more of zinc, iron, manganese, copper and boron.

3. The urea-coated humic acid composite granular fertilizer according to claim 1 or 2, which is characterized in that:

the trace elements are selected from one or more of sodium zinc ethylenediamine tetraacetate, sodium ferric ethylenediamine tetraacetate, sodium manganese ethylenediamine tetraacetate, sodium copper ethylenediamine tetraacetate and borax.

4. The preparation method of the urea-coated humic acid composite granular fertilizer according to any one of claims 1 to 3, characterized by comprising the following steps:

1) taking humic acid or salt thereof and trace elements, crushing, stirring, uniformly mixing, spraying a composite binder, granulating, drying and screening to obtain small particles with the particle size of 0.5-0.6 mm;

2) taking other nitrogenous fertilizer, phosphate fertilizer and potash fertilizer, crushing, stirring and uniformly mixing to obtain nitrogen-phosphorus-potassium mixed powder; continuously spraying a composite binder in the small granules obtained in the step 1), then adding mixed nitrogen-phosphorus-potassium powder to wrap the mixed nitrogen-phosphorus-potassium powder on the surfaces of the small granules, granulating, drying and screening to obtain medium granules with the grain size of 1.4-1.6 mm;

3) taking urea, and crushing to obtain urea powder; spraying the composite binder again in the medium granules obtained in the step 2), then adding urea powder to coat the urea powder on the surface of the medium granules, granulating, drying and screening to obtain large granules with the grain size of 1.9-2.2mm, namely the urea-coated humic acid composite granular fertilizer.

5. The preparation method of the urea-coated humic acid composite granular fertilizer according to claim 4, which is characterized in that:

in the step 1), the drying is carried out for 8-12min in hot air at 75-85 ℃.

6. The preparation method of the urea-coated humic acid composite granular fertilizer according to claim 4, which is characterized in that:

in the step 2), the drying is carried out for 8-12min in hot air at 45-55 ℃.

7. The preparation method of the urea-coated humic acid composite granular fertilizer according to claim 4, which is characterized in that:

in the step 3), the drying is carried out for 25-35min in hot air at 45-55 ℃.

8. The preparation method of the urea-coated humic acid composite granular fertilizer according to claim 4, which is characterized in that:

in the step 1), the particle size of the granules obtained by granulation is 0.5-0.8 mm.

9. The preparation method of the urea-coated humic acid composite granular fertilizer according to claim 4, which is characterized in that:

in the step 2), the particle size of the granules obtained by granulation is 1.5-1.8 mm.

10. The preparation method of the urea-coated humic acid composite granular fertilizer according to claim 4, which is characterized in that:

in the step 3), the particle size of the granules obtained by granulation is 1.9-2.4 mm.

Technical Field

The invention belongs to the technical field of fertilizers, and particularly relates to a urea-coated humic acid composite granular fertilizer and a preparation method thereof.

Background

Humic acid is a macromolecular organic substance widely existing in nature, is a green organic fertilizer, can degrade black liquid mulching films, resist drought, save water, improve saline-alkali soil, adsorb and degrade heavy metals in soil, and meanwhile, has excellent effects of improving desert, increasing nitrogen, dissolving phosphorus and promoting potassium, thereby greatly reducing the using amount of chemical fertilizers. In addition, the nitrogen, phosphorus, potassium and trace element compound fertilizer is a common inorganic compound fertilizer in the current market, and provides various large and medium trace elements required by plant growth. However, most of the inorganic compound fertilizers are powdery fertilizers, a large amount of dust is generated in the using process, the content is difficult to achieve uniformity, and the effect of accurate fertilization cannot be achieved.

The humic acid, the nitrogen, the phosphorus and the potassium and the trace element compound fertilizer are mixed for use, so that the absorption of the nitrogen, the phosphorus and the potassium by plants can be promoted, meanwhile, the soil is improved, the national soil control policy is met, and the purposes of green agriculture and coexistence of nutrition and health are realized. However, researches find that the problems of pseudo-hardening, fertilizer discoloration, humic acid effect reduction and the like exist in the process of mixing and using the humic acid, the nitrogen, the phosphorus and the potassium and the trace element compound fertilizer, so that the effect of mixing and using the two fertilizers is reduced.

Disclosure of Invention

The invention aims to provide a urea-coated humic acid composite granular fertilizer and a preparation method thereof, and aims to solve the problems of pseudo-hardening, fertilizer discoloration and humic acid effect reduction in the mixed use process of humic acid, nitrogen, phosphorus and potassium and trace element compound fertilizers in the prior art, so that the use effect is reduced.

