A light and moderate saline-alkali land alfalfa seedling preservation and growth promoting planting method

Abstract

The present application relates to saline-alkali soil treatment technical field, disclose a kind of light and moderate saline-alkali soil alfalfa seedling protection promotes the planting method of growth, comprising the following steps: S1, soil pretreatment and root zone microenvironment construction;S2, seed treatment and space-time double salt sowing;S3, fungicide application;S4, water and fertilizer integration and precision management;S5, dynamic regulation during growth period etc., by physical barrier and biological improvement combination constructs low salt root zone microenvironment, using slag salt layer inhibits salt up, organic layer improves fertility, and using salt-tolerant variety, climate window sowing and aerogel embedding fungicide enhance stress resistance;Through water and fertilizer integration drip irrigation realizes precision regulation, combined with intertillage and directional topdressing maintains root zone stability, finally significantly improve the uniformity of emergence, survival rate at seedling stage, promote the healthy growth of plant in saline-alkali soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of saline-alkali soil improvement, and particularly relates to a planting method for seedling protection and strong growth of alfalfa in light and moderate saline-alkali soil. BACKGROUND

[0002] China has a large area of light and moderate saline-alkali soil resources, and the development and utilization of the resources is of great significance to guarantee food safety and ecological safety. Alfalfa, as an important legume forage, has strong salt and alkali tolerance and is a pioneer crop for improving and utilizing saline-alkali soil. However, when alfalfa is directly planted in light and moderate saline-alkali soil, it still faces the severe challenge of soil salt stress, especially the soil salt return in spring and the salt accumulation in autumn, which seriously affects the seed germination, seedling survival and plant strong growth, and limits the benefits and popularization of alfalfa planting in saline-alkali soil. Therefore, it is of great significance to develop a planting method for seedling protection and strong growth of alfalfa in saline-alkali soil.

[0003] A patent CN117581759B discloses a saline-alkali soil improvement method based on an alfalfa, oat and okra high-efficiency cultivation mode. The saline-alkali soil improvement method adopts the alfalfa, oat and okra high-efficiency cultivation mode: alfalfa is first planted in the saline-alkali soil and overwinters after cutting; oat is then interplanted, and is harvested when mature; and okra is then planted in the oat area and is interplanted with alfalfa, and the aboveground part of the okra is laid after the okra is harvested. The alfalfa is cut multiple times during the planting period of the oat and the okra, and overwinters after the last cutting. This mode improves the yield and quality of alfalfa and enhances the improvement effect of the saline-alkali soil.

[0004] In view of the above and the prior art, the present application has the following defects: the existing planting method is extensive in alfalfa planting management, lacks effective construction and protection of the seed root zone microenvironment during planting, and the seedling root system directly suffers from salt stress, resulting in uneven emergence and low seedling survival rate, which affects the improvement effect of the saline-alkali soil to some extent. SUMMARY

[0005] The technical problem to be solved by the present application is that the alfalfa planting method in the prior art is extensive in management, lacks effective construction and protection of the seed root zone microenvironment, the seedling root system directly suffers from salt stress, resulting in uneven emergence and low seedling survival rate, and thus affecting the improvement effect of the saline-alkali soil. Therefore, the present application provides a planting method for seedling protection and strong growth of alfalfa in light and moderate saline-alkali soil.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solution: a planting method for seedling protection and strong growth of alfalfa in light and moderate saline-alkali soil, comprising the following implementation steps:

[0007] S1, soil pretreatment and root zone microenvironment construction: ridging in the field and digging a seeding trench on the ridge, laying a physical salt isolation layer of slag in the seeding trench from bottom to top, and an organic improvement layer mixed from bean dregs and fruit shells and soil;

[0008] S2, seed treatment and time-space double salt-avoiding sowing: selecting salt-tolerant alfalfa germplasm, using aerogel to coat the bacteria before sowing, choosing the spring before soil salt return or the autumn after rainfall as the salt-avoiding window period according to the climate characteristics of the planting area, and using the ridging dibbling method to sow the treated alfalfa seeds in the organic improvement layer;

[0009] S3, bacteria agent application: after sowing alfalfa seeds, applying the aerogel coated bacteria in the seeding trench;

[0010] S4, water and fertilizer integration and precision management: using a drip irrigation system for water and fertilizer integration supply, and dynamically adjusting the irrigation and fertilization scheme according to the water and fertilizer requirement law of alfalfa growth period, soil moisture content and meteorological information;

[0011] S5, dynamic regulation during growth period: cultivating and weeding during seedling stage, and applying organic fertilizer or foliar fertilizer during branching stage according to soil salt monitoring results.

[0012] Preferably, in S1, the specific implementation of soil pretreatment and root zone microenvironment construction is as follows:

[0013] S11, ridging operation: ridging operation is performed on the target field to form a planting ridge, the ridge height is 15-25 cm, and the ridge width is determined according to the seeding row spacing;

[0014] S12, digging a seeding trench: digging a seeding trench on the ridged ridge, the trench depth is 15-20 cm, the trench width is 10-15 cm, and the seeding trench provides space for subsequent construction of root zone microenvironment;

[0015] S13, laying a physical salt isolation layer: laying a layer of slag at the bottom of the seeding trench, the thickness is 5-8 cm, the slag layer acts as a physical barrier to prevent salt in the lower layer of soil from rising to the seed and seedling root zone through capillary action;

[0016] S14, constructing an organic improvement layer: laying an organic improvement layer made of bean dregs, fruit shell fragments and field soil mixed in a certain volume ratio on the physical salt isolation layer, the laying thickness is 5-10 cm, the organic improvement layer is used to provide organic matter and nutrients required for seedling growth and inhibit salt upwelling;

[0017] S15, soil backfilling: according to the need, covering a layer of 2-3 cm fine surface soil on the organic improvement layer for subsequent sowing operation and providing a contact interface for seed germination.

[0018] Preferably, in S14, the mixing volume ratio of the organic modified layer of bean dregs, shell broken material and field soil is 1:1:2 or 1:1:3.

