A three-time harvesting method for flue-cured tobacco after rice stubble

Abstract

The present invention belongs to the technical field of tobacco harvesting and curing. The present invention relates to a three-time harvesting method for flue-cured tobacco after rice stubble, comprising: determining the reference leaves to be harvested each time; recording the number of leaves that meet the mature appearance characteristics as the planned number of leaves to be harvested; determining the SPAD values ​​of the reference leaves and the planned harvested tobacco leaves, and determining the actual number of harvested leaves according to the difference D between the SPAD values ​​of the planned harvested tobacco leaves and the reference leaves. The present invention first makes a preliminary judgment on the mature appearance characteristics of the tobacco leaves to be harvested, and then uses an instrument to detect when the tobacco leaves to be harvested reach certain mature appearance characteristics, and uses a combination of qualitative and quantitative methods to make a judgment, which solves the problem that there are no clear indicators and quantitative indicators in the mature harvesting process of multiple flue-cured tobacco leaves, and achieves the purpose of accurately determining the maturity of fresh tobacco leaves while reducing the number of SPAD value determinations, thereby also improving the rate and average price of tobacco leaves, the sensory evaluation and smoking quality of tobacco leaves, and the planting benefits.

Description

Technical Field

[0001] The invention relates to the technical field of tobacco harvesting and curing, and in particular to a three-time harvesting method for flue-cured tobacco after rice stubble. Background Art

[0002] In the process of tobacco leaf curing, harvesting is the basis and curing is the key. The traditional requirement for flue-cured tobacco harvesting in my country is "picking one leaf at a time when it is mature". The number of harvesting and curing of flue-cured tobacco in the field is generally as many as 6-8 times, which has high labor intensity and labor costs. With the continuous increase in labor costs, reducing labor, improving the comprehensive benefits of harvesting and curing, and reducing the number of harvesting and curing have become an inevitable trend. According to existing research reports, Jin Kang et al. believe that reducing the number of tobacco harvesting and curing times in Mudanjiang tobacco area to 4 times can increase the output value of tobacco leaves and make the internal chemical composition of tobacco leaves more coordinated (Jin Kang et al., Effects of different harvesting times on tobacco yield and quality, Anhui Agricultural Science Bulletin, 2021); Liang Zhu et al. believe that reducing the number of tobacco harvesting times in Changsha rice stubble to 5 times compared with 7 times can increase the proportion of high-quality tobacco and increase economic benefits (Liang Zhu et al., Effects of different harvesting and curing times on tobacco leaf yield, quality and benefits, Hunan Agricultural Science, 2021); Zhang Guo et al. adopted the "3 rounds, 4 kang times" harvesting and curing technology to improve the maturity and comprehensive benefits of tobacco leaves for tobacco plants with only 12-14 leaves left after optimizing the tobacco leaf structure (Zhang Guo, 3-time harvesting and automated curing technology in southern Anhui tobacco area, Anhui Agricultural Science Bulletin, 2018), but the actual number of harvesting and curing is still 4 times; other reports on reducing the number of tobacco leaf harvesting and curing are mainly concentrated on 5-6 times. It can be seen that the current research on reducing the number of flue-curing times of flue-cured tobacco is mainly focused on 4-6 times of curing, while three-time curing, especially three-time curing of rice-stubble flue-cured tobacco, is still blank.

[0003] The basis for harvesting tobacco leaves in the field is the maturity of fresh tobacco leaves. Harvesting fresh tobacco leaves at the right maturity is a necessary condition for obtaining high-quality tobacco leaves. There are many methods for judging the maturity of fresh tobacco leaves. The method in the United States is to pick fresh tobacco leaves a week in advance and analyze the chemical composition to determine whether the tobacco leaves have reached the appropriate maturity; Japan mainly uses the colorimetric method of colorimetric cards to determine the appropriate maturity of fresh tobacco leaves; China's current method for judging the maturity of field harvesting is mainly the qualitative description of leaf maturity characteristics. Some people in China also use the conductivity, sucrose content, proline content and tissue structure diagnosis method of flue-cured tobacco leaves, the angle between stems and leaves, and the characteristics of reflectance spectra to judge the maturity of tobacco leaves; there are also colorimetric cards (201220189553.2, Flue-cured tobacco upper leaf maturity colorimetric card, China) and SPAD value methods (Li Fulin et al., Quantification of the maturity of fresh tobacco leaves, Tobacco Science and Technology, 2007; CN 102183617A, A method for determining the maturity of flue-cured tobacco leaves at harvest) to judge the maturity of fresh tobacco leaves. These methods or standards for judging the maturity of fresh tobacco leaves are established on the basis of my country's traditional practice of "picking one leaf when mature" or harvesting 2-3 leaves at a time. They are not applicable to judging the maturity of fresh tobacco leaves that are picked and cured three times after rice-stubble.

