A seedling raising method suitable for planting salt marsh reed asparagus in saline-alkali soil

Abstract

The present application relates to the field of horticultural cultivation, and discloses a seedling raising method suitable for planting salt sedge in saline-alkali soil, which comprises the steps of performing salt water non-saturated infiltration, natural evaporation concentration and fresh water saturated leaching on the seedling raising substrate in circulation; the seedling stress representation in the sentry plug tray with a shallow filling depth is used as an objective basis for triggering leaching, and the conductivity of leaching drainage is measured to feedback and adjust the stress intensity of the subsequent cycle; by reproducing a rhythmic osmotic pressure dynamic change in the seedling root zone, the physiological flexibility and adaptability memory of the seedling are constructed, and the systematic problem of low survival rate of seedlings cultivated by traditional seedling raising methods after transplanting to real saline-alkali soil due to the inability to quickly respond to environmental fluctuations is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to a seedling raising method suitable for the cultivation of salt-alkali land reed canary grass, belonging to the technical field of horticultural cultivation. BACKGROUND

[0002] At present, in modern horticultural production, a static optimal environment supply cultivation method is generally used, that is, by accurately controlling the substrate, water and fertilizer and environmental parameters, a constant non-stress growth environment is constructed for seedlings. This method can produce seedlings with consistent morphology and rapid growth at the seedling stage. However, when these seedlings are transplanted to farmland with salt-alkali stress, their survival rate is often reduced. This is because the aforementioned cultivation method, while focusing on the construction of the external morphology of seedlings, has failed to effectively establish the internal physiological regulation mechanism to cope with dynamic changes in the external environment. For example, a Chinese invention patent with the publication number CN102884937A discloses a medium-salt-alkali land castor seedling raising and transplanting method. This method uses organic substrate plug seedling method to construct a local optimized growth environment for seedlings, in order to bypass the direct stress of salt-alkali land on seed germination and early seedling stage. However, the essence of this method still belongs to an environmental avoidance strategy. The seedlings cultivated by this method are relatively robust in morphology, but their physiological systems have not experienced dynamic osmotic pressure challenges and lack adaptive memory to cope with salt concentration fluctuations. Therefore, when these protected seedlings are transplanted to real farmland, they are still difficult to effectively cope with the dramatic changes in root zone microenvironment salinity caused by evaporation, precipitation and other factors. This is the core problem that the present application aims to solve.

[0003] In order to improve the adaptability of seedlings after transplanting, the industry has tried to introduce salt stress treatment in the later stage of seedling raising. However, the existing stress treatment methods, whether continuously applying a single concentration of salt or gradually increasing the salt concentration, still essentially make seedlings passively adapt to one or more new static stress levels, and fail to enable their physiological systems to cope with continuous environmental changes. Moreover, in large-scale production, the timing of starting and stopping stress treatment often depends on indirect physical parameters or the experience of operators, making it difficult to achieve a stable balance between ensuring exercise effect and avoiding physiological damage.

[0004] Specifically, existing technologies have the following shortcomings: 1. The static tolerance of seedlings constructed by existing cultivation methods differs fundamentally from the dynamic adaptability required by real farmland environments, leading to physiological dysfunction after seedling transplantation; 2. Existing stress training methods either rely on complex external control systems or subjective experience judgment, lacking a low-cost, repeatable, and dynamic domestication technique that combines natural physical processes with feedback from the seedling's own physiological state. Therefore, how to construct a dynamically changing stress process through a simple and controllable workflow during the horticultural seedling stage, shifting the seedling cultivation goal from simple morphological development to the simultaneous establishment of morphological and physiological dynamic adaptability, becomes the technical problem this invention aims to solve. Summary of the Invention

[0005] This invention provides a seedling cultivation method suitable for asparagus cultivation in saline-alkali land. Its main purpose is to solve the problems that existing seedling cultivation methods cannot effectively establish the physiological dynamic adaptability of seedlings, and that existing stress training methods are costly, unstable in control, and difficult to apply on a large scale.

[0006] To achieve the above objectives, the present invention provides a seedling cultivation method suitable for asparagus cultivation in saline-alkali land, the method comprising the following steps of circulating a seedling substrate containing asparagus seedlings:

[0007] Step a, the salt water soaking step, involves using a salt solution of a fixed concentration to irrigate the seedling substrate in an unsaturated manner;

[0008] Step b, the evaporation and concentration step, involves interrupting irrigation after the brine soaking step and allowing the seedling substrate to lose water through natural evaporation, thereby passively increasing the salt solution concentration in the seedling substrate.

[0009] Step c, the freshwater resuscitation step, involves saturating the seedling substrate with freshwater until leaching water is generated at the bottom of the substrate to remove accumulated salt. The freshwater resuscitation step is triggered by the appearance of stress symptoms in asparagus seedlings in sentinel trays (where the substrate filling depth is less than in other ordinary trays). The method also includes measuring the average conductivity of the leaching water generated in each cycle and adjusting the duration of the evaporation and concentration step in subsequent cycles according to a preset rule: if the measured average conductivity is higher than a target value, the duration is shortened; if it is lower than the target value, the duration is extended.

