Method for improving tobacco quality by combined application of biochar and montmorillonite

Abstract

The application discloses a method for improving tobacco quality by jointly applying biochar and montmorillonite, and belongs to the field of agricultural soil improvement and tobacco cultivation technology. In view of the problems of the existing tobacco planting soil improvement technology of separately applying biochar, such as lag of tobacco quality improvement and high improvement cost, the tobacco stalk is first pyrolyzed at 380 DEG C for 2 hours and then crushed into biochar particles with a particle size of less than or equal to 2 mm, and then the biochar particles and the montmorillonite are applied to the surface of the tobacco planting soil at a ratio of 2 t / ha of the biochar particles and 2 t / ha of the montmorillonite, and rotary tillage is performed to uniformly mix the biochar particles and the montmorillonite with the plough layer soil below the surface to 10-30 cm, and preferably the rotary tillage is completed 7-15 days before tobacco transplanting. The method can significantly improve the tobacco quality in the same season, reduces the improvement cost, simultaneously repairs the physical and chemical properties and the micro-ecological function of the degraded tobacco planting soil, and is suitable for the improvement of the acidified and degraded tobacco planting soil.

Description

Technical Field

[0001] This invention relates to a method for improving tobacco quality through the combined application of biochar and montmorillonite, belonging to the field of agricultural soil improvement and tobacco cultivation technology. Background Technology

[0002] Tobacco is an important economic crop in my country. Statistics show that the annual tobacco planting area in my country remains stable at over 1 million hectares, with more than one million tobacco farmers, giving the tobacco industry a significant position in the national economy. However, with the continuous expansion of tobacco planting scale and the extension of continuous cropping years, soil quality problems in tobacco-growing areas have become increasingly prominent. On the one hand, long-term excessive application of chemical fertilizers has led to soil acidification, compaction, nutrient imbalance, destruction of soil aggregate structure, increased bulk density, decreased porosity, and a significant decline in water and fertilizer retention capacity. Studies have shown that soil pH values ​​in major tobacco-growing areas in my country have generally decreased by 0.5-1.5 units, and soil organic matter content has shown a downward trend year by year. On the other hand, continuous cropping obstacles have led to an imbalance in the soil microbial community structure, a reduction in the number of beneficial microorganisms, an accumulation of pathogenic microorganisms, a decrease in soil enzyme activity, and a degradation of soil ecosystem functions. The activity of key enzymes related to carbon, nitrogen, and phosphorus cycles in the soil has significantly decreased, affecting the transformation and supply capacity of soil nutrients. Meanwhile, soil degradation directly leads to nutritional imbalances and metabolic disorders in tobacco plants, resulting in stunted growth, thin and light leaves, reduced disease resistance, and increased susceptibility to diseases. The chemical composition of tobacco leaves also deteriorates, with decreased levels of reducing sugars, total sugars, and potassium, abnormal nicotine content, and weakened quality characteristics, making it difficult to meet the cigarette industry's demand for high-quality tobacco raw materials.

[0003] Existing literature (CN110326385A) discloses a method for improving tobacco-growing soil using biochar. This method involves carbonizing agricultural and forestry waste to obtain biochar, then mixing the biochar particles with the topsoil of the tobacco-growing soil to improve the soil. This can increase soil carbon and nitrogen content, water content, and available potassium content, improve soil compaction and aeration, and ultimately increase tobacco plant biomass. However, this method only uses biochar as a single amendment material, without considering the synergistic effects with other amendment materials. It can only improve the basic physicochemical properties of the soil, but cannot simultaneously regulate the activity of soil carbon cycle-related enzymes or optimize the soil microbial community structure. This results in a limited improvement in soil organic carbon accumulation efficiency and nutrient conversion and supply capacity, failing to provide optimal nutrient supply conditions for tobacco plant growth in the current season. Consequently, the improvement in tobacco leaf quality has a time lag of at least 1-2 planting seasons, failing to meet the production requirements of "seasonal high-quality production" in tobacco cultivation. Summary of the Invention

[0004] (a) Purpose of the invention

[0005] The purpose of this invention is to overcome the shortcomings of existing tobacco soil improvement technologies, such as the delayed effect of applying biochar alone on improving tobacco quality. This invention provides a method for improving tobacco quality by combining biochar and montmorillonite, which can significantly improve tobacco quality in the current season while enhancing the soil's carbon sequestration capacity.

[0006] (II) Technical Solution

[0007] A method for improving tobacco quality through the combined application of biochar and montmorillonite includes the following steps:

[0008] S1. Preparation of biochar pellets: Prepare tobacco straw biochar and crush it to obtain biochar pellets;

[0009] S2. Combined application of soil improvement: Biochar granules and montmorillonite are mixed at a mass ratio of 1-4:1 and then applied to the surface of the tobacco-growing soil in one go. Afterwards, rotary tillage is carried out to mix the two improvement materials evenly with the topsoil layer of tobacco-growing soil 10-30cm below the surface, thereby completing soil improvement and enhancing tobacco quality.

