Regulation and control method for preventing color fading of flue-cured tobacco leaves in acidified soil and application

Abstract

The invention relates to a regulation and control method for preventing color fading of flue-cured tobacco leaves in acidified soil. The regulation and control method comprises the following steps: S1, selecting a proper calcium fertilizer variety according to the acid-base property of the acidified soil and the requirements of flue-cured tobacco; s2, determining the use amount of calcium fertilizer according to the basic fertility of soil, the variety of tobacco and a planting technology; s3, applying a calcium fertilizer according to requirements by adopting a method of combining base fertilizer strip application and foliage spraying; s4, after the calcium fertilizer is applied, field management is carried out in time, so that sufficient absorption and utilization of the calcium fertilizer are promoted. The regulation and control method is simple in step, the appearance chromaticity of the tobacco leaves can be improved, and the fading resistance of the flue-cured tobacco leaves is improved.

Description

Technical Field

[0001] The invention relates to the technical field of tobacco, and in particular to a control method for preventing tobacco leaves from fading after being baked in acidified soil and its application. Background Art

[0002] Tobacco leaves are the foundation for the survival and development of the industry. The development of Chinese cigarettes has continuously increased the requirements for tobacco leaf raw materials. Tobacco leaf color itself refers to the state of related colors, color saturation and color value of the same type of tobacco leaves after modulation. It is caused by the presence of pigments, and different colors are formed due to the different proportions of various pigments. It is an important indicator in the evaluation of the appearance quality of flue-cured tobacco in my country. It can reflect the intrinsic quality of flue-cured tobacco to a certain extent, among which orange-yellow is the best. The appearance color of tobacco leaves varies depending on the variety, planting area, growth environment and storage conditions.

[0003] In recent years, the fading of flue-cured tobacco leaves has become a prominent problem in my country's tobacco production. It is particularly serious in the southern production areas of my country, especially in the southeastern acidic soil tobacco production areas. A considerable portion of flue-cured tobacco leaves in these production areas have faded, which seriously affects the appearance quality and grade structure of tobacco leaves. This type of tobacco leaves are very prone to browning during the storage and aging process, resulting in a significant decrease in tobacco leaf quality and industrial availability. Guangdong tobacco production areas mainly include two types of typical tobacco-growing soils: sandy mud fields and purple soils. The tobacco leaves produced in the former have serious color fading and poor gloss, and the appearance and internal quality are poor, resulting in a low purchase price for tobacco leaves. The tobacco leaves produced in the latter are orange-yellow in color, bright in color, strong in gloss, stable, and full, with good appearance and internal quality, and a high purchase price.

[0004] At present, the fading phenomenon of Yunyan 87, a flue-cured tobacco variety, which is planted in a large area in sandy mud fields (commonly known as paddy field tobacco by farmers, which occupies the majority of tobacco fields in Guangdong Province and has a trend of expanding year by year) is very serious. Since Yunyan 87 is the main variety in the sandy mud field tobacco area of ​​Guangdong Province and occupies a prominent position in the formula of industrial cigarette brands, how to prevent and control tobacco leaf fading is a difficult problem that needs to be solved urgently in the current tobacco production and tobacco raw material utilization. Summary of the invention

[0005] Based on this, the object of the present invention is to provide a control method for preventing tobacco leaves from fading after being cured in acidified soil, which has the advantages of improving the appearance color of tobacco leaves and enhancing the anti-fading ability of tobacco leaves after curing.

[0006] A method for preventing tobacco leaves from fading after being baked in acidified soil, comprising the following steps:

[0007] S1: Choose the appropriate calcium fertilizer type according to the acidity and alkalinity of the acidified soil and the needs of flue-cured tobacco;

[0008] S2: Determine the amount of calcium fertilizer based on the basic fertility of the soil, tobacco variety and planting technology;

[0009] S3: Apply calcium fertilizer by combining basal fertilizer strip application and foliar spraying as needed;

[0010] S4: After applying calcium fertilizer, carry out field management in a timely manner to promote the full absorption and utilization of calcium fertilizer.

[0011] Furthermore, the calcium fertilizer in step S1 is one of the calcium fertilizer combinations selected from the group consisting of calcium oxide (basal application) + calcium nitrate (spraying), calcium oxide (basal application) + sugar alcohol calcium (spraying), oyster shell calcium (basal application) + calcium nitrate (spraying), and oyster shell calcium (basal application) + sugar alcohol calcium (spraying).

