A method for preparing a special fertilizer for saline-alkali soil by using agricultural waste

Abstract

This invention belongs to the field of fertilizer technology, specifically relating to a method for preparing a special fertilizer for saline-alkali land using agricultural waste. The method involves using *Pseudomonas halophilus*... Halopseudomonas salina With Bacillus subtilis Bacillus subtilis With Bacillus megaterium Bacillus megaterium A compound fermented seed liquid was prepared by mixing seed liquids at a mass ratio of 1-3:1-3:1-3. Rice straw, corn straw, peanut shells, and livestock manure were used as fermentation substrates, mixed with water, and inoculated with the compound fermented seed liquid. Fermentation was carried out at 30-32℃ for 9-12 days to obtain bio-fertilizer. The bio-fertilizer was then mixed with humic acid and trace element fertilizers, granulated, and coated with polylactic acid to produce a slow-release fertilizer. This fertilizer can effectively reduce the pH and salinity of saline-alkali soils, increase organic matter content, and promote crop growth.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer technology, specifically relating to a method for preparing special fertilizers for saline-alkali land using agricultural waste. Background Technology

[0002] Saline-alkali land is a type of degraded land with excessively high soil salinity. Saline-alkali land has poor soil structure and low permeability. Furthermore, the high salinity inhibits microbial activity and crop nutrient absorption, resulting in a conventional fertilizer utilization efficiency of less than 30% and hindering crop growth, which seriously restricts the sustainable development of agriculture.

[0003] Currently, methods for improving saline-alkali land include physical salt leaching, chemical neutralization, and bioremediation. Physical salt leaching relies on large amounts of freshwater, which is costly and consumes a lot of water resources, making it difficult to promote in arid areas. Chemical improvement involves applying chemicals such as gypsum and sulfur to neutralize alkalinity, but long-term use can easily lead to secondary soil pollution and cannot fundamentally improve the soil microecology. Bioremediation involves planting salt-tolerant plants to absorb salt, but it is time-consuming, slow to take effect, and limited by climate and species.

[0004] Bio-fertilizers, as an environmentally friendly alternative, improve soil microecology through microbial activity. Agricultural waste (such as straw and livestock manure) is rich in organic matter and nutrients, but its direct application may cause secondary pollution. Furthermore, the high salinity of saline-alkali land strongly inhibits microbial activity, and strains in ordinary microbial fertilizers are easily inactivated, resulting in poor fertilizer effectiveness. Therefore, developing a slow-release fertilizer specifically for saline-alkali land that utilizes agricultural waste, combines specific salt-tolerant microbial combinations, and employs biodegradable coating technology has significant application value. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a special fertilizer for saline-alkali land using agricultural waste. By screening specific salt-tolerant microorganisms and compounding them, and using a specific combination of agricultural wastes as the fermentation substrate, a bio-fertilizer is prepared. This bio-fertilizer is then mixed with humic acid and trace element fertilizers, granulated, and combined with slow-release coating technology to prepare a special fertilizer that can effectively adapt to and improve the saline-alkali land environment.

[0006] On the one hand, the present invention provides a method for preparing special fertilizer for saline-alkali land using agricultural waste, the method comprising the following steps:

[0007] S1. Preparation of compound fermentation seed liquid: The seed liquids of *Halopseudomonas salina*, *Bacillus subtilis*, and *Bacillus megaterium* were mixed at a mass ratio of 1-3:1-3:1-3 to prepare the compound fermentation seed liquid. The preservation number of *Halopseudomonas salina* is CGMCC 1.12482, the preservation number of *Bacillus subtilis* is CGMCC 1.2416, and the preservation number of *Bacillus megaterium* is CGMCC 1.6721.

[0008] S2. Preparation of microbial fertilizer fermentation substrate: After drying agricultural waste, it is crushed to a particle size of 0.5-2mm to obtain microbial fertilizer fermentation substrate. The agricultural waste includes rice straw, corn straw, peanut shells and livestock and poultry manure.

[0009] S3, Solid-state fermentation: The microbial fertilizer fermentation substrate prepared in S2 is mixed with water at a mass ratio of 1:1, and the compound fermentation seed liquid prepared in S1 is added. The amount added is 9%-12% of the total mass of the solid-state fermentation culture medium. Fermentation is carried out at 28-32℃ for 9-12 days to obtain bio-fertilizer.

