Method for regulating the content of chlorine ions in tobacco leaves

Abstract

The present application relates to the field of tobacco production, and particularly relates to a tobacco leaf chlorine ion content regulation method, comprising the following steps: 1) tobacco field chlorine ion detection: detecting the chlorine ion content in tobacco field soil and tobacco field irrigation water respectively; 2) classifying the tobacco field according to the chlorine ion content of the tobacco field obtained in step 1); 3) controlling chlorine in the tobacco field according to the classification obtained in step 2). The present application realizes effective control of the chlorine ion in the tobacco field by adopting a hierarchical regulation strategy in the process of large-scale agricultural production, with relatively low cost and simpler means. The tobacco leaf chlorine ion regulation method designed in the present application fully coordinates the aspects of tillage, cultivation, field management and irrigation in large-scale agricultural production, and strengthens the chlorine ion regulation strategy from the perspective of material circulation, and has stable effect and practicability.

Description

Technical Field

[0001] This invention relates to the field of tobacco production, and specifically to a method for regulating the chloride ion content in tobacco leaves. Background Technology

[0002] The optimal chloride ion content in flue-cured tobacco leaves is generally 0.3–0.8%. For areas where the average chloride ion content in tobacco leaves exceeds this optimal standard, there are no other large-scale control measures besides prohibiting the application of chloride-containing fertilizers during the tobacco planting season. Currently, although some universities and research institutions have attempted to control chloride ions through improved cropping systems, irrigation cultivation, field management, and soil improvement measures, the control effects are not stable. There is still no well-established, systematic chloride ion control program. Existing chloride control methods and measures are summarized below:

[0003] 1) Prohibit the application of chlorine-containing fertilizers: During the tobacco planting season, do not apply chlorine-containing fertilizers to the soil. Use potassium sulfate or potassium dihydrogen phosphate foliar fertilizers as alternative potassium fertilizers.

[0004] 2) Pre-film followed by straw technique: When tobacco is transplanted to the seedling stage, the surface is covered with mulch film. After entering the vigorous growth stage, the film is removed, soil is piled up and the ridges are sealed with straw. The effect of chlorine control is unstable. Some literature reports a 40% reduction in chloride ions, while others report no significant reduction in chloride ions.

[0005] 3) Soil improvement: By increasing the application of organic fertilizer, the porosity and saturated hydraulic conductivity of the soil are improved, and the chloride ion leaching process is enhanced; polysaccharide nano dechlorination agents adsorb chloride ions in the soil, preventing them from being absorbed by tobacco; soil conditioners containing biochar, desulfurized gypsum and other ingredients are used to improve the soil, and the amount of chloride absorbed by crops is reduced by physical adsorption and competitive absorption characteristics.

[0006] Existing technologies for regulating chloride ions in tobacco leaves have the following major shortcomings:

[0007] 1) Existing chlorine control measures are unstable and have low reproducibility: Most existing chlorine control measures are based on single-batch experimental results, and some methods are only verified through small-scale experiments, resulting in weak reproducibility; the same method has different effects under different experimental conditions, and cannot form a stable chlorine control effect.

[0008] 2) Existing chlorine control measures lack systematicity: Most existing chlorine control measures are specific methods and lack a tiered and feedback mechanism. They cannot be designed and implemented based on the actual chloride ion content of tobacco field soil, irrigation and drainage, etc. Summary of the Invention

[0009] This invention addresses the problems existing in the prior art. Taking a large-scale agricultural system as its background, it integrates agricultural practices such as tillage systems, irrigation, fertilizer application, and field management into methods for regulating chloride ion content in tobacco leaves. Based on the theoretical basis of chloride ion migration and transformation, it integrates current chloride ion control measures to form a systematic chloride control implementation plan. This provides guidance for chloride ion control in tobacco-producing areas, ensuring the supply of high-quality, aromatic tobacco leaves. This invention provides a method for regulating chloride ion content in tobacco leaves, characterized by the following steps:

[0010] 1) Chloride ion detection in tobacco fields: The chloride ion content in tobacco field soil and irrigation water was detected separately;

[0011] 2) Based on the chloride ion content of the tobacco fields obtained in step 1), classify the tobacco fields;

[0012] 3) Based on the classification obtained in step 2), chlorine control is carried out in the tobacco fields.