[0012] Furthermore, in S2, the calcium content of the soil can be understood through soil testing, so as to determine a reasonable amount of calcium fertilizer. After the use of the calcium fertilizer, the exchangeable calcium content of the acidified soil is greater than 6Cmol / kg.

[0013] Furthermore, the strip application method of the base fertilizer in S3 is: before planting tobacco, ridges are formed, and strip furrows with a depth of 15 cm are dug downward along the planting center of the ridge body, and the calcium fertilizer is sprinkled, and then the furrows are covered with soil to restore the soil, or two small furrows with a depth of about 10 cm are dug on both sides of the land where tobacco is planted, and the calcium fertilizer is sprinkled, and then the furrows are leveled and ridged.

[0014] Furthermore, the foliar spraying method in S3 is: prepare calcium fertilizer nutrient solution according to the specified concentration, use an electric sprayer, and spray it from bottom to top on the front and back of each leaf and the surface of the stem of the tobacco plant in all directions, and the spraying time is once every 50 days, 60 days, and 70 days after the tobacco plants are transplanted.

[0015] Furthermore, the S4 field management includes covering the ground with black and white double-color film, maintaining a ridge height of 30 cm after soil cultivation, timely removal of residual foot leaves and axillary buds, topping to retain a final number of 20 harvestable leaves, timely harvesting of tobacco leaves when they mature and turn yellow, and baking according to the standard three-stage baking technology of tobacco leaves.

[0016] The present invention also includes application of the above-mentioned control method for preventing tobacco leaves from fading after being baked in acidified soil in tobacco planting.

[0017] Compared with the prior art, the present invention has the following advantages and effects:

[0018] The invention promotes the growth of tobacco plants by adding exogenous calcium, increases the calcium content in acidic soil and tobacco leaves, reduces the content of mineral elements such as copper, zinc, manganese, sulfur, etc., improves the appearance color of tobacco leaves, and significantly improves the anti-fading ability of tobacco leaves after curing.

[0019] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a comparison chart of tobacco leaves baked in purple soil (no fading) and tobacco leaves baked in sandy mud fields (easy to fade);

[0021] Figure 2 This is the result diagram of the effect of different calcium source treatments on the dry matter accumulation of tobacco plants;

[0022] Figure 3 This is the result diagram of the effect of different calcium sources on the chromaticity of flue-cured tobacco leaves;

[0023] Figure 4 This is the result of different calcium source measures on the pigment content of flue-cured tobacco leaves;

[0024] Figure 5 This is the correlation result diagram between the color chromaticity of the tobacco leaf appearance after curing and the mineral element index;

[0025] Figure 6 This is a graph showing the effects of different calcium source treatments on the appearance quality of flue-cured tobacco leaves. DETAILED DESCRIPTION

[0026] The applicant conducted further research on the purple sandstone tobacco-growing area and sandy muddy soil, and found that the two soils differed greatly in nutrients, mineral element content, and pH. The former was slightly alkaline, with high calcium, magnesium, and potassium contents. The tobacco leaves were orange-yellow after being roasted, and the color was stable. The tobacco leaves had excellent internal quality. The latter was slightly acidic, with high organic matter content, but low calcium and potassium content. The tobacco leaves were lemon yellow at first after being roasted, and then quickly faded to brown, and the internal quality of the tobacco leaves deteriorated. The appearance of the two soils was as follows: Figure 1 In order to explore whether the difference in chromaticity and stability of flue-cured tobacco leaves produced in the two types of soils is due to the soil environment itself, and whether more nutrients are involved in pigment synthesis and decomposition, thereby affecting the color fixation and fading of flue-cured tobacco leaves, the applicant conducted in-depth research.

[0027] First of all, in the process of tobacco growth, in addition to carbon, hydrogen, oxygen, and nitrogen, normal nutrition also requires the absorption of another group of important elements, namely mineral elements, among which phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, molybdenum, copper, boron, zinc, etc. are essential mineral elements in the development of tobacco. They have a very significant impact on the aroma, taste, appearance, and irritation of tobacco leaves. Although the amount of these elements absorbed varies, they are all equally important and cannot replace each other. If a certain element is absorbed too much or too little, it will affect the normal growth of tobacco plants and reduce the yield and quality of tobacco leaves. It is generally believed that tobacco leaves with low sulfur, chlorine and calcium content and high potassium and magnesium content have better overall quality. Potassium, magnesium and phosphorus are mineral elements that are beneficial to the overall quality of tobacco leaves. The content of these three mineral elements is high in the middle, orange, mature, and high-grade tobacco leaves, while sulfur and chlorine are the opposite.

