Method for improving survival rate of young poplar man-made forest in sandy and arid region and soil quality of forest land based on mycorrhizal symbiosis

Abstract

The invention provides a method for improving the survival rate of a young poplar man-made forest in a sandy and arid region and the soil quality of forest land based on mycorrhizal symbiosis, and belongs to the technical field of drought-resistant afforestation. The water-retaining agent provided by the invention is prepared from the following components in parts by mass: 60 to 80 parts of acrylic acid, 20 to 30 parts of humic acid, 10 to 15 parts of chitosan, 50 to 70 parts of a pH value regulator, 0.1 to 1 part of N, N-methylene bisacrylamide and 0.5 to 5 parts of potassium persulfate. The water-retaining agent prepared by the invention is high in repeated water absorption capacity and strong in fertilizer-retaining capacity, and has wide development prospects in the aspects of agriculture and forestry water retention, soil fertility increasing, soil physicochemical property improvement and the like. The prepared water-retaining agent is mixed with biochar, organic fertilizer, ectomycorrhiza liquid and soil according to a certain proportion, then the mixture is buried in a fertilization ditch, ectomycorrhiza and poplar seedlings are symbiotic, the absorption area of root systems is increased, the soil environment is improved, the survival rate of the poplar seedlings can be effectively increased, and the physicochemical property of the soil is improved.

Description

Technical Field

[0001] The invention relates to the technical field of drought-resistant afforestation, and in particular to a method for improving the survival rate of young poplar plantations in sandy and arid areas and the quality of forest soil based on mycorrhizal symbiosis. Background Art

[0002] Shelterbelts are forests, trees, and shrublands whose primary purpose is to protect against natural disasters, regulate the climate, maintain ecosystem functions, and restore ecological productivity. Poplars are the most important timber and shelterbelt species, and are of great strategic significance in national security, timber security, afforestation, and the "Three Norths Project." However, in the arid regions of northern my country, both in spring and autumn, soil water scarcity, insufficient nutrients, large pores in sandy loam, high surface evaporation, and low soil microbial community richness lead to poor soil site quality, high water consumption of poplar trees, impeded root development, and low afforestation survival rates.

[0003] Mycorrhizal symbiosis has many positive effects on poplar growth: 1. Enhanced nutrient absorption: Mycorrhizal fungi form a symbiotic relationship with poplar roots, helping the trees more efficiently absorb water and nutrients from the soil, particularly nutrients like phosphorus and nitrogen. This relationship can significantly increase poplar growth rate and biomass. 2. Improved stress tolerance: Mycorrhizal symbiosis can enhance poplars' resistance to adverse environmental factors such as drought, salinity, and pests and diseases. Mycorrhizal fungi improve the plant's water use efficiency and enhance its ability to adapt to adverse conditions. 3. Promoted root development: The presence of mycorrhizal fungi promotes the growth and development of poplar roots, increasing their surface area and thus improving their ability to absorb water and nutrients. 4. Improved soil quality: Mycorrhizal symbiosis can also improve soil structure and fertility, promote soil microbial diversity, and ultimately enhance overall ecosystem health. Despite the beneficial effects of mycorrhizal symbiosis, the use of afforestation land can also be hampered by insufficient water and low nutrient content in sandy, arid soils, which can hinder the development of mycorrhizae and plant roots.

[0004] Water-retaining agents (SRAs) are highly absorbent resins capable of absorbing hundreds of times their own weight in water. They act as miniature reservoirs in the soil, absorbing and storing water during rainfall or irrigation, and releasing it during droughts. These properties have led to their widespread use in agriculture and forestry. They offer numerous benefits, including water conservation and drought resistance, soil and water conservation, soil improvement, fertilizer conservation and yield increase, improved afforestation survival rates, and wind and sand control. They hold broad application prospects in agricultural and forestry production, soil and water conservation, and desertification remediation, and are of significant practical significance to my country's ecological progress. There are many types of SRAs, the traditional type being polyacrylic acid-acrylamide. While these SRAs offer excellent water retention, they also suffer from poor reabsorption and limited fertilizer retention. In recent years, polyacrylic acid-starch and polyacrylic acid-cyclodextrin-based water-retaining agents have emerged to address the shortcomings of traditional water-retaining agents. However, while polyacrylic acid-starch-based water-retaining agents have improved their repeated water absorption capacity to a certain extent, their nutrient retention capacity remains limited. While polyacrylic acid-cyclodextrin-based water-retaining agents have improved their nutrient retention capacity, their repeated water absorption capacity needs further improvement. Therefore, it is necessary to develop a method based on mycorrhizal symbiosis to improve the survival rate and soil quality of young poplar plantations in sandy and arid regions. Summary of the Invention