[0019] Preferably, in S2, the specific implementation steps of seed treatment and time-space salt-avoiding sowing are as follows:

[0020] S21, seed biological inoculation treatment: selected salt-tolerant alfalfa seeds are mixed with aerogel-embedded bacterial agents in a certain proportion for inoculation treatment, and through seed dressing, coating or short-term seed soaking, beneficial microorganisms are attached to the seed surface to provide an initial biological protection barrier for seed germination and young root growth;

[0021] S22, salt-avoiding sowing period decision: based on the analysis of long-term climate data and soil water and salt transport law of the planting area to determine the best "salt-avoiding window period", which is usually selected in a specific period after the surface is thawed in spring, before the strong salt returns, or after the surface salt is leached by continuous rainfall in autumn to achieve "time salt avoidance";

[0022] S23, ridging point planting operation: in the determined salt-avoiding window period, using the matching agricultural machinery, precise point planting is carried out on the ridge with constructed root zone microenvironment, the seed treated with bacterial agents is sown in the organic modified layer of the sowing ditch and covered with appropriate fine soil, and the combination of "space salt avoidance" and "time salt avoidance" is completed.

[0023] Preferably, in S3, the specific implementation steps of bacterial agent synergistic application are as follows:

[0024] S31, bacterial agent application preparation: aerogel-embedded bacterial agents are mixed and diluted with appropriate amount of inert carriers such as fine sand, dry soil particles or organic materials to ensure that the bacterial agents are uniformly applied to the sowing ditch;

[0025] S32, precise trench application operation: after alfalfa sowing and soil covering, the diluted bacterial agents are applied along the sowing ditch in strip or hole form, so that the bacterial agents are positioned in the soil around the alfalfa seeds, ensuring that the bacterial agents fully contact the initial root system of alfalfa;

[0026] S33, bacterial agent activation: after bacterial agent application, a light irrigation is immediately carried out through the drip irrigation system to fully soak the root zone soil where the bacterial agents are located, so as to activate the microorganisms embedded in the aerogel, promote the germination of the microorganisms in the aerogel and start colonization, thereby rapidly forming a dominant bacterial population in the initial rhizosphere of alfalfa.

[0027] Preferably, in S4, the specific implementation steps of water and fertilizer integration and precise management are as follows:

[0028] S41, system installation and commissioning: lay out the shallow buried drip irrigation system, bury the drip irrigation tape at a certain depth near the seeding row on the ridge, and connect and commission it with the head hub including the water pump, filter, and fertilizer tank to ensure normal operation of the drip irrigation system;

[0029] S42, water and fertilizer formula and preparation: according to the fertilizer requirement characteristics of alfalfa at different growth stages, prepare special liquid fertilizer containing appropriate proportions of nitrogen, phosphorus, potassium, and necessary trace elements, and inject it into the fertilizer tank for standby;

[0030] S43, precise irrigation decision and execution: based on real-time monitoring of soil moisture sensor data, judgment of future weather forecast information, and growth simulation output of the alfalfa model, dynamically make irrigation decisions to determine irrigation timing, irrigation quota, and whether fertilization is needed, and execute the decisions through the control system to achieve precise irrigation and water-fertilizer coupling supply on demand;

[0031] S44, salt leaching control operation: during the key growth period, if there is a moderate amount of natural precipitation, irrigation amount is actively reduced to fully utilize the precipitation; if it is a continuous drought, a moderate amount of "salt washing irrigation" is implemented through the drip irrigation system, so that the water infiltrates below the alfalfa root zone, and the excess salt in the soil is leached away to control the salt concentration in the alfalfa root layer;

[0032] Preferably, the control system makes precise irrigation on demand based on the irrigation decision algorithm of the soil water balance model, and the calculation formula is as follows:

[0033]

[0034] In the formula, n represents the number of decision-making days; i represents the index variable, representing the i-th day in the decision-making period; E i represents the crop water requirement on the i-th day; W i represents the root zone water storage on the i-th day; P i represents the effective precipitation on the i-th day; and D represents the soil allowable deficit.

[0035] Preferably, in S44, the drip irrigation system controls water quantity based on the salt washing irrigation amount algorithm, and the calculation formula is as follows:

[0036]

[0037] In the formula, k represents the three layers of soil in the root zone, corresponding to the salt barrier layer, the improved layer, and the topsoil layer; S k represents the measured salt content of the k-th layer of soil; S t represents the alfalfa root zone salt tolerance threshold; p k represents the bulk density of the k-th layer of soil; h k represents the thickness of the k-th layer of soil; C w represents the mineralization degree of irrigation water; and m kK represents the k-th layer soil permeability coefficient.

[0038] Preferably, in S5, the specific implementation steps of the growth period dynamic regulation are as follows:

[0039] S51, seedling management: after the alfalfa emerges, timely implement the cultivation and soil loosening operation, cut off the soil capillary to inhibit the downward migration of the lower salt by breaking the soil hardening and removing the field weeds; at the same time, closely monitor the weather changes, when a small amount of rainfall is forecast, implement light irrigation through the drip irrigation system before the rain to prevent the surface salt from being pressed to the seedling root zone to cause salt damage;

[0040] S52, salt dynamic monitoring and feedback: before and after the alfalfa enters the branching period, the soil salt content in the root zone is monitored regularly by using the soil salt content tester to accurately assess the salt stress risk and provide a basis for subsequent regulation measures;

[0041] S53, branching period promotion regulation: according to the salt monitoring results, when the root zone soil salt content exceeds the tolerance threshold, the organic fertilizer rich in bean dregs and shell materials is applied by trenching or hole application to continuously improve the rhizosphere environment and buffer the salt stress; at the same time, combined with the growth of alfalfa plants, the trace element water-soluble fertilizer or growth regulator is supplemented by foliar spraying.

[0042] Preferably, the aerogel embedded microbial agent used in the seed inoculation treatment in S21 and the microbial agent preparation in S31 is prepared from the following components by weight:

[0043] The salt-tolerant composite microbial agent is 18-22 parts, the modified silica-based aerogel carrier is 35-42 parts, the humic acid synergistic additive is 10-14 parts, and the polyethylene glycol 4000 binder is 4-5 parts; wherein the salt-tolerant composite microbial agent is a mixture of rhizobium and salt-tolerant pseudomonas in a weight ratio of 2:1, and the effective viable bacterial count is ≥2.5×10 9 CFU / g;

[0044] The preparation steps of the aerogel embedded microbial agent are as follows: first, mix and stir the salt-tolerant composite microbial agent and the humic acid synergistic additive at 25-30 DEG C constant temperature environment for 15-20 minutes until uniform, add the polyethylene glycol 4000 binder to adjust the viscosity of the mixture to 500-800 mPa s, then mix with the modified silica-based aerogel carrier at high speed for 3-5 minutes, then dry at 55-58 DEG C low temperature to ≤7% moisture content, and finally crush and screen to 0.3-0.4 mm.