[0028] The pH value of soil has an important influence on the absorption of mineral nutrients. There are two main effects. One is the effect on the surface charge of tobacco root cells, which indirectly affects the absorption of nutrients by tobacco. The other is the effect on the effectiveness of nutrient ions in the soil, thereby affecting the absorption of nutrients by tobacco. Too high or too low soil pH is not conducive to the absorption of nutrients by tobacco. When the pH is too low, the permeability of the root cell protoplasm membrane is damaged, reducing the net absorption of nutrients.

[0029] After further research on acidic sandy mud fields, the applicant found that compared with high-quality purple soil for tobacco planting, the acidic sandy mud fields in Guangdong tobacco-growing areas lack exchangeable calcium, and the calcium content in the roots, stems and leaves of tobacco plants is low, which has an adverse effect on tobacco leaf yield and quality. Calcium itself is one of the indispensable medium-amount nutrients in the growth and development of tobacco. Its content in tobacco ash is second only to potassium. It has many physiological functions such as stabilizing cell walls and cell membrane structures, regulating the activity of many important enzymes in cells, alleviating the toxicity caused by excessive mineral ions, and improving plant resistance. It plays a dual role of nutrition and signaling and is considered to be the general regulator of cell metabolism. Based on this, the applicant conducted relevant research on whether there is a correlation between exogenous calcium and the fading of tobacco leaves after curing.

[0030] The experimental details are as follows:

[0031] 1. Overview of the Experimental Site

[0032] The experiment was conducted from January to July 2023 in Xihe Town, Dapu County, Meizhou City, Guangdong Province (24°30′33″N, 116°44′46″E). The soil type of the experimental site was slightly acidic Masha mud field. The previous crop was rice. The fields were square with medium to high fertility. The basic nutrient status of the soil was pH 5.49, 23.75g / kg organic matter, 176.17mg / kg alkaline nitrogen, 359.51mg / kg available phosphorus, and 276.52mg / kg available potassium.

[0033] 2. Test materials

[0034] The types of calcium fertilizers tested in the experiment are: calcium oxide (CaO), analytically pure AR, purity ≥98%, produced by Tianjin Damao Chemical Reagent Factory; calcium nitrate (Ca(NO3)2), analytically pure AR, purity ≥99%, produced by Guangzhou Chemical Reagent Factory; sugar alcohol calcium produced by Shandong Lvlong Biotechnology Co., Ltd., calcium content ≥150g / L; oyster shell calcium produced by Zhanjiang Botai Biotechnology Co., Ltd., calcium content ≥35%. The tobacco variety tested is the local main variety 'Yunyan 87'.

[0035] 3. Experimental design

[0036] The experiment set up five calcium fertilizer treatment groups, namely, group T1: ordinary acidic hemp sand mud field control (CK); group T2: exogenous calcium selected calcium oxide (1500kg / hm 2 , basal fertilizer strip application) + exogenous calcium selected from sugar alcohol calcium (0.1% ppm concentration, foliar spraying); T3 group: exogenous calcium selected from calcium oxide (1500kg / hm 2 , basal fertilizer strip application) + exogenous calcium selected calcium nitrate (0.5% ppm concentration, foliar spray); T4 group: exogenous calcium selected oyster shell calcium (1500kg / hm 2 , basal fertilizer strip application) + exogenous calcium selected from sugar alcohol calcium (0.1% ppm concentration, foliar spraying); T5 group: exogenous calcium selected from oyster shell calcium (1500kg / hm 2 , basal fertilizer strip application) + exogenous calcium selected calcium nitrate (0.5% ppm concentration, foliar spraying). Each experimental treatment was repeated three times, with a randomized block design, a total of 15 plots, row spacing of 1.2m×0.5m, 40 plants planted in each plot, and protective rows set around. Fertilization and field management of each plot were carried out according to the local technical specifications for high-quality tobacco production.

