阅读说明：本技术 一种长效水稻苗前专用除草剂及其制备方法 (Long-acting special herbicide for rice before seedling and preparation method thereof ) 是由 陈君 陈伯韬 翟志勇 冯辉 陈昌才 温建平 王小苹 狄正海 于 2020-11-30 设计创作，主要内容包括：本发明提供一种长效水稻苗前专用除草剂及其制备方法,包括:(1)制备脲醛预聚液；(2)由苄嘧磺隆、双草醚、异恶草酮和丙酮超声搅拌混合,得除草剂A初混液；由氰氟草酯、异丙甲草胺和丙酮超声搅拌混合,得除草剂B初混液；(3)将除草剂A初混液、壳聚糖、复合乳化剂和水,二次超声波搅拌混合,得除草剂A乳化液；将除草剂B初混液、菇类蛋白多糖、阿拉伯胶、复合乳化剂和水二次超声波搅拌混合,得除草剂B乳化液；(4)分别与脲醛预聚液混合；(5)喷雾干燥；(6)将微囊颗粒A与微囊颗粒B按照质量比3:(0.5～1)混合；该除草剂对阔叶杂草和禾本科杂草的防效好,且持续封草效果好,并可保持良好稳定的出苗数和生长质量。(The invention provides a long-acting special herbicide for rice before seedling and a preparation method thereof, which comprises the following steps of (1) preparing urea formaldehyde pre-polymerization liquid; (2) bensulfuron-methyl, bispyribac-sodium, clomazone and acetone are ultrasonically stirred and mixed to obtain a primary mixed solution of a herbicide A; the cyhalofop-butyl, the metolachlor and the acetone are stirred and mixed by ultrasonic to obtain a primary mixed solution of a herbicide B; (3) mixing the primary mixed solution of the herbicide A, chitosan, a composite emulsifier and water by secondary ultrasonic stirring to obtain an emulsified solution of the herbicide A; mixing the primary mixed solution of the herbicide B, mushroom proteoglycan, Arabic gum, a composite emulsifier and water by secondary ultrasonic stirring to obtain an herbicide B emulsion; (4) respectively mixing the urea formaldehyde prepolymer solution with the urea formaldehyde prepolymer solution; (5) spray drying; (6) mixing the microcapsule particles A and the microcapsule particles B according to the mass ratio of 3 (0.5-1); the herbicide has good control effect on broadleaf weeds and grassy weeds, has good continuous grass sealing effect, and can keep good and stable seedling emergence number and growth quality.)

1. A preparation method of a long-acting special herbicide for rice before seedling is characterized by comprising the following steps: the method comprises the following steps:

(1) heating urea and formaldehyde solution in water bath for mixing reaction to obtain urea formaldehyde pre-polymerization solution;

(2) carrying out ultrasonic stirring and mixing on bensulfuron-methyl, bispyribac-sodium, clomazone and acetone according to the weight ratio of (0.2-0.5) to (0.8-1.2) to (2-3) to (14-18) to obtain a primary mixed solution of a herbicide A; carrying out ultrasonic stirring and mixing on cyhalofop-butyl, metolachlor and acetone according to the weight ratio of (1-3) to (16-28) to obtain a primary mixed solution of a herbicide B;

(3) mixing the primary mixed liquid of the herbicide A, chitosan, a dispersing agent, a composite emulsifier and water according to the weight ratio of (5-8) to (2-3) to (0.5-1) to (3-5) to (20-35), and carrying out secondary ultrasonic stirring and mixing to obtain an emulsion of the herbicide A; mixing the herbicide B primary mixed solution, mushroom proteoglycan, Arabic gum, a dispersing agent, a composite emulsifier and water according to the weight ratio of (6-10) to (1-2) to (4-6) to (1-1.5) to (30-40), and carrying out secondary ultrasonic stirring and mixing to obtain a herbicide B emulsion;

(4) mixing the herbicide A emulsion and the herbicide B emulsion with the urea formaldehyde pre-polymer respectively, uniformly stirring at a high speed of 2000-3000 r/min, adjusting the pH value to 2.0-2.5 by ammonium chloride, and standing for 3-5 h to obtain a herbicide A mixed solution and a herbicide B mixed solution respectively;

(5) respectively carrying out spray drying on the mixed solution of the herbicide A and the mixed solution of the herbicide B to obtain microcapsule particles A and microcapsule particles B;

(6) and mixing the microcapsule particle A and the microcapsule particle B according to the mass ratio of 3 (0.5-1) to obtain the special herbicide for rice before seedling.

2. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: in the step (1), the mixing molar ratio of the urea to the formaldehyde solution is 1: 2, the water bath reaction temperature is 70-80 ℃, the reaction time is 2-2.5 h, the pH value is 8.0, and the mass concentration of the formaldehyde solution is 37%.

3. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: in the step (2), the ultrasonic mixing frequency is 30-35 kHz, the ultrasonic treatment power is 300-400W, the ultrasonic treatment time is 5-10 min, and the stirring speed is less than 500 r/min.

4. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: in the step (3), the secondary ultrasonic stirring and mixing conditions of the herbicide A emulsion are that the ultrasonic frequency is 50-55kHz, the power of ultrasonic treatment is 500-600W, the stirring speed is 1300-1800 r/min, and the stirring is continuously carried out for 10-15 min at the temperature of 75-80 ℃.

5. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: in the step (3), the secondary ultrasonic stirring and mixing conditions of the herbicide B emulsion are that the ultrasonic frequency is 50-55kHz, the ultrasonic treatment power is 500-600W, the stirring speed is 1200-1300 r/min, the mixture is firstly subjected to ultrasonic mixing at the temperature of 50-60 ℃ for 5-8 min, then heated to 80-85 ℃, and continuously stirred for more than 6 min.

6. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: in the step (4), the weight ratio of the mixed herbicide A emulsion to the urea formaldehyde pre-polymer solution is 5: 8; the weight ratio of the herbicide B emulsion to the urea formaldehyde pre-polymer solution is 2: 5.

7. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: in the step (5), the conditions of spray drying are that the inlet temperature is 173-177 ℃, the outlet temperature is 70-75 ℃, and the feeding flow is 480-485L/h.

8. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: the composite emulsifier comprises the following components in parts by weight: 2-3 parts of styryl phenol polyoxyethylene ether, 5-8 parts of sodium dodecyl benzene sulfonate, 801-3 parts of tween-801 and 0.5-1 part of agricultural emulsion 500.

9. The preparation method of the long-acting special herbicide for rice before emergence according to claim 1, which is characterized in that: the dispersant is sodium lignosulfonate.

10. The special herbicide for rice seedlings, which is prepared by the preparation method of the long-acting special herbicide for rice seedlings according to any one of claims 1 to 9.

Technical Field

The invention relates to the technical field of rice weeding, and particularly relates to a long-acting special herbicide for rice before seedling and a preparation method thereof.

Background

With the continuous development of agricultural mechanization, the rice direct seeding technology is newly developed, and intensive production of rice under the condition of insufficient labor force can be effectively solved. In the early stage of direct seeding of rice, the generation amount of weeds is far higher than that of a cultivated or seedling-throwing paddy field, and the control of the weeds has important influence on the high and stable yield of the direct seeding of the rice.

The weed control of the direct seeding herbicide for rice mainly comprises two periods of soil sealing treatment before seedling after seeding and spraying treatment of stem leaves after seedling. Due to the fact that the base number of weeds in the direct-seeding paddy field is large, the emergence period is long, soil sealing treatment is conducted after seeding and before seedling, and in the process of weed killing, the existing compound herbicide before rice seedling is short in lasting period, low in stability of pesticide effect, easy to be affected by weather, poor in preventing and removing effect of weeds before rice seedling, large in dosage, and easy to affect the emergence and growth effect of rice seedling due to excessive use of the herbicide. Therefore, by improving the pre-emergence compound herbicide and combining with a new preparation process, the long-acting special herbicide for the rice seedlings with good stability is obtained, so that long-acting soil sealing treatment before the rice seedlings is achieved, good pre-emergence weed control is realized, good growth of the rice seedlings is guaranteed, the later weed control pressure is reduced, and the pesticide cost is saved, thereby having important significance.

