A method of growing tobacco to improve quality

Abstract

The application discloses a planting method for improving tobacco quality, and the fertilization mode of the planting method is set as T3, or T4, or T5. The fertilization treatment is beneficial to tobacco plant growth, tobacco carbon and nitrogen metabolism, tobacco leaf quality, and improves tobacco leaf yield.

Description

A cultivation method to improve tobacco quality Technical Field

[0001] This invention relates to the field of tobacco cultivation technology, and more specifically to a cultivation method for improving tobacco quality. Background Technology

[0002] Tobacco is an important economic crop harvested for its leaves, playing a vital role in the social development of Yunnan Province. Improving the yield and quality of tobacco leaves is of great significance to tobacco production practices. Based on different processing methods, tobacco can be classified into several types, with flue-cured tobacco being the most widely cultivated type in the world. Tobacco is a crop with extremely high fertilizer requirements and is highly sensitive to fertilizer. Nitrogen, as the mineral nutrient element most needed during tobacco plant growth, is absorbed through the plant roots and transported to the stems and leaves, providing nutrition for their growth and development. It not only affects the external quality of flue-cured tobacco leaves but also participates in the synthesis of nitrogenous compounds in the leaves, thus influencing their taste and aroma. Plant growth and development are inseparable from carbon and nitrogen metabolism; the stronger the metabolism, the better the crop's growth and development, resulting in higher yields and better quality. Many factors influence the strength of crop metabolism, including varietal characteristics, ecological environment conditions, cultivation practices, and fertilization methods. Variety characteristics determine the intensity and coordination of carbon and nitrogen metabolism, ecological conditions determine the accumulation of tobacco products, cultivation measures can ensure and regulate the carbon and nitrogen metabolism process of tobacco plants, and fertilization is a major factor affecting the balance of carbon and nitrogen metabolism.

[0003] This study on fertilization during tobacco cultivation provides a method to improve tobacco quality. Improving the soil environment promotes increased soil enzyme activity, thereby enhancing plant enzyme activity and the metabolic level of tobacco plants. This increases nutrient absorption and accumulation in the plants, ultimately benefiting the agronomic traits of the tobacco plants. Summary of the Invention

[0004] The purpose of this invention is to provide a planting method to improve tobacco quality by applying fertilizer to promote tobacco plant growth, tobacco carbon and nitrogen metabolism, and tobacco leaf quality, thereby increasing tobacco leaf yield.

[0005] A planting method for improving tobacco quality; the planting method is set to a fertilization method of T3, T4, or T5;

[0006] The T3 fertilization method is as follows:

[0007] The fertilizer applied consists of compound fertilizer, straw, and potassium fertilizer;

[0008] The compound fertilizer used is tobacco-specific fertilizer provided by Yunnan Jiehua Clean Energy Development Co., Ltd.; the straw used is pea straw; and the potash fertilizer used is agricultural potassium sulfate provided by SDIC Xinjiang Lop Nur Potash Co., Ltd.

[0009] By weight, compound fertilizer is 35-55 parts, straw is 300-400 parts, and potassium fertilizer is 6-10 parts;

[0010] Compound fertilizer should be applied once before transplanting and twice after transplanting; potassium fertilizer should be applied twice after transplanting; and straw should be crushed and mixed into the soil before transplanting.

[0011] The T4 fertilization method is as follows:

[0012] The fertilizer applied consists of compound fertilizer, straw, soil conditioner, and potassium fertilizer.

[0013] The compound fertilizer used is tobacco-specific fertilizer provided by Yunnan Jiehua Clean Energy Development Co., Ltd.; the straw used is pea straw; the potash fertilizer used is agricultural potassium sulfate provided by SDIC Xinjiang Lop Nur Potash Co., Ltd.; and the soil conditioner used is powder and liquid form provided by Wanzhiyuan Biotechnology Co., Ltd.

[0014] By weight, the amount of compound fertilizer is 35-55 parts, straw is 300-400 parts, soil conditioner powder is 0.5-0.8 parts, soil conditioner liquid is 0.5-0.8 parts, and potassium fertilizer is 6-10 parts.

[0015] Compound fertilizer is applied once before transplanting and twice after transplanting; potassium fertilizer is applied twice after transplanting; straw is crushed and mixed into the soil before transplanting; powdered soil conditioner is applied before and after transplanting; and liquid soil conditioner is applied during the seedling stage, the seedling stage, and the vigorous growth stage.

[0016] The T5 fertilization method is as follows:

[0017] The fertilizer consists of compound fertilizer with 10% reduced nitrogen, straw, soil conditioner, and potassium fertilizer;

[0018] The compound fertilizer with 10% reduced nitrogen content is 90% of the compound fertilizer application amount in T4. The compound fertilizer used is tobacco-specific fertilizer provided by Yunnan Jiehua Clean Energy Development Co., Ltd.; the straw used is pea straw; the potassium fertilizer used is agricultural potassium sulfate provided by Guotou Xinjiang Lop Nur Potash Co., Ltd.; and the soil conditioner used is powder and liquid provided by Wanzhiyuan Biotechnology Co., Ltd.

[0019] By weight: 31.5-48.6 parts compound fertilizer, 300-400 parts straw, 0.5-0.8 parts powdered soil conditioner, 0.5-0.8 parts liquid soil conditioner, and 6-10 parts potassium fertilizer;

[0020] Compound fertilizer should be applied once before transplanting and twice after transplanting. Potassium fertilizer should be applied twice after transplanting. Straw should be crushed and mixed into the soil before transplanting. Powdered soil conditioner should be applied before and after transplanting. Liquid soil conditioner should be applied during the seedling stage, the seedling stage, and the vigorous growth stage.

[0021] The application uses a planting method, wherein the application employs the T3 fertilization method;

[0022] To increase the plant height, stem circumference, internode spacing, and leaf area of ​​tobacco plants;

[0023] And / or, to increase the chlorophyll content in the tobacco leaves of tobacco plants;

[0024] And / or, to reduce the glutamate content of tobacco plants;

[0025] And / or, to increase the enzyme activity of sucrose phosphate synthase in tobacco plants.

[0026] And / or, to increase the enzyme activity of sucrose synthase in tobacco plants.

[0027] The application uses a planting method, wherein the application employs the T4 fertilization method;

[0028] To increase the plant height, stem circumference, internode spacing, and leaf area of ​​tobacco plants;

[0029] And / or, to increase the chlorophyll content in the tobacco leaves of tobacco plants;

[0030] And / or, to reduce the glutamate content of tobacco plants;

[0031] And / or, to increase the enzyme activity of nitrate reductase in tobacco plants;

[0032] And / or, to increase the enzyme activity of glutamine synthase in tobacco plants;

[0033] And / or, to increase the enzyme activity of sucrose synthase in tobacco plants.

[0034] The application uses a planting method, wherein the application employs the T5 fertilization method;

[0035] To increase the plant height, stem circumference, internode spacing, and leaf area of ​​tobacco plants;

[0036] And / or, to increase the chlorophyll content in the tobacco leaves of tobacco plants;

[0037] And / or, to reduce the glutamate content of tobacco plants;

[0038] And / or, to increase the enzyme activity of glutamine synthase in tobacco plants;

[0039] And / or, to increase the enzyme activity of sucrose phosphate synthase in tobacco plants;

[0040] And / or, to increase the enzyme activity of sucrose synthase in tobacco plants.

[0041] The application of planting methods to improve soil fertility, wherein the application adopts the T3 fertilization method;

[0042] To increase the enzyme activity of soil urease;

[0043] And / or, to increase the enzyme activity of soil sucrase in the soil;

[0044] And / or, to increase the enzyme activity of soil catalase in the soil;

[0045] And / or, to increase the enzyme activity of soil acid phosphatase in the soil;

[0046] And / or, to increase the richness of microorganisms in the soil;

[0047] And / or, to improve the uniformity of microorganisms in the soil;

[0048] And / or, to enhance microbial diversity in the soil;

[0049] And / or, to enhance the functional strength of soil microbial communities.

[0050] The application of planting methods to improve soil fertility, wherein the application adopts the T4 fertilization method;

[0051] To increase the enzyme activity of soil urease;

[0052] And / or, to increase the enzyme activity of soil sucrase in the soil;

[0053] And / or, to increase the enzyme activity of soil catalase in the soil;

[0054] And / or, to increase the enzyme activity of soil acid phosphatase in the soil;

[0055] And / or, to increase the richness of microorganisms in the soil;

[0056] And / or, to enhance microbial diversity in the soil;

[0057] And / or, to enhance the functional strength of soil microbial communities.

[0058] The application of planting methods to improve soil fertility, wherein the application adopts the T5 fertilization method;

[0059] To increase the enzyme activity of soil urease;

[0060] And / or, to increase the enzyme activity of soil sucrase in the soil;

[0061] And / or, to increase the enzyme activity of soil catalase in the soil;

[0062] And / or, to increase the enzyme activity of soil acid phosphatase in the soil;

[0063] And / or, to increase the richness of microorganisms in the soil;

[0064] And / or, to enhance microbial diversity in the soil;

[0065] And / or, to enhance the functional strength of soil microbial communities.

[0066] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0067] (1) When planting tobacco, compound fertilizer is selected. On the basis of conventional fertilization, straw return to the field and soil conditioner are applied at the same time. This is beneficial to increase the height of tobacco plants and increase the leaf area of ​​tobacco leaves. It is also beneficial to improve the enzyme activity of plants and thus improve the absorption of nutrients by plants. It is also beneficial to improve the physical and chemical properties of soil, increase soil enzyme activity, and improve the soil microbial environment, which is suitable for the overall growth of tobacco plants.

[0068] (2) On the basis of conventional fertilization, the simultaneous use of straw return to the field and additional soil conditioner can improve the soil’s ability to supply nutrients, stimulate the release of nitrogen and phosphorus in the soil, thereby increasing the potassium content in flue-cured tobacco leaves; it can also significantly reduce the total nitrogen content in tobacco leaves, which is conducive to the yellowing of tobacco leaves, thereby improving the yield and quality of tobacco leaves, and plays an important role in improving the quality of tobacco leaves.

[0069] (3) Soil microbial community diversity Compared with single fertilization, soil microorganisms will increase with different fertilization treatments and will have a certain impact on community composition. Mixed fertilizer application treatment improves microbial diversity and increases species richness, thereby improving the soil environment. Attached Figure Description

[0070] Figure 1 shows the nitrogen uptake of roots under different fertilization treatments in this invention.

[0071] Figure 2 shows the phosphorus uptake of roots under different fertilization treatments in this invention.

[0072] Figure 3 shows the potassium uptake of roots under different fertilization treatments in this invention.

[0073] Figure 4 shows the nitrogen uptake of stems under different fertilization treatments in this invention.

[0074] Figure 5 shows the phosphorus uptake of stems under different fertilization treatments in this invention.

[0075] Figure 6 shows the potassium uptake of stems under different fertilization treatments in this invention.