[0010] Preferably, during the evaporation concentration step, an adaptive adjustment step is further included, which comprises: determining the environmental evaporation potential according to the monitored temperature and air humidity of the seedling environment; when the environmental evaporation potential is higher than a preset evaporation threshold, covering a layer of semi-transparent and microporous film above the seedling substrate; when the environmental evaporation potential is not higher than the evaporation threshold, not applying any cover.

[0011] Preferably, the step of adjusting the duration of the evaporation concentration step in the subsequent cycle is calculated by the following formula to obtain the target duration of the subsequent cycle : , wherein, is the actual duration of the current cycle, is the average conductivity value measured in the current cycle, is a target conductivity value set according to the target soil conditions of the saline-alkali land to be transplanted, is a preset positive response coefficient.

[0012] Preferably, the step of taking the stress indication of the asparagus seedlings in the sentinel plug as the triggering basis further comprises: before the asparagus seedlings in the sentinel plug show visible wilting indication, starting the atomization system to apply salt mist to all asparagus seedlings, the duration of applying salt mist is 30 seconds to 60 seconds, and the salt mist is formed by atomizing a salt solution with a conductivity value of 1.0 dS / m to 2.0 dS / m; and taking the immediate physiological stress response of the asparagus seedlings in the sentinel plug to the salt mist as the judgment basis for triggering the execution of the fresh water recovery step.

[0013] Preferably, the immediate physiological stress response includes rapid change of asparagus seedling leaf angle, or acute water loss posture different from water deficit wilting.

[0014] Preferably, during the repeated execution of the cycle, a step of periodically replacing the seedling plug between different physical positions is further included.

[0015] Preferably, in the salt water soaking step, the conductivity value of the salt solution with a fixed concentration is 30% to 50% of the target soil conductivity value of the saline-alkali land to be transplanted.

[0016] Preferably, in the salt water soaking step, the non-saturated irrigation has an irrigation amount of 50% to 70% of the maximum water holding capacity of the seedling substrate.

[0017] Preferably, the method comprises sowing two asparagus seeds in each seedling hole, and the method is started to be executed after the asparagus seedlings grow the first stem, and is repeatedly executed for 6 to 8 cycles before transplanting and planting, and the period of each cycle is 2 to 4 days.

[0018] Compared with the prior art, the beneficial effects of the present application are:

[0019] 1. By first infiltrating the seedling substrate with unsaturated saltwater, then stopping irrigation and using the natural evaporation of water, the salt concentration in the substrate is passively and continuously increased, and then saturated fresh water irrigation is applied at a preset node; this complete cycle process reproduces a dynamic osmotic pressure environment in the root zone of the seedling substrate, and the physiological system of the seedling is adapted to this continuous and rhythmic osmotic pressure fluctuation, the internal ion balance and water regulation mechanism is repeatedly called and reset, compared with in a constant or stepwise stress environment, the dynamic adaptation ability of the seedling is constructed, and the problem of physiological damage caused by the seedling's inability to quickly respond to the dramatic changes in environmental osmotic pressure after being transplanted to the real saline-alkali soil environment is avoided.

[0020] 2. On the basis of repeatedly performing the above cycle, a part of the substrate is filled with shallow seedling hole trays, and they are treated synchronously with ordinary hole trays; because the water holding capacity of this part of the hole tray is less, the physical process of water loss and salt concentration in the substrate during the evaporation concentration stage will necessarily be faster than that of ordinary hole trays, and the seedlings in it will show stress state first; taking this stress as the basis for triggering the fresh water recovery step for all hole trays, the irrigation decision node which originally depends on indirect physical quantities or operating experience is changed into an objective signal directly given by the physiological state of the seedling itself, thereby introducing a unified and repeatable control reference for the stress training process of the whole seedling batch.

[0021] 3. In the evaporation concentration step, according to the evaporation potential of the external environment, a cover is selectively applied or not applied above the seedling hole tray; in high evaporation potential environment, the cover is applied to slow down the evaporation rate, and in low evaporation potential environment, the cover is not applied to maintain or promote evaporation; this adjustment mode makes the salt concentration rate of the substrate driven by natural evaporation be corrected to a relatively stable interval under different weather conditions, ensuring that the physiological stress process experienced by seedlings cultivated in different batches and different seasons has higher consistency, and further improving the uniformity of the final nursery seedling product in physiological characteristics.

[0022] 4. In the fresh water recovery step of each cycle, by collecting the leaching drainage produced in this step and measuring its average conductivity value, a quantitative index representing the peak stress intensity reached in the last cycle can be obtained; then according to the comparison result of this index with the target interval, the duration of the evaporation concentration step in the next cycle is adjusted; by using the output of the previous cycle to correct the control input of the next cycle, a feedback correction mechanism is established between multiple consecutive tidal cycles, so that the whole seedling domestication process can be self-optimized according to the actual physiological response of the seedling and the environmental changes. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1A closed-loop control flow diagram of the seedling raising method of the present application;

[0024] Fig. 2 A comparison chart of the effects of different initial salt solution concentrations on physiological indicators of seedlings of the present application;

[0025] Fig. 3 An intelligent implementation system architecture diagram of the seedling raising method of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below; it should be noted that the following embodiments are only used to explain the present application and do not limit the protection scope of the present application.