[0045] In the present application, through the multi-level cooperation of physical barrier, biological improvement and dynamic management, a low-salt root zone microenvironment conducive to alfalfa growth is constructed. The slag layer effectively inhibits the upward movement of salt, and the organic improvement layer improves soil fertility and buffering performance, laying the foundation for seed germination; by selecting salt-tolerant varieties, using climate window period sowing and secondary application of aerogel embedded bacterial agent, the salt tolerance and stress resistance of plants are significantly enhanced; relying on the water and fertilizer integrated drip irrigation system, the dynamic balance of water and fertilizer supply and salt leaching is realized according to soil moisture content, crop demand law and meteorological data; combined with intertillage and targeted topdressing during the growth period, the root zone environment is continuously maintained stable; the uniformity of alfalfa emergence and the survival rate of seedling stage are greatly improved, and the healthy growth of plants is promoted, providing a reliable technical approach for the efficient use of saline-alkali land. BRIEF DESCRIPTION OF DRAWINGS

[0046] The disclosure of the present application is explained 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 the present application. In the drawings, the same reference numerals are used to refer to the same parts:

[0047] Figure 1 The overall flowchart of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application;

[0048] Figure 2 The S1 step flowchart of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application;

[0049] Figure 3 The S2 step flowchart of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application;

[0050] Figure 4 The S3 step flowchart of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application;

[0051] Figure 5 The S4 step flowchart of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application;

[0052] Figure 6 The S5 step flowchart of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application;

[0053] Figure 7 The key data comparison monitoring intention of the alfalfa planting method for seedling protection and growth promotion in light and medium saline-alkali land according to the present application. DETAILED DESCRIPTION

[0054] It is easy to understand that, according to the technical solutions of the present application, those skilled in the art can propose a plurality of structure modes and implementation modes which can be replaced with each other without changing the essential spirit of the present application. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solutions of the present application, and should not be regarded as the whole or as the limitation or restriction of the technical solutions of the present application.

[0055] Referring to Figure 1 As shown in the drawings, the present application provides a technical solution: a planting method for improving the survival rate and promoting the growth of alfalfa in light and moderate saline-alkali soil. The method uses innovative techniques in key links such as soil pretreatment, seed treatment, sowing, water and fertilizer management, and growth period regulation, aiming to effectively cope with salt stress in saline-alkali soil, significantly improve the survival rate of alfalfa at seedling stage and promote its healthy growth. The specific implementation steps are as follows:

[0056] Step one, soil pretreatment and root zone microenvironment construction: ridging in the field and digging sowing ditch on the ridge, laying physical salt isolation layer formed by slag in the sowing ditch from bottom to top, and organic improvement layer formed by mixing bean dregs and fruit shells with soil;

[0057] Step two, seed treatment and time-space double salt-avoiding sowing: selecting salt-tolerant alfalfa germplasm, using aerogel-embedded bacterial agent for alfalfa seed inoculation treatment before sowing, selecting spring before soil salt return or autumn after rainfall as the salt-avoiding window period according to the climate characteristics of the planting area, and using ridge point sowing method to sow the treated alfalfa seeds in the organic improvement layer;

[0058] Step three, bacterial agent application: after sowing alfalfa seeds, apply the aerogel-embedded bacterial agent in the sowing ditch;

[0059] Step four, water and fertilizer integration and precision management: using drip irrigation system for water and fertilizer integration supply, and dynamically adjusting the irrigation and fertilization scheme according to the water and fertilizer requirement law of alfalfa growth period, soil moisture regime and meteorological information;

[0060] Step five, dynamic regulation during growth period: intertillage and weeding during seedling stage, and applying organic fertilizer or foliar fertilizer according to the soil salt monitoring results during branching period.

[0061] Specifically, in the soil pretreatment stage, a low-salt root zone environment is formed by layering the salt barrier and the improvement layer. The slag layer blocks the upward movement of salt, and the organic layer provides nutrient buffering. Salt-tolerant varieties are selected and inoculated with bacterial agents during seeding. The climate window is used to reduce surface salt, and the dibbling method ensures that the seeds are planted in the improved layer. The bacterial agent is applied twice to form a rhizosphere protection barrier. The drip irrigation system adjusts water and fertilizer based on real-time data to meet the growth needs and leach excess salt. During the growth period, tillage is used to cut off the capillary to prevent salt from returning. Combined with monitoring results, fertilizers are applied to maintain a stable root zone environment. The various links work together to prevent salt damage from multiple dimensions, including physical barriers, biological protection, and dynamic control. Through the above scheme, the migration path of salt to the root zone is effectively blocked. The organic improvement layer buffers salt stress, and precise seeding avoids the salt peak period. The synergistic application of bacterial agents enhances plant salt tolerance, and dynamic water and fertilizer management maintains salt balance in the root zone. The uniformity of alfalfa seedling emergence and seedling survival rate in saline-alkali soil is improved, and the plant growth in a saline environment is promoted. A reliable solution is provided for the efficient use of saline-alkali land resources.

[0062] Referring to Figure 1 , Figure 2 and Figure 7 , in the present embodiment: the present application further proposes a specific method for soil pretreatment and root zone microenvironment construction in the process of alfalfa planting in light and moderate saline-alkali land in step one, including the steps of ridging, digging a seeding trench, laying a physical salt barrier, constructing an organic improvement layer, and soil backfilling:

[0063] S11, ridging operation: perform ridging operation on the target field to form planting ridges, with a ridge height of 15-25 cm and a ridge width determined according to the seeding row spacing. This is done to raise the seeding site and use the water and salt movement law to achieve spatial "salt avoidance".

[0064] S12, digging a seeding trench: dig a seeding trench on the ridges after ridging, with a trench depth of 15-20 cm and a trench width of 10-15 cm. The seeding trench provides space for subsequent construction of the root zone microenvironment.

[0065] S13, laying a physical salt barrier: lay a layer of slag at the bottom of the seeding trench, with a thickness of 5-8 cm. This slag layer acts as a physical barrier to effectively prevent the upward movement of salt in the lower layer of soil to the seed and seedling root zone through capillary action.

