Method for improving saline-alkali soil by using salvia miltiorrhiza composite biochar

Abstract

The invention discloses a method for improving saline-alkali soil through salvia miltiorrhiza composite biochar, and belongs to the technical field of saline-alkali soil remediation, and the method comprises the following steps: S1, preparing soil, applying a harmless treatment organic fertilizer as a base fertilizer, uniformly applying biochar according to a proportion, carrying out rotary tillage and soil turning on the soil, and according to the planting density and topographic conditions, carrying out rotary tillage and soil turning on the soil; the method comprises the following steps: S1, planning ridge spacing and ridge width of double-high ridges, S2, planting salvia miltiorrhiza, adopting a seedling transplanting method and a hole planting mode, digging holes in ridge surfaces, trimming overlong parts of seedling roots, vertically planting, ridging and transplanting salvia miltiorrhiza seedlings, and S3, performing field management of fertilization, weeding and topdressing after transplanting. According to the method for improving the saline-alkali soil by planting the salvia miltiorrhiza and applying the biochar, the pH and the total salt content in the soil are reduced, the activity of sucrase in the soil is improved, the activity of alkaline phosphatase in the soil is improved, and a microbial structure community in the soil is changed.

Description

Technical Field

[0001] The invention relates to the technical field of saline-alkali soil restoration, and in particular to a method for improving saline-alkali land using salvia miltiorrhiza composite biochar. Background Art

[0002] Saline-alkali land is a general term for saline soil, alkaline soil and various types of saline-alkali soil. It is formed by the combined effects of multiple natural environmental factors such as climate, geographical environment, unreasonable irrigation, and human activities.

[0003] Due to the high salt content in saline-alkali soil, plants face ionic stress, osmotic stress, oxidative stress, etc., which inhibits photosynthesis and hinders the transport of nutrients, thereby limiting plant yields. It also has a serious impact on the stability of soil structure, soil nutrients and microbial communities. Therefore, soil salinization has always been regarded as one of the main forms of land degradation. The current area of ​​saline-alkali land is about 99.13 million hectares, which has huge resource potential.

[0004] Disadvantages of physical remediation methods. Physical remediation methods usually include leaching, soil importation, soil replacement and deep tillage. The main disadvantages of these methods include: large resource consumption: Leaching method: a large amount of water resources are required for irrigation to wash away the salt in the soil, which is difficult to achieve in areas with scarce water resources and may cause waste of water resources and secondary pollution (such as improper wastewater discharge). Soil importation and soil replacement methods: a large amount of foreign soil is required to replace saline-alkali soil, which not only increases transportation costs, but may also damage the soil structure in other areas and cause new environmental problems. The amount of engineering work is large: Deep tillage: Although it can improve the soil structure, the amount of engineering work is large, requiring a large amount of manpower and mechanical equipment, the cost is high, and the effect is limited: Physical remediation methods can often only temporarily alleviate the salinization problem, and it is difficult to fundamentally solve the causes of soil salinization, such as high groundwater levels and poor drainage. Environmental impact: During the implementation process, it may have a certain impact on the surrounding environment, such as Dust pollution, soil erosion, etc. The disadvantages of chemical remediation methods are that chemical remediation methods mainly add chemical substances to the soil to react chemically with pollutants, thereby reducing the biological toxicity and effectiveness of pollutants. The disadvantages of this type of method mainly include: Secondary pollution risk: The chemical substances used in the chemical remediation process may cause secondary pollution to the soil ecological environment, affect the diversity and activity of soil microorganisms, and thus affect the health of the soil. High cost: Chemical remediation usually requires a large amount of chemical substances, which are often expensive, increasing the cost of remediation. Complex technology: Chemical remediation technology has high requirements on the professional quality and technical ability of operators, and requires precise control of the amount of chemical substances and reaction conditions, otherwise it may cause greater damage to the soil. Uncertain long-term effects: Chemical remediation is not a permanent solution. Over time, some chemical substances may gradually become ineffective, causing pollutants to be released into the environment again.