[0076] Figure 7 shows the nitrogen uptake of leaves under different fertilization treatments in this invention.

[0077] Figure 8 shows the phosphorus uptake of leaves under different fertilization treatments in this invention.

[0078] Figure 9 shows the potassium uptake of leaves under different fertilization treatments in this invention.

[0079] Figure 10 shows the chlorophyll content of different fertilization treatments in this invention.

[0080] Figure 11 shows the glutamic acid content under different fertilization treatments in this invention.

[0081] Figure 12 shows the soil nutrient content of different fertilization treatments in this invention; wherein, Figure a represents hydrolyzable nitrogen, Figure b represents available potassium, Figure c represents no organic matter, and Figure d represents the availability rate.

[0082] Figure 13 shows the nutrient content of tobacco plants under different fertilization treatments in this invention; wherein, Figure a shows the amount of nitrogen absorbed by the tobacco plants, and Figure b shows the amount of potassium absorbed by the tobacco plants.

[0083] Figure 14 is a diagram showing the soil microbial Beta diversity analysis under different fertilization treatments in this invention.

[0084] Figure 15 is a prediction diagram of soil microbial community function under different fertilization treatments in this invention. Detailed Implementation

[0085] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0086] A cultivation method to improve tobacco quality; the selected tobacco variety is Honghua Dajinyuan. The experiment included pot experiments and field experiments.

[0087] 1) Experimental Materials and Methods

[0088] 1.1) Pot experiment

[0089] 1.1.1) Experimental time and location: The experiment was conducted from April to October 2023 at the experimental site behind Yunnan Agricultural University in Panlong District, Kunming City, Yunnan Province. Red soil was selected, and the soil nutrient content is shown in Table 1.

[0090] Table 1. Soil physicochemical properties from the pot experiment.

[0091]

[0092] 1.1.2) Experimental Design: A randomized block design was adopted, with a total of 6 treatments: CK (control); T1, T2, T3, T4, and T5. Each treatment was replicated 3 times, with 7 plants per replicate, for a total of 126 plants. The tobacco seedlings were transplanted on May 12, 2023. The pots had an outer diameter of 34 cm, an inner diameter of 29 cm, and a height of 23 cm, with each pot containing 15 kg of soil.

[0093] The blank treatment indicates that no fertilizer was applied; the blank setting is for later calculations of various substances in the tobacco plants and soil. The T1 treatment is a standard treatment method. The compound fertilizer used was tobacco-specific fertilizer (N:P2O5:K2O=12:10:24) provided by Yunnan Jiehua Clean Energy Development Co., Ltd.; the potash fertilizer was agricultural-grade potassium sulfate (K2SO4:52%, meaning a K2SO4 content of 52%) provided by Guotou Xinjiang Lop Nur Potash Co., Ltd.; the farmyard manure was well-rotted farmyard manure (N:P2O5:K2O=9:5:10) used by the Jiuxiang Tobacco Station in Yiliang County, Kunming City, Yunnan Province; the straw was pea straw; the soil conditioner used was powder and liquid formulation (total bacterial count ≥0.5*10) provided by Wanzhiyuan Biotechnology (Shenzhen) Co., Ltd. 3 (N+P2O5+K2O≥6%).

[0094] Table 2: Fertilizer application table for T1

[0095]

[0096] In Table 2, the fertilizer applied at T1 consisted of compound fertilizer and potassium fertilizer; 30% of the compound fertilizer added to each tobacco plant was applied as base fertilizer; topdressing was applied on the 28th and 52nd day after transplanting. The first topdressing added 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing added 35% of the compound fertilizer and 50% of the potassium sulfate. After transplanting, potassium sulfate was added 2-3 hours after the compound fertilizer was applied.

[0097] Table 3: Fertilizer Application Table for T2

[0098]

[0099] In Table 3, the fertilizer applied for T2 was farmyard manure, which was mixed into the soil 10 days before transplanting.

[0100] Table 4: Fertilizer application table for T3

[0101]

[0102] In Table 4, the fertilizer applied for T3 consisted of compound fertilizer, straw, and potassium fertilizer. 30% of the compound fertilizer added to each tobacco plant was applied as base fertilizer. Topdressing was applied on the 28th and 52nd days after transplanting. The first topdressing consisted of 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing consisted of the same combination. Potassium sulfate was added 2-3 hours after the compound fertilizer was applied following transplanting. Pea straw was completely mixed into the soil 10 days before transplanting, and topdressing was applied using a ring application method.

[0103] Table 5: Fertilizer Application Table for T4

[0104]

[0105] Table 5 shows that the fertilizer applied under T4 consisted of compound fertilizer, straw, potassium fertilizer, and soil conditioner powder. 30% of the compound fertilizer added to each tobacco plant was applied as base fertilizer. Topdressing was applied on days 28 and 52 after transplanting. The first topdressing consisted of 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing consisted of the same combination. Potassium sulfate was added 2-3 hours after the compound fertilizer was applied following transplanting. Pea straw was completely mixed into the soil 10 days before transplanting, and topdressing was applied using a ring application method. 30% of the compound fertilizer was applied as base fertilizer. Topdressing was applied on days 28 and 52 after transplanting. The first topdressing consisted of 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing consisted of the same combination. Potassium sulfate was added 2-3 hours after the compound fertilizer was applied following transplanting. Pea straw was completely mixed into the soil 10 days before transplanting, and topdressing was applied using a ring application method. For soil conditioner powder, use 0.6g per plant (0.3g / application). The first application should be made one day before transplanting, and the second application should be 15-20 days after the first. For soil conditioner liquid, add it after the second application of the powder, with an interval of 1-2 hours between the two applications, and apply it during the seedling stage, the crowning stage, and the vigorous growth stage, respectively.

[0106] Table 6: Fertilizer Application Table for T5

[0107]

[0108] In Table 6, the fertilizer applied for T5 consisted of compound fertilizer with 10% reduced nitrogen, straw, potassium fertilizer, and soil conditioner powder. The 10% nitrogen-reduced compound fertilizer was 90% of the amount applied in T4, with 30% of the compound fertilizer added per tobacco plant applied as base fertilizer. Topdressing was applied on the 28th and 52nd days after transplanting. The first topdressing added 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing added 35% of the compound fertilizer and 50% of the potassium sulfate. Potassium sulfate was added 2-3 hours after the compound fertilizer was applied after transplanting. Pea straw was completely mixed into the soil 10 days before transplanting, and topdressing was applied using a ring application method. 30% of the compound fertilizer was applied as base fertilizer. Topdressing was applied on the 28th and 52nd days after transplanting. The first topdressing added 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing added 35% of the compound fertilizer and 50% of the potassium sulfate. Potassium sulfate was added 2-3 hours after the compound fertilizer was applied after transplanting. Pea stalks should be completely mixed into the soil 10 days before transplanting, and topdressing should be done using the ring application method. Soil conditioner powder should be applied at a rate of 0.6g per plant (0.3g / application), with the first application one day before transplanting, and the second application 15-20 days after the first. Soil conditioner liquid should be added after the second application of the powder, with an interval of 1-2 hours between the two applications, and applied during the seedling stage, the crowning stage, and the vigorous growth stage, respectively. The application rates for T1, T2, T3, T4, and T5 fertilizers are shown in Table 2-6.

[0109] 1.1.3) Measurement Items and Methods:

[0110] (1) Soil nutrient content determination: Soil samples were collected at five points before transplanting and at 50, 65, and 80 days after transplanting (d represents days). Plant debris and gravel were removed, and the samples were air-dried and passed through 0.25 mm and 0.15 mm sieves. The samples were then stored in sealed bags, and the pH, organic matter, available phosphorus, available potassium, total phosphorus, total potassium, total nitrogen, and hydrolyzable nitrogen in the soil were determined. Specifically: pH was determined using a pH meter; organic matter was determined using the external heating potassium dichromate oxidation method; available phosphorus was determined using the sodium bicarbonate method; available potassium was determined using the 1 mol / L ammonium acetate extraction flame photometer method; hydrolyzable nitrogen was determined using the alkaline diffusion method; total nitrogen was determined using the Kjeldahl method; total phosphorus was determined using the sulfuric acid-perchloric acid digestion molybdenum antimony colorimetric method; and total potassium was determined using the potassium hydroxide fusion flame photometer method.

[0111] (2) Agronomic trait survey: 50, 65, and 80 days after transplanting, tobacco plants with uniform growth in each treatment were selected for investigation. Plant height, stem circumference, internode distance, and maximum leaf area were measured. The formula for calculating the maximum leaf area is as follows:

[0112] Maximum leaf area (S) = Correction coefficient (K) * Maximum leaf length * Maximum leaf width.

[0113] (3) Determination of chlorophyll content: At 50, 65, and 80 days after transplanting, three tobacco plants with uniform growth were selected from each treatment, and the chlorophyll content was determined by acetone extraction colorimetric method. The formula for calculating chlorophyll content is as follows:

[0114] Chlorophyll content (mg / g) = (20.29A645 + 8.04A665) * extraction liquid volume / (1000 * leaf fresh weight).

[0115] (4) Determination of nutrient accumulation in tobacco plants: At 50, 65 and 80 days after transplanting, tobacco plants with uniform growth were selected from each treatment, and the dry and fresh weight of the whole plant was weighed and the nitrogen, phosphorus and potassium contents were determined. The dry and fresh weight was determined by the drying weight method; the nitrogen was determined by the hydrogen peroxide-sulfuric acid digestion method; the phosphorus was determined by the spectrophotometric method; and the potassium was determined by the flame atomic absorption spectrophotometric method.

[0116] (5) Determination of enzyme activity and related products in tobacco leaves: At 50d, 65d and 80d after transplanting, three tobacco plants with uniform growth were selected from each treatment, and the leaves were selected for enzyme activity determination. The activities of nitrate reductase (NR), glutamine synthase (GS), sucrose phosphate synthase (SPS) and sucrose synthase (SS) in fresh tobacco leaves were determined using a kit, and the content of glutamate (Glu) was determined. The kit was provided by Suzhou Gres Biotechnology Co., Ltd.

[0117] (6) Soil enzyme activity determination: At 50d, 65d and 80d after transplanting, three tobacco plants with the same growth were selected from each treatment, and the leaves were selected for enzyme activity determination. The activities of soil acid phosphatase (S-ACP), catalase (S-CAT), urease (S-UE) and sucrase (S-SC) were determined using a kit provided by Beijing Solarbio Science & Technology Co., Ltd.

[0118] (7) Metagenomic analysis: Soil samples were taken from soil 80 days after transplanting. Visible impurities in the soil were removed. Multiple samples from the same sample were mixed evenly and 5-10g were taken, stored in sterile self-sealing bags, and labeled. All samples were stored on dry ice and sent to Shanghai Meiji Biomedical Technology Co., Ltd. for metagenomic sequencing.