[0037] The strip application method of basal fertilizer is to make ridges before tobacco planting, and to dig a 15 cm deep furrow along the planting center of the ridge, sprinkle the calcium fertilizer, and then cover the furrow with soil to restore it, or to dig two small furrows with a depth of about 10 cm on both sides of the land where tobacco is planted, sprinkle the calcium fertilizer, and then level the furrows and make ridges; the foliar spraying method is to prepare calcium fertilizer nutrient solution according to the specified concentration, use an electric sprayer, and spray it in all directions from bottom to top on the front and back of each leaf and the surface of the stem of the tobacco plant, and the spraying time is once every 50 days, 60 days, and 70 days after the tobacco plant is transplanted.

[0038] 4. Sample collection and determination method

[0039] Soil sampling and determination of mineral elements: After the flue-cured tobacco is harvested, soil samples are collected from the 5-20 cm tillage layer of each plot using a soil drill according to the five-point method. After mixing evenly, samples are taken according to the quartering method. After sieving through 200 mesh, the soil is air-dried and ground for testing. The exchangeable calcium and exchangeable magnesium contents of the soil are determined by the EDTA-ammonium acetate exchange method; the effective iron (Fe), effective manganese (Mn), effective copper (Cu), effective zinc (Zn), and effective molybdenum (Mo) contents of the soil are determined by the DTPA-TEA extraction method; the effective boron content of the soil is determined by the azomethine-H colorimetric method; and the effective sulfur (S) content of the soil is determined by the barium sulfate turbidimetric method.

[0040] Tobacco plant sampling and determination of mineral elements: Three tobacco plants with uniform growth were selected from each plot at maturity (95 days after transplanting) and harvested separately. Each plant was divided into three parts: root, stem and leaf. After being dried in an oven at 105℃ for half an hour, they were dried to constant weight, and the dry matter weight of each plant was calculated. After the baking was completed, 2 kg of C3F grade tobacco leaves from the middle of the baking were selected from each plot and sealed for storage. Half of them were dried and powdered for tobacco leaf mineral element detection. After nitric acid digestion, the mass fractions of calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), boron (B), sulfur (S), and molybdenum (Mo) were determined using an inductively coupled plasma emission spectrometer (iCAP-7200HSDuo, Thermo Fisher Scientific, USA).

[0041] Tobacco leaf chromaticity and pigment determination: In the remaining half of the flue-cured tobacco leaves mentioned above, 20 leaves with relatively uniform appearance color were selected from each plot, and 6 sites were selected from the upper, middle and lower parts along both sides of the main vein of each leaf for chromaticity detection. Specifically, a CR-10plus computer colorimeter (Konica Minolta, Japan) was used to determine the color difference values ​​(L*: dark-light, a*: green-red, b*: blue-yellow, c*: gray-saturated). After the chromaticity detection was completed, the sample was ground, and the ethanol-acetone extraction colorimetric method was used to determine the contents of chlorophyll a, chlorophyll b and carotenoids in the flue-cured tobacco leaves, and the ethanol-petroleum ether extraction direct colorimetric method was used to determine the β-carotene content in the tobacco leaves.

[0042] 5. Data processing

[0043] Excel 2016 and SPSS 20.0 were used to analyze and process the experimental data, Duncan's new multiple range method was used to test the significance of differences, and the corrplot package in R language was used to draw the correlation combination heat map.

[0044] 6. Experimental results

[0045] 6.1 Effects of different exogenous calcium treatments on dry matter accumulation of tobacco plants

[0046] The results of the effects of different exogenous calcium treatments on the dry matter accumulation of tobacco plants are shown in Figure 2 As shown in the figure, different exogenous calcium treatments have different effects on the dry matter accumulation of tobacco plants in acidified soil. For the root, all exogenous calcium treatments are higher than the control T1, among which T2 treatment is the highest, followed by T4, and both are significantly higher than the control T1 treatment by 18.62%; for the stem, there is no significant difference between each exogenous calcium treatment and the control T1 treatment; for the leaf, all exogenous calcium treatments are higher than the control T1, among which T2 treatment and control T1 are significantly different, the former is 34.02% higher than the latter; from the perspective of the total dry matter accumulation of a single plant, T2, T4 and T5 treatments are significantly higher than the control T1, among which T2 treatment is the highest, 24.75% higher than the control T1 treatment. In summary, different exogenous calcium applications can increase the dry matter accumulation of tobacco plants and promote the growth of tobacco plants, among which T2 treatment is the best, followed by T4 treatment.