[0010] S4. Preparation of fertilizer suspension: The bio-fertilizer obtained in S3 is mixed with humic acid, manganese sulfate, ferrous ammonium sulfate, zinc sulfate, calcium magnesium phosphate, urea, potassium dihydrogen phosphate and boron fertilizer, and stirred evenly to obtain fertilizer suspension.

[0011] S5. Granulation and coating: After drying the suspension, it is mixed with starch and granulated using a fluidized bed granulator to obtain core fertilizer. Then, it is coated with polylactic acid to obtain slow-release fertilizer for saline-alkali land.

[0012] Furthermore, in the method, the mass ratio of the seed liquid of *Halopseudomonas salina*, *Bacillus subtilis*, and *Bacillus megaterium* in the composite fermentation seed liquid is 2:1:3.

[0013] Furthermore, in the method, the agricultural waste is based on a total mass of 10 parts, and includes: 1-2 parts rice straw, 1-3 parts corn straw, 1-2 parts peanut shells, and 1-2 parts livestock and poultry manure.

[0014] Further, in the method, step S4 includes, by weight, 80-90 parts of bio-fertilizer, 18-21 parts of humic acid, 5-6 parts of manganese sulfate, 8-12 parts of ferrous ammonium sulfate, 6-8 parts of zinc sulfate, 5-9 parts of calcium magnesium phosphate fertilizer, 17-21 parts of urea, 10-13 parts of potassium dihydrogen phosphate, and 5-8 parts of boron fertilizer.

[0015] Furthermore, in the method, in step S5, the particle size of the core fertilizer after granulation is 4-8 mm, and the moisture content of the core fertilizer is ≤8%.

[0016] Furthermore, in the method, in step S5, the drying temperature after coating is 40-50℃, and the drying time is 1-2 hours.

[0017] Secondly, a slow-release fertilizer specifically for saline-alkali land is prepared by the method described in this invention.

[0018] Thirdly, the present invention also provides the application of the slow-release fertilizer for saline-alkali land in increasing crop yields in saline-alkali land.

[0019] Finally, the application of the slow-release fertilizer for saline-alkali land described in this invention in the improvement of saline-alkali land soil is also provided.

[0020] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0021] (1) This invention creatively selects specific strains: *Pseudomonas halophilus* CGMCC 1.12482, *Bacillus subtilis* CGMCC 1.2416, and *Bacillus megaterium* CGMCC 1.6721, for combination. Comparative experiments show that using only a single strain or replacing it with a similar strain with other preservation numbers results in soil improvement and yield increase far less than the specific strain combination of this invention. This indicates that the specific strains selected in this invention have unique and irreplaceable synergistic effects, working together to cope with saline-alkali stress, decompose organic matter, and activate nutrients.

[0022] (2) This invention uses agricultural waste such as rice straw, corn straw, peanut shells and livestock and poultry manure as the main fermentation substrate to realize the efficient resource utilization of waste, turn waste into treasure, meet the requirements of green agriculture and sustainable development, and at the same time reduce environmental pollution.

[0023] (3) High efficiency in improving saline-alkali soil: The special slow-release fertilizer prepared by this invention can effectively reduce the pH value and salt content of saline-alkali soil. Field trial results show that the soil pH value of the experimental group applying the special slow-release fertilizer for saline-alkali soil provided by this invention decreased from the initial 9.1 to 8.73-8.81, and the salt content decreased significantly from 0.39% to 0.07%-0.09%, which is significantly better than the control groups and blank control, creating a more suitable growth environment for crops.

[0024] (4) Significantly improves soil fertility: The special slow-release fertilizer prepared by this invention, using a specific combination of bacterial strains and agricultural waste as substrates for fermentation, produces a bio-fertilizer that, together with humic acid and trace element fertilizers, significantly increases the organic matter content of saline-alkali soil. Field trial results show that the soil organic matter content in the experimental group applying the special slow-release fertilizer for saline-alkali soil provided by this invention increased to 1.21%-1.25%, far exceeding the 0.83% of the blank control group and the control groups of single bacterial species or different bacterial species combinations, significantly improving the infertile soil structure of saline-alkali land.

[0025] (5) Significantly increases crop yield: The special slow-release fertilizer prepared by this invention effectively promotes the growth of crops in saline-alkali land and significantly increases yield. Through polylactic acid biodegradable coating technology, the slow release of nutrients is achieved, improving the utilization rate of fertilizer in saline-alkali land, which is prone to nutrient loss or fixation. At the same time, the coating plays a certain protective role for microbial agents.