[0005] Therefore, the restoration and improvement of saline-alkali land has become one of the hot research topics, including the use of agricultural measures, physical methods, chemical methods and phytoremediation. Agricultural measures require high costs such as facilities and labor, and chemical methods may have problems such as chemical residues causing secondary pollution. The physiological characteristics of saline-alkali land soil can be changed by planting medicinal plants. Summary of the invention

[0006] The invention aims to provide a method for improving saline-alkali land by using a compound biochar of Danshen. The method of improving saline-alkali land by using a compound biochar of Danshen can reduce the pH of the soil from 8.31 to 7.92, and the total salt content from 6.50 g·kg -1 Reduced to 5.78 g kg -1, pH and total salt content decreased by 4.92% and 12.11% respectively. The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar increased the soil sucrase activity from 11.27 mg·g -1 ·24h -1 Increased to 17.59 mg g -1 ·24h -1 , the enzyme activity increased by 56.08%, and the soil alkaline phosphatase activity increased from 3.24 μmol·g -1 ·24h -1 Increased to 5.83 μmol·g -1 ·24h -1 , enzyme activity increased by 79.94%. The method of using Salvia miltiorrhiza to plant and apply biochar to improve saline-alkali land changed the structure of microbial communities in the soil. Two genera, Canariomyces and Peziza, were added to the fungal community. The abundance of Sphingomo nas in the bacterial community increased the most, by 27.78%.

[0007] In order to achieve the above effect, the present invention provides the following technical solution: a method for improving saline-alkali land with Danshen composite biochar, comprising the following steps:

[0008] S1. Perform land preparation, select a plot with flat terrain, deep soil layer and good drainage as the planting site of Salvia miltiorrhiza. Sandy loam is the best soil type, which is conducive to the growth of Salvia miltiorrhiza roots. Salvia miltiorrhiza can be rotated with crops such as corn, wheat, coix, beans, castor or non-root Chinese medicinal materials to inhibit the accumulation of soil pathogens. Apply harmless organic fertilizer as base fertilizer and apply biochar evenly in proportion. Rotate the soil and turn the soil. Plan the ridge spacing. According to the planting density and terrain conditions, plan the ridge spacing and ridge width of the double high ridges. The ridge width is 50-70cm, and the ridge spacing is determined according to actual needs. Ridge operation, use agricultural machinery or manual methods to perform ridge formation according to the planned ridge spacing and ridge width, ensure that the ridge surface is flat, the soil is fine, and the ridge height reaches more than 20cm to meet the requirements of the double high ridge. Arrange the ridge surface. After ridge formation, arrange the ridge surface to ensure that the ridge surface is flat and has no potholes, which is convenient for subsequent planting and management;

[0009] S2, planting salvia miltiorrhiza, selecting salvia miltiorrhiza seedlings with strong, sturdy, vermilion and disease-free buds, adopting the seedling transplanting method, hole planting, digging holes on the ridge surface, trimming the excessively long parts of the seedling roots and planting vertically, and cultivating the soil. For the second year of salvia miltiorrhiza seedling transplanting, the seedlings are planted upright in the ditch or hole with the reed head facing upward, covered with soil, compacted, and the heart buds are slightly exposed;

[0010] S3. After transplanting, fertilization, weeding, and topdressing are carried out in the field management. Salvia miltiorrhiza needs sufficient water to grow. Watering should be done in time according to soil moisture and weather conditions to keep the soil moist. However, drainage ditches should be dredged before the rainy season to prevent waterlogging caused by soil accumulation. Except for the plots reserved for seeds, the flower buds of the plants in other planting areas should be removed in time to promote the growth and development of roots. The removal of buds should be carried out after 9 am and should not be done when there is dew. Fertilization should be applied during the flowering period and root expansion period of the Salvia miltiorrhiza that year.

