Herbicidal composition for controlling weeds in dryland rice paddies in mountainous areas, its preparation method and uses

Abstract

This application provides a herbicidal composition for controlling weeds in dryland rice fields in mountainous areas, its preparation method, and its uses. The herbicidal composition consists of pendimethalin suspension concentrate, pyrimisulfuron-methyl oil dispersible suspension concentrate, and a special agricultural synergist, with a volume ratio of (30-70):(5-10):(20-55). The herbicidal composition of this application achieves a comprehensive control efficacy of over 97% against grasses and broadleaf weeds in direct-seeded rice fields in dryland areas, and is particularly suitable for soil treatment in direct-seeded rice fields in mountainous areas, exhibiting excellent comprehensive control efficacy. It maintains excellent control efficacy even with a 29% reduction in herbicide dosage. Furthermore, this composition is suitable for aerial spraying, helping to reduce pesticide costs and environmental pollution.

Description

Technical Field

[0001] This application belongs to the field of pesticide technology. Specifically, this application provides a herbicidal composition for controlling weeds in dryland rice paddies in mountainous areas, its preparation method, and its uses. Background Technology

[0002] Pendimethalin (also known as Pendimethalin, Pendimethalin, Pendimethalin, Pendimethalin, Pendimethalin, Pendimethalin) is a herbicide belonging to the dinitroaniline class. It does not inhibit the germination of weed seeds; instead, it effectively controls weeds by blocking cell division in the meristematic tissues during germination, thereby hindering the normal development of young shoots and secondary roots. Pendimethalin has a wide range of applications, controlling annual grasses and broadleaf weeds in crops such as corn, soybeans, cotton, vegetables, and orchards, including many common weeds such as crabgrass, foxtail, Kentucky bluegrass, Alopecurus aequalis, goosegrass, sedge, sedge, black nightshade, and amaranth.

[0003] Pyrimisulfuron, also known as weed killer, is a sulfonylurea herbicide and an acetolactate synthase inhibitor. It is primarily absorbed through the roots of weeds, inhibiting their growth and causing them to gradually die. It effectively controls annual broadleaf weeds and sedges such as Cyperus difformis, Cyperus rotundus, Cyperus rotundus, Cyperus alternifolius, water celery, water spinach, arrowhead, pondweed, duckweed, and eclipta prostrata, with minimal impact on rice. It also exhibits stable efficacy and a long-lasting effect.

[0004] Crabgrass (Digitaria sanguinalis (L.) Scop.) is an annual herbaceous plant belonging to the genus Digitaria in the family Poaceae. It has a rapid seed dispersal rate, strong reproductive capacity, fast plant growth rate, and many branches. It is widely distributed in many provinces of my country and is one of the major noxious weeds in mountainous dryland farmland. It has invaded dryland direct-seeded rice fields or dryland rice fields in large numbers, especially forming dominant communities in fields with uneven surfaces or poor water retention. The damage is getting worse year by year, making it a difficult point for chemical control of weeds.

[0005] Bidens pilosa L., belonging to the Asteraceae family and the Bidens genus, is an annual herbaceous plant widely distributed in field ridges and wastelands in South, Central, and Southwest my country. It is characterized by high germination and seed setting rates, and is considered one of the more harmful invasive alien weeds. With the continuous expansion of land reclamation for grain cultivation, it has gradually become a common weed in crop fields. Due to its extensive root system and strong water and fertilizer absorption capacity, it severely restricts crop growth and affects crop yield.

[0006] Agricultural synergists themselves have no biological activity, but when mixed with herbicides, they can significantly reduce the surface tension of the solution, decrease the contact angle between droplets and plant leaves, and enhance the wetting, adhesion, spreading, and penetration capabilities of the herbicide on plant leaves, thereby greatly improving efficacy. The rational use of agricultural synergists can reduce the amount of herbicide used while ensuring protective effects, achieving the goals of cost reduction and environmental protection.

[0007] In recent years, Yunnan Province has focused on stabilizing rice planting areas in mountainous areas to solidify its strategic bottom line of "ensuring basic self-sufficiency in grains and absolute security in staple food." This has led to the development of a new "dryland rice" production method, which was promoted on 500,000 mu (approximately 33,333 hectares) of land in Yunnan Province in 2022. However, weed problems in dryland areas constantly affect rice yields. For example, weeds such as crabgrass, goosegrass, beggar-ticks, and ageratum, which should be found in wasteland, are appearing in the fields. Food security faces challenges from various types of weeds, and there are no clearly defined pesticides or solutions available on the market. Therefore, there is an urgent need to explore an efficient and safe weeding technology.