[0119] 1.2) Field trials

[0120] 1.2.1) Experiment time and location: The experiment was conducted from April to October 2023 in Jiuxiang Township, Yiliang County, Kunming City, Yunnan Province. Red soil was selected, and the soil nutrient content is shown in Table 7.

[0121] Table 7 Soil physicochemical properties from field trials

[0122]

[0123] 1.2.2) Experimental Design: The experiment adopted a randomized block design with a total of 6 treatments; as shown in 1.1.2), namely CK (control); T1, T2, T3, T4, and T5. Each treatment was repeated 3 times, with 240 plants per replicate, for a total of 720 plants. The control treatment received no fertilizer and was included for later calculations of tobacco plant and soil composition. Treatment T1 used conventional methods. The selection of compound fertilizer, potassium fertilizer, farmyard manure, straw, and soil conditioner is as described in 1.1.2). The fertilization and management methods for T1, T2, T3, T4, and T5 are the same as described in 1.1.2).

[0124] 1.2.3) Measurement Items and Methods

[0125] (1) Soil nutrient content determination: The determination was carried out at 72d, 90d and 108d after transplanting, using the same method as (1) in 1.1.3).

[0126] (2) Agronomic traits survey: The measurements were taken at 72d, 90d and 108d after transplanting, using the same method as (2) in 1.1.3).

[0127] (3) Nutrient accumulation in tobacco plants: The accumulation was measured at 72d, 90d and 108d after transplanting, using the same method as (4) in 1.1.3.

[0128] (4) Determination of economic traits: The tobacco leaves are graded and weighed according to the grading standards, and the tobacco yield is determined. Based on the grading results and the tobacco purchase price of the year, the proportion of medium and high grade tobacco, output value, and economic traits of each treatment are calculated.

[0129] 2.1) Effects of fertilization treatments on the growth and development of tobacco plants at different growth stages under potted conditions

[0130] 2.1.1) Effects of different fertilization treatments on agronomic traits of tobacco plants at different growth stages, as shown in Table 8.

[0131] Table 8 Agronomic traits of tobacco plants during their growth period

[0132]

[0133] Note: Groups without identical lowercase letters indicate statistically significant differences between treatments (P < 0.05), while groups without identical uppercase letters indicate statistically significant differences between treatments (P < 0.01); the same interpretation applies to corresponding lowercase letters in tables or figures in this application.

[0134] Table 8 shows that at 50, 65, and 80 days after transplanting, the plant height, stem circumference, internode distance, and maximum leaf area of ​​the T1, T2, T3, T4, and T5 treatment groups were significantly higher than those of the CK treatment. In this application, CK refers to tobacco cultivation without added fertilizer.

[0135] Fifty days after transplanting, the plant height of treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 36.15%, 38.53%, and 41.22%, respectively; the stem circumference of treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 9.41%, 16.5%, and 3.8%, respectively; the internode distance of treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 9.14%, 11.29%, and 8.06%, respectively; and the maximum leaf area of ​​treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 28.15%, 21.75%, and 22.41%, respectively. In contrast, the plant height, stem circumference, internode distance, and maximum leaf area of ​​treatment T2 were all lower than those of treatment T1, by 19.59%, 9.74%, 17.74%, and 16.69%, respectively. 50 days after transplanting, compared with the T1 treatment, the T3, T4, and T5 treatments all helped to increase the plant height, stem circumference, and internode distance of tobacco plants and the leaf expansion of tobacco leaves, while the T2 treatment was not conducive to increasing the plant height, stem circumference, and internode distance of tobacco plants and the leaf expansion of tobacco leaves. Sixty-five days after transplanting, the plant height of treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 15.54%, 35.64%, and 27.06%, respectively. The plant height of treatment T2 was significantly lower than that of treatment T1, by 47.84%. The stem circumference of treatments T2, T3, T4, and T5 was significantly lower than that of treatment T1, by 32.04%, 4.01%, 6.98%, and 12.02%, respectively. There was no significant difference in plant height between treatments T3, T4, and T5 and treatment T1. The internode distance of treatment T2 was significantly lower than that of treatment T1, by 28.94%. There was no significant difference in maximum leaf area between treatments T3, T4, and T5 and treatment T1. The maximum leaf area of ​​treatment T2 was significantly lower than that of treatment T1, by 42.02%. Sixty-five days after transplanting, compared to treatment T1, treatments T3, T4, and T5 were beneficial for increasing plant height, while treatment T2 could no longer meet the needs of later plant growth and development, resulting in a slowdown in plant growth rate and hindering the increase of plant height, stem circumference, internode distance, and leaf expansion. Eighty days after transplanting, plant height, stem circumference, and internode distance in treatments T3, T4, and T5 were not significantly different from those in treatment T1. Plant height, stem circumference, and internode distance in treatment T2 were significantly lower than those in treatment T1, by 48.82%, 36.24%, and 29.13%, respectively. The maximum leaf area in treatment T2 was significantly lower than that in treatment T1, by 47.17%. The maximum leaf area in treatments T3 and T5 was not significantly different from that in treatment T1. The maximum leaf area in treatment T4 was significantly higher than that in treatment T1, by 12.31%.The agronomic traits of the T2 treatment were significantly lower than those of the T1, T3, T4, and T5 treatments. Under pot conditions, the T2 treatment could not meet the growth and development needs of tobacco plants during their growth period, resulting in slow growth and hindering their growth and development. Compared with the T1 treatment, the T3, T4, and T5 treatments were more conducive to the growth and development of tobacco plants in the early growth stage, while the T4 treatment was more conducive to the growth and development of tobacco plants in the later growth stage.

[0136] 2.1.2) Effects of fertilization treatment on nutrient accumulation in the roots, stems, and leaves of tobacco plants under pot conditions

[0137] 2.1.2.1) Nutrient accumulation in tobacco roots As shown in Figure 1-3, at 50d, 65d and 80d after transplanting, the nitrogen, phosphorus and potassium uptake of tobacco roots in the CK treatment were significantly lower than those in the T1, T2, T3, T4 and T5 treatments.

[0138] Fifty days after transplanting, nitrogen uptake in treatments T3, T4, and T5 was significantly higher than that in treatment T1, by 95.66%, 90.14%, and 142.18%, respectively. Nitrogen uptake in treatment T2 was not significantly different from that in treatment T1. Compared to treatment T1, phosphorus uptake in treatment T2 was not significantly different, while phosphorus uptake in treatments T3, T4, and T5 was significantly higher, by 140.35%, 84.21%, and 182.46%, respectively. Compared to treatment T1, potassium uptake in treatment T2 was not significantly different, while potassium uptake in treatments T3, T4, and T5 was significantly higher, by 72.34%, 56.19%, and 107.75%, respectively. Sixty-five days after transplanting, nitrogen uptake in treatments T2, T3, T4, and T5 was significantly lower than that in treatment T1, by 73.92%, 27.34%, 35.04%, and 49.88%, respectively. Phosphorus uptake in treatments T3, T4, and T5 was not significantly different from that in treatment T1, while phosphorus uptake in treatment T2 was significantly lower than that in treatment T1, by 57.43%. Potassium uptake in treatments T3, T4, and T5 was significantly higher than that in treatment T1, by 39.4%, 20.16%, and 17.83%, respectively, while potassium uptake in treatment T2 was significantly lower than that in treatment T1, by 61.03%. Eighty days after transplanting, compared with T1 treatment, there was no significant difference in nitrogen uptake among treatments T3, T4, and T5, while treatment T2 showed significantly lower nitrogen uptake, 75.93% lower than T1. Phosphorus uptake in treatments T3, T4, and T5 was significantly higher than T1, by 46.83%, 15.61%, and 5.37%, respectively, while treatment T2 showed significantly lower phosphorus uptake, 64.63% lower than T1. Compared with T1, there was no significant difference in potassium uptake among treatments T3, T4, and T5, while treatment T2 showed significantly lower potassium uptake, 68.85% lower than T1.

[0139] 2.1.2.2) Nutrient Accumulation in Tobacco Stems: As shown in Figure 4-6, at 50, 65, and 80 days after transplanting, the nitrogen, phosphorus, and potassium uptake in the roots of the CK treatment were significantly lower than those of T1, T2, T3, T4, and T5. At 50 days after transplanting, there were no significant differences in nitrogen uptake among the T3, T4, and T5 treatments, but the nitrogen uptake in the T2 treatment was significantly lower than that in the T1 treatment, by 80.59%. The phosphorus uptake in the T3, T4, and T5 treatments was significantly higher than that in the T1 treatment, by 79.84%, 87.5%, and 87.5%, respectively, while the phosphorus uptake in the T2 treatment was significantly lower than that in the T1 treatment, by 40.73%. The potassium uptake in the T3, T4, and T5 treatments was significantly higher than that in the T1 treatment, by 27.07%, 66.58%, and 55.01%, respectively, while the potassium uptake in the T2 treatment was significantly lower than that in the T1 treatment, by 62.3%. Sixty-five days after transplanting, nitrogen uptake in treatments T3, T4, and T5 was significantly higher than that in treatment T1, by 53.76%, 67.52%, and 69.08%, respectively. Nitrogen uptake in treatment T2 was significantly lower than that in treatment T1, by 59.54%. Phosphorus uptake in treatments T3, T4, and T5 was significantly higher than that in treatment T1, by 41.4%, 45.02%, and 52.74%, respectively. Phosphorus uptake in treatment T2 was significantly lower than that in treatment T1, by 61.48%. Compared with treatment T1, there was no significant difference in potassium uptake among treatments T3, T4, and T5. Potassium uptake in treatment T2 was significantly lower than that in treatment T1, by 73.3%. Eighty days after transplanting, nitrogen uptake in treatments T2, T3, T4, and T5 was significantly lower than that in treatment T1, by 89.49%, 18.92%, 11.7%, and 30.61%, respectively. Phosphorus uptake in treatments T3, T4, and T5 was significantly higher than that in treatment T1, by 65.2%, 61.26%, and 31.33%, respectively, while phosphorus uptake in treatment T2 was significantly lower than that in treatment T1, by 62.65%. Compared with treatment T1, there was no significant difference in potassium uptake among treatments T3, T4, and T5, while potassium uptake in treatment T2 was significantly lower than that in treatment T1, by 79.86%.

[0140] 2.1.2.3) Nutrient accumulation in tobacco leaves As shown in Figure 7-9, at 50d, 65d and 80d after transplanting, the nitrogen, phosphorus and potassium uptake by the roots of the CK treatment were significantly lower than those of the T1, T2, T3, T4 and T5 treatments.