[0010] Preferably, in step S1, the tobacco stalks are pyrolyzed at 380°C for 2 hours, and then the biochar obtained from the pyrolysis is pulverized to obtain biochar particles with a particle size ≤2mm.

[0011] Preferably, in step S2, the biochar particles and montmorillonite are mixed at an application rate of 2 t / ha of biochar particles and 2 t / ha of montmorillonite.

[0012] Preferably, the montmorillonite used in step S2 is calcium-based montmorillonite with a purity ≥90% and a particle size ≤1mm.

[0013] Preferably, the rotary tillage depth in step S2 is 25-30cm, the number of rotary tillage passes is 2-3, and the mixing uniformity of the two improved materials with the topsoil is ≥90%.

[0014] Preferably, the combined application of the improvement work in step S2 is completed 7 to 15 days before tobacco transplanting.

[0015] Preferably, the tobacco planting soil is acidified and degraded tobacco planting soil with a continuous cropping period of ≥5 years and an initial pH value of 4.5~5.5.

[0016] (III) Beneficial Effects

[0017] This invention utilizes a combined application of biochar and montmorillonite in equal proportions to achieve simultaneous regulation of soil carbon cycle enzyme activity and optimization of bacterial community structure through the synergistic effect of the two amendments. On the one hand, it can increase the activity of carbon-fixing enzyme RubisCO by more than 15% and reduce the activities of carbon-degrading enzymes BG and PPO by more than 10%, thereby improving the efficiency of soil organic carbon accumulation. On the other hand, it can optimize the composition of soil bacterial communities, increase the abundance of carbon-fixing functional microorganisms, and thus significantly improve the soil's nutrient conversion and supply capacity, providing sufficient and balanced nutrient supply for the growth of tobacco plants in the current season. This solves the problem that the improvement of tobacco leaf quality requires a lag of 1-2 planting seasons in existing biochar-only application technologies, achieving a significant improvement in tobacco leaf quality in the current season. After the amendment, the reducing sugar content in the middle leaves of flue-cured tobacco can reach more than 26%, the total sugar content can reach more than 29%, and the chlorine content can reach more than 0.8%. At the same time, the agronomic traits of tobacco plants, such as plant height, internode distance, maximum leaf width, and maximum leaf area, are all significantly improved.

[0018] Furthermore, this invention achieves synergistic improvement of tobacco quality and soil carbon sequestration. The contents of organic carbon, soluble organic carbon, available phosphorus, and nitrate nitrogen in the improved soil are significantly increased. The physicochemical properties and microecological functions of degraded tobacco-growing soil are restored simultaneously, which is conducive to the long-term healthy cultivation of tobacco-growing soil. Attached Figure Description

[0019] Figure 1 The effects of different soil amendment methods on soil enzyme activity;

[0020] Figure 2 The impact of different soil amendment methods on soil bacterial diversity;

[0021] Figure 3 The effects of different soil amendment methods on soil bacterial community composition (a) and community structure (b);

[0022] Figure 4 The effects of different soil amendment methods on functional genes related to soil bacterial carbon fixation (a) and carbon decomposition (b). Detailed Implementation

[0023] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0024] Existing tobacco soil improvement techniques often rely on the single application of biochar, which suffers from high biochar application rates, high improvement costs, and a lag of 1-2 planting seasons in improving tobacco quality, failing to meet the production demands of "perennial high yield and quality" in tobacco cultivation. The solution proposed in this invention is to combine low-dose tobacco straw biochar with montmorillonite in equal proportions. Utilizing the synergistic effect of these two improvement materials, the activity of soil carbon cycle-related enzymes is simultaneously regulated, and the soil bacterial community structure is optimized. This significantly reduces improvement costs while simultaneously achieving a substantial improvement in tobacco quality and a simultaneous enhancement of soil carbon sequestration capacity in the current season.

[0025] 1. Materials

[0026] Biochar pellets: Waste tobacco stalks generated after local tobacco harvesting are collected and impurities are removed. They are then placed in a carbonization furnace at 380℃ to decompose in the absence of oxygen for 2 hours. After cooling, they are crushed and sieved to obtain biochar pellets with a particle size of 0.5~2mm.

[0027] Montmorillonite: Calcium-based montmorillonite with a purity of 92% and a particle size ≤1mm is selected.

