Special compound fertilizer for citrus crops in fruit swelling period and preparation method of special compound fertilizer

Abstract

The invention discloses a special compound fertilizer for citrus crops in a fruit swelling period and a preparation method thereof, and belongs to the technical field of compound fertilizers. Comprising a water-soluble fertilizer and a nitrogen-phosphorus-potassium fertilizer, wherein the water-soluble fertilizer comprises concentrated biogas slurry, EDTA (Ethylene Diamine Tetraacetic Acid), peregal, streptomycin and a preservative; the concentrated biogas slurry is obtained by concentrating biogas slurry by 6-8 times through a reverse osmosis concentration membrane; the mass ratio of the nitrogen-phosphorus-potassium fertilizer to the water-soluble fertilizer is 1: (5-12); the mass ratio of the peregal to the EDTA to the concentrated biogas slurry is (0.2-1.0): (25-35): 1000; the dosage of the preservative is 0.1-0.5% of the weight of the concentrated biogas slurry, and the dosage of the streptomycin is 0.1-0.5% of the weight of the nitrogen-phosphorus-potassium fertilizer; the nitrogen-phosphorus-potassium fertilizer comprises the following nutrients: 14% < N < 16%, 4.5% < P2O5 < 5.5% and 23% < K2O < 27%; when in use, the water-soluble fertilizer and the nitrogen-phosphorus-potassium fertilizer are mixed, diluted by 50-150 times and then sprayed.

Description

Technical Field

[0001] The invention belongs to the technical field of compound fertilizers, and in particular relates to a special compound fertilizer for citrus crops during the fruit-swelling period and a preparation method thereof. Background Art

[0002] my country is a major producer of citrus, boasting a long history of cultivation and abundant citrus resources and high-quality varieties, earning it the title of "World Citrus Treasure House." Since the 20th century, my country's citrus industry has experienced rapid growth, ranking first in both global planting area and production. Currently, a lack of fertilizers and inappropriate farming practices have led to a significant imbalance in nutrients in the soil and crops, severely impacting citrus production and quality. Therefore, efficient and effective fertilization has become a crucial approach to achieving high yields and high quality in citrus.

[0003] Macronutrients contribute 90% to crop yield, while trace elements contribute over 90% to crop quality. Different crops have varying nutrient requirements. Traditional fertilization methods often involve farmers using only one type or category of fertilizer, leading to a serious imbalance in nutrient levels in citrus crops. Long-term use can be extremely harmful to the trees. Statistics show that 100% of my country's citrus-growing areas currently experience nutritional imbalances in citrus crops, with widespread deficiencies in trace elements such as Ca, Fe, and Zn, and excesses in macronutrients such as P. This leads to a series of problems, including frequent citrus diseases, low yields, flower and fruit drop, bland fruit flavor, and a serious decline in fruit quality.

[0004] Many citrus fertilizers are disclosed in the prior art. For example, patent application number CN201210449361.5 discloses a composite water-soluble fertilizer specifically for citrus crops. The preparation steps of the composite water-soluble fertilizer are as follows: (1) Preparation of mother liquor: 250-350 parts of amino acid raw materials and 200-400 parts of solution, stir and shake to prepare an amino acid mother liquor with a pH of 2-5.

[0005] (2) Chelating reaction 1: Add 5-25 parts of pH regulator at room temperature (15°C-35°C), stir until well-mixed, and adjust the pH value of the solution to 3-7. Then, add 30-60 parts of manganese sulfate, copper sulfate, and ferrous sulfate to the mother liquor obtained in step (1), and stir for 1-5 hours. The manganese, copper, and iron chelation is completed.

[0006] (3) Chelating reaction 2: Add 5-25 parts of pH regulator at room temperature (15°C-35°C) and stir continuously until the solution is evenly mixed to adjust the pH value of the solution to 6-10. Then, add 130-260 parts of calcium nitrate, magnesium sulfate and zinc sulfate to the solution obtained in step (2) and stir for 1-5 hours to complete the reaction.

[0007] (4) Adding the remaining elements: add 30-50 parts of potassium dihydrogen phosphate to the solution obtained in step (3), and finally add 50-120 parts of boron raw material and ammonium molybdate and 1-20 parts of silicon dioxide, and stir for 0.1-2 hours.