[0066] S14, constructing an organic improvement layer: on the physical salt barrier, lay an organic improvement layer made of bean dregs, crushed fruit shells, and field soil mixed in a certain volume ratio (preferably 1:1:2 to 1:1:3), with a laying thickness of 5-10 cm. This layer can provide organic matter and nutrients needed for seedling growth, improve soil aggregate structure, and inhibit salt upwelling.

[0067] S15, soil backfilling: according to the need, a layer of 2-3 cm fine topsoil is covered on the organic improvement layer to facilitate subsequent sowing operation and provide a more suitable interface for seed germination.

[0068] Specifically, the root zone microenvironment is constructed by a layered structure to form a salt regulation system that synergizes physical barriers and biological improvement. On the basis of ridge culture, a seeding trench is excavated, and the slag layer is used to cut off the salt capillary rise path. The organic improvement layer continuously releases humic acid through the decomposition of organic matter, inhibits salt ion activity, and improves soil aggregate structure. Surface soil coverage avoids direct contact of seeds with high-concentration organic matter, ensuring the water and gas balance required for germination. The thickness of each layer is optimized to maintain suitable cultivation depth while ensuring salt isolation effect and avoiding root development obstruction. Through the above scheme, the salt concentration in the root zone of alfalfa seedlings is effectively controlled, reducing the direct stress of salt ions on seed germination and root growth. The slag layer blocks the underground salt rise channel, and the organic improvement layer further inhibits salt migration through adsorption. Surface soil coverage ensures the contact quality between seeds and soil. This method not only inhibits salt damage but also provides stable nutrient supply for seedlings, significantly improving the emergence rate and seedling survival rate of alfalfa in saline-alkali soil.

[0069]

[0070] Table 1 is a comparison monitoring table of key data for alfalfa seedling survival and growth promotion in light to moderate saline-alkali soil

[0071]

[0072] Table 2 is a comparison table of alfalfa growth and soil index dynamics in light to moderate saline-alkali soil

[0073]

[0074] Table 3 is a comparison table of alfalfa planting inputs and benefits in light to moderate saline-alkali soil

[0075] As shown in Table 1 above, this method exhibits significant advantages at each stage of the entire growth period: during sowing and emergence, the emergence rate is higher, the emergence is faster, and the root zone salinity is more efficiently reduced, solving the problem of "difficult emergence" of alfalfa in saline-alkali soil; the seedling survival rate is significantly improved, and the seedling growth is more vigorous; during branching, the alfalfa has stronger salt-alkali stress resistance and more vigorous growth; during present budding, the biomass accumulation speed is faster, laying a solid foundation for high yield; during mowing, not only is the yield higher and the quality better (high crude protein content), but also the regenerative buds can efficiently germinate, realizing continuous production.

[0076] The above Table 2 shows that under the method, the growth indexes of alfalfa such as plant height, root length and branch number are better than those of the ordinary planting method, the whole plant is more robust and grows more coordinately; at the same time, the salt content of the root zone soil is more stable and always at a lower level, and the soil pH is also more suitable for alfalfa growth, the continuously improved rhizosphere environment reduces the burden of alfalfa growth throughout the cycle, and the soil salinity stress under the ordinary method is more prominent, which seriously limits the growth potential of alfalfa.

[0077] The above Table 3 shows that although the input cost of the method is higher than that of the ordinary planting method, the per mu income is greatly increased by improving the yield (fresh grass and dry grass yield is significantly higher) and quality (crude protein content is better), the cost input can obtain excess return through higher output and better commodity value, the economic benefit is obvious, and a virtuous cycle of "high input for high output and high income" is achieved.

[0078] Referring to Figure 1 and Figure 3 , in the embodiment, the application further proposes specific implementation steps of seed treatment and space-time salt-avoiding sowing in step two:

[0079] S21, seed biological inoculation treatment: selected salt-tolerant alfalfa seeds are mixed with aerogel embedded bacterial agent according to a predetermined ratio for inoculation treatment, which can be through seed dressing, coating or short-term seed soaking, so that beneficial microorganisms adhere to the surface of the seeds, providing an initial biological protection barrier for seed germination and young root growth.

[0080] S22, salt-avoiding sowing period decision: based on the analysis of long-term climate data and soil water and salt transport law of the planting area, the best "salt-avoiding window period" is determined. The window period is usually selected in a specific period after the surface thawing in spring, before the strong salt return, or after the surface salt leaching by continuous rainfall in autumn, to realize "time salt avoidance".

[0081] S23, ridging dibbling operation: in the determined salt-avoiding window period, the matching farm tools are used to accurately dibble on the ridge where the root zone microenvironment has been constructed (step S1 is completed). The seed treated with the bacterial agent is sown in the organic improved layer of the sowing ditch, and an appropriate amount of fine soil is covered, to realize the combination of "space salt avoidance" (avoiding the surface salt accumulation by using the ridge structure) and "time salt avoidance".

[0082] Specifically, the microbial protective layer formed on the seed surface reduces the salt concentration in the rhizosphere by secreting organic acids, exopolysaccharides and other substances, while enhancing the seed resistance to adversity. The selection of the sowing window period makes the seed germination avoid the peak period of soil salt concentration, and the physical barrier and nutrient supply of the organic improved layer further weaken the salt stress. The ridging dibbling locates the seeds in the three-dimensional salt prevention system constructed by the salt isolation layer and the improved layer, forming a spatial dimension salt avoidance mechanism. The time dimension sowing decision and the spatial dimension microenvironment construction work together to achieve double avoidance of salt stress. Through the above scheme, the salt contact risk of seed germination stage is effectively reduced, and the microbial metabolic activity continuously relieves the salt stress of seedling rhizosphere. The time and space double-avoidance strategy enables the seedling to complete the key growth stage in the low salt window period. Precise control of the sowing position ensures that the root development is in the optimized microenvironment, significantly improving the alfalfa emergence rate and seedling survival rate in saline-alkali soil.

[0083] Reference Figure 1 and Figure 4 As shown in the embodiment, the application further proposes the specific implementation steps of the third step of synergistic application of microbial agents: in the microbial agent application preparation stage, the aerogel-embedded microbial agents are mixed and diluted with inert carriers; in the precise trenching operation stage, the diluted microbial agents are strip-applied or hole-applied along the seeding trench; and in the microbial agent activation stage, light irrigation is performed through the drip irrigation system.