[0004] Flue-cured tobacco after rice refers to the flue-cured tobacco in the tobacco-rice intercropping model, which is mainly found in the rainy tobacco-growing areas in the south. In recent years, tobacco-growing areas have promoted and optimized the structure of tobacco leaves, and the number of leaves left in flue-cured tobacco after rice has been decreasing, generally 15-18 leaves, which provides conditions for reducing the number of harvesting and curing. In order to solve the contradiction of tight labor during harvesting and curing, and to better promote mechanized harvesting and curing technology, it is of great significance to develop three-time harvesting and curing technology. The yellowing and maturity of tobacco leaves is layered from bottom to top. There are three harvesting and curing, and the number of leaves harvested each time is 3-8. The maturity of each tobacco leaf is also inconsistent, and the fresh tobacco leaf maturity determination method of "picking one leaf when mature" cannot be applied. There has always been a blank in the three harvesting and curing, how many tobacco leaves are picked each time, and how to accurately judge the appropriate maturity of fresh tobacco leaves during the picking period, which is also a problem that needs to be solved. Summary of the invention

[0005] In view of the defects of the existing flue-cured tobacco production process, such as the high number of harvesting and curing times and the high labor cost, and the drawback of subjectively determining the number of leaves harvested each time and the harvesting maturity only based on experience when harvesting multiple tobacco leaves, the purpose of the present invention is to provide a three-harvesting method for flue-cured tobacco from rice stubble, including the determination of the suitable maturity of fresh tobacco leaves and the determination of the number of leaves harvested each time, the number of leaves harvested each time and the suitable maturity of the harvest are comprehensively determined through sensory recognition and instrument detection data, the harvesting maturity and the number of leaves harvested of fresh tobacco leaves for three harvests are accurately determined, and the tobacco yield and quality and the efficiency of flue-cured tobacco planting are improved.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The invention provides a three-time harvesting method of flue-cured tobacco after rice stubble, comprising the following steps:

[0008] The number of leaves that meet the mature appearance characteristics is recorded as the number of leaves planned to be harvested;

[0009] Determine the SPAD values ​​of the reference leaves and the planned tobacco leaves to be harvested, and determine the actual number of leaves to be harvested according to the difference D between the SPAD values ​​of the planned tobacco leaves to be harvested and the reference leaves;

[0010] At the first harvest, the mature appearance characteristics are as follows: the leaves are light green, the main veins are light green to white 25-35%, and the leaf edges are curled;

[0011] At the second harvest, the mature appearance characteristics are as follows: the leaves turn yellow 20-70%, the main veins turn white 35-100%, and the side veins turn white 25-100%;

[0012] At the third harvest, the mature appearance characteristics are as follows: the leaf surface turns yellow 50-80%, the main vein turns white 50-80%, the side veins turn white 30-50%, the hairs fall off, and there are mature spots;

[0013] In the three harvests, the third effective tobacco leaf from the bottom of the tobacco plant is used as the reference leaf each time;

[0014] Each time the leaves are harvested, when the D value is between -1 and 1, the planned number of leaves harvested is taken as the actual number of leaves harvested; when the D value is less than -1, the actual number of leaves harvested is taken as the planned number of leaves harvested plus 1; when the D value is greater than 1, the actual number of leaves harvested is taken as the planned number of leaves harvested minus 1.

[0015] Preferably, the SPAD value of the tobacco leaves planned to be harvested is: the average SPAD value of all the tobacco leaves planned to be harvested at each harvest.

[0016] Preferably, at the first harvest, the benchmark leaf SPAD value is 26±1; at the second harvest, the benchmark leaf SPAD value is 25±1; at the third harvest, the benchmark leaf SPAD value is 24±2.

[0017] Preferably, when determining the SPAD value of a reference leaf, ≥ 10 tobacco leaves are measured, and each tobacco leaf is divided into 3 sections, namely the leaf base, the middle part of the leaf, and the leaf tip. One point is selected from the middle of each section, 3 cm away from the main vein on both sides and symmetrically on the leaf blade, for measurement. The average value of all the measuring points is the SPAD value of the reference leaf.

[0018] Preferably, when the total number of effective leaves is 15, the number of leaves actually harvested for the first time is 3, the number of leaves actually harvested for the second time is 6, and the number of leaves actually harvested for the third time is 6.

[0019] Preferably, when the total number of effective leaves is 16, the number of leaves actually harvested for the first time is 4, the number of leaves actually harvested for the second time is 6, and the number of leaves actually harvested for the third time is 6.

[0020] Preferably, when the total number of effective leaves is 17, the number of leaves actually harvested for the first time is 4, the number of leaves actually harvested for the second time is 6, and the number of leaves actually harvested for the third time is 7.

[0021] Preferably, when the total number of effective leaves is 18, the number of leaves actually harvested for the first time is 4, the number of leaves actually harvested for the second time is 6, and the number of leaves actually harvested for the third time is 8.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects:

[0023] 1. The present invention adopts a method combining qualitative and quantitative methods, and uses a SPAD instrument to accurately determine the relative content of chlorophyll in tobacco leaves, which solves the technical defect that the harvesting of multiple tobacco leaves in the prior art mainly depends on the experience of planting technicians to make judgments, and accurate harvesting cannot be achieved. Through subjective and objective comprehensive judgments, the purpose of accurately determining the maturity of fresh tobacco leaves is achieved while reducing the number of SPAD value measurements.

