Long-acting compound fertilizer and method for preparing the same

Abstract

The application discloses a long-acting compound fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. The long-acting compound fertilizer is prepared from the following raw materials in parts by weight: urea 40-60 parts, diammonium phosphate 20-30 parts, potassium chloride 30-40 parts, solid slow-release material 80-100 parts, humic acid 15-25 parts, carboxymethyl cellulose 6-10 parts and water 300-400 parts; the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose at a mass ratio of 2:1. The chemical adsorption of the modified nanocellulose and the physical adsorption of the modified sepiolite powder in the slow-release material jointly form a more stable slow-release system, significantly prolong the release period of the fertilizer, improve the slow-release effect, and further improve the soil environment, improve the water-retaining capacity and fertility of the soil and promote the growth of crops.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fertilizers, and particularly relates to a long-acting compound fertilizer and a preparation method thereof. BACKGROUND

[0002] Fertilizer, as one of the most critical material foundations in agricultural production, plays an indispensable role in crop yield increase. So far, applying chemical fertilizer is still the most effective and convenient measure to ensure the nutrients required for crop growth. In order to maximize crop yield, people began to overuse chemical fertilizer, and the environmental pollution problem caused by this behavior has gradually emerged. Large amounts of chemical fertilizer will inevitably lead to the release of chemical fertilizer into the environment through runoff, which has an adverse effect on biology, and long-term drinking of water sources polluted by chemical fertilizer will also pose a threat to human health. At the same time, the traditional chemical fertilizer has a very fast dissolution rate, and when the fertilizer is applied to the soil, a large amount of nutrients can easily be lost to the natural environment through gas volatilization, leaching and surface runoff, only a small part of the nutrients can be absorbed and fully utilized by plants, thus resulting in low fertilizer utilization rate. It is reported that the seasonal utilization rate of nitrogen fertilizer in China is 30-35%, the utilization rate of phosphorus fertilizer is 10-25%, and the utilization rate of potassium fertilizer is 30-45%. Fertilizer loss and unreasonable fertilization methods have caused huge economic losses and resource waste, and also brought many serious environmental pollution problems, such as nitrate leaching, groundwater pollution, soil acidification, heavy metal pollution and freshwater eutrophication, etc. In addition, irregular application of fertilizer will also cause fluctuations between nutrient concentrations, which directly affects the growth of crops. In order to improve the utilization rate of fertilizer and reduce the impact of over-fertilization on the environment, it is necessary to develop new types of fertilizer to slowly provide nutrients to target plants, reduce nutrient loss and improve crop yield.

[0003] Slow-release fertilizer refers to a new type of fertilizer capable of delaying or controlling the release rate of nutrients. Slow-release fertilizer and controlled-release fertilizer are collectively referred to as slow-release fertilizer, and there is no obvious difference in a broad sense. In a narrow sense, slow-release fertilizer is a fertilizer whose nutrient release rate is slowed down through chemical or biological methods, and is affected by many external factors such as soil pH, microbial activity, and soil moisture content during release. Controlled-release fertilizer is a water-soluble fertilizer coated with a film to slow down the release of nutrients. When the coated fertilizer particles come into contact with wet soil, the water in the soil penetrates the film layer and enters the fertilizer, causing the fertilizer to dissolve locally, and the dissolved fertilizer slowly diffuses outward through the micropores on the film layer. Compared with traditional fertilizers, slow-release fertilizers have many advantages, such as reducing environmental pollution, providing sustained fertilizer supply, and improving plant fertilizer use efficiency. Many commercially manufactured slow-release fertilizers are high in cost and low in nutrient release rate. The coating layer of slow / controlled-release fertilizers is usually composed of petroleum-based polymers such as polyolefins, polyvinylidene chloride, acrylic resins, and polysulfones. These materials usually involve complex manufacturing processes, including some toxic chemicals, are non-renewable resources, and are difficult to biodegrade. This will lead to various environmental and energy conflicts, such as the accumulation of non-degradable waste in the ground and the further consumption of fossil fuels. SUMMARY

[0004] The purpose of the present application is to provide a long-acting compound fertilizer which has good slow-release effect, can significantly improve fertilizer utilization rate, reduce nutrient loss, and improve crop yield.