In order to solve the technical problems, the invention is mainly realized by the following technical scheme:

in one aspect, the urea-coated humic acid composite granular fertilizer comprises the following raw materials in parts by weight: 5-50 parts of urea, 5-10 parts of humic acid or salt thereof, 5-20 parts of other nitrogenous fertilizers, 10-60 parts of phosphate fertilizers, 20-50 parts of potash fertilizers, 0.5-5 parts of trace elements and 1-5 parts of composite binders; the composite binder comprises the following components in parts by weight: 8-12 parts of hydroxymethyl cellulose, 8-12 parts of xanthan gum, 6-8 parts of sodium lignosulfonate, 5-7 parts of sodium dodecyl sulfate, 2-4 parts of sodium dodecyl benzene sulfonate and 60-65 parts of deionized water.

The invention relates to a water-soluble fertilizer of urea coated humic acid, urea is uniformly coated on the outer surface of humic acid through a compound binder, the phenomena of powder falling and dust raising of the humic acid in the granulating and using processes are prevented, the original molecular structure of the humic acid is fully protected, the biological activity of the humic acid is kept, meanwhile, the urea on the outer layer is easy to absorb water, the water solubility of the compound granular fertilizer is promoted, and even in a water-deficient environment, the water in the air can be absorbed through the characteristic of a low moisture absorption point of the urea, so that the dissolution and release of the compound granular fertilizer are accelerated; according to different requirements of crops on nutrient elements in different periods, the composite granular fertilizer with the core-shell structure preferentially releases nitrogen elements to promote the growth of the crops, then sequentially releases phosphorus, potassium, other nitrogen elements and trace elements to meet the nutritional requirements of the crops, and finally releases potassium humate to promote the absorption of the crops on the nitrogen, the phosphorus and the potassium and improve the soil environment; each nutrient element content is stable, the dust is few, the convenient to use is difficult for hardening, has fine prevention soil caking performance, and water-soluble effect is good, and application scope is wide, can broadcast application, drip irrigation or sprinkling irrigation, can realize accurate fertilization at the plant growth in-process, has improved the utilization ratio of fertilizer, has reached the effect of losing weight and increasing production.

As a preferred embodiment, the other nitrogen fertilizer is any one or more of potassium nitrate, ammonium sulfate, monoammonium phosphate and diammonium phosphate; the phosphate fertilizer is one or more of monoammonium phosphate, monopotassium phosphate and diammonium phosphate; the potash fertilizer is any one or more of potassium sulfate, potassium nitrate and potassium dihydrogen phosphate; the trace elements are any one or more of zinc, iron, manganese, copper and boron.

In the urea-coated humic acid composite granular fertilizer, humic acid is positioned on the innermost layer and is the core of the composite granular fertilizer, the outer layer of the humic acid is coated with phosphorus and potassium elements, the phosphorus, potassium and other nitrogen elements form the middle layer of the composite granular fertilizer, and urea is coated on the outer surfaces of the phosphorus, potassium and other nitrogen elements to form the shell of the composite granular fertilizer. The humic acid is easy to react with the urea to form a complex which hinders the water solubility of the humic acid, so that the phenomenon of blocking a drip irrigation nozzle and a sprayer nozzle can occur in the using process; in addition, the complex can also prolong the hydrolysis and enzymolysis processes of urea, and cannot realize the purpose of quickly supplementing nutrients; however, the composite granular fertilizer of the invention effectively blocks the contact of urea and potassium humate, prevents the formation of humic acid urea complex, has good water solubility, does not block a drip irrigation nozzle and a sprayer nozzle, and slowly releases various nutrient elements in a layered manner, thereby meeting different requirements of crops on the nutrient elements at different periods. Other nitrogen fertilizers of the present invention are nitrogen fertilizers other than urea.

In a preferred embodiment, the trace element is selected from any one or more of sodium zinc ethylenediaminetetraacetate, sodium iron ethylenediaminetetraacetate, sodium manganese ethylenediaminetetraacetate, sodium copper ethylenediaminetetraacetate and borax. The invention can be prepared into fertilizers with different nitrogen-phosphorus-potassium ratios according to actual needs, and the content of nitrogen, phosphorus and potassium in the fertilizer is adjusted to meet the requirements of crops on different elements in different growth periods. The trace elements of the invention adopt chelated trace elements, thus improving the use effect.

