A special stable fertilizer for rape based on moringa secondary metabolites, and a preparation method and application thereof

Abstract

The application provides a special rapeseed fertilizer based on moringa secondary metabolites, and a preparation method and application thereof, and belongs to the technical field of fertilizers.The fertilizer is composed of a fertilizer core and a moringa oil coating layer;raw materials of the fertilizer core include: 280-400 parts of urea, 90-170 parts of monoammonium phosphate, 240-300 parts of potassium sulfate, 50-80 parts of humic acid, 14-20 parts of borax, 85-290 parts of bentonite and 9-24 parts of moringa seed extract-biochar composite nitrification inhibitor particles;raw materials of the moringa oil coating layer include: 1-3 parts of moringa oil and 1-3 parts of paraffin wax.The moringa seed extract-biochar composite nitrification inhibitor particles and the moringa oil coating are used to construct a double inhibition system, and the two components have a synergistic effect, inhibit the nitrification in the soil, improve the nitrogen utilization rate, have the characteristics of environmental protection, no residue and easy decomposition of microorganisms, and can significantly improve the rapeseed yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fertilizers, in particular to a special rapeseed fertilizer based on secondary metabolites of Moringa oleifera and a preparation method and application thereof. BACKGROUND

[0002] Rapeseed is an important oil crop. With the expansion of rapeseed planting area and the increasing demand for rapeseed yield and quality, it is of great significance to develop efficient, environmentally friendly and targeted special rapeseed fertilizer. Nitrogen fertilizer application is one of the important measures to increase yield in rapeseed production. Farmers meet the demand of rapeseed for nitrogen by applying a large amount of nitrogen fertilizer. However, the yield of rapeseed does not increase with the increase of the amount of nitrogen fertilizer. Instead, the applied nitrogen fertilizer is lost through leaching, runoff, volatilization, nitrification-denitrification and other ways, resulting in low nitrogen fertilizer utilization rate. At the same time, the large-scale application of traditional fertilizers is easy to cause soil compaction, salinization, damage to soil structure, reduction of soil fertility and environmental pollution, which is not conducive to the sustainable development of agriculture. In addition, conventional fertilization cannot meet the comprehensive demand of rapeseed for nutrients at different growth stages, and lacks targeted nutrient supply, which is easy to cause nutrient deficiency or excess of rapeseed at some growth stages, thereby affecting the growth and development of rapeseed and quality indicators such as oil yield. Therefore, it is of great practical significance to develop a special rapeseed fertilizer to solve the existing rapeseed fertilization problems and promote the sustainable development of rapeseed industry. SUMMARY

[0003] In order to solve the problems in the prior art, the purpose of the present application is to provide a special rapeseed fertilizer based on secondary metabolites of Moringa oleifera, which uses Moringa oleifera seed extract-biochar composite to construct a biological nitrification inhibitor, and combines with Moringa oleifera oil-containing coating to synergistically inhibit the soil nitrification process, thereby stably improving the nitrogen utilization rate while reducing the potential environmental threat, and significantly improving the yield of rapeseed.

[0004] The purpose of the present application is also to provide a preparation method and application of the special rapeseed fertilizer based on secondary metabolites of Moringa oleifera.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0006] The present application provides a special rapeseed fertilizer based on secondary metabolites of Moringa oleifera, which is composed of a fertilizer core and a Moringa oleifera oil coating layer.

[0007] The raw materials of the fertilizer core include, by weight: urea 280-400 parts, monoammonium phosphate 90-170 parts, potassium sulfate 240-300 parts, humic acid 50-80 parts, borax 14-20 parts, bentonite 85-290 parts, and Moringa oleifera seed extract-biochar composite nitrification inhibitor particles 9-24 parts.

[0008] The raw materials of the moringa oil coating layer include 1-3 parts of moringa oil and 1-3 parts of paraffin by weight.

[0009] Preferably, the preparation method of the moringa seed extract-biochar composite nitrification inhibitor particles comprises the following steps:

[0010] The biochar is soaked in 5% dilute hydrochloric acid, then rinsed to neutral, dried, crushed and sieved to obtain biochar powder; the moringa seed extract is mixed with the biochar powder, a binder is added, and the mixture is stirred uniformly and dried to obtain the moringa seed extract-biochar composite nitrification inhibitor particles.