[0008] (5) Adding auxiliary agents: adding 30-80 parts of auxiliary agents to the solution obtained in step (4), stirring for 0.1-2 hours, filtering, and forming the product; wherein the auxiliary agents include a dispersant, a wetting agent, an osmotic diffuser, and a preservative, the dispersant is calcium lignin sulfonate, the wetting agent is glycerol, the osmotic diffuser is ethoxy-modified trisiloxane, and the preservative is potassium sorbate; the weight ratio of each component of the auxiliary agent to the weight of the water-soluble fertilizer is: the dispersant calcium lignin sulfonate is 0.01-2%, the wetting agent glycerol is 0.01-2%, the osmotic diffuser ethoxy-modified trisiloxane is 2-6%, and the preservative potassium sorbate is 0.1-0.5%.

[0009] For example, the patent application number CN201410832638.1 discloses a high-content water-soluble fertilizer for citrus, which uses phosphorus oxyamide as a nitrogen and phosphorus source, to which nanocarbon and enhancers are added, and its composition is the following substances by weight ratio: phosphorus oxyamide: 20%-40%, potassium nitrate: 20%-40%, nanocarbon: 5%-10%, sodium molybdate tetrahydrate: 5%-10%, sodium borate: 1%-5%, chelated zinc: 1%-5%, enhancer: 1%-5%, chelated iron: 0.1%-0.5%, chelated Copper: 0.1%-0.5%, rare earth compound: 0.01%-0.05%, wherein the phosphorus oxyamide has a molecular formula of PO(NH2)3, a molecular weight of 95, and a total nitrogen and phosphorus content of 92%-94%, of which the nitrogen content is 31%-33% and the phosphorus content (P2O5) is 61%-63%; wherein the enhancer is a combination of the following substances: sorbitan, silicone, and water-soluble acrylic acid, and the addition ratio is sorbitan: silicone: water-soluble acrylic acid = 1:1-3:1-2; wherein the silicone is an anionic siloxane with a molecular weight of 1500-3000; wherein the acrylic acid is any one of the following substances: polyacrylamide, polyacrylic acid, and polymethacrylic acid.

[0010] It can be seen from the above patents that in order to improve the effect, various trace elements, more chelating agents and more enhancers need to be added to special fertilizers, which results in high costs. Summary of the Invention

[0011] This patent provides a special compound fertilizer for citrus crops during the fruit-swelling period and its preparation method. It not only turns waste into treasure (consumes biogas slurry), thereby reducing costs; at the same time, it adds 15-5-25 compound fertilizer and ammonium molybdate to meet the growth needs of citrus, eliminating the need to add trace elements or synergists, and only requiring a small amount of insecticide (streptomycin). This reduces costs and is simple to prepare. The technical solution is as follows: On the one hand, an embodiment of the present invention provides a special compound fertilizer for citrus crops during the fruit-swelling period, including water-soluble fertilizers and nitrogen, phosphorus and potassium fertilizers. Among them, the water-soluble fertilizers include concentrated biogas slurry, EDTA, peregrine, streptomycin and preservatives. Concentrated biogas slurry is obtained by concentrating biogas slurry 6-8 times through a reverse osmosis concentration membrane. The mass ratio of nitrogen, phosphorus and potassium fertilizers to water-soluble fertilizers is 1:5-12; the mass ratio of peregrine, EDTA and concentrated biogas slurry is 0.2-1.0:25-35:1000. The amount of streptomycin used is 1-5‰ of the weight of nitrogen, phosphorus and potassium fertilizers. The amount of preservative used is 0.1-0.5% of the weight of concentrated biogas slurry to prevent the concentrated biogas slurry from deteriorating and becoming smelly. The preservative is selected from potassium sorbate or potassium benzoate, etc.

[0012] Concentrated biogas slurry contains a small amount of organic matter (including nitrogen, phosphorus, and potassium), a relatively high concentration of trace elements, amino acids, and humic acid, as well as trace amounts of active substances such as butyric acid, gibberellins, auxins, and vitamins. These substances have multiple benefits: first, promoting crop growth; second, improving disease and stress resistance; third, inhibiting deterioration (when macromolecular organic matter is separated); and fourth, improving the quality of citrus fruits. Concentrated biogas slurry itself is a fast-acting water-soluble fertilizer. Testing has shown that the water-soluble fertilizer does not deteriorate, develop odor, or exhibit noticeable precipitation when stored sealed at room temperature for six months.