[0141] Fifty days after transplanting, there were no significant differences in nitrogen uptake among treatments T3, T4, and T5. Treatment T2 showed significantly lower nitrogen uptake than treatment T1, by 81.86%. Phosphorus uptake in treatments T3, T4, and T5 was significantly higher than in treatment T1, by 97.89%, 108.54%, and 116.14%, respectively. Treatment T2 showed significantly lower phosphorus uptake than treatment T1, by 29.01%. Potassium uptake in treatments T3, T4, and T5 was significantly higher than in treatment T1, by 34.4%, 64.4%, and 62%, respectively. Treatment T2 showed significantly lower potassium uptake than treatment T1, by 55.83%. At 65 days post-transplanting, there were no significant differences in nitrogen uptake among treatments T3, T4, and T5. Treatment T2 showed significantly lower nitrogen uptake than treatment T1, by 74.12%. Treatments T2, T3, T4, and T5 showed significantly higher phosphorus uptake than treatment T1, by 179.94%, 175.57%, 126.33%, and 265.59%, respectively. Treatments T3, T4, and T5 showed significantly higher potassium uptake than treatment T1, by 25.48%, 8.9%, and 14.33%, respectively. Treatment T2 showed significantly lower potassium uptake than treatment T1, by 71.46%. Eighty days after transplanting, nitrogen uptake in treatments T2, T3, T4, and T5 was significantly lower than that in treatment T1, by 86.30%, 22.76%, 24.51%, and 33.28%, respectively. Phosphorus uptake in treatments T3, T4, and T5 was significantly higher than that in treatment T1, by 33.16%, 20.68%, and 4.14%, respectively. Phosphorus uptake in treatment T2 was significantly lower than that in treatment T1, by 67.04%. Compared with treatment T1, there was no significant difference in potassium uptake among treatments T3, T4, and T5. However, potassium uptake in treatment T2 was significantly lower than that in treatment T1, by 81.63%.

[0142] In summary, the trends of nutrient absorption in roots, stems, and leaves of tobacco plants under each treatment are shown in Figure 1-9. The differences in nutrient absorption among the treatments were initially apparent 50 days after transplanting. Compared with treatment T1, treatments T3, T4, and T5 had a very favorable effect on nutrient absorption during tobacco plant growth, increasing nutrient absorption and thus improving nutrient utilization, which is beneficial to tobacco plant growth and development. The proportion of nutrient absorption distribution in tobacco plants was highest in leaves, followed by stems, and lowest in roots. Furthermore, potassium absorption was higher than nitrogen absorption, which was higher than phosphorus absorption in each part.

[0143] 2.2) Effects of different fertilization treatments on the physiological and biochemical characteristics of tobacco plants at different growth stages under potted conditions

[0144] 2.2.1) Effects of chlorophyll content in tobacco leaves at different growth stages

[0145] The chlorophyll content in tobacco leaves reflects the growth status of the tobacco plant. As shown in Figure 10, at 50, 65, and 80 days after transplanting, the chlorophyll content in tobacco leaves treated with T2 was significantly lower than that in other treatment groups, and even much lower than that in the control (CK) treatment. At 50 days after transplanting, the chlorophyll content in treatments T3 and T4 was significantly lower than that in treatment T1, by 26.19% and 12.86%, respectively, while the chlorophyll content in treatment T5 was not significantly different from that in treatment T1. At 65 days after transplanting, the chlorophyll content in treatments T3 and T5 was significantly higher than that in treatment T1, by 26.36% and 16.28%, respectively, while the chlorophyll content in treatment T4 was significantly lower than that in treatment T1, by 23.26%. At 80 days after transplanting, the chlorophyll content in treatment T5 was not significantly different from that in treatment T1, while the chlorophyll content in treatments T3 and T4 was significantly lower than that in treatment T1, by 2.19% and 31.87%, respectively. Sixty-five days after transplanting, the chlorophyll content of the T3 treatment was slightly higher than that of the original treatment at 50 days after transplanting, by 0.02%. Moreover, the T3 treatment showed the smallest decrease in pigment content during the 65-80 days after transplanting, indicating that the T3 treatment has a certain promoting effect on the accumulation of light and chlorophyll content in tobacco plants during their growth process.

[0146] In summary, the results are consistent with those for agronomic traits and nutrient uptake. Treatment T2 is detrimental to photosynthetic accumulation in tobacco plants during growth, thus affecting their growth and development. Treatments T1, T3, T4, and T5 have a more favorable effect on tobacco plant growth. Compared to treatment T1, treatments T3 and T5 are more conducive to photosynthetic accumulation in tobacco plants during growth.

[0147] 2.2.2) Effects of different fertilization treatments on the activity of carbon and nitrogen metabolism enzymes in tobacco plants

[0148] 2.2.2.1) Nitrate reductase (NR) is an extremely important rate-limiting enzyme in the nitrogen metabolism process in plants. It is related to the effective absorption and utilization of nitrogen fertilizer by crops. The stronger the NR activity, the higher the effective absorption and utilization of nitrogen fertilizer by crops.

[0149] Table 9. Nitrate reductase in tobacco leaves during the growing season

[0150]

[0151] Table 9 shows that at 50 days post-transplantation, the NR enzyme activities in treatments T3 and T5 were significantly higher than those in treatment T1, by 3.2% and 13.97%, respectively; while the NR enzyme activities in treatments T2 and T4 were significantly lower than those in treatment T1, by 23.03% and 14.5%, respectively. At 65 days post-transplantation, the NR enzyme activity in treatment T2 was significantly lower than that in treatment T1, by 30.46%; the NR enzyme activities in treatments T3 and T5 showed no significant difference from those in treatment T1; and the NR enzyme activity in treatment T4 was significantly higher than that in treatment T1, by 10.57%. At 80 days post-transplantation, the NR enzyme activities in treatments T2, T3, and T5 were all significantly lower than those in treatment T1, by 77.4%, 17.02%, and 18.49%, respectively; and the NR enzyme activity in treatment T4 showed no significant difference from that in treatment T1. At 50 days post-transplantation, treatment T5 showed the highest value, significantly higher than the other treatments, after which the activity first increased and then decreased. Within 50-80 days after transplanting, the NR activity of the T2 treatment was consistently significantly lower than that of the CK treatment, indicating that the T2 treatment was not conducive to improving the NR activity of tobacco plants. At 65 and 80 days after transplanting, the activity of the T4 treatment was the highest, indicating that the T4 treatment was beneficial to improving the NR activity of tobacco plants, thereby enhancing the utilization and absorption of nitrogen in tobacco plants.

[0152] 2.2.2.2) Glutamine synthase (GS) is a regulatory enzyme of the nitrogen metabolism center in plants, possessing high NH4+ content. + Affinity can convert NH4 + Catalytic synthesis of glutamine, an important form of nitrogen storage in plants. Glutamine is also involved in the synthesis of NH4+ within plants. + At high concentrations, glutamine is synthesized in large quantities, which can prevent NH4+. + Accumulated poisoning.

[0153] Table 10. Glutamine synthase table of tobacco leaves during the growth period

[0154]

[0155] Table 10 shows that from 50 to 80 days after transplanting, the CK and T2 treatments showed a trend of first decreasing and then increasing, while the T1, T3, T4, and T5 treatments showed a trend of first increasing and then decreasing. The T1 treatment maintained a relatively stable trend, but with a slight decrease. At 50 days after transplanting, the GS enzyme activity in the T2 treatment was significantly lower than that in the T1 treatment, by 56.64%; the GS enzyme activities in the T3 and T4 treatments were not significantly different from those in the T1 treatment; the GS enzyme activity in the T5 treatment was significantly higher than that in the T1 treatment, by 9.56%. At 65 days after transplanting, the GS enzyme activity in the T2 treatment was significantly lower than that in the T1 treatment, by 75.71%; the GS enzyme activities in the T3, T4, and T5 treatments were not significantly different from those in the T1 treatment. At 80 days after transplanting, the GS enzyme activity in treatment T2 was significantly lower than that in treatment T1, by 25.47%. The GS enzyme activities in treatments T3, T4, and T5 were all significantly higher than those in treatment T1, by 61.52%, 64.77%, and 87.26%, respectively. During the period of 65-80 days after transplanting, GS enzyme activity showed a significant decrease, with the T4 treatment exhibiting a more pronounced decline. This indicates that treatments T4 and T5 contribute to a trend of initial increase followed by decrease in GS activity in tobacco leaves.

[0156] 2.2.2.3) Sucrose phosphate synthase (SPS) is a key regulatory enzyme in plants that catalyzes the synthesis of sucrose. Its activity is positively correlated with the sucrose content in tobacco leaves. The higher the enzyme activity, the higher the sucrose content. Moreover, the reaction it catalyzes is irreversible, so it is the key point for the allocation of photosynthetic products to sucrose in plants.

[0157] Table 11 Table of Sucrose Phosphate Synthases in Tobacco Leaves During Growth Period

[0158]

[0159] Table 11 shows that 50 days after transplanting, the SPS enzyme activities in treatments T2 and T5 were significantly lower than those in treatment T1, by 58.63% and 18.9%, respectively; the SPS enzyme activities in treatments T3 and T4 showed no significant difference from those in treatment T1. At 65 days after transplanting, the SPS enzyme activities in treatments T2, T3, and T4 were significantly lower than those in treatment T1, by 31.96%, 15.88%, and 17.8%, respectively; the SPS enzyme activity in treatment T5 was significantly higher than that in treatment T1, by 20.43%. At 80 days after transplanting, the SPS enzyme activities in treatments T2 and T4 were significantly lower than those in treatment T1, by 30.37% and 22%, respectively; the SPS enzyme activities in treatments T3 and T5 were significantly higher than those in treatment T1, by 17.72% and 25.2%, respectively. This indicates that treatments T3 and T5 are beneficial for increasing SPS enzyme activity, thereby enhancing the sucrose synthesis capacity of flue-cured tobacco, while treatments CK and T2 are detrimental to sucrose synthesis in flue-cured tobacco.

[0160] 2.2.2.4) Sucrose synthase (SS) is a two-way reaction enzyme that can catalyze both the synthesis and decomposition of carbohydrates. Among them, SS-II catalyzes the reaction between free fructose and glucose donor UDPG, and is one of the key enzymes in carbon metabolism.

[0161] Table 12 Table of Sucrose Synthetic Enzymes in Tobacco Leaves During Growth Period

[0162]

[0163] Table 12 shows that at 50 days post-transplantation, the SS enzyme activities of treatments T2, T3, and T4 were not significantly different from those of treatment T1; the SS enzyme activity of treatment T5 was significantly lower than that of treatment T1, by 16.11%. At 65 days post-transplantation, the SS enzyme activity of treatment T2 was significantly higher than that of treatment T1, by 163.50%; the SS enzyme activity of treatment T3 was significantly lower than that of treatment T1, by 25.83%; the SS enzyme activities of treatments T4 and T5 were not significantly different from those of treatment T1. At 80 days post-transplantation, the SS enzyme activity of treatment T2 was not significantly different from that of treatment T1; the SS enzyme activities of treatments T3, T4, and T5 were significantly higher than those of treatment T1, by 12.33%, 23.93%, and 20.80%, respectively. From 50 to 80 days post-transplantation, the SS-II enzyme activities of the CK, T1, and T2 treatment groups showed a trend of first increasing and then decreasing, while the T3, T4, and T5 treatment groups showed a continuous increasing trend. Based on the above explanation, treatments T3, T4, and T5 are beneficial for increasing SS enzyme activity, thereby promoting the carbon metabolism process of flue-cured tobacco, while treatments CK, T1, and T2 are detrimental to sucrose synthesis in flue-cured tobacco.