In another aspect, the preparation method of the urea-coated humic acid composite granular fertilizer comprises the following steps:

1) taking humic acid or salt thereof and trace elements, crushing, stirring, uniformly mixing, spraying a composite binder, granulating, drying and screening to obtain small particles with the particle size of 0.5-0.6 mm;

2) taking other nitrogenous fertilizer, phosphate fertilizer and potash fertilizer, crushing, stirring and uniformly mixing to obtain nitrogen-phosphorus-potassium mixed powder; continuously spraying a composite binder in the small granules obtained in the step 1), then adding mixed nitrogen-phosphorus-potassium powder to wrap the mixed nitrogen-phosphorus-potassium powder on the surfaces of the small granules, granulating, drying and screening to obtain medium granules with the grain size of 1.4-1.6 mm;

3) taking urea, and crushing to obtain urea powder; spraying the composite binder again in the medium granules obtained in the step 3), then adding urea powder to coat the urea powder on the surface of the medium granules, granulating, drying and screening to obtain large granules with the grain size of 1.9-2.2mm, namely the urea-coated humic acid composite granular fertilizer

In the preparation method of the urea-coated humic acid composite granular fertilizer, the potassium humate and the trace elements are mixed to form an inner core of the composite granular fertilizer; then, coating phosphorus-potassium and other nitrogen mixed powder on the outer surface of the composite granular fertilizer inner core, and forming an intermediate layer of the composite granular fertilizer; finally, coating urea powder on the outer surface of the intermediate layer of the composite granular fertilizer and forming a shell of the composite granular fertilizer; the preparation method can achieve the effect that the nutrient components are uniformly distributed in the range of 2mm in thickness, and realizes accurate fertilization in the plant growth process; the humic acid is positioned on the innermost layer, so that the original molecular structure of the humic acid is fully protected, and the biological activity of the humic acid is kept; meanwhile, the urea on the outer layer is easy to absorb water, so that the water solubility of the composite granular fertilizer is promoted, and even in a water-deficient environment, the water in the air is absorbed through the characteristic of low moisture absorption point of the urea, so that the dissolution and release of the fertilizer granules are accelerated; the obtained composite granular fertilizer prevents the contact of urea and potassium humate, thereby blocking the formation of humic acid urea, preferentially releasing nitrogen elements to promote plant growth in the use process, sequentially releasing phosphorus potassium, other nitrogen elements and trace elements to meet the nutritional requirements of crops, and finally releasing potassium humate to promote the absorption of the crops on nitrogen, phosphorus and potassium and improve the soil environment; the fertilizer has stable content of various nutrient elements, good performance of preventing soil from caking, good water-soluble effect and wide application range, can be applied in a broadcasting way, drop-irrigation or spray-irrigation way, improves the utilization rate of the fertilizer and achieves the effects of losing weight and increasing yield. The preparation method of the urea-coated humic acid composite granular fertilizer is simple, convenient to operate and easy to realize industrialization.

As a preferred embodiment, in the step 1), the drying is carried out in hot air at 75-85 ℃ for 8-12 min. Because humic acid is a macromolecular group with a long carbon chain, the invention adopts a low-temperature drying mode in the formation process of the inner core, avoids the breakage of carbon chains in the molecular structure of the humic acid caused by high temperature, and fully ensures the biological activity of the humic acid; meanwhile, the low-temperature drying mode has less energy loss and is green and environment-friendly.

As a preferred embodiment, in the step 2), the drying is carried out in hot air at 45-55 ℃ for 8-12 min. In the forming process of the intermediate layer of the compound granular fertilizer, a low-temperature drying mode is also adopted, so that the activity of humic acid is further protected, the phenomena of humic acid structural decomposition and fertilizer efficiency reduction are avoided, phosphorus, potassium and other nitrogen elements are fully ensured to be coated on the surface of the humic acid, and the thickness of the phosphorus, potassium and other nitrogen elements on the surface of the humic acid is controlled, so that accurate fertilization is realized.

As a preferred embodiment, in the step 3), the drying is carried out in hot air at 45-55 ℃ for 25-35 min. The invention also adopts a low-temperature drying mode in the forming process of the outer shell layer of the compound granular fertilizer, fully ensures that the urea is firmly wrapped on the outer surface of the middle layer, simultaneously does not influence the performance of the urea, effectively controls the thickness of the urea on the surface of the middle layer, and does not generate the phenomena of powder falling and dust raising.

As a preferred embodiment, in the step 1), the particle size of the granules obtained by granulation is 0.5 to 0.8 mm. According to the invention, the particle sizes of potassium humate and trace elements in the granulation process are controlled, so that the content of humic acid in the urea-coated humic acid composite granular fertilizer is effectively controlled, and accurate fertilization is realized; according to the invention, humic acid is used as an inner core, a three-layer core-shell structure is formed by a composite binder, the binding is firm, the coating temperature is low, and the nutrient components are not lost.

