Why can herbicides only remove weeds but not seedlings?

Herbicide. This chemical use,It makes full use of the difference between crops and weeds, so as to only remove weeds and not seedlings. <>

First, starting from the difference in plant morphology and structure, although weeds and crops are the same plant, butThe two are very different in morphological structure, and the degree of tolerance to drugs is also completely different. Our common weeds are classified as sharp-leaved, broad-leaved or sedge.

Crops are also spiky and broad-leaved. As a simple example, wheat is a sharp-leaved plant, so if you use broad-leaved herbicides in wheat fields, such as besulfuron-methyl, these pesticides will only take effect on broad-leaved weeds, and will not affect the growth of wheat at all. <>

Second, for example, the time difference is used for sealing herbicides.

There are many types of herbicides used in principle, except for the more commonly used spraying type to control weeds, as well as closed weeding. Occlusive herbicides, also known as soil treatment agents, are sprinkled on the soil with a protective film on top of the soil. However, the main function of this film is not protection, but weeding.

For example, after corn planting, farmers sprinkle a sealing herbicide immediately. Because in the normal growth environment, weeds will break the soil earlier than corn, and the weeds after breaking the soil will absorb the herbicide solution and wilt directly. Late-growing corn can grow normally.

3. Herbicides should be used with safety agentsWith the progress of science, the safety measures of herbicides themselves are gradually rising. The crop herbicides sold today are all paired with a bottle of adjuvant, which is what we call a safety agent. The presence of this adjuvant can protect crops from herbicides to the greatest extent.

Different crops have different safety agents, and the most amazing thing is that they don't work on weeds. In the end, it plays a role in protecting crops and eliminating weeds. <>

The above three points are the reasons why herbicides only kill weeds and not seedlings. Of course, there are herbicides that are more toxic and can kill all green plants, but they are not used in farmland. After all, if the farmland is no longer growing crops, what will the farmers do?

Because weeds and crops are fundamentally different, when spraying herbicides, there will be some drugs that specifically target weeds, and crops are carried with antibodies to herbicides.

The herbicide can only control the weeds but not the seedlings, because the ingredients of the herbicide only have an effect on the grass and can play a role in elimination, but it will not cause excessive damage to the seedlings.

The efficacy of herbicides is selective, generally based on the cotyledons of plants, weeds are monocots with low requirements for auxin, crops are generally dicots with high requirements for auxin, and the auxin content in herbicides is good to inhibit the growth of weeds.

Improper use of herbicides can cause significant losses to crops. WhenWhen herbicides don't work, try manual weeding and planting herbicide-resistant varieties to control those weeds. Although chemical weed control has always been the main measure of weed control, it has always been a difficult problem for weed control because the mechanism of action of conventional herbicides will be differentiated.

1: Manual weeding

Time-consuming and laborious manual weeding can be called a safe and effective industry master, but when operating, it needs to be targeted at small planting areas. If you have as much as 100 acres of fertile land, I believe that those who choose this method must have a first-class economic team to dare to operate. But I have to say that as the earliest weeding measures, when the area is appropriate and the manpower is enough, for those perennial weeds that are difficult to control, the effect of weeding and rooting is still very good.

2: Grass to suppress grass.

However, when labor is in short supply, herbicides can not solve the pain points, so as long as we find ecological measures to inhibit weeds and replace herbicides for weeding, we can solve the problem of difficult weeding of plants.

For example, the widely adaptable rat thatch is such an herbaceous plant, which is resistant to cold and high temperatures, and is completely fine for winter. Safe for winter, so there is no need for a second harvest. It can be used directly after planting for 5-7 years at a time, avoiding repeated sowing.

One investment will directly reduce the cost of weeding for 5-7 years, so as long as you choose the right variety and cycle it every year, the weeding effect will be ideal.

Whether in the orchards of the south or the tea plantations of the north, weeding is a homework that cannot be ignored. A hundred-acre orchard owner said that it costs tens of thousands of yuan to calculate the orchard weeding alone every year. Sometimes you have to hire someone to buy a weeder or herbicide, so it costs money to buy a machine, and the grass may not be clean.

Therefore, when spring ploughing and autumn harvest become the industry that farmers rely on for survival, it will set off a boom in crop management, and we can only continue to make progress and learn in weeding, and carry out chemical weeding and other measures in a timely manner. Only by scientifically managing these fields can we lay a firm foundation for a bumper harvest of autumn grain.

If it really doesn't work, or if it really doesn't work, then some farmers should respond accordingly, and there may be a problem with the pesticide or the herbicide has expired. Should repurchase it.

After this happens, you can choose the method of manual weeding, and then you can also avoid the period when the grass grows more lushly, and you can change to a new herbicide, be sure to pay attention to the ingredients.

I don't think the herbicide works, probably because the spraying time is not right, and it should be sprayed in the evening.

It works, but the effect on crops is not very large, and generally the herbicide can only fully exert its effective effect two to three hours after spraying.

Herbicides are chemicals that kill weeds or harmful plants without affecting the normal growth of crops. It can be used to control weeds in farmland or kill weeds or shrubs on non-agricultural land.

