Fertilizing method for improving yield and quality of tobacco in tobacco-potato rotation mode

Abstract

The invention discloses a fertilizing method for improving yield and quality of tobacco in a tobacco-potato rotation mode, aiming at soil nutrient characteristics after rotation, a rotation field with preceding crops being sweet potatoes is selected, soil physicochemical properties need to meet certain requirements, nitrogen (45-67.5 kg N / hm < 2 >), phosphorus (66-69 kg P2O5 / hm < 2 >) and potassium (135-202.5 kg K2O / hm < 2 >) are precisely applied, nitrogen fertilizer and potassium fertilizer are mixed and spread to furrows, the phosphorus fertilizer is singly applied to ridge bottoms in furrows, and the fertilizer is applied to the ridge bottoms in furrows. Transplanting is performed according to the line spacing of 1-1.5 m and the plant spacing of 0.4-0.6 m in the first ten days of May. According to the method, the tobacco yield, the output value and the middle-first-class tobacco proportion can be remarkably increased, agronomic characters and dry matter accumulation are optimized, chemical components of the tobacco leaves are coordinated, the potassium content is increased, the nutrient utilization rate is increased, cost is reduced, and the green agriculture concept is met.

Description

Technical Field

[0001] This invention relates to the field of agricultural fertilizer technology, specifically a fertilization method for improving tobacco yield and quality under a tobacco-potato rotation model. Background Technology

[0002] Tobacco is an important economic crop in my country, and its yield and quality directly affect farmers' income and the economic benefits of the producing areas. In actual cultivation, long-term continuous cropping can easily lead to soil nutrient imbalances, increased pests and diseases, and other obstacles, thus affecting the sustainable production of tobacco. Therefore, crop rotation is often adopted in production to mitigate the negative effects of continuous cropping, with tobacco and sweet potato rotation being a typical example. This model allows the two crops to complement each other in terms of nutrient utilization and soil structure improvement, helping to maintain the ecological balance of farmland.

[0003] However, even under crop rotation, improper fertilizer application, especially an inappropriate ratio of key nutrients such as nitrogen, potassium, and phosphorus, can still restrict the improvement of tobacco yield and quality. Nitrogen and potassium are key nutrients in the tobacco growth process, and their proper application plays an important role in tobacco yield formation and quality improvement; phosphorus is crucial for root development, energy metabolism, and early growth. Current research on tobacco fertilization mainly focuses on single crops or general soil conditions, lacking specific fertilization schemes tailored to the dynamic changes in soil nutrients under tobacco-sweet potato rotation systems. Due to differences in crop residues, root distribution, and nutrient absorption characteristics before and after rotation, the availability of nitrogen, phosphorus, and potassium in the soil and their supply capacity to tobacco will change significantly. Continuing to use conventional tobacco fertilization strategies often leads to a mismatch between nutrient supply and tobacco demand.

[0004] Specifically, excessive nitrogen fertilizer can lead to delayed maturity of tobacco leaves, excessively high nicotine content, and poor coordination of chemical components; insufficient nitrogen fertilizer, on the other hand, restricts yield formation. Insufficient potassium supply directly results in low potassium content in tobacco leaves, affecting combustibility and aroma quality, while also reducing plant resistance. Improper application of phosphorus fertilizer can affect early growth and root development in tobacco. Furthermore, the interactions between nitrogen, potassium, and phosphorus are significant; improper ratios can reduce fertilizer utilization, increase production costs, and are inconsistent with the development direction of green agriculture.

[0005] Therefore, there is an urgent need in this field for a dedicated fertilization method for the tobacco-sweet potato rotation pattern, which can precisely control the amount and ratio of nitrogen, phosphorus, and potassium according to the actual soil nutrient conditions under this rotation system, so as to achieve the production goals of high yield, high quality, and high efficiency of tobacco. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the problems of limited yield, reduced quality and low fertilizer utilization caused by unreasonable application of nitrogen, phosphorus and potassium fertilizers in the tobacco-sweet potato rotation mode in the prior art, and to provide a fertilization method that can significantly increase tobacco yield, improve tobacco leaf quality and promote efficient nutrient utilization.