[0011] S4. Harvest the Salvia miltiorrhiza after its above-ground part has withered, and collect soil for determination of relevant evaluation indicators.

[0012] Further, the method comprises the following steps: according to the operation steps in S1, the land preparation time is early March, and the amount of the harmless treated organic fertilizer used is 1500-2000 kg·hm 2 The mixing ratio of the base fertilizer and the biochar is 19:1.

[0013] Further, the method comprises the following steps: according to the operation steps in S1, the rotary tillage depth is about 30 cm, ridges are formed after trenches are dug, the ridge width is 60 cm, the trench width is 20 cm, and the row spacing is 25-30 cm, so as to increase soil permeability and remove weeds and stones at the same time.

[0014] Further, the method comprises the following steps: according to the operation steps in S2, the planting time of the salvia miltiorrhiza is controlled in mid-March, and the standard of being thick is that the stem base is ≥ 0.4 cm.

[0015] Further, the method comprises the following steps: according to the operation steps in S2, holes are made on the ridge surface, and the hole depth is 10 cm.

[0016] Further, the method comprises the following steps: according to the operation steps in S2, the Salvia miltiorrhiza seedlings are transplanted at 8,000-10,000 plants / mu.

[0017] Further, the method comprises the following steps: according to the operation steps in S3, during the root expansion period of the salvia miltiorrhiza, i.e., mid-August to early September, the fertilizer selected during the root expansion period should be topdressing of phosphorus and potassium fertilizers.

[0018] Further, the method comprises the following steps: according to the operation steps in S3, applying 20-30 kg / mu of compound fertilizer during the flowering period of the salvia miltiorrhiza.

[0019] Further, the method comprises the following steps: according to the operation steps in S4, the above-ground part of the salvia miltiorrhiza is harvested after it withers in early November.

[0020] Further, the method comprises the following steps: according to the operation steps in S4, the soil is evaluated for relevant indicators including pH, total salt content, soil sucrase and soil alkaline phosphatase.

[0021] The present invention provides a method for improving saline-alkali land with Danshen composite biochar, which has the following characteristics:

[0022] Beneficial effects:

[0023] (1) The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar reduced the soil pH from 8.31 to 7.92 and the total salt content from 6.50 g·kg -1 Reduced to 5.78 g kg -1 , pH and total salt content decreased by 4.92% and 12.11% respectively.

[0024] (2) The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar increased the soil sucrase activity from 11.27 mg·g -1 ·24h -1 Increased to 17.59 mg g -1 ·24h -1 , the enzyme activity increased by 56.08%, and the soil alkaline phosphatase activity increased from 3.24 μmol·g -1 ·24h -1 Increased to 5.83 μmol·g -1 ·24h -1 , enzyme activity increased by 79.94%.

[0025] (3) The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar caused changes in the microbial community structure in the soil. Two genera, Canariomyces and Peziza, were added to the fungal community. The abundance of Sphingomonas in the bacterial community increased the most, by 27.78%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of a method for improving saline-alkali land using salvia miltiorrhiza composite biochar according to the present invention;

[0027] Figure 2 This is a schematic diagram of the relative abundance of the TOP10 species of bacteria and fungi at the genus level in the microbial community structure of saline-alkali land improved by planting Salvia miltiorrhiza and applying biochar in the present invention. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0029] Embodiment 1