[0026] In summary, this invention provides a special fertilizer for saline-alkali land that effectively improves the soil environment and increases crop yield, as well as its preparation method, offering more solutions to the problem of saline-alkali land management. Detailed Implementation

[0027] The technical solution of the present invention will be described below with reference to the embodiments. However, the present invention is not limited to the following embodiments.

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments, but the embodiments are not intended to limit the present invention.

[0029] Unless otherwise specified, the experimental and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0030] Halopseudomonas salina, accession number CGMCC 1.12482, was purchased from the China General Microbiological Culture Collection Center and is referred to as Halopseudomonas salina CGMCC 1.12482 below.

[0031] Bacillus megaterium, accession number CGMCC 1.6721, was purchased from the China General Microbiological Culture Collection Center and is referred to as Bacillus megaterium CGMCC 1.6721 below.

[0032] Bacillus subtilis, accession number: CGMCC 1.2416, was purchased from the China General Microbiological Culture Collection Center and is referred to as Bacillus subtilis CGMCC 1.2416 below.

[0033] Bacillus subtilis, accession number CGMCC 1.12939, was purchased from the China General Microbiological Culture Collection Center and is referred to as Bacillus subtilis CGMCC 1.12939 below.

[0034] Bacillus megaterium, accession number ATCC 14581, was purchased from Shanghai Fuxiang Biotechnology Co., Ltd., and is referred to below as Bacillus megaterium ATCC 14581.

[0035] Example 1

[0036] This example demonstrates the preparation of seed solution.

[0037] The halophilic Pseudomonas halophilus CGMCC 1.12482, stored in a -80℃ freezer, was streaked onto the surface of LB medium for activation. The activated halophilic Pseudomonas halophilus CGMCC 1.12482 was then inoculated into LB liquid medium and cultured at 37℃ with shaking at 220 rpm for 1 day to obtain the halophilic Pseudomonas halophilus CGMCC 1.12482 seed culture.

[0038] Bacillus subtilis CGMCC 1.2416, stored in a -80℃ freezer, was streaked onto the surface of LB medium for activation. The activated Bacillus subtilis CGMCC 1.2416 was then inoculated into LB liquid medium and cultured at 37℃ with shaking at 220 rpm for 1 day to obtain Bacillus subtilis CGMCC 1.2416 seed culture.

[0039] Bacillus megaterium CGMCC 1.6721 stored in a -80℃ freezer was taken out and streaked onto the surface of LB medium for activation. The activated Bacillus megaterium CGMCC 1.6721 was then inoculated into LB liquid medium and cultured at 37℃ with shaking at 220 rpm for 1 day to obtain the seed culture of Bacillus megaterium CGMCC 1.6721.

[0040] Bacillus subtilis CGMCC 1.12939, stored in a -80℃ freezer, was streaked onto the surface of LB medium for activation. The activated Bacillus subtilis CGMCC 1.12939 was then inoculated into LB liquid medium and cultured at 37℃ with shaking at 220 rpm for 1 day to obtain Bacillus subtilis CGMCC 1.12939 seed culture.

[0041] Bacillus megaterium ATCC 14581 stored in a -80℃ freezer was taken out and streaked onto the surface of LB medium for activation. The activated Bacillus megaterium ATCC 14581 was then inoculated into LB liquid medium and cultured at 37℃ with shaking at 220 rpm for 1 day to obtain Bacillus megaterium ATCC 14581 seed culture.

[0042] Example 2

[0043] This example demonstrates the preparation of bio-fertilizer.

[0044] Weigh out 2 parts rice straw, 2 parts corn straw, 1 part peanut shell, and 1 part sheep manure by weight. Dry the above raw materials, crush them, mix them thoroughly, and then crush them to a particle size of 0.5-2 mm to prepare a substrate for microbial fertilizer fermentation.

[0045] The prepared microbial fertilizer fermentation substrate was mixed with an equal mass of water to obtain a solid fermentation medium. The seed liquid of *Pseudomonas halophilus* CGMCC 1.12482, the seed liquid of *Bacillus subtilis* CGMCC 1.2416, and the seed liquid of *Bacillus megaterium* CGMCC 1.6721 were mixed evenly at a mass ratio of 1:2:2 to obtain a compound fermentation seed liquid. 10% of the total mass of the solid fermentation medium was added to the compound fermentation seed liquid, and fermentation was carried out at 28℃ for 10 days to obtain the bio-fertilizer, which was labeled as No. 1 bio-fertilizer.