[0011] Preferably, the biochar includes any one or both of coconut shell charcoal and rice husk charcoal.

[0012] Preferably, the particle size of the biochar powder is 100-200 mesh.

[0013] Preferably, the phenol content of the moringa seed extract is ≥15%.

[0014] Preferably, the preparation method of the moringa seed extract comprises the following steps:

[0015] The moringa seeds are crushed and sieved, the moringa seed powder is mixed with n-hexane at a ratio of 1g:8-12mL, magnetic stirring is performed for 1-2h, ventilation is performed to volatilize the n-hexane, then 70% ethanol solution is added at a ratio of 1g:10-15mL, ultrasonic extraction is performed for 0.5-3h, filtration is performed, and concentration is performed to obtain the extract.

[0016] Preferably, the ultrasonic conditions are a temperature of 40-60℃, a power of 200-400W, and a frequency of 20-40kHz.

[0017] Preferably, the binder is 1% sodium alginate solution.

[0018] The application also provides a preparation method of the above-mentioned special rapeseed fertilizer based on moringa secondary metabolites, which comprises the following steps:

[0019] Borax and bentonite are mixed, then urea, monoammonium phosphate, potassium sulfate, humic acid, and moringa seed extract-biochar composite nitrification inhibitor particles are sequentially added and uniformly mixed, polyvinyl alcohol is added as a binder, and granulation is performed to obtain a fertilizer core.

[0020] Moringa oil and paraffin are mixed, then sprayed on the surface of the fertilizer core to form a coating, and low-temperature drying is performed to obtain the special rapeseed fertilizer based on moringa secondary metabolites.

[0021] The application also provides application of the above-mentioned special rapeseed fertilizer based on moringa secondary metabolites in improving rapeseed yield.

[0022] Compared with the prior art, the technical scheme of the present application has the following beneficial effects:

[0023] The rapeseed special stable fertilizer based on moringa secondary metabolites provided by the present application adopts moringa seed extract-biochar composite nitrification inhibitor particles and moringa oil coating to construct a double inhibition system, and the two have a synergistic effect to inhibit nitrification in the soil, improve the utilization rate of nitrogen fertilizer, reduce environmental pollution, and can significantly improve the yield of rapeseed.

[0024] Nitrification is mainly mediated by AOB in neutral and alkaline soils, while AOA plays a leading role in this process in acid soils. The moringa seed extract-biochar composite nitrification inhibitor particles and moringa oil coating in the rapeseed special stable fertilizer can simultaneously inhibit the growth of AOA and AOB, thereby inhibiting nitrification, especially in acid soils. The present application has great potential in inhibiting the nitrification process, and compared with chemically synthesized nitrification inhibitors, it has the characteristics of greenness, naturalness and easy biodegradability, which meets the demand for green and sustainable development of agriculture. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 : Ammonium nitrogen content of each group of soil;

[0026] Figure 2 : AOB and AOA gene abundance of each group of soil, a figure is AOB gene abundance, and b figure is AOA gene abundance. DETAILED DESCRIPTION

[0027] The present application provides a rapeseed special stable fertilizer based on moringa secondary metabolites, which is composed of a fertilizer core and a moringa oil coating layer.

[0028] By weight, the raw materials of the fertilizer core include: urea 280-400 parts, monoammonium phosphate 90-170 parts, potassium sulfate 240-300 parts, humic acid 50-80 parts, borax 14-20 parts, bentonite 85-290 parts, and moringa seed extract-biochar composite nitrification inhibitor particles 9-24 parts; preferably including urea 300-350 parts, monoammonium phosphate 120-150 parts, potassium sulfate 260-280 parts, humic acid 60-70 parts, borax 16-18 parts, bentonite 150-200 parts, and moringa seed extract-biochar composite nitrification inhibitor particles 12-20 parts; by weight, the raw materials of the moringa oil coating layer include: 1-3 parts of moringa oil and 1-3 parts of paraffin wax, preferably including 2 parts of moringa oil and 2 parts of paraffin wax. The paraffin wax has a melting point of 50-55℃.