[0007] To achieve the above objectives, the specific solution adopted by the present invention is as follows: A fertilization method for improving tobacco yield and quality under a tobacco-potato rotation pattern includes the following steps: Step 1: Select a rotation field where the previous crop was sweet potato, and the soil physicochemical properties meet the following requirements: pH 7.20-7.30, organic matter 12.00-12.80 g / kg, available nitrogen 58.00-60.00 mg / kg, available phosphorus 10.00-11.50 mg / kg, and available potassium 115.00-118.00 mg / kg; Step 2: Apply fertilizer to the field selected in Step 1. The fertilizer includes nitrogen, potassium, and phosphorus fertilizers; wherein, by pure amount, the application rate of nitrogen is 45-67.5 kg N / hm². 2 The potassium application rate is 135-202.5 kg K2O / hm. 2 The fertilizer is applied all at once after ridging. The nitrogen fertilizer and potassium fertilizer are mixed and spread in the furrows, and the phosphorus fertilizer is applied separately in strips at the bottom of the ridges. Step 3: Transplant the tobacco seedlings to the fertilized field in early May, with a row spacing of 1-1.5m and a plant spacing of 0.4-0.6m.

[0008] Furthermore, the nitrogen fertilizer is calcium ammonium nitrate, and the potassium fertilizer is potassium sulfate.

[0009] Furthermore, in step one, the soil physicochemical properties meet the following requirements: pH 7.25, organic matter 12.37 g / kg, available nitrogen 59.03 mg / kg, available phosphorus 10.86 mg / kg, and available potassium 116.32 mg / kg.

[0010] Furthermore, in step two, the amount of phosphorus applied is 66-69 kg P2O5 / hm. 2 .

[0011] Furthermore, in step two, the phosphate fertilizer is superphosphate.

[0012] Furthermore, the nitrogen application rate is 45 kg N / hm². 2 The potassium application rate is 202.5 kg K₂O / hm. 2 .

[0013] Beneficial effects: (1) This invention optimizes the nitrogen and potassium application ratio based on the soil nutrient characteristics after tobacco-sweet potato rotation. Experiments show that this method can significantly increase tobacco yield, output value, proportion of medium and high grade tobacco, and average price, resulting in a significant improvement in economic benefits.

[0014] (2) The compounding method of the present invention makes the chemical composition of the flue-cured tobacco leaves more coordinated, significantly increases the potassium content, and the total nitrogen, nicotine and chloride ion contents are all within the suitable range for high-quality tobacco leaves. The nitrogen-alkali ratio, sugar-alkali ratio and potassium-chlorine ratio are coordinated, which comprehensively improves the internal quality and taste of the tobacco leaves.

[0015] (3) The method of the present invention can effectively promote the optimization of tobacco agronomic traits, improve indicators such as plant height, stem circumference, number of effective leaves and leaf area index, and significantly increase the amount of dry matter accumulation, which is evenly distributed in all parts, laying a material foundation for high yield.

[0016] (4) By precisely applying nitrogen, phosphorus and potassium, this invention improves the efficiency of tobacco in nutrient absorption and utilization, reduces fertilizer waste, lowers environmental risks and planting costs, and is in line with the concept of green agriculture and sustainable development. Attached Figure Description

[0017] Figure 1 A statistical chart showing the total nitrogen content of flue-cured tobacco leaves under different nitrogen and potassium application ratios.

[0018] Figure 2 A statistical chart showing the nicotine content of flue-cured tobacco leaves under different nitrogen and potassium application ratios.

[0019] Figure 3 A statistical chart showing the potassium content of flue-cured tobacco leaves under different nitrogen and potassium application ratios.

[0020] Figure 4 A statistical chart showing the chlorine content in different parts of flue-cured tobacco leaves under different nitrogen and potassium application ratios.