[0005] In view of this, the present invention provides a method for improving the survival rate of young poplar plantations in sandy arid areas and the quality of forest soil based on mycorrhizal symbiosis, so as to solve the problem of low afforestation survival rate in arid areas.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for improving the survival rate of young poplar plantations in sandy and arid areas and the quality of forest soil based on mycorrhizal symbiosis, comprising the following steps:

[0008] S1. Dig a fertilizer trench around the poplar seedlings in the plantation;

[0009] S2. Mix the biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution, and soil, backfill the mixture into the fertilization trench, and water the mixture until the soil reaches 58-62% of its maximum water holding capacity.

[0010] The water-retaining agent comprises the following components in parts by mass: 60-80 parts of acrylic acid, 20-30 parts of humic acid, 10-15 parts of chitosan, 50-70 parts of pH regulator, 0.1-1 part of N,N-methylenebisacrylamide, and 0.5-5 parts of potassium persulfate.

[0011] Preferably, the mass ratio of the biochar, organic fertilizer, water retaining agent, ectomycorrhizal solution and soil is 20-30:100-200:10-20:5-10:50-100.

[0012] Preferably, the spore concentration in the ectomycorrhizal fungal liquid is 400 to 500 spores / mL.

[0013] Preferably, the fertilizer ditch is located at the outer edge of the vertical projection of the tree crown, and the depth of the fertilizer ditch is 30 to 40 cm and the width is 40 to 50 cm.

[0014] Preferably, the molecular weight of the humic acid is 3000-5000.

[0015] Preferably, the polymerization degree of the chitosan is 200-400.

[0016] Preferably, the pH adjustment comprises NaOH and / or KOH.

[0017] Preferably, the preparation of the water-retaining agent comprises the following steps:

[0018] (1) Grind chitosan and humic acid into powders of 70-80 μm;

[0019] (2) preparing a 25-35 wt% alkaline solution of NaOH or KOH, mixing acrylic acid with the alkaline solution in a ratio of 1 g: 1.6-2.2 mL, stirring and dissolving, to obtain solution 1;

[0020] (3) Chitosan and humic acid powders were mixed with solution 1, and the pH value was adjusted to neutral by adding alkaline solution dropwise to obtain solution 2;

[0021] (4) Add N,N-methylenebisacrylamide and potassium persulfate to solution 2, stir at 50-60°C for 2-3 hours, filter, dry the filter residue, and granulate to obtain the product.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects:

[0023] (1) The water-retaining agent prepared by the present invention has high repeated water absorption capacity and strong fertilizer retention capacity, and has broad development prospects in agricultural and forestry water conservation, soil fertilization, and improvement of soil physical and chemical properties.

[0024] (2) The "Reticulated Puffball" of the present invention is an ectomycorrhizal fungus that can promote the growth of mycorrhizal fungi, colonize the roots of poplar seedlings to form a mycorrhizal symbiotic structure, and promote plant growth; after the mycorrhiza is formed, the interaction between the mycorrhizal auxiliary bacteria and the mycorrhizal fungus-plant symbiont can improve the absorption and transport level of mineral nutrients by the poplar seedlings; in addition, the ectomycorrhiza can increase the absorption area of ​​the root system and enhance the root system's ability to absorb water and fertilizer. The secretions of the mycelium of the Reticulated Puffball can also granulate soil particles, improve the soil structure, and increase the survival rate of poplar seedlings in artificial forests.

[0025] (3) The water-retaining agent prepared by the present invention is mixed with biochar, organic fertilizer, ectomycorrhizal fungus liquid and soil in a certain proportion and then buried in the fertilizer ditch, which can effectively promote the survival rate of poplar seedlings and improve the physical and chemical properties of the soil. DETAILED DESCRIPTION

[0026] The invention provides a water-retaining agent, comprising the following components in parts by mass: 60-80 parts of acrylic acid, 20-30 parts of humic acid, 10-15 parts of chitosan, 50-70 parts of a pH regulator, 0.1-1 part of N,N-methylenebisacrylamide, and 0.5-5 parts of potassium persulfate.