[0029] The preparation method of the moringa seed extract-biochar composite nitrification inhibitor particle comprises the following steps: the biochar is soaked in 5% dilute hydrochloric acid, then rinsed to neutral, dried, crushed and sieved to obtain biochar powder; the moringa seed extract is mixed with the biochar powder, a binder is added, and then stirred uniformly and dried to obtain the moringa seed extract-biochar composite nitrification inhibitor particle.

[0030] The 5% dilute hydrochloric acid refers to a hydrochloric acid aqueous solution with a mass concentration of 5%. In the present application, the biochar is soaked in 5% dilute hydrochloric acid for 1-3 h to remove free ash and inorganic impurities. After soaking in dilute hydrochloric acid, the biochar is rinsed with deionized water until neutral, dried, crushed and sieved; the drying temperature is preferably 60-80 DEG C, the time is preferably 4-8 h, and the drying is preferably performed until the moisture content of the biochar is less than 5%; the particle size of the sieved biochar powder is preferably 100-200 meshes. The biochar in the present application preferably includes any one or both of coconut shell charcoal and rice husk charcoal.

[0031] The moringa seed extract and the biochar powder are preferably mixed at a mass ratio of 1:1-4, and more preferably at a mass ratio of 1:2-3; the binder is preferably 1% sodium alginate solution, and the 1% sodium alginate solution refers to a sodium alginate aqueous solution with a mass concentration of 1%. Based on the mass of the moringa seed extract-biochar composite nitrification inhibitor particle, the mass of the binder is preferably 3%-8%, and more preferably 5%. After adding the binder, the mixture is stirred uniformly and dried, the drying temperature is preferably 50-70 DEG C, and the drying temperature is more preferably 60 DEG C, and the drying is preferably performed until the moisture content is 5%-8%; the particle size of the moringa seed extract-biochar composite nitrification inhibitor particle prepared in the present application is preferably 0.5-1 mm.

[0032] The phenol content of the moringa seed extract is greater than or equal to 15%, and preferably 15%-25%. The preparation method of the moringa seed extract comprises the following steps: the moringa seeds are crushed and sieved, the moringa seed powder is mixed with n-hexane at a ratio of 1g:8-12 mL, magnetically stirred for 1-2 h, ventilated to volatilize the n-hexane, then 70% ethanol solution is added at a ratio of 1g:10-15 mL, ultrasonic extraction is performed for 0.5-3 h, and then filtration, concentration and extraction are performed to obtain the extract.

[0033] The moringa seed of the present application is preferably crushed through a 40-80 mesh sieve, and the mixing ratio of the moringa seed powder and n-hexane is preferably 1g:9mL, 1g:10mL or 1g:11mL; the temperature of the magnetic stirring is preferably 20-45℃, more preferably 35℃, and the stirring speed is preferably 200-800rpm, more preferably 300-500rpm; the fat is removed by magnetic stirring, and then the n-hexane is volatilized in a fume hood to obtain defatted moringa seed powder; then the defatted moringa seed powder is added into 70% ethanol solution for ultrasonic extraction according to a material-liquid ratio of 1g:10-15mL, more preferably 1g:11mL, 1g:12mL, 1g:13mL or 1g:14mL, and the extraction temperature is preferably 60℃; the ultrasonic condition is a frequency of 10-40kHz, more preferably 20-25kHz; the ultrasonic extract is filtered and concentrated to obtain extract; the concentration method is preferably rotary evaporation or thin film evaporation under the conditions of 40-60℃ and a vacuum degree of ≤0.08Mpa, and the ethanol solvent is recovered, and the density of the extract is 1.05-1.2g / cm 3 .

[0034] The present application also provides a preparation method of the above-mentioned rapeseed special stable fertilizer based on moringa secondary metabolites, which comprises the following steps: mixing borax with bentonite, and then sequentially adding urea, monoammonium phosphate, potassium sulfate, humic acid, moringa seed extract-biochar composite nitrification inhibitor granules, mixing uniformly, adding polyvinyl alcohol as a binder, granulating to obtain a fertilizer core; mixing moringa oil with paraffin, and spraying on the surface of the fertilizer core to form a coating, and low-temperature drying to obtain the rapeseed special stable fertilizer based on moringa secondary metabolites.