[0027] The disclosed seedling raising method suitable for salt-alkali land reed planting has an overall operation flow including a core processing stage that can be executed in a cycle and is configured with multiple auxiliary modules for process control of the core processing stage; the core processing stage aims to construct rhythmic osmotic pressure dynamic changes by physical action on the root zone of the seedling substrate, which is composed of a salt water soaking step a, an evaporation concentration step b and a fresh water recovery step c to form an operation cycle; the auxiliary control modules include a sentinel plug and its signal detection mechanism for determining the execution timing of step c, an adaptive adjustment mechanism for responding to external environmental changes and stabilizing the execution rate of step b, and a leaching drainage electrical conductivity monitoring mechanism for feedback correction between cycles; in a commercial reed seedling application, if the target farmland for seedling is medium salinization land, in order to cope with the situation that the seedlings cultivated by the conventional seedling raising method lack the adaptability to osmotic pressure fluctuations and have a low survival rate after transplanting, the method of the present application is configured to start executing after the reed seedlings grow the first stem, and is repeated for 6 to 8 operation cycles before transplanting, the period of each cycle is set to 2 to 4 days, and two reed seeds are sown in each seedling hole of the deep seedling tray.

[0028] The initial step of the cycle, i.e. the saltwater soaking step in step a, is to introduce the initial salt stress signal to the root zone of the seedling substrate. For this purpose, the concentration of the salt solution needs to be calibrated first, and the procedure is as follows: collect soil samples from multiple points in the target saline-alkali land for transplanting, measure the average conductivity value of the saturated leachate, and take 30% to 50% of the measured value as the target conductivity value of the salt solution. For example, if the soil conductivity value of the target saline-alkali land is 8.0 dS / m, the conductivity value of the salt solution is set to a fixed value within the interval of 2.4 dS / m to 4.0 dS / m. It should be noted that the specific selection of the initial salt solution conductivity value within the interval of 30% to 50% of the target saline-alkali land soil conductivity value is based on a pre-prepared seedling growth response test procedure. This procedure includes setting up multiple parallel test groups, using salt solutions with conductivity values corresponding to different gradients within the aforementioned interval, such as 30%, 40%, and 50%, for initial non-saturated irrigation, and after completing two complete cycles, measuring the average length of the first root stem of the asparagus seedlings in each test group and a fresh water irrigation control group, and then calculating the relative growth rate of the stem length of each test group relative to the control group. Finally, the highest salt solution conductivity value that can maintain a stem length relative growth rate of not less than 90% is taken as the operational setting value of the initial salt solution conductivity for subsequent batch seedling cultivation. During the irrigation operation, in order to allow the salt to enter the root zone and not to be leached due to oversaturation, non-saturated irrigation is used, and the irrigation amount is determined to be 50% to 70% of the maximum water holding capacity of the seedling substrate. This maximum water holding capacity can be obtained through pre-calibration experiments, i.e. taking the dry seedling substrate, weighing it, saturating it with fresh water until no water flows out, and then weighing it again. The difference between the two weights is the maximum water holding capacity. Accordingly, if the maximum water holding capacity of the substrate in a seedling tray is 1000 mL, the irrigation amount in the saltwater soaking step is controlled to be 500 mL to 700 mL.

[0029] After the saltwater soaking step, the process proceeds to step b, the evaporation concentration step. In this step, irrigation is interrupted, and the seedling substrate loses water under the conditions of ventilation and light in the greenhouse. As the water in the substrate evaporates, the salt ions dissolved in the water remain in the substrate, causing the salt concentration of the remaining aqueous solution in the substrate to passively and continuously increase, thereby forming an automatically increasing salt stress environment in the root zone. Since the rate of natural evaporation is affected by external conditions such as temperature and air humidity in the seedling environment, an adaptive adjustment mechanism is further configured in this step to stabilize the evaporation rate. The execution logic of this mechanism is as follows: monitor the data through the temperature and humidity sensors already configured in the seedling field to determine the current environmental evaporation potential. If it is a high evaporation potential day, for example, the temperature is higher than 28 and the relative humidity of the air is less than 50%, a layer of semi-transparent plastic film with micropores is covered on all the seedling trays. This film forms a local high-humidity microclimate boundary layer on the surface of the trays, which inhibits the rapid evaporation of water. If it is a low evaporation potential day, for example, the temperature is lower than 20 and the relative humidity of the air is higher than 75%, no cover is applied and the ventilation equipment in the nursery field can be activated to enhance the air flow over the substrate surface to maintain or promote evaporation.