[0047] 6.2 Effects of different exogenous calcium treatments on the mineral element content of tobacco-growing soil

[0048] As can be seen from Table 1 below, the application of different exogenous calcium will lead to changes in the content of mineral elements in tobacco-growing soils, and the change trends of each treatment are inconsistent. Compared with the control T1, the exchangeable Ca content of the soil in the T2 treatment increased significantly by 39.48%, the exchangeable Mg content, effective B and effective S changed slightly, the effective Fe, effective Mo and effective B content increased, but the difference was not significant, and the effective Cu, effective Zn, effective Mn and effective S showed a significant downward trend; T4 and T5 both significantly reduced the content of effective Cu and effective Mn in the soil, and increased the content of effective Fe and effective S. In general, the T2 treatment can quickly increase the content of soil exchangeable calcium. Due to its role in regulating soil pH, it promotes the deacidification of the Masha mud field soil, resulting in a decrease in the biological effectiveness of some mineral element ions, which may be one of the important reasons for the decrease in the effective state content of elements such as effective Cu, effective Zn, effective Mn and effective S in the soil of this treatment.

[0049]

[0050] Table 1 Contents of mineral elements in tobacco-growing soils treated with different exogenous calcium

[0051] 6.3 Effects of different exogenous calcium treatments on mineral element content in flue-cured tobacco leaves

[0052] As shown in Table 2 below, compared with the control T1, the T2, T4 and T5 treatments significantly increased the calcium content of tobacco leaves by more than 75.82%. The Mg content of tobacco leaves was highest in the T4 treatment, which was significantly higher than the control T1 treatment by 23.96%, followed by the T2 treatment, and there were no significant differences among the other treatments. The Fe content of tobacco leaves treated with T3 and T5 was significantly lower than that of the control T1, and the content of T2 and T4 was equivalent to that of the control T1. The contents of Cu, Zn, Mn, B and S in tobacco leaves treated with the four calcium sources decreased to varying degrees, among which Cu The content of tobacco leaves decreased by 24.74% to 49.23%, among which the T4 treatment had the largest decrease; the Zn content of tobacco leaves decreased by 28.76% to 42.81%, among which the T3 treatment had the largest decrease; the Mn content of tobacco leaves decreased by 20.08% to 26.70%, among which the T4 treatment had the largest decrease; the B content of tobacco leaves decreased the most in the T3 treatment, reaching 35.63%; the S content of tobacco leaves decreased the most in the T2 treatment, reaching 44.55%, and the other calcium source treatments also decreased significantly. In summary, the application of different calcium sources has a great influence on the content of mineral elements in tobacco leaves after curing. On the whole, except for the T3 treatment, T2, T4 and T5 have greatly increased the calcium content of tobacco leaves. The change rules of Mg, Fe and Mo content of tobacco leaves in each treatment are inconsistent, but the Cu, Zn, Mn and S content of tobacco leaves all show a downward trend, and the decline is more than 20%. The possible reason is that the application of exogenous calcium has an antagonistic effect on the absorption of other elements. In addition, the application of calcium oxide and oyster shell calcium changes the soil pH and the effectiveness of mineral elements, affecting the absorption and utilization of soil mineral elements by tobacco leaves.

[0053] deal with Total calcium g.kg-1 Total magnesium g.kg-1 Total iron mg.kg-1 Total copper mg.kg-1 Total zinc mg.kg-1 Total amount of manganese mg.kg-1 Total amount of molybdenum μg.kg-1 Total boron mg.kg-1 Total sulfur g.kg-1 T1 5.79±1.03b 2.17±0.10b 68.46±2.52ab 3.88±0.25a 51.17±2.00a 108.04±4.49a 1.07±0.10a 49.34±1.91a 6.15±0.19a T2 12.68±1.02a 2.27±0.11ab 69.66±1.37a 2.92±0.23b 39.74±2.14b 84.99±1.59b 1.27±0.11a 41.08±1.83b 3.41±0.23c T3 5.77±0.67b 1.91±0.06b 45.76±1.12c 2.34±0.11b 29.26±1.99c 86.61±3.06b 0.79±0.08b 31.76±0.98c 5.35±0.45b T4 11.44±1.03a 2.69±0.10a 70.10±2.70a 1.97±0.13c 30.72±1.80c 79.46±3.83b 0.91±0.11ab 48.28±2.55a 5.18±0.12b T5 10.18±1.80a 1.98±0.11b 64.78±2.50b 2.65±0.24b 35.16±3.56b 81.90±1.94b 1.19±0.04a 41.67±2.27b 4.85±0.18b