[0008] Chinese patent application CN 105409997 A discloses a wettable powder formulation of pyrimisulfuron and pendimethalin and its preparation method, relating to the field of weed control in transplanted rice paddies. However, several compositions in this patent were found to be less effective against Bidens pilosa, Ageratum conyzoides, and Gnaphalium affine in experiments, and due to the formulation, it is not suitable for direct-seeded rice fields in dryland areas.

[0009] Chinese invention patent CN 107372562 A discloses a herbicide composition of pendimethalin, isoxaflutole, and pyrimisulfuron, relating to a herbicide for controlling annual weeds and barnyardgrass in direct-seeded rice fields. By rationally proportioning the components of pendimethalin, isoxaflutole, and pyrimisulfuron in the herbicide composition, the herbicide's efficacy is enhanced, resulting in better control of weeds in direct-seeded rice fields. However, the isoxaflutole contained in this patent poses a significant risk of phytotoxicity to vegetables and potatoes planted after rice in mountainous dryland areas, and the ternary compound is prone to the emergence of multi-resistant weed varieties, increasing the difficulty of later control.

[0010] This weed control composition not only solves the above-mentioned problems, but is also suitable for drone-based aerial spraying. Summary of the Invention

[0011] This application provides a herbicidal composition for controlling weeds in dryland rice paddies in mountainous areas. The herbicidal composition consists of pendimethalin suspension concentrate, pyrimisulfuron-methyl oil dispersible suspension concentrate, and a special agricultural synergist. The special agricultural synergist consists of a solvent, organosilicon, methyl oleate, and a safener. The solvent is selected from one or more of methanol, isopropanol, acetone, xylene, and dichloromethane. The organosilicon is a mixture of IOTA-2000 and IOTA-331. The safener is selected from one or more of glyphosate, quinalazine, pyrazolium bromide, and oxime ether.

[0012] In addition, the herbicidal composition is composed of diluted pendimethalin suspension, diluted pyrimisulfuron dispersible oil suspension and special agricultural synergist, with a volume ratio of (30-70):(5-10):(20-55).

[0013] The dimethomorph suspension is prepared by diluting a 450 g / L dimethomorph suspension stock solution with water by 10-30 times.

[0014] The pyrimisulfuron dispersible oil suspension is prepared by diluting a 15% pyrimisulfuron dispersible oil suspension stock solution with water by 10-30 times.

[0015] Furthermore, in the special agricultural synergist, the mass-to-volume ratio of organosilicon surfactant, methyl oleate and safener in the solvent is (0.2–1.0) (g / L): (0.3–1.5) (g / L): (5.0–12) (g / L), and the solvent is made up to 1 L.

[0016] In particular, the organosilicon surfactant is composed of IOTA-2000 and IOTA-331 in a mass ratio of (0.5–1.0):(1.0–1.5).

[0017] In addition, this application provides a method for preparing the above-mentioned herbicidal composition, the method comprising the following steps:

[0018] ① Mix 450 g / L pendimethalin suspension stock solution with distilled water at a volume ratio of 1:(10-30), and treat with 30 kHz low-frequency ultrasound for 15-150 seconds under stirring conditions at 25℃ and 200 r / min; after treatment, let stand to obtain translucent pendimethalin suspension S1.

[0019] ② Mix 15% pyrimisulfuron dispersible oil suspension mother liquor with distilled water at a volume ratio of 1:(10-30) (g / L), and treat with 30 kHz low-frequency ultrasound for 15-150 seconds under stirring conditions at 25℃ and 200 r / min; after treatment, let stand to obtain translucent pyrimisulfuron dispersible oil suspension N1;

[0020] ③ Add the organosilicon surfactant, methyl oleate, and safener to the solvent in the following mass-volume ratio: organosilicon surfactant (0.2–1.0) g / L, methyl oleate (0.3–1.5) g / L, and safener (5.0–12) g / L; then stir at 25℃ and 300 r / min for 5–10 minutes to fully disperse the components. After standing, a transparent special agricultural synergist solution M1 is obtained.

