Planting method for keeping seedlings and promoting growth of alfalfa in light and moderate saline-alkali soil

Abstract

The invention relates to the technical field of saline-alkali soil treatment, and discloses a light and moderate saline-alkali soil alfalfa seedling protection and strong growth promotion planting method which comprises the following steps: S1, soil pretreatment and root zone microenvironment construction; s2, seed treatment and space-time double-salt-avoiding sowing; s3, microbial inoculum synergistic application; s4, water and fertilizer integration and accurate management; s5, dynamic regulation and control in the growth period, a low-salt root zone microenvironment is constructed through combination of physical obstruction and biological improvement, salt ascending is inhibited by using a slag salt isolation layer, fertility is improved by using an organic layer, and stress resistance is enhanced by adopting a salt-tolerant variety, climate window sowing and aerogel embedding fungicide; precise regulation and control are achieved through water and fertilizer integrated drip irrigation, the stability of a root zone is maintained by combining intertillage and directional topdressing, finally, the seedling emergence uniformity and the seedling stage survival rate are remarkably improved, and robust growth of plants in saline-alkali soil is promoted.

Description

Technical Field

[0001] This invention relates to the field of saline-alkali land management technology, and in particular to a planting method for protecting alfalfa seedlings and promoting vigorous growth in mild to moderate saline-alkali land. Background Technology

[0002] my country possesses vast areas of mildly to moderately saline-alkali land resources, the development and utilization of which are of great significance for ensuring food security and ecological security. Alfalfa, as an important legume forage crop, has strong salt and alkali tolerance and is a pioneer crop for improving and utilizing saline-alkali land. However, direct alfalfa planting in mildly to moderately saline-alkali land still faces severe challenges from soil salinity stress, especially the spring soil salinization and autumn salt accumulation processes, which seriously affect seed germination, seedling survival, and vigorous plant growth, limiting the efficiency and promotion of alfalfa planting in saline-alkali land. Therefore, developing planting methods for protecting seedlings and promoting vigorous growth of alfalfa in saline-alkali land is of great significance.

[0003] For example, patent CN117581759B discloses a method for improving saline-alkali land based on an efficient cultivation pattern of alfalfa, oats, and okra. This method employs an efficient alfalfa, oat, and okra cultivation pattern: first, alfalfa is planted in the saline-alkali land, harvested, and overwintered; then, oats are intercropped between rows and harvested at maturity; subsequently, okra is planted in the oat area, intercropped with alfalfa, and the above-ground parts are spread after the okra harvest. Alfalfa is harvested multiple times during the oat and okra growing season, with the final harvest followed by overwintering. This pattern, through intercropping and rotation of the three crops, improves alfalfa yield and quality, and also enhances its effect on improving saline-alkali land.

[0004] Regarding the above and existing related technologies, the inventors believe that the following defects often exist: the existing planting methods are relatively extensive in the planting and management of alfalfa, and there is a lack of effective construction and protection of the seed root zone microenvironment during planting. The seedling roots are directly subjected to salt stress, resulting in uneven emergence and low seedling survival rate, which to some extent affects the improvement effect on saline-alkali land. Summary of the Invention

[0005] The technical problem to be solved by this invention is that the existing alfalfa planting methods are relatively extensive in management. Due to the lack of effective construction and protection of the seed root zone microenvironment, the seedling roots are directly subjected to salt stress, resulting in uneven emergence and low seedling survival rate, which in turn affects the improvement effect on saline-alkali land. To this end, we propose a planting method for alfalfa in mild to moderate saline-alkali land to protect seedlings and promote vigorous growth.

[0006] To achieve the above objectives, this application adopts the following technical solution: a planting method for promoting the healthy growth of alfalfa seedlings in mildly to moderately saline-alkali land, comprising the following implementation steps: S1. Soil pretreatment and root zone microenvironment construction: Ridges are made in the field and sowing furrows are dug on the ridges. A physical salt barrier layer formed by slag and an organic amendment layer made of soybean residue and fruit shells mixed with soil are laid from bottom to top in the sowing furrows. S2. Seed treatment and temporal and spatial salt-avoidance sowing: Salt-tolerant alfalfa germplasm was selected. Before sowing, alfalfa seeds were inoculated with aerogel-embedded bacterial agent. According to the climate characteristics of the planting area, spring before soil salinization or autumn after rainfall was selected as the salt-avoidance window period. The treated alfalfa seeds were sown in the organic improvement layer by ridge sowing. S3. Synergistic application of microbial agents: After sowing alfalfa seeds, apply the aerogel-embedded microbial agent in the sowing furrow; S4. Integrated water and fertilizer management: Drip irrigation system is used for integrated water and fertilizer supply, and irrigation and fertilization plans are dynamically adjusted according to the water and fertilizer requirements of alfalfa during its growth period, soil moisture and meteorological information. S5. Dynamic regulation during the growth period: Weeding and cultivating should be carried out during the seedling stage, and organic fertilizer or foliar fertilizer should be applied during the branching stage based on the soil salinity monitoring results.

[0007] Preferably, in S1, the specific implementation methods for soil pretreatment and rhizosphere microenvironment construction are as follows: S11. Ridging operation: Ridging operation is carried out on the target field to form planting ridges. The ridge height is 15-25 cm and the ridge width is determined according to the sowing row spacing. S12. Dig seeding furrows: Dig seeding furrows on the ridge strip after ridging. The furrows should be 15-20 cm deep and 10-15 cm wide. The seeding furrows provide space for the subsequent construction of the root zone microenvironment. S13. Laying a physical salt barrier layer: Lay a layer of slag at the bottom of the sowing furrow, with a thickness of 5-8 cm. This slag layer serves as a physical barrier to prevent the salt in the lower soil layer from rising to the seed and seedling root zone through capillary action. S14. Construct an organic amendment layer: On top of the physical salt barrier layer, lay an organic amendment layer made of soybean residue, crushed fruit shells and field soil in a certain volume ratio. The thickness of the layer is 5-10 cm. This organic amendment layer is used to provide the organic matter and nutrients required for seedling growth and to inhibit salt upwelling. S15. Soil backfilling: Cover the organic amendment layer with a 2-3 cm layer of fine topsoil as needed for subsequent sowing operations and to provide a contact interface for seed germination.

[0008] Preferably, in S14, the volume ratio of soybean residue, crushed fruit shells and field soil in the organic amendment layer is 1:1:2 or 1:1:3.