[0013] In concentrated biogas slurry, the phosphorus content is 4-5 times higher than before concentration, increasing rapidly after 1-3 times concentration, then slowly increasing, and rapidly increasing after 8 times concentration. The potassium content is 4-5 times higher than before concentration, decreasing slightly after 7 times concentration (potassium concentration in the permeate increases rapidly starting from 7 times concentration). The organic matter content is 3.5-4.0 times higher than before concentration, with organic matter appearing in the permeate starting after 8 times concentration. The electrical conductivity is 2-3 times higher than before concentration, and rapidly increases after 7 times concentration. The amino acid content is 2-3 times higher than before concentration. The humic acid content is 3.0-3.5 times higher than before concentration. The concentrate contains virtually no metal ions such as chromium, mercury, and arsenic. The above data demonstrate that nutrient content is high with minimal loss when concentrated to 6-8 times. Concentration facilitates transportation and storage.

[0014] EDTA acts as a chelating agent, working with humic acid and amino acids in concentrated biogas slurry to capture and release metal ions, enabling more complete absorption. Pingpingjia acts as a surfactant, promoting the adhesion and absorption of active ingredients on leaves and facilitating the dissolution of fertilizers.

[0015] Among them, the nutrients of nitrogen, phosphorus and potassium fertilizers are: 14%<N<16%, 4.5%<P2O5<5.5%, 23%<K2O<27%; when using, mix water-soluble fertilizers and nitrogen, phosphorus and potassium fertilizers and dilute them 50-150 times before spraying.

[0016] Specifically, the source of the biogas slurry is: a biogas tank from a pig farm, the fermentation temperature is 15-45°C, and the fermentation time is more than 3 months.

[0017] Among them, the parameters of concentrated biogas slurry are: P2O5 content is 0.20-0.30g / L, K2O content is 1.6-2.4g / L, N content is 4.4-6.0g / L, organic matter content is 2.2-3.5g / L, amino acid content is 0.15-0.28g / L, humic acid content is 6-12g / L, calcium ion content is 20-40mg / L, iron ion content is 25-42mg / L, zinc ion content is 15-27mg / L, and pH value is 7.8-8.4.

[0018] Preferably, the nutrients of nitrogen, phosphorus and potassium fertilizers are: N=15%, P2O5=5%, K2O=25%.

[0019] Preferably, the mass ratio of nitrogen, phosphorus and potassium fertilizers to water-soluble fertilizers is 1:8. The mass ratio of peregrin, EDTA and concentrated biogas slurry is 0.5:28:1000.

[0020] The concentration conditions of the reverse osmosis concentration membrane are as follows: the operating pressure is 1.2-1.5Mpa; the reverse osmosis membrane is a polyamide reverse osmosis membrane, and the water flux is 35-45LMH.

[0021] Among them, nitrogen, phosphorus and potassium fertilizers are prepared from urea, superphosphate and potassium sulfate, and the mass ratio of urea, superphosphate and potassium sulfate is 15-17:12-13:20-22.

[0022] Preferably, the nitrogen, phosphorus and potassium fertilizers also include ammonium molybdate, and the amount of ammonium molybdate used is 4-10‰ of the quality of urea.

[0023] In another aspect, embodiments of the present invention further provide a method for preparing the aforementioned compound fertilizer specifically for citrus crops during the fruit-swelling period. The method comprises: mixing urea, superphosphate, potassium sulfate, and ammonium molybdate in a specific ratio, granulating, drying, screening, and coating to produce a nitrogen, phosphorus, and potassium fertilizer. Biogas slurry is concentrated 6-8 times using a reverse osmosis concentration membrane to produce concentrated biogas slurry. Under sterile conditions, the slurry is mixed with EDTA, peregal, streptomycin, and a preservative in a specific ratio, and then sealed and packaged to produce a water-soluble fertilizer.

[0024] This patent has the following advantages: (1) This special fertilizer can increase citrus yield, with an average increase of 153 kg per mu.

[0025] (2) This special fertilizer can slightly improve the quality of citrus, with the sugar content increased by 11.51%, the acidity decreased by 8.5%, and the sugar-acid ratio increased by 3.94.

[0026] (3) Compared with other fertilizers, the application of this special fertilizer can increase the value of each mu by an average of 1,955 yuan, and the output value growth rate reaches 4.51%.