[0021] ④ Mix S1 obtained in step ①, N1 obtained in step ② and M1 obtained in step ③ at a volume ratio of (30-70):(5-10):(20-55), stir thoroughly, and then perform ultrasonic treatment to obtain the mother liquor SMN of the herbicidal composition.

[0022] The method further includes the following steps:

[0023] ⑤ Preparation of application solution: Dilute the stock solution of the herbicidal composition obtained in step ④ with water by 30-450 times, mix well and obtain the ready-to-use application solution (MSN-solution).

[0024] Finally, this application provides the application of the above-mentioned herbicidal composition in the control of weeds in direct-seeded rice fields in mountainous drylands. The weeds are crabgrass and beggar-ticks; the herbicidal composition is applied as a soil spray after sowing but before emergence; preferably, the working concentration application rate is 30 L / mu.

[0025] Beneficial effects:

[0026] Under the aforementioned control steps, the present invention can achieve a comprehensive control efficacy of over 97% against grasses and broadleaf weeds in direct-seeded rice fields in dryland areas.

[0027] Compared with existing technologies, this invention is applicable to soil treatment in direct-seeded rice fields in dryland areas of Yunnan, with excellent comprehensive control efficacy. Even with a 29% reduction in herbicide dosage, it still maintains excellent control efficacy.

[0028] Furthermore, this invention can also be applied to aerial spraying operations, reducing pesticide costs and environmental pollution. Attached Figure Description

[0029] Figure 1 Flowchart for the formulation of herbicide compositions.

[0030] Figure 2 This is a photograph of the actual process of preparing a herbicide composition.

[0031] Figure 3 A comparison chart showing the weed control efficacy of reduced-dosage herbicides and conventional herbicides.

[0032] The herbicidal composition stock solution MSN is prepared by combining pendimethalin suspension S1, pyrimisulfuron dispersible oil suspension N1, and special agricultural synergist M1. After dilution, it becomes the application solution of the herbicidal composition (MSN-solution). Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] This invention proposes a weed control composition for controlling weeds in dryland rice paddies in mountainous areas, its preparation method, and its uses. Specifically, it is a weed control composition comprising pendimethalin suspension concentrate, pyrimisulfuron oil suspension concentrate, and a special agricultural synergist. The invention is further illustrated below using common grasses such as crabgrass (Digitaria sanguinalis) and broadleaf grass (Bidens pilosa) as examples. This invention targets grasses including, but not limited to, crabgrass and Bidens pilosa.

[0035] Example 1: Formulation of herbicide composition

[0036] The herbicide composition preparation process is as follows: Figure 1 and Figure 2 .

[0037] (1) Preparation of special agricultural synergist M1

[0038] Formula 1: (1-1) Add organosilicon (IOTA-2000+IOTA-331), methyl oleate and pyrazinyl oleate to methanol at a mass-volume ratio of 0.3 g / L, 0.5 g / L and 7.7 g / L, respectively. The mass ratio of IOTA-2000 to IOTA-331 is 1.0:1.5. Stir at 300 r / min for 5-10 min at room temperature to fully disperse the components. Let stand for 5 min to form a transparent solution M1-1.

[0039] Formula 2: (1-2) Add organosilicon (IOTA-2000+IOTA-331), methyl oleate and pyrazinyl oleate to isopropanol at a mass-volume ratio of 0.3 g / L, 0.5 g / L and 7.7 g / L, respectively, wherein the mass ratio of IOTA-2000 to IOTA-331 is 1.0:1.5. Stir at 300 r / min for 5-10 min at room temperature to fully disperse the composition, and let stand for 5 min to form a transparent solution M1-2.

[0040] Formula 3: Add organosilicon (IOTA-2000+IOTA-331), methyl oleate and pyrazinyl oleate to xylene at a mass-volume ratio of 0.3 g / L, 0.5 g / L and 7.7 g / L, respectively, wherein the mass ratio of IOTA-2000 to IOTA-331 is 1.0:1.5. Stir at 300 r / min for 5-10 min at room temperature to fully disperse the composition, and let stand for 5 min to form a transparent solution M1-3.

