Method for improving soil through microbial agent secondary compost mushroom bran

Abstract

The invention relates to the field of soil improvement. The invention relates to a method for improving soil by secondarily composting mushroom bran with a microbial agent, which comprises the following steps of: composting the original mushroom bran through two steps of natural fermentation and strain addition fermentation, and improving the properties of the mushroom bran, so that the improved mushroom bran can change the physicochemical properties and microbial community structure of the soil to promote the growth of nursery stocks (especially pinus sylvestris).

Description

Technical Field

[0001] The present invention relates to the field of soil improvement. Background Art

[0002] Scots pine occupies an important position in afforestation tree species in arid and semi-arid areas. Fertilizers and pesticides need to be added during the seedling raising process to ensure the good growth of Scots pine. However, long-term application of fertilizers and pesticides will lead to the destruction of soil physical and chemical properties, change the soil microbial structure, and cause soil degradation; making Scots pine grow slowly and susceptible to diseases. In recent years, many studies have shown that the study of new soil conditioners has become an effective strategy to overcome soil degradation and improve seedling growth.

[0003] Mushroom bran is an agricultural waste composed of residual fungal mycelium, decomposed lignocellulose, various nutritious organic matter and active enzymes. Irrational treatment of mushroom bran will not only cause waste of resources, but also affect the ecological environment. At present, composting is one of the most effective technologies for treating and decomposing mushroom bran. Composting can kill harmful microorganisms and insect eggs, and improve the physical and chemical properties of mushroom bran. At present, using mushroom bran as a soil conditioner can improve the physical and chemical properties of the soil, accelerate the fixation of soil nutrients and the formation of aggregates; Zanella et al. found that mushroom bran has a better effect on long-cycle crop improvement, which may be due to the longer mineralization time of secondary metabolites and the slow release of nutrients. Hanafi, FHM et al. used suitable beneficial microorganisms to treat mushroom bran, which can improve the nutrition and active substances in mushroom bran, thereby improving soil quality and environmental safety.

[0004] Soil microorganisms play an important role in soil energy material cycle and crop disease control through the decomposition of organic matter and the fixation of elements. Many studies have shown that the application of mushroom husk soil conditioner increases soil diversity and produces antimicrobial peptides with disease resistance, thereby improving the disease resistance of plants; Yu, Y. et al. used mushroom husk compost to replace chemical fertilizers. The beneficial microorganisms in the husk can increase vegetable or grain yields and improve soil and product quality. The bacteria-soil-plant mutual system can inhibit plant diseases; Li, X applied mushroom husk to the soil. Due to the large number of microorganisms distributed in the rhizosphere, the plants were encouraged to secrete a large number of growth enzymes, growth hormones and other plant regulators, which promoted the growth and development of the root system.

[0005] In the prior art, such as patents CN202210061883.1, CN201810459338.1, and CN201611242977.X, the mushroom bran is fermented for the second time. However, various organic and inorganic substances need to be added during the fermentation process to assist the fermentation of the mushroom bran, and the product after fermentation cannot improve the soil. Summary of the invention

[0006] The technical problem to be solved by the present invention is: how to process mushroom dregs to obtain a better soil conditioner, in particular to obtain a soil conditioner suitable for planting Pinus sylvestris var. mongolica.

[0007] The technical solution adopted by the present invention is: a method for improving soil by secondary composting of bacterial bran with microbial agents, which is characterized by the following steps: Step 1, primary composting (natural fermentation), crushing and sieving the dried original fungus bran to obtain dry fungus bran with a particle size of less than 0.5 cm, placing the dry fungus bran in a composting tank, adding water to make the moisture content of the fungus bran 50-70% by mass, maintaining the temperature at 50-70°C, ventilating once every 15 minutes, and fermenting for more than 24 hours; Step 2, secondary composting (fermentation with bacterial strains), adding bacterial strains to the fermented fungus bran in step 1, wherein the bacterial strains account for 0.8-1.2% of the mass of the dry fungus bran, maintaining the temperature at 30-40°C, ventilating once every 15 minutes, and fermenting for more than 24 hours, wherein the bacterial strains are a mixed strain of Bacillus subtilis, Nitrogen-fixing Bacillus nitricola and Bacillus colloidus; Step 3: Mix the secondary composted fungus residue with soil for planting Pinus sylvestris var. mongolica.