[0030] When the evaporation concentration process reaches the stress critical point, the step c fresh water recovery step needs to be executed immediately to avoid irreversible damage to the seedlings; to obtain an objective execution trigger signal from the biological state, the method uses a sentinel plug mechanism; the construction method is to set one or more sentinel plug trays in the whole batch of nursery plug trays, and the filling depth of the nursery substrate of the sentinel plug tray is less than that of the ordinary plug tray; during the execution cycle, the sentinel plug tray is processed synchronously with the ordinary plug tray, and because the total volume of the substrate of the sentinel plug tray is smaller and the water holding capacity is less, the salt solution concentration in the substrate of the sentinel plug tray increases faster than that of the ordinary plug tray during the evaporation concentration stage of step b, and the seedlings in the sentinel plug tray will reach the stress critical point first; therefore, the execution of the fresh water recovery step is triggered by observing the appearance of the predetermined stress characteristics of the asparagus seedlings in the sentinel plug tray; under certain weather conditions, such as high humidity and no wind, the wilting characteristics of the seedlings may be delayed or not obvious, in order to deal with the signal blunting situation, an active detection method can be used, which is to start the atomization system in the nursery field when it is judged according to the time that the sentinel plug tray will enter the stress critical point but no visible wilting appears, and a salt mist with a duration of 30 to 60 seconds is applied to all asparagus seedlings, and the salt mist is formed by atomizing a salt solution with an electrical conductivity of 1.0 to 2.0 dS / m; in addition, the salt mist active detection method used when the stress characteristics of the sentinel plug tray are not obvious, the coordinated setting of the two parameters of the salt mist electrical conductivity and the application duration, is dynamically related to the air saturation water vapor pressure difference, i.e. VPD value of the nursery environment, the specific operation logic is that the VPD value is calculated by the real-time data of the temperature and humidity sensor, when the VPD value is lower than 0.8 kPa, the salt mist electrical conductivity is set to 1.8 to 2.0 dS / m and the application duration is 50 to 60 seconds, when the VPD value is in the interval of 0.8 to 1.5 kPa, the salt mist electrical conductivity is set to 1.4 to 1.6 dS / m and the application duration is 40 to 50 seconds, and when the VPD value is higher than 1.5 kPa, the salt mist electrical conductivity is set to 1.0 to 1.2 dS / m and the application duration is 30 to 40 seconds; for the sentinel seedlings that have been in a state of high stress, the additional slight stress from the aboveground part will induce a rapid and significant response, and the immediate physiological stress response, such as the rapid change of the angle of asparagus seedling leaves or an acute water loss posture different from water deficit wilting, is used as the basis for triggering the execution of the fresh water recovery step; once the trigger instruction is confirmed, sufficient fresh water is immediately used to saturate irrigation of all plug trays until leaching drainage is produced at the bottom of the nursery substrate, which on the one hand reduces the root zone osmotic pressure and supplements the water for the seedlings, and on the other hand leaches out the salt accumulated in the last cycle.

[0031] To enable the entire multi-cycle seedling raising process to be adjusted according to the actual physiological response of the seedlings, this method establishes a feedback correction mechanism between successive cycles. This mechanism utilizes the leaching wastewater generated in step c (freshwater resuscitation). The operation is as follows: in each cycle, the initially generated leaching wastewater is collected, and its average conductivity after mixing is measured and denoted as... The measured The value is related to a preset target conductivity value. In comparison, the The value can be set according to the target soil conditions of the saline-alkali land to be transplanted, for example, set to 80% of the target soil conductivity value; based on the comparison results, the target duration of the evaporation and concentration step in the subsequent cycle is calculated and adjusted using the following formula. , In the formula, This is the actual duration of this cycle. It is a positive response coefficient; this response coefficient The value of can be determined through an initial calibration cycle, that is, in the first cycle, a reference evaporation time is set, and the generated evaporation time is measured. In the second cycle, the evaporation time is extended or shortened by a fixed amount, and the resulting value is measured again. Value, through =(Change in duration) / ( By doing so, a coefficient value suitable for the current seedling environment can be obtained; if Higher than This indicates that the previous round of coercion was too strong, so the calculated... Less than This means shortening the evaporation time of the next cycle, and vice versa. In addition, in large seedling nurseries, in order to cope with the differences in evaporation rates of each seedling tray caused by uneven air flow and light distribution, the seedling trays can be periodically replaced between different physical locations during the repeated execution of the cycle. For example, every other cycle, the seedling trays in the edge area are swapped with those in the center area to equalize the evaporation conditions experienced by different seedling trays throughout the acclimatization period.

[0032] Embodiment 1: This embodiment is a specific application of the technical solution disclosed in the foregoing detailed description in a specific application scenario; in a large-scale commercialization of asparagus seedling project, its task is to supply hundreds of thousands of asparagus seedlings with high survival rate for the agricultural development project in the coastal saline-alkali area, the soil electrical conductivity value of the target farmland is determined to be 7.5 dS / m, a batch of seedlings cultivated by using the standardized seedling raising method in the early stage, although showing uniform morphology in the seedling stage, but after planting in the target farmland, a large-scale wilting occurs within two weeks, and the final survival rate is less than 10%; in response to this situation, the project uses the seedling raising method of the present application to cultivate a new batch of asparagus seedlings; after the first root of the seedling grows, the first operation cycle is started, according to the electrical conductivity value of 7.5 dS / m of the target farmland, the salt solution concentration used in the salt water soaking step of step a is set to 3.0 dS / m, and all seedling trays, including the sentry plug tray arranged therein at a ratio of 50:1, with a substrate filling depth of 80% of the ordinary plug tray, are subjected to non-saturated irrigation with a water holding capacity of 60%; subsequently, the whole seedling raising greenhouse enters the evaporation concentration step of step b, during which all irrigation operations are interrupted, the substrate gradually loses water under the action of natural evaporation, and the salt concentration in the root zone is passively increased, thereby exerting a continuously increasing osmotic stress on the seedling root system; in the process, the monitoring object of the operator is only the sentry plug tray, on the third day of the cycle, slight curling of the seedling leaves in the sentry plug tray is observed, and this stress indication is immediately used as a trigger instruction, and the operator immediately performs the fresh water recovery step of step c on all plug trays, and saturated irrigation is performed with sufficient fresh water until washing drainage flows out from the bottom of the tray.