[0013] Preferably, the chloride ion detection in the tobacco field is performed using silver nitrate titration and / or ion chromatography.

[0014] Preferably, when detecting chloride ion content in tobacco field soil, if the tobacco field area is ≤10 mu, at least one sample should be taken; if the tobacco field area increases by 10 mu, the number of sample groups should increase by at least one.

[0015] Preferably, the set of samples includes at least 10 samples.

[0016] Preferably, the set of samples includes tobacco field soil at a depth of 0-5 cm and / or tobacco field soil at a depth of 20-25 cm.

[0017] Preferably, when detecting the chloride ion content in the irrigation water for tobacco fields, at least one set of samples should be taken from each water source.

[0018] Preferably, in step 2), the classification criteria for the tobacco fields are:

[0019] A1) When the chloride ion content in the tobacco field soil is ≤30mg / L and the chloride ion content in the tobacco field irrigation water is <30mg / L, it is a first-level area;

[0020] A2) When the chloride ion content in the tobacco field soil is 30-50 mg / L and the chloride ion content in the irrigation water is ≤50 mg / L, it is classified as a secondary zone.

[0021] A3) When the chloride ion content in the tobacco field soil is ≤30mg / L and the chloride ion content in the tobacco field irrigation water is ≤50mg / L, it is classified as a Level III area;

[0022] A4) When the chloride ion content in the tobacco field soil is >50mg / L and the chloride ion content in the tobacco field irrigation water is ≤50mg / L, it is a level four area;

[0023] A5) When the chloride ion content in the tobacco field soil is ≤50mg / L and the chloride ion content in the tobacco field irrigation water is >50mg / L, it is classified as a level 5 area.

[0024] A6) When the chloride ion content in the tobacco field soil is >50 mg / L and the chloride ion content in the tobacco field irrigation water is >50 mg / L, it is a level VI area;

[0025] Preferably, the chlorine control in step 3) is as follows:

[0026] B1) In the aforementioned primary areas, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season;

[0027] B2) In the areas described above, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season and the preceding crop. Land preparation should be carried out in late autumn, winter irrigation should be conducted, and intercropping should be adopted.

[0028] B3) In the aforementioned Level 3 areas, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season and in the preceding crop, and intercropping should be adopted.

[0029] B4) In the aforementioned Level IV areas, the application of chlorine-containing fertilizers is completely prohibited; deep plowing in autumn, freezing in winter, land preparation in spring, spring irrigation, and crop rotation are required.

[0030] Chlorine control;

[0031] B5) In the aforementioned Level 5 areas, the application of chlorine-containing fertilizers is completely prohibited, and chlorine control measures should be implemented through crop rotation;

[0032] B6) In the aforementioned Level VI areas, the application of chlorine-containing fertilizers is completely prohibited, deep plowing is carried out in autumn, freezing is carried out in winter, land preparation is carried out in spring, spring irrigation is carried out, chlorine control is implemented through crop rotation, and soil conditioners are added.

[0033] Preferably, it includes at least one of the following technical features:

[0034] C1) In features B1), B2), B3), B4), B5), and B6), the chlorine-containing fertilizer is selected from at least one of chemical fertilizers, compound fertilizers, and organic fertilizers with a water-soluble chloride ion content exceeding 1%.