[0008] The mass ratio of Bacillus subtilis, Azotobacter fusca and Bacillus colloids in the mixed bacteria is (0.9-1.1): (0.9-1.1): (0.9-1.1).

[0009] When the secondary composted fungus residues are mixed with soil for planting Pinus sylvestris var. mongolica, the volume ratio of the fungus residues is 1-100%.

[0010] The beneficial effect of the present invention is that the present invention improves the properties of fungus stalks through secondary composting by natural fermentation and fermentation with added bacteria, and the improved fungus stalks can change the physical and chemical properties of the soil and the microbial community structure to promote the growth of seedlings (especially Pinus sylvestris var. mongolica). BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a comparison diagram of bulk density of 8 comparative experiments of the present invention; Figure 2 It is the conductivity comparison diagram of 8 comparative experiments of the present invention; Figure 3 It is the pH comparison diagram of 8 comparative experiments of the present invention; Figure 4 This is a comparison diagram of stem diameters from eight comparative experiments of the present invention; Figure 5 This is a comparison chart of the number of blades in 8 comparative experiments of the present invention; Figure 6 It is a comparison diagram of plant heights of 8 comparative experiments of the present invention. DETAILED DESCRIPTION

[0012] The test site is located in Wucheng Forest Farm of Guandishan State Forestry Administration, Shanxi Province, China (37°23~37°32′n, 111°24′~111°36′e). The forest farm is located between 1300 and 2008 meters above sea level, with a hilly terrain. The climate is a typical subtropical monsoon climate, with an annual precipitation of less than 500 mm, an annual average temperature of 4 to 6°C, an annual average frost-free period of 120 days, a daily average temperature of ≥10°C, and an effective accumulated temperature of 2500 to 3000°C. The soil physical and chemical properties are: pH 6.31, EC 0.61, TN 1.65 g kg -1 ,TP 0.58 g kg -1 ,TK 10.33g kg -1 .

[0013] The original mushroom bran was made of shiitake mushroom bran (by mass percentage, 85% sawdust, 12-14% wheat bran, 1-1.5% gypsum, and 0.1-0.2% compound fertilizer) purchased from a shiitake mushroom production workshop in Yangqu County, Shanxi Province.

[0014] Bacillus subtilis, brown spherical nitrogen-fixing bacteria, and Bacillus colloidus were purchased from the China Industrial Microbiological Culture Collection Center (CICC). Of course, Bacillus subtilis, brown spherical nitrogen-fixing bacteria, and Bacillus colloidus strains produced in other places can also be used. The chemical reagents used were purchased from Aladdin Reagent Company. The purchased strains were first expanded in liquid culture and cultured at 30°C for 1-3 days. Culture medium: Bacillus subtilis (LB culture medium): tryptone: 10.0g / L, yeast extract powder: 5.0g / L, NaCl: 10.0g / L, pH7.0-7.1; brown spherical nitrogen-fixing bacteria and Bacillus colloidus:, KH2PO4: 0.4 g / L, K2HPO 4: 0.1 g / L, Sodium D-gluconate: 5.0 g / L, MgSO4: 0.2 g / L, NaCl: 0.1g / L, CaCl2: 0.02g / L, FeCl3: 0.01g / L, Yeast extract powder: 0.8g / L, Na2MoO4·2H2O: 0.002 mg / L, pH6.8-7.0.

[0015] In the embodiment, 8 comparative experiments were designed.

[0016] (1) The mushroom residue was not composted (CK1), and the original mushroom residue was used directly.

[0017] (2) Soil (CK2): original soil was used directly.

[0018] (3) One-time composting (B1): only one natural fermentation composting is carried out.