[0005] To achieve the above technical purpose, the technical scheme adopted by the present application is:

[0006] A long-acting compound fertilizer is prepared from the following raw materials by weight: urea 40-60 parts, diammonium phosphate 20-30 parts, potassium chloride 30-40 parts, solid slow-release material 80-100 parts, humic acid 15-25 parts, carboxymethyl cellulose 6-10 parts, and water 300-400 parts; the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a mass ratio of 2:1.

[0007] Preferably, the modified sepiolite powder is prepared by the following method:

[0008] (1) Sepiolite powder is added to a 5wt% sulfuric acid solution according to the solid-liquid ratio, heated to 80℃ in a water bath, and reacted for 5-6 hours. After filtration, the filter residue is washed to neutral with deionized water, dried in a vacuum drying oven, and then pulverized to obtain acidified sepiolite powder;

[0009] (2) 5g of acidified sepiolite powder is dispersed in 40ml of deionized water to obtain a suspension A;

[0010] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0011] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0012] Preferably, the solid-liquid ratio in step (1) is 1g:10ml.

[0013] Preferably, the modified nano-hydroxyapatite in step (3) is prepared as follows:

[0014] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0015] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution according to the material-to-liquid ratio. Stir the reaction at room temperature for 2-3 hours to obtain mixture II;

[0016] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture in a water bath to 60°C, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place it in a freeze dryer and dry at -20°C for 24 h. Grind it into powder to obtain modified nano hydroxyapatite.

[0017] Preferably, in step (b), the ratio of epoxidized soybean oil to NaOH solution is 1g:100ml.

[0018] Preferably, in step (c), the volume ratio of suspension I to mixture II is 1:2.

[0019] Preferably, the modified nanocellulose is prepared by the following method:

[0020] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0021] S2: Mix nitric acid triacetic acid, N,N-dimethylamide and pyridine, add an appropriate amount of acetic anhydride, heat to 75°C under a nitrogen atmosphere, and stir magnetically for 10-15 hours to obtain mixture A;

[0022] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir the reaction for 10-15 hours. After the reaction is completed, filter the mixture, wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose.

[0023] Preferably, in step S2, the mass ratio of nitroglycerin, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.5-2:1.5-1.6:1-1.2.

[0024] Preferably, in step S3, the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:3-5ml.

[0025] The lignocellulose used in this invention is prepared from raw materials such as wood, crop straw, bamboo, and sugarcane bagasse through conventional operations such as dewaxing, lignin removal, and hemicellulose removal using reagents such as ethanol, sodium hydroxide, and sodium sulfide.

[0026] This invention also provides a method for preparing the above-mentioned long-acting compound fertilizer, which includes the following steps:

[0027] Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material;

[0028] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0029] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0030] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0031] The beneficial effects of this invention are:

[0032] (1) This invention uses a solid slow-release material prepared by modifying sepiolite powder and modified nanocellulose as a fertilizer carrier. After modification, the sepiolite powder has a large number of modified hydroxyapatite nanoparticles attached to its unique fiber and pore structure, making it rougher and significantly increasing its specific surface area and adsorption capacity. This structure can effectively adsorb and encapsulate nutrients such as nitrogen, phosphorus, and potassium in the fertilizer, slowing down their release rate in the soil and improving the slow-release effect of the fertilizer. At the same time, the nano-hydroxyapatite modified with epoxidized soybean oleic acid has enhanced surface hydrophobicity, further reducing nutrient volatilization and leaching, effectively controlling the release of fertilizer nutrients, and improving the stability and slow-release performance of the material. Moreover, the raw materials such as sepiolite powder, hydroxyapatite, and nanocellulose all have good biodegradability and are environmentally friendly. While improving fertilizer utilization, it reduces the amount of fertilizer applied and reduces environmental pollution.

[0033] (2) The modified nanocellulose used in this invention is modified by esterification of aminotriacetic acid. The carboxyl and ester groups on the surface of the cellulose can interact with the nutrients in the fertilizer and slow down the release rate of nutrients. The porous structure of the modified sepiolite powder also acts as a physical barrier for slow release and controls the release of nutrients. When the two are combined, the chemical adsorption of the modified nanocellulose and the physical adsorption of the modified sepiolite powder work together to form a more stable slow release system, which significantly prolongs the release cycle of fertilizer and improves the slow release effect. In addition, the combination of the two can further improve the soil environment, improve the soil's water retention capacity and fertility, and promote crop growth. Attached Figure Description

[0034] Figure 1 These are scanning electron microscope images of the sepiolite powder used in this invention before and after modification, where a is before modification and b is after modification.