[0035] In feature B2), the late autumn land preparation equipment is a deep tillage machine;

[0036] In feature B2), the depth of the late autumn land preparation is >30cm;

[0037] In feature B2), the winter irrigation is selected from one or more of furrow irrigation and flood irrigation;

[0038] In C5) features B2) and B3), the intercropping pattern is selected from one or more of the tobacco-sweet potato and tobacco-soybean planting patterns;

[0039] In feature B4) of C6), the device for autumn deep plowing is a moldboard plow;

[0040] In C7) features B4) and B6), the depth of the autumn deep tillage is ≥30cm;

[0041] In features B4) and B6) of C8), the preceding crop in the crop rotation control is selected from at least one of sweet potato, corn, sesame and chili pepper;

[0042] In C9) features B4) and B6), the non-previous crop in the crop rotation chlorine control is selected from cereals and / or legumes;

[0043] In feature B6 of C10), the conditioner is selected from at least one of potassium humate, desulfurized gypsum, biochar, and organic fertilizer.

[0044] Preferably, in feature C9), the non-previous crop is selected from one or more of wheat, corn, and soybean.

[0045] The present invention has at least one of the following beneficial effects:

[0046] 1) Based on the chloride ion content of farmland soil and irrigation water, targeted large-scale agricultural chloride control measures were adopted, forming a systematic chloride control plan;

[0047] 2) The chloride ion regulation scheme for tobacco leaves designed in this invention fully coordinates the tillage, cultivation, field management and irrigation aspects in large-scale agricultural production, strengthens the chloride ion regulation strategy from the perspective of material cycle, and has stable effects and practicality;

[0048] 3) While there are numerous existing methods for regulating chloride ions in flue-cured tobacco leaves, such as pre-film mulching followed by straw application, various conditioners, organic fertilizer application, green manure incorporation, and fertigation, these methods are either expensive to operate, difficult to maintain, and lack stability and sustainability in chloride control, failing to create a virtuous cycle. In contrast, this invention employs a tiered regulation strategy within the large-scale agricultural production process, achieving effective chloride ion control in tobacco fields at a relatively low cost and with simpler methods. Detailed Implementation

[0049] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0050] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0051] 1) Chloride ion detection in tobacco fields

[0052] For tobacco fields smaller than 10 mu, at least one set of samples should be collected. For every additional 10 mu of tobacco field area, the number of sample sets should be increased by one.

[0053] Each sample group includes one irrigation water sample. If there are multiple irrigation water sources, take one sample from each source. Use a clean container to collect 100-200 ml of representative irrigation water and store it away from light. Each sample group includes at least 10 soil samples. Use a sampling shovel to collect approximately 300 grams of soil from the surface 0-5 cm and 300 grams of soil from a depth of 20-25 cm. Ensure adequate sample coverage. Randomly select at least 5 sampling points within the field and collect no fewer than 10 soil samples. Air dry them away from light.

[0054] Soil samples from tobacco fields and irrigation water samples were measured using the silver nitrate titration method specified in NY / T 1121.17-2006 and GB / T 11896, or using more accurate testing methods such as ion chromatography. The chloride ion content in the soil was expressed as mg / kg, and the chloride ion content in the irrigation water was expressed as mg / L.

[0055] 2) Classify tobacco fields

[0056] When the chloride ion content in the tobacco field soil is ≤30mg / L and the chloride ion content in the tobacco field irrigation water is ≤30mg / L, it is classified as a first-level area.

[0057] When the chloride ion content in the tobacco field soil is 30-50 mg / L and the chloride ion content in the irrigation water is ≤50 mg / L, it is classified as a secondary zone.

[0058] When the chloride ion content in the tobacco field soil is ≤30mg / L and the chloride ion content in the tobacco field irrigation water is ≤50mg / L, it is classified as a level three area.

[0059] When the chloride ion content in the tobacco field soil is >50mg / L and the chloride ion content in the tobacco field irrigation water is ≤50mg / L, it is classified as a level four area.

[0060] When the chloride ion content in the tobacco field soil is ≤50mg / L and the chloride ion content in the tobacco field irrigation water is >50mg / L, it is classified as a level 5 area.

[0061] When the chloride ion content in the tobacco field soil is >50 mg / L and the chloride ion content in the tobacco field irrigation water is >50 mg / L, it is classified as a Level VI area.

[0062] 3) Adopt corresponding chlorine control measures according to different conditions in tobacco fields.