[0027] (4) It can significantly reduce the incidence of Huanglongbing disease. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the planting situation of the experimental plot; Figure 2 This is a comparison of the early stages of citrus under different treatments Figure 1 ; Figure 3 This is a comparison of the early stages of citrus under different treatments Figure 2 ; Figure 4 The occurrence of soot disease on citrus leaves under two different fertilization treatments; Figure 5 The incidence of Huanglongbing on citrus leaves under two different fertilizer treatments; Figure 6 is the weight of citrus under two different fertilizer treatments. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] Example 1 Example 1 provides a method for preparing a compound fertilizer specifically for citrus crops during the fruit-swelling period. The method comprises: mixing 1540 kg of urea, 1260 kg of superphosphate, 2140 kg of potassium sulfate, and 10 kg of ammonium molybdate; granulating, drying, screening, and coating to obtain a nitrogen, phosphorus, and potassium fertilizer. Biogas slurry is concentrated sevenfold using a reverse osmosis concentration membrane to obtain concentrated biogas slurry. Under sterile conditions, 0.5 kg of peregrine, 4 kg of potassium sorbate, 0.35 kg of streptomycin, and 28 kg of EDTA are mixed with 1000 kg of the concentrated biogas slurry and sealed in barrels (25 kg per barrel) to obtain a water-soluble fertilizer. 12.5 kg of nitrogen, phosphorus, and potassium fertilizer is mixed with 100 kg of the water-soluble fertilizer to obtain a compound fertilizer specifically for citrus crops during the fruit-swelling period.

[0031] The parameters of the concentrated biogas slurry are as follows: P2O5 content is 0.24 g / L, K2O content is 2.1 g / L, N content is 4.9 g / L, organic matter content is 2.4 g / L, amino acid content is 0.25 g / L, humic acid content is 9.4 g / L, calcium ion content is 35 mg / L, iron ion content is 37 mg / L, zinc ion content is 31 mg / L, and pH value is 7.9.

[0032] Example 2 Example 2 provides a method for preparing a compound fertilizer specifically for citrus crops during the fruit-swelling period. The method comprises: mixing 1540 kg of urea, 1260 kg of superphosphate, 2140 kg of potassium sulfate, and 10 kg of ammonium molybdate; granulating, drying, screening, and coating to obtain a nitrogen, phosphorus, and potassium fertilizer. Biogas slurry is concentrated sevenfold using a reverse osmosis concentration membrane to obtain concentrated biogas slurry. Under sterile conditions, 0.6 kg of peregrine, 4.5 kg of potassium sorbate, 0.38 kg of streptomycin, and 30 kg of EDTA are mixed with 1000 kg of the concentrated biogas slurry and sealed in barrels (25 kg per barrel) to obtain a water-soluble fertilizer. 12.5 kg of nitrogen, phosphorus, and potassium fertilizer is mixed with 100 kg of the water-soluble fertilizer to obtain a compound fertilizer specifically for citrus crops during the fruit-swelling period.

[0033] Example 3 Example 3 provides a method for preparing a compound fertilizer specifically for citrus crops during the fruit-swelling period. The method comprises: mixing 1540 kg of urea, 1220 kg of superphosphate, 2100 kg of potassium sulfate, and 10 kg of ammonium molybdate; granulating, drying, screening, and coating to obtain a nitrogen, phosphorus, and potassium fertilizer. Biogas slurry is concentrated 7.5 times using a reverse osmosis concentration membrane to obtain concentrated biogas slurry. Under sterile conditions, 0.45 kg of peregrine, 4.5 kg of potassium sorbate, 0.4 kg of streptomycin, and 25 kg of EDTA are mixed with 1000 kg of the concentrated biogas slurry and sealed in barrels (25 kg per barrel) to obtain a water-soluble fertilizer. 10 kg of nitrogen, phosphorus, and potassium fertilizer is mixed with 100 kg of the water-soluble fertilizer to obtain a compound fertilizer specifically for citrus crops during the fruit-swelling period.

[0034] Verification Example 1. Materials and Methods 1.1 Test location: Xiangshan Village, Shiqiaoyi Town, Jingmen City, Hubei Province.

[0035] 1.2 Test soil: The test soil fertility is low, with soil organic matter 1.0%, soil alkaline nitrogen 74.5 mg / kg, available phosphorus 20.7 mg / kg, available potassium 87.8 mg / kg, and soil pH 7.5.

[0036] 1.3 Test crops and varieties: Citrus Ehime 28.

[0037] 1.4 Time: February 2022 to February 2023.