[0030] See also Figure 1-2A method for improving saline-alkali land with Danshen composite biochar, comprising the following steps: S1, land preparation in early March, application of harmless treated organic fertilizer 1500-2000kg·hm -2As base fertilizer, biochar will be evenly applied at a ratio of 5%, the soil will be rotary tilled, the ridge spacing will be planned, and the ridge spacing and width of the double high ridges will be planned according to the planting density and terrain conditions. The ridge width is 50-70cm, and the ridge spacing is determined according to actual needs. Ridge-forming operations, using agricultural machinery or manual methods, according to the planned ridge spacing and ridge width, to ensure that the ridge surface is flat, the soil is fine, and the ridge height reaches more than 20cm to meet the requirements of double high ridges. After ridge forming, the ridge surface is sorted to ensure that the ridge surface is flat and without potholes, which is convenient for subsequent planting and management. The advantages of double high ridges for planting Salvia miltiorrhiza are mainly reflected in the following aspects: Increase ground temperature: The design of double high ridges can increase Increasing the soil surface area is conducive to absorbing more solar radiation energy, thereby increasing the soil temperature, especially in early spring and late autumn. The double-high ridges can more effectively maintain the soil temperature and provide a suitable environment for the growth of Salvia miltiorrhiza. Moisturizing effect: The soil structure of the double-high ridges is conducive to water retention, reducing water evaporation and loss, and providing a stable water supply for the growth of Salvia miltiorrhiza. Enhanced air permeability: The soil structure of the double-high ridges is relatively loose, which is conducive to air circulation and enhances the aeration of the soil, which helps the respiration of the roots of Salvia miltiorrhiza and promotes the growth and development of the root system. Smooth drainage: The design of the double-high ridges allows rainwater to be quickly discharged from the ridges, reducing water accumulation in the field and reducing the risk of root diseases of Salvia miltiorrhiza. The risk of occurrence is particularly important for rainy or low-lying areas. Increase root growth: Double high ridges provide a wider growth space for the roots of Salvia miltiorrhiza, which is conducive to the extension and development of the root system, thereby increasing the number and weight of the root system and improving the yield of Salvia miltiorrhiza. Improve light conditions: The planting method of double high ridges makes the light between Salvia miltiorrhiza plants more uniform, reduces the shading phenomenon between plants, is conducive to the photosynthesis of leaves and the accumulation of nutrients, thereby improving the quality of Salvia miltiorrhiza. Reduce humidity: The soil humidity of double high ridges is relatively low, which is not conducive to the breeding and reproduction of some moisture-loving pests and diseases, thereby reducing the occurrence of pests and diseases. Easy to manage: The planting method of double high ridges makes field management more convenient, such as Weeding, fertilization, watering and other operations can be carried out more efficiently, which is conducive to timely detection and prevention of pests and diseases, and increase production: As mentioned above, the double-high ridge planting method can significantly increase the yield of Salvia miltiorrhiza, thereby increasing farmers' economic income and reducing costs: Although the double-high ridge planting method may require more investment in the early stage (such as ridge-making machinery, labor, etc.), in the long run, due to the reduction of pests and diseases and the increase in yield, its economic benefits are significant. The rotary tillage depth is about 30cm, and the ridge is formed after digging the ditch. The ridge width is 60cm, the ditch width is 20cm, and the row spacing is 25-30cm. Salvia miltiorrhiza is planted in mid-S2 and March. Select the buds that are strong and thick (stem base ≥0.4cm), vermilion, disease-free Salvia miltiorrhiza seedlings, adopt the seedling transplanting method, hole planting, dig holes on the ridge surface, the hole depth is 10cm, trim the excessively long parts of the seedling roots and plant them vertically, and cultivate the soil. The transplanting of Salvia miltiorrhiza seedlings is about 8000-10000 plants / mu. S3. After transplanting, fertilization, weeding, topdressing and other field management are carried out. Salvia miltiorrhiza needs sufficient water to grow. Water it in time according to soil moisture and weather conditions to keep the soil moist. However, the drainage ditch needs to be dredged before the rainy season to prevent waterlogging due to soil waterlogging, and additional fertilizer should be applied during the flowering period and root expansion period of Salvia miltiorrhiza that year. The roots of Salvia miltiorrhiza During the expansion period, from mid-August to early September, the fertilizer selection during the root expansion period should be topdressing of phosphorus and potassium fertilizers. During the flowering period of Salvia miltiorrhiza, 20-30kg / mu of compound fertilizer should be applied. S4. After the aboveground part of Salvia miltiorrhiza withered in early to mid-November, it was harvested and the soil was collected for determination of relevant evaluation indicators. The harvest time after the aboveground part of Salvia miltiorrhiza withered was early November. The relevant evaluation indicators of the soil included pH, total salt content, soil sucrase and soil alkaline phosphatase. The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar composite to improve saline-alkali land reduced the pH in the soil from 8.31 to 7.92, and the total salt content from 6.50g·kg. -1 Reduced to 5.78 g kg -1 , pH and total salt content decreased by 4.92% and 12.11% respectively. The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar increased the soil sucrase activity from 11.27 mg·g -1 ·24h -1 Increased to 17.59 mg g -1 ·24h -1 , the enzyme activity increased by 56.08%, and the soil alkaline phosphatase activity increased from 3.24 μmol·g -1 ·24h -1 Increased to 5.83 μmol·g -1 ·24h -1 , enzyme activity increased by 79.94%. The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar changed the microbial community structure in the soil. Two genera, Canar iomyces and Peziza, were added to the fungal community. The abundance of Sphingomonas in the bacterial community increased the most, by 27.78%. Figure 2 In the figure, A: relative abundance diagram of TOP10 species at the genus level based on bacterial ASV, B: relative abundance diagram of TOP10 species at the genus level based on fungal ASV.