[0021] Figure 5 A statistical chart showing the total sugar content of different parts of flue-cured tobacco leaves under different nitrogen and potassium application ratios.

[0022] Figure 6 A statistical chart showing the reducing sugar content in different parts of flue-cured tobacco leaves under different nitrogen and potassium application ratios.

[0023] Figure 7 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0024] This invention provides a fertilization method for improving tobacco yield and quality under a tobacco-potato rotation system. Please refer to [reference needed]. Figure 7 The detailed technical solution includes the following steps: Step 1: Field Selection Select rotation fields where the previous crop was sweet potato. The soil physicochemical properties of the selected fields must meet specific ranges: pH value between 7.20 and 7.30, organic matter content between 12.00 and 12.80 g / kg, available nitrogen content between 58.00 and 60.00 mg / kg, available phosphorus content between 10.00 and 11.50 mg / kg, and available potassium content between 115.00 and 118.00 mg / kg. Preferably, the soil physicochemical properties are: pH 7.25, organic matter 12.37 g / kg, available nitrogen 59.03 mg / kg, available phosphorus 10.86 mg / kg, and available potassium 116.32 mg / kg.

[0025] Function Explanation: This step is fundamental to ensuring the effectiveness of the fertilization program. After tobacco-sweet potato rotation, the soil pH and basic fertility (organic matter, available nitrogen, available phosphorus, and available potassium) are in a relatively stable state. The soil index ranges determined in this invention are verified to be suitable soil conditions that optimize the subsequent application of nitrogen, phosphorus, and potassium. Soil pH affects nutrient availability; organic matter is the core of soil fertility; specific ranges of available nitrogen, available phosphorus, and available potassium reflect the soil's nitrogen, phosphorus, and potassium supply levels after rotation. Precise fertilization based on these ranges can avoid nutrient over- or under-nutrients.

[0026] Step 2: Fertilizer Application Select suitable fields for application of nitrogen, potassium, and phosphorus fertilizers. Specific application rates are based on pure nutrient content: nitrogen (N) application rates range from 45-67.5 kg / hm². 2 The application rate of potassium (calculated as K2O) ranges from 135 to 202.5 kg / hm². 2 The application rate of phosphorus (calculated as P2O5) ranges from 66 to 69 kg / hm. 2 (Preferred 67.5 kg / hm) 2 The recommended nitrogen fertilizer is calcium ammonium nitrate (15% N), the potassium fertilizer is potassium sulfate (52% K2O), and the phosphate fertilizer is superphosphate (12% P2O5). All fertilizers should be applied all at once after ridging is completed in the field. Specifically, the calculated amounts of nitrogen and potassium fertilizers should be mixed evenly and then spread in the furrows; the phosphate fertilizer should be applied separately in strips at the bottom of the ridges.

[0027] Functional explanation: This step is the core of the invention, providing the key nutrients required for tobacco growth and optimizing the application method.

[0028] Dosage and Ratio: Nitrogen and potassium application rates are controlled within the aforementioned ranges, forming a specific ratio (e.g., nitrogen:potassium oxide ratio approximately 1:3 to 1:4.5). This is based on research findings regarding soil nutrient status after crop rotation and the nutrient requirements of tobacco. This ratio effectively coordinates the vegetative and reproductive growth of tobacco, promoting yield formation and quality improvement. Phosphate fertilizer application is determined according to soil phosphorus levels and tobacco requirements to ensure early growth and root development.

[0029] Fertilization methods and timing: "Applying fertilizer all at once after ridging" simplifies agricultural operations. "Mixing nitrogen and potassium fertilizers and spreading them in the furrows" facilitates the even diffusion and supply of these two relatively mobile nutrients in the main distribution area of ​​tobacco roots (the ridge). "Applying phosphate fertilizer separately in strips at the bottom of the ridges" is because phosphorus has poor mobility in the soil; strip application allows for relatively concentrated supply, reduces contact and fixation with the soil, and improves the utilization rate of phosphate fertilizer in the current season.