[0035] The polyvinyl alcohol of the present application is preferably a 5% polyvinyl alcohol aqueous solution, and the addition amount of the 5% polyvinyl alcohol aqueous solution is preferably 2-5% of the mass of the fertilizer core; the low-temperature drying of the present application is preferably rapid reduction to room temperature through a cold air drum, and preferably drying to a water content of 3-5%; and the particle size of the fertilizer prepared by the present application is preferably 1-5mm.

[0036] The present application also provides the application of the above-mentioned rapeseed special stable fertilizer based on moringa secondary metabolites in improving the yield of rapeseed.

[0037] Nitrification to form nitrate nitrogen is the main way of nitrogen loss. Nitrification inhibitors can control soil nitrification process by inhibiting ammonia oxidation, thereby delaying the generation of nitrate nitrogen and reducing N2O emissions. Chemical nitrification inhibitors, including dicyandiamide (DCD), 3,4-dimethylpyrazole phosphate (DMPP) and 2-chloro-6-(trichloromethyl)pyridine (CP), are widely used in agricultural planting. However, these chemicals have the disadvantages of short action time, food contamination risk and potential environmental threat. The present application uses moringa seed extract-biochar composite to construct biological nitrification inhibitor, and combines with moringa oil-containing coating to synergistically inhibit soil nitrification process, which can significantly improve the yield of rapeseed while achieving stable improvement of nitrogen utilization rate and reducing potential environmental threat.

[0038] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] In specific embodiments of the present application, moringa seeds are purchased from Honghe Valley Moringa Industry Co., Ltd., and moringa oil is purchased from Jiangxi Youshangao Spice Co., Ltd.

[0040] In the following examples, unless otherwise specified, all are conventional methods.

[0041] In the following examples, unless otherwise specified, all materials, reagents, etc. can be obtained from commercial channels.

[0042] Example 1

[0043] A special rapeseed stable fertilizer based on moringa seed secondary metabolites, the fertilizer comprising a fertilizer core and a moringa oil-containing coating, the preparation method comprising the following steps:

[0044] 1. Preparation of moringa seed extract-biochar composite nitrification inhibitor particles

[0045] S1: After drying the moringa seeds at 45℃, crush them through a 60 mesh sieve, mix the seed powder with n-hexane at 1g:10mL, and magnetically stir at room temperature (35℃) for 1 hour (at a speed of 400rpm), remove the fat, and let the n-hexane evaporate in a fume hood to obtain defatted moringa seed powder;

[0046] S2: Defatted Moringa oleifera seed powder was added to 70% ethanol at a material to liquid ratio of 1 g: 10 mL, and extracted at 60°C for 2 hours under ultrasonication (ultrasonication conditions: frequency 25 kHz, power density 40 W / L). After filtration, the ethanol was recovered by rotary evaporation under reduced pressure (water bath temperature 40°C, vacuum degree 80 mbar), and the extract was concentrated to obtain an extract (the density of the extract was 1.10 g / mL -1 );

[0047] S3: Coconut shell charcoal was soaked in 5% dilute hydrochloric acid (soaking time 2 h) to remove free ash and inorganic impurities, and then washed thoroughly with deionized water until neutral (pH 6.5-7.5). After drying (drying temperature 70°C, time 8 h, to a water content of ≤5%), the charcoal was ground to pass through a 200-mesh sieve to obtain a powder of uniform particle size;

[0048] S4: Moringa oleifera seed extract was mixed with biochar powder at a mass ratio of 1:2, and 5% by mass of a 1% sodium alginate solution was added as a binder. After stirring to uniformity, the mixture was slowly dried at 60°C to a water content of 6% to obtain Moringa oleifera seed extract-biochar composite nitrification inhibitor granules of particle size 0.5-1 mm.

[0049] 2. Preparation of the fertilizer core

[0050] Fourteen parts of borax were mixed with 91 parts of bentonite, and then 400 parts of urea, 133 parts of monoammonium phosphate, 300 parts of potassium sulfate, 60 parts of humic acid, and 9 parts of Moringa oleifera seed extract-biochar composite nitrification inhibitor granules were added and mixed uniformly. The mixture was then fed into a rotary drum granulator for granulation. During the granulation process, 3% by mass of a 5% polyvinyl alcohol aqueous solution was sprayed onto the surface of the material to promote particle bonding.