[0033] In this operation process, the natural evaporation process of water is used to replace the external control equipment, and in the absence of additional energy consumption, a dynamically changing osmotic stress is formed in the root zone to exercise the physiological regulation ability of the seedlings; and the sentry plug tray, due to its faster water loss rate caused by its shallower substrate depth, the seedlings therein can be expected to exhibit a stress state earlier than the main population, and the irrigation decision originally dependent on indirect physical quantities or personnel experience is converted into an objective signal given by the physiological state of the seedlings, the combination of these two technical steps makes the application of stress training close to the physiological limit and within the safe range to the whole population a repeatable operation procedure; at the same time, the saturated fresh water irrigation of step c, in addition to relieving the stress and supplementing the water for the seedlings, the leaching drainage generated will also flush out the salt ions accumulated in the substrate in the last cycle, this design avoids the situation of ion toxicity caused by continuous accumulation of salt during salt stress training; after 7 operation cycles, the batch of seedlings is planted in the same saline-alkali land after four weeks of cultivation; the statistical results three weeks after planting show that the survival rate of the seedlings is more than 85%, and the plants quickly recover their growth, showing physiological adaptability to the saline-alkali environment.

[0034] Example 2: To objectively verify the effect of the seedling raising method of the present application on improving the physiological adaptability of asparagus seedlings after planting in saline-alkali land, a control test was conducted in a greenhouse with controllable environmental parameters. The temperature fluctuation in the greenhouse was controlled within ±1 , the air relative humidity fluctuation was controlled within ±5%, and a 14-hour light period was provided daily. The same batch of asparagus seeds was selected for cultivation in deep seedling trays filled with the same mixture of grass charcoal and vermiculite. The specifications and substrate filling capacity of all seedling trays were kept consistent. The test was divided into three groups: a control group, an inventive group, and a comparative group. Each group had three replicates, and each replicate contained 100 seedlings. The control group was only irrigated with fresh water during the entire seedling raising period to maintain a constant moist state of the substrate. The inventive group was operated according to the disclosed technical solution. The comparative group was subjected to continuous salt stress treatment, i.e., from the beginning of the first stem growth, a fixed-concentration salt solution with an electrical conductivity of 2.0 dS / m was used for irrigation. After four weeks of seedling raising, the seedlings from all three groups were transplanted into a pre-prepared salted substrate simulating the conditions of the target saline-alkali land, with the electrical conductivity of the salted substrate set at 7.5 dS / m. On the 14th day after transplantation, the physiological indicators of the seedlings in each group were measured and statistically analyzed to assess their adaptability to salt stress. The measured indicators included survival rate, root activity determined by the TTC method, proline content, and malondialdehyde content, which was positively correlated with the degree of lipid peroxidation damage to the cell membrane. The higher the value, the greater the stress damage to the plant. The test data are summarized in Table 1.

[0035] Table 1: Comparison of physiological indicators of seedlings from each group on the 14th day after transplantation.

[0036]

[0037] Referring to Table 1, the seedlings in the control group had the lowest survival rate of 14.3% and the weakest root activity after being directly exposed to high salt stress, with a malondialdehyde content of 28.5 nmol / g. The seedlings in the comparative group, which had experienced continuous low-concentration salt stress, had a survival rate of 41.7%, with indicators superior to those of the control group. The seedlings in the inventive group had a survival rate of 86.2% and a root activity of 1.12 mg / g·h. The proline content was the highest among the three groups, and the malondialdehyde content was the lowest. The data showed that the seedlings cultivated by the method of the present application had formed more effective osmotic regulation mechanisms and stress damage defense capabilities. The test results showed that, compared with seedlings grown in a non-stress environment or under continuous low-intensity stress, seedlings cultivated using the seedling raising method of the present application, which included salt water soaking, evaporation concentration, and fresh water recovery cycles, exhibited higher physiological adaptability and survival rate when transplanted in a high-salinity environment.

[0038] To further highlight the technical advantages of dynamic feedback and rhythm stress in the method of the present application over other active stress methods, the following comparative example is added.