[0009] Preferably, in S2, the specific implementation steps of seed treatment and spatiotemporal dual-alkaline sowing are as follows: S21. Seed biological inoculation treatment: Selected salt-tolerant alfalfa seeds are mixed with aerogel-embedded microbial agents in a predetermined ratio for inoculation treatment. Through seed mixing, coating, or short-term soaking, beneficial microorganisms are attached to the seed surface, providing an initial biological protective barrier for seed germination and young root growth. S22. Salt-avoidance sowing period decision: Based on the analysis of long-term climate data and soil water and salt transport patterns in the planting area, the optimal "salt-avoidance window" is determined. This window is usually selected in the spring after the ground thaws and before strong salt return, or in the autumn after continuous rainfall causes surface salt to leach down, in order to achieve "time-based salt avoidance". S23. Ridge-making and spot-seeding operation: During the determined salt-avoidance window period, use matching agricultural machinery to precisely sow seeds on the ridges where the root zone microenvironment has been constructed. Sow the seeds treated with microbial agents in the organic amendment layer of the sowing furrow and cover them with an appropriate amount of fine soil to complete the combination of "spatial salt avoidance" and "temporal salt avoidance".

[0010] Preferably, in S3, the specific implementation steps for the synergistic application of microbial agents are as follows: S31. Preparation for application of microbial agent: Mix and dilute the aerogel-embedded microbial agent with an inert carrier including an appropriate amount of fine sand, dry soil particles or organic materials to ensure that the microbial agent is evenly applied to the sowing furrow. S32. Precision furrow application: After alfalfa sowing and covering with soil, immediately apply the diluted inoculant along the sowing furrow in strips or holes, so that the inoculant is positioned in the soil around the alfalfa seeds, ensuring that the inoculant has full and sufficient contact with the primary roots of alfalfa. S33. Microbial agent activation: After the microbial agent is applied, a light irrigation is carried out through the drip irrigation system to fully saturate the soil in the root zone where the microbial agent is located, so as to activate the microorganisms embedded in the aerogel, promote the germination and colonization of the microorganisms in the aerogel, and thus quickly form a dominant microbial community in the primary rhizosphere of alfalfa.

[0011] Preferably, in S4, the specific implementation steps of integrated water and fertilizer management and precision management are as follows: S41. System installation and commissioning: Install the shallow-buried drip irrigation system, bury the drip irrigation tape at a certain depth in the ground near the sowing row on the ridge, and connect and commission it with the head hub including the water pump, filter, and fertilizer tank to ensure that the drip irrigation system is operating normally. S42. Water and fertilizer formula and preparation: Based on the fertilizer requirements of alfalfa at different growth stages, prepare a special liquid fertilizer containing appropriate proportions of nitrogen, phosphorus, potassium and necessary trace elements, and inject it into the fertilizer tank for later use. S43. Precision Irrigation Decision and Execution: Based on real-time monitoring of soil moisture sensor data, analysis of future weather forecast information, and growth simulation output of alfalfa model, irrigation decisions are dynamically made to determine irrigation timing, irrigation quota, and whether fertilization is required. The decision is executed through the control system to achieve on-demand precision irrigation and coupled water and fertilizer supply. S44. Salt leaching and salt control operation: During the critical growth period, if a suitable amount of natural precipitation is forecast, the amount of irrigation should be reduced to make full use of the precipitation; if a continuous drought occurs, an appropriate amount of "salt leaching irrigation" should be implemented through the drip irrigation system to allow water to seep down to below the alfalfa root zone and leach away the excess salt in the soil to control the salt concentration in the alfalfa root layer. Preferably, the control system uses an irrigation decision algorithm based on a soil moisture balance model to perform precise irrigation on demand. The calculation formula is as follows:

[0012] In the formula: n represents the number of days in the decision-making cycle; i represents the index variable, indicating the day of the decision-making cycle; E i W represents the crop's water requirement on day i; i P represents the water storage in the root zone on day i; i denoted as the effective precipitation on day i; D represents the allowable soil deficit.

[0013] Preferably, in S44, the drip irrigation system controls water volume based on a salt leaching irrigation volume algorithm, the calculation formula of which is as follows:

[0014] In the formula: k represents the three soil layers in the root zone, corresponding to the salt barrier layer, the improved layer, and the topsoil layer; S k S represents the measured salt content of the k-th soil layer; t Indicates the salt tolerance threshold of alfalfa root zone; ρ k h represents the bulk density of the k-th soil layer; k C represents the thickness of the k-th soil layer; w Indicates the mineralization of irrigation water; m k This represents the permeability coefficient of the k-th soil layer.

[0015] Preferably, in S5, the specific implementation steps for dynamic regulation of the reproductive period are as follows: S51. Seedling Protection Management: After alfalfa emerges, timely cultivation and loosening of the soil should be carried out to break up soil compaction and remove weeds in the field to cut off soil capillaries and inhibit the upward migration of lower layer salts; at the same time, close monitoring of weather changes should be carried out. When a small amount of precipitation is forecast, light irrigation should be carried out through the drip irrigation system before the rain to prevent rainwater from pressing surface salts into the seedling root zone and causing salt damage. S52. Dynamic monitoring and feedback of salinity: Before and after alfalfa enters the branching stage, the soil salinity in the root zone is monitored regularly using a soil salinity rapid tester to accurately assess the risk of salt stress and provide a basis for subsequent control measures. S53. Branching Stage Growth Regulation: Based on the salt monitoring results, when the soil salt content in the root zone exceeds the tolerance threshold, apply organic fertilizer rich in soybean residue and fruit shells through trenching or hole application to continuously improve the rhizosphere environment and buffer salt stress; at the same time, in combination with the growth of alfalfa plants, supplement micronutrient water-soluble fertilizer or growth regulators through foliar spraying.

[0016] Preferably, the aerogel-embedded bacterial agent used in seed inoculation treatment in S21 and in bacterial agent application preparation in S31 is prepared from the following components by weight: The mixture comprises 18-22 parts of a salt- and alkali-tolerant composite microbial agent, 35-42 parts of a modified silica-based aerogel carrier, 10-14 parts of a humic acid synergist, and 4-5 parts of polyethylene glycol 4000 binder; wherein the salt- and alkali-tolerant composite microbial agent is a mixture of rhizobium and salt-solubilizing Pseudomonas aeruginosa at a weight ratio of 2:1, with an effective viable count ≥2.5 × 10⁻⁶. 9 CFU / g; Preparation steps of aerogel-encapsulated microbial agent: First, mix and stir the salt-alkali resistant composite microbial agent and humic acid synergist at a constant temperature of 25-30℃ for 15-20 minutes until homogeneous. Add polyethylene glycol 4000 binder to adjust the viscosity of the mixture to 500-800 mPa•s. Then, coat and mix with a modified silicone-based aerogel carrier at high speed for 3-5 minutes. Subsequently, dry at a low temperature of 55-58℃ until the moisture content is ≤7%. Finally, pulverize and screen to a particle size of 0.3-0.4 mm. Technical effects and advantages of this invention: This invention constructs a low-salt root zone microenvironment conducive to alfalfa growth through multi-level synergy of physical barriers, biological improvement, and dynamic management. A slag layer effectively inhibits salt uptake, while an organic amendment layer enhances soil fertility and buffering capacity, laying the foundation for seed germination. By selecting salt-tolerant varieties, utilizing climatic windows for sowing, and applying aerogel-encapsulated microbial agents twice, the plant's salt tolerance and stress resistance are significantly enhanced. Furthermore, relying on an integrated fertigation system, precise regulation based on soil moisture, crop requirements, and meteorological data achieves a dynamic balance between water and fertilizer supply and salt leaching. Combined with weeding and targeted fertilization during the growth period, the root zone environment remains stable. This significantly improves the uniformity of emergence and seedling survival rate of alfalfa in mildly to moderately saline-alkali land, promoting robust plant growth and providing a reliable technical approach for the efficient agricultural utilization of saline-alkali land. Attached Figure Description