[0024] 2. The method of the present invention solves the problem of no clear and quantitative indicators in the process of mature harvesting of multiple flue-cured tobacco leaves, improves the operability and accuracy of judging mature tobacco leaves, is more targeted, regular and comprehensive, and is easier to operate and master.

[0025] 3. The method of the present invention is used to determine the appropriate maturity of three harvests of flue-cured tobacco after rice stubble, which can reduce the labor required for harvesting and curing and the proportion of green and mixed tobacco leaves in the cured tobacco leaves, thereby increasing the rate of high-quality tobacco leaves and the average price, as well as the sensory evaluation quality of tobacco leaves, and ultimately improving the planting benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The grouping of flue-cured tobacco leaves with different harvest times;

[0027] Figure 2 To evaluate the smoking quality of flue-cured tobacco leaves harvested at different times. DETAILED DESCRIPTION

[0028] The invention provides a three-time harvesting method for flue-cured tobacco after rice stubble, comprising the following steps: recording the number of leaves meeting mature appearance characteristics as the planned number of leaves to be harvested; measuring SPAD values ​​of reference leaves and the planned tobacco leaves to be harvested, and determining the actual number of leaves to be harvested according to the difference D between the SPAD values ​​of the planned tobacco leaves to be harvested and the reference leaves.

[0029] In the present invention, the three harvestings are preferably a first harvesting of tobacco leaves at the bottom of the tobacco plant, a second harvesting of tobacco leaves at the middle of the tobacco plant, and a third harvesting of tobacco leaves at the top of the tobacco plant.

[0030] In the present invention, when harvested for the first time, the mature appearance characteristics are as follows: the leaves are light green, the main veins are light green to white 25-35%, and the leaf edges are curled; when harvested for the second time, the mature appearance characteristics are as follows: the leaf surface turns yellow 20-70%, the main veins turn white 35-100%, and the side veins turn white 25-100%; when harvested for the third time, the mature appearance characteristics are as follows: the leaf surface turns yellow 50-80%, the main veins turn white 50-80%, the side veins turn white 30-50%, the hairs fall off, and there are mature spots.

[0031] In the present invention, after determining the planned number of leaves to be harvested each time based on the mature appearance characteristics, the SPAD values ​​of the reference leaves and the planned tobacco leaves to be harvested are determined. In the present invention, the third effective tobacco leaf from the bottom of the tobacco plant is preferably used as the reference leaf for each harvest. The present invention preferably uses a SPAD instrument (soil plant analysis development) to determine the tobacco leaf SPAD value of the reference leaf, and preferably performs the measurement at 9:00-10:00 in the morning. When determining the SPAD value of the reference leaf, the number of tobacco leaves to be measured is preferably ≥10, mainly because the maturity of field tobacco leaves varies greatly, and the measurement error is reduced; each tobacco leaf is divided into 3 sections on average, namely the base of the leaf, the middle of the leaf, and the tip of the leaf. One point is selected from both sides of the main vein 3 cm away from the middle of each section and at the symmetric part of the leaf for measurement. This is also because the maturity of the same leaf varies greatly, and multi-point detection reduces the measurement error; all measuring points are required to avoid the leaf veins, and the average value of all measuring points is the SPAD value of the reference leaf, recorded as S 基准叶 .

[0032] In the present invention, the SPAD value of the reference leaf is 26±1 at the first harvest; the SPAD value of the reference leaf is 25±1 at the second harvest; and the SPAD value of the reference leaf is 24±2 at the third harvest. The reference leaf in the present invention is the third effective leaf in each harvest, and the determination of the SPAD values ​​of the three reference leaves is the result obtained after many years of multi-variety experiments. 基准叶 ±1 (or 2) varies according to the variety, fertilization level, and individual requirements of cigarette brand raw materials. Generally, for varieties with strong maturity resistance and fields with low fertilization levels, the SPAD value of the reference leaf can be lower; for varieties with weak maturity resistance and fields with high fertilization levels, the SPAD value of the reference leaf can be higher. The SPAD value of the reference leaf in the present invention is higher than that studied by others in the past. The main reason is that the number of leaves harvested each time is large. Appropriately reducing the maturity of the reference leaf is beneficial to reducing the maturity difference of the harvested tobacco leaves, which is beneficial to reducing the proportion of green and mixed tobacco leaves.

[0033] In the present invention, the SPAD value of the planned tobacco leaves to be harvested is the average value of the SPAD values ​​of all the planned tobacco leaves to be harvested at each harvest, denoted as S 平均值 The present invention also uses a SPAD instrument to measure the SPAD value of the planned tobacco leaves to be harvested. The specific measurement requirements and methods are the same as those for measuring the SPAD value of the reference leaf. The SPAD values ​​of the planned number of leaves to be harvested (n) are respectively recorded as S1, S2, S3, ..., Sn; the SPAD value of the planned tobacco leaves to be harvested (S 平均值 ) is calculated as:

[0034] In the present invention, D is calculated based on the SPAD values ​​of the planned harvested tobacco leaves and the reference leaves, and the actual number of harvested leaves is determined. The D calculation formula is: D = S 平均值 -S基准叶 The judgment of the actual number of leaves harvested in the present invention is preferably as follows: each time the leaves are harvested, when the D value is between -1 and 1, the planned number of leaves harvested is used as the actual number of leaves harvested; when the D value is less than -1, the planned number of leaves harvested plus 1 is used as the actual number of leaves harvested; when the D value is greater than 1, the planned number of leaves harvested minus 1 is used as the actual number of leaves harvested.

