Evaluation method and application of lodging-resistant capability of rice stalks

Abstract

The invention provides a method for evaluating lodging resistance of rice stalks and application. A method for evaluating lodging resistance of rice stalks comprises the following steps: firstly, establishing a mechanical model of stalk lodging, and calculating the critical wind speed of rice stalk lodging by measuring the breaking resistance, plant height, stem leaf weight, panicle weight, a wind attack angle in a lodging critical state and a plant windward area of the stalks; then, a rainfall action factor is introduced into calculation of the critical wind speed, and a critical wind speed model for evaluating the lodging-resistant capability of the stalks of the rice is established. The rice stem lodging critical wind speed model comprehensively considers plant crop traits, external wind and rain and other meteorological factors, highlights the important effect of wind and rain on rice stem lodging, and compared with an evaluation method singly using rice stem traits, the result better conforms to the actual situation, and is scientific and effective.

Description

Technical Field

[0001] The present invention relates to the technical field of rice cultivation, and in particular to a method for evaluating the lodging resistance of rice culms and its application. Background Art

[0002] Rice is the most important food crop in China. Greatly increasing the yield per unit area of rice is an important measure to ensure food security in China. During the heading to maturity stage of rice, due to the influence of climatic factors such as strong winds and rainfall, it is generally prone to lodging, which has become an important limiting factor for further improving the yield and quality. First of all, rice lodging reduces the light interception of the canopy, resulting in a significant decrease in yield. Secondly, the lodged panicles touch the ground, leading to pre-harvest sprouting, seriously affecting the rice quality. In addition, lodging also causes difficulties in large-scale mechanical harvesting and increases the harvesting cost, which seriously affects the improvement of rice production capacity and planting benefits.

[0003] Generally speaking, the higher the rice yield, the more prone it is to lodging. However, in actual production, under normal windless and rainless conditions, high-yield rice populations do not lodge either. Lodging often occurs along with winds and rains. Therefore, when evaluating the lodging resistance of rice, meteorological factors such as winds and rains must be considered. At present, some researchers have proposed some methods for evaluating the lodging resistance of rice. Commonly used methods such as direct field observation method classify the lodging resistance of different varieties according to the actual lodging situation in the field. This method is intuitive, simple and efficient. However, since lodging is the result of the interaction between the environment and the crop, in years with normal little wind and rain, almost all rice does not lodge, resulting in the inability to judge the difference in the culm lodging resistance of different varieties. The artificial induction lodging test method can make up for the above deficiencies, but it requires specific devices and is not suitable for popularization. The lodging index method calculates the lodging index by measuring the breaking resistance, fresh weight and plant height of the culm to characterize the lodging resistance of rice culms. This is based on its own agronomic and mechanical characteristics and does not consider climatic factors such as winds and rains, and cannot ensure the accuracy and applicability of the evaluation. The publicly disclosed "Method for Measuring and Calculating the Critical Wind Speed for Wheat Population Lodging Resistance" (Application No. 201710114171.0) proposed a method for calculating the critical wind speed for wheat population lodging resistance, but the formula is too cumbersome and does not consider the influence of rainfall. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a scientific method for evaluating the lodging resistance of rice culms and its application, providing necessary technical support for coordinating the contradiction between high yield and lodging and further improving the rice yield per unit area.

[0005] The present invention provides a method for evaluating the lodging resistance of rice stems. First, a mechanical model of stem lodging is established. By measuring the breaking resistance of the stem, plant height, fresh weight of stems and leaves, fresh weight of panicles, wind attack angle at the critical state of lodging, and the windward area of the plant, the critical wind speed of rice stem lodging is calculated. Then, a factor of rainfall effect is introduced in the calculation of the critical wind speed, and a critical wind speed model for evaluating the lodging resistance of rice stems is established.