[0084] S31, microbial agent application preparation: the aerogel-embedded microbial agents are mixed and diluted with an appropriate amount of inert carriers (such as fine sand, dry soil particles or organic materials) to ensure that the microbial agents can be uniformly applied to the seeding trench.

[0085] S32, precise trenching operation: after completing seeding and soil covering, the diluted microbial agents are strip-applied or hole-applied along the seeding trench to ensure that the microbial agents are located in the soil around the seeds and can fully contact the alfalfa primary root system.

[0086] S33, microbial agent activation: after the application of microbial agents, light irrigation is immediately performed through the drip irrigation system to fully soak the soil in the root zone where the microbial agents are located, activate the microorganisms embedded in the aerogel, promote their germination and start colonization, and thus rapidly form a dominant microbial community in the rhizosphere.

[0087] Specifically, the preparation stage of bacterial agent application reduces the concentration of bacterial agent by mixing operation of inert carrier, avoids the toxicity of high concentration bacterial agent to seeds, and realizes uniform distribution of bacterial agent by the dispersion of carrier. The precise ditching operation stage adopts strip or hole application method, so that the bacterial agent is precisely applied to the soil around the seeds to form a bacterial agent distribution zone around the seeds, and ensure that the initial root system is in full contact with the bacterial agent during development. The bacterial agent activation stage implements light irrigation through the drip irrigation system, and the water infiltration promotes the swelling of aerogel carrier to release microorganisms, while driving the bacterial agent to diffuse to the rhizosphere area, and the double action accelerates the germination and colonization of microorganisms. The three steps are sequentially linked to form a progressive technical chain of bacterial agent dilution and dispersion, spatial positioning, and water activation. Through the above scheme, the problem of low colonization efficiency of microorganisms caused by uneven application of bacterial agent is effectively solved, so that the bacterial agent is uniformly distributed in the soil around the seeds, the precise positioning ensures that the bacterial agent is in full contact with the root system, and the water activation accelerates the colonization process of microorganisms, and finally forms a dominant microbial community in the rhizosphere of alfalfa, and builds a biological barrier to resist salt stress.

[0088] The application further provides an aerogel-embedded bacterial agent used in seed inoculation treatment and bacterial agent application preparation, which is prepared from the following components by weight: 18-22 parts of salt-tolerant and alkali-tolerant composite microbial agent, 35-42 parts of modified silica-based aerogel carrier, 10-14 parts of humic acid synergistic additive, and 4-5 parts of polyethylene glycol 4000 binder; wherein the salt-tolerant and alkali-tolerant composite microbial agent is a mixture of rhizobium and salt-tolerant pseudomonas in a weight ratio of 2:1, and the effective viable bacterial count is ≥2.5×10 9 CFU / g; the preparation steps of the aerogel-embedded bacterial agent include mixing and stirring the salt-tolerant and alkali-tolerant composite microbial agent and the humic acid synergistic additive, adding the polyethylene glycol 4000 binder to adjust the viscosity, and then mixing and coating with the modified silica-based aerogel carrier at high speed, and then crushing and screening to a specific particle size after low-temperature drying.

[0089] The salt-tolerant and alkali-tolerant composite microbial agent refers to a mixed microbial community composed of rhizobium and salt-tolerant pseudomonas, which can be realized by centrifugal collection of bacterial bodies after liquid fermentation culture. The rhizobium promotes the nitrogen fixation ability of alfalfa, and the salt-tolerant pseudomonas directly decomposes soil salt ions. The modified silica-based aerogel carrier refers to a porous silica-based material that has been hydrophobically modified, which can be prepared by sol-gel method and then surface treated with trimethylchlorosilane, and its porous structure provides physical protection for microorganisms and blocks salt erosion. The humic acid synergistic additive refers to humic acid substances extracted from weathered coal, which can be obtained by alkali dissolution and acid extraction and then spray drying, and reduces the rhizosphere salt concentration through ion exchange. The polyethylene glycol 4000 binder refers to a polyethylene glycol polymer with a molecular weight of 4000, which can be mixed with other components by melting method to adjust the viscosity of the mixture and enhance the particle formability.

[0090] Specifically, the saline-alkali resistant composite microbial agent is mixed with humic acid synergistic additives under constant temperature conditions, so that the humic acid uniformly wraps the surface of the microbial body; the addition of polyethylene glycol binder makes the mixture form a suitable viscosity, facilitating subsequent carrier coating; the modified silica-based aerogel carrier embeds the microbial agent-humic acid complex in its porous structure during high-speed mixing, forming a physical barrier; the low-temperature drying process controls the water evaporation rate to avoid microbial inactivation caused by high temperature; and the final particle size after crushing and screening ensures the slow release of the microbial agent in the soil. The synergistic effect of rhizobium and salt-tolerant pseudomonas forms a dual regulation mechanism in the rhizosphere of alfalfa, and the aerogel carrier blocks salt while maintaining the microenvironment required for microbial metabolism, and humic acid continuously regulates the ion balance in the rhizosphere.

[0091] Referring to Figure 1 and Figure 5 In the present embodiment, the present application further proposes the specific implementation steps of water and fertilizer integration and precision management in step four:

[0092] S41, system installation and debugging: lay out the shallow buried drip irrigation system, bury the drip irrigation tape (pipe) at a certain depth underground near the seeding row on the ridge, and connect and debug the first hub (including water pump, filter, fertilizer tank, etc.) to ensure that the system can operate normally.

[0093] S42, water and fertilizer formula and preparation: according to the fertilizer requirement characteristics of different growth stages of alfalfa (such as seedling stage, branching stage, budding stage, etc.), special liquid fertilizer containing appropriate proportions of nitrogen, phosphorus, potassium and necessary trace elements is prepared, and is injected into the fertilizer tank for standby.

[0094] S43, precision irrigation decision and execution: based on real-time monitoring of soil moisture sensor data, judgment of future weather forecast information (especially precipitation probability and evaporation), and growth simulation output of alfalfa model, dynamic irrigation decision is made, including determining irrigation time, irrigation quota and whether fertilization is needed. Execute the decision through the control system to realize precision irrigation and water and fertilizer coupling supply as needed.