[0030] Step 3: Transplanting tobacco seedlings In early May, tobacco seedlings were transplanted into fields where fertilization had been completed. A reasonable plant population structure was maintained during transplanting, with row spacing controlled at 1-1.5 meters (e.g., 1.3 meters) and plant spacing controlled at 0.4-0.6 meters (e.g., 0.5 meters).

[0031] Function Explanation: This step is a crucial agronomic link connecting fertilization and tobacco growth. Transplanting in early May is chosen to match the tobacco's growth process with local light and temperature conditions, making full use of the growing season. The planting density configuration of "row spacing of 1-1.5m and plant spacing of 0.4-0.6m" provides reasonable growing space and ventilation and light penetration for the tobacco plants, which is conducive to building an efficient photosynthetic community, reducing the occurrence of pests and diseases, and laying a good field structure foundation for ultimately achieving high yield and quality.

[0032] The systematic implementation of the above three steps constitutes the complete fertilization method of this invention. This method, tailored to the soil nutrient variation characteristics of the tobacco-sweet potato rotation pattern, achieves precise nutrient management throughout the entire tobacco growth process by selecting suitable fields, optimizing nitrogen, phosphorus, and potassium application rates and ratios, improving fertilization methods, and providing appropriate transplanting support. This results in a comprehensive goal of increasing yield, improving quality, and achieving cost savings.

[0033] The technical solutions in the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Examples 1-4 and Comparative Examples 1-5 This experiment was conducted as a demonstration application in tobacco-sweet potato rotation fields in western Henan Province. Four exemplary cases (conforming to the nitrogen and potassium application range specified in the invention) and five comparative cases (deviating from the nitrogen and potassium application range specified in the invention) were set up, as detailed below: Overview of the test site: The experimental field was located in the hilly area of ​​western Henan Province, with an average altitude of approximately 460 meters. The soil type was brown soil, and the previous crop was sweet potato. Prior to the experiment, the basic physicochemical properties of the soil were measured as follows: pH 7.25, organic matter content 12.37 g / kg, available nitrogen 59.03 mg / kg, available phosphorus 10.86 mg / kg, and available potassium 116.32 mg / kg. These soil conditions met the requirements of step one of this invention.

[0035] Test materials: The tobacco variety was 'LY1306'. The tested fertilizers were calcium ammonium nitrate (N content 15%), potassium sulfate (K2O content 52%), and superphosphate (P2O5 content 12%).

[0036] Implementation steps (1) Field preparation and fertilization: After ridging, apply fertilizer once according to the method of this invention. Set the phosphate fertilizer application rate to 67.5 kg P2O5 / hm. 2 Nitrogen fertilizer (calcium ammonium nitrate) and potassium fertilizer (potassium sulfate) were applied at different levels, with the example group meeting the requirement of "nitrogen 45-67.5 kg N / hm²". 2 Potassium 135-202.5 kg K2O / hm 2 The comparative groups deviated from this range. The specific dosages of Examples 1-4 and Comparative Examples 1-5 are shown in Table 1 below. When fertilizing, the calculated nitrogen and potassium fertilizers were mixed evenly and spread in the furrows; the phosphorus fertilizer was applied separately in strips at the bottom of the ridges. (2) Field design: Each treatment plot has an area of ​​52m². 2 (13m × 4.0m), 80 tobacco plants were planted, with a row spacing of 1.3m and a plant spacing of 0.5m. Each treatment was replicated 3 times; (3) Transplanting and management: In early May, the tobacco seedlings were transplanted to the fertilized fields, and field management was carried out in accordance with the local high-quality tobacco production standards.

[0037] Table 1. Nitrogen and potassium combined application treatments in Examples 1-4 and Comparative Examples 1-5 By planting tobacco in the above four examples and five comparative examples, the tobacco parameters of each treatment were measured, and the effects of the nitrogen and potassium application ranges specified in the invention on tobacco yield, quality, agronomic traits and dry matter accumulation were analyzed to verify the optimal technical solution.