[0019] (4) Secondary composting (C1) uses two steps of composting: natural fermentation and fermentation with added bacteria, without adding bacteria.

[0020] (5) Secondary composting (C2) uses two steps of composting: natural fermentation and fermentation with added bacteria, and the bacteria used is Bacillus subtilis.

[0021] (6) Secondary composting (C3) uses two steps of composting: natural fermentation and fermentation with added bacteria, and the bacteria used are brown coccus nitrogen-fixing bacteria.

[0022] (7) Secondary composting (C4) uses two steps of composting: natural fermentation and fermentation with added bacteria, and the bacteria used are Bacillus subtilis.

[0023] (8) Secondary composting (C5) uses two steps of composting: natural fermentation and fermentation with added bacteria. The bacteria are Bacillus subtilis, Nitrogen-fixing bacteria, and Bacillus mucilaginosus mixed in a mass ratio of 1:1:1.

[0024] Each of the above comparisons was repeated 5 times to avoid single unexpected (environmental) influences.

[0025] In all comparative experiments, the dried original fungus bran was crushed and sieved to obtain a dried fungus bran with a particle size of less than 0.5 cm, and in experiment CK1, the original fungus bran was directly used (the dried original fungus bran was crushed and sieved to obtain a dried fungus bran with a particle size of less than 0.5 cm). The soil involved was the garden soil of the same garden.

[0026] In a composting process, dry fungus bran is placed in a composting tank, water is added to make the moisture content of the fungus bran 50-70% by mass, the temperature is maintained at 50-70°C, ventilation is performed every 15 minutes, and fermentation is performed for more than 24 hours.

[0027] In the secondary composting, bacteria are added to the fermented fungus bran in step 1 (no bacteria are added in C1 and other process conditions are the same), the bacteria are 0.8-1.2% of the mass of the dry fungus bran, the temperature is maintained at 30-40°C, ventilation is performed every 15 minutes, and fermentation is performed for more than 24 hours. The bacteria are a mixed bacteria of Bacillus subtilis, brown spherical nitrogen-fixing bacteria and Bacillus mucilaginosus.

[0028] The secondary composting experiment was divided into two steps. The first step was to compost the original fungus residues for the second time. After composting, the fungus residues were mixed with garden soil in equal proportions (mass ratio); the second step was to use the fungus residues mixed with garden soil as soil to plant Pinus sylvestris seedlings. After composting, the physical and chemical properties of the soil in each treatment were measured. After planting, the growth of the seedlings and the microbial composition and structure of the soil were analyzed.

[0029] The composting of mushroom bran is divided into two stages: the first composting is without adding composting bacteria, and the mushroom bran is aerobically composted under the action of original microorganisms, and the composting temperature is 55℃; the second composting is adding different composting bacteria and controlling the composting temperature at 34℃.

[0030] Composting process: First, the dried fungus bran is crushed and sieved (particle size (φ) < 0.5 cm), and water is added until the moisture content of the fungus bran is about 60%; then the fungus bran is placed in a 10L composting tank, intermittently ventilated (200L / 15min), and the composting time is determined according to the temperature (the higher the temperature, the shorter the composting time), and the first composting is completed. For the second composting, the composting bacteria are inoculated at a 1% inoculation rate into the fungus bran after the first composting, and the temperature is controlled below 35°C. The rest of the method is the same as the first composting. The composted fungus bran is mixed with the soil in equal proportions. In this embodiment, the composting is carried out for 36 hours.

[0031] Select healthy seedlings with intact root systems and no pests and diseases and plant them in nutrient pots. No fertilizer or pesticides are added during the planting period. After the growth stops in the current year, the seedling characteristics are measured.

[0032] Before planting seedlings, select the surface, middle and bottom layers of the soil matrix for sampling. The sampling method adopts a triangular cross-type, 100g per portion, mix evenly, and repeat 3 times; after natural air drying, remove impurities. Then crush and dry in the sun, store at 4°C for soil physical and chemical property determination. After planting, collect rhizosphere soil with a brush, freeze and store in liquid nitrogen at -80°C for soil rhizosphere microbial determination.