[0027] In the raw materials for preparing the water-retaining agent of the present invention, the mass fraction of the acrylic acid is preferably 65 to 75 parts, more preferably 70 parts;

[0028] The mass fraction of the humic acid is preferably 23 to 28 parts, more preferably 25 parts;

[0029] The mass fraction of the chitosan is preferably 11 to 14 parts, more preferably 13 parts;

[0030] The mass fraction of the pH value adjusting agent is preferably 52 to 58 parts, more preferably 55 parts;

[0031] The mass fraction of the N,N-methylenebisacrylamide is preferably 0.3 to 0.8 parts, more preferably 0.5 parts;

[0032] The mass fraction of the potassium persulfate is preferably 1 to 4 parts, more preferably 2.5 parts.

[0033] The molecular weight of the humic acid of the present invention is 3000-5000, preferably 3500-4500, more preferably 4000; the degree of polymerization of the chitosan is 200-400, preferably 250-350, more preferably 300.

[0034] The pH value adjustment of the present invention includes NaOH and / or KOH.

[0035] The present invention also provides a method for preparing the water-retaining agent, comprising the following steps:

[0036] (1) Grind chitosan and humic acid into powders of 70-80 μm;

[0037] (2) preparing a 25-35 wt% alkaline solution of NaOH or KOH, mixing acrylic acid with the alkaline solution in a ratio of 1 g: 1.6-2.2 mL, stirring and dissolving, to obtain solution 1;

[0038] (3) Chitosan and humic acid powders were mixed with solution 1, and the pH value was adjusted to neutral by adding alkaline solution dropwise to obtain solution 2;

[0039] (4) Add N,N-methylenebisacrylamide and potassium persulfate to solution 2, stir at 50-60°C for 2-3 hours, filter, dry the filter residue, and granulate to obtain the product.

[0040] The present invention first grinds chitosan and humic acid into powder, wherein the particle size of the powder is 70-80 μm, preferably 72-78 μm, and more preferably 75 μm; then, NaOH or KOH is prepared into an alkaline solution, acrylic acid is mixed with the alkaline solution, and the mixture is stirred and dissolved to obtain a solution 1; the concentration of the alkaline solution is 25-35 wt%, preferably 28-32 wt%, and more preferably 30 wt%; and the mass volume ratio of the acrylic acid to the alkaline solution is 1 g:1.6-2.2 mL, preferably 1 g:1.8-2.0 mL, and more preferably 1 g:1.9 mL. In the present invention, chitosan and humic acid powder are mixed with solution 1, and an alkaline solution is continuously added dropwise to adjust the pH value to neutral to obtain solution 2. Then, N,N-methylenebisacrylamide and potassium persulfate are added to solution 2 to carry out a cross-linking reaction. After the reaction is completed, the solution is filtered, and the filter residue is dried and granulated to obtain the water-retaining agent. The temperature of the cross-linking reaction is 50-60°C, preferably 52-58°C, and more preferably 55°C. The cross-linking reaction time is 2-3 hours, preferably 2.2-2.8 hours, and more preferably 2.5 hours. The cross-linking reaction is accompanied by stirring. The present invention does not specifically limit the stirring speed, as long as it can ensure sufficient contact between the reactants. After the reaction is completed, the solution is filtered, and the filter residue is dried and granulated to obtain the water-retaining agent. The particle size of the water-retaining agent is 0.5-1 mm, preferably 0.6-0.8 mm, and more preferably 0.7 mm.

[0041] The present invention also provides a method for improving the survival rate and site quality of young poplar plantations in sandy and arid areas, comprising the following steps:

[0042] S1. Dig a fertilizer trench around the seedlings;

[0043] S2. Mix the biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution and soil, and backfill them into the fertilizer trench.

[0044] The fertilizer ditch is located at the outer edge of the vertical projection of the tree crown. The depth of the fertilizer ditch is 30 to 40 cm, preferably 32 to 38 cm, and more preferably 35 cm; the width is 40 to 50 cm, preferably 42 to 48 cm, and more preferably 45 cm. The length of the ditch is similar to the radius of the tree crown. When digging the fertilizer ditch in the present invention, damage to the roots should be avoided as much as possible.

[0045] The mass ratio of the biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution and soil is 20-30:100-200:10-20:5-10:50-100, preferably 22-28:120-180:13-17:6-9:60-90, and more preferably 25:150:15:8:80; the spore concentration in the ectomycorrhizal solution is 400-500 spores / mL.

[0046] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0047] The ectomycorrhiza of the present invention is "Lycoperdon perlatum".