[0046] Example 3

[0047] This embodiment describes the preparation of bio-fertilizer.

[0048] Weigh out 1 part rice straw, 3 parts corn straw, 2 parts peanut shells, and 2 parts sheep manure by weight. Dry the above raw materials, crush them, mix them thoroughly, and then crush them to a particle size of 0.5-2 mm to prepare a substrate for microbial fertilizer fermentation.

[0049] The prepared microbial fertilizer fermentation substrate was mixed with an equal mass of water to obtain a solid fermentation medium. The seed liquid of *Pseudomonas halophilus* CGMCC 1.12482, the seed liquid of *Bacillus subtilis* CGMCC 1.2416, and the seed liquid of *Bacillus megaterium* CGMCC 1.6721 were mixed evenly in a mass ratio of 2:1:3 to obtain a compound fermentation seed liquid. 9% of the total mass of the compound fermentation seed liquid of the solid fermentation medium was added, and fermentation was carried out at 30℃ for 12 days to obtain the bio-fertilizer, which was labeled as No. 2 bio-fertilizer.

[0050] Example 4

[0051] This embodiment describes the preparation of bio-fertilizer.

[0052] Weigh out 2 parts rice straw, 1 part corn straw, 1 part peanut shells, and 1 part cow dung by weight. Dry the above raw materials, crush them, mix them thoroughly, and then crush them to a particle size of 0.5-2 mm to prepare a substrate for microbial fertilizer fermentation.

[0053] The prepared microbial fertilizer fermentation substrate was mixed with an equal mass of water to obtain a solid fermentation medium. The seed liquid of *Pseudomonas halophilus* CGMCC 1.12482, the seed liquid of *Bacillus subtilis* CGMCC 1.2416, and the seed liquid of *Bacillus megaterium* CGMCC 1.6721 were mixed evenly in a mass ratio of 3:3:1 to obtain a compound fermentation seed liquid. 12% of the total mass of the compound fermentation seed liquid was added to the solid fermentation medium and fermented at 32℃ for 9 days to obtain the bio-fertilizer, which was labeled as No. 3 bio-fertilizer.

[0054] Comparative Example 1

[0055] This comparative example is for preparing a contrast agent bio-fertilizer.

[0056] The only difference between this comparative example and Example 4 is that the compound fermentation seed liquid was replaced with a single halophilic Pseudomonas halophilus CGMCC 1.12482 seed liquid. All other conditions were the same, and the resulting bio-fertilizer was labeled as #1 contrast agent bio-fertilizer.

[0057] Comparative Example 2

[0058] This comparative example is for preparing a contrast agent bio-fertilizer.

[0059] The only difference between this comparative example and Example 4 is that the compound fermentation seed liquid was replaced with a single Bacillus subtilis CGMCC 1.2416 seed liquid. All other conditions were the same, and the resulting bio-fertilizer was labeled as #2 contrast agent bio-fertilizer.

[0060] Comparative Example 3

[0061] This comparative example is for preparing a contrast agent bio-fertilizer.

[0062] The only difference between this comparative example and Example 4 is that the compound fermentation seed liquid contains Bacillus megaterium CGMCC1.6721 seed liquid. All other conditions are the same. The resulting bio-fertilizer is labeled as No. 3 contrast agent bio-fertilizer.

[0063] Comparative Example 4

[0064] This comparative example is for preparing a contrast agent bio-fertilizer.

[0065] The only difference between this comparative example and Example 4 is that the Bacillus subtilis CGMCC1.2416 seed solution in the compound fermentation seed solution was replaced with the Bacillus subtilis CGMCC1.12939 seed solution prepared in Example 1. Specifically, the compound fermentation seed solution was prepared by uniformly mixing the *Pseudomonas halophilus* CGMCC1.12482 seed solution, the Bacillus subtilis CGMCC1.12939 seed solution, and the *Bacillus megaterium* CGMCC1.6721 seed solution at a mass ratio of 3:3:1. All other conditions were the same, and the resulting bio-fertilizer was labeled as #4 contrast agent bio-fertilizer.