As a preferred embodiment, in the step 2), the particle size of the granules obtained by granulation is 1.5 to 1.8 mm. The invention also controls the particle size of phosphorus and potassium elements after coating humic acid, thereby effectively controlling the content of phosphorus and potassium elements in the urea-coated humic acid composite granular fertilizer to realize accurate fertilization; the phosphorus-potassium element as the intermediate layer effectively prevents the urea from directly contacting with the potassium humate, thereby preventing the formation of the urea humate.

As a preferred embodiment, in the step 3), the particle size of the granules obtained by granulation is 1.9-2.4 mm. The invention also controls the particle size of the urea after coating the humic acid, thereby effectively controlling the urea content in the urea-coated humic acid composite granular fertilizer to realize accurate fertilization; the urea is used as the outermost layer of the composite granular fertilizer, the hardness of the urea is high, the internal structure of the composite granular layer is fully protected, the phenomena of powder falling and dust raising in the transportation and use processes of the urea are avoided, and the loss and content unbalance of nutrient elements of the composite granular fertilizer are avoided.

Compared with the prior art, the invention has the beneficial effects that: the invention is a water-soluble fertilizer of urea coating humic acid, urea wraps up on the external surface of humic acid evenly through the compound binder, fully protect the original molecular structure of humic acid, has kept the biological activity of humic acid, meanwhile, the urea of the outer layer is apt to absorb water, has promoted the water-solubility of this compound granular fertilizer, even in the environment of water shortage, can absorb the moisture in the air through the characteristic of urea low moisture absorption point, thus accelerate the dissolution release of this compound granular fertilizer; according to different requirements of crops on nutrient elements in different periods, the composite granular fertilizer with the core-shell structure preferentially releases nitrogen elements to promote the growth of the crops, then sequentially releases phosphorus, potassium, other nitrogen elements and trace elements to meet the nutritional requirements of the crops, and finally releases potassium humate to promote the absorption of the crops on the nitrogen, the phosphorus and the potassium and improve the soil environment; the fertilizer has the advantages of stable content of various nutrient elements, less dust, convenient use, difficult hardening, good performance of preventing soil from caking, good water-soluble effect, wide application range, capability of being applied in a broadcasting way, drop irrigation or spray irrigation, capability of realizing accurate fertilization in the plant growth process, improved utilization rate of the fertilizer and achievement of the effects of losing weight and increasing yield; the preparation method is simple, convenient to operate and easy to realize industrialization.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention relates to a urea-coated humic acid composite granular fertilizer which comprises the following raw materials in parts by weight: 5-50 parts of urea, 5-10 parts of humic acid or salt thereof, 5-20 parts of other nitrogenous fertilizers, 10-60 parts of phosphate fertilizers, 20-50 parts of potash fertilizers, 0.5-5 parts of trace elements and 1-5 parts of composite binders; the composite binder comprises the following components in parts by weight: 8-12 parts of hydroxymethyl cellulose, 8-12 parts of xanthan gum, 6-8 parts of sodium lignosulfonate, 5-7 parts of sodium dodecyl sulfate, 2-4 parts of sodium dodecyl benzene sulfonate and 60-65 parts of deionized water.

Preferably, the other nitrogen fertilizers are any one or more of potassium nitrate, ammonium sulfate, monoammonium phosphate and diammonium phosphate; the phosphate fertilizer is one or more of monoammonium phosphate, monopotassium phosphate and diammonium phosphate; the potash fertilizer is any one or more of potassium sulfate, potassium nitrate and potassium dihydrogen phosphate; the trace elements are any one or more of zinc, iron, manganese, copper and boron.

Furthermore, the trace elements are selected from one or more of sodium zinc ethylene diamine tetraacetate, sodium iron ethylene diamine tetraacetate, sodium manganese ethylene diamine tetraacetate, sodium copper ethylene diamine tetraacetate and borax.

The invention relates to a preparation method of a urea-coated humic acid composite granular fertilizer, which comprises the following steps:

1) taking humic acid or salt thereof and trace elements, crushing, stirring, uniformly mixing, spraying a composite binder, granulating, drying and screening to obtain small particles with the particle size of 0.5-0.6 mm;

2) taking other nitrogenous fertilizer, phosphate fertilizer and potash fertilizer, crushing, stirring and uniformly mixing to obtain nitrogen-phosphorus-potassium mixed powder; continuously spraying a composite binder in the small granules obtained in the step 1), then adding mixed nitrogen-phosphorus-potassium powder to wrap the mixed nitrogen-phosphorus-potassium powder on the surfaces of the small granules, granulating, drying and screening to obtain medium granules with the grain size of 1.4-1.6 mm;

3) taking urea, and crushing to obtain urea powder; spraying the composite binder again in the medium granules obtained in the step 3), then adding urea powder to coat the urea powder on the surface of the medium granules, granulating, drying and screening to obtain large granules with the grain size of 1.9-2.2mm, namely the urea-coated humic acid composite granular fertilizer.