According to its action characteristics, it can be divided into selective herbicides and biocidal herbicides, selective herbicides refer to the use of a certain dose and concentration range, can selectively kill some kinds of plants, and other kinds of plants are harmless.

Herbicides are still very effective, if there are more weeds, herbicides are used in the world, then the weeds can basically be removed, but relatively speaking, it is necessary to use an appropriate amount of time, and it is necessary to pay attention to the scope of spraying.

Weeds have very vigorous growth and fecundity, which will absorb water and nutrients in the soil, compete for the growth space of crops, make crops grow slowly, and the more weeds there are, the greater the impact on crops. In addition, too many weeds can easily lead to pests and diseases, resulting in reduced crop yields or even death, so whether it is planting crops or raising flowers and plants in pots, we need to remove weeds regularly.

There are several main methods of weeding:

Manual weeding: The method of effectively controlling weeds through manual uprooting, hoeing and other measures is the most primitive and simple method of weeding.

Mechanical weeding: Mechanical weeding is a method of weeding by using mechanically driven weeding machinery at a suitable stage of crop growth, according to the occurrence and harm of weeds.

Chemical weeding: The use of chemicals to suppress or eliminate weeds, such as herbicides, pesticides, etc.

In addition to weeding after weeds have grown, it is best to carry out physical control in advance. Physical control refers to the use of physical methods, such as flame, high temperature, electricity, radiation and other means to kill and control weeds, including fire weeding, electricity and microwave weeding, film covering and weeding, etc. Physical control methods are safer and have less impact on the land than chemical control methods.

1. Weeds will occupy the aboveground and underground voids, affecting the photosynthesis of crops, and interfering with crop growth. 2. The number of seeds of weeds in early production far exceeds the sowing amount of crops, and the early emergence and fast speed of seedlings are easy to form grass famine.

Weeds compete with crops for water and nutrients in the field, and their root systems are extremely large, and the nutrients that should belong to crops will be plundered by them, resulting in poor growth in the early stage and reduced yield in the later stage.

Farmers have herbicides, why do the grass die but the crops don't?

1. Morphological and structural discrimination.

Although weeds and crops are higher plants, they are different in form and structure, such as common weeds have broad-leaved, sharp-leaved and sedges, and crops also have sharp-leaved broad-leaved branches, for example, wheat belongs to sharp-leaved leaves, sowing Artemisia, pigs, mother-in-law, etc. belong to broad-leaved grasses, at this time choose to play broad-leaved herbicides (such as benzsulfuron, dimethyltetrachloride, chlorofluoropyroxyacetic acid, etc.), these agents only have an effect on broad-leaved weeds, and wheat belongs to sharp-leaved leaves (specific molecular structure, This article does not go into detail, it involves too many technical terms, and it is not easy to understand), so the weeds are killed, and the crops grow normally.

2. The principle of position difference.

The principle of the difference is mainly in the closed herbicide, or a small example to illustrate, in the case of corn, many friends will play the closed herbicide in time after the corn is sown, when the liquid is played, it will form a layer of film on the soil, under normal circumstances, weeds come out earlier than corn, at this time the weeds will absorb the liquid of the closed herbicide, resulting in death, and the corn is late, it will sprout and grow normally under the protection of the soil cover, which is the principle of the difference in the position.

3. Safety agent.

Now many crop post-emergence herbicides, are added with safety agents (wheat, corn, peanuts, etc.), such as the removal of wheat and wheat methyldisulfuron, when purchasing, there will be a bottle of adjuvant, the adjuvant is generally a safety agent, in such as corn herbicide, nicosulfuron, mesotrione, atrazine + adjuvant, this adjuvant is actually a safety agent, the role of the safety agent is to protect crops from being harmed by herbicides, and these safety agents do not work for weeds (the specific principle is also more complicated, Later, there is time, the little helper can tell you about the safety agent, welcome to pay attention), the end result is the death of weeds, and the normal growth of crops.

The main reason why the herbicide you hit does not control weeds may be that the quality of the herbicide is faulty, in other words, it may be that its variety does not meet the requirements.

If the herbicide is ineffective against the grass, the first possibility is that the herbicide has a problem with the quality or has expired; The second is that this herbicide is ineffective against some grasses and does not work, in other words, it is not the right symptom.

Different crops have different degrees of sensitivity to herbicides, and if the pesticides are not selected according to the sensitivity of the crops to herbicides, even if they are safe for crops, they are sometimes prone to pesticide damage. Generally, herbicides to control broadleaf weeds are sensitive to dicot crops, and herbicides to control gramineous weeds are sensitive to gramineous crops. For example, 2,4-drops, dimethyltetrachloride, etc. have good effects on broad-leaved weeds, but are sensitive to broad-leaved crops such as cotton, rapeseed, melons, beans, peanuts, potatoes, tobacco, etc., and are prone to pesticide damage.

Acetochlor is suitable for corn, peanut, cotton, soybean and other broad-leaved crops, but it is easy to cause pesticide damage to wheat. Grass cover can be used to control grasses and weeds in the field of broad-leaved crops, but it has serious pesticide damage to grasses such as wheat, rice, millet and corn.