[0033] Soil bulk density, total porosity, and water-holding pores were determined as follows: a fixed volume (V) of matrix was placed in a container of fixed mass (W1), and its total weight was weighed as W2. Water was added to the container until no more water was absorbed, and the weight was W3. A hole was dug at the bottom of the container to drain the water until all the water seeped out, which took about 10 hours (W4). Bulk density = (W2-W1) / W1, total porosity = ((W3-W1)-(W2-W1) / V×100%, water-holding pores = (W4-W2) / V×100%, and the total porosity minus the water-holding pores was the exhaust porosity. Soil pH and electrical conductivity (Electronical conductivity) were determined according to the method of Chen et al. (Chen M, Huang Y, Liu H, Xie S, Abbas F (2019a) Impact of different nitrogen source on the compost quality and greenhouse gas emissions during compostingof garden waste. Process Saf Environ Prot 124:326–335). Conductance, EC value): Extraction solution preparation (sample 10g, add 50ml DI to mix evenly, shake (175rpm, 40min) and filter to obtain the extract), then use pH meter (PB-10, Sartorius, Germany) and conductivity meter (DDS-11A, Leici, China) to determine. Total organic carbon (TOC) was determined by permanganate method, total nitrogen (TN) was determined by Kjeldahl nitrogen analyzer (SPAD 502, KONIC MINOLA, Japan); total potassium (TK) was determined by flame spectrophotometer (6400A, rainbow, China); total phosphorus (TP) was determined by ammonium molybdate colorimetric method. The alkaline nitrogen (alkaline N) content was determined by 2g sodium hydroxide hydrolyzing H3BO3 in the soil to adsorb NH3. The alkaline nitrogen (alkaline N) content was determined by 2g sodium hydroxide hydrolyzing H3BO3 in the soil to adsorb NH3. The content of effective potassium was determined by ammonium acetate extraction method, specifically 1 mol L − 1 The available potassium (available K) was extracted with CH3COONH4 (1:10, w:v) and determined by atomic absorption spectrometry. The available phosphorus (available P) in the soil was determined by the Olsen method.

[0034] After the growth stopped that year, 50 seedlings were randomly selected from each treatment to measure their growth status. The measured values ​​mainly included seedling height, ground diameter, height-to-diameter ratio, diameter-to-root ratio, seedling growth index and chlorophyll content. Seedling height (above soil surface) and root length were measured with a tape measure, and ground diameter (5 cm above the ground) and leaf length and width were measured with a vernier caliper. Height-to-diameter ratio = seedling height / ground diameter. Leaf chlorophyll content was measured by a chlorophyll meter (SPAD 502, KONIC MINOLA, Japan), and five parts of the branches (upper, upper middle, middle, lower middle, and lower) were selected for average measurement.

[0035] The total number of live bacteria in the soil was determined by the dilution plate live bacteria count method. Soil (10 g) was taken from each treatment and diluted with sterile water to different multiples (10 for bacteria, 10 for fungi, and 10 for actinomycetes). 3 , 10 2 , 10), inoculated into the corresponding culture medium (beef extract peptone medium for bacteria, Martin medium for fungi, and Gao's medium No. 1 for actinomycetes). Culture at 30℃ for 3-5 days, count the number of colonies, and express the count concentration as CFU g -1 .

[0036] Total DNA from soil was extracted using a soil genomic DNA extraction kit (DcP336, Tiangen Biochemical Technology Co., Ltd., Beijing) according to the manufacturer's instructions. DNA extracts were analyzed on a 1.2% agarose gel, and DNA concentration, purity, and integrity were determined using a NanoDropND-2000 UV-visible spectrophotometer (Thermo Scientific, Wilmington, DE, USA). To determine changes in microbial diversity, bacterial-specific primers 338F (5′-ACTCCTACGGGAGGCAGCAG-3′) and 806R were used. The V3-V4 hypervariable region of fungi was amplified by PCR using primers ITS1 (5′-CTTGGTCATTTAGAGGAAGTAA-3′) and ITS2 (5′-TGCGTTCTTCATCGATGC-3′).