Disclosure of Invention

In view of the above, the invention provides a long-acting special herbicide for rice before seedling and a preparation method thereof.

The technical scheme of the invention is realized as follows:

the invention provides a preparation method of a long-acting special herbicide for rice before seedling, which comprises the following steps:

(1) heating urea and formaldehyde solution in water bath for mixing reaction to obtain urea formaldehyde pre-polymerization solution;

(2) carrying out ultrasonic stirring and mixing on bensulfuron-methyl, bispyribac-sodium, clomazone and acetone according to the weight ratio of (0.2-0.5) to (0.8-1.2) to (2-3) to (14-18) to obtain a primary mixed solution of a herbicide A; carrying out ultrasonic stirring and mixing on cyhalofop-butyl, metolachlor and acetone according to the weight ratio of (1-3) to (16-28) to obtain a primary mixed solution of a herbicide B;

(3) mixing the primary mixed liquid of the herbicide A, chitosan, a dispersing agent, a composite emulsifier and water according to the weight ratio of (5-8) to (2-3) to (0.5-1) to (3-5) to (20-35), and carrying out secondary ultrasonic stirring and mixing to obtain an emulsion of the herbicide A; mixing the herbicide B primary mixed solution, mushroom proteoglycan, Arabic gum, a dispersing agent, a composite emulsifier and water according to the weight ratio of (6-10) to (1-2) to (4-6) to (1-1.5) to (30-40), and carrying out secondary ultrasonic stirring and mixing to obtain a herbicide B emulsion;

(4) mixing the herbicide A emulsion and the herbicide B emulsion with the urea formaldehyde pre-polymer respectively, uniformly stirring at a high speed of 2000-3000 r/min, slowly adjusting the pH value to 2.0-2.5 by ammonium chloride, and standing for 3-5 h to obtain a herbicide A mixed solution and a herbicide B mixed solution respectively;

(5) respectively carrying out spray drying on the mixed solution of the herbicide A and the mixed solution of the herbicide B to obtain microcapsule particles A and microcapsule particles B;

(6) and mixing the microcapsule particle A and the microcapsule particle B according to the mass ratio of 3 (0.5-1) to obtain the special herbicide for rice before seedling.

Further, in the step (1), the mixing molar ratio of the urea to the formaldehyde solution is 1: 2, the water bath reaction temperature is 70-80 ℃, the reaction time is 2-2.5 h, the pH value is 8.0, and the mass concentration of the formaldehyde solution is 37%.

Further, in the step (2), the frequency of ultrasonic mixing is 30-35 kHz, the power of ultrasonic treatment is 300-400W, the time of ultrasonic treatment is 5-10 min, and the stirring speed is less than 500 r/min.

Further, in the step (3), the secondary ultrasonic stirring and mixing conditions of the herbicide A emulsion are that the ultrasonic frequency is 50-55kHz, the power of ultrasonic treatment is 500-600W, the stirring speed is 1300-1800 r/min, and the stirring is continued for 10-15 min at 75-80 ℃.

Further, in the step (3), the secondary ultrasonic stirring and mixing conditions of the herbicide B emulsion are that the ultrasonic frequency is 50-55kHz, the power of ultrasonic treatment is 500-600W, the stirring speed is 1200-1300 r/min, the mixture is firstly subjected to ultrasonic mixing at the temperature of 50-60 ℃ for 5-8 min, then slowly heated to 80-85 ℃, and continuously stirred for more than 6 min.

Further explaining, in the step (4), the weight ratio of the herbicide A emulsion to the urea formaldehyde pre-polymer solution is 5: 8; the weight ratio of the herbicide B emulsion to the urea formaldehyde pre-polymer solution is 2: 5.

Further, in the step (5), the conditions of spray drying are that the inlet temperature is 173-177 ℃, the outlet temperature is 70-75 ℃, and the feed flow is 480-485L/h.

Further explaining, the composite emulsifier comprises the following components in parts by weight: 2-3 parts of styryl phenol polyoxyethylene ether, 5-8 parts of sodium dodecyl benzene sulfonate, 801-3 parts of tween-801 and 0.5-1 part of agricultural emulsion 500.