[0063] In the primary zone, the application of chlorine-containing fertilizers, including chemical fertilizers, compound fertilizers, and organic fertilizers with a water-soluble chloride ion content exceeding 1%, is prohibited during the tobacco planting season.

[0064] In secondary areas, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season and the preceding crop. The land is prepared in late autumn before tobacco planting, followed by winter irrigation. Deep tillage is performed using a deep plow to loosen the soil to a depth of at least 30cm, ensuring no soil layer is disturbed. Furrow irrigation or flood irrigation is used to irrigate the fields before the soil freezes in late autumn. Intercropping patterns are employed, such as tobacco-sweet potato intercropping or tobacco-soybean intercropping. For furrow irrigation, irrigation ditches are first dug between crop rows. Irrigation water enters the furrows through delivery ditches or canals, and during its flow, it primarily moistens the soil through capillary action from the bottom and walls of the furrow. Gravity also contributes to soil saturation at the bottom of the furrow. Flood irrigation involves not constructing any ditches in the field; water flows freely across the surface, relying on gravity to saturate the soil.

[0065] In the third-level areas, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season and the preceding crop. Intercropping is permitted, with the use of flue-cured tobacco and sweet potato intercropping or flue-cured tobacco and soybean intercropping.

[0066] In Level IV areas, the application of chlorine-containing fertilizers is completely prohibited. Deep plowing is required in the autumn before tobacco planting, followed by winter freezing. Land preparation and irrigation should be carried out in the spring of the year preceding tobacco planting. After the autumn harvest, the soil should be plowed using a moldboard plow to a depth of at least 30cm. During the winter fallow period, the soil should be frozen using low temperatures. In the following spring, rotary tillers and other agricultural machinery should be used early to break up and loosen the soil layer. Irrigation should be carried out in zones or using flood irrigation to wash away chloride ions from the soil surface. Crop rotation is used to control chloride levels. The preceding crop for flue-cured tobacco should be sesame, chili peppers, or other crops with good chloride control properties. The non-preceding crop should be a crop with high biomass or a legume such as wheat, corn, or soybeans. Zoned irrigation refers to dividing the entire area into small plots using constructed field ridges, each of which is then flood irrigated. Flood irrigation refers to direct irrigation without dividing the tobacco field into small zones beforehand; both methods fall under the category of flood irrigation.

[0067] In Level 5 areas, the application of chlorine-containing fertilizers is completely prohibited. Crop rotation is implemented to control chlorine levels. For flue-cured tobacco, the preceding crop should be sesame, pepper, or other crops with good chlorine control. For non-preceding crops, crops with high biomass or legumes such as wheat, corn, and soybeans should be selected.

[0068] In Level VI areas, the application of chlorine-containing fertilizers is completely prohibited. The autumn of the year preceding tobacco planting should be deep plowing, winter freezing, spring tillage, spring irrigation, and after the autumn harvest, the soil should be plowed using a moldboard plow to a depth of no less than 30cm. During the winter fallow period, the soil should be frozen at low temperatures. In the following spring, early use of rotary tillers and other tillage machinery should be employed to break up and loosen the soil layer. Irrigation should be carried out in zones or using flood irrigation to wash away chloride ions from the soil surface. Crop rotation should be implemented to control chloride levels. Before planting flue-cured tobacco, crops with good chloride control, such as sesame and chili peppers, should be selected. For non-previous crops, crops with high biomass or legumes such as wheat, corn, and soybeans should be selected. Soil conditioners should be added, selecting commercially available water-soluble conditioners with low chlorine content that improve soil structure to enhance competitive adsorption of chloride ions and strengthen the leaching process of chloride ions in the soil.

[0069] Meanwhile, the present invention can use methods such as topsoil mulching and straw covering to reduce soil surface evaporation and improve water use efficiency.