[0035] Figure 2 This is a graph showing the cumulative nitrogen release rate in Test Example 2 of the present invention;

[0036] Figure 3 This is a graph showing the cumulative phosphorus release rate in Test Example 2 of the present invention;

[0037] Figure 4 This is a graph showing the cumulative potassium release rate in Test Example 2 of the present invention. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. The sepiolite powder used in the present invention was purchased from Lingshou County Derui Mining Co., Ltd.; the lignocellulose was purchased from Shandong Haosong Fiber Co., Ltd.

[0039] Example 1

[0040] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 40 kg urea, 20 kg diammonium phosphate, 30 kg potassium chloride, 80 kg solid slow-release material, 15 kg humic acid, 6 kg carboxymethyl cellulose, and 300 kg water; wherein the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a mass ratio of 2:1.

[0041] The modified sepiolite powder was prepared using the following method:

[0042] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0043] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0044] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0045] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0046] The modified nano-hydroxyapatite is prepared as follows:

[0047] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0048] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0049] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0050] The modified nanocellulose was prepared using the following method:

[0051] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0052] S2: Mix nitric acid triacetic acid, N,N-dimethylamide, and pyridine, then add an appropriate amount of acetic anhydride. Heat the mixture to 75°C under a nitrogen atmosphere and stir magnetically for 10 hours to obtain a mixture A. The mass ratio of nitric acid triacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.5:1.5:1.

[0053] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 10 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:3ml.

[0054] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0055] Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material;

[0056] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0057] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0058] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0059] Example 2

[0060] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 60 kg of urea, 30 kg of diammonium phosphate, 40 kg of potassium chloride, 100 kg of solid slow-release material, 25 kg of humic acid, 10 kg of carboxymethyl cellulose, and 400 kg of water; wherein the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a mass ratio of 2:1.

[0061] The modified sepiolite powder was prepared using the following method:

[0062] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0063] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0064] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0065] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0066] The modified nano-hydroxyapatite is prepared as follows:

[0067] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0068] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0069] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0070] The modified nanocellulose was prepared using the following method:

[0071] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0072] S2: Mix nitric acid triacetic acid, N,N-dimethylamide, and pyridine, then add an appropriate amount of acetic anhydride. Heat the mixture to 75°C under a nitrogen atmosphere and stir magnetically for 15 hours to obtain a mixture A. The mass ratio of nitric acid triacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride is 1:2:1.6:1.2.

[0073] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 15 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:5ml.

[0074] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0075] Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material;

[0076] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0077] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0078] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is below 10%. Then granulate it using a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain a long-acting compound fertilizer. Example 3

[0079] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg urea, 25 kg diammonium phosphate, 35 kg potassium chloride, 90 kg solid slow-release material, 20 kg humic acid, 8 kg carboxymethyl cellulose, and 350 kg water; wherein the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a mass ratio of 2:1.

[0080] The modified sepiolite powder was prepared using the following method:

[0081] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0082] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0083] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0084] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0085] The modified nano-hydroxyapatite is prepared as follows:

[0086] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0087] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0088] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0089] The modified nanocellulose was prepared using the following method:

[0090] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0091] S2: Mix nitric acid triacetic acid, N,N-dimethylamide, and pyridine, then add an appropriate amount of acetic anhydride. Heat the mixture to 75°C under a nitrogen atmosphere and stir magnetically for 12 hours to obtain a mixture A. The mass ratio of nitric acid triacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.6:1.5:1.1.

[0092] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 12 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:4ml.

[0093] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0094] Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material;

[0095] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0096] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0097] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0098] Comparative Example 1

[0099] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg urea, 25 kg diammonium phosphate, 35 kg potassium chloride, 90 kg solid slow-release material, 20 kg humic acid, 8 kg carboxymethyl cellulose, and 350 kg water; wherein the solid slow-release material is modified sepiolite powder.

[0100] The modified sepiolite powder was prepared using the following method:

[0101] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0102] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0103] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0104] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0105] The modified nano-hydroxyapatite is prepared as follows:

[0106] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0107] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0108] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0109] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0110] Step 1: Prepare modified sepiolite powder to obtain solid sustained-release materials;

[0111] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0112] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0113] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0114] This comparative example is basically the same as Example 3, except that the solid slow-release material is only modified sepiolite powder.