[0035] In the present invention, when the total number of effective leaves is 15, the number of leaves actually harvested for the first time is preferably 3, the number of leaves actually harvested for the second time is preferably 6, and the number of leaves actually harvested for the third time is preferably 6.

[0036] In the present invention, when the total number of effective leaves is 16, the number of leaves actually harvested for the first time is preferably 4, the number of leaves actually harvested for the second time is preferably 6, and the number of leaves actually harvested for the third time is preferably 6.

[0037] In the present invention, when the total number of effective leaves is 17, the number of leaves actually harvested for the first time is preferably 4, the number of leaves actually harvested for the second time is preferably 6, and the number of leaves actually harvested for the third time is preferably 7.

[0038] In the present invention, when the total number of effective leaves is 18, the number of leaves actually harvested for the first time is preferably 4, the number of leaves actually harvested for the second time is preferably 6, and the number of leaves actually harvested for the third time is preferably 8.

[0039] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0040] Example 1 Study on the different maturity of Xiangyan No. 7 harvested three times

[0041] 1. Experimental plan

[0042] A three-harvest suitable maturity test of Xiangyan No. 7 was carried out in Guiyang County, Hunan Province. There are three levels of harvest maturity, namely low maturity (M1), medium maturity (M2, determined by the mature appearance characteristics of the present invention), and high maturity (M3). The harvest time interval for each maturity is 7 days. The number of leaves harvested for the first, second, and third time are 4, 6, and 6 tobacco leaves, respectively, recorded as D1-D4, D5-D10, D11-D16, and the reference leaves are D3, D7, and D13, respectively. When harvesting tobacco leaves, 120 tobacco leaves are selected for each leaf position, and the tobacco leaves are put on the pole according to the leaf position, and baked after 3 repetitions.

[0043] The baking adopts a four-step baking process: yellow leaf stage, 50-66h, dry bulb 39-40°C, wet bulb 37-39°C, tobacco leaves are 80-90% yellow, and moisturizing and yellowing is carried out; dry bulb 40°C, wet bulb 35-36°C, leaves are softened and fully collapsed; yellow vein stage, 55h, dry bulb 43°C, wet bulb 35-36°C, water loss reaches the softening of main veins; dry bulb 45°C, wet bulb 35-36°C, yellow leaf and yellow veins; dry leaf stage, 24h, dry bulb 54-55°C, wet bulb 38-39°C, leaves are completely dry; dry vein stage, 24-30h, dry bulb 65°C, wet bulb 40-41°C, main veins are completely dry.

[0044] 2. Test results

[0045] (1) Appearance characteristics of mature fresh tobacco leaves, see Table 1 for details.

[0046] Table 1 Appearance maturity characteristics of fresh tobacco leaves at different harvest maturity

[0047]

[0048]

[0049]

[0050] (2) SPAD value of fresh tobacco leaves. Specific test results are shown in Table 2.

[0051] Table 2 SPAD values ​​of fresh tobacco leaves at different harvest maturity

[0052]

[0053]

[0054] As shown in Table 2, the S 基准叶 is 28.33, which is greater than 1 compared to 26; M2’s S 基准叶 is 26.26, and the difference with 26 is within ±1; the S of M3 基准叶 The SPAD value of M2 is suitable, the maturity of M1 is poor, and M3 is over-mature. 基准叶 is 27.68, which is greater than 1 compared to 25; M2’s S 基准叶 is 25.59, and the difference with 25 is within ±1; the S of M3 基准叶 The SPAD value of M2 is suitable, the maturity of M1 is poor, and M3 is over-mature. 基准叶 is 29.45, which is greater than 2 from 24; M2's S 基准叶 is 24.04, and the difference with 24 is within ±1; the S of M3基准叶 It is 15.71, and the difference with 24 is less than 2; it can be seen that the SPAD value of M2 is appropriate, the maturity of M1 is poor, and M3 is overmature.

[0055] (3) Statistics of flue-cured tobacco leaves grouped

[0056] The statistical statistics of the proportions of normal, variegated and slightly green in the flue-cured tobacco leaves with different harvest times and different maturity treatments are shown in Table 3.

[0057] Table 3 Statistics of groups of flue-cured tobacco leaves at different harvest maturity

[0058]

[0059] As shown in Table 3, the first harvest of M1 treatment had some slightly green tobacco leaves, and M3 treatment had a higher proportion of variegated tobacco leaves. The second harvest of M1 and M2 treatments had some slightly green tobacco leaves, but M1 treatment had relatively more; M3 treatment had a higher proportion of variegated tobacco leaves; the third harvest of M1 and M2 treatments had some slightly green tobacco leaves, but M1 treatment had relatively more; M3 treatment had a higher proportion of variegated tobacco leaves. Overall, M2 treatment had the highest proportion of positive tobacco leaves, and the proportion of variegated and slightly green tobacco leaves was relatively small.