[0017] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 This is an overall flowchart of a method for protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Figure 2 This is a flowchart of step S1 of a method for protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Figure 3 This is a flowchart of step S2 of a planting method for protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Figure 4 This is a flowchart of step S3 of a method for protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Figure 5 This is a flowchart of step S4 of a planting method for protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Figure 6 This is a flowchart of step S5 of a method for protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Figure 7 This is a schematic representation of key data comparison and monitoring for a method of protecting and promoting the vigorous growth of alfalfa seedlings in mild to moderate saline-alkali land according to the present invention. Detailed Implementation

[0018] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0019] Reference Figure 1 As shown, this invention provides a technical solution: a planting method for promoting the healthy growth of alfalfa seedlings in mild to moderate saline-alkali land. This method employs innovative technologies in key stages such as soil pretreatment, seed treatment, sowing, water and fertilizer management, and growth period regulation. It aims to effectively address salt stress in saline-alkali land, significantly improve the seedling survival rate of alfalfa, and promote its robust growth. The specific implementation steps are as follows: Step 1: Soil pretreatment and root zone microenvironment construction: Ridges are made in the field and sowing furrows are dug on the ridges. A physical salt barrier layer formed by slag and an organic amendment layer made of soybean residue and fruit shells mixed with soil are laid from bottom to top in the sowing furrows. Step 2, Seed Treatment and Spatial-Temporal Salt-Avoiding Sowing: Select salt-tolerant alfalfa germplasm, and inoculate alfalfa seeds with aerogel-embedded bacterial agent before sowing. Select spring before soil salinization or autumn after rainfall as the salt-avoiding window period according to the climate characteristics of the planting area. Sow the treated alfalfa seeds in the organic improvement layer using the ridge sowing method. Step 3, Synergistic Application of Microbial Agent: After sowing alfalfa seeds, apply the aforementioned aerogel-embedded microbial agent into the sowing furrow; Step 4, Integrated Water and Fertilizer Management: A drip irrigation system is used for integrated water and fertilizer supply, and the irrigation and fertilization plan is dynamically adjusted according to the water and fertilizer requirements of alfalfa during its growth period, soil moisture, and meteorological information. Step 5: Dynamic regulation during the growth period: Weeding and cultivating during the seedling stage, and applying organic fertilizer or foliar fertilizer during the branching stage based on soil salinity monitoring results.

[0020] Specifically, in the soil pretreatment stage, a low-salt root zone environment is created by laying a salt-barrier layer and an amendment layer. A slag layer blocks salt from migrating upwards, and an organic layer provides a nutrient buffer. Salt-tolerant varieties are selected and inoculated with microbial agents at sowing, utilizing the climatic window to reduce surface salinity. Spot sowing ensures seeds are planted in the amendment layer. The microbial agent is applied twice to form a rhizosphere protective barrier, and the drip irrigation system adjusts water and fertilizer based on real-time data, meeting growth needs while leaching excess salt. During the growing season, intertillage is used to cut off capillary action and inhibit salt return, and topdressing is applied based on monitoring results to maintain a stable root zone environment. These synergistic effects of each step provide multi-dimensional control of salt damage, from physical barriers and biological protection to dynamic regulation. This approach effectively blocks the migration path of salt to the root zone, uses the organic amendment layer to buffer salt stress, and avoids peak salt periods through precise sowing. The synergistic application of microbial agents enhances plant salt tolerance, and dynamic water and fertilizer management maintains the salt balance in the root zone. It improved the uniformity of emergence and seedling survival rate of alfalfa in saline-alkali land, promoted the robust growth of plants in the saline environment, and provided a reliable solution for the efficient utilization of saline-alkali land resources.

[0021] Reference Figure 1 , Figure 2 and Figure 7 As shown in this implementation plan: This application further proposes specific methods for soil pretreatment and rhizosphere microenvironment construction during alfalfa planting in mildly to moderately saline-alkali land in step one, including ridging operations, digging sowing furrows, laying physical salt barriers, constructing organic amendment layers, and soil backfilling steps: S11. Ridging Operation: Ridging is carried out on the target field to form planting ridges. The ridge height is 15-25 cm, and the ridge width is determined according to the sowing row spacing. This is to raise the sowing position and utilize the water and salt movement law to achieve spatial "salt avoidance".

[0022] S12. Dig seed furrows: Dig seed furrows on the raised beds after ridging, with a depth of 15-20 cm and a width of 10-15 cm. Seeding furrows provide space for the subsequent construction of the root zone microenvironment.

[0023] S13. Laying a physical salt barrier layer: Lay a layer of slag at the bottom of the sowing furrow, with a thickness of 5-8 cm. This slag layer acts as a physical barrier, effectively preventing soil salts from rising to the seed and seedling root zone through capillary action.

[0024] S14. Constructing an organic amendment layer: On top of the physical salt barrier layer, lay an organic amendment layer composed of soybean residue, crushed fruit shells, and field soil in a certain volume ratio (preferably 1:1:2 to 1:1:3), with a thickness of 5-10 cm. This layer provides the organic matter and nutrients needed for seedling growth, improves soil aggregate structure, and inhibits salt upwelling.

[0025] S15. Soil backfilling: If necessary, a 2-3 cm layer of fine topsoil can be placed on the organic amendment layer to facilitate subsequent sowing operations and provide a more suitable contact interface for seed germination.

[0026] Specifically, a layered structure was used to construct the root zone microenvironment, forming a salinity regulation system that synergistically combines physical barriers and biological amendments. Seeding furrows were dug on ridge cultivation, utilizing a slag layer to cut off the capillary uplift path of salt. The organic amendment layer continuously releases humic acid through the decomposition of organic materials, inhibiting salt ion activity and improving soil aggregate structure. A fine topsoil cover prevents seeds from directly contacting high concentrations of organic matter, ensuring the water-air balance required for germination. The thickness of each layer was optimized to maintain an appropriate tillage depth while ensuring salt isolation, preventing root development hindrance. This approach effectively controlled the salt concentration in the alfalfa seedling root zone, reducing the direct stress of salt ions on seed germination and root growth. The slag layer blocked the underground salt uplift pathway, the organic amendment layer further inhibited salt migration through adsorption, and the topsoil cover ensured quality seed-soil contact. This method provided a stable nutrient supply to seedlings while suppressing salt damage, significantly improving the emergence and survival rates of alfalfa in saline-alkali land.