[0054] Table 2 Effects of different calcium source treatments on the mineral element content of flue-cured tobacco leaves

[0055] 6.4 Effects of different exogenous calcium treatments on the color of flue-cured tobacco leaves

[0056] The chromaticity of flue-cured tobacco leaves after different exogenous calcium treatments Figure 3 As shown, there are differences in the color darkness-brightness (L*) values ​​of tobacco leaves among the treatments. The four exogenous calcium treatments are significantly higher than the control T1, among which T2 treatment is the highest, 9.35% higher than the control T1 treatment, followed by T5 and T4. The specific order is T2>T5>T4>T3>T1( Figure 3 a); The green-red value (a*) of the color was highest in T3 treatment, followed by T1 treatment, and lowest in T5 treatment. The specific order was T3>T1>T4>T2>T5( Figure 3 b); The blue-yellow values ​​(b*) of each exogenous calcium treatment were significantly higher than those of the control T1, with the highest value in the T2 treatment, which was 7.70% higher than the control T1 treatment. The specific order was T2>T4>T5>T3>T1( Figure 3c); The gray-saturation values ​​(c*) of each exogenous calcium treatment were significantly higher than those of the control T1, with the highest value in the T2 treatment, which was 5.87% higher than the control T1 treatment. The specific order was T2>T4>T3>T5>T1( Figure 3 d). This shows that exogenous calcium application can improve the brightness, yellowness and purity of the color of flue-cured tobacco leaves, and improve the appearance quality of tobacco leaves in sandy mud fields, among which the effect of T2 treatment is the best.

[0057] 6.5 Effects of different exogenous calcium treatments on pigment content in flue-cured tobacco leaves

[0058] Effects of different exogenous calcium treatments on pigment content in flue-cured tobacco leaves Figure 4 As shown in the figure, the content of leaf green a and leaf green b in the flue-cured tobacco leaves of each treatment was consistent. The content of both in tobacco leaves treated with T2 was significantly lower than that in the control by more than 22.58%, and the content of T3 and T5 was not significantly different from that in the control ( Figure 4 a. Figure 4 b); The carotenoid content of tobacco leaves in T2, T4 and T5 treatments was significantly higher than that in the control treatment, and the content in T3 treatment was slightly higher than that in the control treatment, but the difference between the two was not significant ( Figure 4 c); The β-carotene content of tobacco leaves treated with four exogenous calcium treatments was significantly higher than that of the control T1 treatment by more than 22.59%, among which the content was the highest in T2 treatment and the lowest in T3 treatment ( Figure 4 d). In general, T2 and T4 reduced the contents of green a and green b in flue-cured tobacco leaves and increased the contents of carotenoids and β-carotene, which is one of the important internal reasons why the appearance quality of their tobacco leaves was superior to that of other treatments.

[0059] 6.6 Correlation analysis between the color and mineral element index of flue-cured tobacco leaves

[0060] The results of the correlation between the color and mineral element index of the flue-cured tobacco leaves are as follows: Figure 5 As shown in the figure, the correlation analysis between the color difference of flue-cured tobacco leaves and mineral element indices showed that the dark-brightness (L*) value was significantly correlated with Mn, Cu, Zn and Ca (P<0.05), and was extremely significantly correlated with S (P<0.01); the green-red value (a*) was significantly correlated with Fe, Mo and S (P<0.05), and was extremely significantly correlated with Ca (P<0.01); the blue-yellow value (b*) and the gray-saturation value (c*) were significantly correlated with Cu, Zn and Ca (P<0.05), and were extremely significantly correlated with S (P<0.01). In general, the color difference value of flue-cured tobacco leaves was significantly correlated with most mineral element indices, among which the correlation with S and Ca elements in tobacco leaves was the strongest.