[0095] S44, salt leaching and salt control operation: during the key growth period, if there is a moderate amount of natural precipitation, the irrigation amount is actively reduced to make full use of precipitation; if it is continuous drought, a moderate amount of "salt washing irrigation" is implemented through the drip irrigation system, so that the water infiltrates below the root zone, and the excess salt in the soil is leached away to control the salt concentration in the root layer.

[0096] Specifically, the underground layout of the shallow buried drip irrigation system effectively blocks the upward movement of salt caused by surface evaporation, allowing irrigation water to directly act on the root zone soil. Dynamic adjustment of water and fertilizer formula avoids nutrient waste and salt surge caused by traditional spreading by matching the alfalfa growth period fertilizer requirement curve. The precise irrigation decision module integrates real-time soil moisture monitoring data, future 72-hour precipitation probability, and transpiration prediction values output by the alfalfa growth model, calculates daily irrigation demand through the soil water balance equation, and realizes the dynamic balance of on-demand water supply and salt leaching. The salt leaching control operation starts the salt washing mode during the dry period, forms a downward water flow by increasing the single irrigation amount, and migrates the salt accumulated in the root layer to the deep soil, while reducing the irrigation amount before the arrival of precipitation to fully utilize the natural salt leaching of rainwater. Through the above scheme, the problem of root zone salt accumulation caused by extensive irrigation in alfalfa planting in saline-alkali soil is solved, and through the combination of underground drip irrigation system and precise regulation of water and fertilizer, a controllable salt leaching mechanism is formed while ensuring the water and nutrient supply of plants. The application of the dynamic decision model makes the irrigation strategy adapt to environmental changes in real time, avoiding the salt stress caused by traditional fixed irrigation mode in dry period, and preventing nutrient loss caused by excessive irrigation in rainy season. The integrated management system effectively maintains the suitable water and salt environment of alfalfa root zone, and provides reliable technical support for the growth of alfalfa seedlings in saline-alkali soil.

[0097] The application further proposes an irrigation decision algorithm based on the soil water balance model for precise irrigation on demand by the control system, and the calculation formula is as follows:

[0098]

[0099] In the formula, n represents the number of decision cycle days; i represents the index variable, representing the day in the decision cycle; E i represents the crop water requirement on the i-th day; W i represents the root zone water storage on the i-th day; P i represents the effective precipitation on the i-th day; D represents the allowable soil deficit.

[0100] The decision cycle days refer to the range of consecutive days for making irrigation plans, which can be determined by dividing the alfalfa growth stages, for example, 5 days for the seedling stage and 7 days for the branching stage, and the period length is dynamically adjusted to adapt to the changes in water demand at different growth stages. The crop water requirement refers to the daily water consumption per unit area of alfalfa at a specific growth stage, which can be calculated by using the Penman formula combined with crop coefficients to reflect the comprehensive water consumption characteristics of plant transpiration and soil evaporation. The root zone water storage refers to the effective soil moisture content in the alfalfa root distribution layer, which can be obtained by real-time monitoring by soil moisture sensors, and is used to represent the actual soil water supply capacity. The effective precipitation refers to the rainfall that can be absorbed by the soil and used by crops, which can be calculated by multiplying the rainfall by the runoff coefficient and the infiltration coefficient, and is used to quantify the supplement of natural precipitation to irrigation demand. The soil allowable deficit refers to the minimum water storage threshold for maintaining normal growth of alfalfa, which can be determined by the difference between the field water capacity and the wilting coefficient, and is used to balance water saving demand and plant drought tolerance.

[0101] Specifically, the algorithm realizes dynamic irrigation decision-making by establishing an iterative calculation framework with multiple parameters coupled. After setting the decision cycle, the system collects root zone water storage data every day and calculates the crop water requirement for the day, while combining weather forecasts to obtain effective precipitation prediction values. By accumulating the crop water requirement and the root zone water storage change amount day by day, irrigation instructions are triggered when the cumulative water deficit exceeds the soil allowable threshold. This calculation process fully considers the soil moisture replenishment effect of natural precipitation, avoiding the problem of excessive or insufficient irrigation caused by ignoring meteorological factors in traditional fixed irrigation modes. In saline-alkali soil environment, the algorithm can adjust the irrigation amount according to the real-time soil moisture content, ensuring sufficient water leaching of root zone salt and preventing excessive irrigation causing deep salt leaching difficulty. Through the above scheme, the irrigation strategy can be dynamically adjusted according to the actual growth demand of alfalfa and the change of environmental conditions, maintaining the water-salt balance in the root zone in saline-alkali soil environment. The algorithm effectively avoids the problem of salt concentration caused by insufficient irrigation, and prevents the problem of incomplete salt leaching caused by excessive irrigation, creating a stable root zone water environment for alfalfa growth. By precisely matching water supply and crop demand, the risk of salt stress is reduced, and the efficiency of water resource utilization is improved.

[0102] The present application further proposes a water quantity control method for the drip irrigation system based on the salt leaching irrigation amount algorithm, and the calculation formula is as follows:

[0103]

[0104] In the formula, k represents the three layers of soil in the root zone, corresponding to the salt isolation layer, the improved layer and the topsoil layer; S k represents the measured salt content of the kth layer of soil; S t represents the salt tolerance threshold of the alfalfa root zone; p kh 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.

[0105] 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.

[0106] 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.

[0107] 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:

[0108] S51, seedling stage seedling management: timely implement the shallow tillage operation after the alfalfa emergence, cut off the soil capillary by breaking the soil hardening and removing the field weeds, effectively inhibit the lower salt migration; At the same time, closely monitor the weather changes, when there is a small amount of rainfall, before the rain through the drip irrigation system to implement light irrigation, prevent rain salt in the surface layer of young seedling root zone and cause salt damage.

[0109] S52, salt dynamic monitoring and feedback: before and after the alfalfa into the branching period, using soil salt content meter regularly monitor the root zone, accurate assessment of salt stress risk, for the follow-up control measures to provide the basis.

[0110] S53, branching period, promote the regulation: according to the salt monitoring results, when the root zone soil salt content exceeds the tolerance threshold, through the ditch or hole application of rich bean dregs and shell material of organic fertilizer, continuous improvement of rhizosphere environment and buffer salt stress; At the same time, combined with the growth of alfalfa, through the leaf spraying way to supplement trace element water soluble fertilizer or growth regulator, enhance the plant resistance, promote the healthy growth.

