A method for judging soil conditions and precise irrigation of a puer tea field in a puer tea area and application thereof

Abstract

This invention relates to a method for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco region and its application. The method includes: (1) combining tobacco plant morphological diagnosis with soil moisture quantitative monitoring to judge the soil moisture status in the tobacco field; (2) classifying the degree of water shortage according to the soil moisture status in the tobacco field and the growth and development stage of the tobacco plants, and performing precise irrigation on the tobacco plants; in step (1), the morphological diagnosis is based on the dynamic recovery of wilting tobacco leaves and the tactile sensation of the leaves, and the soil moisture quantitative monitoring method is: setting up soil moisture sensors according to the root distribution depth and tobacco plant planting density at different growth stages. This invention combines tobacco plant morphological diagnosis with soil moisture quantitative monitoring, establishes collaborative decision-making rules, realizes the organic integration of morphological indicators and sensor data, and overcomes the defects of strong subjectivity or obvious lag in single judgment methods.

Description

Technical Field

[0001] This invention belongs to the field of tobacco cultivation technology, and relates to a method for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco region, and its application. Background Technology

[0002] The Pu'er tobacco region is located in southwestern Yunnan Province. Its terrain is mainly mountainous and hilly with a large elevation difference. The climate is a subtropical plateau monsoon climate with distinct dry and wet seasons. The tobacco transplanting period (February to April) coincides with the end of the dry season, with scarce rainfall. Although the peak growing season (June to July) is the rainy season, the rainfall is unevenly distributed in time and space, with frequent alternations of regional droughts and short-term heavy rainfalls, resulting in complex and variable water conditions in the tobacco fields.

[0003] Currently, water management in tobacco fields in the Pu'er tobacco-growing area relies heavily on the traditional experience of tobacco farmers for soil moisture assessment and irrigation decisions. Farmers typically determine irrigation timing and volume by visually observing the degree of wilting in tobacco leaves, by touching the soil to judge its moisture level, or by relying on years of planting experience. This experience-based management method has the following shortcomings: First, the judgment criteria are highly subjective, with significant differences in judgment among different farmers, making it difficult to standardize operations; second, morphological diagnosis is delayed, as wilting often indicates that the tobacco plant is already under water stress, missing the optimal irrigation time; and third, there is a lack of a systematic moisture management plan covering the entire growth cycle, making it difficult to implement differentiated and precise irrigation based on the water requirements of tobacco at different growth stages.

[0004] While existing technologies have reported the use of soil moisture sensors for tobacco field moisture monitoring, most are limited to single-depth monitoring and cannot cover the dynamic changes in root distribution depth at different growth stages of tobacco. Furthermore, current methods for combining morphological diagnosis and quantitative monitoring are relatively simplistic, either treating them as independent criteria or merely as simple mutual verification, failing to form an organically integrated hierarchical decision-making system. In addition, considering the unique topographical and climatic conditions and production realities of the Pu'er tobacco region, a standardized soil moisture management and precision irrigation scheme that integrates morphological diagnosis and quantitative indicators and covers the entire tobacco growth period has not yet been developed.

[0005] Therefore, how to establish a set of methods for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco area, and to achieve differentiated and precise water management at different growth stages, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco area, and its application.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for judging soil moisture in tobacco fields and for precise irrigation in the Pu'er tobacco-growing area, the method comprising: (1) Combine tobacco plant morphology diagnosis with soil moisture quantitative monitoring to determine the soil moisture status in tobacco fields; (2) Classify the degree of water shortage according to the soil moisture status in the tobacco field and the growth and development stage of the tobacco plants, and carry out precise irrigation for the tobacco plants. In step (1), the morphological diagnosis is based on the dynamic recovery of wilting tobacco leaves and the feel of the leaves. The method of quantitative monitoring of soil moisture is to deploy soil moisture sensors according to the root distribution depth and tobacco plant planting density at different growth stages.