[0061] 6.7 Effects of different exogenous calcium treatments on the appearance quality of flue-cured tobacco leaves

[0062] The results of the effects of different exogenous calcium treatments on the appearance quality of flue-cured tobacco leaves are shown in Table 3 and Figure 6 As shown in the figure, the color, maturity, leaf structure, oil content, chroma and other indicators of the tobacco leaves after the four exogenous calcium treatments were better than those of the Masha mud field control (CK) treatment. Among them, the T2 treatment had the best indicators, followed by the T4 treatment, and the comprehensive scores were 22.95% and 18.11% higher than the control, respectively. The two treatments performed outstandingly in terms of tobacco leaf appearance color, chroma and maturity. From a phenotypic point of view, the control treatment had a better appearance color and a better maturity.

[0063] and chroma are significantly weaker than other treatments ( Figure 6 ), overall, the appearance quality of each treatment is ranked as T2>T4>

[0064] T5>T3>T1(CK).

[0065]

[0066] Table 3 Quantitative evaluation of appearance quality of tobacco leaves treated with different calcium sources

[0067] Based on the above experimental results, the following conclusions can be drawn:

[0068] (1) The calcium oxide + sugar alcohol calcium treatment can quickly increase the content of soil exchangeable calcium. At the same time, the calcium oxide + sugar alcohol calcium treatment and the oyster shell calcium + sugar alcohol calcium treatment both significantly reduced the content of soil available copper, available manganese and available sulfur.

[0069] (2) Both the calcium oxide + sugar alcohol calcium treatment and the oyster shell calcium + sugar alcohol calcium treatment significantly increased the calcium and magnesium content of tobacco leaves, while the copper, zinc, manganese and sulfur contents of the tobacco leaves showed a downward trend.

[0070] (3) Calcium oxide + calcium sugar alcohol treatment reduced the content of green a and green b in flue-cured tobacco leaves and increased the content of carotenoids and β-carotene. Significantly improve the yellowness (b), brightness (L*), and saturation of the color of tobacco leaves after curing in Masha mud fields (C*), improved the fading degree of tobacco leaves in sandy mud fields .

[0071] To this end, the applicant proposed a control method for preventing tobacco leaves from fading after being baked in acidified soil, and the control method is specifically as follows:

[0072] S1: Select a suitable type of calcium fertilizer according to the acidity and alkalinity of the acidified soil and the needs of flue-cured tobacco, wherein the calcium fertilizer is a combination of calcium oxide (basal application) + calcium nitrate (spraying), calcium oxide (basal application) + sugar alcohol calcium (spraying), oyster shell calcium (basal application) + calcium nitrate (spraying), and oyster shell calcium (basal application) + sugar alcohol calcium (spraying);

[0073] S2: Determine the amount of calcium fertilizer according to the basic fertility of the soil, the tobacco variety and the planting technology, and the calcium fertilizer is used to make the exchangeable calcium content of the acidified soil greater than 6 cmol / kg;

[0074] Among them, the evaluation standard of soil exchangeable calcium abundance and deficiency in tobacco fields (Ca 2+ (cmol / kg)) are shown in Table 4 below:

[0075] grade Very low Low Medium (suitable) high Very high content <3 3～6 6～10 10～18 ≥18

[0076] Table 4

[0077] The evaluation criteria for calcium content in tobacco leaves (g / kg) are shown in Table 5 below:

[0078] grade lack Low suitable high content <12 12～15 15～25 >25

[0079] Table 5

[0080] Recommended calcium oxide dosage for different pH values ​​of acidic sandy loam (kg / hm 2 ) are shown in Table 6 below:

[0081] Soil pH <5.0 5.0-5.5 5.5-6.0 6.0-6.5 Recommended Dosage 1800 1500 900 300

[0082] Table 6

[0083] S3: Apply calcium fertilizer by combining basal fertilizer strip application and foliar spraying as needed;

[0084] Among them, the base fertilizer strip application method is to build ridges before tobacco planting, dig a 15 cm deep strip application furrow along the planting center of the ridge body, sprinkle the calcium fertilizer, and then cover the furrow with soil to restore it, or dig two 10 cm deep strip application furrows on both sides of the land where tobacco is planted, sprinkle the calcium fertilizer, and then level the furrows and build ridges.

[0085] The foliar spraying method is to prepare calcium fertilizer nutrient solution according to the specified concentration, use an electric sprayer, and spray it from bottom to top on the front and back of each leaf and the surface of the stem of the tobacco plant. The spraying time is once every 50 days, 60 days, and 70 days after the tobacco plants are transplanted.