[0006] In the above evaluation method, the formula for calculating the critical wind speed of the rice stem lodging is as follows:

[0007]

[0008] Wherein, V is the critical wind speed of the stem lodging, F is the breaking resistance of the stem at the internode where lodging occurs, L is the distance between the two fulcrums when measuring the breaking resistance, M is the fresh weight of the stems and leaves, m is the fresh weight of the panicles, H is the plant height, θ is the wind attack angle, ρ is the air density, S is the windward area of the plant, and C is the drag coefficient.

[0009] In the above evaluation method, the fresh weight of the stems and leaves is the fresh weight of the stems and leaves, and the fresh weight of the panicles is the fresh weight of the panicles.

[0010] In the above evaluation method, the plant height is the length from the base of the stem above the ground to half of the length of the panicle.

[0011] In the above evaluation method, to measure the breaking resistance of the base stem: use a stem strength tester to measure the breaking resistance F of the basal internode of the stem, and set the distance L between the two fulcrums to 5 cm;

[0012] To measure the plant height, the fresh weight of the stems and leaves, and the fresh weight of the panicles: measure the length H from the base to half of the length of the panicle, then cut it off flush with the mud at the base, divide it into two parts: the panicle and the stems and leaves, and measure the fresh weight M of the stems and leaves and the fresh weight m of the panicles respectively;

[0013] To measure the windward area of the plant: take a photo to obtain the projected area of the plant, and use software to calculate the projected area of the stem, which is the windward area S of the plant;

[0014] To measure the drag coefficient: measure the wind speeds on the windward and leeward sides of the stem, and the drag coefficient C = the wind speed on the leeward side / the wind speed on the windward side;

[0015] To measure the wind attack angle: push the stem until it breaks, and measure the angle θ between the stem and the ground at this time.

[0016] In the above evaluation method, the formula for establishing the critical wind speed model for evaluating the lodging resistance of the rice stems by introducing the rainfall effect factor is as follows:

[0017]

[0018] Among them, Vr is the critical wind speed of the stem lodging considering the factor of rainfall, a is the weight gain coefficient of the stem and leaves after rain, then aM is the weight of the stem and leaves after rain, b is the weight gain coefficient of the ear after rain, and bm is the weight of the ear after rain.

[0019] In the above evaluation method, after rainfall, the values of a and b are both greater than 1, and when there is no rainfall, the values of a and b are both 1.

[0020] Application of any of the above evaluation methods for the lodging resistance of rice stems in the early prediction and screening of the lodging resistance of rice varieties, or in the scientific cultivation of rice.

[0021] 1) The critical wind speed model of rice stem lodging provided by the present invention comprehensively considers the crop traits of the plant itself and meteorological factors such as wind and rain in the outside world, highlighting the important role of wind and rain on the lodging of rice stems. Compared with the evaluation method that only uses the traits of rice stems, the result is more in line with the actual situation and is scientific and effective.

[0022] 2) According to the method of the present invention, for a certain rice variety, the critical wind speed of its stem lodging can be calculated based on its stem traits, and then by comparing the meteorological data of previous years in different regions, the safe planting area and promotion area of the rice variety can be scientifically guided.

[0023] 3) According to the method of the present invention, by using the meteorological data of previous years in each region and combining with the target yield of rice, the required breaking force for the lodging resistance of rice stems can be calculated, so as to selectively screen suitable cultivated varieties, and at the same time provide reference for breeders to purposefully breed lodging-resistant varieties and improve the breeding efficiency. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 It is a schematic diagram of the mechanical model parameters in the critical state of rice stem lodging. Detailed Embodiments

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0027] A method for evaluating the lodging resistance of rice stems. First, a mechanical model of stem lodging is established. By measuring the breaking resistance of the stem, plant height, weight of stems and leaves, weight of panicles, wind attack angle at the critical state of lodging, and the windward area of the plant, the critical wind speed of rice stem lodging is calculated. Then, a factor of rainfall effect is introduced into the calculation of the critical wind speed, and a critical wind speed model for evaluating the lodging resistance of rice stems is established. The formula is as follows:

[0028]

[0029] Where, Vr is the critical wind speed of stem lodging considering the rainfall effect, F is the breaking resistance of the stem at the internode where lodging occurs, L is the distance between the two support points when measuring the breaking resistance, a is the coefficient of weight increase of stems and leaves after rain, then aM is the weight of stems and leaves after rain, b is the coefficient of weight increase of panicles after rain, then bm is the weight of panicles after rain, H is the plant height, θ is the wind attack angle, ρ is the air density, S is the windward area of the plant, and C is the drag coefficient.