[0008] This invention creatively designs a method for judging soil moisture in tobacco fields and for precise irrigation. It combines tobacco plant morphological diagnosis with quantitative monitoring of soil moisture, establishing collaborative decision-making rules to organically integrate morphological indicators and sensor data, overcoming the shortcomings of single-method judgments that are either highly subjective or have significant time lags. Simultaneously, this invention deploys soil moisture sensors according to the root distribution depth at different growth stages of tobacco plants, forming a precise irrigation system "by growth stage, by soil layer, and by grade." This method can significantly improve water use efficiency, avoid indiscriminate irrigation, promote root development and normal growth of tobacco plants, increase tobacco yield and quality, and is highly operable, making it suitable for widespread application in Pu'er and similar ecological tobacco-growing areas.

[0009] Preferably, the method for classifying the degree of water shortage in step (2) is as follows: the degree of water shortage is divided into four levels: normal, mild water shortage, moderate water shortage, and severe water shortage, wherein: When the soil moisture sensor reading is not lower than the lower limit of the soil moisture content threshold for this growth period, and there is no wilting in the morphological diagnosis, it is considered normal and irrigation is not started. When the soil moisture sensor reading is lower than the lower limit of the soil moisture content threshold for this growth period, and the morphological diagnosis shows that the leaves wilt slightly at noon and recover in the evening, it is judged as mild water shortage, irrigation is not started, and only a warning signal is issued; When the soil moisture sensor reading is below the lower limit of the soil moisture content threshold for this growth period, and the morphological diagnosis shows that the leaves wilt during the day, cannot recover in the evening but recover at night, it is determined to be a moderate water shortage, and irrigation is initiated. When the soil moisture sensor reading is below the lower limit of the soil moisture content threshold for that growth period, and the morphological diagnosis shows that the leaves still do not recover by the next morning, it is determined to be a severe water shortage, and irrigation is initiated. During the ripening period, if the leaf touch temperature is 30-45℃ (e.g., 30℃, 35℃, 40℃, 45℃, etc.) on a sunny morning between 9 and 10 am, and the ground is dry, and the soil moisture sensor reading is below the lower limit of the ripening period threshold, it is directly determined to be a severe water shortage, and irrigation is initiated.

[0010] Preferably, the soil moisture content thresholds at different growth stages of tobacco plants are as follows: During the root establishment stage, the relative soil moisture content is 65-75% of the field capacity (e.g., 65%, 67%, 69%, 71%, 73%, 75%, etc.); during the seedling stage, the relative soil moisture content is 65-75% of the field capacity (e.g., 65%, 67%, 69%, 71%, 73%, 75%, etc.); and during the root extension stage, the relative soil moisture content is 50-60% of the field capacity (e.g., 52%, 54%, 55%, etc.). During the vigorous growth stage, the relative soil moisture content is 72-80% of the field capacity (e.g., 72%, 74%, 76%, 78%, 80%). During the topping and rounding stage, the relative soil moisture content is 60-70% of the field capacity (e.g., 60%, 62%, 64%, 66%, 68%, 70%). During the maturity stage, the relative soil moisture content is 60-70% of the field capacity (e.g., 60%, 62%, 64%, 66%, 68%, 70%).

[0011] Preferably, the soil layer setting for the quantitative monitoring of soil moisture in step (1) includes: setting one monitoring point for every 20-50 tobacco plants (e.g., 20, 25, 30, 35, 40, 45, 50 plants, etc.), with the spacing between adjacent monitoring points along the ridge direction being 2-4 (e.g., 2, 3, 4, etc.) tobacco plant row spacing; at each monitoring point, a shallow sensor is set at a soil depth of 10-15cm (e.g., 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, etc.), and a deep sensor is set at a soil depth of 25-35cm (e.g., 25 cm, 27 cm, 29 cm, 31 cm, 33 cm, 35 cm, etc.), and the horizontal distance between the shallow sensor and the deep sensor is not less than 20 cm.

[0012] Preferably, in step (2), the irrigation method includes: hole irrigation during the root establishment period, plant irrigation during the seedling establishment period, drip irrigation and / or micro-sprinkler irrigation during the vigorous growth period, plant irrigation during the dome stage, and plant irrigation during the maturity stage.