Further, the dispersant is sodium lignosulfonate.

The special herbicide for rice seedlings is prepared by the preparation method of the long-acting special herbicide for rice seedlings.

Compared with the prior art, the invention has the beneficial effects that: according to the preparation method of the long-acting special herbicide for the rice before the seedling stage, the obtained special herbicide for the rice before the seedling stage has good control effect on broadleaf weeds and gramineous weeds, the control effect can be more than 89.2%, the continuous grass sealing effect is good, and the control effect can be kept more than 83.3% after the herbicide is applied for 45 days; and basically has no influence on rice seedling emergence, and can keep good and stable seedling number and growth quality. Compared with the existing herbicide in seedling stage, the invention has the advantages that:

1. the invention adopts the ternary herbicide which takes bensulfuron methyl, bispyribac-sodium and clomazone as effective components to be mixed and compounded, and the ternary herbicide is mixed and compounded with the binary herbicide which takes cyhalofop-butyl and metolachlor as effective components to be used for comprehensively preventing and killing weeds before rice seedlings, has good prevention effect and is safe to the growth of the rice seedlings.

2. According to different multi-element compounded herbicide primary mixed solutions, chitosan and Arabic gum are respectively used as stabilizers to be matched with different herbicide primary mixed solutions, and the primary mixed solutions are combined under a secondary ultrasonic mixing emulsification process, so that a micro-membrane fusion effect is favorably formed, a better protection effect is achieved on effective components, and the emulsification effect of the herbicide primary mixed solutions is fully stabilized.

3. By adding mushroom proteoglycan into the herbicide B primary mixed liquid, the long-acting grass sealing effect is realized, and the stable emergence rate and growth quality of rice seedlings are kept.

4. The fusion effect of the secondary ultrasonic mixed micro-membrane and the coating effect of the urea formaldehyde pre-polymerization liquid ensure that the obtained different micro-capsule particles have stable and better sustained release effect and good effect of continuously sealing grass.

5. Different multi-element compound micro-capsule particles are adopted for effective compounding, so that the obtained special herbicide for rice has long control effect, the dosage is reduced, and the growth of rice seedlings is facilitated.

Detailed Description

In order to better understand the technical content of the invention, specific examples are provided below to further illustrate the invention.

The experimental methods used in the examples of the present invention are all conventional methods unless otherwise specified.

The materials, reagents and the like used in the examples of the present invention can be obtained commercially without specific description.

Example 1-a method for preparing a long-acting pre-emergence herbicide for rice, comprising the steps of:

(1) mixing urea and a formaldehyde solution with the mass concentration of 37% according to the mol ratio of 1: 2, heating and mixing in a water bath at 70 ℃ for 2 hours to react, wherein the pH value is 8.0, and obtaining a urea formaldehyde pre-polymerization solution;

(2) the bensulfuron methyl, the bispyribac-sodium, the clomazone and the acetone are ultrasonically stirred and mixed according to the weight ratio of 0.2:0.8:2:14 to obtain a primary mixed solution of the herbicide A; carrying out ultrasonic stirring and mixing on cyhalofop-butyl, metolachlor and acetone according to the weight ratio of 1:1:16 to obtain a primary mixed solution of a herbicide B;

wherein the ultrasonic mixing frequency is 30kHz, the ultrasonic treatment power is 300W, the ultrasonic treatment time is 5min, and the stirring speed is 200 r/min;

(3) mixing the herbicide A primary mixed solution, chitosan, a dispersant, a composite emulsifier and water according to the weight ratio of 5:2:0.5:3:20, and carrying out secondary ultrasonic stirring and mixing, wherein the ultrasonic frequency is 50kHz, the ultrasonic treatment power is 500W, the stirring speed is 1300r/min, and the mixture is continuously stirred for 10min at the temperature of 75 ℃; obtaining herbicide A emulsion; mixing a herbicide B primary mixed solution, mushroom proteoglycan, Arabic gum, a dispersing agent, a composite emulsifying agent and water according to a weight ratio of 6:1:4:1:30, carrying out secondary ultrasonic stirring and mixing, wherein the ultrasonic frequency is 50kHz, the ultrasonic treatment power is 500W, the stirring speed is 1200r/min, carrying out ultrasonic mixing at the temperature of 50 ℃ for 5min, then slowly heating to 80 ℃, and continuously stirring for 7min to obtain a herbicide B emulsion;