[0048] Example 1

[0049] A water-retaining agent is prepared from the following components in parts by mass: 60 kg of acrylic acid, 20 kg of humic acid with a molecular weight of 3000-5000, 10 kg of chitosan with a degree of polymerization of 200-400, 50 kg of a pH regulator, 0.1 kg of N,N-methylenebisacrylamide, and 0.5 kg of potassium persulfate.

[0050] Preparation method:

[0051] (1) Grind chitosan and humic acid into powders of 70-80 μm;

[0052] (2) preparing a 25 wt% alkaline solution of NaOH or KOH, mixing acrylic acid with the alkaline solution at a ratio of 1 g: 1.6 mL, stirring and dissolving, to obtain Solution 1;

[0053] (3) Chitosan and humic acid powders were mixed with solution 1, and the pH value was adjusted to neutral by adding alkaline solution dropwise to obtain solution 2;

[0054] (4) Add N,N-methylenebisacrylamide and potassium persulfate to solution 2, stir at 50°C for 3 hours, filter, dry the filter residue, and prepare particles with a particle size of 0.5 to 1 mm.

[0055] Methods for improving the survival rate and soil quality of young poplar plantations in sandy and arid areas: dig a 40 cm deep and 50 cm wide fertilizer ditch at the outer edge of the vertical projection of the poplar seedling crown, mix biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution and soil in a mass ratio of 25:150:15:8:80, and backfill the mixture into the fertilizer ditch. The spore concentration of the ectomycorrhizal solution is 500 / mL.

[0056] Example 2

[0057] A water-retaining agent is prepared from the following components in parts by mass: 70 kg of acrylic acid, 25 kg of humic acid with a molecular weight of 3000-5000, 13 kg of chitosan with a degree of polymerization of 200-400, 60 kg of a pH regulator, 0.5 kg of N,N-methylenebisacrylamide, and 3 kg of potassium persulfate.

[0058] Preparation method:

[0059] (1) Grind chitosan and humic acid into powders of 70-80 μm;

[0060] (2) preparing a 30 wt% alkaline solution of NaOH or KOH, mixing acrylic acid with the alkaline solution at a ratio of 1 g: 2.0 mL, stirring and dissolving, to obtain Solution 1;

[0061] (3) Chitosan and humic acid powders were mixed with solution 1, and the pH value was adjusted to neutral by adding alkaline solution dropwise to obtain solution 2;

[0062] (4) Add N,N-methylenebisacrylamide and potassium persulfate to solution 2, stir at 55°C for 2.5 hours, filter, dry the filter residue, and prepare particles with a particle size of 0.5 to 1 mm.

[0063] Methods for improving the survival rate and soil quality of young poplar plantations in sandy and arid areas: dig a 40 cm deep and 50 cm wide fertilizer ditch at the outer edge of the vertical projection of the poplar seedling crown, mix biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution and soil in a mass ratio of 25:150:15:8:80, and backfill the mixture into the fertilizer ditch. The spore concentration of the ectomycorrhizal solution is 500 / mL.

[0064] Example 3

[0065] A water-retaining agent is prepared from the following components in parts by mass: 80 kg of acrylic acid, 30 kg of humic acid with a molecular weight of 3000-5000, 15 kg of chitosan with a degree of polymerization of 200-400, 70 kg of a pH regulator, 1 kg of N,N-methylenebisacrylamide, and 5 kg of potassium persulfate.

[0066] Preparation method:

[0067] (1) Grind chitosan and humic acid into powders of 70-80 μm;

[0068] (2) preparing a 35 wt% alkaline solution of NaOH or KOH, mixing acrylic acid with the alkaline solution at a ratio of 1 g: 2.2 mL, stirring and dissolving, to obtain Solution 1;

[0069] (3) Chitosan and humic acid powders were mixed with solution 1, and the pH value was adjusted to neutral by adding alkaline solution dropwise to obtain solution 2;

[0070] (4) Add N,N-methylenebisacrylamide and potassium persulfate to solution 2, stir at 60°C for 2 hours, filter, dry the filter residue, and prepare particles with a particle size of 0.5 to 1 mm.

[0071] Methods for improving the survival rate and soil quality of young poplar plantations in sandy and arid areas: dig a 40 cm deep and 50 cm wide fertilizer ditch at the outer edge of the vertical projection of the poplar seedling crown, mix biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution and soil in a mass ratio of 25:150:15:8:80, and backfill the mixture into the fertilizer ditch. The spore concentration of the ectomycorrhizal solution is 500 / mL.

