From May to June every year, when the rice field herbicides are used in the peak season, there are often growers asking why the herbicide should be drained first, and the water should be returned after 24 hours. Can it be undrained or not returned? Especially Large planting households often suffer from herbicide damage or poor weeding effects due to large planting area, untimely drainage, incomplete drainage, untimely return of water, and inadequate water retention, which leads to grass shortage and directly causes rice production to be reduced or rejected.
Using herbicides to drain the water first, returning water after 24 hours, and retaining water for 5 to 7 days, not only can effectively kill weeds, ensure the safety of rice, but also the key to effectively control the secondary damage of weeds. Hubei Ruifengda technical team through survey, analysis, summary as follows, for the majority of growers to refer to.
Why drain water when using herbicides?
Controlling weeds in paddy fields can take advantage of the differences in morphology, physiology, growth and development of rice and weeds and some of the characteristics of herbicides to avoid phytotoxicity to rice, usually in five pathways. Among them, chemical weeding usually adopts four methods: time difference selection, position difference selection, shape selection and physiological selection; physical weeding adopts space selection method. For transplanting and throwing fields, we have a variety of options. We can choose weeds, time difference, morphological difference, physiological difference and spatial difference to control weeds. The live field weeds usually grow before the seeds, grow at the same time as the rice, and even grow ahead of the rice. Because the semi-arid and semi-humid conditions in the field in the early stage of the live field are very beneficial to the weed growth, the difference in position, time difference and space. Can not be used, can only choose the shape difference and space difference for weeding.
The paddy field drains the water before using the herbicide, mainly to let the weeds out of the water surface and fully contact the liquid to achieve a better herbicidal effect. Especially in the live field, the time for weeding is long (usually there will be 2 to 3 peaks of grass in the live field, the first time is 5 to 7 days after sowing, the weed seeds in the soil will germinate a lot; the second time is 10~ after the sowing In 15 days, weeds entered the peak of germination, this time is also the key period of chemical weeding; the third time is 20-40 days after sowing, the weeds remaining in the deep layer of soil germination, if the rice grows better at this time, weed growth Will be in a weak position, will not pose a hazard to rice. However, if the weeding of the second weed is not complete, especially in the field where the gold is more harmful, the drainage is not thorough, the return water is not timely, and the water retention is not in place, which will result in Weeds are catastrophic.), grass ages vary, older grasses can float (especially thousands of gold), young grasses are even germinated, if the effluent is not drained before using the herbicide, the drainage is not complete, the drainage will not be thorough, it will As a result, the young grass did not come into contact with the liquid medicine, causing the failure of weeding and the consequences of the second hazard of weeds.
Why use herbicides to return to water after 24 hours?
After the herbicide is applied for more than 24 hours, the field can be returned to the water. Some materials say 48 hours, and some say 72 hours. What needs to be explained here is that when the temperature in early spring is low, the time of returning water should be delayed a little, but it must be returned within 72 hours after the medicine. When the temperature is high in summer and autumn, back The time of the water should be a little earlier, but it must be 24 hours after the medicine.
Rice, alfalfa, and thousand gold are all gramineous plants, and their genetic relationship is close. In the chemical weeding process, weeds die and the rice does not die because the physiological characteristics of rice and weeds are different. Rice can decompose such herbicides themselves (such as cyhalofoprin, penoxsulam, bispyribyl ether, etc.). . It is required to return water in time. On the one hand, rice is more energetic when it has water, and its ability to dissolve is better, which can prevent phytotoxicity in rice. For example, transplanting and throwing sputum, using amide herbicides such as acetochlor, pretilachlor, butachlor, etc., monocotyledon (rice, valerian, and turmeric) plants act by stimulating the growth point of the bud tip, so use The height of rice and weeds is not the same. Water retention floods the monocotyledonous weeds and leaves the grass, which plays a role in killing grass. The rice heart is above the water surface and is relatively safe. If it is raining heavily or if it is too deep, it will also kill rice. Hubei Ruifengda technical team found in the field investigation, using 40% bispyribyl ether suspension agent after rice 3 leaf 1 heart period 9 ~ 12 g / mu (according to the age of grass can increase the dose, but the maximum should not exceed 12 grams / acre), returned to water after 24 hours, observed after 10 days, the mortality rate of alfalfa can reach more than 90%, almost no effect on rice. In the field where the water is not returned to the water or the water is returned later, the yellowing of the leaves occurs in the rice, especially in the fields that have not returned to the water. The rice will almost always have phytotoxicity, but it usually recovers after 7 to 10 days.
On the other hand, 24 hours of backwater is required to ensure the efficacy of herbicides. Sunshine is one of the important means to promote the development of rice roots (dry long roots, aerobic roots). Of course, this method is also conducive to the development of weed roots. . After using the herbicide, if the water is not returned in time, the lack of water in the field will cause the weed roots to develop rapidly, so that the weeds may pass the herbicide's efficacy, which directly leads to the failure of weeding. In the field investigation, Hubei Ruifengda technical team found that when the prevention of thousands of gold, if not returned in time, it would lead to a large number of gold. Because usually, the 5th leaf is the same as the valerian, the difference is that the thousand gold belongs to the perennial rhizome breeding weed, although the cyhalofop is a systemic herbicide, its main function is to act on the stems and leaves, Old age gold has a strong inhibitory effect, can prevent grass shortage, but can not completely kill weeds. That is to say, cyhalofop-butyl ester can only kill the stems and leaves of thousands of gold, and can not cause damage to the roots (there is a certain relationship with the amount). If the amount of use is insufficient or the water is not returned in time, the root system will develop rapidly. The Hubei Ruifengda technical team found that the growers who used 15% cyhalofoprin water emulsion 100 ml/15 kg water returned to the water 24 hours after the drug (3 to 5 cm in water) and kept water for 5 to 7 days. The effect is particularly outstanding, and there is basically no harm in the late stage. However, the amount of cyhalofoprin used is not enough or the water is not timely. The root system of Qianjin is particularly developed, which provides abundant nutrient protection for the large-scale and rapid propagation of thousands of gold. We often hear the growers say that after using cyhalofoprin, the longer the thousands of gold (the one before application, the one after application, and the damage to the vine), is the reason. If the cyhalofoprin is used and the water is returned in time, the cyhalofoprin kills the stems and leaves of the thousand gold. The roots are submerged in the water and cannot develop rapidly, and the thousand gold can be controlled. Therefore, the return of water after the herbicide is used is undoubtedly worse for weeds, which can improve the effect of killing grass.
Why use water for 5 to 7 days when using herbicides?
The role of water retention is very simple, that is, to achieve the purpose of water control. The use of a layer of water (usually 3 to 5 cm, not too deep or too shallow) serves to close the secondary germination of weeds. Reasonable water retention can promote the early development of strong seedlings in rice, and achieve the effect of controlling water by grass, promoting seedling and inhibiting grass, and improving the efficacy of herbicides. After 5 to 7 days of water retention, combined with topdressing, rice has occupied the space of the field, and it is difficult to cause damage after weeds are germinated. Hubei Ruifengda technical team found that long-term water-breaking fields can easily cause grass shortage; and reasonable water retention can increase chemical weeding effect by 40%-60%.
Through a large number of field investigations, practices, analysis and summarization, Hubei Ruifengda technical team recommended the use of herbicides in paddy fields. The drainage must be thoroughly (drained) and returned to water in time (after 24 hours). Water retention should be in place (3~5). Cm, 5-7 days).
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(Source: Public Welfare Plant Protection )
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