[0038] 1.5 Planting area: 100 mu, of which 80 mu were applied with the special fertilizer (Example 1), and 20 mu were applied with other fertilizers (nitrogen, phosphorus, and potassium fertilizers dissolved in equal amounts of clean water).

[0039] 1.6 Fertilization time and fertilizer: As shown in Table 1: Table 1: Fertilization situation of field experiment

[0040] 1.7 Processing Settings: Treatment 1: This special fertilizer (wintering organic fertilizer 10kg / plant, fruit-swelling fertilizer 1kg / plant), diluted 100 times; Treatment 2: Other fertilizers (10 kg / plant of winter organic fertilizer and 1 kg / plant of fruit-swelling fertilizer), with a dilution ratio of 100 times.

[0041] 1.8 Pest and disease management The main diseases and pests of citrus are Huanglongbing, red spider mites, leaf miners and scale insects. The main prevention and control methods are to apply cypermethrin and a mixture of it and etoxazole.

[0042] Previous planting conditions: Citrus has always been cultivated. Other fertilizers were used previously, but due to unsatisfactory yields, this special fertilizer has been used instead. The citrus cultivation area is located on a hillside, and the experimental site has a steep slope. The soil is poor and water is easily lost, making water and fertilizer management difficult. 1.9 Statistical Methods All data were statistically analyzed by EXCEL and SAS, and then the difference significance test was performed.

[0043] 2. Fertilization and management technology of Eyuan No. 28 Ehime 28 requires a high amount of fertilizer. Inadequate fertilizer and water supply can lead to small leaves and fruit, weakened trees, and prone to alternate bearing. Similar to other citrus varieties, young trees should primarily receive nitrogen and organic fertilizers, with frequent, light applications to cultivate a healthy, high-yielding tree. Producing trees should receive four main fertilizer applications annually: bud break, fruit expansion, color change, and wintering.

[0044] Bud fertilizer: Apply before spring shoots sprout, mainly with fast-acting nitrogen fertilizer and potassium fertilizer, and apply Zhimeijia multi-nutrient liquid fertilizer (root application type) in combination to awaken the root system and promote new shoots.

[0045] Fruit-swelling fertilizer: From late May to early July, apply compound fertilizer + medium and trace element fertilizer to achieve the purpose of strengthening fruits, promoting shoots and nourishing roots.

[0046] Color-changing fertilizer: From late August to early September, mainly potassium fertilizer, root application and foliar topdressing should be combined.

[0047] Overwintering fertilizer: From late November to early December, mainly use long-lasting organic fertilizer, combined with balanced fertilizer and medium and trace element fertilizer, combined with deep plowing and soil improvement.

[0048] In addition, foliar fertilization should be used to ensure the nutritional supply of citrus during each critical growth period.

[0049] 3. Results and Analysis 3.1 Effects of different fertilizer treatments on soil nutrients in citrus fields like Figure 1 As shown, the fruit trees in the experimental plot ranged in age from 4 to 15 years, the terrain was rugged, the soil fertility was average, and citrus yields in previous years were average. Based on these external conditions, soil samples were collected and analyzed for some physical and chemical properties of the experimental field, as shown in Table 1. Compared to pre-fertilization, the application of this specialized fertilizer increased nutrient content in the experimental field, with significant differences in organic matter and alkaline nitrogen content. Compared to other fertilizers, the application of this specialized fertilizer significantly increased soil organic matter, while other nutrients showed no significant differences, and the pH did not change significantly.

[0050] Table 2: Effects of different fertilization treatments on the geochemical properties of citrus fruit

[0051] 3.2 Effects of different fertilization treatments on citrus pests and diseases Pests and diseases are key factors affecting the yield and quality of citrus. There are many common diseases of citrus, among which the main diseases and pests on citrus in Jingmen, Hubei are Huanglongbing, leaf miner, and fumigation (such as Figure 4 、 5 (as shown in Table 3) The incidence of Huanglongbing and fumigation was measured under the two different fertilizer treatments. Specific data are shown in Table 3. While there were no significant differences in the incidence of Huanglongbing and leaf miner in citrus between the two fertilizer treatments, it was clear that the specialized fertilizer had slightly stronger disease resistance, with citrus fruits growing significantly better when treated with it. This is because it contains a high concentration of antibacterial, insecticide, and growth-promoting substances, which effectively reduce the invasion of pests and diseases, thereby improving citrus' disease resistance.