[0041] Formula 4: (1-4) Add organosilicon (IOTA-2000+IOTA-331), methyl oleate and pyrazinyl oleate to isopropanol at a mass-volume ratio of 0.3 g / L, 0.5 g / L and 7.7 g / L, respectively. The mass ratio of IOTA-2000 to IOTA-331 is 1.5:1.0. Stir at 300 r / min for 5-10 min at room temperature to fully disperse the components. Let stand for 5 min to form a semi-transparent solution M1-4.

[0042] Formula 5: (1-5) Add organosilicon (IOTA-2000+IOTA-331), methyl oleate and detoxifying quinolone to isopropanol at a mass-volume ratio of 0.3 g / L, 0.5 g / L and 7.7 g / L, respectively. The mass ratio of IOTA-2000 to IOTA-331 is 1.0:1.5. Stir at 300 r / min for 5-10 min at room temperature to fully disperse the components. Let stand for 5 min to form a semi-transparent solution M1-5.

[0043] Formula 6: (1-6) Add organosilicon (IOTA-2000+IOTA-331), methyl oleate and pyrazosulfuron-methyl to isopropanol at a mass-volume ratio of 0.3 g / L, 0.5 g / L and 7.7 g / L, respectively. The mass ratio of IOTA-2000 to IOTA-331 is 1.0:1.5. Stir at 300 r / min for 5-10 min at room temperature to fully disperse the components. Let stand for 5 min to form a semi-transparent solution M1-6.

[0044] (2) Preparation of suspension diluents S1 and N1

[0045] The mother liquor of pendimethalin suspension was mixed with distilled water at a mass-to-volume ratio of 1:10. The mixture was then subjected to low-frequency ultrasonic treatment at 30 kHz for 2 minutes under stirring conditions at 25℃ and 200 r / min. After dilution and standing, a semi-transparent pendimethalin suspension S1 was obtained.

[0046] The mother liquor of pyrimisulfuron dispersible oil suspension was mixed with distilled water at a mass-to-volume ratio of 1:10. The mixture was then subjected to low-frequency ultrasonic treatment at 30 kHz for 2 minutes under stirring conditions at 25℃ and 200 r / min. After dilution and standing, a semi-transparent pyrimisulfuron dispersible oil suspension N1 was obtained.

[0047] (3) Preparation of herbicide composition stock solution MSN

[0048] The mother liquors S1 and N1 prepared in the above steps are mixed with solution M1 at a volume ratio of 70:7.5:22.5, stirred thoroughly, and then subjected to ultrasonic treatment to obtain the herbicidal composition mother liquor MSN.

[0049] (4) Preparation of MSN-solution, the herbicidal composition application solution

[0050] Before field application, dilute the obtained herbicidal composition stock solution with water, stir well, and finally form an application solution containing herbicidal active ingredients, MSN-solution.

[0051] Test location: Plant Protection Station of Yuanjiang Hani, Yi and Dai Autonomous County, Yuxi City, Yunnan Province.

[0052] Test materials: Rice (Dianheyou '615', Yunnan Jinding Hepu Agricultural Technology Co., Ltd.), and crabgrass and beggar-ticks were locally collected seeds.

[0053] Planting method: potted plants, each pot requires 7-8 kg of soil, using field topsoil, repeated 3 times.

[0054] Rice and Bidens pilosa were planted by artificial sowing (5-6 seeds per hole). Crataegus pinnatifida was planted by broadcasting after mixing with sand (12 g of seeds mixed with 10 kg of sand, 3 g broadcast per pot).

[0055] Application method: Apply the above-mentioned herbicide combinations to the soil after rice sowing (dosage: 30 L / mu).

[0056] Calculate its fresh weight efficacy and total efficacy.

[0057] Fresh weight efficacy (%) = [(fresh weight of control group - fresh weight of treatment group) / fresh weight of control group] * 100.

[0058] Total control efficacy (%) = [(total fresh weight of control group - total fresh weight of treatment group) / total fresh weight of control group] * 100.

[0059] CK: A water control treatment (CK) was set up, in which 30 L of water was sprayed onto the soil per acre after rice sowing.