[0111] Among them, the shallow tillage operation is to turn the surface soil by mechanical or manual way to destroy the hardening layer of agricultural operation, can be used in the seedling stage by rotary cultivator or hoe shallow tillage, through cutting off the soil capillary pore to reduce the water evaporation path, so as to inhibit the salt with water up to the root zone. Among them, light irrigation is to wet the surface soil with a small amount of water, can be through the drip irrigation system before the rain to add equivalent to 5-8 mm of precipitation irrigation water, in the soil surface layer forms a water barrier to prevent rainwater infiltration to the root zone. Among them, the salt dynamic monitoring is to use the conductivity method or spectral method to quickly determine the salt concentration of soil solution, can be used in the root zone of different depth layer sampling detection by portable soil salt content meter, real-time acquisition of salt distribution data to evaluate the stress risk level. Among them, the bean dregs and shell material organic fertilizer is the fertilizer made by mixing and fermenting the by-products of beans and nut shell broken material, can be used to mix the bean dregs and walnut shell after composting, using its porous structure to adsorb salt ions and release humic acid to improve the soil physical and chemical properties. Among them, the leaf spraying is to spray the nutrient solution directly to the plant leaf surface, can be used in the morning or evening by unmanned aerial vehicle or backpack sprayer to implement the operation, through the stomata directly absorb trace elements to avoid the interference of soil salt on the root nutrient absorption.

[0112] Specifically, the seedling stage forms a double salt barrier through physical loosening and water regulation, the cultivation destroys the soil capillary structure to block the salt upward channel, and the irrigation before rain uses the water gradient difference to form a reverse salt compression effect. Before the branching stage, a data feedback mechanism is established through high-frequency salt monitoring, and a three-dimensional root zone salt distribution model is constructed by using a speed tester to sample multiple points to accurately identify high-risk areas. According to the salt threshold, different measures are taken during the branching stage, organic fertilizer is applied in the ditch to form a rhizosphere buffer zone through ion adsorption and organic matter release, and foliar spraying bypasses the salinized soil to directly supplement the plant nutrient demand. The measures at each stage form a closed-loop management chain, which not only controls the salt dynamic balance but also enhances the plant stress resistance.

[0113] In some embodiments, the depth of cultivation loosening can be controlled at 3-5 cm to avoid damaging the seedling roots; the light irrigation amount can be adjusted according to the soil texture, for example, 5 mm irrigation amount for sandy soil and 8 mm for clay soil; the salt monitoring frequency can be set to once every 7-10 days, and increased to once every 3 days after consecutive sunny days or rainfall; the organic fertilizer application amount can be calculated at 2-3 tons per hectare, and the ditch is opened and applied 15 cm away from the seeding ditch; the foliar fertilizer spraying concentration can be controlled between 0.2%-0.5%, and a chelated water-soluble fertilizer containing zinc and boron trace elements is selected. Through the above scheme, the migration path of salt to the root zone during the seedling stage is effectively blocked, and the secondary salinization hazard caused by precipitation is avoided; through high-frequency salt monitoring, real-time data support is provided for control decision-making, ensuring that targeted improvement measures are implemented in time during the key stage of branching; organic fertilizer deep application and foliar nutrient supplementation form a synergistic effect, reducing the salt concentration in the root zone while ensuring plant nutrient supply, ultimately achieving the dual goals of improving the survival rate of alfalfa in saline-alkali soil and the healthy growth of plants.

[0114] The technical scope of the present application is not limited to the content in the above description, and those skilled in the art can make various modifications and modifications to the above embodiments without departing from the technical idea of the present application, and these modifications and modifications should be within the protection scope of the present application.

Claims

1. A light and medium saline-alkali soil alfalfa seedling preservation and growth promotion planting method, characterized in that, The method comprises the following implementation steps: S1, soil pretreatment and root zone microenvironment construction: ridging in the field and digging seeding ditch on the ridge, laying physical salt isolation layer formed by slag in the seeding ditch from bottom to top and organic improvement layer mixed by bean dregs and fruit shells and soil; S2, seed treatment and space-time salt-avoiding sowing: selecting salt-tolerant alfalfa germplasm, using aerogel to inoculate bacteria before sowing, selecting spring before soil salt returning or autumn after precipitation as salt-avoiding window period according to climate characteristics of planting area, and sowing treated alfalfa seeds in the organic improvement layer by ridging dibbling; S3, bacteria agent application: after sowing alfalfa seeds, applying the aerogel bacteria agent in the seeding ditch; S4, water and fertilizer integration and precision management: using drip irrigation system for water and fertilizer integration supply, and dynamically adjusting irrigation and fertilization scheme according to alfalfa water and fertilizer demand law, soil moisture content and meteorological information; S5, dynamic regulation during growth period: cultivating and weeding during seedling stage, and applying organic fertilizer or foliar fertilizer during branching period according to soil salt monitoring result; In S3, the specific implementation steps of bacteria agent application are as follows: S31, bacteria agent application preparation: mixing and diluting the aerogel bacteria agent with inert carrier including appropriate amount of fine sand, dry soil particles or organic material to ensure that the bacteria agent is uniformly applied to the seeding ditch; S32, precise ditch application operation: after completing alfalfa sowing and soil covering, immediately applying the diluted bacteria agent along the seeding ditch by strip application or hole application, so that the bacteria agent is located in the soil around the alfalfa seed, ensuring that the bacteria agent fully contacts with the alfalfa primary root system; S33, bacteria agent activation: after applying the bacteria agent, immediately performing light irrigation through the drip irrigation system to fully soak the root zone soil where the bacteria 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 quickly form dominant bacteria group in the alfalfa primary rhizosphere; In S5, the specific implementation steps of dynamic regulation during growth period are as follows: S51, seedling management: after alfalfa germination, timely implementing cultivation and soil loosening operation to cut off soil capillary to inhibit the upward migration of lower layer salt by breaking soil hardening and removing field weeds; at the same time, closely monitoring weather changes, and when a small amount of precipitation is predicted, performing light irrigation through the drip irrigation system before the rain to prevent rainwater from pressing the surface layer salt to the alfalfa seedling root zone to cause salt damage; S52, dynamic salt monitoring and feedback: before and after alfalfa enters the branching period, regularly monitoring the salt content of the root zone soil by using soil salt rapid tester to accurately evaluate the salt stress risk and provide basis for subsequent regulation measures; S53, branching period regulation: according to the salt monitoring result, when the salt content of the root zone soil exceeds the tolerance threshold, applying organic fertilizer rich in bean dregs and fruit shell materials by ditch application or hole application to continuously improve the rhizosphere environment and buffer the salt stress; at the same time, combining with the growth of alfalfa plants, supplementing trace element water-soluble fertilizer or growth regulator by foliar spraying; The aerogel bacteria agent is prepared from the following components by weight: The salt-tolerant composite microbial agent 18-22 parts, the modified silica-based aerogel carrier 35-42 parts, the humic acid synergistic additive 10-14 parts, and the polyethylene glycol 4000 binder 4-5 parts; wherein the salt-tolerant composite microbial agent is a mixture of rhizobium and salt-tolerant pseudomonas in a weight ratio of 2:1, and the effective viable bacterial count is ≥2.5×10 9 CFU / g. 9 CFU / g.