[0164] 2.2.3) Effects of different fertilization treatments on carbon and nitrogen metabolism enzyme-related products in tobacco plants

[0165] As shown in Figure 11, from 50 to 80 days after transplanting, the glutamic acid (Glu) content in the CK and T2 treatments showed a trend of first decreasing and then increasing, while the Glu content in the T1, T3, T4, and T5 treatments showed a continuous decreasing trend. Furthermore, the Glu content in the tobacco leaves of the T2 treatment was significantly lower than that of the other treatment groups, even far lower than that of the CK treatment. At 50 days after transplanting, the Glu content in the T3 and T5 treatments was significantly higher than that in the T1 treatment, by 12.98% and 36.08%, respectively, while the Glu content in the T4 treatment was not significantly different from that in the T1 treatment. At 65 days after transplanting, the Glu content in the T3 and T5 treatments was significantly lower than that in the T1 treatment, by 45.76% and 49.17%, respectively, while the Glu content in the T4 treatment was not significantly different from that in the T1 treatment. At 80 days after transplanting, the Glu content in the T3, T4, and T5 treatments was significantly lower than that in the T1 treatment, by 71.69%, 38.86%, and 10.99%, respectively. Fifty days after transplanting, significant differences were observed among the treatments. Treatment T5 had the highest Glu content, exceeding that of treatment T2 by 180.77%. Treatment T3 had the lowest Glu content at both 65 and 80 days post-transplanting. During the 50-80 day period after transplanting, treatments T1, T3, T4, and T5 showed a significant decrease in Glu content, with the decrease being more pronounced in treatments T3, T4, and T5 compared to treatment T1. This indicates that treatments T3, T4, and T5, compared to treatment T1, help reduce Glu content in tobacco leaves, thereby preventing NH4+ depletion in tobacco plants. + Accumulated poisoning.

[0166] 2.3) Effects of different fertilization treatments on soil enzyme activity in tobacco-growing areas under potted conditions

[0167] 2.3.1) Effects of different fertilization treatments on soil enzyme activity in tobacco-growing areas under potted conditions

[0168] 2.3.1.1) The effects of different fertilization treatments on soil urease (S-UE) are shown in Table 13.

[0169] Table 13 Soil urease levels during the growing season

[0170]

[0171] Table 13 shows that 50 days after transplanting, the soil urease (S-UE) activities of treatments T2, T3, T4, and T5 were significantly higher than those of treatment T1, by 83.37%, 141.95%, 150.93%, and 155.03%, respectively. From 50 to 65 days after transplanting, the S-UE activities of treatments T1, T3, T4, and T5 remained relatively stable, with a slight decrease. At 65 days after transplanting, the S-UE activities of treatments T2, T3, T4, and T5 were significantly higher than those of treatment T1, by 21.74%, 129.75%, 126.91%, and 120.44%, respectively. At 80 days after transplanting, there was no significant difference in S-UE enzyme activity in treatment T2, while the S-UE activities of treatments T3, T4, and T5 were significantly higher than those of treatment T1, by 52.74%, 44.06%, and 61.48%, respectively. This indicates that compared to the T1 treatment, the T2, T3, T4, and T5 treatments were beneficial to improving the S-UE activity of tobacco plants, while the CK treatment was not beneficial to improving the S-UE activity of tobacco plants.

[0172] 2.3.1.2) The effects of different fertilization treatments on soil sucrase (S-SC) are shown in Table 14.

[0173] Table 14 Soil Sucrosease Table during Growth Period

[0174]

[0175] Table 14 shows that within 50-65 days after transplanting, the activity of soil sucrase (S-SC) in CK, T1, and T2 treatments remained relatively stable and slightly increased; the activity of S-SC in T3 treatment continued to decrease, showing a downward trend; the activity of S-SC in T4 treatment first increased and then decreased, but the overall activity showed an upward trend; and the activity of S-SC in T5 treatment first decreased and then increased, showing an upward trend. At 50 days post-transplanting, there was no significant difference in S-SC enzyme activity among the T2 treatments, while the S-SC enzyme activities of the T3, T4, and T5 treatments were significantly higher than those of the T1 treatment, by 215.69%, 276.94%, and 249.25%, respectively. At 65 days post-transplanting, there was no significant difference in S-SC enzyme activity among the T2 treatments, while the S-SC enzyme activities of the T3, T4, and T5 treatments were significantly higher than those of the T1 treatment, by 71.24%, 452.82%, and 159.81%, respectively. At 80 days post-transplanting, there was no significant difference in S-SC enzyme activity among the T2 treatments, while the S-SC enzyme activities of the T3, T4, and T5 treatments were significantly higher than those of the T1 treatment, by 183.36%, 289.65%, and 277.46%, respectively. This indicates that compared to the T1 treatment, the T3, T4, and T5 treatments were more conducive to improving the S-SC activity of tobacco plants.

[0176] 2.3.1. 3) The effects of different fertilization treatments on soil catalase (S-CAT) are shown in Table 15.

[0177] Table 15 Soil catalase levels during the growing season

[0178]

[0179] Table 15 shows that at 50 and 65 days after transplanting, there were no significant differences in soil catalase (S-CAT) activity among the treatments. At 80 days after transplanting, there was no significant difference in S-CAT activity among the T2 treatments, while the S-CAT activities of the T3, T4, and T5 treatments were significantly higher than those of the T1 treatment, by 1.24%, 2.14%, and 2.25%, respectively. The significant differences in soil catalase activity among the treatment groups only appeared in the later stages of growth and development, indicating that the T3, T4, and T5 treatments were beneficial in increasing the S-CAT activity in the soil, while the CK and T2 treatments were not beneficial in increasing the S-CAT activity in the soil.

[0180] 2.3.1.4) The effects of different fertilization treatments on soil acid phosphatase (S-ACP) are shown in Table 16.

[0181] Table 16 Soil acid phosphatase table during the growing season

[0182]

[0183] As shown in Table 16, at 50 days after transplanting, there was no significant difference in soil acid phosphatase (S-ACP) activity among treatments T2. The S-ACP activities of treatments T3, T4, and T5 were significantly higher than those of treatment T1, by 77.23%, 95.37%, and 51.91%, respectively. At 65 days after transplanting, there was no significant difference in S-ACP activity among treatments T4. The S-ACP activity of treatment T2 was significantly lower than that of treatment T1, by 15.33%. The S-ACP activities of treatments T3 and T5 were significantly higher than those of treatment T1, by 25.98% and 111.34%, respectively. At 80 days after transplanting, there was no significant difference in S-ACP activity among treatments T2. The S-ACP activities of treatments T3, T4, and T5 were significantly higher than those of treatment T1, by 26.45%, 55.19%, and 84.63%, respectively. This indicates that there are significant differences in S-ACP enzyme activity among different treatment groups at different growth stages, with the T3, T4, and T5 treatment groups being beneficial in increasing S-ACP activity in the soil.

[0184] 2.3.2) Effects of different fertilization treatments on soil nutrients in tobacco-growing areas

[0185] As shown in Figure 12(a), at 50 days post-transplantation, there were significant differences in the hydrolyzable nitrogen content in the soil among the treatment groups. The hydrolyzable nitrogen content in treatment T2 was significantly lower than that in treatment T1, by 24.1%. The hydrolyzable nitrogen contents in treatments T3, T4, and T5 were all significantly higher than those in treatment T1, by 34.78%, 36.17%, and 49.57%, respectively. At 65 days post-transplantation, the hydrolyzable nitrogen contents in treatments T2, T3, T4, and T5 were all significantly higher than those in treatment T1, by 7.75%, 32.9%, 72.63%, and 45.55%, respectively. At 80 days post-transplantation, the hydrolyzable nitrogen contents in treatments T2, T3, T4, and T5 were all significantly higher than those in treatment T1, by 11.41%, 24.53%, 45.91%, and 63.1%, respectively. Within 50-80 days after transplanting, the hydrolyzable nitrogen content in the soil of T1 and T3 treatments generally showed a decreasing trend, while the hydrolyzable nitrogen content in the soil of CK, T2, T4 and T5 treatment groups all showed an increasing trend.

[0186] As shown in Figure 12(b), at 50 days post-transplantation, there were no significant differences in available potassium content among treatments T3, T4, and T5. Treatment T2 had a significantly lower available potassium content than treatment T1, by 55.76%. At 65 days post-transplantation, treatment T2 still had a significantly lower available potassium content than treatment T1, by 53.57%, while treatments T3, T4, and T5 all had significantly higher available potassium content than treatment T1, by 35.78%, 55.76%, and 42.48%, respectively. At 80 days post-transplantation, there were no significant differences in available potassium content among treatments T3, T4, and T5, but treatment T2 had a significantly lower available potassium content than treatment T1, by 60.85%. As shown in Figure 12(c), at 50 days post-transplantation, there was no significant difference in organic matter content among treatments T2, while the organic matter content of treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 123.77%, 122.48%, and 98.38%, respectively. At 65 days post-transplantation, the organic matter content of treatments T2, T3, T4, and T5 was significantly higher than that of treatment T1, by 33.55%, 72.71%, 83.2%, and 74.76%, respectively. At 80 days post-transplantation, the organic matter content of treatments T2, T3, T4, and T5 was significantly higher than that of treatment T1, by 31.12%, 41.29%, 69.55%, and 83.35%, respectively. As shown in Figure 12(d), at 50 days post-transplantation, there was no significant difference in available phosphorus content among treatments T3, T4, and T5, while the available phosphorus content of treatment T2 was significantly lower than that of treatment T1, by 76.07%. At 65 days post-transplanting, there was no significant difference in available phosphorus content between treatments T4 and T5. The available phosphorus content in treatments T2 and T3 was lower than that in treatment T1, by 73.17% and 45.09%, respectively. At 80 days post-transplanting, the available phosphorus content in treatments T4 and T5 was higher than that in treatment T1, by 17.9% and 35.7%, respectively. The available phosphorus content in treatments T2 and T3 was lower than that in treatment T1, by 73.93% and 38.76%, respectively.

[0187] In summary, the differences in soil nutrient content in each treatment shown in Figure 12 were initially apparent 50 days after transplanting. Treatments T3, T4, and T5 had a very positive effect on the accumulation of soil nutrients during tobacco plant growth, which could increase soil nutrient content and contribute to the growth and development of tobacco plants.

[0188] 2.4) Correlation Analysis

[0189] 2.4.1) Correlation analysis between nutrient absorption and the physiological and biochemical properties of tobacco plants, as shown in Table 17.

[0190] Table 17 Correlation analysis of nutrient uptake with tobacco enzyme activity, metabolites, and chlorophyll.