wherein, the composite emulsifier comprises the following components in parts by weight: 2 parts of styryl phenol polyoxyethylene ether, 5 parts of sodium dodecyl benzene sulfonate, 801 parts of tween-801 and 0.5 part of agricultural emulsion No. 500; the dispersant is sodium lignosulfonate;

(4) mixing the herbicide A emulsion and the herbicide B emulsion with the urea formaldehyde pre-polymer respectively, uniformly stirring at a high speed of 2000r/min, slowly adjusting the pH value to 2.0 by ammonium chloride, and standing for 3 hours to obtain a herbicide A mixed solution and a herbicide B mixed solution respectively;

wherein the weight ratio of the mixed herbicide A emulsion to the urea formaldehyde pre-polymer solution is 5: 8; the weight ratio of the mixed herbicide B emulsion to the urea formaldehyde pre-polymer solution is 2: 5;

(5) respectively carrying out spray drying on the mixed solution of the herbicide A and the mixed solution of the herbicide B at the inlet temperature of 173 ℃, the outlet temperature of 70 ℃ and the feeding flow rate of 480L/h to obtain microcapsule particles A and microcapsule particles B;

(6) mixing the microcapsule particle A and the microcapsule particle B according to the mass ratio of 3:0.5 to obtain the special herbicide for rice before seedling

Example 2-a method for preparing a long-acting pre-emergence herbicide for rice, comprising the steps of:

(1) mixing urea and a formaldehyde solution with the mass concentration of 37% according to the mol ratio of 1: 2, heating and mixing in a water bath at the temperature of 80 ℃, reacting for 2.5 hours, and obtaining a urea formaldehyde pre-polymerization solution, wherein the pH value is 8.0;

(2) the bensulfuron methyl, the bispyribac-sodium, the clomazone and the acetone are ultrasonically stirred and mixed according to the weight ratio of 0.5:1.2:3:18 to obtain a primary mixed solution of the herbicide A; carrying out ultrasonic stirring and mixing on cyhalofop-butyl, metolachlor and acetone according to the weight ratio of 3:3:28 to obtain a primary mixed solution of a herbicide B;

wherein the ultrasonic mixing frequency is 35kHz, the ultrasonic treatment power is 400W, the ultrasonic treatment time is 10min, and the stirring speed is 400 r/min;

(3) mixing the primary mixed liquid of the herbicide A, chitosan, a dispersing agent, a composite emulsifier and water according to the weight ratio of 8:3:1:5:35, stirring and mixing by secondary ultrasonic wave, wherein the ultrasonic frequency is 55kHz, the power of ultrasonic treatment is 600W, the stirring speed is 1800r/min, and continuously stirring for 15min at 80 ℃ to obtain an emulsified liquid of the herbicide A; mixing a herbicide B primary mixed solution, mushroom proteoglycan, Arabic gum, a dispersing agent, a composite emulsifying agent and water according to a weight ratio of 10:2:6:1.5:40, stirring and mixing the mixture by secondary ultrasonic wave, wherein the ultrasonic frequency is 55kHz, the power of ultrasonic treatment is 600W, the stirring speed is 1300r/min, firstly ultrasonically mixing the mixture at the temperature of 60 ℃ for 8min, then slowly heating the mixture to 85 ℃, and continuously stirring the mixture for 8min to obtain a herbicide B emulsion;

wherein, the composite emulsifier comprises the following components in parts by weight: 3 parts of styryl phenol polyoxyethylene ether, 8 parts of sodium dodecyl benzene sulfonate, 8 parts of tween-803 and 1 part of agricultural emulsion 500; the dispersant is sodium lignosulfonate;