[0038] After implementing the above methods, the yield and economic traits of tobacco, the chemical composition of tobacco leaves, agronomic traits, and dry matter accumulation were systematically measured and analyzed.

[0039] (1) Yield and economic traits Test methods: After the tobacco leaves matured, they were harvested sequentially according to their parts and dried on individual poles according to their processing. The dried tobacco leaves were graded, and the yield, output value, proportion of medium and high grade tobacco, and average price of the dried tobacco leaves in each plot were statistically analyzed. 1.0 kg of samples each of the upper B2F grade tobacco leaves (upper orange-yellow grade 2), the middle C3F grade tobacco leaves (middle orange-yellow grade 3), and the lower X2F grade tobacco leaves (lower orange-yellow grade 2) were taken for routine chemical composition analysis.

[0040] Table 2. Effects of Examples and Comparative Examples on Tobacco Yield and Economic Traits As shown in Table 2, the yield, proportion of medium-to-high grade tobacco, average price, and output value of the example group were significantly higher than those of the comparative group (deviating from this range). Among them, Example 2 (N1K2) performed the best, with a yield of 2593.82 kg / hm². 2 The output value reached 72,214.87 yuan / hm² 2 Compared with Comparative Example 1 (NOK0), the yield increased by 48.72% and the income increased by 60.74% respectively. Even compared with the comparative examples that only met the single element limit (such as Comparative Examples 4 and 5), the economic traits of the Example Group were superior in all aspects, proving that the synergistic use of nitrogen and potassium to meet the invention limit is the key to achieving high yield and high quality.

[0041] (2) Conventional chemical components of tobacco leaves Determination Method: Take 200g each of B2F, C3F, and X2F tobacco leaves after different treatments, remove the midrib, dry at 65℃, and pulverize. Flow analysis is used to determine the total nitrogen, nicotine, potassium, chlorine, total sugar, and reducing sugar content of the tobacco leaves, according to YC / T161-2002, YC / T160-2002, YC / T173-2003, YC / T162-2002, and YC / T159-2002, respectively. The chemical composition coordination indices, including nitrogen-alkali ratio (total nitrogen / nicotine), sugar-alkali ratio (reducing sugar / nicotine), and potassium-chlorine ratio (potassium content / chlorine content), are calculated.

[0042] Figure 1 This is a statistical chart showing the total nitrogen content of flue-cured tobacco leaves under different nitrogen and potassium application ratios. Figure 1It can be seen that there are significant differences in the total nitrogen content of the flue-cured tobacco leaves, with the middle leaves having the highest total nitrogen content and the upper and lower leaves having relatively lower content. Analysis of the suitable range (2.0%–2.5%) for total nitrogen in high-quality tobacco leaves shows that, in the comparative examples, the total nitrogen content of the N0 series (Comparative Examples 2 and 3) is below the suitable range, while the total nitrogen content of the K0 series (Comparative Examples 4 and 5) is above the suitable range. The total nitrogen content of Examples 1–4 (N1K1, N1K2, N2K1, N2K2) is all within the suitable range, and the content is more consistent, demonstrating the rationality of the invention's limitation on nitrogen and potassium usage.

[0043] Figure 2 This is a statistical chart showing the nicotine content of flue-cured tobacco leaves under different nitrogen and potassium application ratios. Figure 2 The results showed significant differences in nicotine content among different parts of the tobacco leaves after curing, with the upper and middle leaves having similar levels and significantly higher levels than the lower leaves. Based on the suitable nicotine content standard for high-quality tobacco leaves (1.5%–3.5%), the nicotine content of N0K2 (Comparative Example 3) in the comparative example was too low, deviating from the suitable range; the nicotine content of the other comparative examples (N0K0, N0K1, N1K0, N2K0) and all examples (N1K1, N1K2, N2K1, N2K2) were all within the suitable range. The nicotine content of the examples was closer to the ideal level for high-quality tobacco leaves, effectively balancing taste and irritation, and was superior to the single-control effect of the comparative examples.