[0115] Comparative Example 2

[0116] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg urea, 25 kg diammonium phosphate, 35 kg potassium chloride, 90 kg solid slow-release material, 20 kg humic acid, 8 kg carboxymethyl cellulose, and 350 kg water; wherein the solid slow-release material is modified nanocellulose.

[0117] The modified nanocellulose was prepared using the following method:

[0118] S1: Lignocellulose was added to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heated to 80℃, and reacted under magnetic stirring for 1h. After the reaction was completed, the solution was filtered and dried to obtain nanocellulose. The mass ratio of aminotriacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride was 1:1.6:1.5:1.1.

[0119] S2: Mix nitric acid triacetic acid, N,N-dimethylamide and pyridine, add an appropriate amount of acetic anhydride, heat to 75°C under a nitrogen atmosphere, and stir magnetically for 12 hours to obtain mixture A;

[0120] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 12 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:4ml.

[0121] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0122] Step 1: Prepare modified nanocellulose to obtain solid sustained-release material;

[0123] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0124] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0125] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0126] This comparative example is basically the same as Example 3, except that the solid slow-release material is only modified nanocellulose.

[0127] Comparative Example 3

[0128] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg urea, 25 kg diammonium phosphate, 35 kg potassium chloride, 90 kg solid slow-release material, 20 kg humic acid, 8 kg carboxymethyl cellulose, and 350 kg water; wherein the solid slow-release material is composed of sepiolite powder and modified nanocellulose in a mass ratio of 2:1.

[0129] The modified nanocellulose was prepared using the following method:

[0130] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0131] S2: Mix nitric acid triacetic acid, N,N-dimethylamide, and pyridine, then add an appropriate amount of acetic anhydride. Heat the mixture to 75°C under a nitrogen atmosphere and stir magnetically for 12 hours to obtain a mixture A. The mass ratio of nitric acid triacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.6:1.5:1.1.

[0132] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 12 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:4ml.

[0133] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0134] Step 1: Prepare modified nanocellulose and mix it evenly with sepiolite powder in a certain proportion to obtain a solid sustained-release material;

[0135] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0136] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0137] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0138] This comparative example is basically the same as Example 3, except that the sepiolite powder in the solid slow-release material was not modified.

[0139] Comparative Example 4

[0140] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg urea, 25 kg diammonium phosphate, 35 kg potassium chloride, 90 kg solid slow-release material, 20 kg humic acid, 8 kg carboxymethyl cellulose, and 350 kg water; wherein the solid slow-release material is composed of modified sepiolite powder and nanocellulose in a mass ratio of 2:1.

[0141] The modified sepiolite powder was prepared using the following method:

[0142] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0143] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0144] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0145] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0146] The modified nano-hydroxyapatite is prepared as follows:

[0147] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0148] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0149] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0150] The nanocellulose was prepared by the following method: lignocellulose was added to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heated to 80℃, and reacted for 1h under magnetic stirring. After the reaction was completed, the mixture was filtered and dried to obtain nanocellulose.

[0151] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0152] Step 1: Prepare modified sepiolite powder and nanocellulose separately, and mix them evenly in a certain proportion to obtain a solid sustained-release material;

[0153] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0154] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0155] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0156] This comparative example is basically the same as Example 3, except that the nanocellulose in the solid slow-release material was not modified.

[0157] Comparative Example 5

[0158] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg of urea, 25 kg of diammonium phosphate, 35 kg of potassium chloride, 90 kg of solid slow-release material, 20 kg of humic acid, 8 kg of carboxymethyl cellulose, and 350 kg of water; wherein the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a 1:1 mass ratio.

[0159] The modified sepiolite powder was prepared using the following method:

[0160] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0161] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0162] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0163] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0164] The modified nano-hydroxyapatite is prepared as follows:

[0165] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0166] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0167] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0168] The modified nanocellulose was prepared using the following method:

[0169] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0170] S2: Mix nitric acid triacetic acid, N,N-dimethylamide, and pyridine, then add an appropriate amount of acetic anhydride. Heat the mixture to 75°C under a nitrogen atmosphere and stir magnetically for 12 hours to obtain a mixture A. The mass ratio of nitric acid triacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.6:1.5:1.1.