[0031] Embodiment 2

[0032] See also Figure 1A method for improving saline-alkali land with Danshen composite biochar, comprising the following steps: S1, land preparation in early March, application of harmless treated organic fertilizer 1500-2000kg·hm -2 As base fertilizer, biochar will be evenly applied at a ratio of 5%. The soil will be rotary tilled and the ridge spacing will be planned. According to the planting density and terrain conditions, the ridge spacing and width of the double high ridges are planned. The ridge width is 50-70cm, and the ridge spacing is determined according to actual needs. Ridge-forming operations are carried out using agricultural machinery or manual methods. Ridge-forming operations are carried out according to the planned ridge spacing and ridge width to ensure that the ridge surface is flat and the soil is finely broken. The ridge height reaches more than 20cm to meet the requirements of double high ridges. The ridge surface is arranged. After ridge-forming, the ridge surface is arranged to ensure that the ridge surface is flat and has no potholes, which is convenient for subsequent planting and management. The rotary tillage depth is about 30cm. Ridge-forming operations are carried out after trenching. The ridge width is 60cm, the trench width is 20cm, and the row spacing is 25-30cm. S2. Holes are made on the ridge surface with a hole depth of 10cm. Soil is cultivated. S3. Fertilization and topdressing are carried out after transplanting. Field management: Salvia miltiorrhiza needs sufficient water for growth. Watering should be done in time according to soil moisture and weather conditions to keep the soil moist. However, drainage ditches should be cleared before the rainy season to prevent waterlogging caused by soil accumulation. Fertilization should be applied at the same time as the flowering period and root expansion period of Salvia miltiorrhiza. The root expansion period of Salvia miltiorrhiza is from mid-August to early September. During the root expansion period, fertilizer selection should be topdressing of phosphorus and potassium fertilizers. During the flowering period of Salvia miltiorrhiza, 20-30 kg / mu of compound fertilizer should be applied. S4: After the Salvia miltiorrhiza of Example 1 withers in early to mid-November, the weeds are completely harvested and concentrated for treatment. The weeds need to be completely harvested, including fallen leaves and underground rhizomes, and soil is collected for determination of relevant evaluation indicators. The relevant evaluation indicators of the soil include pH, total salt content, soil sucrase and soil alkaline phosphatase.