[0013] Preferably, the specific timing for irrigation of tobacco plants at each growth and development stage is as follows: irrigation during the root establishment stage is done at transplanting; irrigation during the seedling establishment stage is done within 2-3 days after transplanting (e.g., 2 or 3 days); irrigation during the vigorous growth stage is done when water is scarce; irrigation during the dome formation stage is done 2-3 days before topping (e.g., 2 or 3 days) or after topping; and irrigation during the maturity stage is done when water is scarce.

[0014] Preferably, during the vigorous irrigation period, an intermittent moisture-conserving irrigation method is adopted, which is as follows: the standard irrigation volume is divided into 2-3 times (for example, 2 times, 3 times, etc.); the irrigation volume each time is 40%-60% of the standard volume (for example, 40%, 50%, 60%, etc.), and the irrigation is carried out at intervals of 2-3 days (for example, 2 days, 3 days, etc.) until the soil moisture reaches the target range.

[0015] All other specific point values ​​not listed above within the numerical ranges mentioned above can be selected and are all within the protection scope of this invention. For the sake of brevity, they will not be described in detail here.

[0016] Preferably, the standard irrigation amount is the amount of water required in a single irrigation to bring the soil moisture content to the target threshold for the corresponding growth stage.

[0017] Preferably, the method further includes setting up a drainage system in the tobacco field, the drainage system being set up in the waist ditch and / or field ditch.

[0018] Secondly, the present invention provides the application of the method described in the first aspect in the irrigation of tobacco fields.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention creatively designs a method for judging soil moisture in tobacco fields and for precise irrigation. It combines tobacco plant morphological diagnosis with quantitative monitoring of soil moisture, establishing collaborative decision-making rules to organically integrate morphological indicators and sensor data, overcoming the shortcomings of single-method judgments that are either highly subjective or have significant time lags. Simultaneously, this invention deploys soil moisture sensors according to the root distribution depth at different growth stages of tobacco plants, forming a precise irrigation system "by growth stage, by soil layer, and by grade." This method can significantly improve water use efficiency, avoid indiscriminate irrigation, promote root development and normal growth of tobacco plants, increase tobacco yield and quality, and is highly operable, making it suitable for widespread application in Pu'er and similar ecological tobacco-growing areas. Detailed Implementation

[0020] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.

[0021] The following examples were all conducted in a tobacco field in Pu'er City, Yunnan Province. The flue-cured tobacco variety was Yunyan 87, and the cultivation method was plastic film mulching. The planting density was 120 cm between rows and 50 cm between plants, with approximately 1100 plants per mu (approximately 667 square meters). The transplanting time was from late March to early April.

[0022] Example 1 This embodiment provides a method for judging soil moisture in tobacco fields and for precise irrigation in the Pu'er tobacco-growing area. The specific implementation method is as follows: First, a soil moisture sensor monitoring network was deployed in the field: one monitoring point was set up for every 30 tobacco plants, with adjacent monitoring points spaced 4 tobacco plant rows apart along the ridge direction. At each monitoring point, a shallow sensor was placed at a soil depth of 15 cm, and a deep sensor was placed at a soil depth of 30 cm. The horizontal distance between the shallow and deep sensors was 20 cm to eliminate interference from moisture seeping down the sensor casing and affecting the deep readings.

[0023] The sensor employs a soil moisture sensor based on the frequency domain reflectance (FDR) principle, with a measurement accuracy of ±3% and a resolution of 0.1%. Data is uploaded to a cloud platform in real time via a wireless communication module. During the experiment, the sensor collected data every 30 minutes, monitoring the dynamic changes in volumetric water content of each soil layer around the clock.