[0171] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 12 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:4ml.

[0172] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0173] Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material;

[0174] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0175] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0176] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0177] This comparative example is basically the same as Example 3, except that the mass ratio of modified sepiolite powder to modified nanocellulose in the solid slow-release material is different.

[0178] Comparative Example 6

[0179] A long-acting compound fertilizer is made from the following raw materials in parts by weight: 50 kg of urea, 25 kg of diammonium phosphate, 35 kg of potassium chloride, 90 kg of solid slow-release material, 20 kg of humic acid, 8 kg of carboxymethyl cellulose, and 350 kg of water; wherein the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a mass ratio of 1:2.

[0180] The modified sepiolite powder was prepared using the following method:

[0181] (1) Add sepiolite powder to 5wt% sulfuric acid solution at a solid-liquid ratio of 1g:10ml, heat in a water bath to 80℃, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder.

[0182] (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A;

[0183] (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B;

[0184] (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Keep the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and let stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder.

[0185] The modified nano-hydroxyapatite is prepared as follows:

[0186] (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I;

[0187] (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution at a ratio of 1 g: 100 ml. Stir the mixture at room temperature for 2-3 hours to obtain mixture II.

[0188] (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture to 60°C in a water bath, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place in a freeze dryer and dry at -20°C for 24 h. Grind into powder to obtain modified nano-hydroxyapatite. The volume ratio of suspension I to mixture II is 1:2.

[0189] The modified nanocellulose was prepared using the following method:

[0190] S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose.

[0191] S2: Mix nitric acid triacetic acid, N,N-dimethylamide, and pyridine, then add an appropriate amount of acetic anhydride. Heat the mixture to 75°C under a nitrogen atmosphere and stir magnetically for 12 hours to obtain a mixture A. The mass ratio of nitric acid triacetic acid, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.6:1.5:1.1.

[0192] S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir for 12 hours. After the reaction is completed, filter, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and vacuum dry to obtain modified nanocellulose; wherein the ratio of nanocellulose, mixture A and N,N-dimethylamide is 1g:15ml:4ml.

[0193] The above-mentioned method for preparing long-acting compound fertilizer includes the following steps:

[0194] Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material;

[0195] Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture;

[0196] Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension;

[0197] Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

[0198] This comparative example is basically the same as Example 3, except that the mass ratio of modified sepiolite powder to modified nanocellulose in the solid slow-release material is different.

[0199] Comparative Example 7

[0200] A compound fertilizer is made from the following raw materials in parts by weight: 50 kg urea, 25 kg diammonium phosphate, 35 kg potassium chloride, 20 kg humic acid, 8 kg carboxymethyl cellulose, and 350 kg water. The above raw materials are mixed evenly and then directly granulated to obtain the fertilizer. The basic composition of the above fertilizer is the same as in Example 3, the only difference being that it does not contain solid slow-release materials.

[0201] Test Example 1

[0202] Scanning electron microscopy (SEM) was used to observe the microstructure and structural characteristics of sepiolite powder before and after modification, such as... Figure 1 As shown, the microstructure of sepiolite powder before modification is a smooth nanofiber rod-like structure. After modification, the surface is loaded with a large number of irregularly sized nano-hydroxyapatite particles, which makes the surface of the sepiolite rougher, forming a micro-nano composite structure of interwoven particles and fibers. This composite morphology has a porous structure and a large specific surface area. At the same time, the modified sepiolite powder surface also contains abundant carboxyl groups, which can further enhance the adsorption of nutrients, reduce the rapid leaching of nutrients, and improve the slow-release effect of fertilizers.

[0203] Test Example 2

[0204] Determination of nutrient release characteristics in still water

[0205] Eight treatment groups were set up in the experiment, namely Example 3 and Comparative Examples 1-7. 5g of fertilizer from each treatment group was placed in a non-woven fabric tea bag, which was then placed in a plastic bottle containing 200mL of deionized water. The bottles were incubated at 25℃ for 70 days, with the bottle openings sealed with plastic film to prevent moisture evaporation. At specific time intervals (days 1, 5, 7, 21, 28, 42, and 70), 20mL of the solution was collected and stored at -20℃. The nitrogen, phosphorus, and potassium contents were then determined by the Kjeldahl method, the molybdenum antimony colorimetric method, and the flame photometry method, respectively. 20mL of deionized water was added after each collection to maintain a constant volume of the culture medium. Each sample was repeated four times, and the average value was taken. The cumulative nitrogen, phosphorus, and potassium release curves over time were plotted. The cumulative nutrient release rate of nitrogen, phosphorus, and potassium in still water for each treatment group was calculated using the following formula. The results are shown below. Figures 2-4 .