[0033] Embodiment 3

[0034] See also Figure 1A method for improving saline-alkali land with salvia miltiorrhiza composite biochar comprises the following steps: S1, land preparation is carried out in early March, the soil is rotary tilled, ridge spacing is planned, and the ridge spacing and ridge width of double high ridges are planned according to the planting density and terrain conditions. The ridge width is 50-70 cm, and the ridge spacing is determined according to actual needs. Ridge forming operation is carried out by using agricultural machinery or manual methods according to the planned ridge spacing and ridge width to ensure that the ridge surface is flat and the soil is finely broken. The ridge height reaches more than 20 cm to meet the requirements of double high ridges, and the ridge surface is arranged. After ridge forming, the ridges are S1. The surface is cleaned to ensure that the ridge surface is flat and without potholes to facilitate subsequent planting and management. The rotary tillage depth is about 30 cm. Ridges are formed after digging trenches. The ridge width is 60 cm, the trench width is 20 cm, and the row spacing is 25-30 cm. S2. In mid-March, holes are dug on the ridge surface with a depth of 10 cm. S3. Weeding is carried out and the number and growth of weed plants are recorded. S4. In early to mid-November, soil is collected for the determination of relevant evaluation indicators. The relevant soil evaluation indicators include pH, total salt content, soil sucrase and soil alkaline phosphatase.

[0035] In the above embodiment, soil was collected to measure relevant evaluation indicators, and the specific parameters in Table 1 were obtained:

[0036] Table 1 - Changes in soil nutrient content after planting Salvia miltiorrhiza and applying biochar to improve saline-alkali land

[0037]

[0038] In summary, in Example 2, in the specific steps of the comparative example 1, the specific transplanting and planting of Salvia miltiorrhiza are missing. As a comparison, the effects of fertilization, field management and naturally grown weeds on soil indicators are confirmed. The native weeds are optimized for growth conditions due to fertilization and field management, which will affect the soil indicators to a certain extent. Secondly, Example 3 is different from Example 1 in that the planting of Salvia miltiorrhiza is reduced, and weeds are not allowed to grow. No fertilization is performed, but the land preparation, rotary tillage, ridge formation after trenching and hole opening on the ridge surface required for the planting of Salvia miltiorrhiza are still performed, which is used to compare the land preparation, rotary tillage, ridge formation after trenching and hole opening on the ridge surface in Example 1. The influence of the hole-digging on the soil index was studied, and the number of native weeds and the growth quality were recorded at the same time, and the soil index was finally obtained. It was found that the land preparation, rotary tillage, ridge-making after ditch digging and hole-digging on the ridge surface required for fertilization and planting of Salvia miltiorrhiza can stimulate the rapid growth of weeds, but its pH, total salt content, soil sucrase and soil alkaline phosphatase indexes did not have obvious index optimization, and the bioaccumulation effect of native weeds was obtained, which can slowly optimize the soil index. In Example 1, the method of using Salvia miltiorrhiza planting to apply biochar composite to improve saline-alkali land can be realized to reduce the pH in the soil from 8.31 to 7.92, and the total salt content from 6.50g·kg -1 Reduced to 5.78 g kg -1, pH and total salt content decreased by 4.92% and 12.11% respectively. The method of using Salvia miltiorrhiza to improve saline-alkali land by applying biochar increased the soil sucrase activity from 11.27 mg·g -1 ·24h -1 Increased to 17.59 mg g -1 ·24h -1 , the enzyme activity increased by 56.08%, and the soil alkaline phosphatase activity increased from 3.24 μmol·g -1 ·24h -1 Increased to 5.83 μmol·g -1 ·24h -1 , enzyme activity increased by 79.94%. The method of using Salvia miltiorrhiza to plant and apply biochar to improve saline-alkali land changed the structure of microbial communities in the soil. Two genera, Canariomyces and Peziza, were added to the fungal community. The abundance of Sphingomonas in the bacterial community increased the most, by 27.78%.