[0066] Comparative Example 5

[0067] This comparative example is for preparing a contrast agent bio-fertilizer.

[0068] The only difference between this comparative example and Example 4 is that the Bacillus megaterium CGMCC1.6721 seed solution in the compound fermentation seed solution was replaced with the Bacillus megaterium ATCC 14581 seed solution prepared in Example 1. Specifically, the compound fermentation seed solution was prepared by uniformly mixing the Pseudomonas halophilus CGMCC 1.12482 seed solution, the Bacillus subtilis CGMCC 1.12939 seed solution, and the Bacillus megaterium ATCC14581 seed solution at a mass ratio of 3:3:1. All other conditions were the same, and the resulting bio-fertilizer was labeled as #5 contrast agent bio-fertilizer.

[0069] Example 5

[0070] This embodiment provides a slow-release fertilizer specifically for saline-alkali land and its preparation method.

[0071] In this embodiment, the slow-release fertilizer for saline-alkali land includes, by weight, 80 parts of No. 1 bio-fertilizer, 20 parts of humic acid, 6 parts of manganese sulfate, 11 parts of ferrous ammonium sulfate, 7 parts of zinc sulfate, 9 parts of calcium magnesium phosphate fertilizer, 21 parts of urea, 12 parts of potassium dihydrogen phosphate, 8 parts of boron fertilizer, 15 parts of starch, and 20 parts of polylactic acid.

[0072] The preparation method of the above-mentioned slow-release fertilizer for saline-alkali land in this embodiment includes the following steps:

[0073] Step 1: Weigh all materials according to the component mass proportions in the example.

[0074] Step 2: Thoroughly mix fulvic acid, manganese sulfate, ferrous ammonium sulfate, zinc sulfate, calcium magnesium phosphate fertilizer, urea, potassium dihydrogen phosphate, boron fertilizer and bio-fertilizer, stir evenly to obtain a suspension;

[0075] Step 3: Dry the suspension obtained in Step 2 in a dryer at 40°C using hot air. After drying, add starch and granulate using a fluidized bed granulator to obtain a particle size of 5-6 mm to produce core fertilizer. Then dry the core fertilizer at 60°C until the moisture content of the core fertilizer is less than or equal to 8%.

[0076] Step 4: Add the core fertilizer obtained in Step 3 and polylactic acid to the coating equipment and stir at 100 rpm for 10 minutes. During stirring, spray water at 5% of the mass of polylactic acid into the coating equipment using a spray device to ensure that the polylactic acid adheres evenly to the surface of the core fertilizer. After coating, place it in a drying oven at 40°C and dry for 2 hours. This yields a slow-release fertilizer specifically for saline-alkali land, labeled as #1 slow-release fertilizer for saline-alkali land.

[0077] Example 6

[0078] This embodiment provides a slow-release fertilizer specifically for saline-alkali land and its preparation method.

[0079] In this embodiment, the slow-release fertilizer for saline-alkali land includes, by weight, 85 parts of No. 2 bio-fertilizer, 21 parts of humic acid, 5 parts of manganese sulfate, 12 parts of ferrous ammonium sulfate, 8 parts of zinc sulfate, 7 parts of calcium magnesium phosphate fertilizer, 20 parts of urea, 13 parts of potassium dihydrogen phosphate, 7 parts of boron fertilizer, 18 parts of starch, and 21 parts of polylactic acid.

[0080] The preparation method of the above-mentioned slow-release fertilizer for saline-alkali land in this embodiment includes the following steps:

[0081] Step 1: Weigh all materials according to the component mass proportions in the example.

[0082] Step 2: Thoroughly mix fulvic acid, manganese sulfate, ferrous ammonium sulfate, zinc sulfate, calcium magnesium phosphate fertilizer, urea, potassium dihydrogen phosphate, boron fertilizer and bio-fertilizer, stir evenly to obtain a suspension;

[0083] Step 3: Dry the suspension obtained in Step 2 in a dryer at 58°C. After drying, add starch and granulate using a fluidized bed granulator to obtain a particle size of 7-8 mm to produce core fertilizer. Then dry the core fertilizer at 60°C until the moisture content of the core fertilizer is less than or equal to 8%.