[0060] (4) Chemical composition of flue-cured tobacco leaves

[0061] Table 4 Chemical components of flue-cured tobacco leaves at different harvest maturity

[0062]

[0063] As shown in Table 4, from the first harvest, except for the low ratio of sugars in M1, other chemical composition indicators are within the appropriate range; with the increase of harvest maturity, the total sugar and reducing sugar content of tobacco leaves increased, the nicotine content increased, the sugar ratio increased, and the nitrogen-base ratio decreased. From the second harvest, with the increase of maturity, the total sugar content showed an upward trend, the reducing sugar content first decreased and then increased, the nicotine content first increased and then decreased, the total nitrogen content decreased slightly, the starch content first increased and then decreased, and the sugar ratio did not change significantly with maturity; with the increase of maturity, the sugar-base ratio increased slightly, and except for M3, they were all within the appropriate range, and the nitrogen-base ratio did not change significantly with maturity. From the third harvest, the differences in different chemical composition indicators were not significant; in general, the changes in various chemical components were not significant. Overall, the chemical composition of M2 is relatively coordinated.

[0064] (5) Sensory evaluation of smoking quality of flue-cured tobacco leaves

[0065] Table 5 Total sensory scores of flue-cured tobacco leaves at different harvest maturity

[0066]

[0067] As shown in Table 5, in the first harvest, the total sensory score of M2 was 20.91% and 50.45% higher than that of M1 and M3, respectively. In the second harvest, the total sensory score of M2 was 23.26% and 15.50% higher than that of M1 and M3, respectively. In the third harvest, the total sensory score of M2 was 11.55% and 8.90% higher than that of M1 and M3, respectively. It can be seen that the sensory quality of M2 treatment is the best.

[0068] (6) Economic characteristics of flue-cured tobacco leaves

[0069] Table 6 The percentage and average price of high-quality tobacco leaves after flue-cured tobacco leaves at different harvest maturity

[0070]

[0071]

[0072] As shown in Table 6, in the first harvest, the rate of M2 high-quality tobacco was 13.80 and 14.67 percentage points higher than that of M1 and M3, respectively; the average price of M2 was 16.13% and 27.13% higher than that of M1 and M3, respectively. In the second harvest, the rate of M2 high-quality tobacco was 3.29 and 17.30 percentage points higher than that of M1 and M3, respectively; the average price of M2 was 1.00% and 12.63% higher than that of M1 and M3, respectively. In the third harvest, the rate of M2 high-quality tobacco was 6.27 and 17.74 percentage points higher than that of M1 and M3, respectively; the average price of M2 was 5.63% and 14.56% higher than that of M1 and M3, respectively. It can be seen that the rate of high-quality tobacco and the average price of M2 were the highest.

[0073] Based on the above analysis, Xiangyan No. 7 was harvested three times. The tobacco leaf harvesting maturity discrimination method of the present invention can increase the proportion of regular tobacco leaves and reduce the proportion of green and mixed tobacco leaves; it can make the chemical composition of tobacco leaves more coordinated and improve the smoking quality of tobacco leaves after curing; it can increase the rate of high-quality tobacco and the average price, and improve the efficiency of tobacco leaf cultivation.

[0074] Example 2 Study on different maturity of Yunyan 87 harvested three times

[0075] 1. Experimental plan

[0076] A three-harvest suitable maturity test of Yunyan 87 was carried out in Guiyang County, Hunan Province. There are three levels of harvest maturity, namely low maturity (M1), medium maturity (M2, determined by the mature appearance characteristics of the present invention), and high maturity (M3). The harvest time interval for each maturity is 7 days. The number of leaves harvested for the first, second, and third time are 4, 6, and 6 tobacco leaves, respectively, recorded as D1-D4, D5-D10, D11-D16, and the reference leaves are D3, D7, and D13, respectively. When harvesting tobacco leaves, 120 tobacco leaves are selected for each leaf position, and the tobacco leaves are put on the pole and braided according to the leaf position. After 3 repetitions, they are baked.

[0077] The baking adopts a four-step baking process: yellow leaf stage, 50-66h, dry bulb 39-40°C, wet bulb 37-39°C, tobacco leaves are 80-90% yellow, and moisturizing and yellowing is carried out; dry bulb 40°C, wet bulb 35-36°C, leaves are softened and fully collapsed; yellow vein stage, 55h, dry bulb 43°C, wet bulb 35-36°C, water loss reaches the softening of main veins; dry bulb 45°C, wet bulb 35-36°C, yellow leaf and yellow veins; dry leaf stage, 24h, dry bulb 54-55°C, wet bulb 38-39°C, leaves are completely dry; dry vein stage, 24-30h, dry bulb 65°C, wet bulb 40-41°C, main veins are completely dry.

[0078] 2. Test results

[0079] (1) Appearance characteristics of mature fresh tobacco leaves, see Table 7 for details.