(4) mixing the herbicide A emulsion and the herbicide B emulsion with the urea formaldehyde pre-polymer respectively, uniformly stirring at a high speed of 3000r/min, slowly adjusting the pH value to 2.5 by ammonium chloride, and standing for 5 hours to obtain a herbicide A mixed solution and a herbicide B mixed solution respectively;

wherein the weight ratio of the mixed herbicide A emulsion to the urea formaldehyde pre-polymer solution is 5: 8; the weight ratio of the mixed herbicide B emulsion to the urea formaldehyde pre-polymer solution is 2: 5;

(5) respectively carrying out spray drying on the mixed solution of the herbicide A and the mixed solution of the herbicide B at the inlet temperature of 177 ℃, the outlet temperature of 75 ℃ and the feeding flow rate of 485L/h to obtain microcapsule particles A and microcapsule particles B;

(6) and mixing the microcapsule particles A and the microcapsule particles B according to the mass ratio of 3:1 to obtain the special herbicide for rice before seedling.

Example 3-a method for preparing a long-acting pre-emergence herbicide for rice, comprising the steps of:

(1) mixing urea and a formaldehyde solution with the mass concentration of 37% according to the mol ratio of 1: 2, heating and mixing in a water bath at the temperature of 75 ℃ for reaction for 2.0h, wherein the pH value is 8.0, and obtaining a urea formaldehyde pre-polymerization solution;

(2) the bensulfuron methyl, bispyribac-sodium, clomazone and acetone are ultrasonically stirred and mixed according to the weight ratio of 0.3:1.0:2.5:16 to obtain a primary mixed solution of a herbicide A; carrying out ultrasonic stirring and mixing on cyhalofop-butyl, metolachlor and acetone according to the weight ratio of 2:2:20 to obtain a primary mixed solution of a herbicide B;

wherein the ultrasonic mixing frequency is 35kHz, the ultrasonic treatment power is 350W, the ultrasonic treatment time is 8min, and the stirring speed is 300 r/min;

(3) mixing the herbicide A primary mixed solution, chitosan, a dispersant, a composite emulsifier and water according to the weight ratio of 7.5:2.5:0.8:4:28, stirring and mixing by secondary ultrasonic wave, wherein the ultrasonic frequency is 55kHz, the power of ultrasonic treatment is 550W, the stirring speed is 1600r/min, and continuously stirring for 13min at 78 ℃ to obtain a herbicide A emulsion; mixing a herbicide B primary mixed solution, mushroom proteoglycan, Arabic gum, a dispersing agent, a composite emulsifying agent and water according to a weight ratio of 8:1.5:5:1.2:35, stirring and mixing the mixture by secondary ultrasonic wave, wherein the ultrasonic frequency is 55kHz, the power of ultrasonic treatment is 550W, the stirring speed is 1250r/min, firstly performing ultrasonic mixing at the temperature of 55 ℃ for 6min, then slowly heating to 85 ℃, and continuously stirring for 10min to obtain a herbicide B emulsion;

wherein, the composite emulsifier comprises the following components in parts by weight: 2.5 parts of styryl phenol polyoxyethylene ether, 6 parts of sodium dodecyl benzene sulfonate, 0.8 part of tween-802 and 500 parts of agricultural emulsion; the dispersant is sodium lignosulfonate;

(4) mixing the herbicide A emulsion and the herbicide B emulsion with the urea formaldehyde pre-polymer respectively, uniformly stirring at a high speed of 2500r/min, slowly adjusting the pH value to 2.0 by ammonium chloride, and standing for 4 hours to obtain a herbicide A mixed solution and a herbicide B mixed solution respectively;

wherein the weight ratio of the mixed herbicide A emulsion to the urea formaldehyde pre-polymer solution is 5: 8; the weight ratio of the mixed herbicide B emulsion to the urea formaldehyde pre-polymer solution is 2: 5;

(5) respectively carrying out spray drying on the mixed solution of the herbicide A and the mixed solution of the herbicide B at the inlet temperature of 175 ℃, the outlet temperature of 73 ℃ and the feeding flow rate of 482L/h to obtain microcapsule particles A and microcapsule particles B;

(6) and mixing the microcapsule particles A and the microcapsule particles B according to the mass ratio of 3:0.8 to obtain the special herbicide for rice before seedling.