[0039] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for improving saline-alkali land by using salvia miltiorrhiza composite biochar, characterized in that: The following steps are involved: S1. Perform land preparation, select a plot with flat terrain, deep soil layer and good drainage as the planting site of Salvia miltiorrhiza. Sandy loam is the best soil type, which is conducive to the growth of Salvia miltiorrhiza roots. Salvia miltiorrhiza can be rotated with crops such as corn, wheat, coix, beans, castor or non-root Chinese medicinal materials to inhibit the accumulation of soil pathogens. Apply harmless organic fertilizer as base fertilizer and apply biochar evenly in proportion. Rotate the soil and turn the soil. Plan the ridge spacing. According to the planting density and terrain conditions, plan the ridge spacing and ridge width of the double high ridges. The ridge width is 50-70cm, and the ridge spacing is determined according to actual needs. Ridge operation, use agricultural machinery or manual methods to perform ridge formation according to the planned ridge spacing and ridge width, ensure that the ridge surface is flat, the soil is fine, and the ridge height reaches more than 20cm to meet the requirements of the double high ridge. Arrange the ridge surface. After ridge formation, arrange the ridge surface to ensure that the ridge surface is flat and has no potholes, which is convenient for subsequent planting and management; S2, planting salvia miltiorrhiza, selecting salvia miltiorrhiza seedlings with strong, sturdy, vermilion and disease-free buds, adopting the seedling transplanting method, hole planting, digging holes on the ridge surface, trimming the excessively long parts of the seedling roots and planting vertically, and cultivating the soil. For the second year of salvia miltiorrhiza seedling transplanting, the seedlings are planted upright in the ditch or hole with the reed head facing upward, covered with soil, compacted, and the heart buds are slightly exposed; S3. After transplanting, fertilization, weeding, and topdressing are carried out in the field management. Salvia miltiorrhiza needs sufficient water to grow. Watering should be done in time according to soil moisture and weather conditions to keep the soil moist. However, drainage ditches should be dredged before the rainy season to prevent waterlogging caused by soil accumulation. Except for the plots reserved for seeds, the flower buds of the plants in other planting areas should be removed in time to promote the growth and development of roots. The removal of buds should be carried out after 9 am and should not be done when there is dew. Fertilization should be applied during the flowering period and root expansion period of the Salvia miltiorrhiza that year. S4. Harvest the Salvia miltiorrhiza after its above-ground part has withered, and collect soil for determination of relevant evaluation indicators.

2. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The method comprises the following steps: according to the operation steps in S1, the land preparation time is early March, and the amount of the harmless treated organic fertilizer used is 1500-2000 kg·hm 2 The mixing ratio of the base fertilizer and the biochar is 19:

1.

3. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The method comprises the following steps: according to the operation steps in S1, the rotary tillage depth is about 30 cm, ridges are formed after trenches are dug, the ridge width is 60 cm, the trench width is 20 cm, and the row spacing is 25-30 cm, so as to increase soil permeability and remove weeds and stones at the same time.

4. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The following steps are involved: According to the operation steps in S2, the planting time of the salvia miltiorrhiza is controlled in mid-March, and the standard of being thick is that the stem base is ≥ 0.4 cm.

5. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The method comprises the following steps: according to the operation steps in S2, holes are opened on the ridge surface, and the hole depth is 10 cm.

6. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The method comprises the following steps: according to the operation steps in S2, the salvia miltiorrhiza seedlings are transplanted at 8,000 to 10,000 plants per mu.

7. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The following steps are involved: According to the operation steps in S3, during the root expansion period of the Salvia miltiorrhiza, i.e., from mid-August to early September, the fertilizer selected during the root expansion period should be topdressing of phosphorus and potassium fertilizers.

8. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The following steps are involved: According to the operation steps in S3, 20-30 kg / mu of compound fertilizer is applied during the flowering period of Salvia miltiorrhiza.

9. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The following steps are involved: According to the operation steps in S4, the time for harvesting the aboveground parts of Salvia miltiorrhiza after they wither is early November.

10. The method for improving saline-alkali land with Danshen composite biochar according to claim 1, characterized in that: The following steps are involved: According to the operation steps in S4, the soil is evaluated for related indicators including pH, total salt content, soil sucrase and soil alkaline phosphatase.

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