[0060] Table 1: Safety, weed control efficacy and surface tension of rice under different formulation conditions

[0061]

[0062] As shown in Table 1, the total weed control efficacy of the mixture of pendimethalin suspension concentrate, pyrimisulfuron dispersible oil suspension concentrate, and special agricultural synergist of this invention all reached over 90%. Among them, formulations 3, 5, and 6 showed excellent control efficacy against crabgrass and beggar-ticks, exceeding 95%, and exhibited a higher droplet diameter, indicating that formulation 3 has better anti-drift ability during aerial spraying. The isobutanol solvent in the agricultural synergist provides better dissolution, facilitating stable drug presence in solution, and is inexpensive with minimal harm to humans.

[0063] Example 2: This example demonstrates the application of a reduction test and herbicidal composition.

[0064] Test location: Plant Protection Station of Yuanjiang Hani, Yi and Dai Autonomous County, Yuxi City, Yunnan Province.

[0065] Test materials: Rice (Dianheyou '615', Yunnan Jinding Hepu Agricultural Technology Co., Ltd.), and crabgrass and beggar-ticks were locally collected seeds.

[0066] Planting method: potted plants, each pot requires 7-8 kg of soil, using field topsoil, repeated 3 times.

[0067] Rice and Bidens pilosa were planted by artificial sowing (5-6 seeds per hole). Crataegus pinnatifida was planted by broadcasting after mixing with sand (12 g of seeds mixed with 10 kg of sand, 3 g broadcast per pot).

[0068] Test reagents: 450 g / L pendimethalin suspension was purchased from BASF AG, 15% pyrimisulfuron oil suspension was purchased from Hefei Xingyu Chemical Co., Ltd., and the components of the special agricultural synergist (formula 3) were commercially available.

[0069] Application method: Soil spraying after rice sowing (application rate: 30 L / mu)

[0070] CK: A water control treatment (CK) was set up, in which 30 L of water was sprayed onto the soil per acre after rice sowing.

[0071] T1: Measure 140 mL of 450 g / L pendimethalin suspension stock solution, add water to make up to 1400 mL while stirring, and stir evenly to obtain diluted pendimethalin suspension S1. After rice sowing, add water to the diluted pendimethalin suspension to make up to 30 L of total volume, and use the above-mentioned twice-diluted application solution T1-solution for soil spraying to ensure uniform spraying.

[0072] T2: Measure 15 mL of 15% pyrimisulfuron dispersible oil suspension, add water to make up to 150 mL while stirring, stir evenly to obtain diluted pyrimisulfuron dispersible oil suspension N1, dilute the above pyrimisulfuron dispersible oil suspension with water to a total volume of 30 L, and use the above diluted application solution T2-solution for soil spraying to ensure uniform spraying.

[0073] T3: A commonly used herbicide composition in the local area, consisting of 140 ml of 450 g / L pendimethalin suspension concentrate and 15 ml of 15% pyrimisulfuron dispersible oil suspension concentrate (without adding special agricultural synergists). After mixing thoroughly with an appropriate amount of water, dilute to 30 L. After rice sowing, use the diluted T3-solution for soil spraying to ensure uniform spraying.

[0074] T4: Mix 100 mL of 450 g / L pendimethalin suspension concentrate and 10 mL of 15% pyrimisulfuron dispersible oil suspension concentrate (without adding special agricultural synergist, reducing the dosage of suspension concentrate), add an appropriate amount of water and mix thoroughly, then dilute with water to 30 L. After rice sowing, use the above diluted application solution T4-solution for soil spraying.

[0075] T5: Take 100 mL of diluted pendimethalin suspension S1 from T1 and 10 mL of diluted pyrimisulfuron dispersible oil suspension N1 from T2 and mix them. Then add the resulting mixed suspension to 45 mL of special pesticide synergist and stir ultrasonically. The resulting herbicide composition stock solution MSN is obtained. After rice sowing, dilute the above stock solution with water to 30 L. After rice sowing, use the above diluted application solution MSN-solution for soil spraying to ensure uniform spraying.

[0076] Example 2 Measurement Indicators: Rice plant height, number of crabgrass seedlings, and number of Bidens pilosa seedlings were measured 14 days after application. Rice fresh weight, rice plant height, number of crabgrass seedlings, fresh weight of crabgrass, number of Bidens pilosa seedlings, and fresh weight of Bidens pilosa were measured 28 days after application.

[0077] Calculate its control efficacy per plant, control efficacy per fresh weight, and total control efficacy.