[0072] Comparative Example 1

[0073] The difference from Example 1 is that starch is used instead of humic acid.

[0074] Comparative Example 2

[0075] The difference from Example 1 is that chitosan is replaced by cotton fiber.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that the mass of humic acid is 40 kg.

[0078] Comparative Example 4

[0079] The difference from Example 1 is that humic acid with a molecular weight of 3000-5000 is replaced by fulvic acid with a molecular weight of 300-1000.

[0080] Comparative Example 5

[0081] The difference from Example 1 is that the polymerization degree of chitosan is 50-100.

[0082] Comparative Example 6

[0083] The difference from Example 1 is that no ectomycorrhizal solution was added to the fertilization furrow.

[0084] Experimental Example 1. Water retention performance measurement

[0085] 1. Determination of water absorption rate

[0086] Water absorption rate is one of the key indicators of a water-retention agent's water retention performance. It reflects the maximum amount of water a water-retention agent can absorb, i.e., the ratio of the mass of water absorbed by the water-retention agent to its own mass. In this experimental example, the water absorption rate was measured in deionized water.

[0087] Determination method: Weigh a certain mass of dry water-retaining agent m1, put it into a beaker, add sufficient deionized water, wait for it to be fully absorbed for 6 hours, filter it with a standard mesh sieve (0.18mm) of known mass, filter it naturally for 10 minutes, then place it at an angle and filter it for another 10 minutes, weigh the gel mass m2, and then calculate the water absorption multiple according to the following formula, and repeat three times for each treatment.

[0088] Water absorption multiple = (m2-m1) / m1.

[0089] 2. Repeated water absorption capacity determination

[0090] The repeated water absorption capacity is determined by subjecting the water-retaining agent to a reversible reaction of water absorption, drying, reabsorption, and re-drying. To minimize the quality error of the water-retaining agent during this process, a cloth bag is used instead of a standard sieve for filtration when determining its water absorption rate.

[0091] Determination method: Put a certain mass of dry water-retaining agent into a small cloth bag of known mass, soak it in deionized water for 7 hours, take out the cloth bag, hang it and let it stand for 7 hours, wait for it to dry and weigh it once, then put it in an oven and dry it at 60℃ for 12 hours, until it is completely dried, take it out, and then repeat the above steps to let it absorb water repeatedly. Test the water absorption rate of different water-retaining agents after five repeated water absorption and drying, with three replicates for each treatment.

[0092] Repeated water absorption rate = water absorption multiple after repeated water absorption and drying / initial water absorption multiple × 100%

[0093] Table 1 Performance test results of water retaining agent

[0094] Group Water absorption ratio (g / g) Repeated water absorption rate (%) Example 1 652 89 Example 2 668 92 Example 3 660 90 Comparative Example 1 532 76 Comparative Example 2 585 83 Comparative Example 3 603 80 Comparative Example 4 573 78 Comparative Example 5 618 69

[0095] As shown in Table 1, the water-retaining agent prepared by the present invention has a high water absorption multiple and a high repeated water absorption rate. Comparative Examples 1 and 2 show that the water absorption multiple and repeated water absorption rate of the water-retaining agent decrease when humic acid is replaced by starch and chitosan is replaced by cotton fiber. Comparative Examples 3, 4, and 5 show that the water absorption multiple and repeated water absorption rate of the water-retaining agent decrease when the mass and molecular weight of humic acid or the degree of polymerization of chitosan is changed.

[0096] Experimental Example 2. Determination of seedling survival rate and soil physical and chemical properties

[0097] The experiment was conducted in June 2023 at the Heishan Experimental Base of the Liaoning Poplar Research Institute. Nine groups were assigned to the experiment using a randomized block design. The poplar plantation was divided into several plots, each containing 100 poplar seedlings. Groups were separated by at least 5 m. A 40 cm deep and 50 cm wide fertilization trench was dug along the outer edge of the vertical projection of the poplar seedling canopy. Biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution, and soil were mixed in a mass ratio of 25:150:15:8:80 and backfilled into the trench. The ectomycorrhizal solution contained 500 spores / mL. A control group without water-retaining agent was used. Each treatment was replicated three times. Seedling survival was measured in August of the following year. Equal amounts of soil samples were collected at the 15 cm soil layer from five randomly selected locations within each plot for physical and chemical property measurements. The average results are shown in Table 2.