Preferably, in the step 1), the drying is drying in hot air at 75-85 ℃ for 8-12 min.

Preferably, in the step 2), the drying is drying in hot air at 45-55 ℃ for 8-12 min.

Preferably, in the step 3), the drying is carried out for 25-35min in hot air at 45-55 ℃.

Preferably, in the step 1), the particle size of the granules obtained by granulation is 0.5-0.8 mm.

Preferably, in the step 2), the particle size of the granules obtained by granulation is 1.5-1.8 mm.

Preferably, in the step 3), the particle size of the granules obtained by granulating is 1.9-2.4 mm.

Example one

The invention relates to a preparation method of a urea-coated humic acid composite granular fertilizer, which comprises the following steps:

1) weighing the following raw materials in parts by weight:

7 parts of urea, 5 parts of potassium humate, 63 parts of potassium nitrate, 13 parts of monopotassium phosphate, 10 parts of potassium sulfate, 0.5 part of EDTA-Cu, 0.5 part of EDTA-Fe, 0.4 part of EDTA-Mn, 0.3 part of EDTA-Zn, 0.3 part of borax and 3 parts of composite binder;

the composite binder comprises the following components in parts by weight: 10 parts of hydroxymethyl cellulose, 10 parts of xanthan gum, 7 parts of sodium lignin sulfonate, 6 parts of sodium dodecyl sulfate, 3 parts of sodium dodecyl benzene sulfonate and 64 parts of deionized water;

2) taking potassium humate, EDTA-Cu, EDTA-Fe, EDTA-Mn, EDTA-Zn and borax, crushing, adding into a high-speed granulator, stirring, uniformly mixing, spraying a composite binder, granulating to form particles of 0.6mm, introducing hot air at 75 ℃ for drying for 12min, and screening to obtain small particles with the particle size of 0.5 mm;

3) taking potassium nitrate, monopotassium phosphate and potassium sulfate, crushing, stirring and uniformly mixing to obtain nitrogen-phosphorus-potassium mixed powder; adding the small granules obtained in the step 2) into a high-speed granulator again, continuously spraying a composite binder, then adding mixed nitrogen phosphorus potassium powder to enable the mixed phosphorus potassium powder to be coated on the surfaces of the small granules, granulating to form granules of 1.6mm, introducing hot air of 45 ℃ for drying for 12min, and screening to obtain medium granules of which the particle size is 1.5 mm;

4) taking urea, and crushing to obtain urea powder; adding the medium particles obtained in the step 3) into the high-speed granulator again, spraying the composite binder again, then adding urea powder to coat the urea powder on the surface of the medium particles, granulating to form particles with the particle size of 2.2mm, introducing hot air at 45 ℃ for drying for 35min, and screening to obtain large particles with the particle size of 2.0mm, namely the urea-coated humic acid composite granular fertilizer.

The high-potassium urea coated humic acid composite granular fertilizer is characterized in that the contents of nitrogen, phosphorus and potassium are respectively 13-7-40; is generally used in the swelling period of crops and can improve the quality of the fruits of the crops.

Example two

The invention relates to a preparation method of a urea-coated humic acid composite granular fertilizer, which comprises the following steps:

1) weighing the following raw materials in parts by weight:

60 parts of urea, 5 parts of potassium humate, 16 parts of monoammonium phosphate, 17 parts of potassium sulfate, 0.8 part of EDTA-Fe, 0.6 part of EDTA-Zn, 0.6 part of borax and 3 parts of a composite binder;

the composite binder comprises the following components in parts by weight: 10 parts of hydroxymethyl cellulose, 10 parts of xanthan gum, 7 parts of sodium lignin sulfonate, 6 parts of sodium dodecyl sulfate, 3 parts of sodium dodecyl benzene sulfonate and 64 parts of deionized water;

2) taking potassium humate, EDTA-Fe, EDTA-Zn and borax, crushing, adding into a high-speed granulator, stirring, uniformly mixing, spraying a composite binder, granulating to form particles of 0.8mm, introducing hot air at 80 ℃ for drying for 10min, and screening to obtain small particles with the particle size of 0.6 mm;