[0206] Cumulative nutrient release rate (%) = ∑Nutrient release amount (mg) in each time period / Total nutrient amount (mg) × 100%;

[0207] Nutrient release (mg) = Nutrient content in test solution (mg / L) × Test solution volume (V);

[0208] Total nutrients (g) = fertilizer mass (g) × nutrient content (%);

[0209] Nutrient accumulation and release curves are an important means of characterizing the nutrient slow-release performance of slow-release fertilizers. From Figures 2-4 It can be seen that in Comparative Example 7, without the addition of any solid slow-release material, the initial nutrient release efficiency of nitrogen, phosphorus, and potassium was relatively high, and the nutrient release rate exceeded 80% after 5 days. Compared with Comparative Examples 1-6, the nutrient release rate curves of nitrogen, phosphorus, and potassium in Example 3 of this invention were also significantly slower. This indicates that the long-acting compound fertilizer prepared by this invention has a longer-lasting effect. The chemical adsorption of modified nanocellulose and the physical adsorption of modified sepiolite powder in the prepared solid slow-release material work together to form a more stable slow-release system, significantly extending the fertilizer release cycle and improving the slow-release effect. In addition, the combined use of the two can further improve the soil environment, enhance the soil's water retention capacity and fertility, and promote crop growth.

[0210] Field planting application trial

[0211] Experimental site: Farmland in Zhaojiahezi Village, Economic Development Zone, Junan County, Linyi City, Shandong Province. The soil was loam, and its basic physicochemical properties before planting were: pH 8.01, organic matter content 19.75 g / kg, total nitrogen content 1.05 g / kg, nitrate nitrogen content 20.55 mg / kg, ammonium nitrogen content 10.01 mg / kg, available phosphorus content 19.33 mg / kg, and available potassium content 132.55 mg / kg. The cultivation pattern was wheat-corn rotation, and the seeding rate was 15 kg / mu.

[0212] The experiment consisted of 10 treatments: Examples 1-3 and Comparative Examples 1-7. Each treatment group had an area of ​​100 m². 2 Each treatment was repeated in triplicate, and the results were averaged. The tested crop variety was wheat, specifically Linmai 14. Before planting, fertilizer was applied as basal fertilizer to all treatment groups in a single application to the soil at a rate of 40 kg / mu (approximately 667 square meters). The control group received no fertilizer. Apart from the application of different fertilizers, all other routine field management practices were the same across treatment groups, with no additional fertilization.

[0213] Wheat was harvested at maturity, and wheat yield and yield composition were statistically analyzed. The specific results are shown in Table 1.

[0214] Table 1. Wheat yield and composition in different treatment groups

[0215]

[0216] As can be seen from the data in Table 1 above, after using the long-acting compound fertilizer of the present invention, the wheat yield increased by more than 16.1% compared with Comparative Example 7. However, the increase in wheat yield of Comparative Examples 1-6 compared with Comparative Example 7 was less than that of Examples 1-3 of the present invention. This indicates that the solid slow-release material in the raw materials of the present invention achieved a good fertilizer slow-release effect, with a longer fertilizer effect, improved fertilizer utilization, and a significant increase in wheat yield. However, changing the proportion of any component in the solid slow-release material or the preparation method weakens the corresponding effect. This shows that the raw materials of the present invention complement each other and are indispensable.