[0080] Table 7 Appearance maturity characteristics of fresh tobacco leaves at different harvest maturity

[0081]

[0082]

[0083]

[0084] (2) SPAD value of fresh tobacco leaves

[0085] Table 8 SPAD values ​​of fresh tobacco leaves at different harvest maturity

[0086]

[0087] From Table 8, we can see that the S 基准叶 is 28.90, which is greater than 1 compared to 26; M2’s S 基准叶 is 25.95, and the difference with 26 is within ±1; the S of M3 基准叶 The SPAD value of M2 is suitable, the maturity of M1 is poor, and M3 is over-mature. 基准叶 is 27.65, which is greater than 1 compared to 25; M2’s S 基准叶 is 25.55, and the difference with 25 is within ±1; the S of M3 基准叶 The SPAD value of M2 is suitable, the maturity of M1 is poor, and M3 is over-mature. 基准叶 is 31.54, which is greater than 2 when compared to 24; 基准叶 is 24.87, and the difference with 24 is within ±1; the S of M3 基准叶It is 19.65, and the difference with 24 is less than 2; it can be seen that the SPAD value of M2 is appropriate, the maturity of M1 is poor, and M3 is overmature.

[0088] (3) Statistics of flue-cured tobacco leaves grouped

[0089] The statistical statistics of the proportions of normal, variegated and slightly green in the flue-cured tobacco leaves with different harvest times and different maturity treatments are shown in Table 9.

[0090] Table 9 Statistics of groups of flue-cured tobacco leaves at different harvest maturity

[0091]

[0092] As shown in Table 9, in the first harvest, there were some slightly green tobacco leaves in the M1 and M2 treatments, but the M1 treatment had relatively more leaves; the M3 treatment had a higher proportion of variegated tobacco leaves. In the second harvest, there were some slightly green tobacco leaves in the M1 and M2 treatments, but the M1 treatment had relatively more leaves; the M3 treatment had a higher proportion of variegated tobacco leaves; in the third harvest, there were some slightly green tobacco leaves in the M1, M2, and M3 treatments, but the M1 treatment had relatively more leaves; the M3 treatment had a higher proportion of variegated tobacco leaves. In general, the M2 treatment had the highest proportion of normal tobacco leaves, and the proportion of variegated and slightly green tobacco leaves was relatively small.

[0093] (4) Chemical composition of flue-cured tobacco leaves

[0094] Table 10 Chemical components of flue-cured tobacco leaves at different harvest maturity

[0095]

[0096] From the availability index of tobacco chemical components in Table 10, we can see that from the first harvest, M2 is 4.78% and 5.16% higher than M1 and M3, respectively. From the second harvest, M3 and M2 are 12.54% and 12.37% higher than M1, respectively, and M3 and M2 are significantly higher than M1. From the third harvest, M2 is 30.86% and 4.55% higher than M1 and M3, respectively. In general, the availability index of chemical components of M2 is relatively good.

[0097] (5) Sensory evaluation of smoking quality of flue-cured tobacco leaves

[0098] Table 11 Total sensory scores of flue-cured tobacco leaves at different harvest maturity

[0099]

[0100]

[0101] As shown in Table 11, in the first harvest, the total sensory evaluation score of M2 was 2.46% and 11.11% higher than that of M1 and M2, respectively. In the second harvest, the total sensory evaluation score of M1 and M2 was 4.86% and 5.42% higher than that of M3, respectively. In the third harvest, the sensory evaluation score of M2 was 10.12% and 0.50% higher than that of M1 and M3, respectively. It can be seen that the sensory evaluation quality of M2 treatment is the best.

[0102] (6) Economic characteristics of flue-cured tobacco leaves

[0103] Table 12 The percentage and average price of high-quality tobacco leaves after flue-cured tobacco leaves at different harvest maturity

[0104]

[0105] As shown in Table 12, in the first harvest, the high-middle tobacco rate of different maturity treatments was M2>M1>M3, and M2 was 4.51% and 5.49% higher than M1 and M3, respectively, and reached a significant level; the average price of different maturity treatments was M2>M1>M3, and M2 was 4.52% and 15.49% higher than M1 and M3, respectively, and M2 was significantly higher than M3. In the second harvest, the high-quality tobacco rate of different maturity treatments was M2>M1>M3, and M2 was significantly higher than M1 and M3, at 8.66% and 13.89% respectively; the average price was M2>M1>M3, and M1 and M2 were significantly higher than M3, and M1 and M2 were 6.24% and 10.83% higher than M3, respectively. In the third harvest, the percentage of high-quality tobacco in different maturity treatments was M2>M3>M1, and M2 was 45.22% and 7.82% higher than M1 and M3, respectively, and M2 was significantly higher than M1; the average price was 8.62% and 6.26% higher than the average of M1 and M3, respectively, and M2 was significantly higher than M1. It can be seen that the percentage of high-quality tobacco and the average price of M2 treatment were the highest.