[0039] Comparative Example 1: To further verify the unique advantages of dynamic rhythm stress based on the physiological state feedback of seedlings in the method of the present application in building environmental adaptability, another comparative example is set up. The test conditions of this comparative example, including asparagus seeds, seedling substrate, seedling tray specifications, greenhouse environmental parameters, total seedling time (four weeks), and the final salinized substrate conductivity value (EC) of the transplanted seedlings (EC = 0.5 dS / m), are consistent with the conditions disclosed in Example 2 at the character level. This comparative example uses a pre-programmed stepwise salt stress scheme representing the conventional approach of those skilled in the art to replace the dynamic feedback cycle of the present application, which includes salt water immersion, evaporation concentration, and fresh water recovery. The specific stress scheme is set as follows: after the first stem grows, the first week uses fresh water for regular irrigation; from the second week, the conductivity value of the irrigation salt solution is increased by one level every week, i.e. the second week uses a salt solution with a conductivity value of 0.2 dS / m, the third week uses a salt solution with a conductivity value of 0.3 dS / m, and the fourth week uses a salt solution with a conductivity value of 0.4 dS / m. At the beginning of each increase in salt solution concentration (e.g. the first day of the second and third weeks), about 5-8% of the total seedlings are observed to be acutely wilted and unable to recover, showing poor adaptation to the stepwise change in osmotic pressure. After the four-week seedling process is completed, the seedlings cultivated in this comparative example are transplanted into a salinized substrate with a conductivity value of 0.5 dS / m. On the 14th day after transplantation, the same physiological indicators of the seedlings are measured and statistically analyzed, and the test data are summarized in Table 2 below.

[0040] Table 2: Comparison of physiological indicators of seedlings treated by different seedling methods on the 14th day after transplantation.

[0041]

[0042] Referring to Table 2, compared with the control group, the survival rate (38.5%) and various physiological indicators of the comparative example 1 group using the stepwise salt stress scheme are improved to some extent. However, compared with the test group using the method of the present application, the survival rate, root activity and proline content are significantly lower, while the malondialdehyde content, which represents the degree of cell membrane damage, is higher. The test results show that the pre-programmed stepwise salt stress scheme can induce a certain static salt tolerance in seedlings, but due to the lack of real-time response and dynamic adjustment to the actual physiological state of the seedlings, the physiological adaptability and final survival rate of the seedlings cultivated by this method are inferior to those of the seedlings cultivated by the dynamic rhythm stress method based on the sentinel mechanism and feedback correction of the present application. ​​​​​

[0043] Example 3: This example combines Figs. 1 to 3 This describes a seedling cultivation method suitable for asparagus cultivation in saline-alkali land, such as... Fig. 1 As shown, this process focuses on the seedling substrate and root zone environment B1 as the core treatment objects, and executes a closed-loop control process in cycles. One cycle begins with the substrate being unsaturated with saline solution to wet the substrate, followed by an evaporation and concentration process. During this stage, the moisture in the substrate decreases due to natural evaporation, and the salt is passively concentrated. The rate of this process is affected by the evaporation potential of the seedling environment, which is determined by factors such as temperature and humidity. At the same time, the physiological state of the seedlings is continuously observed through a stress monitoring module. When a preset stress manifestation trigger signal is detected, the control system or operator issues a recovery command to initiate a freshwater recovery treatment, i.e., rinsing the substrate with saturated freshwater. The rinsing wastewater generated by this treatment is collected, and its average conductivity is measured. This data is input into the feedback adjustment calculation module to generate adjustment instructions for the duration of the evaporation and concentration step in the next cycle.

[0044] like Fig. 2 As shown, the horizontal axis represents four initial salt solutions with different electrical conductivity values, corresponding to 20% (1.6 dS / m), 30% (2.4 dS / m), 50% (4.0 dS / m), and 70% (5.6 dS / m) of the target saline-alkali soil electrical conductivity, respectively. The left vertical axis represents the relative value of root activity in asparagus seedlings, and the right vertical axis represents the relative value of malondialdehyde (MDA) content. The data in the figure show that as the salt solution concentration increases, root activity (represented by solid filled columns) shows a decreasing trend, while MDA content, as an indicator of stress damage (represented by dotted filled columns), shows an increasing trend. In particular, at a concentration of 70% (5.6 dS / m), MDA content increases sharply. This result provides experimental basis for optimizing the initial salt solution concentration within the range of 30% to 50% of the target soil electrical conductivity.

[0045] like Fig. 3 As shown, the system consists of a central control and monitoring station and an intelligent seedling greenhouse. The central control and monitoring station contains a data analysis and decision-making module, responsible for sending control commands and receiving and analyzing monitoring data. The intelligent seedling greenhouse is divided into three functional units: a water and fertilizer integration center, including a freshwater storage tank and a brine solution mixing tank, responsible for accurately supplying freshwater or brine solution according to irrigation commands; and a seedling area, which is equipped with ordinary seedling trays and shallowly filled seedling trays, and is equipped with a device for collecting leaching wastewater and measuring conductivity using a conductivity meter. The device for data, environment perception and execution system, which perceives the environment state through temperature and humidity sensor and executes the environment control instruction by using air circulation fan, atomization system and covering film, etc. The whole system realizes the automatic control of the seedling process by the closed loop flow of data and instruction, and feeds back the stress characterization observation signal, conductivity , data, etc. to the central control station.