[0070] Example 1

[0071] The experimental field was located in Yinzhuang Village, Wangluo Town, Xiangcheng County, Xuchang City, Henan Province. In 2020, the background chloride ion content in the tobacco field soil was 32.2 mg / kg, and the chloride ion content in the irrigation water was 35.4 mg / L. Based on the chloride ion control level, the field was divided into secondary control areas. In control area 1, deep tillage and deep plowing were carried out in the autumn of the year before tobacco planting, and winter irrigation was conducted to flush out chloride ions in the winter of the year before tobacco planting. Chlorine-containing fertilizers were prohibited in the previous crop. After planting one season of sweet potatoes, the chloride ion content in the soil of the control area was 28.7 mg / kg. In control area 1, no chloride control measures were taken, and the chloride ion content in the soil of control area 1 was 35.6 mg / kg. The chloride ion content in the irrigation water did not change significantly. In 2021, Zhongyan 100 was planted in both control area 1 and control area 1, applying local flue-cured tobacco planting and management techniques, and no chloride-containing fertilizers were applied in that season. During the vigorous growth stage of tobacco, 15 tobacco plants with similar growth were randomly selected from both control and control areas 1. One leaf from the upper, middle, and lower parts of each plant was taken, and the chloride ion content was analyzed using boiling water extraction-ion-selective electrode method. After the tobacco leaves were harvested and cured, 15 leaves from each of the lower, middle, and upper parts were randomly selected, crushed, sieved, and extracted. The chloride ion content was then detected using the ion-selective electrode method. The results are shown in Table 1.

[0072] Table 1. Chloride ion content of tobacco leaves in Yinzhuang Control Zone 1 and Control Zone 1, Wangluo Town (unit: %)

[0073]

[0074] It is evident that the chlorine control measures of this invention can effectively reduce the chloride ion content in tobacco leaves, meeting the chloride ion content requirements for flue-cured tobacco purchasing.

[0075] Example 2

[0076] The experiment was conducted in Zhanbei Township, Ziyun Town, Xiangcheng County, Xuchang City, Henan Province. In 2020, the background chloride ion content in the tobacco field soil was 56.1 mg / kg, and the chloride ion content in the irrigation water was 45.5 mg / L. The area was divided into four control zones according to chloride ion control levels. In control zone 2, chili peppers were rotary-tilled and planted in the spring of the year prior to tobacco planting. No chloride-containing fertilizers were applied, and local chili pepper cultivation and management techniques were used. In the autumn of the year prior to tobacco planting, 40 cubic meters per mu were irrigated, and the soil was deeply plowed to 30 cm before freezing at the end of the autumn of the year prior to tobacco planting. The soil was left fallow and frozen in the winter of the year prior to tobacco planting. The soil chloride ion content decreased to 35.2 mg / kg. In control zone 2, no chloride control measures were implemented, and the change in soil chloride ion content in control zone 2 was not significant. Flue-cured tobacco (variety K326) was rotary-tilled and planted in the spring of tobacco planting, using local flue-cured tobacco cultivation and management techniques, and no chloride-containing fertilizers were applied during the season. During the vigorous growth stage of tobacco, 15 tobacco plants with similar growth were randomly selected from both control and control areas 2. One leaf from the upper, middle, and lower parts of each plant was taken, and the chloride ion content was analyzed using boiling water extraction-ion-selective electrode method. After the tobacco leaves were harvested and cured, 15 leaves from each of the lower, middle, and upper parts were randomly selected, crushed, sieved, and extracted. The chloride ion content was then detected using the ion-selective electrode method. The results are shown in Table 2.

[0077] Table 2. Chloride ion content of tobacco leaves in the control and control areas of Zhanbei Township, Ziyun Town (unit: %)

[0078]

[0079]

[0080] It is evident that the chlorine control measures described in this invention can effectively reduce the chloride ion content in tobacco leaves, significantly improving the quality and combustibility of the cured tobacco leaves.

[0081] Example 3

[0082] A field survey was conducted in a tobacco field in Dalushie Village, Xiangcheng County, Xuchang City, using soil samples from adjacent sweet potato, corn, sesame, chili, and tobacco fields as the subjects of the survey. Soil chloride ion content was investigated before planting and after harvest. For each survey, soil samples were taken from two depths: 0–5 cm and 20–25 cm. A five-point sampling method was used for each soil sample, and the samples were thoroughly mixed, with five replicates for each soil sample. Soil samples were extracted using deionized water, and the chloride ion concentration in the extract was measured using an ion-selective electrode method, which was then converted to the chloride ion content in the soil. The chloride ion concentration in the irrigation water for the experimental field ranged from 30.2 to 35.5 mg / L.