[0024] The field maximum water holding capacity (Volumetric method) of the 0-30 cm soil layer in this experimental field was determined using the ring sampler method (NY / T 1121.22-2010) and found to be 27.5%, which was used as the benchmark for converting between volumetric water content and relative soil moisture content. The conversion relationships between relative soil moisture content, soil volumetric water content, and field maximum water holding capacity are as follows: Relative soil moisture content = (Volume water content of soil layer / Field capacity) × 100% The following methods are used for field management of tobacco fields: (1) Water management during the rooting period: On the day of transplanting tobacco seedlings, water the seedlings by irrigating holes, irrigating each hole with 1.5 kg of water to make the soil compact and ensure that the roots of the tobacco seedlings are in close contact with the soil; after irrigating the holes, cover them with dry fine soil in time to reduce water evaporation.

[0025] The water decision rule is as follows: during the root establishment period, the volumetric water content of the 15 cm soil layer is monitored by shallow sensors and controlled at 18% (corresponding to a relative soil water content of 65%).

[0026] (2) Water management during the seedling stage: 2-3 days after transplanting the tobacco seedlings, water the seedlings according to the soil moisture. Use the plant irrigation method, irrigate each plant with 1.5 kg of water to make the relative soil moisture content reach 65%.

[0027] The water determination rules are as follows: when the shallow sensor reading is ≥18% (relative water content ≥65%) and the leaves are not wilted, it is considered normal; when the reading is <18% and the leaves wilt slightly at noon but recover in the evening, it is considered slightly water-deficient, and only a warning is issued without irrigation; when the reading is <18% and the leaves wilt but do not recover in the evening but recover at night, it is considered moderately water-deficient, and 1.0 kg of water is added per plant; when the reading is <18% and the leaves still do not recover by the next morning, it is considered severely water-deficient, and 1.5 kg of water is added per plant.

[0028] (3) Water management during the root extension period: The core management goal during the root extension period (7-35 days after transplanting) is to control water and encourage seedling growth. During this period, the relative soil moisture content should be maintained at 55% of the field capacity.

[0029] The water determination rules are as follows: when the shallow sensor reading is ≥15.1% and the leaves are not wilted, it is considered normal; when the reading is <15.1% and the leaves wilt slightly at noon but recover in the evening, it is considered slightly water-deficient, and only a warning is issued without irrigation; when the reading is <15.1% and the leaves do not recover in the evening but recover at night, it is considered moderately water-deficient, and 1.0 kg of water is added per plant; when the reading is <15.1% and the leaves still do not recover by the next morning, it is considered severely water-deficient, and 1.5 kg of water is added per plant.

[0030] (4) Water management during the vigorous growth period: During the vigorous growth period (35-65 days after transplanting), the soil relative water content is maintained at 72% of the field maximum water holding capacity, with deep sensors as the main monitoring basis.

[0031] The water shortage decision rules are as follows: when the deep sensor reading is ≥20% (relative water content ≥72%) and the leaves are not wilted, it is considered normal; when the reading is <20% and the leaves wilt slightly at noon but recover in the evening, it is considered mild water shortage, and only a warning is issued without irrigation; when the reading is <20% and the leaves wilt during the day and cannot recover in the evening but recover at night, it is considered moderate water shortage, and drip irrigation is started; when the reading is <20% and still does not recover by the next morning, it is considered severe water shortage, and drip irrigation is started.

[0032] Each time irrigation is needed, the required amount of water for a single irrigation (3 m³ of water per acre of tobacco field) should be recorded. 3 The irrigation is done in two stages, with each irrigation using 50% of the amount needed for a single irrigation, and two days between the two irrigations.

[0033] (5) Water management during the dome stage and maturity stage: After topping, the plant enters the dome stage and maturity stage (about 65-120 days after transplanting); during this stage, water control is the main focus, and the relative soil moisture content is maintained at 60%.

[0034] The water determination rule is as follows: if the leaf touch temperature is ≥30℃ (detected using an infrared thermometer) between 9:00 and 10:00 am on a sunny day and the ground is dry, and the deep sensor reading is below 16.5% (i.e., the relative soil moisture content is below 60%), then it is determined to be severely water-deficient, and irrigation is initiated; each plant is irrigated with 0.8 kg of water.

[0035] Drainage management for tobacco fields: Keep the drainage system of tobacco fields unobstructed throughout the growing season. When preparing the soil, dig waist ditches and side ditches, with waist ditches 40 cm deep and 40 cm wide, to ensure that waterlogging can be quickly drained from the fields during the rainy season and prevent waterlogging damage.