[0027]

[0028] Table 1 shows the key data comparison and monitoring for alfalfa seedling protection and vigorous growth promotion in mild to moderate saline-alkali land.

[0029] Table 2 shows the dynamic comparison of alfalfa growth and soil indicators in mildly to moderately saline-alkali land.

[0030] Table 3 compares the inputs and benefits of alfalfa cultivation in mild to moderate saline-alkali land. As can be seen from Table 1 above, this method exhibits significant advantages at all stages of the entire growth period: at the sowing and emergence stage, the emergence rate is higher and faster, and it can more effectively reduce the salinity of the root zone, solving the problem of "difficulty in emergence" of alfalfa in saline-alkali land; the seedling survival rate is greatly improved during the seedling stage, and the seedlings grow more robustly; during the branching stage, alfalfa has stronger resistance to saline-alkali stress and exhibits more vigorous growth; during the budding stage, the biomass accumulation rate is faster, laying a solid foundation for high yield; during the harvesting stage, not only is the yield higher and the quality better (high crude protein content), but it can also ensure the efficient germination of regenerated buds, achieving continuous production.

[0031] Table 2 above shows that under this method, the growth indicators of alfalfa, such as plant height, root length, and number of branches, are better than those of ordinary planting methods throughout the entire process. The plants are more robust and their growth is more coordinated. At the same time, the soil salinity in the root zone is more stable and remains at a lower level, and the soil pH is more suitable for alfalfa growth. The continuously improved rhizosphere environment reduces the burden on alfalfa throughout its growth cycle. In contrast, under ordinary methods, soil salinity stress is more prominent, which seriously limits the growth potential of alfalfa.

[0032] Table 3 above illustrates that although the input cost of this method is higher than that of ordinary planting methods, the per-acre yield is greatly increased by improving the yield (significantly higher yield of fresh grass and hay) and quality (better crude protein content). The input cost can be obtained with excess returns through higher output and better commercial value, which has obvious advantages in economic benefits and achieves a virtuous cycle of "high input for high output and high benefits".

[0033] Reference Figure 1 and Figure 3 As shown in this implementation plan: This application further proposes specific implementation steps for seed treatment and spatiotemporal dual-salt sowing in step two: S21. Seed biological inoculation treatment: Selected salt-tolerant alfalfa seeds are mixed with aerogel-embedded microbial agents in a predetermined ratio for inoculation treatment. This can be achieved through seed dressing, coating, or short-term soaking, allowing beneficial microorganisms to adhere to the seed surface and providing an initial biological protective barrier for seed germination and young root growth.

[0034] S22. Salt-avoidance sowing period decision: Based on the analysis of long-term climate data and soil water and salt transport patterns in the planting area, the optimal "salt-avoidance window" is determined. This window is usually selected in a specific period after the surface thaws in spring and before strong salt return, or after continuous rainfall in autumn causes surface salt to leach down, in order to achieve "time-based salt avoidance".

[0035] S23. Ridging and sowing operation: During the determined salt-avoidance window, use the matching agricultural machinery to perform precise sowing on the ridges where the root zone microenvironment has been constructed (completed in step S1). Sow the seeds treated with microbial agents in the organic amendment layer of the sowing furrow and cover with an appropriate amount of fine soil to complete the combination of "spatial salt avoidance" (using the ridge structure to avoid the surface layer where salt accumulates) and "temporal salt avoidance".

[0036] Specifically, the microbial protective layer formed on the seed surface reduces rhizosphere salt concentration by secreting organic acids and extracellular polysaccharides, while simultaneously enhancing seed stress resistance. Choosing the optimal sowing window allows seed germination to avoid peak soil salinity, while the physical barrier and nutrient supply from the organic amendment layer further mitigate salt stress. Ridging and spot sowing positions seeds within a three-dimensional salt-prevention system constructed from the salt barrier and amendment layers, forming a spatial salt avoidance mechanism. The temporal sowing decisions and spatial microenvironment construction work synergistically to achieve dual avoidance of salt stress. Through these methods, the risk of salt exposure during seed germination is effectively reduced, microbial metabolic activity continuously alleviates rhizosphere salt stress in seedlings, and the temporal and spatial dual avoidance strategy allows seedlings to complete critical growth stages within a low-salt window. Precise control of sowing location ensures root development is within an optimized microenvironment, significantly improving the emergence rate and seedling survival rate of alfalfa in saline-alkali land.

[0037] Reference Figure 1 and Figure 4 As shown in this implementation plan: This application further proposes specific implementation steps for the synergistic application of microbial agents in step three: in the microbial agent application preparation stage, the aerogel-embedded microbial agent is mixed and diluted with an inert carrier; in the precision furrow application stage, the diluted microbial agent is applied in strips or holes along the sowing furrow; in the microbial agent activation stage, light irrigation is carried out through a drip irrigation system.

[0038] S31. Preparation for application of microbial agent: Mix and dilute the aerogel-embedded microbial agent with an appropriate amount of inert carrier (such as fine sand, dry soil particles or organic materials) to ensure that the microbial agent can be evenly applied to the sowing furrow.

[0039] S32. Precision furrow application: After sowing and covering with soil, immediately apply the diluted inoculant along the sowing furrow in strips or holes, so that the inoculant is positioned in the soil around the seeds and ensures that it can fully contact the primary roots of alfalfa.

[0040] S33. Microbial agent activation: After the microbial agent is applied, a light irrigation is carried out through the drip irrigation system to fully wet the soil in the root zone where the microbial agent is located, activate the microorganisms embedded in the aerogel, promote their germination and colonization, and thus quickly form a dominant microbial community in the rhizosphere.

[0041] Specifically, the preparation stage of inoculant application involves mixing with an inert carrier to reduce the concentration of the inoculant, avoiding the toxicity of high concentrations to the seeds, while simultaneously utilizing the carrier's dispersing effect to achieve uniform distribution of the inoculant. The precision furrow application stage employs strip or hole application methods, ensuring the inoculant is precisely applied to the soil surrounding the seeds, forming an inoculant distribution zone and ensuring full contact between the inoculant and the developing primary roots. The inoculant activation stage utilizes a drip irrigation system for light irrigation; the water infiltration causes the aerogel carrier to swell and release microorganisms, simultaneously diffusing the inoculant into the rhizosphere, accelerating microbial germination and colonization through this dual action. These three steps are sequentially linked, forming a progressive technical chain of inoculant dilution and dispersion, spatial positioning, and water activation. This approach effectively solves the problem of low microbial colonization efficiency caused by uneven inoculant application, ensuring uniform distribution of the inoculant in the soil surrounding the seeds. Precise positioning ensures full contact between the inoculant and the roots, and combined with water activation, accelerates the microbial colonization process, ultimately leading to the rapid formation of a dominant microbial community in the alfalfa rhizosphere, constructing a biological barrier against salt stress.