[0052] Table 3: Effects of different fertilization treatments on citrus diseases and insect pests

[0053] 3.3 Effects of different fertilization treatments on citrus yield indicators Yield is the most important factor affecting economic benefits, and fertilization can increase citrus yield. Random sampling was used to measure yield in citrus trees across multiple plots at the experimental site. Three locations were selected for yield measurement: size, weight of multiple citrus trees, and the number of fruits per tree. As shown in Table 4, the size and weight of citrus trees treated with this special fertilizer were not significantly different from those treated with other fertilizers. However, the number of fruits per tree was significantly higher, significantly more than those treated with other fertilizers. The reduction in pests and diseases also increased the survival rate of citrus trees. This demonstrates that the application of this special fertilizer can increase citrus yield.

[0054] Table 4: Impact of citrus yield indicators

[0055] like Figure 6These are three replicates under two different treatments. The left side shows citrus fruits treated with this fertilizer, and the right side shows citrus fruits treated with other fertilizers. In replicate 1, the left reading was 1.45, and the right reading was 1.30. This indicates that this fertilizer promotes fruit enlargement in citrus fruits.

[0056] 3.4 Effects of different fertilization treatments on citrus quality indicators Quality is a major factor influencing price. Fresh citrus fruits were collected at harvest time and quality indicators such as total sugar, soluble protein, vitamin C, and titratable acid were measured. Finally, the sugar-acid ratio of the citrus fruits under the two different fertilizer treatments was calculated. The data in Table 5 show that the quality of the citrus fruits under the two different fertilizer treatments differed slightly, but the differences were not significant. Soluble protein and vitamin C content increased slightly, sugar content increased by 11.51%, acidity decreased by 8.5%, and the sugar-acid ratio increased by 3.94, indicating that the citrus fruits treated with this special fertilizer had a sweeter and more refreshing taste.

[0057] Table 5: Effects of different fertilization treatments on citrus quality indicators during harvest

[0058] 3.5 Economic benefit analysis of citrus under different fertilizer treatment conditions The effects of different treatments on citrus yield and quality were analyzed, and the economic benefits of citrus under different fertilizer treatments were further analyzed. Economic benefits are the most direct indicator of profitability. As shown in Table 6, the fertilizer price of this special fertilizer is 2 yuan / kg higher than other fertilizers, and the average fertilizer cost is 300 yuan more per mu. However, this special fertilizer produces an average of 153 kg more citrus per mu. Based on the wholesale price of citrus of 15 yuan / kg, the profit per mu after applying this special fertilizer is 46,220 yuan, while the profit per mu after applying other fertilizers is 44,225 yuan, an increase of 1,955 yuan in output value, and an output value growth rate of 4.51%. This shows that this special fertilizer can produce higher profits under the premise of high price.

[0059] Table 6: Economic benefits of citrus under different fertilization treatments

[0060] This specialized fertilizer is rich in microbial metabolites, which can improve soil resistance to continuous cropping, enhance soil enzyme and microbial activity, and promote soil nutrient conversion, thereby increasing yield and quality. Table 5 shows that citrus treated with this fertilizer had higher levels of total sugar, soluble protein, and vitamin C than those treated with other fertilizers, while having lower titratable acid content and a 3.94 increase in the sugar-acid ratio, indicating a better taste. Table 6 also shows that citrus treated with this fertilizer resulted in higher yields and greater economic benefits. Therefore, this fertilizer can increase the profitability of citrus cultivation in this region. Comparative Example The planting area of ​​each comparative ratio was 5 mu, and it was carried out at the same time as the above experiment. The fertilization method and amount were the same as the above experiment, and the treatment location was the same.

[0061] Comparative Example 1 In Comparative Example 1, the nitrogen, phosphorus and potassium fertilizers were replaced with an equal weight of compound fertilizer 15-15-15, and the rest were the same as in Example 1.

[0062] Comparative Example 2 In Comparative Example 2, concentrated biogas slurry was obtained by vacuum concentration at a concentration temperature of 70° C., and other conditions were the same as those in Example 1.

[0063] Comparative Example 3 In Comparative Example 3, Peregal was replaced with Tween-60.

[0064] Comparative Example 4 In Comparative Example 4, nitrogen, phosphorus and potassium fertilizers were dissolved in clean water, and peregal, potassium sorbate, streptomycin, EDTA and an equal weight (relative to Example 1) of P2O5, K2O, N, organic matter, amino acids (complex amino acids, mainly histidine), humic acid, calcium ions (sulfate or chelated salt, the same below), iron ions, and zinc ions were added.