[0083] Table 3 shows the results of soil chloride ion content measurements before and after crop planting.

[0084] Table 3. Soil chloride ion concentration (mg / kg) before and after cultivation for different crops

[0085]

[0086] Data are expressed as mean ± standard deviation.

[0087] Before cultivation, the chloride ion content in the surface soil of sweet potato fields was the lowest among the four soil types, with an average chloride ion concentration of 29.73±3.74 mg / kg. In contrast, the chloride ion concentration in the surface soil of corn fields was the highest among the four soil types, with an average of 34.51±5.75 mg / kg. The difference in chloride ion concentration between the deep soil and the surface soil was not significant. The chloride ion concentration in the soil at a depth of 20-25 cm in sesame and sweet potato fields was lower than that in the surface soil.

[0088] After crop harvest, the chloride ion content in soils of different farmlands decreased significantly. The largest decrease was observed in the lower soil layer of sweet potato fields, where the chloride ion content dropped from 23.99±3.74 mg / kg to 13.06±3.90 mg / kg, a reduction of 46%. In chili pepper fields, both the top and bottom soil layers showed reductions exceeding 40%. The smallest decrease was observed in the lower layer of corn fields, where the chloride ion concentration decreased from 35.31±3.03 mg / kg to 27.81±4.67 mg / kg, a reduction of 21%. Data from a single growing season indicates that different crop plantings have a positive effect on soil dechlorination, with chili pepper-grown soil showing relatively better dechlorination effects.

[0089] Example 4

[0090] In Dalushie Village, about 8.5 km north of Xiangcheng County, Xuchang City, Henan Province, seven demonstration plots of tobacco soil conditioner were designed. Each plot involved three rows of tobacco soil (3 rows * 1.2 meters / row * 100 meters, approximately 0.5 mu). The chloride ion content in the irrigation water was close to the average level in the central Henan tobacco-growing region, ranging from 30.2 to 35.5 mg / kg, comparable to the initial soil chloride ion content (approximately 39 mg / kg). The groundwater chloride ion concentration in the irrigated experimental plots was 35.5 mg / kg. The well depth was 40 meters. The seven tobacco soil conditioner demonstration plots are as follows:

[0091] Treatment 1: Biochar (500 kg / mu) + Organic fertilizer (100 kg / mu);

[0092] Treatment 2: Biochar (500 kg / mu) + Potassium humate (100 kg / mu);

[0093] Treatment 3: Biochar (500 kg / mu) + desulfurized gypsum (100 kg / mu);

[0094] Treatment 4: Organic fertilizer (100 kg / mu) + potassium humate (100 kg / mu);

[0095] Treatment 5: Organic fertilizer (100 kg / mu) + desulfurized gypsum (100 kg / mu);

[0096] Treatment 6: Potassium humate (100 kg / mu) + desulfurized gypsum (100 kg / mu).

[0097] 1) Testing the chloride ion content in the soil of the experimental field where soil conditioner was added.

[0098] The results showed that the chloride ion content in the soil at a depth of 5-10 cm from the ground on the side of the ridge in the control group was 16.3 ± 5.5 mg / kg; the chloride ion content in the soil of treatment 1 (biochar + organic fertilizer) was 68.5 ± 7.5 mg / kg, treatment 2 (biochar + potassium humate) was 18.70 ± 11.9 mg / kg, treatment 3 (biochar + desulfurized gypsum) was 112.9 ± 52.3 mg / kg, treatment 4 (organic fertilizer + humic acid) was 15.6 ± 8.0 mg / kg, treatment 5 (organic fertilizer + desulfurized gypsum) was 13.8 ± 1.8 mg / kg, and treatment 6 (humic acid + desulfurized gypsum) was 14.7 ± 3.9 mg / kg. Details are shown in Table 4.