[0084] Step 4: Add the core fertilizer obtained in Step 3 and polylactic acid to the coating equipment and stir at 120 rpm for 8 minutes. During stirring, spray water at 6% of the mass of polylactic acid into the coating equipment using a spray device to ensure that the polylactic acid adheres evenly to the surface of the core fertilizer. After coating, place it in a drying oven at 45°C and dry for 1.5 hours. This yields a slow-release fertilizer specifically for saline-alkali land, labeled as #2 slow-release fertilizer for saline-alkali land.

[0085] Example 7

[0086] This embodiment provides a slow-release fertilizer specifically for saline-alkali land and its preparation method.

[0087] In this embodiment, the slow-release fertilizer for saline-alkali land includes, by weight, 90 parts of No. 3 bio-fertilizer, 18 parts of humic acid, 5 parts of manganese sulfate, 8 parts of ferrous ammonium sulfate, 6 parts of zinc sulfate, 5 parts of calcium magnesium phosphate fertilizer, 17 parts of urea, 10 parts of potassium dihydrogen phosphate, 5 parts of boron fertilizer, 13 parts of starch, and 18 parts of polylactic acid.

[0088] The preparation method of the above-mentioned slow-release fertilizer for saline-alkali land in this embodiment includes the following steps:

[0089] Step 1: Weigh all materials according to the component mass proportions in the example.

[0090] Step 2: Thoroughly mix fulvic acid, manganese sulfate, ferrous ammonium sulfate, zinc sulfate, calcium magnesium phosphate fertilizer, urea, potassium dihydrogen phosphate, boron fertilizer and bio-fertilizer, stir evenly to obtain a suspension;

[0091] Step 3: Dry the suspension obtained in Step 2 in a dryer at 60°C. After drying, add starch and granulate using a fluidized bed granulator to obtain a particle size of 4-5 mm to produce core fertilizer. Then dry the core fertilizer at 60°C until the moisture content of the core fertilizer is less than or equal to 8%.

[0092] Step 4: Add the core fertilizer obtained in Step 3 and polylactic acid to the coating equipment and stir at 150 rpm for 5 minutes. During stirring, spray water at a concentration equal to 6% of the polylactic acid's mass into the coating equipment using a spray device to ensure the polylactic acid adheres evenly to the surface of the core fertilizer. After coating, place it in a drying oven at 50°C and dry for 1 hour. This yields a slow-release fertilizer specifically for saline-alkali land, labeled as #3 slow-release fertilizer for saline-alkali land.

[0093] Comparative Example 6

[0094] The only difference between this comparative example and Example 7 is that the No. 3 bio-fertilizer was replaced with the No. 1 contrast agent bio-fertilizer; all other conditions were the same, resulting in a slow-release fertilizer specifically for saline-alkali land. It is labeled as the No. 1 contrast agent for slow-release fertilizer specifically for saline-alkali land.

[0095] Comparative Example 7

[0096] The only difference between this comparative example and Example 7 is that the No. 3 bio-fertilizer was replaced with the No. 2 contrast agent bio-fertilizer; all other conditions were the same. The resulting slow-release fertilizer for saline-alkali land was labeled as No. 2, the contrast agent for slow-release fertilizer for saline-alkali land.

[0097] Comparative Example 8

[0098] The only difference between this comparative example and Example 7 is that the No. 3 bio-fertilizer was replaced with the No. 3 contrast agent bio-fertilizer; all other conditions were the same, resulting in a slow-release fertilizer specifically for saline-alkali land. It is labeled as the No. 3 slow-release fertilizer contrast agent for saline-alkali land.

[0099] Comparative Example 9

[0100] The only difference between this comparative example and Example 7 is that the No. 3 bio-fertilizer was replaced with the No. 4 contrast agent bio-fertilizer; all other conditions were the same. The resulting slow-release fertilizer for saline-alkali land was labeled as No. 4, the contrast agent for slow-release fertilizer for saline-alkali land.

[0101] Comparative Example 10

[0102] The only difference between this comparative example and Example 7 is that the No. 3 bio-fertilizer was replaced with the No. 5 contrast agent bio-fertilizer; all other conditions were the same, resulting in a slow-release fertilizer specifically for saline-alkali land. The No. 5 contrast agent is labeled as "Slow-Release Fertilizer Specific for Saline-Alkali Land".

[0103] Test case

[0104] This test case is a test experiment on the application effect of different slow-release fertilizers for saline-alkali land.

[0105] Experimental location: Saline-alkali land in Zhoushan, Zhejiang Province. The tested soil was severely alkaline, with a pH of 9.1, a salt content of 0.39%, and an organic matter content of 0.85%.