[0030] Establish a mechanical model of the rice stem at the critical state of lodging. Assume that the gravity of the stems, leaves and panicles is G, the wind force acting on the rice plant is Fw, the direction of the wind force is parallel to the ground, the wind attack angle is θ (the angle between the wind force acting on the stem and the stem), the length from the base of the stem above the ground to half of the panicle is H, the weight of the stem (including leaves) is M, the weight of the panicle is m, one-fourth of the weight of the stems and leaves is converted to the center of gravity of the panicle, and the rice stem is simplified to a weightless equal-section rod, as Figure 1 shown.

[0031] Measure the breaking resistance of the basal stem: Use the YYD-1 stem strength tester (Zhejiang Top Instrument Co., Ltd., China) to measure the breaking resistance F of the basal internode of the stem, and set the distance L between the two support points to 5 cm.

[0032] Measure the plant height, weight of stems, leaves and panicles: Measure the length (H) from the base to half of the panicle, then cut it off at the base level with the mud, divide it into two parts: panicle and stems and leaves, and measure the fresh weight of the stems and leaves (M) and the fresh weight of the panicle (m) respectively;

[0033] Measure the windward area of the plant: Use a camera to take a picture to obtain the projected area of the plant, and use software to calculate the projected area of the stem, which is the windward area S of the plant;

[0034] Measure the drag coefficient: Use an anemometer to measure the wind speed on the windward and leeward sides of the stem, and the drag coefficient C = wind speed on the leeward side / wind speed on the windward side;

[0035] Measure the wind attack angle: The wind attack angle is the angle between the stem and the ground at the critical state of lodging. Manually push the stem until it breaks, and measure the angle θ between the stem and the ground at this time.

[0036] Calculate the wind force:

[0037] Fw = 0.5ρSCV 2 ①;

[0038] Among them, ρ is the air density (1.29 kg / m 3 ), S is the windward area of the rice plant, C is the drag coefficient, and V is the wind speed.

[0039] Calculate the gravity:

[0040] G = (1 / 4×M + m)g ②;

[0041] Calculate the component force of the wind force in the direction perpendicular to the stem:

[0042] Fw’ = Fwsinθ ③;

[0043] Calculate the component force of the gravity of the stem, leaves and panicle in the direction perpendicular to the stem as:

[0044] G’ = Gcosθ ④;

[0045] Calculate the lodging moment:

[0046] M = (Fw’ + G’)×H ⑤;

[0047] Calculate the lodging resistance moment of the basal stem of the rice:

[0048] B = 1 / 4×F×L ⑥;

[0049] Among them, F is the flexural resistance of the internode where lodging occurs, and L is the distance between the two fulcrums when measuring the flexural resistance.

[0050] Calculate the critical wind speed for stem lodging of the rice:

[0051] In the critical state of lodging, M = B. Substituting equations ① - ⑥, we get:

[0052] (0.5ρSCV 2 sinθ + Gcosθ)×H = 1 / 4×F×L ⑦;

[0053] From equation ⑦, we can get:

[0054]

[0055] Equation ⑧ is the critical wind speed model for evaluating the lodging resistance ability of the rice. From equation ⑧, it can be seen that the larger the flexural resistance F at the base of the stem, the larger V, indicating that the lodging resistance ability of the rice is stronger; while the larger the weight of the stem, leaves and panicle M and the weight of the panicle m, the higher the plant height H, and the larger the windward area S, the smaller V, indicating that the lodging resistance ability of the rice is weaker, which is in line with the actual production situation.