[0036] Example 2 This embodiment provides a method for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco region. The only difference between this method and Embodiment 1 is that the water decision-making rules are changed at various stages of field management in the tobacco field, as follows: (1) Rooting water and seedling water: During the seedling stage, the root system of tobacco seedlings has not yet recovered, and the leaves are prone to temporary wilting. Once wilting is observed, watering should be started.

[0037] (2) Water management during the root extension period: Observe whether the tobacco leaves are wilted. If the leaves are not wilted, do not start irrigation; if the leaves are wilted (including slight wilting at noon and recovery in the evening), start irrigation, using the plant irrigation method, and irrigate each plant with 1.0 kg of water.

[0038] (3) Water management during the vigorous growth period: If the leaves do not wilt, do not irrigate; if the leaves wilt (including mild wilting during the day and recovery in the evening), start irrigation using drip irrigation, distributing the required amount of water per irrigation cycle (3 m³ per mu of tobacco field). 3 The irrigation is done in two stages, with each irrigation using 50% of the amount needed for a single irrigation, and two days between the two irrigations.

[0039] (4) Water management during the dome stage: If the leaves do not wilt, do not irrigate; if the leaves wilt (including mild wilting), start irrigation and use the plant irrigation method, irrigating each plant with 0.8 kg of water.

[0040] (5) Water management during maturity: If the leaves feel ≥30℃ (using an infrared thermometer) and the ground is dry between 9:00 and 10:00 am on a sunny day, and wilting occurs, it is determined to be water shortage, and irrigation should be started, with 0.8 kg of water per plant; if there is no wilting, irrigation should not be started even if the leaves feel warm.

[0041] Example 3 This embodiment provides a method for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco-growing area. The only difference between this method and Embodiment 1 is that, during the vigorous growth period of the tobacco field, the water management method is changed as follows: During the vigorous growth period (35-65 days after transplanting), the soil relative moisture content is maintained at 72% of the field maximum water holding capacity, mainly based on deep sensors.

[0042] The water determination rules are as follows: when the deep sensor reading is ≥20% (relative water content ≥72%) and the leaves are not wilted, it is considered normal; when the reading is <20% and the leaves wilt slightly at noon but recover in the evening, it is considered slightly water-deficient, and only a warning is issued without irrigation; when the reading is <20% and the leaves wilt during the day and cannot recover in the evening but recover at night, it is considered moderately water-deficient, and drip irrigation is initiated; when the reading is <20% and still does not recover by the next morning, it is considered severely water-deficient, and irrigation is initiated; drip irrigation is used, and the required amount of water is applied at once each time irrigation is needed.

[0043] Comparative Example 1 This comparative example provides a method for judging soil moisture in tobacco fields and for precise irrigation in the Pu'er tobacco-growing area. The only difference between this method and Example 1 is that the soil moisture sensor is deployed in a single-layer shallow layer, with only a 15 cm depth sensor and no 30 cm depth sensor. The volumetric water content of all soil layers is obtained by observing the readings of the shallow sensor, while all other conditions remain unchanged.

[0044] Comparative Example 2 This comparative example provides a method for judging soil moisture in tobacco fields and for precise irrigation in the Pu'er tobacco-growing area. The only difference between this method and Example 1 is that the soil moisture sensor is deployed in a single shallow layer, with deep sensors only deployed at a depth of 30 cm and no shallow sensors at a depth of 15 cm. The volumetric water content of all soil layers is obtained by observing the readings of the deep sensors, while all other conditions remain unchanged.

[0045] Comparative Example 3 This comparative example provides a method for judging soil moisture and precise irrigation in tobacco fields in the Pu'er tobacco-growing area. The only difference between this method and Example 1 is that no soil moisture sensor is set up, and the soil moisture judgment throughout the entire growth period is based solely on morphological diagnosis and the traditional experience of tobacco farmers. All other conditions remain unchanged.