[0051] 3. Coating

[0052] Moringa oil was mixed with number 58 paraffin wax at a mass ratio of 1:1 to obtain a coating oil containing Moringa oil. The mass ratio of the composite coating material to the fertilizer core was 4%, and the composite coating material was uniformly sprayed onto the surface of the fertilizer core in a fluidized bed. The fluidized hot air accelerated the film formation. The coated particles were rapidly cooled to room temperature (dried to a water content of 4%) by a cold air roller. Non-standard particles with a particle size of less than 1 mm and more than 5 mm were removed by a multi-stage vibrating screen classifier to obtain a rapeseed special-purpose stability fertilizer based on Moringa oleifera secondary metabolites.

[0053] Example 2

[0054] A rapeseed special-purpose stability fertilizer based on Moringa oleifera seed secondary metabolites, the fertilizer comprising a fertilizer core and a Moringa oil-containing coating, the preparation method comprising the following steps:

[0055] 1. Preparation of Moringa oleifera seed extract-biochar composite nitrification inhibitor granules

[0056] S1: After drying the Moringa oleifera seeds at 45℃, the seeds were ground to pass through a 60 mesh sieve. The seed powder was mixed with n-hexane at a ratio of 1 g:10 mL and stirred magnetically at room temperature (35℃) for 1 hour (400 rpm). The fat was removed and the n-hexane was allowed to evaporate in a fume hood to obtain defatted Moringa oleifera seed powder;

[0057] S2: The defatted Moringa oleifera seed powder was mixed with 70% ethanol at a ratio of 1 g:10 mL and extracted ultrasonically at 60℃ for 2 hours (ultrasonic conditions: frequency 25 kHz, power density 40 W / L). After filtration, the ethanol was recovered by rotary evaporation under reduced pressure (water bath temperature 40℃, vacuum degree 80 mbar) and the extract was obtained (the density of the extract was 1.10 g / mL -1 );

[0058] S3: The coconut shell charcoal was soaked in 5% dilute hydrochloric acid (soaking time 2 h) to remove free ash and inorganic impurities. Then, the charcoal was washed thoroughly with deionized water until neutral (pH 6.5-7.5) and dried (drying temperature 70℃, time 8 h, water content ≤5%) before being ground to pass through a 200 mesh sieve to obtain a uniform powder of the biochar;

[0059] S4: The Moringa oleifera seed extract was mixed with the biochar powder at a ratio of 1:2, and 5% 1% sodium alginate solution was added as a binder. After stirring, the mixture was slowly dried at 60℃ until the water content was 6% to obtain Moringa oleifera seed extract-biochar composite nitrification inhibitor particles with a particle size of 0.5-1 mm.

[0060] 2. Preparation of the fertilizer core

[0061] The 14 parts of borax and 85 parts of bentonite were mixed, and then 400 parts of urea, 133 parts of monoammonium phosphate, 300 parts of potassium sulfate, 60 parts of humic acid, and 15 parts of Moringa oleifera seed extract-biochar composite nitrification inhibitor particles were added and mixed uniformly. The mixture was then fed into a rotary drum granulator for granulation. During the granulation process, 3% of a 5% polyvinyl alcohol solution was sprayed onto the surface of the material to promote particle bonding.

[0062] 3. Coating

[0063] Moringa oil was mixed with number 58 paraffin wax at a ratio of 1:1 to obtain a coating oil containing Moringa oil. The coating material was uniformly sprayed onto the surface of the fertilizer core in a fluidized bed at a ratio of 4%. The fluidized hot air accelerated the film formation. The coated particles were rapidly cooled to room temperature (dried to a water content of 4%) by a cold air roller. Non-standard particles with a particle size less than 1 mm and greater than 5 mm were removed by a multi-stage vibrating screen separator to obtain a rapeseed-specific stable fertilizer based on Moringa secondary metabolites.