3) taking monoammonium phosphate and potassium sulfate, crushing, stirring and uniformly mixing to obtain nitrogen-phosphorus-potassium mixed powder; adding the small granules obtained in the step 2) into a high-speed granulator again, continuously spraying a composite binder, then adding mixed nitrogen-phosphorus-potassium powder to enable the mixed nitrogen-phosphorus-potassium powder to be coated on the surfaces of the small granules, granulating to form granules of 1.7mm, introducing hot air of 50 ℃ for drying for 10min, and screening to obtain medium granules of which the particle size is 1.6 mm;

4) taking urea, and crushing to obtain urea powder; adding the medium particles obtained in the step 3) into the high-speed granulator again, spraying the composite binder again, then adding urea powder to coat the urea powder on the surface of the medium particles, granulating to form particles with the particle size of 2.4mm, introducing hot air at 50 ℃ for drying for 30min, and screening to obtain large particles with the particle size of 2.2mm, namely the urea-coated humic acid composite granular fertilizer.

The high-nitrogen urea coated humic acid composite granular fertilizer has the contents of nitrogen, phosphorus and potassium of 30-10-10; is generally used in the early stage of crop growth to promote the growth of crop branches and leaves.

EXAMPLE III

The invention relates to a preparation method of a urea-coated humic acid composite granular fertilizer, which comprises the following steps:

1) weighing the following raw materials in parts by weight:

21 parts of urea, 10 parts of potassium humate, 18 parts of potassium sulfate, 37 parts of monoammonium phosphate, 12 parts of monopotassium phosphate, 0.8 part of EDTA-Fe, 0.4 part of EDTA-Mn, 0.5 part of EDTA-Cu, 0.3 part of borax and 3 parts of composite binder;

the composite binder comprises the following components in parts by weight: 10 parts of hydroxymethyl cellulose, 10 parts of xanthan gum, 7 parts of sodium lignin sulfonate, 6 parts of sodium dodecyl sulfate, 3 parts of sodium dodecyl benzene sulfonate and 64 parts of deionized water;

2) taking potassium humate, EDTA-Cu, EDTA-Mn, EDTA-Fe and borax, crushing, adding into a high-speed granulator, stirring, uniformly mixing, spraying a composite binder, granulating to form particles of 0.5mm, introducing hot air at 75 ℃ for drying for 8min, and screening to obtain small particles with the particle size of 0.5 mm;

3) taking potassium sulfate, monoammonium phosphate and monopotassium phosphate, crushing, stirring and uniformly mixing to obtain nitrogen-phosphorus-potassium mixed powder; adding the small granules obtained in the step 2) into a high-speed granulator again, continuously spraying a composite binder, then adding mixed nitrogen-phosphorus-potassium powder to enable the mixed nitrogen-phosphorus-potassium powder to be coated on the surfaces of the small granules, granulating to form granules of 1.4mm, introducing hot air of 55 ℃ for drying for 8min, and screening to obtain medium granules of which the particle size is 1.4 mm;

4) taking urea, and crushing to obtain urea powder; adding the medium particles obtained in the step 3) into the high-speed granulator again, spraying the composite binder again, then adding urea powder to coat the urea powder on the surface of the medium particles, granulating to form particles with the particle size of 1.9mm, introducing hot air at 55 ℃ for drying for 25min, and screening to obtain large particles with the particle size of 1.9mm, namely the urea-coated humic acid composite granular fertilizer.

The high-phosphorus urea coated humic acid composite granular fertilizer has the contents of nitrogen, phosphorus and potassium of 15-30-15; it is a seedling stage formula and is mainly used in the early rooting process of crops to promote the root development of the crops.

Comparative example 1

Weighing the following raw materials according to the formula of the first embodiment: 7 parts of urea, 5 parts of potassium humate, 63 parts of potassium nitrate, 13 parts of monopotassium phosphate, 10 parts of potassium sulfate, 0.5 part of EDTA-Cu, 0.5 part of EDTA-Fe, 0.4 part of EDTA-Mn, 0.3 part of EDTA-Zn and 0.3 part of borax;

according to the prior art, the raw materials are sequentially mixed to obtain the humic acid water-soluble fertilizer, namely the reference sample I.

Comparative example 2

Weighing the following raw materials according to the formula of the second embodiment: 60 parts of urea, 5 parts of potassium humate, 16 parts of monoammonium phosphate, 17 parts of potassium sulfate, 0.8 part of EDTA-Fe, 0.6 part of EDTA-Zn and 0.6 part of borax;

and mixing the raw materials in sequence according to the existing process to obtain the humic acid water-soluble fertilizer, namely a reference sample II.