[0065] Comparative Example 5 In Comparative Example 5, the biogas slurry was concentrated 15 times using a reverse osmosis membrane to obtain concentrated biogas slurry, and the mass ratio of nitrogen, phosphorus and potassium fertilizers to the concentrated biogas slurry was the same as that in Example 1.

[0066] The results are shown in Table 7: Table 7

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A special compound fertilizer for citrus crops during the fruit-swelling period, characterized in that: The invention comprises water-soluble fertilizer and nitrogen, phosphorus and potassium fertilizer, wherein the water-soluble fertilizer comprises concentrated biogas slurry, EDTA, peregal, streptomycin and a preservative; the concentrated biogas slurry is obtained by concentrating the biogas slurry 6-8 times through a reverse osmosis concentration membrane; the mass ratio of the nitrogen, phosphorus and potassium fertilizer to the water-soluble fertilizer is 1:5-12; the mass ratio of peregal, EDTA and concentrated biogas slurry is 0.2-1.0:25-35:1000; the dosage of the preservative is 0.1-0.5% of the weight of the concentrated biogas slurry, and the dosage of the streptomycin is 1-5‰ of the weight of the nitrogen, phosphorus and potassium fertilizer; the nutrients of the nitrogen, phosphorus and potassium fertilizer are: 14%<N<16%, 4.5%<P2O5<5.5%, and 23%<K2O<27%; when in use, the water-soluble fertilizer and the nitrogen, phosphorus and potassium fertilizer are mixed and diluted 50-150 times before spraying.

2. The compound fertilizer specifically for citrus crops during the fruit-swelling period according to claim 1, characterized in that: The source of the biogas slurry is a biogas tank from a pig farm, the fermentation temperature is 15-45°C, and the fermentation time is more than 3 months.

3. The compound fertilizer specifically for citrus crops during the fruit-swelling period according to claim 1, characterized in that: The parameters of the concentrated biogas slurry are: P2O5 content of 0.20-0.30 g / L, K2O content of 1.6-2.4 g / L, N content of 4.4-6.0 g / L, organic matter content of 2.2-3.5 g / L, amino acid content of 0.15-0.28 g / L, humic acid content of 6-12 g / L, calcium ion content of 20-40 mg / L, iron ion content of 25-42 mg / L, zinc ion content of 15-27 mg / L, and pH value of 7.8-8.

4.

4. The special compound fertilizer for citrus crops during the fruit-swelling period according to claim 3, characterized in that The nutrients of the nitrogen, phosphorus and potassium fertilizer are: N=15%, P2O5=5%, K2O=25%.

5. The special compound fertilizer for citrus crops during the fruit-swelling period according to claim 4, characterized in that The mass ratio of nitrogen, phosphorus and potassium fertilizers to water-soluble fertilizers is 1:8; the mass ratio of peregrin, EDTA and concentrated biogas slurry is 0.5:28:1000.

6. The compound fertilizer specifically for citrus crops during the fruit-swelling period according to claim 1, characterized in that: The concentration conditions of the reverse osmosis concentration membrane are as follows: the operating pressure is 1.2-1.5 MPa; the reverse osmosis membrane is a polyamide reverse osmosis membrane, and the water flux is 35-45 LMH.

7. The compound fertilizer specifically for citrus crops during the fruit-swelling period according to claim 1, characterized in that: The nitrogen, phosphorus and potassium fertilizer is prepared from urea, superphosphate and potassium sulfate, and the mass ratio of the urea, superphosphate and potassium sulfate is 15-17:12-13:20-22.

8. The compound fertilizer specifically for citrus crops during the fruit-swelling period according to claim 7, characterized in that: The nitrogen, phosphorus and potassium fertilizers also include ammonium molybdate, and the amount of the ammonium molybdate used is 4-10‰ of the quality of urea.

9. The method for preparing the special compound fertilizer for citrus crops during the fruit-swelling period according to claim 8, characterized in that: The method comprises: mixing urea, superphosphate, potassium sulfate and ammonium molybdate according to a proportion, granulating, drying, screening and coating to obtain nitrogen, phosphorus and potassium fertilizers; concentrating biogas slurry by 6-8 times through a reverse osmosis concentration membrane to obtain concentrated biogas slurry, mixing it with EDTA, peregal, streptomycin and a preservative according to a proportion under sterile conditions, and sealing and packaging to obtain water-soluble fertilizers.

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