Comparative example 1-method for preparing a long-acting pre-emergence herbicide for rice according to example 3, with the difference that: in the step (3), the herbicide A primary mixed solution, the herbicide B primary mixed solution, chitosan, mushroom proteoglycan, Arabic gum, a dispersing agent, a composite emulsifying agent and water are directly mixed according to the weight ratio: mixing at a ratio of 7.5:8:2.5:1.5:5:5.2:63, and stirring and mixing by ultrasonic waves for the second time to obtain a herbicide emulsion; and as in example 3, the pre-polymerized solution is mixed with urea formaldehyde pre-polymerized solution and spray dried to obtain the herbicide special for rice seedlings.

Comparative example 2-method for preparing a long-acting pre-emergence herbicide for rice according to example 3, with the difference that: in the step (3), chitosan is not added into the herbicide A primary mixed liquid, and Arabic gum is not added into the herbicide B primary mixed liquid.

Comparative example 3-method for preparing a long-acting pre-emergence herbicide for rice according to example 3, with the difference that: in the step (3), mushroom proteoglycan is not added into the herbicide B primary mixed liquid.

Comparative example 4-method for preparing a long-acting pre-emergence herbicide for rice according to example 3, with the difference that: in the step (6), the mass ratio of the microcapsule particles A to the microcapsule particles B is 5: 0.5.

The herbicides prepared in examples 1 to 3 and comparative examples 1 to 4 were subjected to field efficacy experiments.

The experimental method comprises the following steps: selecting test field with moderate soil fertility and good irrigation and drainage conditions, setting 8 treatments in total, repeating each treatment for 3 times, and making the area of the cell be 60m²On the next day after direct seeding of rice, the herbicides of examples 1 to 3 and comparative examples 1 to 4 were mixed according to the experimental design to prepare spray agents, and each agent was uniformly sprayed 1 time per 667m in each experimental area²The dosage is 45g, water is added for 30kg, and the control group is clear water control, and the daily field management is consistent in each district.

After 15d, 25d and 45d after application, the weed amount of each plot was counted, wherein 5 points were randomly selected for each treatment and 0.5m was investigated for each point²(ii) a Control effect (%) - (control weed amount-treatment area weeding amount)/control weeding amount]X is 100%; and investigating the influence and growth condition of the rice seedlings by 15d and 25d after the medicament is used, and the results are shown in the following table:

TABLE 1 Effect of different herbicides on blocking weeds in Rice field

As can be seen from the above table, the special herbicide for rice before seedling prepared by the invention has good control effect on broadleaf weeds and grassy weeds, the control effect can be more than 89.2%, the continuous grass sealing effect is good, and the control effect can be kept more than 83.3% after 45 days of pesticide application. Compared with the example 3, the control effect of the comparative examples 1 and 2 on the broadleaf weeds and the grassy weeds is obviously reduced, and particularly after 45 days of pesticide application, the control effect is lower than 75 percent. The invention is shown to be favorable for forming a microfilm fusion effect under the process of combining different multi-element compounded herbicide primary mixed liquid with secondary ultrasonic mixed emulsification, plays a better protection role on effective components, ensures that the emulsification effect of the herbicide primary mixed liquid is fully and stably, and obtains different microcapsule particles with stable and better particle slow release effect and good continuous grass sealing effect.

TABLE 2 Effect of different herbicides on Rice emergence

The results in the table show that the special herbicide for rice before seedling emergence prepared by the invention basically has no influence on rice seedling emergence, and can keep good and stable seedling emergence number and growth quality. Compared with the embodiment 3, the comparative examples 3 and 4 have the advantages that the seedling yield per mu in the comparative example 3 is obviously reduced, and the growth rate of the seedlings is reduced, which shows that the long-acting grass sealing effect is realized, and the stable emergence rate and the stable growth quality of the rice seedlings are favorably maintained by adding the mushroom proteoglycan into the herbicide B primary mixed solution. The reduction of the seedling yield per mu in the comparative example 4 shows that the invention adopts different multi-component compound microcapsule particles to carry out effective compounding, and has certain influence on the seedling yield and growth of rice seedlings.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.