[0044] Figure 3 This is a statistical chart showing the potassium content of flue-cured tobacco leaves under different nitrogen and potassium application ratios. Potassium content is a core indicator of tobacco quality. Figure 3 The significant effects of combined nitrogen and potassium application are clearly demonstrated. In the examples, as the nitrogen application rate increased, the potassium content in each part first increased and then decreased. (N1 (45 kg N / hm)) 2 The potassium content was relatively high, and Example 2 (N1K2) had the highest potassium content at 1.78%, which was significantly higher than Comparative Example 1 (N0K0) by 122.8%.

[0045] Figure 4 This is a statistical chart showing the chlorine content in different parts of flue-cured tobacco leaves under different nitrogen and potassium application ratios. The suitable range for chloride ions is 0.4% to 0.6%; excessively high levels will affect combustibility and taste. Figure 4 The results showed that the effect of nitrogen and potassium combined application on chlorine content was site-specific: in the examples, the N1 treatment (45 kg N / hm) 2 Under these conditions, the chlorine content in all parts of the K1 and K2 treatments was within a suitable range, while that in the N2 treatment (67.5 kg N / hm) was within a suitable range. 2 Under these conditions, although the chlorine content fluctuated slightly, it still met the high-quality standard. In the comparative example, the chlorine content of some treatments (such as the upper leaves of N2K0) deviated from the suitable range, while the example achieved precise control of chlorine content through precise application, which was better than the single fertilization mode of the comparative example.

[0046] Figure 5 This is a statistical chart showing the total sugar content of different parts of the flue-cured tobacco leaves under different nitrogen and potassium application ratios. Figure 5 The results show that the total sugar content gradient is upper leaves > middle leaves > lower leaves, consistent with the distribution pattern of photosynthetic products. The total sugar content of the examples is generally higher than that of the comparative examples, and the site specificity is more pronounced: the lower leaves have the highest total sugar content in Example 3 (N2K1), the middle leaves have the highest total sugar content in Example 1 (N1K1), and although the upper leaves have the highest total sugar content in Comparative Example 2 (N0K1), the total sugar content of the examples is more stable and exhibits better coordination with other chemical components. The total sugar content of all examples meets the requirements for high-quality tobacco leaves, while the comparative examples show some areas with excessively high or low total sugar content, indicating a less effective control than the examples.

[0047] Figure 6 This is a statistical chart showing the reducing sugar content in different parts of flue-cured tobacco leaves under different nitrogen and potassium application ratios. The suitable range for reducing sugar is 18%–24%, which is a key indicator affecting taste. Figure 6 It can be seen that in the comparative examples, both the nitrogen-deficient treatments (N0K0, N0K1, N0K2) and potassium-deficient treatments (N1K0, N2K0) had reducing sugar content below 18%, which could not meet the requirements for high-quality tobacco leaves. In the examples (N1K1, N1K2, N2K1, N2K2), the reducing sugar content was all within the suitable range and evenly distributed. In particular, nitrogen fertilizer in the examples significantly increased the reducing sugar content of the lower and middle leaves, while potassium fertilizer enhanced the effect on the upper and middle leaves. The synergistic effect avoided the problem of unbalanced reducing sugar content in the comparative examples and effectively improved the sweetness and harmony of the tobacco leaves.

[0048] (3) Agronomic traits Measurement methods: At 60 and 90 days after transplanting, five tobacco plants of uniform growth were randomly selected from each treatment. Agronomic traits such as plant height, stem circumference, maximum leaf length, maximum leaf width, and number of effective leaves were measured according to standard YC / T142-2010. Simultaneously, at 30, 60, 90, and 120 days after transplanting, whole-plant samples were taken. Three tobacco plants of uniform growth were randomly dug up from each treatment, rinsed clean with water, dried, and then separated into leaves, stems, and roots. The samples were blanched at 105℃ for 30 minutes and then dried at 75℃ to constant weight. The dry matter mass was then measured.