2. The method according to claim 1, wherein the method is characterized by: In S1, the specific implementation of soil pretreatment and root zone microenvironment construction is as follows: S11, ridging operation: perform ridging operation on the target field to form planting ridge, the ridge height is 15-25 cm, and the ridge width is determined according to the seeding row spacing; S12, digging seeding ditch: dig a seeding ditch on the ridge after ridging, the ditch depth is 15-20 cm, the ditch width is 10-15 cm, and the seeding ditch provides space for subsequent construction of root zone microenvironment; S13, laying physical salt barrier layer: lay a layer of slag with a thickness of 5-8 cm at the bottom of the seeding ditch, and the slag layer acts as a physical barrier to prevent salt in the lower layer of soil from rising to the seed and seedling root zone through capillary action; S14, construction of organic improvement layer: lay an organic improvement layer made of bean dregs, fruit shell broken material and field soil in a certain volume ratio on the physical salt barrier layer, and the laying thickness is 5-10 cm, and the organic improvement layer is used to provide organic matter and nutrients required for seedling growth and inhibit salt upwelling; S15, soil backfilling: according to the need, cover a layer of 2-3 cm fine soil on the organic improvement layer for subsequent seeding operation and to provide a contact interface for seed germination.

3. The method according to claim 2, wherein the method is characterized by: In S14, the mixing volume ratio of bean dregs, fruit shell broken material and field soil in the organic improvement layer is 1:1:2 or 1:1:

3.

4. The method of claim 1, wherein the method is characterized by: In S2, the specific implementation steps of seed treatment and space-time salt-avoiding sowing are as follows: S21, seed biological inoculation treatment: mix the selected salt-tolerant alfalfa seeds with aerogel embedded bacterial agent in a certain proportion for inoculation treatment, and through seed dressing, coating or short-term seed soaking, the beneficial microorganisms are attached to the seed surface to provide an initial biological protection barrier for seed germination and young root growth; S22, salt-avoiding sowing period decision: based on the analysis of long-term climate data and soil water and salt transport law of the planting area to determine the best "salt-avoiding window period", which is usually selected in a specific period after the surface thawing in spring, before the strong salt return, or after the continuous precipitation in autumn to make the surface salt leaching, so as to realize "time salt avoidance"; S23, ridging point sowing operation: in the determined salt-avoiding window period, use the matching agricultural machinery to perform accurate point sowing on the ridge where the root zone microenvironment has been constructed, sow the seeds treated with bacterial agent in the organic improvement layer of the seeding ditch and cover with appropriate fine soil, to realize the combination of "space salt avoidance" and "time salt avoidance".

5. The method of claim 1, wherein the method is characterized by: In S4, the specific implementation steps of water and fertilizer integration and precise management are as follows: S41, system installation and debugging: lay the shallow buried drip irrigation system, bury the drip irrigation belt at a certain depth underground near the seeding row on the ridge, and connect and debug the first hub including water pump, filter and fertilizer tank, to ensure the normal operation of the drip irrigation system; S42, water and fertilizer formula and preparation: according to the fertilizer requirement characteristics of different growth stages of alfalfa, prepare special liquid fertilizer containing appropriate proportion of nitrogen, phosphorus, potassium and necessary trace elements, and inject it into the fertilizer tank for standby use; S43, precise 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, dynamic formulation of irrigation decision to determine irrigation timing, irrigation quota and whether to combine with fertilization, and execution of decision through control system to realize precise irrigation and water and fertilizer coupling supply according to demand; S44, salt leaching control operation: in the key growth period, if there is a certain amount of natural precipitation, the irrigation amount is actively reduced to fully utilize the precipitation; if it is continuous drought, a certain amount of "salt washing irrigation" is implemented through the drip irrigation system to make the water infiltrate below the alfalfa root zone, and the excess salt in the soil is leached away to control the salt concentration in the alfalfa root layer.

6. The method of claim 5, wherein the method is characterized by: The control system performs precise irrigation according to the irrigation decision algorithm of the soil water balance model, and the calculation formula is as follows: In the formula, n represents the number of days in the decision period; i represents an index variable, representing the day in the decision cycle; E i represents the crop water requirement on day i; W i represents the root zone water storage on day i; P i represents the effective precipitation on day i; D represents the soil allowable depletion.

7. The method of claim 5, wherein the method is characterized by: In the S44, the drip irrigation system controls the water amount based on the salt washing irrigation amount algorithm, and the calculation formula is as follows: In the formula, k represents the three layers of soil in the root zone, corresponding to the salt barrier layer, the improved layer, and the topsoil layer; S k represents the measured salt content of the kth layer of soil; S t represents the salt tolerance threshold of alfalfa in the root zone; p k represents the bulk density of the kth layer of soil; h k represents the thickness of the kth layer of soil; C w represents the mineralization degree of irrigation water; m k represents the permeability coefficient of the kth layer of soil.

8. The method of claim 4, wherein the method is characterized by: The preparation steps of the aerogel embedded microbial agent used in the seed inoculation treatment in S21 and the microbial agent preparation in S31 include: first, mix and stir the saline-alkali resistant composite microbial agent and humic acid synergistic adjuvant at 25-30°C constant temperature environment 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 with the modified silicon-based aerogel carrier at high speed for 3-5 minutes, then dry at 55-58°C low temperature to a water content of ≤7%, and finally crush and screen to a particle size of 0.3-0.4 mm.

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