[0191]

[0192] Note: "*" indicates a significant difference at the 0.05 level, and "**" indicates an extremely significant difference at the 0.01 level.

[0193] As shown in Table 17, 50 days after transplanting, nitrogen uptake was positively correlated with the activities of NR, GS, and SPS enzymes in tobacco leaves, with correlation coefficients of 0.786, 0.634, and 0.426, respectively, but these correlations were not statistically significant. Nitrogen uptake was negatively correlated with SS enzyme activity in tobacco leaves, with a correlation coefficient of -0.961, which was statistically significant (P < 0.01). Phosphorus uptake was positively correlated with the activities of NR, GS, and SPS enzymes in tobacco leaves, with correlation coefficients of 0.667, 0.397, and 0.24, respectively. The correlation coefficients were 0.01, but not statistically significant. Phosphorus uptake was negatively correlated with SS enzyme activity in tobacco leaves, with a correlation coefficient of -0.946, which was statistically significant (P < 0.01). Potassium uptake was positively correlated with NR, GS, and SPS enzyme activities in tobacco leaves, with correlation coefficients of 0.676, 0.487, and 0.317, respectively, but not statistically significant. Potassium uptake was negatively correlated with SS enzyme activity in tobacco leaves, with a correlation coefficient of -0.952, which was statistically significant (P < 0.01). At 50 days post-transplantation, Glu content showed a positive correlation with nitrogen, phosphorus, and potassium uptake, with correlation coefficients of 0.730, 0.705, and 0.678, respectively, all of which were statistically significant (P < 0.01). Chlorophyll content also showed a positive correlation with nitrogen and potassium uptake, with correlation coefficients of 0.695 and 0.608, respectively, all of which were statistically significant (P < 0.01). Furthermore, chlorophyll content showed a positive correlation with phosphorus uptake, with a correlation coefficient of 0.571, which was statistically significant (P < 0.05). At 65 days post-transplanting, nitrogen uptake showed a positive correlation with the activities of NR, GS, and SPS enzymes in tobacco leaves, with correlation coefficients of 0.470, 0.699, and 0.488, respectively, but these correlations were not statistically significant. Conversely, nitrogen uptake showed a negative correlation with SS enzyme activity in tobacco leaves, with a correlation coefficient of -0.697, which was statistically significant (P < 0.01). Phosphorus uptake also showed a positive correlation with the activities of NR, GS, and SPS enzymes in tobacco leaves, with correlation coefficients of 0.319, 0.690, and 0.643, respectively. The correlation between phosphorus uptake and SS enzyme activity in tobacco leaves was negative, with a correlation coefficient of -0.634, which was statistically significant (P < 0.01). The correlation between potassium uptake and NR, GS, and SPS enzyme activities in tobacco leaves was positive, with correlation coefficients of 0.469, 0.704, and 0.478, respectively, but it was not statistically significant. The correlation between potassium uptake and SS enzyme activity in tobacco leaves was negative, with a correlation coefficient of -0.721, which was statistically significant (P < 0.01).At 65 days post-transplantation, Glu content showed a negative correlation with nitrogen, phosphorus, and potassium uptake, with correlation coefficients of -0.001, -0.220, and -0.191, respectively, a significant decrease compared to 50 days post-transplantation. Chlorophyll showed a strong positive correlation with nitrogen, phosphorus, and potassium uptake. Chlorophyll was positively correlated with nitrogen and potassium uptake, with correlation coefficients of 0.695 and 0.608, respectively, reaching a significant level (P < 0.01), and also showed a positive correlation with phosphorus uptake, with a correlation coefficient of 0.571, reaching a significant level (P < 0.05). At 80 days post-transplanting, nitrogen uptake showed a positive correlation with the activities of NR, GS, SPS, and SS enzymes in tobacco leaves, with correlation coefficients of 0.966, 0.351, 0.633, and 0.570, respectively. However, only the correlation between nitrogen uptake and SS enzyme activity reached a significant level (P < 0.01). Phosphorus uptake also showed a positive correlation with the activities of NR, GS, SPS, and SS enzymes in tobacco leaves, with correlation coefficients of 0.965, 0.464, 0.640, and 0.6692, respectively. However, only the correlation between phosphorus uptake and SS enzyme activity reached a significant level (P < 0.01). Potassium uptake also showed a positive correlation with the activities of NR, GS, SPS, and SS enzymes in tobacco leaves, with correlation coefficients of 0.878, 0.562, 0.668, and 0.761, respectively, and all of these correlations reached a significant level (P < 0.01). Eighty days after transplanting, Glu content showed a negative correlation with nitrogen, phosphorus, and potassium uptake, with correlation coefficients of -0.108, -0.422, and -0.255, respectively, which were not statistically significant. Chlorophyll, on the other hand, still showed a strong positive correlation with nitrogen, phosphorus, and potassium uptake, with correlation coefficients of 0.653, 0.513, and 0.564, respectively. Chlorophyll was statistically significantly correlated with nitrogen uptake (P < 0.01), and with phosphorus and potassium uptake (P < 0.05).

[0194] In summary, the correlation between nutrient uptake and tobacco enzyme activity was weak in the early growth stage, while both nutrient uptake and NR enzyme activity showed a positive correlation, which became stronger and more significant at 80 days after transplanting (P < 0.01). In the later growth stage, the correlation between nutrient uptake and tobacco enzyme activity gradually increased. Nitrogen, phosphorus, and potassium uptake showed a negative correlation with SS enzyme activity at 50 and 65 days after transplanting, reaching a significant correlation at 50 days (P < 0.01), and a positive correlation at 80 days after transplanting. Nutrient uptake consistently showed a positive correlation with GS and SPS. Nutrient uptake and chlorophyll content consistently showed a strong positive correlation throughout the growth period. Glu content showed a strong positive correlation with nitrogen, phosphorus, and potassium uptake in the early growth stage, but this correlation gradually weakened and eventually became negative as the growth stage progressed.

[0195] 2.4.2) Correlation analysis of soil enzyme activity and soil nutrients under different fertilization treatments, as shown in Table 18.

[0196] Table 18 Correlation Analysis of Soil Enzyme Activity and Soil Nutrients

[0197]

[0198] Note: "*" indicates a significant difference at the 0.05 level, and "**" indicates an extremely significant difference at the 0.01 level.

[0199] As shown in Table 18, 50 days after transplanting, S-UE enzyme activity showed a positive correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in the soil, with correlation coefficients of 0.843, 0.683, 0.935, and 0.672, respectively. S-UE enzyme activity showed a significant correlation with hydrolyzable nitrogen (P < 0.05) and organic matter (P < 0.01). S-SC enzyme activity showed a negative correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in the soil, with correlation coefficients of -0.960, -0.788, -0.955, and -0.839, respectively. Among these, S-SC enzyme activity showed a significant correlation with the contents of hydrolyzable nitrogen and organic matter. The activity of S-CAT enzyme was significantly correlated with the content of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in tobacco-growing soil (P < 0.01). The S-CAT enzyme activity was positively correlated with the content of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in tobacco-growing soil, with correlation coefficients of 0.563, 0.136, 0.495, and 0.434, respectively, but none of them reached a significant level. The S-CAP enzyme activity was positively correlated with the content of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in soil, with correlation coefficients of 0.877, 0.876, 0.925, and 0.776, respectively. Among them, the S-CAP enzyme activity was significantly correlated with hydrolyzable nitrogen and available potassium (P < 0.05) and significantly correlated with organic matter (P < 0.01). Sixty-five days after transplanting, S-UE enzyme activity showed a positive correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in the tobacco-growing soil, with correlation coefficients of 0.918, 0.890, 0.979, and 0.531, respectively. S-UE enzyme activity was significantly correlated with hydrolyzable nitrogen and organic matter (P < 0.01) and with available potassium (P < 0.05). S-SC enzyme activity was also significantly correlated with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in the tobacco-growing soil. Organic matter and available phosphorus content showed negative correlations, with correlation coefficients of -0.732, -0.835, -0.847, and -0.445, respectively. S-SC enzyme activity was significantly correlated with available potassium and organic matter (P < 0.05). S-CAT enzyme activity showed positive correlations with hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus content in tobacco-growing soil, with correlation coefficients of 0.939, 0.790, 0.961, and 0.488, respectively. S-CAT enzyme activity was significantly correlated with hydrolyzable nitrogen and organic matter (P < 0.01). S-ACP enzyme activity showed positive correlations with hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus content in tobacco-growing soil, with correlation coefficients of 0.584, 0.698, 0.648, and 0.503, respectively, but did not reach a significant level.Eighty days after transplanting, S-UE enzyme activity showed a positive correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in the tobacco-growing soil, with correlation coefficients of 0.927, 0.863, 0.894, and 0.702, respectively. Among these, S-UE enzyme activity showed a significant correlation with hydrolyzable nitrogen and available potassium (P < 0.01) and with organic matter (P < 0.05). S-SC enzyme activity showed a negative correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in the tobacco-growing soil, with correlation coefficients of -0.788, -0.816, -0.774, and -0.651, respectively. S-SC enzyme activity showed a significant correlation with available potassium (P < 0.05). S-CAT enzyme activity showed a positive correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in tobacco-growing soil, with correlation coefficients of 0.977, 0.865, 0.983, and 0.753, respectively. Among them, S-CAT enzyme activity was significantly correlated with hydrolyzable nitrogen and organic matter (P < 0.01) and with available potassium (P < 0.05). S-ACP enzyme activity also showed a positive correlation with the contents of hydrolyzable nitrogen, available potassium, organic matter, and available phosphorus in tobacco-growing soil, with correlation coefficients of 0.970, 0.721, 0.919, and 0.897, respectively. S-ACP enzyme activity was significantly correlated with hydrolyzable nitrogen, organic matter, and available phosphorus (P < 0.01).

[0200] In the early growth stage, the correlation between the activity of related enzymes in the soil and the nutrient content in the tobacco-growing soil was weak. In the later growth stage, the correlation between the nutrient content in the tobacco-growing soil and the enzyme activity in the soil reached a significant level and increased considerably. The activities of S-UE, S-CAT, and S-ACP enzymes were consistently positively correlated with the nutrient content in the tobacco-growing soil, while the activities of S-SC enzymes were consistently negatively correlated with the nutrient content in the tobacco-growing soil. This indicates that the activities of soil urease, soil catalase, and soil acid phosphatase are positively correlated with the accumulation of nutrients in the soil. The stronger the activity of these three enzymes, the more nutrients accumulate in the soil, which is beneficial to improving soil fertility, improving the soil environment, and thus benefiting the growth and development of plants.

[0201] 2.4.3) Correlation analysis of agronomic traits of tobacco plants at different stages under potted conditions and soil nutrient content, as shown in Table 19.

[0202] Table 19 Correlation Analysis of Soil Nutrient Content and Agronomic Traits

[0203]

[0204] Note: "*" indicates a significant difference at the 0.05 level, and "**" indicates an extremely significant difference at the 0.01 level.