[0099] Table 4. Soil chloride ion content (mg / kg) during the vigorous growth period under different treatments

[0100]

[0101] Data are expressed as mean ± standard deviation.

[0102] (ii) Detection of chloride ion concentration (%) in leaves at different locations during the vigorous growth phase under different treatments.

[0103] The specific test results are shown in Table 5:

[0104] Table 5. Chloride ion concentration (%) in leaves at different locations during the vigorous growth phase under different treatments.

[0105]

[0106] Data are expressed as mean ± standard deviation.

[0107] The chloride ion content in the control group tobacco leaves was 2.39±0.67%, while that in treatment 1 was 1.98±0.45%, treatment 2 was 2.55±0.16%, treatment 3 was 2.43±0.15%, treatment 4 was 1.61±0.44%, treatment 5 was 1.42±0.09%, and treatment 6 was 1.17±0.10%. This indicates that the combined action of biochar, humic acid, and desulfurized gypsum may lead to an increase in chloride ion content. The combined effect of humic acid and desulfurized gypsum in regulating chloride ion content is more significant, reducing chloride ion content by more than 50%. Although the current chloride ion content in tobacco leaves is somewhat different from the ideal conditions (0.3–0.8%), the overall chloride ion content of cured tobacco leaves will gradually decrease as the maturity of the leaves increases.

[0108] Based on data on chloride ion content in soil and tobacco leaves during the vigorous growth period, the chloride ion content in the soil of treatments 1 and 3 was significantly higher than that of the control group, but the chloride ion concentration in the tobacco leaves did not show the same large difference. The chloride ion concentration in tobacco leaves of treatment 1 was reduced by 17.2% compared to the control, indicating that the addition of biochar and organic fertilizer had a good inhibitory effect. Potassium humate and desulfurized gypsum, among other components, had a significant effect on reducing chloride ion levels in tobacco leaves during the vigorous growth period.

[0109] (iii) Complete the testing of flue-cured tobacco leaf samples

[0110] According to the test results, different chlorine-controlling soil conditioners all had significant effects on regulating chloride ions in flue-cured tobacco leaves, effectively controlling the chloride ion content to below 1%. Compared with the control group, the chloride ion content in flue-cured tobacco leaves decreased by 19.5% to 31.3%, demonstrating a considerable chlorine control effect, as shown in Table 6.

[0111] Table 6. Content of major chemical components in flue-cured tobacco leaves (%)

[0112]

[0113]

[0114] (iv) Soil chloride ion detection at the end of the growing season

[0115] Testing showed that the chloride ion content in the soil of treatments 2 to 6 was effectively controlled, with chloride ion concentrations below 20 mg / kg. In contrast, the chloride ion content in the control group and treatment 1 was higher, at 74.4 mg / kg and 53.3 mg / kg, respectively. However, this did not affect the reduction in chloride ion concentration in the tobacco leaves of treatment 1. The specific results are shown in Table 7.

[0116] Table 7. Soil chloride ion content (mg / kg) at the end of the growing season for different treatments

[0117]