Comparative example 3

Weighing the following raw materials according to the formula of the third embodiment: 21 parts of urea, 10 parts of potassium humate, 18 parts of potassium sulfate, 37 parts of monoammonium phosphate, 12 parts of monopotassium phosphate, 0.8 part of EDTA-Fe, 0.4 part of EDTA-Mn, 0.5 part of EDTA-Cu and 0.3 part of borax;

according to the prior art, the raw materials are sequentially mixed to obtain the humic acid water-soluble fertilizer, namely the control sample III.

Experiment 1

Carrying out a plate-bond resistance test experiment on three parts of urea-coated humic acid composite granular fertilizer obtained in the first embodiment to the third embodiment of the invention, a first reference sample, a second reference sample and a third reference sample respectively, putting 100g of each of the six parts of fertilizer into a constant-temperature and constant-humidity box with the temperature of 40 ℃ and the relative humidity of 80%, standing for 4h, taking out and measuring the caking rate of the product, and listing the experiment results in a table 1; the calculation formula of the caking rate is as follows:

blocking rate ═ 100% (weight of blocked sample/total weight of sample).

As can be seen from table 1, under the same conditions, the caking rate of the urea-coated humic acid composite granular fertilizer obtained by the method of the present invention is significantly reduced, namely, the caking rate is reduced by about 12.38% in the first example, by about 63.64% in the second example, and by about 25.38% in the third example.

TABLE 1 test results of the resistance to plate-caking of different fertilizers

Sample name	Caking ratio 1 (%)	Caking ratio 2 (%)	Caking ratio 3 (%)	Caking ratio 4 (%)	Caking ratio 5 (%)
						Example one	0.6	0.3	0.5	0.1	0.7
Comparison sample one	11.4	12.7	13.2	10.5	16.3
						Example two	2.6	2.2	3.1	1.5	2.8
Control 2	60.7	70.4	68.5	50.6	80.2
						EXAMPLE III	1.2	1.4	1.5	1.7	1.1
Control sample three	20.6	24.8	31.3	26.6	30.5

Experiment 2

Three parts of urea-coated humic acid composite granular fertilizer obtained in the first to third embodiments of the invention, and a first control sample, a second control sample and a third control sample are respectively subjected to a nutrient element stability test experiment, 0.2g of each of the six parts of fertilizer is taken, the nitrogen, phosphorus and potassium contents of the six parts of fertilizer are measured according to a method specified in NYT1977, 5 samples are taken for each part of fertilizer, the deviation amplitude is the deviation between the average value of the measured values and the theoretical value, and the experimental results are listed in tables 2, 3 and 4.

As can be seen from table 2, the total nitrogen deviation amplitude of the urea-coated humic acid composite granular fertilizer obtained in the first to third embodiments of the present invention is not more than 2.00%; the total nitrogen deviation for example one was only 0.77%, whereas the total nitrogen deviation for control one was 5.08%; the total nitrogen bias for example two was 1.07%, whereas the total nitrogen bias for control two was 4.20%; the total nitrogen bias for example three was 2.00%, whereas the total nitrogen bias for control three was 5.87%.

TABLE 2 stability test results for nitrogen content of different fertilizers

Sample name	Total nitrogen 1 (%)	Total nitrogen 2 (%)	Total nitrogen 3 (%)	Total nitrogen 4 (%)	Total nitrogen 5 (%)	Total nitrogen deviation amplitude (%)
							Example one	13.1	12.9	12.8	13.0	12.9	0.77
Comparison sample one	12.4	11.7	12.8	13.5	12.3	5.08
							Example two	30.6	30.2	30.1	29.5	29.8	1.07
Control 2	30.2	30.4	28.5	26.6	29.2	4.20
							EXAMPLE III	15.2	15.4	15.5	14.7	15.1	2.00
Control sample three	15.6	14.8	13.3	13.6	14.5	5.87

As can be seen from table 3, the deviation ranges of the phosphorus pentoxide of the urea-coated humic acid composite granular fertilizer obtained in the first to third embodiments of the present invention are not more than 2.00%; the phosphorus pentoxide bias for example one was 1.43%, whereas the phosphorus pentoxide bias for control one was 6.29%; the phosphorus pentoxide bias for example two was 2.00%, whereas the phosphorus pentoxide bias for control two was 10.20%; the phosphorus pentoxide bias for example three was 0.73%, whereas the phosphorus pentoxide bias for control three was 5.73%.