[0106] Based on the above analysis, Yunyan 87 was harvested three times. The tobacco leaf harvesting maturity discrimination method of the present invention can increase the proportion of regular tobacco leaves and reduce the proportion of green and mixed tobacco leaves; it can make the chemical composition of tobacco leaves more coordinated and improve the smoking quality of tobacco leaves after curing; it can increase the rate of high-quality tobacco and the average price, and improve the benefits of tobacco leaf cultivation.

[0107] Example 3 Evaluation of the effect of roasting technology based on three harvests

[0108] 1. Experimental plan

[0109] The experimental variety is the flue-cured tobacco variety Yunyan 87, and the number of effective leaves after optimizing the number of tobacco leaves is 16. The experimental location is Guiyang County, Chenzhou City, Hunan Province.

[0110] Experimental plan (1) Survey of typical farmers: A survey method of fixed-point and fixed-farmer was adopted. Four harvesting methods were set up, namely 3, 4, 5, and 6 harvests. 3-5 tobacco farmers were surveyed for each method, and the baking costs of different harvesting and baking times were calculated.

[0111] Experimental plan (2) The experiment has two treatments, T1, 3 harvesting and curing; T2, 5 harvesting and curing. T1: 4 leaves harvested for the first time, 6 leaves harvested for the second time, and 6 leaves harvested for the third time; T2: 3-4 leaves harvested for the first time, 3-4 leaves harvested for the second time, 3-4 leaves harvested for the third time, 3-4 leaves harvested for the fourth time, and 3-4 leaves harvested for the fifth time. According to the different treatments, 40 representative flue-cured leaves of each treatment were selected for physical property measurement, chemical composition analysis, and appearance quality and sensory quality evaluation.

[0112] 2. Test results

[0113] (1) Baking cost of different harvest times

[0114] The labor cost of harvesting is 1,800 yuan / time / curing room, the energy cost of each curing room is 1,300 yuan / time / curing room, and the salary of the curing technician is 280 yuan / time / curing room. At present, the number of leaves that can be harvested and cured in Guiyang tobacco area is 14-16 pieces, and the tobacco loading volume per curing is 350 rods. According to the survey results, the average per kang per curing room for 3 harvests is 14 mu, the average per kang per curing room for 4 harvests is 16 mu, the average per kang per curing room for 5 harvests is 18 mu, and the average per kang per curing room for 6 harvests is 2 mu. The cost and benefit analysis of harvesting and curing under different treatments is shown in Table 13.

[0115] Table 13 The benefits of harvesting and roasting at different harvesting and roasting times

[0116]

[0117] According to the data in the table, the total cost of 3rd, 4th, 5th and 6th harvesting and curing is 724.28 yuan / mu, 845.00 yuan / mu, 938.89 yuan / mu and 1014.00 yuan / mu respectively; the total cost of 3rd, 4th and 5th harvesting and curing is 289.72 yuan / mu, 169.00 yuan / mu and 75.11 yuan / mu less than that of 6th harvesting and curing (CK), and the cost decreases by 28.57%, 16.67% and 7.41% respectively.

[0118] (2) Grouping statistics of flue-cured tobacco leaves at different harvest times

[0119] Depend on Figure 1 It can be seen that the proportion of regular tobacco leaves harvested 3 times is 3.1% higher than that harvested 5 times, the proportion of variegated tobacco is 1.84% lower than that harvested 5 times, and the proportion of slightly green tobacco is 1.26% lower than that harvested 5 times. The main reason for this difference is that the lower tobacco leaves harvested 5 times are more mature.

[0120] (3) Appearance quality of flue-cured tobacco leaves at different harvest times

[0121] Table 14 Appearance quality of tobacco leaves after different harvesting and curing times

[0122]

[0123] As shown in Table 14, the difference in appearance quality of tobacco leaves with different harvesting and curing times is mainly reflected in the lower tobacco leaves. The looseness of tobacco leaves harvested 3 times is slightly worse than that of tobacco leaves harvested 5 times, but the oil content is slightly higher than that of tobacco leaves harvested 5 times. In general, the appearance quality of tobacco leaves harvested 5 times is better than that of tobacco leaves harvested 3 times.

[0124] (4) Physical properties of flue-cured tobacco leaves at different harvest times

[0125] Table 15 Physical properties of tobacco leaves at different harvest times

[0126]

[0127] As shown in Table 15, the differences in the physical properties of tobacco leaves harvested at different times are mainly in the two indicators of single leaf weight and leaf quality weight. From the perspective of the lower tobacco leaves, the leaf quality weight of the 3rd harvest is significantly higher than that of the 5th harvest; from the perspective of the middle and upper tobacco leaves, the single leaf weight and leaf quality weight of the 3rd harvest are significantly higher than those of the 5th harvest. The main reason for this difference is that the number of leaves harvested each time in the 3rd harvest treatment is large. In order to take care of the uniformity of harvest maturity, the maturity of tobacco leaves harvested in the field is slightly lower, and its dry matter consumption is relatively small, resulting in single leaf weight and leaf quality weight higher than those of the 5th harvest treatment.