[0046] The specific judgment rules are as follows: Morphological diagnosis: Observe the wilting and recovery dynamics of tobacco leaves. If the leaves wilt slightly at noon and recover to normal by evening, it is considered a temporary physiological water shortage, and irrigation is not necessary. If the wilting is severe and the leaves do not recover by evening, it is considered a severe water shortage, and irrigation is required immediately. During the ripening period, the temperature can be sensed by touching the leaves. If the leaves feel warm to the touch and the ground is dry, it is considered a water shortage, and irrigation should be initiated.

[0047] Visual assessment of soil moisture: Grab a handful of soil about 10 cm from the base of the tobacco plant. If the soil can be formed into a clump and then crumbles when dropped, the soil moisture is suitable. If the soil cannot be formed into a clump, irrigation is needed.

[0048] Test Example 1 To verify the technical effectiveness of the tobacco field soil moisture assessment and precision irrigation methods described in the embodiments and comparative examples of this invention, a field comparison experiment was conducted in the same representative tobacco field in Pu'er City, Yunnan Province. The experiment included six treatment groups: Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Each treatment was replicated three times, resulting in a total of 18 plots, each 100 m² in size. 2 The data were arranged in randomized blocks. Each treatment was strictly managed in accordance with the methods in the corresponding examples or comparative examples, and all other agricultural operations (fertilization, cultivation, plant protection, etc.) were kept consistent.

[0049] The test metrics for this test case are as follows: (1) Plant height (cm): During the dome stage (10 days after topping), select 5 representative tobacco plants from each plot, measure from the ground to the top, and take the average value.

[0050] (2) Number of effective leaves: Before harvesting, select 5 representative tobacco plants from each plot, count the number of harvestable leaves (leaf length ≥ 30 cm), and take the average value.

[0051] (3) Number of irrigations during the entire growth period: The total number of irrigations for each plot from transplanting to the end of harvest is counted. The average number of irrigations for plots with the same treatment is taken.

[0052] (4) Yield (kg / mu): The tobacco leaves in each plot were harvested in batches after maturity, and weighed after uniform curing. The yield per mu was calculated, and the average yield of the same treatment group plots was taken.

[0053] (5) Proportion of superior tobacco (%): The flue-cured tobacco leaves are graded by qualified personnel according to the GB 2635-92 standard. The weight of each grade is weighed and the percentage of superior tobacco weight in the total weight is calculated. The average proportion of superior tobacco in the same treatment group is taken.

[0054] The test results are shown in Table 1. The results showed that Example 1 had the highest plant height and number of effective leaves, indicating that its water management was most beneficial to tobacco plant growth and development, followed by Example 3. Comparative Example 3 had the lowest plant height and number of effective leaves, indicating that a lack of quantitative monitoring leads to improper water management and inhibits tobacco plant growth. Example 1 had the fewest irrigations, demonstrating the water-saving effect of precision irrigation. Example 2 resulted in frequent irrigation due to "irrigating immediately upon wilting," while Comparative Example 3 also resulted in multiple ineffective irrigations due to delayed experience-based judgment.

[0055] Example 1 showed the highest yield, while Example 2 and Comparative Example 1 had significantly lower yields than Example 1, indicating that improper water management limits yield formation. Furthermore, Example 1 had the highest proportion of high-quality tobacco, suggesting that both over-irrigation and delayed irrigation can lead to a decline in tobacco leaf quality.

[0056] The applicant declares that the technical solution of this invention is illustrated by the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

[0057] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0058] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for judging soil conditions and precise irrigation of Puer tea fields in Puer tobacco-growing areas, characterized in that, The method includes: (1) Combine tobacco plant morphology diagnosis with soil moisture quantitative monitoring to determine the soil moisture status in tobacco fields; (2) Classify the degree of water shortage according to the soil moisture status in the tobacco field and the growth and development stage of the tobacco plants, and carry out precise irrigation for the tobacco plants. In step (1), the morphological diagnosis is based on the dynamic recovery of wilting tobacco leaves and the feel of the leaves. The method of quantitative monitoring of soil moisture is to deploy soil moisture sensors according to the root distribution depth and tobacco plant planting density at different growth stages.