[0106] Test plant: rice.

[0107] Fertilizers used in the experiment: Test group 1 was given No. 1 slow-release fertilizer for saline-alkali land, test group 2 was given No. 2 slow-release fertilizer for saline-alkali land, and test group 3 was given No. 3 slow-release fertilizer for saline-alkali land; control group 1 was given No. 1 slow-release fertilizer for saline-alkali land, control group 2 was given No. 2 slow-release fertilizer for saline-alkali land, control group 3 was given No. 3 slow-release fertilizer for saline-alkali land, control group 4 was given No. 4 slow-release fertilizer for saline-alkali land, control group 5 was given No. 5 slow-release fertilizer for saline-alkali land, and the blank control group (CK) was given water.

[0108] The experimental area was randomly divided into 9 plots, with 3 replicates for each treatment. The fertilizer application rate was the same for both the test and control groups, at 110 kg / mu. Other field management practices were standard. At harvest, the yield of each group was measured and recorded. Soil organic matter content, pH value, and soil salinity were also tested. The test results are shown in Table 1.

[0109] Table 1. Statistical results of crop yields and soil improvement effects of different fertilizers on saline-alkali land.

[0110]

[0111] Table 1 shows that the rice yield of the 1#-3# saline-alkali land-specific slow-release fertilizer was significantly higher than that of the control group, the 1#-5# saline-alkali land-specific slow-release fertilizer, and the blank control group. Among them, the 2# experimental group had the highest yield, reaching 503.72 kg / mu, while the blank control group only yielded 409.35 kg / mu, indicating that the saline-alkali land-specific slow-release fertilizer provided by this invention can effectively increase rice yield in saline-alkali land. Although the 4# and 5# control groups also improved rice yield, the results were far lower than those of the 1#-3# saline-alkali land-specific slow-release fertilizer, indicating that the synergistic effect of multiple microorganisms in the compound fermentation seed liquid of specific strains provided by this invention improves crop yield.

[0112] The soil organic matter content of experimental groups 1-3, which were treated with the 1-3# slow-release fertilizer specifically for saline-alkali land, was significantly higher than that of the control group and the blank control group. In particular, the soil organic matter content of experimental group 2 reached 1.25%, while the blank control group only had 0.83%. This indicates that the slow-release fertilizer for saline-alkali land of the present invention can increase soil organic matter content and improve soil fertility. This may be related to the specific strains provided by the present invention, mixed in a specific ratio, fermenting agricultural waste rich in organic matter and nutrients such as rice straw, corn straw, peanut shells, and livestock and poultry manure, providing rich organic fertilizer to the soil, increasing soil organic matter content, improving soil structure and aeration, and promoting the synergistic effect of soil microbial reproduction and activity.

[0113] In experimental groups 1-3, the soil pH values ​​of the soils treated with the 1-3# slow-release fertilizer for saline-alkali land were all lower than those of the control group and the blank control group, and were closer to neutral. Among them, experimental group 2 had a soil pH of 8.73, showing the largest pH reduction, and was the best slow-release fertilizer for saline-alkali land. This indicates that the slow-release fertilizer for saline-alkali land of this invention can effectively reduce the pH value of saline-alkali soil and improve soil acidity and alkalinity.

[0114] In experimental groups 1-3, the soil salinity of the soil treated with the 1-3# slow-release fertilizer for saline-alkali land was significantly lower than that of the control group and the blank control group. This indicates that the slow-release fertilizer for saline-alkali land provided by this invention effectively reduces the salinity of saline-alkali soil and alleviates the inhibitory effect of salinity on crop growth. This may be due to the synergistic effect between the specific strains provided by this invention. A better ecological balance achieved through specific mixing ratios allows for better utilization of fermentation substrates to convert into organic fertilizer. Furthermore, the rational combination of bio-fertilizer with nutrients such as humic acid, manganese sulfate, ferrous ammonium sulfate, zinc sulfate, calcium magnesium phosphate, urea, potassium dihydrogen phosphate, and boron fertilizer provides comprehensive nutrient supply to crops. Polylactic acid, as a coating material, can control the nutrient release rate, allowing for slow release of fertilizer nutrients to meet the needs of crops at different growth stages, improving fertilizer utilization, and reducing nutrient loss. Simultaneously, the coating material also protects the strains in the microbial fertilizer to a certain extent, prolonging the microbial activity time.