[0046] Embodiment 4: This embodiment discloses a standardized engineering calibration procedure for determining the key control parameters in the method of the present application, in order to cope with different production environments and substrate conditions; when a commercial seedling raising institution applies the method for the first time, in order to face a target plot with a soil conductivity value of 8.0 dS / m, in order to ensure the controllability of the seedling raising process, two core parameters need to be calibrated in advance: the initial concentration of the salt solution used in step a, and the response coefficient used to feedback and adjust the duration of step b ; in order to determine the operation interval of the initial salt solution concentration, four groups of tests are set, denoted as A1, A2, A3 and A4, and each group uses 100 healthy asparagus seedlings with consistent state; all other seedling raising conditions are kept consistent except the salt solution concentration; the four groups of tests use salt solutions with conductivity values of 1.6 dS / m, 2.4 dS / m, 4.0 dS / m and 5.6 dS / m respectively for the unsaturated irrigation of step a, and the four concentration values correspond to 20%, 30%, 50% and 70% of the target saline soil conductivity value respectively; after completing an operation cycle lasting for three days, the root activity and malondialdehyde content of each group of seedlings are measured; the measurement results show that the physiological indicators of the seedlings in group A1 have no significant difference compared with the untreated seedlings; the root activity of the seedlings in groups A2 and A3 has a small decrease, but the malondialdehyde content has no significant increase; the root activity of the seedlings in group A4 has a large decrease, and the malondialdehyde content increases, showing the characterization of acute stress damage; the results of this calibration test provide operation basis for setting the conductivity value of the initial salt solution in the interval of 30% to 50% of the target soil conductivity value in subsequent production.

[0047] After the concentration of the initial salt solution is determined (in this example, 3.2 dS / m, i.e. 40%), the calibration of the response coefficient is continued; this process uses two consecutive operation cycles, and a target conductivity value of 6.4 dS / m is set; in the first calibration cycle, a reference evaporation concentration step duration of 60 hours is set, and at the end of this cycle, the average conductivity value of the leaching drainage is measured as 7.2 dS / m; in the second calibration cycle, the duration of the evaporation concentration step is shortened to 54 hours, and at the end of this cycle, the measured average conductivity value decreased to 6.6 dS / m; accordingly, the response coefficient may be calculated from the relationship ( ) / ( ) and substituting the measured values, i.e. = (60h - 54h) / (7.2 dS / m - 6.6 dS / m) = 6h / 0.6 dS / m = 10h / (dS / m); through this calibration procedure, the initial operating parameters applicable to the current specific production environment conditions are obtained, i.e. the initial salt solution conductivity value of 3.2 dS / m and the feedback regulation response coefficient value of 10h / (dS / m); this procedure transforms the general technical method into a set of operating instructions with explicit operating parameters, which can be directly applied to production, making the control process of the seedling raising method portable and reproducible.

[0048] Example 5: This example is intended to illustrate the execution of the method of the present application under sustained adverse weather conditions; during the execution of a seedling raising project, the greenhouse environment is subjected to a week of continuous rainy weather, characterized by temperatures consistently below 20 °C and air relative humidity consistently above 80%, this low evaporation potential working condition reduces the rate of step b which relies on natural evaporation; under this environmental condition, after the start of an operating cycle, although the seedling plug trays have not been covered as required by the self-adaptive regulation mechanism, after 48 hours of execution of the evaporation concentration step, the weight loss rate of the substrate is lower than that under normal weather conditions, from which it is judged that, without taking measures, the duration of this cycle will exceed the pre-set upper limit of 4 days and the salt concentration in the substrate can not reach the required stress threshold; to deal with this situation, the operator starts the air circulation fans inside the greenhouse to increase the air flow rate on the surface of the substrate of the seedling plug trays, at the same time, combined with the periodic plug tray position replacement procedure, the plug trays originally located in the center of the greenhouse, where the air flow is weak, are swapped with the plug trays located near the fans, where the air flow is strong, this operation is performed once a day.

[0049] Through the above measures, the overall water loss rate of the substrate is improved, on the fourth day of the cycle, the seedlings in the sentinel plug trays exhibit the pre-set stress characteristics, triggering the execution of the step c fresh water recovery step; subsequent conductivity measurements of the leachate drainage generated by this cycle are within the target conductivity value interval; this process shows that the method of the present application, by combining its operating flow with the existing environmental control equipment in seedling production, and by periodically replacing the positions of the plug trays, can cope with sustained adverse weather conditions and maintain the normal progress of its operating cycle within a wide range of environmental fluctuations.

[0050] Example 6: This example discloses a standardization pre-calibration procedure for adapting the sentinel plug parameters and stress characterization criteria in the method of the invention when changing the seedling substrate; when a seedling production unit plans to adopt a new seedling substrate with coconut coir as the main component, since the water holding and water conducting properties of this substrate are different from that of peat, the following calibration procedure needs to be performed to determine the operating parameters of the sentinel plug and to unify the stress characterization criteria; to determine the sentinel plug filling depth suitable for coconut coir substrate, multiple sets of test plugs are set up, one set is a normal plug with a substrate filling depth of 20 cm, and four sets of potential sentinel plugs are set up with substrate filling depths of 90%, 80%, 70% and 60% of the normal plug respectively; all plugs are synchronized to perform one cycle of operation, and during the evaporation concentration period in step b, the leaf water potential of each group of seedlings is monitored at regular intervals using a plant water potential meter; the time when the leaf water potential of the seedlings in the sentinel plug of each depth reaches the critical stress threshold (-1.5 MPa) is recorded, and compared with the time when the leaf water potential of the seedlings in the normal plug reaches the threshold; the test results show that the time when the leaf water potential of the seedlings in the plug with a filling depth of 70% reaches the critical point is about 18 hours earlier than that of the normal plug, accordingly, 70% is determined as the operating filling depth of the sentinel plug for this kind of coconut coir substrate to obtain a warning window of 12 to 24 hours.