[0064] Example 3

[0065] A special oilseed rape fertilizer based on secondary metabolites of Moringa oleifera seeds, said fertilizer comprising a fertilizer core and a coating comprising Moringa oil, the method of preparation comprising the following steps:

[0066] 1. Preparing Moringa oleifera seed extract-biochar composite nitrification inhibitor granules

[0067] S1: After drying the Moringa oleifera seeds at 45°C, the seeds were ground to pass through a 60-mesh sieve. The seed powder was mixed with n-hexane at a ratio of 1 g:10 mL and stirred magnetically at room temperature (35°C) for 1 hour at a speed of 400 rpm. The n-hexane was allowed to evaporate in a fume hood, and defatted Moringa oleifera seed powder was obtained.

[0068] S2: The defatted Moringa oleifera seed powder was added to 70% ethanol at a ratio of 1 g:10 mL. The mixture was ultrasonicated at 60°C for 2 hours (ultrasonic conditions: frequency 25 kHz, power density 40 W / L). After filtration, the ethanol was recovered by rotary evaporation under reduced pressure (water bath temperature 40°C, vacuum degree 80 mbar), and an extract was obtained (the density of the extract was 1.10 g / mL -1 );

[0069] S3: The coconut shell charcoal was soaked in 5% dilute hydrochloric acid for 2 hours to remove free ash and inorganic impurities. Then, the charcoal was washed with deionized water until it was neutral (pH 6.5-7.5). After drying (drying temperature 70°C, time 8 hours, until the water content was ≤5%), the charcoal was ground to pass through a 200-mesh sieve, and a powder of uniform particle size was obtained.

[0070] S4: The Moringa oleifera seed extract was mixed with the biochar powder at a ratio of 1:2. A 5% solution of 1% sodium alginate was added as a binder at a mass fraction of 5%. After stirring, the mixture was slowly dried at 60°C until the water content was 6%, and granular Moringa oleifera seed extract-biochar composite nitrification inhibitor granules with a particle size of 0.5-1 mm were obtained.

[0071] 2. Preparing the fertilizer core

[0072] Fourteen parts of borax were mixed with 85 parts of bentonite. Then, 400 parts of urea, 133 parts of monoammonium phosphate, 300 parts of potassium sulfate, 60 parts of humic acid, and 21 parts of Moringa oleifera seed extract-biochar composite nitrification inhibitor granules were added and mixed uniformly. The mixture was fed into a rotary drum granulator. During the granulation process, a 5% polyvinyl alcohol solution was sprayed onto the surface of the mixture at a mass ratio of 3% to promote particle bonding.

[0073] 3. Coating

[0074] The moringa oil is mixed with the No. 58 paraffin wax at a mass ratio of 1:1 to obtain a moringa oil coated oil. The mass ratio of the composite coating material is 4% and is uniformly sprayed on the surface of the fertilizer core in a fluidized bed. The fluidized hot air accelerates the film formation. The coated particles are rapidly cooled to room temperature (dried to a moisture content of 4%) by a cold air roller. Non-standard particles with a particle size of less than 1 mm and greater than 5 mm are removed by a multi-stage vibrating screen separator to obtain a rapeseed special-purpose stability fertilizer based on moringa secondary metabolites.

[0075] Example 4

[0076] A rapeseed special-purpose stability fertilizer based on moringa secondary metabolites, the fertilizer comprising a fertilizer core and a moringa oil coating, the preparation method comprising the following steps:

[0077] 1. Preparation of moringa seed extract-biochar composite nitrification inhibitor particles

[0078] S1: After drying the moringa seeds at 45°C, the seeds are crushed to pass through an 80-mesh sieve. The seed powder is mixed with n-hexane at a ratio of 1 g:10 mL and stirred magnetically at room temperature (35°C) for 1 hour (at a speed of 400 rpm). The n-hexane is allowed to evaporate in a fume hood to obtain defatted moringa seed powder;

[0079] S2: The defatted moringa seed powder is added to 70% ethanol at a solid-liquid ratio of 1 g:10 mL. Ultrasonic extraction is performed at 60°C (ultrasonic conditions: frequency 25 kHz, power density 40 W / L) for 3 hours. After filtration, the ethanol is recovered by rotary evaporation under reduced pressure (water bath temperature 40°C, vacuum degree 80 mbar) and the extract is obtained (the density of the extract is 1.10 g / mL -1 );