[0115] In summary, the test results of this embodiment show that the slow-release fertilizer for saline-alkali land prepared using agricultural waste significantly increases rice yield in saline-alkali land, increases soil organic matter content, and reduces soil pH and salinity, demonstrating a good improvement effect on saline-alkali soil. Compared with single microbial fertilizers or fertilizers composed of different microorganisms, the bio-fertilizer prepared by fermenting specific compound seed liquid and agricultural waste using this invention, combined with humic acid, various trace element fertilizers, urea, potassium dihydrogen phosphate, boron fertilizer, and a biodegradable coating material, results in a significant improvement effect on saline-alkali soil.

[0116] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for preparing special fertilizer for saline-alkali land using agricultural waste, characterized in that, Includes the following steps: S1. Preparation of compound fermentation seed liquid: Halophilic Pseudomonas aeruginosa Halopseudomonas salina With Bacillus subtilis Bacillus subtilis With Bacillus megaterium Bacillus megaterium The seed cultures were mixed at a mass ratio of 1-3:1-3:1-3 to prepare a compound fermentation seed culture, wherein the halophilic Pseudomonas bacteria... Halopseudomonas salina The accession number is CGMCC 1.12482, and the Bacillus subtilis described therein is... Bacillus subtilis The accession number is CGMCC 1.2416, Bacillus megaterium. Bacillus megaterium Its accession number is CGMCC 1.6721; S2. Preparation of microbial fertilizer fermentation substrate: After drying agricultural waste, it is crushed to a particle size of 0.5-2mm to obtain microbial fertilizer fermentation substrate. The agricultural waste includes rice straw, corn straw, peanut shells and livestock and poultry manure. S3, Solid-state fermentation: The microbial fertilizer fermentation substrate prepared in S2 is mixed with water at a mass ratio of 1:1, and the compound fermentation seed liquid prepared in S1 is added. The amount added is 9%-12% of the total mass of the solid-state fermentation culture medium. Fermentation is carried out at 28-32℃ for 9-12 days to obtain bio-fertilizer. S4. Preparation of fertilizer suspension: The bio-fertilizer obtained in S3 is mixed with humic acid, manganese sulfate, ferrous ammonium sulfate, zinc sulfate, calcium magnesium phosphate, urea, potassium dihydrogen phosphate and boron fertilizer, and stirred evenly to obtain fertilizer suspension. S5. Granulation and coating: After drying the suspension, it is mixed with starch and granulated using a fluidized bed granulator to obtain core fertilizer. Then, it is coated with polylactic acid to obtain slow-release fertilizer for saline-alkali land.

2. The method according to claim 1, characterized in that, The halophilic Pseudomonas aeruginosa in the compound fermentation seed liquid Halopseudomonas salina With Bacillus subtilis Bacillus subtilis With Bacillus megaterium Bacillus megaterium The mass ratio of the seed liquid was 2:1:

3.

3. The method according to claim 1, characterized in that, The agricultural waste is based on a total mass of 10 parts, including: 1-2 parts rice straw, 1-3 parts corn straw, 1-2 parts peanut shells, and 1-2 parts livestock and poultry manure.

4. The method according to claim 1, characterized in that, In step S4, by weight, the following are included: 80-90 parts of bio-fertilizer, 18-21 parts of humic acid, 5-6 parts of manganese sulfate, 8-12 parts of ferrous ammonium sulfate, 6-8 parts of zinc sulfate, 5-9 parts of calcium magnesium phosphate fertilizer, 17-21 parts of urea, 10-13 parts of potassium dihydrogen phosphate, and 5-8 parts of boron fertilizer.

5. The method according to claim 1, characterized in that, In step S5, the particle size of the granulated core fertilizer is 4-8 mm, and the moisture content of the core fertilizer is ≤8%.

6. The method according to claim 1, characterized in that, In step S5, the drying temperature after coating is 40-50℃, and the drying time is 1-2 hours.

7. A slow-release fertilizer specifically for saline-alkali land, characterized in that, It is prepared by the method described in any one of claims 1-6.

8. The application of the slow-release fertilizer for saline-alkali land as described in claim 7 in increasing crop yields in saline-alkali land.

9. The application of the slow-release fertilizer for saline-alkali land as described in claim 7 in the improvement of saline-alkali land soil.

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