[0118] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for regulating chloride ion content in tobacco leaves, characterized in that, Includes the following steps: 1) Chloride ion detection in tobacco fields: The chloride ion content in tobacco field soil and irrigation water was detected separately; 2) Based on the chloride ion content of the tobacco fields obtained in step 1), classify the tobacco fields; the classification criteria for the tobacco fields are as follows: A1) When the chloride ion content in the tobacco field soil is <30 mg / L and the chloride ion content in the tobacco field irrigation water is <30 mg / L, it is a first-level area; A2) When the chloride ion content in the tobacco field soil is 30-50 mg / L and the chloride ion content in the irrigation water is ≤50 mg / L, it is classified as a secondary zone. A3) When the chloride ion content in the tobacco field soil is <30 mg / L and the chloride ion content in the tobacco field irrigation water is 30-50 mg / L, it is a level three area; A4) When the chloride ion content in the tobacco field soil is >50 mg / L and the chloride ion content in the tobacco field irrigation water is <50 mg / L, it is a level four area; A5) When the chloride ion content in the tobacco field soil is <50 mg / L and the chloride ion content in the tobacco field irrigation water is >50 mg / L, it is a level 5 area; A6) When the chloride ion content in the tobacco field soil is >50 mg / L and the chloride ion content in the tobacco field irrigation water is >50 mg / L, it is a level VI area; 3) Based on the classification obtained in step 2), chlorine control is applied to the tobacco fields; the chlorine control is as follows: B1) In the aforementioned primary areas, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season; B2) In the aforementioned secondary area, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season and the preceding crop. Land preparation should be carried out in late autumn, winter irrigation should be conducted, and intercropping should be adopted. B3) In the aforementioned Level 3 areas, the application of chlorine-containing fertilizers is prohibited during the tobacco planting season and in the preceding crop, and intercropping should be adopted. B4) In the aforementioned Level IV areas, the application of chlorine-containing fertilizers is completely prohibited, deep plowing is carried out in autumn, freezing is carried out in winter, land preparation is carried out in spring, spring irrigation is carried out, and chlorine control is implemented through crop rotation. B5) In the aforementioned Level 5 areas, the application of chlorine-containing fertilizers is completely prohibited, and chlorine control measures should be implemented through crop rotation; B6) In the aforementioned Level VI areas, the application of chlorine-containing fertilizers is completely prohibited, deep plowing is carried out in autumn, freezing is carried out in winter, land preparation is carried out in spring, spring irrigation is carried out, chlorine control is implemented through crop rotation, and soil conditioners are added; Among B1), B2), B3), B4), B5), and B6), the chlorine-containing fertilizer is selected from at least one of chemical fertilizers, compound fertilizers, and organic fertilizers with a water-soluble chloride ion content exceeding 1%. In B2) and B3), the intercropping pattern is selected from one or more of the tobacco-sweet potato and tobacco-soybean planting patterns; In B4) and B6), the preceding crop for chlorine control in crop rotation is selected from at least one of sweet potato, corn, sesame and chili pepper; In B4) and B6), the non-previous crop in the crop rotation chlorine control method is selected from cereals and / or legumes; In B6), the conditioner is selected from at least one of potassium humate, desulfurized gypsum, biochar, and soybean organic fertilizer.

2. The method for regulating chloride ion content in tobacco leaves according to claim 1, characterized in that, The chloride ion detection in the tobacco field was performed using silver nitrate titration and / or ion chromatography.

3. The method for regulating chloride ion content in tobacco leaves according to claim 1, characterized in that, When detecting chloride ion content in tobacco field soil, if the tobacco field area is ≤10 mu, at least one sample should be taken. For every additional 10 mu of tobacco field area, the number of sample groups should be increased by at least one.

4. The method for controlling chloride ion content in tobacco leaves according to claim 3, characterized in that, The set of samples shall include at least 10 samples.

5. The method for controlling chloride ion content in tobacco leaves according to claim 3, characterized in that, The set of samples includes tobacco field soil at a depth of 0-5 cm and / or tobacco field soil at a depth of 20-25 cm.

6. The method for controlling chloride ion content in tobacco leaves according to claim 1, characterized in that, When testing the chloride ion content in the irrigation water for tobacco fields, at least one set of samples should be taken from each water source.

7. The method for controlling chloride ion content in tobacco leaves according to claim 1, characterized in that, Includes at least one of the following technical features: In feature B2), the late autumn land preparation equipment is a deep tillage machine; In feature B2), the depth of the late autumn land preparation is >30cm; In feature B2), the winter irrigation is selected from one or more of furrow irrigation and flood irrigation; In feature B4), the device for autumn deep plowing is a moldboard plow; In C5) Features B4) and B6), the depth of the autumn deep tillage is ≥30cm.

8. The method for controlling chloride ion content in tobacco leaves according to claim 1, characterized in that, The non-previous crop is selected from one or more of wheat, corn, and soybean.

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