TABLE 3 stability test results for phosphorus content of different fertilizers

As can be seen from table 4, the deviation amplitudes of the urea-coated humic acid composite granular fertilizer potassium oxide obtained in the first to third embodiments of the present invention are not more than 3.20%; the deviation of potassium oxide for example one was only 0.35%, whereas the deviation of potassium oxide for control one was 1.35%; the deviation of potassium oxide for example two was 3.20%, whereas the deviation of potassium oxide for control two was 11.40%; the deviation of potassium oxide was 2.00% for example three, whereas the deviation of potassium oxide was 6.00% for control three.

TABLE 4 results of different treatments on potassium content

Therefore, the urea-coated humic acid composite granular fertilizer obtained by the invention highly meets the design requirements in content and can achieve the effect of precise fertilization.

Experiment 3

Three parts of urea-coated humic acid composite granular fertilizer obtained in the first to third embodiments of the invention, and a fertilization experiment was performed on the first control sample, the second control sample and the third control sample, respectively.

In a test field greenhouse of the institute of agricultural science and research, Shandong province tobacco terrace, 1 mu of area is used in a test cell, and a drip irrigation fertilization method is adopted to respectively carry out three treatments. In the first treatment, no fertilizer is applied in the rooting period, the growing period and the fruiting period of the tomatoes. Secondly, 8Kg of the high-potassium composite granular fertilizer obtained in the first embodiment of the invention is applied to the tomato in the rooting period; in the growing period of tomatoes, 8Kg of the high-nitrogen composite granular fertilizer obtained in the second embodiment of the invention is applied, and in the fruiting period of tomatoes, 8Kg of the high-phosphorus composite granular fertilizer obtained in the third embodiment of the invention is applied. Treating the tomato in the rooting period by applying 10Kg of the high-potassium mixed fertilizer of the control sample I; in the growing period of the tomatoes, 10Kg of the high-nitrogen mixed fertilizer of the second control sample is applied, and in the fruiting period of the tomatoes, 10Kg of the high-phosphorus mixed fertilizer of the third control sample is applied.

In the rooting period of the tomatoes, randomly extracting 10 tomatoes 5 days after fertilization, measuring the diameter of a third section of a stem below a stem head of the tomatoes, and averaging; in the tomato fruiting period, randomly extracting 10 tomatoes 5 days after fertilization, measuring the weight of each tomato and the diameter of each tomato, and averaging; the results are shown in Table 5.

As can be seen from table 5, the tomatoes to which the urea-coated humic acid composite granular fertilizer obtained in the first to third examples of the present invention was applied were significantly superior to the tomatoes to which the mixed fertilizers of the first, second and third control samples were applied, in terms of plant stem, individual fruit weight and fruit diameter; therefore, the urea-coated humic acid composite granular fertilizer achieves the effects of losing weight and increasing yield in the plant growth process.

TABLE 5 Effect of different fertilizers on tomato fruit

Sample name	Diameter of the third section stem (mm) below the tap	Weight of a fruit (g)	Fruit diameter (cm)
				Process one	8.93	450.2	8.0
Treatment two	13.75	525.5	9.5
				Treatment three	11.35	502.3	8.5

Therefore, compared with the prior art, the invention has the beneficial effects that: the invention is a water-soluble fertilizer of urea coating humic acid, urea wraps up on the external surface of humic acid evenly through the compound binder, fully protect the original molecular structure of humic acid, has kept the biological activity of humic acid, meanwhile, the urea of the outer layer is apt to absorb water, has promoted the water-solubility of this compound granular fertilizer, even in the environment of water shortage, can absorb the moisture in the air through the characteristic of urea low moisture absorption point, thus accelerate the dissolution release of this compound granular fertilizer; according to different requirements of crops on nutrient elements in different periods, the composite granular fertilizer with the core-shell structure preferentially releases nitrogen elements to promote the growth of the crops, then releases phosphorus, potassium and trace elements in sequence, meets the nutritional requirements of the crops, and finally releases potassium humate to promote the absorption of the crops on the nitrogen, the phosphorus and the potassium and improve the soil environment; the fertilizer has the advantages of stable content of various nutrient elements, less dust, convenient use, difficult hardening, good performance of preventing soil from caking, good water-soluble effect, wide application range, capability of being applied in a broadcasting way, drop irrigation or spray irrigation, capability of realizing accurate fertilization in the plant growth process, improved utilization rate of the fertilizer and achievement of the effects of losing weight and increasing yield; the preparation method is simple, convenient to operate and easy to realize industrialization.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.