[0051] Secondly, to quantify the immediate physiological stress response induced by salt spray and reduce the subjectivity of manual observation, a salt spray application operation is performed on the seedlings in the sentinel plug with a filling depth of 70% that have reached the critical stress threshold in the above test; when the salt spray is applied, a high-resolution camera is used to take time-lapse photos of the morphological changes of the seedlings, and the change in the angle between the main stem and the main leaf of the asparagus seedlings is quantified through image analysis; the analysis results show that within 3 minutes after the salt spray is applied, the average angle reduction between the main stem and the main leaf of the seedlings in the critical stress state is greater than 15 degrees, while the angle change of the seedlings that have not reached the critical stress state is less than 5 degrees; accordingly, a quantifiable judgment criterion is established, i.e. the average angle change of the main leaf of the seedlings in the sentinel plug is greater than 15 degrees within 3 minutes after the salt spray is applied as the basis for triggering the step c fresh water recovery step, and the images of this process are made into standard operation guide cards for operator training; by performing this set of standardized pre-calibration procedure, the method of the invention can be applied to seedling substrates with different physical properties, and the judgment basis for the key steps is converted from qualitative observation to quantifiable engineering indicators, thereby ensuring the stability and consistency of the seedling process under different production conditions.

[0052] It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention.

[0053] Finally, it should be noted that the above examples are merely intended to illustrate the technical solutions of the present application and not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A seedling cultivation method suitable for asparagus cultivation in saline-alkali land, characterized in that, The method includes performing the following steps on a seedling substrate containing asparagus seedlings: Step a, the salt water soaking step, involves using a salt solution of a fixed concentration to irrigate the seedling substrate in an unsaturated manner; Step b, the evaporation and concentration step, involves interrupting irrigation after the brine soaking step and allowing the seedling substrate to lose water through natural evaporation, thereby passively increasing the salt solution concentration in the seedling substrate. Step c, the freshwater resuscitation step, involves saturating the seedling substrate with freshwater until leaching water is generated at the bottom of the substrate to remove accumulated salt. The freshwater resuscitation step is triggered by the appearance of stress symptoms in asparagus seedlings in sentinel trays (where the substrate filling depth is less than in other ordinary trays). The method also includes measuring the average conductivity of the leaching water generated in each cycle and adjusting the duration of the evaporation and concentration step in subsequent cycles according to a preset rule: if the measured average conductivity is higher than a target value, the duration is shortened; if it is lower than the target value, the duration is extended.

2. The seedling raising method for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, During the evaporation and concentration step, an adaptive adjustment step is also included, which includes: determining the environmental evaporation potential based on the monitored temperature and air humidity of the seedling environment; when the environmental evaporation potential is higher than a preset evaporation threshold, covering the seedling substrate with a translucent and microporous film; and when the environmental evaporation potential is not higher than the evaporation threshold, not applying any covering.

3. The seedling raising method for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, The step of adjusting the duration of the evaporation and concentration step in subsequent cycles is specifically calculated using the following formula to determine the target duration of the subsequent cycles. ,in, This is the actual duration of this cycle. This is the average conductivity value measured in this cycle. This is a target electrical conductivity value set based on the soil conditions of the target saline-alkali land for transplantation. This is a preset positive response coefficient.

4. The seedling raising method for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, The step of using the appearance of stress symptoms in asparagus seedlings in sentinel trays as the triggering criterion further includes: before the asparagus seedlings in the sentinel trays show visible wilting symptoms, activating the atomization system to apply salt spray to all asparagus seedlings for 30 to 60 seconds, the salt spray being formed by atomizing a salt solution with a conductivity of 1.0 dS / m to 2.0 dS / m; and using the immediate physiological stress response of the asparagus seedlings in the sentinel trays to the salt spray as the criterion for triggering the freshwater resuscitation step.

5. A seedling raising method suitable for asparagus cultivation in saline-alkali land according to claim 4, characterized in that, Immediate physiological stress responses include rapid changes in the leaf angle of asparagus seedlings, or acute dehydration postures that are distinct from wilting due to water shortage.

6. The seedling raising method for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, The process of repeatedly executing the loop also includes the step of periodically replacing the seedling trays in different physical locations.

7. A seedling raising method suitable for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, In the salt water soaking step, the conductivity value of the salt solution of a fixed concentration is 30% to 50% of the conductivity value of the target transplanted saline-alkali soil.

8. A seedling raising method suitable for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, The unsaturated irrigation in the salt water soaking step is 50% to 70% of the maximum water holding capacity of the seedling substrate.

9. A seedling raising method suitable for asparagus cultivation in saline-alkali land according to claim 1, characterized in that, The method involves sowing two asparagus seeds in each seedling hole, starting the cycle after the asparagus seedlings have grown their first stem, and repeating the cycle 6 to 8 times before transplanting. Each cycle lasts 2 to 4 days.

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