[0028] 2. Experiment

[0029] Ten days before tobacco transplanting, 2 t / ha of biochar granules (B), 2 t / ha of calcium-based montmorillonite (M), and 2 t / ha of biochar granules + 2 t / ha of calcium-based montmorillonite (MB) were applied in a single application to the surface of the tobacco-growing soil (different areas of the same plot in the same region; the tobacco-growing soil was acidified and degraded after 5 years of continuous cropping, with an initial pH of 5). The materials were then thoroughly mixed with the topsoil layer (10–30 cm below the surface) through rotary tillage, requiring two passes, with a mixing uniformity of ≥90%. Soil without amendments was used as a blank control (CK). Subsequent transplanting, field management, and harvesting were carried out according to local conventional tobacco cultivation and management procedures.

[0030] 3. Results

[0031] (1) Effects of different soil improvement methods on the physical properties of tobacco leaves

[0032] The effects of different soil amendment methods on the physical properties of tobacco leaves are shown in Table 1. Compared with the control (CK) treatment, the B and MB treatments significantly increased the leaf length of tobacco leaves, while there were no significant differences in other physical property indicators among the different treatments.

[0033] Table 1. Effects of different soil improvement methods on the physical properties of tobacco leaves

[0034]

[0035] (2) Effects of different soil improvement methods on the chemical composition of tobacco leaves

[0036] Different soil amendment methods had a significant impact on the chemical composition of tobacco leaves. Compared with the control (CK) treatment, the reducing sugar, total sugar, potassium, and chloride contents of the MB treatment were significantly higher than those of the CK (P<0.05), while the potassium content of the B treatment was significantly higher than that of the CK (P<0.05). There were no significant differences in other chemical components among the different treatments.

[0037] Table 2. Effects of different soil amendment methods on the chemical composition of tobacco leaves

[0038]

[0039] (3) Effects of different soil improvement methods on tobacco agronomic traits

[0040] The effects of different soil amendment methods on tobacco agronomic traits are shown in Table 3. Compared with the control (CK) treatment, the MB treatment significantly increased tobacco plant height, internode distance, maximum leaf width, and maximum leaf area; the B treatment significantly increased tobacco maximum leaf area and maximum leaf width; the M treatment significantly increased tobacco internode distance, maximum leaf width, and maximum leaf area, but significantly decreased the number of effective leaves and stem circumference.

[0041] Table 3. Effects of different soil improvement methods on tobacco agronomic traits.

[0042]

[0043] (4) The effects of different soil improvement methods on soil physicochemical properties

[0044] As shown in Table 4, compared with CK, the soil organic carbon and soluble organic carbon content in the MB treatment were significantly higher than those in CK (P<0.05), and the available phosphorus content in the soil of the B, M and MB treatments was significantly increased.

[0045] Table 4. Effects of different soil amendment methods on soil physicochemical properties

[0046]

[0047] (5) Effects of different soil amendment methods on the activity of soil carbon cycle-related enzymes

[0048] Regarding the activities of enzymes related to soil carbon cycling, except for cellobiase (CBH) activity which showed no significant difference among different soil amendment methods, the activities of carbon fixation enzyme (RubisCO), β-glucosidase (BG), polyphenol oxidase (PPO), and peroxidase (POD) all showed significant differences. Figure 1Specifically, the RubisCO activity associated with carbon fixation was significantly higher in B, M, and MB treatments than in CK (P<0.05); among the hydrolases associated with carbon decomposition, the BG and PPO activities in B, M, and MB treatments were significantly lower than in CK (P<0.05), and the POD activity in MB treatment was significantly lower than in CK.

[0049] (6) The impact of different soil amendment methods on soil bacterial diversity

[0050] A total of 33,632 valid sequences were obtained from 12 soil samples, and clustering yielded 4,676 ASVs. Species taxonomy and annotation results showed that the soil bacterial community belonged to 34 phyla, 92 classes, 201 orders, 321 families, and 606 genera. Soil bacterial community diversity results are as follows: Figure 2 As shown in the figure, compared with the CK treatment, the species richness Chao index and community diversity Shannon index of the B, M and MB treatments showed an increasing trend, but none of them reached a significant level.

[0051] (7) The effects of different soil amendment methods on soil bacterial community composition

[0052] Different soil improvement methods result in different soil bacterial community compositions in tobacco cultivation, such as Figure 3 As shown in Figure a, the bacterial phyla with a relative abundance greater than 1% include Chloroflexota, Acidobacteriota, Pseudomonadota, Actinomycetota, Bacillota, Bacteroidota, Gemmatimonadetes, Verrucomicrobita, Patescibacteria, Cyanobacteriota, and Planctmycetota. Among them, Chloroflexota, Acidobacteriota, Pseudomonadota, Actinomycetota, and Bacillota are dominant, with their relative abundance exceeding 80%. Figure 3 a). Compared with the control (CK), the relative abundance of Bacillota was significantly lower in the MB treatment (P<0.05), while the relative abundance of Planctomycetota was significantly higher in the MB treatment. Other major bacterial phyla showed no significant differences among treatments. NMDS analysis results (Figure) Figure 3(b) The community structure of MB and CK differed significantly (ANOSIM, P<0.01), and they were clearly separated along the first axis.