[0098] Table 2 Survival rate of seedlings and soil physical and chemical properties in each group

[0099]

[0100] As shown in Table 2, the water-retaining agent prepared in the present invention exhibits excellent fertilizer retention, surpassing that of the comparative example. This is because the acrylic acid, humic acid, and chitosan in the present invention form a three-dimensional network structure through cross-linking. This effectively adsorbs and fixes fertilizer, preventing it from being washed away during irrigation or rainfall or decomposing before being absorbed by plant roots. After the water-retaining agent absorbs water and expands again, it slowly releases the adsorbed fertilizer, ensuring a stable nutrient supply for the plants over a long period of time, thereby improving the survival rate of poplar seedlings. It can be seen from Comparative Example 6 that when the reticulated puffball liquid is not added to the fertilization ditch of the poplar plantation, the survival rate of the poplar is reduced, and the contents of organic matter and available nitrogen, available phosphorus and available potassium are reduced compared with the embodiment. This is because the reticulated puffball is an ectomycorrhiza that can promote the growth of mycorrhizal fungi, colonize the roots of poplar seedlings to form a mycorrhizal symbiotic structure, and promote plant growth; after the mycorrhiza is formed, the interaction between the mycorrhizal auxiliary bacteria and the mycorrhizal fungi-plant symbiont can improve the absorption and transport level of mineral nutrients by the poplar seedlings; in addition, the ectomycorrhiza can increase the absorption area of ​​the root system and enhance the root system's ability to absorb water and fertilizer. The secretions of the reticulated puffball hyphae can also granulate soil particles, improve the soil structure, and improve the survival rate of the poplar seedlings in the plantation.

[0101] As can be seen from the above examples, the present invention provides a method for improving the survival rate and soil quality of young poplar plantations in sandy and arid regions through mycorrhizal symbiosis. The water-retaining agent of the present invention has excellent water and fertilizer retention capabilities. The ectomycorrhizae symbiotically interact with the poplar seedlings, increasing the root absorption area and improving the soil environment, effectively increasing the survival rate of young poplar plantations in sandy and arid regions.

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for improving the survival rate of young poplar plantations and forest soil quality in sandy and arid areas based on mycorrhizal symbiosis, characterized in that: The following steps are involved: S1. Dig a fertilizer trench around the poplar seedlings in the plantation; S2. Mix the biochar, organic fertilizer, water-retaining agent, ectomycorrhizal solution, and soil, backfill the mixture into the fertilization trench, and water the mixture until the soil reaches 58-62% of its maximum water holding capacity. The water-retaining agent comprises the following components in parts by mass: 60-80 parts of acrylic acid, 20-30 parts of humic acid, 10-15 parts of chitosan, 50-70 parts of pH regulator, 0.1-1 part of N,N-methylenebisacrylamide, and 0.5-5 parts of potassium persulfate.

2. The method according to claim 1, characterized in that The mass ratio of the biochar, organic fertilizer, water retaining agent, ectomycorrhizal liquid and soil is 20-30:100-200:10-20:5-10:50-100.

3. The method according to claim 1, characterized in that The spore concentration in the ectomycorrhizal fungal liquid is 400 to 500 spores / mL.

4. The method according to claim 1, wherein The fertilizer ditch is located at the outer edge of the vertical projection of the tree crown, and the depth of the fertilizer ditch is 30 to 40 cm and the width is 40 to 50 cm.

5. The method according to claim 4, characterized in that The molecular weight of the humic acid is 3000-5000.

6. The method according to claim 5, characterized in that The polymerization degree of the chitosan is 200-400.

7. The method according to claim 6, characterized in that The pH adjustment includes NaOH and / or KOH.

8. The method according to claim 7, characterized in that The preparation of the water-retaining agent comprises the following steps: (1) Grind chitosan and humic acid into powders of 70-80 μm; (2) preparing a 25-35 wt% alkaline solution of NaOH or KOH, mixing acrylic acid with the alkaline solution in a ratio of 1 g: 1.6-2.2 mL, stirring and dissolving, to obtain solution 1; (3) Chitosan and humic acid powders were mixed with solution 1, and the pH value was adjusted to neutral by adding alkaline solution dropwise to obtain solution 2; (4) Add N,N-methylenebisacrylamide and potassium persulfate to solution 2, stir at 50-60°C for 2-3 hours, filter, dry the filter residue, and granulate to obtain the product.

Images