[0080] S3: The rice husk charcoal is soaked in 5% dilute hydrochloric acid (soaking time 2 h) to remove free ash and inorganic impurities. It is then washed thoroughly with deionized water until neutral (pH 6.5-7.5). After drying (drying temperature 70°C, time 8 h, moisture content ≤5%), the rice husk charcoal is crushed to pass through a 200-mesh sieve to obtain a powder of uniform particle size;

[0081] S4: The moringa seed extract and the biochar powder are mixed at a mass ratio of 1:2. A 5% solution of 1% sodium alginate is added as a binder. After stirring uniformly, the mixture is slowly dried at 60°C until the moisture content is 6% to obtain moringa seed extract-biochar composite nitrification inhibitor particles with a particle size of 0.5-1 mm.

[0082] 2. Preparation of a fertilizer core

[0083] Mix 18 parts of borax with 166 parts of bentonite, then add 320 parts of urea, 130 parts of monoammonium phosphate, 280 parts of potassium sulfate, 80 parts of humic acid, and 9 parts of moringa seed extract-biochar composite nitrification inhibitor granules, mix uniformly, and then send to a drum granulator for granulation. In the granulation process, spray 3% of 5% polyvinyl alcohol aqueous solution on the surface of the material to promote particle bonding.

[0084] 3, coating

[0085] Mix the moringa oil with the No. 58 paraffin wax at a mass ratio of 3:1 to obtain a coating oil containing moringa oil. In a fluidized bed, uniformly spray 4% of the composite coating material on the surface of the fertilizer core, accelerate film formation with fluidized hot air, and cool the coated particles to room temperature (dry to a moisture content of 4%) through a cold air roller. Remove non-standard particles with particle sizes less than 1 mm and greater than 5 mm through a multi-stage vibration screen separator to obtain a special rapeseed stability fertilizer based on moringa secondary metabolites.

[0086] Comparative Example 1

[0087] A special rapeseed stability fertilizer based on moringa secondary metabolites, which is different from Example 2 in that no moringa seed extract-biochar composite nitrification inhibitor granules are added to the fertilizer core.

[0088] Comparative Example 2

[0089] A special rapeseed stability fertilizer based on moringa secondary metabolites, which is different from Example 2 in that it is not coated with a coating liquid containing moringa oil, but only coated with paraffin wax, and the others are the same as Example 2.

[0090] Comparative Example 3

[0091] A special rapeseed stability fertilizer based on moringa secondary metabolites, which is different from Example 2 in that the fertilizer core is replaced with 0.6 parts of 3,4-dimethylpyrazole phosphate (DMPP) instead of moringa seed extract-biochar composite nitrification inhibitor granules, and only coated with paraffin wax, and the others are the same as Example 2.

[0092] Comparative Example 4

[0093] A general rapeseed special fertilizer, which is different from Example 2 in that no moringa seed extract-biochar composite nitrification inhibitor granules are added to the fertilizer core, and only coated with paraffin wax, and the others are the same as Example 2.

[0094] Test Example

[0095] Test site: Zhilingpu Town, Dongbao District, Jingmen City, Hubei Province; the soil nutrient content of the test is: organic matter 3.67%, alkali hydrolysis nitrogen 128.9 mg / kg, available phosphorus (P2O5) 29.5 mg / kg, available potassium (K2O) 324.9 mg / kg, and the soil pH value is 7.32; the test rape variety is Huayouzha 50.

[0096] Experimental design: 8 treatments are set in this experiment, each treatment is repeated 3 times, arranged randomly in groups, and the test plot area is 20 m 2 (10 m x 2 m), and 1 m wide protection lines are set around the test field. The fertilizer amount is 750 kg / hm 2 , all fertilizers are applied as base fertilizer at one time. The planting method is direct seeding, sowing on October 10, 2024, and harvesting on May 8, 2025, and other management measures are managed according to the conventional way in the field.