[0042] This application further proposes an aerogel-embedded microbial agent used in seed inoculation treatment and preparation for microbial agent application, which is prepared from the following components by weight: 18-22 parts of salt-alkali tolerant composite microbial agent, 35-42 parts of modified silica-based aerogel carrier, 10-14 parts of humic acid synergist, and 4-5 parts of polyethylene glycol 4000 binder; wherein, the salt-alkali tolerant composite microbial agent is a mixture of rhizobium and salt-solubilizing Pseudomonas aeruginosa at a weight ratio of 2:1, with an effective viable count ≥2.5×10⁻⁶. 9 The preparation steps of the CFU / g aerogel-encapsulated microbial agent include mixing and stirring the salt-alkali resistant composite microbial agent with humic acid synergist, adding polyethylene glycol 4000 binder to adjust the viscosity, then coating and mixing it with a modified silicon-based aerogel carrier at high speed, drying it at low temperature, and then pulverizing and screening it to a specific particle size.

[0043] Among them, the salt-tolerant compound microbial agent refers to a mixed bacterial community composed of rhizobia and halophilic Pseudomonas, specifically obtained by liquid fermentation followed by centrifugation to collect the bacterial cells. Rhizobia promote nitrogen fixation in alfalfa, while halophilic Pseudomonas directly decomposes soil salt ions. The modified silica-based aerogel carrier refers to a porous silica-based material modified with hydrophobicity, specifically prepared by the sol-gel method followed by trimethylchlorosilane surface treatment. Its porous structure provides physical protection for microorganisms and blocks salt erosion. The humic acid synergist refers to humic acid substances extracted from weathered coal, specifically obtained by alkali-dissolution-acid precipitation followed by spray drying. It reduces rhizosphere salt concentration through ion exchange. The polyethylene glycol 4000 binder refers to a polyethylene glycol polymer with a molecular weight of 4000, specifically obtained by melt mixing with other components to adjust the viscosity of the mixture and enhance particle formability.

[0044] Specifically, salt-tolerant composite microbial inoculants and humic acid synergists are mixed under constant temperature conditions, allowing humic acid to uniformly coat the surface of the microorganisms. The addition of polyethylene glycol binder creates a suitable viscosity for subsequent carrier coating. During high-speed mixing, the modified silica-based aerogel carrier embeds the inoculant-humic acid complex into its porous structure, forming a physical barrier. The low-temperature drying process controls the rate of moisture evaporation, preventing high temperatures from inactivating the microorganisms. The final particle size, determined by pulverization and screening, ensures the slow release of the inoculant into the soil. The synergistic effect of rhizobia and halophilic Pseudomonas forms a dual regulatory mechanism in the alfalfa rhizosphere. The aerogel carrier blocks salt while maintaining the microenvironment required for microbial metabolism, and humic acid continuously regulates the rhizosphere ion balance.

[0045] Reference Figure 1 and Figure 5 As shown in this implementation plan: This application further proposes specific implementation steps for step four of the water and fertilizer integration and precision management: S41. System Installation and Debugging: Deploy the shallow-buried drip irrigation system, bury the drip irrigation tape (pipe) at a certain depth underground near the sowing row on the ridge, and connect and debug it with the headworks (including water pump, filter, fertilizer tank, etc.) to ensure that the system can operate normally.

[0046] S42. Water and fertilizer formula and preparation: Based on the fertilizer requirements of alfalfa at different growth stages (such as seedling stage, branching stage, budding stage, etc.), prepare a special liquid fertilizer containing appropriate proportions of nitrogen, phosphorus, potassium and necessary trace elements, and inject it into the fertilizer tank for later use.

[0047] S43. Precision Irrigation Decision-Making and Execution: Based on real-time monitoring of soil moisture sensor data, analysis of future weather forecasts (especially precipitation probability and evaporation), and growth simulation output from alfalfa models, irrigation decisions are dynamically formulated, including determining irrigation timing, irrigation quotas, and whether fertilization is necessary. The control system executes these decisions, achieving on-demand precision irrigation and coupled water and fertilizer supply.

[0048] S44. Salt leaching and salt control operation: During the critical growth period, if a suitable amount of natural precipitation is forecast, the amount of irrigation should be reduced to make full use of the precipitation; if there is a continuous drought, an appropriate amount of "salt leaching irrigation" should be implemented through the drip irrigation system to allow water to seep down to the root zone and leach away the excess salt in the soil to control the salt concentration in the root zone.

[0049] Specifically, the underground deployment of the shallow-buried drip irrigation system effectively blocks the upward movement of salts caused by surface evaporation, allowing irrigation water to directly act on the root zone soil. Dynamic adjustments to the water and fertilizer formula, matched to the alfalfa's growth cycle nutrient requirements, avoid the nutrient waste and salt surges caused by traditional broadcasting. The precision irrigation decision module integrates real-time soil moisture monitoring data, the probability of precipitation in the next 72 hours, and the transpiration prediction output from the alfalfa growth model. It calculates daily irrigation needs using the soil moisture balance equation, achieving a dynamic balance between on-demand water supply and salt leaching. Salt leaching control is implemented during dry periods, initiating a salt-leaching mode by increasing the volume of each irrigation to create infiltration flow, migrating salts accumulated in the root zone to deeper soil layers. Before rainfall, reduced irrigation allows for the full utilization of rainwater for natural salt leaching. This solution addresses the problem of salt accumulation in the root zone caused by extensive irrigation in alfalfa cultivation on saline-alkali land. The combination of underground drip irrigation and precise water and fertilizer control ensures adequate water and nutrient supply to the plants while establishing a controllable salt leaching mechanism. The application of dynamic decision-making models enables irrigation strategies to adapt to environmental changes in real time, avoiding both the salt stress caused by traditional fixed irrigation methods during droughts and the nutrient loss caused by excessive irrigation during the rainy season. This integrated management system effectively maintains a suitable water and salt environment in the alfalfa root zone, providing reliable technical support for the seedling protection and vigorous growth of alfalfa in saline-alkali land.

[0050] This application further proposes an irrigation decision algorithm for the control system based on a soil moisture balance model for precise irrigation on demand. The calculation formula is as follows:

[0051] In the formula: n represents the number of days in the decision-making cycle; i represents the index variable, indicating the day of the decision-making cycle; E i W represents the crop's water requirement on day i; i P represents the water storage in the root zone on day i; i denoted as the effective precipitation on day i; D represents the allowable soil deficit.