[0205] Table 19 shows that 50 days after transplanting, pH was positively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of 0.480, 0.540, 0.594, and 0.197, respectively. pH was significantly correlated with plant height, stem circumference, and internode distance (P < 0.01). Organic matter was negatively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of -0.654, -0.583, -0.761, and -0.394, respectively. Organic matter was significantly correlated with plant height, stem circumference, and internode distance (P < 0.01), and significantly correlated with maximum leaf area (P < 0.05). Alkali-available nitrogen was negatively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of -0.157, 0, -0.308, and -0, respectively. The correlation coefficients were -0.440 and -0.415, with significant correlations observed with internode distance and maximum leaf area (P < 0.05). Available phosphorus was negatively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of -0.421, -0.551, -0.604, and -0.530, respectively. Significant correlations were observed with stem circumference, internode distance, and maximum leaf area (P < 0.01), and with plant height (P < 0.05). Available potassium was negatively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of -0.363, -0.380, -0.558, and -0.511, respectively. Significant correlations were observed with internode distance and maximum leaf area (P < 0.01), and with stem circumference and plant height (P < 0.05).Sixty-five days after transplanting, pH was positively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of 0.137, 0.209, 0.347, and 0.218, respectively, but none reached a statistically significant level. Organic matter was positively correlated with plant height and internode distance, with correlation coefficients of 0.368 and 0.066, respectively, with a statistically significant correlation with plant height (P < 0.05). Organic matter was negatively correlated with stem circumference and maximum leaf area, with correlation coefficients of -0.465 and -0.218, respectively, with a statistically significant correlation with stem circumference (P < 0.01). Alkali-available nitrogen was negatively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of -0.200, -0.065, and -0.029, respectively. The correlation coefficients were -0.072, which were not statistically significant. Available phosphorus showed a positive correlation with stem circumference and maximum leaf area, with correlation coefficients of 0.220 and 0.281, respectively, but were not statistically significant. Available phosphorus showed a negative correlation with plant height and internode distance, with correlation coefficients of -0.230 and -0.407, respectively, with a statistically significant correlation with internode distance (P < 0.05). Available potassium showed a negative correlation with plant height and internode distance, with correlation coefficients of -0.231 and -0.424, respectively, with a statistically significant correlation with internode distance (P < 0.06). Available potassium showed a positive correlation with stem circumference and maximum leaf area, with correlation coefficients of 0.310 and 0.404, respectively, with a statistically significant correlation with maximum leaf area (P < 0.05). Eighty days after transplanting, pH was positively correlated with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of 0.054, 0.150, 0.123, and 0.309, respectively, none of which were statistically significant. Organic matter was positively correlated with plant height and internode distance, with correlation coefficients of 0.278 and 0.054, respectively, none of which were statistically significant. Organic matter was negatively correlated with stem circumference and maximum leaf area, with correlation coefficients of -0.362 and -0.215, respectively, with the correlation with stem circumference being statistically significant (P < 0.05). Alkali-available nitrogen was positively correlated with plant height, with a correlation coefficient of 0.545, which was statistically significant (P < 0.01). Alkali-available nitrogen was also negatively correlated with stem circumference, internode distance, and maximum leaf area. Maximum leaf area showed a negative correlation with all three factors, with correlation coefficients of -0.453, -0.174, and -0.206, respectively, among which the correlation with stem circumference was significant (P < 0.05). Available phosphorus showed a positive correlation with plant height, stem circumference, internode distance, and maximum leaf area, with correlation coefficients of 0.524, 0.014, 0.027, and 0.089, respectively, among which the correlation with plant height was significant (P < 0.01). Available potassium showed a positive correlation with plant height, internode distance, and maximum leaf area, with correlation coefficients of 0.280, 0.098, and 0.202, respectively, but the correlation was not significant. Available potassium showed a negative correlation with stem circumference, with a correlation coefficient of -0.189, which was also not significant.Compared to the later stages of growth, soil nutrients and plant agronomic traits showed a stronger correlation in the early stages of growth, with most showing a significant correlation. 2.5) The effects of different fertilization treatments on soil microorganisms under potted conditions.

[0206] 2.5.1) Rhizosphere soil microbial alpha diversity

[0207] Alpha diversity refers to the diversity of species within a specific ecological environment or ecosystem.

[0208] Table 20. Rhizosphere Soil Microbial Community Alpha Diversity Index

[0209]

[0210] Table 20 shows that at the microbial level, the Chao indices of treatments T3, T4, and T5 did not differ significantly, indicating relatively stable performance and demonstrating the accuracy and reliability of the sequencing results. Coverage represents the OUT abundance coverage of the samples; this index was 100% in all four groups, indicating that the sequencing depth was sufficient to reflect the true soil microbial community structure and meet the requirements for subsequent analysis. The Chao index reflects the species richness in the samples; a larger index indicates a greater number of species in the microbial community and a higher microbial community richness. The Chao indices of treatments T3, T4, and T5 were significantly higher than that of treatment T1, indicating that the microbial communities of treatments T3, T4, and T5 were richer and had a greater number of species compared to treatment T1. The Shannon and Simpson indices indicate species richness and evenness. A larger Shannon index indicates greater species richness and a more even distribution of species, while a smaller Simpson index indicates higher species evenness. Treatment T3 had the largest Shannon index and the smallest Simpson index, indicating that treatment T3 had the highest species richness and the highest evenness.

[0211] 2.5.2) Soil microbial Beta diversity analysis

[0212] Figure 14 shows the principal coordinate analysis (PCoA) of rhizosphere soil microbial communities under different fertilization treatments based on Bray-curtis. At 80 days post-transplantation, the contributions of the PC1 and PC2 axes to the differences in sample composition were 31.37% and 15.21%, respectively. Treatment T1 was located in the second and third quadrants, treatments T3 and T4 in the first and fourth quadrants, and treatment T5 in the first, third, and fourth quadrants. The microbial communities of treatments T3, T4, and T5 were more distant from those of treatment T1, indicating significant differences in the communities. Within treatments T3 and T5, there were also significant differences. Different fertilization treatments were concentrated in the fourth quadrant and near the midpoint, showing relatively small differences in the communities. Compared to single fertilization, different fertilization treatments led to changes in the microbial community.

[0213] 2.5.3) KEGG Function Comments

[0214] KEGG functional annotation categorizes primary pathways into six main classes: Metabolism, Cellular Processes, Human Diseases, Organic Systems, Genetic Information Processing, and Environmental Information Processing. Of the 15,969 functional genes obtained from the KEGG database, 441 metabolic pathways were annotated, including 502 enzyme genes involved in the reactions. In Figure 15, the bottom and right sides of the heatmap represent the sample name and function name, respectively, with the color intensity indicating the abundance of the function.

[0215] As shown in Figure 15, under potted conditions, the functional differences between treatments T3, T4, and T5 and treatment T1 were significant throughout the entire growth period. Particularly, the differences were strong in tryptophan metabolism, C5-branched dibasic acid metabolism, pentose and glucuronate interconversions, and fructose and mannose metabolism. This indicates that in the later stages of transplanting, the microbial functions under treatment T1 differed significantly from those under treatments T3, T4, and T5. Treatments T3, T4, and T5 demonstrated stronger microbial functions than treatment T1 in amino acid synthesis, fructose and mannose metabolism, and the interconversion of pentose and glucuronate. Compared to different fertilization treatments, the application of a single fertilizer type was detrimental to the later growth of tobacco plants.

[0216] Figure 15 shows the biosynthesis of phenylalanine, tyrosine, and tryptophan, the metabolism of amino sugars and nucleotide sugars, the biosynthesis of extracellular polysaccharides, and tryptophan metabolism, all of which have relatively high functional abundance. These are important processes involved in carbon and nitrogen metabolism. Compared to single fertilization, different fertilization treatments can effectively improve soil microbial diversity and the functional strength of soil microbial communities, thereby promoting microbial activity and improving soil carbon and nitrogen metabolism efficiency.

[0217] 3.1) Effects of different fertilization treatments on the growth and development of tobacco plants at different growth stages under field conditions

[0218] 3.1.1) The effects of different fertilization treatments on the agronomic traits of tobacco plants at different growth stages are shown in Table 21.

[0219] Table 21 Effects of the growing season on agronomic traits of flue-cured tobacco

[0220]

[0221] Table 21 shows that 72 days after transplanting, the plant height of treatments T2 and T3 was significantly lower than that of treatment T1, by 1.61% and 2.37% respectively; the plant height of treatment T4 was significantly higher than that of treatment T1, by 10.43%; and the plant height of treatment T5 was not significantly different from that of treatment T1. The stem circumference of treatment T2 was significantly lower than that of treatment T1, by 4.29%; the stem circumference of treatment T3 was not significantly different from that of treatment T1; and the stem circumference of treatments T4 and T5 were significantly higher than that of treatment T1, by 3.71% and 2.57% respectively. Compared with treatment T1, there were no significant differences in internode distance among treatments T2, T3, T4, and T5. Compared with treatment T1, there were no significant differences in maximum leaf area among treatments T2, T3, T4, and T5. At 90 days post-transplanting, the plant height of treatments T2, T3, T4, and T5 was significantly higher than that of treatment T1, by 6.03%, 1.35%, 6.59%, and 2.98%, respectively. There was no significant difference in stem circumference between treatments T3 and T4, while the stem circumference of treatments T2 and T5 was significantly higher than that of treatment T1, by 0.66% and 2.08%, respectively. There was no significant difference in stem circumference among treatments T3, T4, and T5, but the internode distance in treatment T2 was significantly higher than that in treatment T1, by 0.58%. The maximum leaf area of ​​treatments T2, T3, T4, and T5 was significantly lower than that of treatment T1, by 28.49%, 22.12%, 9.95%, and 16.44%, respectively. At 108 days post-transplanting, the plant height of treatments T2, T3, T4, and T5 was significantly lower than that of treatment T1, by 4.79%, 3.06%, 1.56%, and 1.17%, respectively. Compared with treatment T1, there were no significant differences in stem circumference among treatments T2, T3, T4, and T5. Plant height was significantly lower in treatments T2, T3, T4, and T5 than in treatment T1, by 4.8%, 1.78%, 2.14%, and 1.6%, respectively. Maximum leaf area was significantly lower in treatment T2 than in treatment T1, by 2.87%. Maximum leaf area was significantly higher in treatments T3 and T4 than in treatment T1, by 2.14% and 2.17%, respectively. Maximum leaf area was not significantly different between treatment T5 and treatment T1.

[0222] Under field conditions, the T2 treatment was detrimental to the later growth and leaf expansion of tobacco plants, while the T3, T4, and T5 treatments could effectively improve the agronomic traits of flue-cured tobacco. In the later stages of growth, the T3, T4, and T5 treatments were more conducive to leaf expansion than the T1 treatment, which is consistent with the results of pot experiments.