[0097] The ammonium nitrogen content in the soil of each group of rape at the seedling stage, bud stage, flowering stage and mature stage is determined by potassium chloride solution extraction-spectrophotometry (standard HJ 634-2012), and the abundance of AOA and AOB at the flowering stage is determined by real-time fluorescent quantitative PCR. The branch number, angle fruit number, grain number per angle fruit, thousand grain weight and rape yield at the mature stage are determined, and the results are shown in Figures 1-2 and Table 1.

[0098] Table 1: Rape yield and its constituent factors of each group

[0099]

[0100] As can be seen from Figure 1 , compared with Comparative Examples 1-2 and 4, the ammonium nitrogen content in the soil of the rape of the fertilizer treatment of Examples 1-4 is higher than that of other treatments, which indicates that Examples 1-4 have a good inhibitory effect on the process of soil ammonium nitrogen to nitrate nitrogen, and the effect is comparable to that of chemical inhibitors.

[0101] As can be seen from Figure 2 , compared with Comparative Examples 1-2 and 4, the AOA and AOB gene abundance of the fertilizer treatment of Examples 1-4 is significantly reduced, which indicates that Examples 1-4 significantly inhibit the microbial activity related to the soil nitrification process.

[0102] As can be seen from Table 1, the rape yield of Examples 1-4 is increased by 6.7%-14.5%, and the yield-increasing effect is better than that of Comparative Examples 1-2.

[0103] The above is only the preferred embodiment of the present application, it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A stable specialty fertilizer for Brassica based on a secondary metabolite of Moringa oleifera characterized in that, The fertilizer is composed of a fertilizer core and a moringa oil coating layer; The raw materials of the fertilizer core include, in parts by weight, urea 280-400 parts, monoammonium phosphate 90-170 parts, potassium sulfate 240-300 parts, humic acid 50-80 parts, borax 14-20 parts, bentonite 85-290 parts, and moringa seed extract-biochar composite nitrification inhibitor granules 9-24 parts; The raw materials of the moringa oil coating layer include, in parts by weight, moringa oil 1-3 parts and paraffin 1-3 parts; The preparation method of the moringa seed extract-biochar composite nitrification inhibitor granules comprises the following steps: soaking biochar in 5% dilute hydrochloric acid, then rinsing to neutral, drying, and then crushing and sieving to obtain biochar powder; mixing the biochar powder with moringa seed extract, adding a binder, stirring uniformly, and then drying to obtain moringa seed extract-biochar composite nitrification inhibitor granules; The biochar includes any one or both of coconut shell charcoal and rice husk charcoal. The preparation method of the moringa seed extract comprises the following steps: crushing and sieving moringa seeds, mixing the moringa seed powder with n-hexane at a ratio of 1g:8-12mL, magnetically stirring for 1-2h, ventilating to volatilize the n-hexane, then adding 70% ethanol solution at a ratio of 1g:10-15mL, ultrasonic extraction for 0.5-3h, filtering, and then concentrating to obtain an extract; The binder is 1% sodium alginate solution. The preparation method of the moringa secondary metabolite-based special rapeseed fertilizer with stability comprises the following steps: Mixing borax with bentonite, then adding urea, monoammonium phosphate, potassium sulfate, humic acid, and moringa seed extract-biochar composite nitrification inhibitor granules in sequence, mixing uniformly, adding polyvinyl alcohol as a binder, granulating to obtain a fertilizer core, mixing moringa oil with paraffin, and then spraying on the surface of the fertilizer core to form a coating, and low-temperature drying to obtain the moringa secondary metabolite-based special rapeseed fertilizer with stability.

2. The stable brassica specific biofertilizer based on moringa secondary metabolites as claimed in claim 1, wherein, The particle size of the biochar powder is 100-200 mesh.

3. The stable brassica specific biofertilizer based on moringa secondary metabolites as claimed in claim 1, wherein, The phenol content of the moringa seed extract is ≥15%.

4. The stable brassica specific biofertilizer based on moringa secondary metabolites as claimed in claim 1, wherein, The ultrasonic conditions are a temperature of 40-60℃, a power of 200-400W, and a frequency of 20-40kHz.

5. Application of the moringa secondary metabolite-based special rapeseed fertilizer with stability in improving rapeseed yield according to any one of claims 1-4.

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