[0049] Table 3. Agronomic traits of tobacco 60 days after transplanting As shown in Table 3, 60 days after transplanting, the agronomic traits of the Example group were comprehensively superior to those of the comparative group. Example 2 (N1K2) had the highest plant height (60.69 cm), stem circumference (7.58 cm), number of effective leaves (18.22), and leaf area index (1.58), which were significantly higher than those of Comparative Example 1 (N0K0) by 24.85%, 24.67%, 34.37%, and 88.10%, respectively. In the comparative group, only the treatments of potassium or nitrogen alone (such as Comparative Examples 2, 3, 4, and 5) showed some improvement in agronomic traits, but they were far inferior to those of the Example group, proving that the synergistic application of nitrogen and potassium at the invention-limited dosage can maximize the promotion of tobacco vegetative growth.

[0050] Table 4. Agronomic traits of tobacco 90 days after transplanting As shown in Table 4, the growth advantage of the Example groups continued to expand 90 days after transplanting. Example 4 (N2K2) had the highest plant height (147.02 cm) and stem circumference (8.86 cm), which were 33.27% and 26.57% higher than those of Comparative Example 1, respectively. Example 2 (N1K2) had the largest number of effective leaves (24.50 leaves) and leaf area index (3.24), which were significantly higher than those of Comparative Example 1, by 33.66% and 205.66%, respectively. The improvement in agronomic traits in the Comparative Example groups was limited, and there was uneven growth. This further proves that the nitrogen and potassium application range specified in the invention can meet the nutrient requirements of tobacco in the reproductive growth stage.

[0051] Table 5. Dry matter mass of tobacco seedlings 30 days after transplanting As shown in Table 5, 30 days after transplanting, the total dry matter accumulation of the Example group was significantly higher than that of the Comparative group. The total dry matter of Example 3 (N2K1) and Example 4 (N2K2) both exceeded 29 g / plant, which was more than 118% higher than that of Comparative Example 1 (13.79 g / plant). In the Comparative group, even when high nitrogen or high potassium was applied alone (such as Comparative Examples 3 and 5), the dry matter accumulation was much lower than that of the Example group, which proves that the synergistic application of nitrogen and potassium (within the range of the invention dosage) can quickly initiate the accumulation of tobacco substances.

[0052] Table 6. Dry matter mass of tobacco seedlings 60 days after transplanting As shown in Table 6, 60 days after transplanting, the total dry matter accumulation of the plants in the example groups continued to increase with the optimization of fertilizer application, reaching 145.71 g / plant in Example 4 (N2K2), which was significantly higher than that in Comparative Example 1 by 87.67%. The root-to-shoot ratio of the example groups was more reasonable, which was conducive to nutrient absorption and translocation, while the dry matter accumulation of the comparative example groups showed a "leaf weight imbalance" phenomenon, proving that the nitrogen and potassium application range specified in the invention can achieve a balanced distribution of dry matter.

[0053] Table 7. Dry matter mass of tobacco seedlings 90 days after transplanting As shown in Table 7, 90 days after transplanting, the dry matter accumulation in each part of the example group was significantly higher than that in the comparative group. The upper and lower leaves of Example 1 (N1K1) had the highest dry matter content, which was 230.93% and 106.59% higher than that of Comparative Example 1, respectively. The roots and the whole plant of Example 2 (N1K2) had the highest dry matter content. The dry matter accumulation in the comparative group showed a "partial imbalance", while the dry matter in the example group was evenly distributed among the leaves, stems and roots, laying a material foundation for high yield and quality.