[0052] The decision-making cycle in days refers to the range of consecutive days used to formulate an irrigation plan. This can be determined by dividing alfalfa into different growth stages, such as 5 days for the seedling stage and 7 days for the branching stage. The cycle length can be dynamically adjusted to adapt to changes in water demand at different growth stages. Crop water requirement refers to the daily water consumption per unit area of ​​alfalfa at a specific growth stage. This can be calculated using the Penman formula combined with the crop coefficient, reflecting the combined water consumption characteristics of plant transpiration and soil evaporation. Root zone water storage refers to the effective water content of the soil in the alfalfa root zone. This can be obtained through real-time monitoring using soil moisture sensors, characterizing the actual water supply capacity of the soil. Effective precipitation refers to the amount of rainfall that can be absorbed by the soil and used by the crop. This can be calculated by multiplying the rainfall by the runoff coefficient and infiltration coefficient, quantifying the supplementary role of natural precipitation in irrigation demand. Soil allowable deficit refers to the minimum water storage threshold required to maintain normal alfalfa growth. This can be determined by the difference between field capacity and the wilting coefficient, balancing water-saving needs with the plant's drought tolerance.

[0053] Specifically, this algorithm achieves dynamic irrigation decisions by establishing a multi-parameter coupled iterative calculation framework. After setting the decision cycle, the system collects root zone water storage data daily and calculates the daily crop water requirement, while simultaneously combining weather forecasts to obtain effective precipitation predictions. By accumulating the changes in crop water requirement and root zone water storage daily, an irrigation command is triggered when the cumulative water deficit exceeds the soil's allowable threshold. This calculation process fully considers the replenishment of soil moisture by natural precipitation, avoiding the over- or under-irrigation problems caused by neglecting meteorological factors in traditional fixed irrigation models. In saline-alkali environments, this algorithm can adjust the irrigation amount according to real-time soil moisture, ensuring sufficient water to leach salts from the root zone while preventing deep salt leaching difficulties caused by over-irrigation. Through this scheme, the irrigation strategy can be dynamically adjusted according to the actual growth needs of alfalfa and changes in environmental conditions, maintaining the water-salt balance in the root zone in saline-alkali environments. This algorithm effectively avoids salt concentration caused by insufficient irrigation, while preventing incomplete salt leaching caused by over-irrigation, creating a stable root zone water environment for alfalfa growth. By precisely matching water supply with crop needs, the risk of salt stress is reduced and the efficiency of water resource utilization is improved.

[0054] This application further proposes a drip irrigation system based on a salt leaching irrigation volume algorithm for water volume control, the calculation formula of which is as follows:

[0055] In the formula: k represents the three soil layers in the root zone, corresponding to the salt barrier layer, the improved layer, and the topsoil layer; S k S represents the measured salt content of the k-th soil layer; t Indicates the salt tolerance threshold of alfalfa root zone; ρ k h represents the bulk density of the k-th soil layer; kC represents the thickness of the k-th soil layer; w Indicates the mineralization of irrigation water; m k This represents the permeability coefficient of the k-th soil layer.

[0056] The root zone soil consists of three layers: a physical salt barrier layer, an organic amendment layer, and a topsoil layer. This layering can be achieved through stratified sampling and conductivity measurement, reflecting the salt distribution characteristics at different soil depths. Measured salt content refers to the total soluble salt content of each soil layer, obtained using a soil salinity rapid analyzer. This can be achieved using conductivity or chemical titration methods, quantifying the degree of salt stress in each soil layer. The salt tolerance threshold is the critical soil salinity level that alfalfa roots can tolerate for normal growth. This can be determined through pot experiments combined with physiological index measurements, setting target values ​​for salt leaching. Soil bulk density refers to the dry weight of a unit volume of soil, measured using the ring sampler method, used to calculate the total soil salt content. Soil permeability coefficient refers to the rate of water infiltration in the soil under a unit hydraulic gradient, measured using a constant head permeability test, characterizing salt leaching efficiency. Irrigation water salinity refers to the total concentration of dissolved salts in irrigation water, measured using a conductivity meter or the evaporation residue method, used to assess the dilution effect of irrigation water on soil salinity.

[0057] Specifically, the salt leaching irrigation algorithm dynamically determines the required irrigation water volume by calculating the salt content, bulk density, thickness, and permeability coefficient of the root zone soil in a stratified manner, combined with the alfalfa tolerance threshold and irrigation water mineralization. The algorithm divides the root zone soil into a salt-barrier layer, a modified layer, and a topsoil layer. For each soil layer, based on measured salt content, bulk density, and thickness parameters, it calculates the difference in salt content exceeding the tolerance threshold. This difference is then combined with the water permeability reflected by the permeability coefficient, and finally, a weighted sum is used to obtain the total irrigation volume. This stratified calculation method accurately quantifies the salt leaching needs of each soil layer, avoiding localized salt residue or excessive leaching caused by a single irrigation volume. Simultaneously, the introduction of irrigation water mineralization parameters allows for dynamic adjustment of the impact of irrigation water quality on salt dilution, ensuring that the irrigation water volume effectively leaches salt from the root zone while avoiding water waste or nutrient loss due to excessive irrigation. The above scheme can accurately calculate the minimum irrigation amount required for salt leaching based on the salt content, permeability, and irrigation water quality of different soil layers in the root zone. While ensuring that the salt concentration of each soil layer is reduced below the alfalfa tolerance threshold, it avoids water waste and nutrient loss caused by excessive irrigation, effectively balancing the contradiction between salt leaching effect and water conservation needs.

[0058] Reference Figure 1 and Figure 6 As shown in this implementation plan: This application further proposes specific implementation steps for the dynamic regulation of the reproductive period in step five: S51. Seedling Management: After alfalfa emerges, timely cultivation and loosening of the soil should be carried out to break up soil compaction and remove weeds in the field to cut off soil capillaries and effectively inhibit the upward migration of lower layer salts. At the same time, close monitoring of weather changes should be carried out. When a small amount of precipitation is forecast, light irrigation should be carried out through the drip irrigation system before the rain to prevent rainwater from pressing surface salts to the seedling root zone and causing salt damage.

[0059] S52. Dynamic monitoring and feedback of salinity: Before and after alfalfa enters the branching stage, the soil salinity in the root zone is monitored regularly using a soil salinity rapid tester to accurately assess the risk of salt stress and provide a basis for subsequent control measures.

[0060] S53. Branching Stage Growth Regulation: Based on the salt monitoring results, when the soil salt content in the root zone exceeds the tolerance threshold, apply organic fertilizer rich in soybean residue and fruit shells through trenching or hole application to continuously improve the rhizosphere environment and buffer salt stress. At the same time, in combination with the growth of alfalfa plants, supplement micronutrient water-soluble fertilizer or growth regulators through foliar spraying to enhance the plant's resistance and promote robust growth.