2. The method of claim 1, wherein, The method for classifying the degree of water shortage in step (2) is as follows: the degree of water shortage is divided into four levels: normal, mild water shortage, moderate water shortage, and severe water shortage, wherein: When the soil moisture sensor reading is not lower than the lower limit of the soil moisture content threshold for this growth period, and there is no wilting in the morphological diagnosis, it is considered normal and irrigation is not started. When the soil moisture sensor reading is lower than the lower limit of the soil moisture content threshold for this growth period, and the morphological diagnosis shows that the leaves wilt slightly at noon and recover in the evening, it is judged as mild water shortage, irrigation is not started, and only a warning signal is issued; When the soil moisture sensor reading is below the lower limit of the soil moisture content threshold for this growth period, and the morphological diagnosis shows that the leaves wilt during the day, cannot recover in the evening but recover at night, it is determined to be a moderate water shortage, and irrigation is initiated. When the soil moisture sensor reading is below the lower limit of the soil moisture content threshold for that growth period, and the morphological diagnosis shows that the leaves still do not recover by the next morning, it is determined to be a severe water shortage, and irrigation is initiated. During the ripening period, if the leaf temperature is 30-45℃ on a sunny morning between 9 and 10 am and the ground is dry, and the soil moisture sensor reading is below the lower limit of the ripening period threshold, it is directly determined to be a severe water shortage, and irrigation is initiated.

3. The method of claim 2, wherein, The specific soil moisture content thresholds at different growth stages of tobacco plants are as follows: During the root establishment period, the relative soil moisture content should be 65-75% of the field capacity. During the seedling stage, the relative soil moisture content should be 65-75% of the field capacity. During the root extension stage, the relative soil moisture content is 50-60% of the field capacity. During the vigorous growth period, the relative soil moisture content is 72-80% of the field capacity. During the topping and dome-forming stages, the relative soil moisture content is 60-70% of the field capacity. At maturity, the relative soil moisture content is 60-70% of the field capacity.

4. The method according to any one of claims 1-3, characterized in that, The soil layer setup for quantitative monitoring of soil moisture in step (1) includes: One monitoring point is set up for every 20-50 tobacco plants, and the spacing between adjacent monitoring points along the row is 2-4 tobacco plant row spacings. At each monitoring point, shallow sensors are installed at a soil depth of 10-15cm, and deep sensors are installed at a soil depth of 25-35cm, with a horizontal distance of not less than 20cm between the shallow and deep sensors.

5. The method according to any one of claims 1-4, characterized in that, In step (2), the irrigation methods include: hole irrigation during the root establishment period, plant irrigation during the seedling establishment period, drip irrigation and / or micro-sprinkler irrigation during the vigorous growth period, plant irrigation during the dome stage, and plant irrigation during the maturity stage.

6. The method according to any one of claims 1-5, characterized in that, The specific times for irrigation of tobacco plants at each growth and development stage are as follows: irrigation during the root establishment stage is done at the time of transplanting; irrigation during the seedling establishment stage is done 2-3 days after transplanting; irrigation during the vigorous growth stage is done when water is scarce; irrigation during the dome stage is done 2-3 days before topping or after topping; and irrigation during the maturity stage is done when water is scarce.

7. The method according to claim 3, characterized in that, During the long-term irrigation, an intermittent moisture-conserving irrigation method is adopted, which is as follows: the standard irrigation volume is divided into 2-3 times; the irrigation volume each time is 40%-60% of the standard volume, and irrigation is carried out at intervals of 2-3 days until the soil moisture reaches the target range.

8. The method according to claim 7, characterized in that, The standard irrigation amount is the amount of water required in a single irrigation to bring the soil moisture content to the target threshold for the corresponding growth stage.

9. The method according to any one of claims 1-8, characterized in that, The method also includes setting up a drainage system in the tobacco field, the drainage system being set up in the waist ditch and / or field ditch.

10. The application of the method according to any one of claims 1-9 in the irrigation of tobacco fields.

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