[0054] Table 8. Dry matter mass of tobacco 120 days after transplanting As shown in Table 8, 120 days after transplanting (harvest period), the total dry matter accumulation of the Example group reached its peak, which was significantly higher than that of the Comparative Example group. Example 2 (N1K2) had the highest total dry matter accumulation (457.90 g / plant), which was 192.36% higher than that of Comparative Example 1; Example 1 (N1K1) was the second highest, which was 166.25% higher than that of Comparative Example 1; the highest dry matter accumulation of the Comparative Example group was only 284.26 g / plant (Comparative Example 3), which was less than 62% of that of Example 2. This fully demonstrates that the nitrogen and potassium dosage range specified in the invention can maximize the total dry matter accumulation of tobacco and distribute it evenly.

[0055] In summary, the tobacco leaves obtained by the method of this invention are superior to those of the comparative examples in terms of yield and economic traits, tobacco quality, and growth and development: (1) In terms of yield and economic traits: the yield, output value, proportion of medium and high grade tobacco, and average price of the example group are significantly better than those of the comparative group, of which example 2 (N1K2) performed the best and exceeded all the comparative examples; (2) In terms of tobacco quality: the chemical composition of the flue-cured tobacco leaves of the example group is more coordinated, the potassium content is significantly increased, and the total nitrogen, nicotine, and chloride ion content are all within the excellent range. The nitrogen-alkali ratio, sugar-alkali ratio, and potassium-chlorine ratio are optimized, of which example 2 has the best quality index; (3) In terms of growth and development: the agronomic traits (plant height, stem circumference, leaf area index, etc.) and the amount of dry matter accumulation at each stage of the example group are significantly better than those of the comparative group at 60 days and 90 days after transplanting, and the dry matter distribution is balanced, which provides a guarantee for high yield and high quality.

[0056] Taking all indicators into account, the invention specifies a nitrogen content of 45-67.5 kg N / hm². 2 Potassium 135-202.5 kg K2O / hm 2 "The dosage range is the optimal technical solution under the tobacco-potato rotation mode. Among them, Example 2 (N1K2) has the best overall effect and can achieve high-yield, high-quality and high-efficiency tobacco production."

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A fertilization method for improving tobacco yield and quality under a tobacco-potato rotation system, characterized in that, Includes the following steps: Step 1: Select a rotation field where the previous crop was sweet potato, and the soil physicochemical properties meet the following requirements: pH 7.20-7.30, organic matter 12.00-12.80 g / kg, available nitrogen 58.00-60.00 mg / kg, available phosphorus 10.00-11.50 mg / kg, and available potassium 115.00-118.00 mg / kg; Step 2: Apply fertilizer to the field selected in Step 1. The fertilizer includes nitrogen, potassium, and phosphorus fertilizers; wherein, by pure amount, the application rate of nitrogen is 45-67.5 kg N / hm². 2 The potassium application rate is 135-202.5 kg K2O / hm. 2 The fertilizer is applied all at once after ridging. The nitrogen fertilizer and potassium fertilizer are mixed and spread in the furrows, and the phosphorus fertilizer is applied separately in strips at the bottom of the ridges. Step 3: Transplant the tobacco seedlings to the fertilized field in early May, with a row spacing of 1-1.5m and a plant spacing of 0.4-0.6m.

2. The method according to claim 1, characterized in that, The nitrogen fertilizer is calcium ammonium nitrate, and the potassium fertilizer is potassium sulfate.

3. The method according to claim 1 or 2, characterized in that, In step one, the soil physicochemical properties meet the following requirements: pH 7.25, organic matter 12.37 g / kg, available nitrogen 59.03 mg / kg, available phosphorus 10.86 mg / kg, and available potassium 116.32 mg / kg.

4. The method according to claim 1, characterized in that, In step two, the amount of phosphorus applied is 66-69 kg P2O5 / hm. 2 .

5. The method according to claim 1, characterized in that, In step two, the phosphate fertilizer is superphosphate.

6. The method according to claim 3, characterized in that, The nitrogen application rate is 45 kg N / hm. 2 The potassium application rate is 202.5 kg K₂O / hm. 2 .

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