[0217] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A long-acting compound fertilizer, characterized in that, It is made from the following raw materials in parts by weight: 40-60 parts urea, 20-30 parts diammonium phosphate, 30-40 parts potassium chloride, 80-100 parts solid slow-release material, 15-25 parts humic acid, 6-10 parts carboxymethyl cellulose, and 300-400 parts water; wherein the solid slow-release material is composed of modified sepiolite powder and modified nanocellulose in a mass ratio of 2:

1. The modified sepiolite powder was prepared using the following method: (1) Add sepiolite powder to a 5wt% sulfuric acid solution according to the solid-liquid ratio, heat in a water bath to 80°C, react for 5-6 hours, filter, wash the filter residue with deionized water until neutral, dry in a vacuum drying oven and then pulverize to obtain acidified sepiolite powder. (2) Take 5g of acidified sepiolite powder and disperse it in 40ml of deionized water to obtain suspension A; (3) Take 1g of modified nano-hydroxyapatite and disperse it in 30ml of deionized water to obtain suspension B; (4) Add suspension A to suspension B to obtain a mixed solution, and adjust the pH of the mixed solution to 9-10 with NaOH. Maintain the mixed solution at 60-65℃ and stir magnetically for 1 hour. Cool to room temperature and stand for 24 hours. Filter and wash the filter residue with deionized water until neutral. Place it in a freeze dryer at -20℃ for 24 hours and grind it into powder to obtain modified sepiolite powder. The modified nanocellulose was prepared using the following method: S1: Add lignocellulose to a 1wt% hydrochloric acid solution at a solid-liquid ratio of 1g:10ml, heat to 80℃, and react for 1 hour under magnetic stirring. After the reaction is complete, filter and dry to obtain nanocellulose. S2: Mix nitric acid triacetic acid, N,N-dimethylamide and pyridine, add an appropriate amount of acetic anhydride, heat to 75°C under a nitrogen atmosphere, and stir magnetically for 10-15 hours to obtain mixture A; S3: Mix nanocellulose, mixture A and N,N-dimethylamide evenly, continue heating to 75°C under nitrogen atmosphere, and magnetically stir the reaction for 10-15 hours. After the reaction is completed, filter the mixture, and wash the solid product three times in sequence with deionized water, saturated sodium bicarbonate solution and acetone, and then vacuum dry to obtain modified nanocellulose. The method for preparing modified nano-hydroxyapatite in step (3) is as follows: (a) Take 5g of nano-hydroxyapatite and disperse it in 50ml of deionized water to form suspension I; (b) Take epoxidized soybean oil and slowly add it to 0.1 mol / L NaOH solution according to the material-to-liquid ratio. Stir the reaction at room temperature for 2-3 hours to obtain mixture II; (c) Slowly add suspension I to mixture II, and adjust the pH of the mixture to 9-10 with 0.1 mol / L NaOH. Heat the mixture in a water bath to 60°C, stir for 30-40 min, cool to room temperature and let stand for 24 h. Filter and wash the residue with deionized water until neutral. Place it in a freeze dryer and dry at -20°C for 24 h. Grind it into powder to obtain modified nano hydroxyapatite.

2. The long-acting compound fertilizer according to claim 1, characterized in that, In step (1), the solid-liquid ratio is 1g:10ml.

3. The long-acting compound fertilizer according to claim 1, characterized in that, In step (b), the ratio of epoxidized soybean oil to NaOH solution is 1g:100ml.

4. The long-acting compound fertilizer according to claim 1, characterized in that, In step (c), the volume ratio of suspension I to mixture II is 1:

2.

5. The long-acting compound fertilizer according to claim 1, characterized in that, In step S2, the mass ratio of nitroglycerin, N,N-dimethylamide, pyridine, and acetic anhydride is 1:1.5-2:1.5-1.6:1-1.

2.

6. The long-acting compound fertilizer according to claim 1, characterized in that, In step S3, the ratio of nanocellulose, mixture A, and N,N-dimethylamide is 1g:15ml:3-5ml.

7. A method for preparing a long-acting compound fertilizer according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1: Prepare modified sepiolite powder and modified nanocellulose separately, and mix them evenly in proportion to obtain a solid sustained-release material; Step 2: Take urea, diammonium phosphate, potassium chloride and half the amount of water and mix them evenly to obtain a uniform fertilizer mixture; Step 3: Take the solid slow-release material obtained in Step 1, humic acid, and the other half of the water and mix them evenly to obtain a suspension; Step 4: Mix the above fertilizer mixture with the suspension and add the cross-linking agent carboxymethyl cellulose. Stir at 150-200 rpm for 1 hour at room temperature. Dry the resulting mixture until the moisture content is less than 10%. Then granulate it with a granulator to obtain granular fertilizer. Finally, dry the granular fertilizer at 60℃ for 2 hours to obtain long-acting compound fertilizer.

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