[0056] Determine the influence of rainfall on the critical wind speed for stem lodging of the rice:

[0057] Rainwater adheres to the rice ears, stems and leaves, resulting in an increase in the weight of the stems, leaves and ears. After the rain, the weight of the stems and leaves is aM, where a is the weight gain coefficient of the stems and leaves after the rain; the weight of the ears after the rain is bm, where b is the weight gain coefficient of the ears after the rain. Take several plants with consistent growth. Divide some of the plants into two parts: the stem and the ear, and weigh them separately, denoted as M and m; fix the other part to keep the plants in their natural state, artificially simulate rainfall, record the rainfall amount and rainfall duration, record the weight of the plants after the rain until the weight no longer increases, stop the rainfall, divide the plants into two parts: the stems and leaves and the ears, and measure their weights M' and m' respectively. Then the weight gain coefficient of the stems and leaves after the rain a = M' / M, b = m' / m, and both a and b are coefficients greater than 1. Substitute the weights of the stems, leaves and ears after the rain into Equation ⑧ to obtain the critical wind speed for lodging after rainfall:

[0058]

[0059] It can be seen from Equation ⑨ that after rainfall, the weight of the stems and leaves aM and the weight of the ears bm increase, and the critical wind speed for lodging Vr decreases, indicating that the lodging resistance ability of rice decreases, which is consistent with the actual situation. When there is no wind and rain, the values of a and b are 1, and Equation ⑨ is the same as Equation ⑧.

[0060] Example 1

[0061] The determination and calculation of the critical wind speed for lodging resistance of paddy rice stems in the field include the following steps: (1) Rice is prone to lodging in the middle and late stages of filling. Therefore, measure each parameter 30 days after the rice has headed; (2) Use a plant stem strength tester (YYD-1 type) to measure the breaking resistance of the basal internodes of the rice, and the distance between the two fulcrums is 5 cm; (3) Cut the rice plants at ground level, measure the length from the base to half of the ear, and then divide the plants into two parts: the stem and the ear, and weigh them separately with an electronic balance; (4) Measure the wind attack angle in the critical state of stem lodging. Slowly push the stem until the basal internode breaks, and measure the angle between the basal stem and the ground at this time as the wind attack angle; (5) Measure the windward area of the plant. Place the rice plant flat and take a vertical photo with a camera. Use software analysis to obtain the projected area of the plant as the windward area; (6) Measure the drag coefficient of the plant. Measure the wind speeds on the windward and leeward sides of the ear at a certain wind speed respectively. The drag coefficient is the ratio of the leeward wind speed to the windward wind speed; (7) Calculate the critical wind speed for lodging resistance of the rice stem through Equation ⑧, with the unit of m / s; (8) Measure the critical wind speed for lodging resistance of the rice stem after rain. Measure the weights of the stem and the ear before and after the rain respectively, calculate the weight gain coefficients a and b of the stem and the ear after the rain, and calculate the critical wind speed for lodging resistance of the rice stem after rain according to Equation ⑨.

[0062] The test results show that under non-rainfall conditions (as shown in Table 1), the critical wind speed for lodging of the rice variety Huanghuazhan is 12.6 m / s (wind speed of grade 6), and the measured wind speed at which lodging occurs is 11.9 m / s; while under rainfall conditions (as shown in Table 2), the critical wind speed for lodging decreases to 10.7 m / s (wind speed of grade 5), and the measured wind speed at which lodging occurs is 10.2 m / s.