[0223] 3.1.2) Effects of different fertilization treatments on nutrient absorption in tobacco plants

[0224] As shown in Figure 13(a), 72 days after transplanting, the nitrogen uptake of treatments T2, T3, T4, and T5 was significantly higher than that of treatment T1, by 30.53%, 32.54%, 18.17%, and 49.97%, respectively. At 108 days after transplanting, there was no significant difference in nitrogen uptake among treatments T2, T3, T4, and T5. As shown in Figure 13(b), 72 days after transplanting, the potassium uptake of treatments T2, T3, T4, and T5 was significantly higher than that of treatment T1, by 29.92%, 33.96%, 24.08%, and 49.48%, respectively. At 108 days after transplanting, there was no significant difference in potassium uptake among treatments T2, T3, T4, and T5. This indicates that under field conditions, in the early growth stage, the nutrient uptake of treatments T2, T3, T4, and T5 differed significantly from that of treatment T1, but there was no significant difference in nutrient uptake in the later stages.

[0225] 3.2) Effects of different fertilization treatments on soil nutrients in tobacco-growing areas under field conditions

[0226] 3.2.1) The effects of different fertilization treatments on soil nutrient content are shown in Table 22.

[0227] Table 22 Effects of Soil Nutrient Content

[0228]

[0229] Table 22 shows that at 72 days after transplanting, the hydrolyzable nitrogen content in treatments T2, T3, T4, and T5 was significantly higher than that in treatment T1, by 53.18%, 42.62%, 58.13%, and 53.73%, respectively. At 108 days after transplanting, there was no significant difference in hydrolyzable nitrogen content among treatments T2, T3, and T4, while the hydrolyzable nitrogen content in treatment T5 was significantly lower than that in treatment T1, by 7.56%. During the 50-80 days after transplanting, except for treatments CK and T1, the hydrolyzable nitrogen content in all other treatments showed an increasing trend. At 72 days after transplanting, the available potassium content in treatments T2, T3, T4, and T5 was significantly higher than that in treatment T1, by 23.61%, 42.92%, 46.73%, and 58.81%, respectively. At 108 days post-transplantation, there were no significant differences in available potassium content among treatments T2, T3, and T4. However, treatment T5 showed a significantly higher available potassium content than treatment T1, exceeding it by 84.35%. During the period of 72-108 days post-transplantation, all treatment groups showed a decreasing trend in available potassium content, consistent with the results under potted plant conditions.

[0230] 3.3) Effects of different fertilization treatments on economic traits under field conditions

[0231] 3.3.1) The economic traits of tobacco plants in each treatment are shown in Table 23.

[0232] Table 23 Economic Traits of Tobacco Plants

[0233]

[0234] In Table 23, the yields of treatments T3 and T4 were significantly higher than those of treatment T1, by 8.72% and 9.54%, respectively; the output value of treatments T3, T4, and T5 was significantly higher than that of treatment T1, by 16.79%, 17.96%, and 12.35%, respectively; and the proportion of high-grade tobacco in treatments T3 and T4 was significantly higher than that in treatment T1, by 4.3797 and 5.4031 percentage points, respectively. Under field conditions, treatments T3, T4, and T5 can more effectively improve the economic traits of flue-cured tobacco, thereby achieving the goal of increasing yield and income in the field.

[0235] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A method for improving tobacco quality; characterized in that: The planting method is set to fertilization mode T3, T4, or T5. T3 fertilization mode involves applying fertilizer composed of compound fertilizer, straw, and potassium fertilizer. By weight, the compound fertilizer is 35-55 parts, straw 300-400 parts, and potassium fertilizer 6-10 parts. The compound fertilizer is tobacco-specific fertilizer with a N:P2O5:K2O ratio of 12:10:

24. The straw used is pea straw. The potassium fertilizer is agricultural-grade potassium sulfate with a K2SO4 content of 52%. The compound fertilizer is applied once before transplanting and twice after transplanting, while the potassium fertilizer is applied twice after transplanting. The straw is crushed and mixed into the soil before transplanting. 30% of the compound fertilizer added to each tobacco plant is applied as base fertilizer. Topdressing is applied on the 28th and 52nd days after transplanting. The first topdressing adds 35% of the compound fertilizer and 50% of the potassium sulfate, and the second topdressing adds... Add 35% of the compound fertilizer and 50% of the potassium sulfate. After transplanting, add potassium sulfate 2-3 hours after applying the compound fertilizer. Mix all pea straw into the soil 10 days before transplanting. Apply topdressing using a ring application method. The T4 fertilization method consists of compound fertilizer, straw, powdered soil conditioner, liquid soil conditioner, and potassium fertilizer. By weight, the amounts are: 35-55 parts compound fertilizer, 300-400 parts straw, 0.5-0.8 parts powdered soil conditioner, 0.5-0.8 parts liquid soil conditioner, and 6-10 parts potassium fertilizer. The compound fertilizer is a tobacco-specific fertilizer with a N:P2O5:K2O ratio of 12:10:

24. The straw used is pea straw. The potassium fertilizer is agricultural-grade potassium sulfate with a K2SO4 content of 52%. The total bacterial count in the powdered and liquid soil conditioners is ≥0.5 x 10⁻⁶. 3 The concentrations of N+, P2O5+, and K2O should be ≥6%. Compound fertilizer should be applied once before transplanting and twice after transplanting. Potassium fertilizer should be applied twice after transplanting. Straw should be crushed and mixed into the soil before transplanting. Powdered soil conditioner should be applied before and after transplanting. Liquid soil conditioner should be applied during the seedling stage, the crowning stage, and the vigorous growth stage. 30% of the compound fertilizer added to each tobacco plant should be applied as base fertilizer. Topdressing should be applied on the 28th and 52nd days after transplanting. The first topdressing should add 35% of the compound fertilizer added and 50% of the potassium sulfate added. The second topdressing should add 35% of the compound fertilizer added and 50% of the potassium sulfate added. After transplanting, potassium sulfate should be added 2-3 hours after the compound fertilizer application. Pea straw should be completely mixed into the soil 10 days before transplanting. Topdressing should be done using the ring application method. The powdered soil conditioner should be used at a rate of 0.6g per plant, with 0.3g used each time. The first application should be applied one day before transplanting, and the second application should be 15-20 days after the first application. The aqueous soil conditioner is added after the second application of the powdered soil conditioner, with an interval of 1-2 hours between the two applications. It is applied during the seedling stage, the crowning stage, and the vigorous growth stage, respectively. The T5 fertilization method consists of a compound fertilizer with 10% reduced nitrogen, straw, powdered soil conditioner, aqueous soil conditioner, and potassium fertilizer. The mass percentages are: 31.5-48.6 parts compound fertilizer, 300-400 parts straw, 0.5-0.8 parts powdered soil conditioner, and... The application rate is 0.5-0.8 parts of a good fertilizer and 6-10 parts of potassium fertilizer. The compound fertilizer with 10% nitrogen reduction is 90% of the amount applied in T4. The compound fertilizer used is a tobacco-specific fertilizer with a N:P₂O₅:K₂O ratio of 12:10:

24. Pea straw is used. Agricultural-grade potassium sulfate is used, with a K₂SO₄ content of 52%. The total bacterial count in both powder and liquid soil conditioners is ≥0.5 x 10⁻⁶. 3 The concentration of N+P2O5+K2O is ≥6%. Compound fertilizer is applied once before transplanting and twice after transplanting. Potassium fertilizer is applied twice after transplanting. Straw is crushed and mixed into the soil before transplanting. Powdered soil conditioner is applied before and after transplanting. Liquid soil conditioner is applied during the seedling stage, the crowning stage, and the vigorous growth stage. 30% of the compound fertilizer added to each tobacco plant is applied as base fertilizer. Topdressing is carried out on the 28th and 52nd days after transplanting. The first topdressing adds 35% of the compound fertilizer added and 50% of the potassium sulfate added. The second topdressing adds 35% of the compound fertilizer added and 50% of the potassium sulfate added. After transplanting, potassium sulfate is added 2-3 hours after the compound fertilizer is applied. Pea straw is mixed into the soil 10 days before transplanting. Topdressing is done by ring application. The soil conditioner powder is used at 0.6g per plant, 0.3g each time. The first application is one day before transplanting, and the second application is 15-20 days after the first application. The aqueous soil conditioner is added after the second application of the powder form, with an interval of 1-2 hours between the two applications. It is applied during the seedling stage, the crowning stage, and the vigorous growth stage, respectively.

2. The application of the method according to claim 1, characterized in that: The application employs a T3 fertilization method to increase the plant height, stem circumference, internode distance, and leaf area of ​​tobacco plants; and / or to increase the chlorophyll content in tobacco leaves; and / or to decrease the glutamate content of tobacco plants; and / or to increase the enzyme activity of sucrose phosphate synthase in tobacco plants; and / or to increase the enzyme activity of sucrose synthase in tobacco plants.

3. The application of the method according to claim 1, characterized in that: The application employs a T4 fertilization method to increase the plant height, stem circumference, internode distance, and leaf area of ​​tobacco plants; and / or to increase the chlorophyll content in tobacco leaves; and / or to decrease the glutamate content of tobacco plants; and / or to increase the enzyme activity of nitrate reductase in tobacco plants; and / or to increase the enzyme activity of glutamine synthase in tobacco plants; and / or to increase the enzyme activity of sucrose synthase in tobacco plants.

4. The application of the method according to claim 1, characterized in that: The application employs a T5 fertilization method to increase the plant height, stem circumference, internode distance, and leaf area of ​​tobacco plants; and / or to increase the chlorophyll content in tobacco leaves; and / or to decrease the glutamate content of tobacco plants; and / or to increase the enzyme activity of glutamine synthase in tobacco plants; and / or to increase the enzyme activity of sucrose phosphate synthase in tobacco plants; and / or to increase the enzyme activity of sucrose synthase in tobacco plants.

5. The application of the method described in claim 1 in improving soil fertility, characterized in that: The application employs a T3 fertilization method to increase the activity of soil urease, and / or the activity of soil sucrase, and / or the activity of soil catalase, and / or the activity of soil acid phosphatase, and / or the richness of soil microorganisms, and / or the evenness of soil microorganisms, and / or the diversity of soil microorganisms, and / or the functional strength of soil microbial communities.

6. The application of the method described in claim 1 in improving soil fertility, characterized in that: The application employs a T4 fertilization method to increase the activity of soil urease, and / or the activity of soil sucrase, and / or the activity of soil catalase, and / or the activity of soil acid phosphatase, and / or the richness of soil microorganisms, and / or the diversity of soil microorganisms, and / or the functional strength of soil microbial communities.

7. The application of the method according to claim 1 in improving soil fertility, characterized in that: The application employs a T5 fertilization method to increase the activity of soil urease, and / or the activity of soil sucrase, and / or the activity of soil catalase, and / or the activity of soil acid phosphatase, and / or the richness of soil microorganisms, and / or the diversity of soil microorganisms, and / or the functional strength of soil microbial communities.

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