[Chemical Knowledge]：Properties and Uses of Herbicides

The nature and use
of herbicides
herbicide refers to can make weeds completely or selectively produce dead chemical, also known as herbicides, to destroy or inhibit the growth of plants of a class of substances. Herbicides can be classified by mode of action, site of application, source of compound, etc. Classification according to the mode of action is the main classification method of herbicides, which can be divided into selective herbicides and killing herbicides. Selective herbicides, especially derivatives of nitrophenol, chlorophenol and carbamic acid, are mostly effective. The development of herbicides in the world is becoming more and more stable, mainly developing varieties with high efficiency, low toxicity, broad spectrum and low dosage, and disposable treatment agents with little environmental pollution have gradually become the mainstream. The commonly used varieties are organic compounds, which can be widely used to control weeds, miscellaneous irrigation, miscellaneous trees and other harmful plants in farmland, orchards, flower nurseries, grasslands and non-cultivated land, railway lines, rivers, reservoirs, warehouses and other places.

1. herbicide type

1. according to the mode of action classification
(1) selective herbicide: herbicide for different kinds of seedlings, resistance degree is also different, this agent can kill weeds, and harmless to seedlings. Such as Gaicaoneng, trifluralin, promicin, simazine, and gol herbicides.
(2) Killing herbicides: herbicides are toxic to all plants. As long as they touch the green part, regardless of seedlings and weeds, they will be harmed or killed. It is mainly used before sowing, before emergence after sowing, and on the main and secondary roads of the nursery. such as glyphosate.
2. Classification
according to the movement of herbicides in plants (1) Touch-killing herbicides: when the pesticide comes into contact with weeds, it only kills the part in contact with the pesticide, which plays a local killing effect and cannot be conducted in plants. Only the above-ground part of the weed was killed, and less effective on the underground part of the weed or perennial deep-rooted weeds with underground stems. Such as weed ether, paraquat and so on.
(2) systemic conduction herbicide: after the medicament is absorbed by the root or leaf, bud sheath or stem, it is transmitted to the plant body and causes the plant to die. Such as glyphosate, promethium net and so on.
(3) Internal absorption conduction and contact killing comprehensive herbicide: it has the dual functions of internal absorption conduction and contact killing, such as fenoxamine.
3. according to the chemical structure classification
(1) inorganic compounds herbicide: made from natural mineral raw materials processing, does not contain carbon compounds, such as potassium chlorate, copper sulfate and so on.
(2) organic compounds herbicide: mainly by benzene, alcohol, fatty acid, organic amine and other organic compounds synthesis. Such as ethers-gol, all three nitrogen benzene-promethamphetamine, substituted urea-herbicide No. 1, etc.

2. herbicide use method

1. soil treatment: the herbicide will be directly sprayed on the soil to form a certain thickness of the layer, when the weed seeds of young buds, seedlings and their roots are contact absorption and play a role in killing grass. The advantages of this method are timely application, less dosage, good effect and high efficiency. Disadvantages in arid areas difficult to work, will damage the roots of crops, reduce soil fertility.
2. Foliar treatment: A method in which the herbicide is sprayed directly onto the leaves of the plant. The amount of this drug is less, spray evenly, and let all weeds be covered as much as possible.
3. Smudge application: when weeds are higher than crops, apply herbicides with strong internal absorption on weeds. Smear pesticide dosage is small, safe to crops, economic and effective. However, the underground part of weeds is difficult to remove and has certain limitations.

3. herbicides pay attention to matters of

1. strict control of temperature: herbicides are generally marked with 5 ℃ or 10 ℃ can be used, so here said 5 ℃, 10 ℃, what refers to the use of the temperature or the lowest temperature? The answer is the latter. The temperature mentioned here refers to the lowest temperature, that is to say, the lowest temperature can be used above 5 ℃, and the temperature should not be lower than this two days before and after herbicide application.
2. Prohibition of drug use in windy days: Drug use in windy days is easy to cause herbicides to drift away, not to mention the poor effect, but also may drift to crops sensitive to herbicides and cause phytotoxicity, so we must pay attention to the prohibition of drug use in windy days.
3. Prohibition of medication in severe weather: The use of herbicides before and after heavy rain and before the arrival of cold air affects the weeding effect on the one hand, and on the other hand, it is easy to cause phytotoxicity. These are all severe weather, especially in the 7 days before the late spring cold. Use herbicides, pay more attention to weather forecast when using drugs in winter.
4. Do not re-spray or miss-spray: use herbicides must be evenly sprayed. If weeds in places where spraying is missed or less sprayed are unevenly treated, the prevention effect is definitely not good. Remember not to re-spray, as re-spraying of wheat herbicides is easy to cause pesticide damage!
5. Herbicides are not recommended to be mixed with other pesticides, fungicides and control agents: on the one hand, mixing may affect the efficacy, on the other hand, it is easy to cause harm!
6. Be sure to pay attention to the second dilution: especially powder herbicides, the second dilution is especially important! Because powder herbicides are easily precipitated if poured directly into the sprayer, resulting in uneven spraying and drug damage! After the secondary dilution is completed, pour it into the sprayer and stir it evenly, so as to have uniform drug effect and reduce the occurrence of drug damage! The development trend of

4. herbicides

With the continuous development of the global economy, environmental issues have attracted more and more attention. In the field of raw materials for chemical production, herbicides are an important class of pesticide products.