[0061] Among these, tillage and loosening of the soil refers to agricultural operations that use machinery or manual methods to turn over the topsoil to break up the compacted layer. Specifically, this can be done using rotary tillers or hoes during the seedling stage for shallow tillage. By cutting off the capillary pores in the soil, it reduces the path of water evaporation, thereby inhibiting salt from migrating upwards to the root zone with water. Light irrigation refers to the operation of moistening the topsoil with a small amount of water. Specifically, this can be done using a drip irrigation system to apply irrigation water equivalent to 5-8 mm of rainfall before rain, forming a moisture barrier on the soil surface to prevent rainwater from infiltrating and carrying salt to the root zone. Dynamic salinity monitoring refers to the technical means of rapidly determining the salinity concentration of the soil solution using conductivity or spectroscopy methods. Specifically, this can be done using a portable soil salinity rapid tester to sample and test at different depths in the root zone, obtaining real-time salinity distribution data to assess the stress risk level. Among them, soybean residue and nut shell organic fertilizer refers to fertilizer made by fermenting a mixture of soybean processing by-products and crushed nut shells. Specifically, soybean residue and walnut shells can be mixed in a 3:1 mass ratio and composted. Their porous structure adsorbs salt ions and releases humic acid to improve the physical and chemical properties of the soil. Foliar spraying refers to a fertilization method that involves directly spraying nutrient solution onto the surface of plant leaves. This can be done using drones or backpack sprayers in the early morning or evening, allowing the plant to directly absorb trace elements through the stomata of the leaves, thus avoiding interference from soil salts on root nutrient absorption.

[0062] Specifically, during the seedling stage, a dual salt-barrier is formed through physical soil loosening and water regulation. Cultivation disrupts the soil capillary structure, blocking the upward flow of salt. Pre-rain irrigation utilizes the water gradient to create a reverse salt-suppressing effect. Before branching, a data feedback mechanism is established through high-frequency salt monitoring. A three-dimensional salt distribution model of the root zone is constructed using rapid sampling instruments at multiple points to accurately identify high-risk areas. During the branching stage, differentiated measures are implemented based on salt thresholds. Furrow application of organic fertilizer forms a rhizosphere buffer zone through ion adsorption and organic matter release, while foliar spraying bypasses saline soil to directly supplement the plant's nutrient needs. These measures at each stage form a closed-loop management chain, controlling the dynamic balance of salt and enhancing the plant's resistance to adverse conditions.

[0063] In some specific implementations, the depth of inter-row cultivation and loosening of the soil can be controlled at 3-5 cm to avoid damaging the seedling roots; the amount of light irrigation can be adjusted according to the soil texture, for example, 5 mm of irrigation for sandy soil and 8 mm for clay soil; the frequency of salt monitoring can be set to once every 7-10 days, and increased to once every 3 days after consecutive sunny days or rainfall; the amount of organic fertilizer applied can be calculated at 2-3 tons per hectare, and applied in furrows 15 cm deep on both sides of the sowing furrow; the concentration of foliar fertilizer can be controlled between 0.2% and 0.5%, and chelated water-soluble fertilizer containing zinc and boron trace elements should be selected. The above-mentioned approach effectively blocked the migration path of salt from the seedling stage to the root zone, avoiding secondary salinization damage caused by rainfall; high-frequency salt monitoring provided real-time data support for regulatory decisions, ensuring timely implementation of targeted improvement measures during the critical branching stage; deep application of organic fertilizer and foliar nutrient supplementation created a synergistic effect, reducing the salt concentration in the root zone while ensuring the nutrient supply to the plants, ultimately achieving the dual goals of improving the survival rate of alfalfa seedlings in saline-alkali land and promoting robust plant growth.

[0064] The technical scope of this invention is not limited to the content described above. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the technical concept of this invention, and all such modifications and variations should fall within the protection scope of this invention.

Claims

1. A planting method for protecting seedlings and promoting vigorous growth of alfalfa in mildly to moderately saline-alkali land, characterized in that, The implementation steps include the following: S1. Soil pretreatment and root zone microenvironment construction: Ridges are made in the field and sowing furrows are dug on the ridges. A physical salt barrier layer formed by slag and an organic amendment layer made of soybean residue and fruit shells mixed with soil are laid from bottom to top in the sowing furrows. S2. Seed treatment and temporal and spatial salt-avoidance sowing: Salt-tolerant alfalfa germplasm was selected. Before sowing, alfalfa seeds were inoculated with aerogel-embedded bacterial agent. According to the climate characteristics of the planting area, spring before soil salinization or autumn after rainfall was selected as the salt-avoidance window period. The treated alfalfa seeds were sown in the organic improvement layer by ridge sowing. S3. Synergistic application of microbial agents: After sowing alfalfa seeds, apply the aerogel-embedded microbial agent in the sowing furrow; S4. Integrated water and fertilizer management: Drip irrigation system is used for integrated water and fertilizer supply, and irrigation and fertilization plans are dynamically adjusted according to the water and fertilizer requirements of alfalfa during its growth period, soil moisture and meteorological information. S5. Dynamic regulation during the growth period: Weeding and cultivating should be carried out during the seedling stage, and organic fertilizer or foliar fertilizer should be applied during the branching stage based on the soil salinity monitoring results.

2. The planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 1, characterized in that: The specific implementation methods for soil pretreatment and rhizosphere microenvironment construction in S1 are as follows: S11. Ridging operation: Ridging operation is carried out on the target field to form planting ridges. The ridge height is 15-25 cm and the ridge width is determined according to the sowing row spacing. S12. Dig seeding furrows: Dig seeding furrows on the ridge strip after ridging. The furrows should be 15-20 cm deep and 10-15 cm wide. The seeding furrows provide space for the subsequent construction of the root zone microenvironment. S13. Laying a physical salt barrier layer: Lay a layer of slag at the bottom of the sowing furrow, with a thickness of 5-8 cm. This slag layer serves as a physical barrier to prevent the salt in the lower soil layer from rising to the seed and seedling root zone through capillary action. S14. Construct an organic amendment layer: On top of the physical salt barrier layer, lay an organic amendment layer made of soybean residue, crushed fruit shells and field soil in a certain volume ratio. The thickness of the layer is 5-10 cm. This organic amendment layer is used to provide the organic matter and nutrients required for seedling growth and to inhibit salt upwelling. S15. Soil backfilling: Cover the organic amendment layer with a 2-3 cm layer of fine topsoil as needed for subsequent sowing operations and to provide a contact interface for seed germination.

3. The planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 2, characterized in that: In S14, the volume ratio of soybean residue, crushed fruit shells, and field soil in the organic amendment layer is 1:1:2 or 1:1:

3.