[0037] The MiSeq library was constructed using Illumina, and the sequences of the microbial DNA fragments were determined, and the sequencing was completed by the Chinese Science Compass Testing Platform.

[0038] The raw sequence data were decomposed, reused, identified, merged, read, and filtered. QIIME 2 software was used to denoise 97% of the sequences and cluster the sequences into opertional taxonomic units (OTUs). Alpha diversity indices (Chao1, Shannon, and Simpson) were calculated using QIIME; beta diversity was evaluated using non-metric multidimensional scaling (NMDS) based on Bray-Curtis distance.

[0039] The results are as follows Effects of composting on the physical and chemical properties and nutrient content of fungus residues The color of the spores before composting was light brown, and after composting, the color of the spores was dark brown granules. The composting process had a significant effect on the physical properties of the spores, but the addition of different inoculants had little effect on it; as the composting progressed, the bulk density and water-holding pores showed an upward trend, while the total porosity and ventilation pores showed a downward trend. Compared with CK1, the bulk density and water-holding pores of the B1 treatment increased significantly by 0.53 and 4.82%, and the C1 to C5 treatments continued to increase significantly to 0.57-0.59 and 7.15%-8.97%; the total porosity and ventilation pores of the B1 treatment decreased significantly by about 4.02% and 26.30%. As for the chemical properties, the composting process had a significant effect on pH, EC value and TOC; but the type of inoculants had a slight difference in pH, EC value and TOC. The composting process caused the pH and EC values ​​to increase, and TOC to decrease. Compared with CK1 treatment, pH and EC values ​​of B1 treatment increased significantly to 5.74 and 0.63, and TOC decreased by 11.77%. After adding bacterial agents, pH and EC values ​​continued to rise to about 7.3 and 2.6. However, no significant differences were found among the treatments after different bacterial agents were added. Figure 1-Figure 3 shown.

[0040] Effects of Mushroom Waste on the Growth of Seedlings The application of added fungus husks can significantly promote plant growth, but the growth of seedlings varies with different microbial agents. The plant height and diameter of the C3 and C5 treatments were the highest among all treatments; the number of leaves in the C5 and C4 treatments was significantly higher than that in other control groups, and the chlorophyll content in the C5 treatment was the highest. Overall, the C5 treatment had the most significant effect on seedling growth, with its plant height, diameter, number of leaves and chlorophyll content increasing by 26.94%, 15.91%, 27.76% and 36.25% compared with CK2. Figure 4-Figure 6 shown.

[0041] Effects of mushroom residues on soil microbial biomass and diversity In this example, the number of culturable microorganisms in each treatment was greater for bacteria than for actinomycetes, followed by fungi; and after adding the fungus residue, the number of viable bacteria was significantly higher than that of CK2. However, there was a significant difference in the number of viable bacteria between the treatments C1 to C5, and the number of bacteria and fungi in C5 was significantly higher than that of the other treatments, which was 9.15× 10 6 CFU g −1 ; 4.84× 10 5 CFU g −1 The number of actinomycetes in C3 was the highest (37.57× 10 5 CFU g −1 ).

[0042] The α diversity of microorganisms between treatments included Chao1, which represents richness, and Shannon index (H'), which represents diversity. In bacterial α diversity, microbial agents significantly affected the diversity index between treatments. The richness (Chao1) of C1 treatment was not much different from that of CK2. The Chao1 and Shannon index of C2 to C5 increased by 2.56% to 26.81% and 16.58% to 36.34%. In fungal α diversity, the diversity index of C1 to C5 treatments was greater than that of CK2. C5 had the highest diversity index, and its Chao1 and Shannon index increased by about 149 and 2.28 compared with CK2. The differences in the composition of microbial communities in different treatments were evaluated by NMDS. The results showed that the addition of fungal bran with different agents had a significant effect on the distribution of soil microbial communities. All community structures showed that the bacterial and fungal communities of CK2 and other treatments were clearly separated along the NMDS 1 axis.