[0086] S4: After the application of calcium fertilizer, timely field management is carried out to promote the full absorption and utilization of calcium fertilizer. The field management includes covering with black and white double-color film, maintaining a 30cm ridge height after soil cultivation, timely removal of residual foot leaves and axillary buds, topping to retain 20 leaves that can be harvested in the end, timely harvesting of tobacco leaves when they mature and turn yellow, and baking according to the standard three-stage baking technology of tobacco leaves. It is also necessary to pay attention to the growth of tobacco and timely supplement other nutrients to ensure the healthy growth of tobacco.

[0087] When calcium oxide is used as calcium fertilizer, the amount of calcium oxide applied is 1500 kg / hm2. 2 , the application method is to use the base fertilizer strip application method;

[0088] When calcium nitrate is used as the exogenous calcium fertilizer, a 0.5% ppm calcium nitrate solution is sprayed once on the 50th, 60th and 70th days after the tobacco plants are transplanted.

[0089] When the applied exogenous calcium is oyster shell calcium, the applied amount of the oyster shell calcium is 1500 kg / hm 2 , the application method is to use the base fertilizer strip application method;

[0090] When the exogenous calcium fertilizer applied is sugar alcohol calcium, a 0.1% ppm concentration of sugar alcohol calcium solution is selected and sprayed once 50 days, 60 days, and 70 days after the tobacco plants are transplanted.

[0091] Compared with the prior art, the present invention promotes the growth of tobacco plants by adding exogenous calcium, increases the calcium content in acidic soil and tobacco leaves, reduces the content of mineral elements such as copper, zinc, manganese, and sulfur, improves the appearance color of tobacco leaves, and significantly improves the ability of tobacco leaves to resist fading after curing, among which the calcium oxide + sugar alcohol calcium treatment has the best effect.

[0092] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A method for preventing tobacco leaves from fading after being cured in acidified soil, characterized in that: The steps include: S1: Choose the appropriate type of calcium fertilizer according to the acidity and alkalinity of the acidified soil and the needs of flue-cured tobacco; S2: Determine the amount of calcium fertilizer based on the basic fertility of the soil, tobacco variety and planting technology; S3: Apply calcium fertilizer by combining basal fertilizer strip application and foliar spraying as needed; S4: After applying calcium fertilizer, carry out field management in a timely manner to promote the full absorption and utilization of calcium fertilizer.

2. The control method according to claim 1, characterized in that: The calcium fertilizer in step S1 is a calcium fertilizer combination selected from the group consisting of calcium oxide (basal application) + calcium nitrate (spraying), calcium oxide (basal application) + sugar alcohol calcium (spraying), oyster shell calcium (basal application) + calcium nitrate (spraying), and oyster shell calcium (basal application) + sugar alcohol calcium (spraying).

3. The control method according to claim 1, characterized in that: In S2, the calcium content of the soil can be understood through soil testing, so as to determine a reasonable amount of calcium fertilizer. After the calcium fertilizer is used, the exchangeable calcium content of the acidified soil is greater than 6 cmol / kg.

4. The control method according to claim 1, characterized in that: The strip application method of the base fertilizer in S3 is to make ridges before tobacco planting, dig a strip application furrow with a depth of 15 cm downward along the planting center of the ridge body, sprinkle the calcium fertilizer, and then cover the furrow with soil to restore it, or dig two strip application furrows with a depth of about 10 cm on both sides of the land where tobacco is planted, sprinkle the calcium fertilizer, and then level the furrows and make ridges.

5. The control method according to claim 1, characterized in that: The foliar spraying method in S3 is to prepare calcium fertilizer nutrient solution according to the specified concentration, use an electric sprayer, and spray it from bottom to top on the front and back of each leaf and the surface of the stem of the tobacco plant. The spraying time is once every 50 days, 60 days, and 70 days after the tobacco plant is transplanted.

6. The control method according to claim 1, characterized in that: The S4 field management includes covering with black and white double-color mulch, maintaining a 30cm ridge height after soil cultivation, timely removal of residual foot leaves and axillary buds, topping to retain 20 leaves that can be harvested in the end, timely harvesting of tobacco leaves when they are mature and yellow, and baking according to the standard three-stage baking technology of tobacco leaves.

7. Use of the method for preventing tobacco leaves from fading after being baked in acidified soil according to any one of claims 1 to 6 in tobacco planting.

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