[0053] (8) The effects of different soil improvement methods on carbon cycle-related functional genes

[0054] To further understand the effects of different biochar additions on microbial carbon cycling functional genes, PICRUSt2 was used to predict bacterial function in soil. KEGG functional annotation information (Pathway, Enzyme, Module, Gene) for each gene was obtained from the KEGG (Kyoto Encyclopedia of Genes and Genomes) database and statistical analysis was performed. Results are as follows: Figure 4 As shown, among the key functional genes related to carbon fixation, the abundance of cbbL and cbbS genes tended to increase in B, M, and MB treatments compared to the CK treatment, but this did not reach a significant level. Among the key functional genes related to carbon decomposition, the abundance of pulA gene, which is related to starch decomposition, was significantly lower in MB treatment than in CK, and the abundance of cbhA gene, which is related to cellulose decomposition, was significantly lower in M ​​treatment than in CK.

[0055] In summary, compared with the control, the present invention effectively improves the following indicators:

[0056] Soil microecological indicators: In the improved tobacco-growing soil, the activities of ribulose-1,5-bisphosphate carboxylase / oxygenase (RubisCO, commonly known as carbon fixation enzyme) increased by more than 15% compared with the control, while the activities of β-glucosidase (BG, carbon degrading enzyme) and polyphenol oxidase (PPO, carbon degrading enzyme) decreased by more than 10% compared with the control; the relative abundance of Bacillota decreased by more than 8% compared with the control, while the relative abundance of Planctomycetota increased by more than 10% compared with the control; the contents of soil organic carbon, soluble organic carbon, available phosphorus, and nitrate nitrogen were all significantly increased.

[0057] Agronomic traits of tobacco plants: Plant height, internode distance, maximum leaf width, and maximum leaf area were significantly increased compared with the control group, while the number of effective leaves and stem circumference did not decrease significantly.

[0058] Tobacco leaf quality indicators: The reducing sugar content of the middle leaves of the planted flue-cured tobacco was ≥26%, the total sugar content was ≥29%, and the chlorine content was ≥0.8%. The core quality indicators were significantly better than those of the B and M controls and the blank control, proving that the synergistic effect of biochar and montmorillonite can improve the quality of tobacco leaves in the same season without any time lag.

[0059] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for improving tobacco quality through the combined application of biochar and montmorillonite, characterized in that, Includes the following steps: S1. Preparation of biochar pellets: Prepare tobacco straw biochar and crush it to obtain biochar pellets; S2. Combined application of soil improvement: Biochar granules and montmorillonite are mixed at a mass ratio of 1-4:1 and then applied to the surface of the tobacco-growing soil in one go. Afterwards, rotary tillage is carried out to mix the two improvement materials evenly with the topsoil layer of tobacco-growing soil 10-30cm below the surface, thereby completing soil improvement and enhancing tobacco quality.

2. The method for improving tobacco quality by combining biochar and montmorillonite according to claim 1, characterized in that, In step S1, the tobacco stalks are pyrolyzed at 380°C for 2 hours, and then the biochar obtained from the pyrolysis is pulverized to obtain biochar particles with a particle size ≤2mm.

3. The method for improving tobacco quality by combining biochar and montmorillonite according to claim 1, characterized in that, In step S2, biochar particles and montmorillonite are mixed at an application rate of 2 t / ha of biochar particles and 2 t / ha of montmorillonite.

4. The method for improving tobacco quality by combining biochar and montmorillonite according to claim 1, characterized in that, The montmorillonite used in step S2 is calcium-based montmorillonite with a purity of ≥90% and a particle size of ≤1mm.

5. The method for improving tobacco quality by combining biochar and montmorillonite according to claim 1, characterized in that, The rotary tillage depth in step S2 is 25-30cm, the number of rotary tillage passes is 2-3, and the uniformity of the two amendments with the topsoil is ≥90%.

6. The method for improving tobacco quality by combining biochar and montmorillonite according to claim 1, characterized in that, The combined application of the improvement work in step S2 should be completed 7 to 15 days before tobacco transplanting.

7. The method for improving tobacco quality by combining biochar and montmorillonite according to claim 1, characterized in that, The tobacco-growing soil is acidified and degraded tobacco-growing soil with a continuous cropping period of ≥5 years and an initial pH value of 4.5~5.5.

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