4. The planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 1, characterized in that: In step S2, the specific implementation steps of seed treatment and spatiotemporal dual-alkaline seeding are as follows: S21. Seed biological inoculation treatment: Selected salt-tolerant alfalfa seeds are mixed with aerogel-embedded microbial agents in a predetermined ratio for inoculation treatment. Through methods including seed dressing, coating, or short-term soaking, beneficial microorganisms are attached to the seed surface, providing an initial biological protective barrier for seed germination and young root growth. S22. Salt-avoidance sowing period decision: Based on the analysis of long-term climate data and soil water and salt transport patterns in the planting area, the optimal "salt-avoidance window" is determined. This window is usually selected in the spring after the ground thaws and before strong salt return, or in the autumn after continuous rainfall causes surface salt to leach down, in order to achieve "time-based salt avoidance". S23. Ridge-making and spot-seeding operation: During the determined salt-avoidance window period, use matching agricultural machinery to precisely sow seeds on the ridges where the root zone microenvironment has been constructed. Sow the seeds treated with microbial agents in the organic amendment layer of the sowing furrow and cover them with an appropriate amount of fine soil to complete the combination of "spatial salt avoidance" and "temporal salt avoidance".

5. The planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 4, characterized in that: In step S3, the specific implementation steps for the synergistic application of microbial agents are as follows: S31. Preparation for application of microbial agent: Mix and dilute the aerogel-embedded microbial agent with an inert carrier including an appropriate amount of fine sand, dry soil particles or organic materials to ensure that the microbial agent is evenly applied to the sowing furrow. S32. Precision furrow application: After alfalfa sowing and covering with soil, immediately apply the diluted inoculant along the sowing furrow in strips or holes, so that the inoculant is positioned in the soil around the alfalfa seeds, ensuring that the inoculant has full and sufficient contact with the primary roots of alfalfa. S33. Microbial agent activation: After the microbial agent is applied, a light irrigation is carried out through the drip irrigation system to fully saturate the soil in the root zone where the microbial agent is located, so as to activate the microorganisms embedded in the aerogel, promote the germination and colonization of the microorganisms in the aerogel, and thus quickly form a dominant microbial community in the primary rhizosphere of alfalfa.

6. The planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 1, characterized in that: In step S4, the specific implementation steps of integrated water and fertilizer management and precision management are as follows: S41. System installation and commissioning: Install the shallow-buried drip irrigation system, bury the drip irrigation tape at a certain depth in the ground near the sowing row on the ridge, and connect and commission it with the head hub including the water pump, filter, and fertilizer tank to ensure that the drip irrigation system is operating normally. S42. Water and fertilizer formula and preparation: Based on the fertilizer requirements of alfalfa at different growth stages, prepare a special liquid fertilizer containing appropriate proportions of nitrogen, phosphorus, potassium and necessary trace elements, and inject it into the fertilizer tank for later use. S43. Precision Irrigation Decision and Execution: Based on real-time monitoring of soil moisture sensor data, analysis of future weather forecast information, and growth simulation output of alfalfa model, irrigation decisions are dynamically formulated to determine the timing of irrigation, irrigation quota, and whether fertilization is required. The decisions are executed through the control system to achieve on-demand precision irrigation and coupled water and fertilizer supply. S44. Salt leaching and salt control operation: During the critical growth period, if a suitable amount of natural precipitation is forecast, the amount of irrigation should be reduced to make full use of the precipitation; if there is a continuous drought, an appropriate amount of "salt leaching irrigation" should be implemented through the drip irrigation system to allow water to seep down to the alfalfa root zone and leach away the excess salt in the soil to control the salt concentration in the alfalfa root layer.

7. A planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 6, characterized in that: The control system uses an irrigation decision algorithm based on a soil moisture balance model to perform precise irrigation on demand. The calculation formula is as follows: In the formula: n represents the number of days in the decision-making cycle; i represents the index variable, indicating the day of the decision period; E i W represents the crop's water requirement on day i; i P represents the water storage in the root zone on day i; i denoted as the effective precipitation on day i; D represents the allowable soil deficit.

8. A planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 6, characterized in that: In step S44, the drip irrigation system controls water volume based on a salt leaching irrigation volume algorithm, the calculation formula of which is as follows: In the formula: k represents the three soil layers in the root zone, corresponding to the salt barrier layer, the improved layer, and the topsoil layer; S k S represents the measured salt content of the k-th soil layer; t Indicates the salt tolerance threshold of alfalfa root zone; ρ k h represents the bulk density of the k-th soil layer; k C represents the thickness of the k-th soil layer; w Indicates the mineralization of irrigation water; m k This represents the permeability coefficient of the k-th soil layer.

9. A planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 1, characterized in that: The specific implementation steps for dynamic regulation of the reproductive period in S5 are as follows: S51. Seedling Protection Management: After alfalfa emerges, timely cultivation and loosening of the soil should be carried out to break up soil compaction and remove weeds in the field to cut off soil capillaries and inhibit the upward migration of lower layer salts; at the same time, close monitoring of weather changes should be carried out. When a small amount of precipitation is forecast, light irrigation should be carried out through the drip irrigation system before the rain to prevent rainwater from pressing surface salts into the seedling root zone and causing salt damage. S52. Dynamic monitoring and feedback of salinity: Before and after alfalfa enters the branching stage, the soil salinity in the root zone is monitored regularly using a soil salinity rapid tester to accurately assess the risk of salt stress and provide a basis for subsequent control measures. S53. Branching Stage Growth Regulation: Based on the salt monitoring results, when the soil salt content in the root zone exceeds the tolerance threshold, apply organic fertilizer rich in soybean residue and fruit shells through trenching or hole application to continuously improve the rhizosphere environment and buffer salt stress; at the same time, in combination with the growth of alfalfa plants, supplement micronutrient water-soluble fertilizer or growth regulators through foliar spraying.

10. A planting method for promoting seedling growth and strengthening alfalfa in mildly to moderately saline-alkali land according to claim 5, characterized in that: The aerogel-embedded bacterial agent used in the seed inoculation treatment in S21 and the preparation of bacterial agent application in S31 is prepared from the following components by weight: The mixture comprises 18-22 parts of a salt- and alkali-tolerant composite microbial agent, 35-42 parts of a modified silica-based aerogel carrier, 10-14 parts of a humic acid synergist, and 4-5 parts of polyethylene glycol 4000 binder; wherein the salt- and alkali-tolerant composite microbial agent is a mixture of rhizobium and salt-solubilizing Pseudomonas aeruginosa at a weight ratio of 2:1, with an effective viable count ≥2.5 × 10⁻⁶. 9 CFU / g; Preparation steps of aerogel-encapsulated microbial agent: First, mix and stir the salt-alkali resistant composite microbial agent and humic acid synergist at a constant temperature of 25-30℃ for 15-20 minutes until uniform. Add polyethylene glycol 4000 binder to adjust the viscosity of the mixture to 500-800 mPa•s. Then, mix and coat the modified silicone-based aerogel carrier at high speed for 3-5 minutes. Afterward, dry at a low temperature of 55-58℃ until the moisture content is ≤7%. Finally, pulverize and screen to a particle size of 0.3-0.4 mm.

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