[0043] Effects of mushroom residues on soil microbial community composition There was no difference in the composition of bacteria at the phylum level, but the relative abundance of different treatments was different. In the CK2 treatment, Actinobacteria, Gemmatimonads, and Acidobacteria were significantly higher than those in other treatments, while Proteobacteria, Chloroflexi, and Bacteroidetes were significantly lower than those in other treatments. In addition, the phyla with the highest relative abundance in the C1, C2, C4, C3, and C5 treatments were Firmicutes, Chloroflexi, Actinobacteria, and Proteobacteria, respectively. Compared with the CK2 treatment, the composition and relative abundance of bacteria at the genus level changed; the dominant genus from C1 to C5 increased to Acinetobacter. With the addition of microbial agents, the relative abundance of Bacillus, Azotobacter, and Paenibacillus was significantly higher in C2 and C5, C3 and C5, and C4 and C5 than in other treatments.

[0044] As for fungi, the six fungal groups with the highest relative abundance at the phylum level were Ascomycota, Basidiomycota, Aphelidiomycot, Chytridiomycot, and Mortierellomycota. Adding fungus bran had a significant effect on the composition of soil fungal communities, but it affected the relative proportions of each phylum. The relative abundance of Ascomycota and Basidiomycota remained basically unchanged; the relative abundance of Basidiomycota and Chytridiomycota in the C5 treatment was the highest. The addition of bacterial bran significantly changed the composition and relative abundance of genera, and the relative abundance of each treatment was different depending on the added bacterial species; Mycothermus, Sphaerulina, Brocchiosphaera, Cladosporium, Didymella and Fusarium became the dominant genera, with step-by-step ranges of 24.65%-32.97%, 4.17%-21.18%, 7.82%-18.91%, 4.27%-14.52% and 5%-20.62%.

[0045] Relationship between soil microbial community structure and physical and chemical properties The Spearman correlation coefficient between bacterial composition and soil factors showed that the genus vicinamibacteraceae under the phylum Acidobacteria was significantly negatively correlated with total phosphorus, total potassium, alkaline nitrogen and available phosphorus (P<0.05), A4b in the phylum Chloroflexi was significantly positively correlated with TK, AN and AP (P<0.01), and Paenibacillus in the phylum Firmicutes was significantly positively correlated with pH, ​​EC, total nitrogen and total phosphorus (P<0.05). In addition, it was found that the genus Azotobacter in the phylum Proteobacteria was strongly affected by total nitrogen (positive, P<0.05), total phosphorus (positive, P<0.05) and alkaline nitrogen (positive, P<0.05); it was also found that Sphingomonas in the suborder α-Proteobacteria was strongly affected by TP, TK, AN, AP and AK (negative, P<0.05). In the experiment, it was found that mycothermus in Mucor was significantly positively correlated with soil nutrients (TN, TP, TK, AN and AK) (P<0.05), and soil nutrients had a significant effect on the relative abundance of Fusarium in Ascomycota (negative, P<0.05).

[0046] The results of SEM analysis showed that, except for the horizontal diameter of the plant, the growth of the plant was positively correlated with the chao1 index of bacteria; in fungal diversity, except for the chlorophyll content, the growth was positively correlated with the chao1 index of fungi. The results showed that the richness of soil microorganisms was of great significance to the growth of plants. The application of soil conditioners changed the physical and chemical properties of the soil, increased the nutrient content of the soil, and promoted the growth of plants. The use of fungus residues can promote the colonization and growth of beneficial rhizosphere microorganisms, thereby promoting the growth of plants. The chao1 index of bacteria and fungi was negatively correlated with EC. The increase in EC value will lead to an increase in soil salinity, which is not conducive to plant growth. This is consistent with the previous research results of Shen that the increase in soil salt is not conducive to the increase of microbial communities. Therefore, the application of SMS soil conditioner can reduce the EC value of the soil, increase the diversity of soil microorganisms, and promote plant growth. In addition, alkaline nitrogen is negatively correlated with the chao1 of bacteria and fungi, which is also confirmed by the research results in C. Wang. Therefore, adding SMS soil conditioner can directly or indirectly regulate soil microbial diversity by changing the physical and chemical properties and nutrient content of the soil, thereby improving plant growth.