[0078] Control efficacy (%) = [(Number of plants in control group - Number of plants in treatment group) / Number of plants in control group] * 100.

[0079] Fresh weight efficacy (%) = [(fresh weight of control group - fresh weight of treatment group) / fresh weight of control group] * 100.

[0080] Total control efficacy (%) = [(total fresh weight of control group - total fresh weight of treatment group) / total fresh weight of control group] * 100.

[0081] The specific statistical results are shown in Tables 2 and 3. The experimental results obtained are as follows: Figure 3 As shown.

[0082] Table 2: Differences in safety of different pesticide treatments on rice

[0083]

[0084] Note: Lowercase letters indicate a 5% significance level (P<0.05).

[0085] Table 2 shows that 14 days after application, except for treatment T3, there was no significant difference in the number of seedlings compared with the control in any of the herbicide treatments. 28 days after application, the plant height of rice in all treatments was not affected, but the fresh weight of rice in all treatments was significantly higher than that in the control. This indicates that commonly used herbicides in the area have a certain impact on rice emergence, while the reduced-dosage mixtures of pendimethalin suspension, 15% pyrimisulfuron-methyl oil dispersible suspension, and a special agricultural synergist were not affected.

[0086] Table 3: Differences in weed control efficacy of different herbicide treatments

[0087]

[0088] Note: Lowercase letters indicate a 5% significance level (P<0.05).

[0089] Table 3 shows that, compared with the commonly used local herbicidal composition (T3), the overall control efficacy of adding a special agricultural synergist after a 29% reduction in herbicide dosage still reached the T3 level; while compared with the treatment without the special agricultural synergist (T4), the overall control efficacy increased by 33.4% after adding the special agricultural synergist. This indicates that the mixture of pendimethalin suspension, 15% pyrimisulfuron oil suspension, and the special agricultural synergist still maintains excellent weed control effects while reducing pesticide usage.

[0090] Figure 3 A comparison chart showing the weed control efficacy of reduced-dosage herbicides versus conventional herbicides. Figure 3 As shown, the mixture of pendimethalin suspension, 15% pyrimisulfuron oil suspension, and a special agricultural synergist maintains excellent weed control while reducing pesticide usage. Furthermore, it is safe for rice.

[0091] Example 3: Unmanned Aerial Vehicle (UAV) Flight Test

[0092] Implementation location: Lancang Lahu Autonomous County, Pu'er City, Yunnan Province.

[0093] Application of the herbicides: Dilute 100 mL of the stock solution of the above-mentioned herbicides with water to 3 L, stir well, and add it to the spraying tank of the drone for soil spraying.

[0094] Application method: Soil spraying treatment using drones.

[0095] The relevant parameters for aerial spraying are shown in the table below.

[0096] Table 4: Relevant parameters for UAV soil spraying treatment

[0097]

[0098] Comparative Example 1: Water control treatment, i.e., water without any herbicide added, soil spraying was carried out by drone, with a liquid volume of 3 L / acre.

[0099] Comparative Example 2: Manual control. Weeds in the plots of this treatment were manually removed every 7 days after sowing.

[0100] Example 3 Measurement indicators: 28 days after application, a random sampling method was used, with 3 points as a group, repeated 3 times, and the survey covered 1 m. 2 Fresh weight of weeds. At harvest, the above sampling method was used to conduct actual yield measurement, and the actual yield was calculated based on 14.5% moisture content.

[0101] Table 5: Weed Control Efficacy and Yield Measurement of UAV Soil Spraying

[0102]

[0103] Based on comprehensive analysis, this herbicidal composition has a good control effect on weeds in dryland rice fields, is safe for rice, is suitable for drone spraying, and has important application value in dryland rice cultivation in mountainous areas.

[0104] It is used in direct-seeded rice fields in mountainous drylands to control grasses and broadleaf weeds.

[0105] The specific embodiments of the present invention have been described above, but the present invention is not limited thereto. Various changes can be made to the present invention as long as they do not depart from the spirit of the present invention.