[0063] Table 1 Test results under non-rainfall conditions

[0064]

[0065] Table 2 Test results under rainfall conditions

[0066]

[0067] As can be seen from Table 1 and Table 2, under non-rainfall and rainfall conditions, it is only necessary to measure morphological traits such as flexural strength, plant height, stem weight, panicle weight, and windward area, and the wind attack angle, and then calculate the critical wind speed in the two cases using Equation ⑧ and Equation ⑨ respectively. The measurement and calculation operations are simple; comparing the measured wind speed at the time of lodging, the difference is 5.9% under non-rainfall conditions and 4.9% under rainfall conditions, both within the error range; the evaluation method of the present invention takes into account both crop traits and meteorological factors such as wind and rain, and has strong comprehensive evaluation ability and operability. The above test results show that the results obtained by using the evaluation method of the present invention are consistent with the actual results of field tests, and the evaluation method of the present invention has high accuracy. Therefore, the evaluation method of the present invention can reflect the actual situation of lodging and be used to evaluate the lodging resistance of rice.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An evaluation method for the lodging resistance of rice stems, characterized in that, First, establish a mechanical model of stem lodging. By measuring the breaking resistance of the stem, plant height, fresh weight of the stem and leaves, fresh weight of the ear, wind attack angle at the critical state of lodging, and the windward area of the plant, calculate the critical wind speed of rice stem lodging; then introduce the factor of rainfall in the calculation of the critical wind speed, and establish a critical wind speed model for evaluating the lodging resistance ability of rice stems.

2. The evaluation method for the lodging resistance of rice culms according to claim 1, characterized in that, The formula for calculating the critical wind speed of the rice stem lodging is as follows: Among them, V is the critical wind speed of the stem lodging, F is the breaking resistance of the stem at the internode where lodging occurs, L is the distance between the two fulcrums when measuring the breaking resistance, M is the fresh weight of the stem and leaves, m is the fresh weight of the ear, H is the plant height, θ is the wind attack angle, ρ is the air density, S is the windward area of the plant, and C is the drag coefficient.

3. The evaluation method for the lodging resistance of rice culms according to claim 1 or 2, characterized in that The fresh weight of the stem and leaves is the fresh weight of the stem and leaves, and the fresh weight of the ear is the fresh weight of the ear.

4. The evaluation method for the lodging resistance of rice stems according to claim 1 or 2, characterized in that, The plant height is the length from the base of the stem above the ground to half of the ear.

5. The evaluation method for the lodging resistance of rice culms according to claim 2, wherein Measure the breaking resistance of the base stem: Use a stem strength tester to measure the breaking resistance F of the basal internode of the stem, and set the distance L between the two fulcrums to 5 cm; Measure the plant height, the fresh weight of the stem and leaves, and the fresh weight of the ear: Measure the length H from the base to half of the ear, then cut it off at the base level with the mud, divide it into two parts: the ear and the stem and leaves, and measure the fresh weight M of the stem and leaves and the fresh weight m of the ear respectively; Measure the windward area of the plant: Take a photo to obtain the projected area of the plant, and use software to calculate the projected area of the stem, which is the windward area S of the plant; Measure the drag coefficient: Measure the wind speeds on the windward and leeward sides of the stem, and the drag coefficient C = the wind speed on the leeward side / the wind speed on the windward side; Measure the wind attack angle: Push the stem until it breaks, and measure the angle θ between the stem and the ground at this time.

6. The evaluation method for the lodging resistance of rice culms according to claim 1, wherein The formula for establishing a critical wind speed model for evaluating the lodging resistance ability of the rice stem by introducing the factor of rainfall is as follows: Among them, Vr is the critical wind speed of the stem lodging after introducing the factor of rainfall, a is the coefficient of increase in the fresh weight of the stem and leaves after rain, then aM is the fresh weight of the stem and leaves after rain, b is the coefficient of increase in the fresh weight of the ear after rain, then bm is the fresh weight of the ear after rain.

7. The evaluation method for the lodging resistance of rice culms according to claim 6, characterized in that After rainfall, the values of a and b are both greater than 1. When there is no rainfall, the values of a and b are both 1.

8. Application of the method for evaluating the lodging resistance ability of the rice stem according to any one of claims 1 to 7 in the early prediction and screening of the lodging resistance ability of rice varieties, or in the scientific planting of rice.

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