[0128] (5) Conventional chemical components of flue-cured tobacco leaves at different harvest times

[0129] Table 16 Conventional chemical components of tobacco leaves harvested at different times

[0130]

[0131] As shown in Table 16, the differences in conventional chemical composition of tobacco leaves harvested at different times are mainly in the upper tobacco leaves. From the upper tobacco leaves, the total sugar and reducing sugar content of tobacco leaves harvested 3 times are significantly higher than those harvested 5 times, and the nicotine content is significantly lower than that harvested 5 times. The main reason for this difference is that the upper 6 leaves of tobacco leaves harvested 3 times were harvested at one time, and in order to take care of the uniformity of harvest maturity, the maturity of tobacco leaves harvested in the field is slightly lower.

[0132] (6) Sensory evaluation of smoking quality of flue-cured tobacco leaves at different harvest times

[0133] Depend on Figure 2 It can be seen that the smoking quality of the lower and middle tobacco leaves harvested at different times is slightly lower than that of the 5th harvest, but the difference is not significant. The smoking quality of the upper tobacco leaves harvested at different times is slightly higher than that of the 5th harvest, but the difference is not significant. In other words, 3 harvests will not affect the smoking quality of tobacco leaves.

[0134] (7) Economic characteristics of flue-cured tobacco leaves at different harvest times

[0135] Table 17 Economic characteristics of different harvest times

[0136]

[0137] As shown in Table 17, the rate of high-quality tobacco in the third harvest was 2.96 percentage points lower than that in the fifth harvest, but the difference was not significant; the average price in the third harvest was 1.69 percentage points lower than that in the fifth harvest, but the difference was not significant; the yield in the third harvest was 8.63% higher than that in the fifth harvest, with a significant difference; the output value in the third harvest was 3.08% higher than that in the fifth harvest, with a significant difference. It can be seen that the third harvest can increase the yield and output value of tobacco leaves.

[0138] (8) Comprehensive evaluation of economic effects of different harvesting times

[0139] Table 18 Economic effect evaluation of different harvest times

[0140]

[0141] As shown in Table 18, the cost of three harvesting and curing can save 214.61 yuan / mu compared with five harvesting and curing, increase the output value by 146.70 yuan / mu, increase the net output value9 (income of tobacco farmers) by 361.31 yuan / mu, and increase the income of tobacco farmers by 19.86%.

[0142] It can be seen from the above embodiments that the three-harvesting method for flue-cured tobacco after rice stubble provided by the present invention includes the determination of the appropriate maturity of fresh tobacco leaves and the determination of the number of leaves harvested each time, and adopts a combination of qualitative and quantitative methods to comprehensively determine the number of leaves harvested each time and the appropriate maturity of the harvest through sensory identification and instrument detection data, thereby reducing the number of SPAD value measurements while achieving the purpose of accurately determining the maturity of fresh tobacco leaves at harvest, and also improving the rate and average price of high-quality tobacco leaves, the sensory evaluation quality of tobacco leaves, and the planting benefits.

[0143] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A three-time harvesting method for flue-cured tobacco after rice stubble, characterized in that: The following steps are involved: The number of leaves that meet the mature appearance characteristics is recorded as the number of leaves planned to be harvested; Determine the SPAD values ​​of the reference leaves and the planned tobacco leaves to be harvested, and determine the actual number of leaves to be harvested according to the difference D between the SPAD values ​​of the planned tobacco leaves to be harvested and the reference leaves; At the first harvest, the mature appearance characteristics are as follows: the leaves are light green, the main veins are light green to white 25-35%, and the leaf edges are curled; At the second harvest, the mature appearance characteristics are as follows: the leaf surface turns yellow 20-70%, the main vein turns white 35-100%, and the side veins turn white 25-100%; At the third harvest, the mature appearance characteristics are as follows: the leaf surface turns yellow 50-80%, the main vein turns white 50-80%, the side veins turn white 30-50%, the hairs fall off, and there are mature spots; In the three harvests, the third effective tobacco leaf from the bottom of the tobacco plant is used as the reference leaf each time; Each time when harvesting, when the D value is between -1 and 1, the planned number of leaves to be harvested is taken as the actual number of leaves to be harvested; when the D value is less than -1, the planned number of leaves to be harvested plus 1 is taken as the actual number of leaves to be harvested; when the D value is greater than 1, the planned number of leaves to be harvested minus 1 is taken as the actual number of leaves to be harvested; At the first harvest, the baseline leaf SPAD value was 26 ± 1; At the second harvest, the benchmark leaf SPAD value was 25 ± 1; at the third harvest, the benchmark leaf SPAD value was 24 ± 2; The SPAD value of the planned tobacco leaves to be harvested is: the average value of the SPAD values ​​of all the planned tobacco leaves to be harvested at each harvest.

2. The three-time harvesting method of flue-cured tobacco after rice stubble according to claim 1, characterized in that: When determining the SPAD value of a reference leaf, ≥ 10 tobacco leaves were measured, and each tobacco leaf was divided into three sections, namely the leaf base, the middle of the leaf, and the leaf tip. One point was selected symmetrically on both sides of the leaf blade 3 cm away from the main vein in the middle of each section for measurement. The average value of all the measured points was the SPAD value of the reference leaf.

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