Claims

1. A herbicidal composition for controlling weeds in dryland rice paddies in mountainous areas, characterized in that: The herbicidal composition comprises pendimethalin suspension, pyrimisulfuron-methyl oil dispersible suspension, and a special agricultural synergist. The pendimethalin suspension is prepared by diluting pendimethalin suspension stock solution with water. The pyrimisulfuron-methyl oil dispersible suspension is prepared by diluting pyrimisulfuron-methyl oil dispersible suspension stock solution with water. The special agricultural synergist comprises a solvent, an organosilicon surfactant, methyl oleate, and a safener. The solvent is selected from one or more of methanol, isopropanol, acetone, xylene, and dichloromethane. The organosilicon surfactant is a mixture of IOTA-2000 and IOTA-331. The safener is selected from one or more of glyphosate, quinalazine, pyrazolium bromide, and oxime ether compounds.

2. The herbicidal composition according to claim 1, characterized in that, The volume ratio of the dimethyl pendimethalin suspension, pyrimisulfuron dispersible oil suspension, and special agricultural synergist is (30-70):(5-10):(20-55).

3. The herbicidal composition according to claim 2, characterized in that: The dimethomorph suspension was prepared by diluting a commercially available 450 g / L dimethomorph suspension stock solution; The pyrimisulfuron dispersible oil suspension was prepared by diluting a commercially available 15% (approximately 150 g / L) pyrimisulfuron dispersible oil suspension stock solution. In the aforementioned special agricultural synergist, the mass concentration ratio of organosilicon surfactant, methyl oleate, and safener in the solvent is (0.2–1.0) (g / L): (0.3–1.5) (g / L): (5.0–12) (g / L), and the solvent is made up to 1 L. The organosilicon surfactant is a mixture of IOTA-2000 and IOTA-331, and the mass ratio of IOTA-2000 to IOTA-331 is (0.5–1.0):(1.0–1.5).

4. A method for preparing the herbicidal composition according to any one of claims 1-3, characterized in that, The specific steps include the following: (1) Preparation of pendimethalin suspension: Mix commercially available 450 g / L pendimethalin suspension stock solution with distilled water at a volume ratio of 1:(10-30), and under stirring conditions of 25℃ and 200 r / min, treat with 30 kHz low-frequency ultrasound 3-10 times, each treatment lasting 5-15 seconds, with an interval of 1-3 minutes between each ultrasound treatment; after treatment, let stand to obtain translucent pendimethalin suspension S1; (2) Preparation of pyrimisulfuron dispersible oil suspension: Mix 15% commercially available pyrimisulfuron dispersible oil mother liquor with distilled water at a volume ratio of 1:(10-30), and under stirring conditions of 25℃ and 200 r / min, treat with 30 kHz low-frequency ultrasound 3-10 times, each treatment lasting 5-15 seconds, with an interval of 1-3 minutes between each ultrasound treatment; after treatment, let stand to obtain translucent pyrimisulfuron dispersible oil suspension N1; (3) Preparation of special agricultural synergist: Add organosilicon surfactant, methyl oleate and safener to solvent in the following mass-volume ratio: organosilicon surfactant (0.2–1.0) g / L, methyl oleate (0.3–1.5) g / L, safener (5.0–12) g / L; then stir at 25℃ and 300 r / min for 5–10 minutes to fully disperse the components. After standing, a transparent special agricultural synergist solution M1 is obtained.

5. (4) Preparation of the herbicidal composition mother liquor: The S1 obtained in step ①, the N1 obtained in step ② and the M1 obtained in step ③ are mixed in a volume ratio of (30-70): (5-10): (20-55), stirred thoroughly, and then subjected to ultrasonic treatment to obtain the herbicidal composition mother liquor MSN.

6. The method according to claim 4, characterized in that, The herbicidal composition is diluted with water 30-450 times before field application to obtain the application solution SMN-solution.

7. The herbicidal composition according to claim 5 can be applied to control weeds in direct-seeded rice fields in mountainous drylands. This application relies on the composition's highly effective control of gramineous and broadleaf weeds, combined with the characteristics of the mountainous dryland operating environment, and works through soil treatment and other methods. It is particularly suitable for modern operating modes such as aerial spraying, achieving cost reduction and pollution reduction while ensuring control efficacy.

8. The application according to claim 6, characterized in that, The weeds include crabgrass (Digitaria sanguinalis) and beggar-ticks (Bidens pilosa).

9. The application according to claim 6 or 7, characterized in that, The herbicidal composition is applied to the soil by spraying after rice sowing but before seedling emergence; the working concentration is 30 L / mu.

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