[0047] When different microbial agents were added to the fungus sludge, the soil bulk density and water-holding pores increased significantly, while the total porosity, aeration space and TOC decreased significantly. The pH and EC values ​​increased to about 7.3 and 2.6 ms▪cm -1 , no significant difference was found between different microbial agents; the total nitrogen, total phosphorus, total potassium, alkaline nitrogen, available phosphorus and available potassium contents were relatively high after the mixed microbial agent treatment; the seedling height, ground diameter, leaf number and chlorophyll content were significantly higher than those of other treatments; these results confirmed that the mixed microbial agent can have a positive effect on soil physical and chemical properties and seedling growth after secondary composting. In addition, after the mixed microbial agent treatment, the fungal and bacterial biomass and diversity index of the sludge were significantly higher than those of the single microbial agent treatment, and the Proteobacteria, Bacteroidetes, Firmicutes and Basidiomycetes were also significantly enriched, and the corresponding nitrogen-fixing bacteria, Chrysecolinea, Bacillus and Vishniacozyma, Coprinopsis genera also increased. The above results show that mixed microbial agents are an effective way to improve soil through secondary composting. This study deepens our understanding of soil improvement with sludge and provides practical uses of sludge in soil conditioners. These insights can also help apply mushroom bran to improve soil degradation, reduce the use of chemical fertilizers and pesticides, and promote the development of a green ecological environment, and therefore have important ecological and economic significance.

[0048] Vecstaudza, D., Senkovs, M., Nikolajeva, V., Kasparinskis, R., Muter, O., 2017. Wooden biochar as a carrier for endophytic isolates. Rhizosphere 3,126–127 Shen , W. , Ni , Y. , Gao , N. , Bian , B. , Zheng , S. , Lin , X. , Chu , H. ,2016 . Bacterial community composition is shaped by soil secondarysalinization and acidification brought on by high nitrogen fertilizationrate. Appl. Soil Ecol. Rev. 108, 76–83

Claims

1. A method for improving soil by secondary composting of bacterial residues using a microbial agent, characterized in that Proceed as follows: Step 1, primary composting, crushing and sieving the dried original fungus bran to obtain dry fungus bran with a particle size less than 0.5 cm, placing the dry fungus bran in a composting tank, adding water to make the moisture content of the fungus bran 50-70% by mass, maintaining the temperature at 50-70° C., ventilating once every 15 minutes, and fermenting for more than 24 hours; Step 2, secondary composting, adding bacteria to the fermented fungus spores in step 1, the bacteria spores are 0.8-1.2% of the mass of the dry fungus spores, maintaining the temperature at 30-40°C, ventilating once every 15 minutes, and fermenting for more than 24 hours, wherein the bacteria spores are a mixed strain of Bacillus subtilis, brown spherical nitrogen-fixing bacteria and Bacillus colloidus; Step 3: Mix the secondary composted fungus residue with soil for planting Pinus sylvestris var. mongolica.

2. The method for improving soil by secondary composting of bacterial bran using a microbial agent according to claim 1, characterized in that: The mass ratio of Bacillus subtilis, Azotobacter fusca and Bacillus colloids in the mixed bacteria is (0.9-1.1): (0.9-1.1): (0.9-1.1).

3. The method for improving soil by secondary composting of bacterial bran using a microbial agent according to claim 1, characterized in that: When the secondary composted fungus residues are mixed with soil for planting Pinus sylvestris var. mongolica, the volume ratio of the fungus residues is 1-100%.

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