What should I do with corn post-emergence herbicide? Can you spray again?
The use of post-emergence herbicides in corn is not good, and most of them are caused by improper use. There are many factors affecting the effect of herbicides. Even if the herbicides of the same variety have different environments or different operations, the herbicidal effect is very different.
1. The reasons that affect the efficacy of the drug.
(1) Temperature. Herbicide efficacy and phytotoxicity have a lot to do with temperature. Such as nicosulfuron, mesotrione, etc. in the case of lower temperatures, the effect of the drug is slow or poor. In high temperature conditions, it is easy to produce phytotoxicity. Therefore, it is relatively safe to apply the crops around the evening.
(2) Weather conditions. Under drought conditions, the efficacy of the drug often does not work well; after the rain, the soil moisture has a good effect on the soil; the application of the windy weather, the liquid medicine drifts, the drug effect is not good, and the drifting is easy to cause phytotoxicity to other crops.
(3) Soil conditions. It has a great influence on the closed herbicides, especially the land where the soil treatment agent is applied, the organic matter content is high, the liquid medicine is easily adsorbed by the soil, and the dosage is required to be increased. Sandy land with low organic matter content is easy to leak and leaching, the film formation is not good, and the effect of closed weeding is poor.
(4) Soil moisture. The sensation is good, the drug solution is less adsorbed by the soil, which is beneficial to the absorption of weeds and has good efficacy. Under drought conditions, the herbicide active ingredient is absorbed and fixed by the soil, and is not easily absorbed by the weeds, and the drug effect is not good.
(5) How to use it. Water consumption, spray uniformity, leakage spray, re-spraying, and addition of surfactants have significant effects on the efficacy of the drug.
(6) Weed effects. When the grass age is small, the drug resistance is poor, and the drug effect is good; when the grass age is too large, the drug resistance is increased, and the drug effect is poor. In the case of drought, the weeds do not germinate, and the weeds that have been unearthed look small, but the grass age is too large, especially the wettable powder products, the adsorption is poor, the sprayed liquid is quickly dried, the powder falls off, and the effect is not good.
2, the solution.
(1) Soil sealant. After pouring the soil or after the rain, the soil moisture is good, apply the dosage according to the instructions, do not increase or decrease at will, spray evenly on the soil surface to form a drug film, and improve the herbicidal effect.
(2) Post-emergence treatment agent. Try to apply the medicine after pouring the ground or after the rain. The weeds are in a growing state, the pores are open, which is beneficial to the absorption of the liquid; and the plants grow vigorously, and the liquid is quickly transmitted in the body.
The effect of the drug is good and the herbicidal effect is good. When it is dry, it is necessary to increase the water consumption. The water consumption per mu is not less than 30 kg, evenly spray, wet and penetrate the weed stems and leaves to help absorb and conduct.
It is best to use the herb in the 2-5 leaf stage of weeds. At this time, the grass age is small and the herbicidal effect is better. Surfactants such as silicone additives can be added to the chemical solution to increase the ductility of the leaves, promote the absorption of the liquid, and improve the herbicidal effect.
In addition, improper use of corn post-emergence herbicides not only eliminates weeds, but also may cause certain phytotoxicity. Therefore, after the first spraying has no effect, it should be sprayed again at intervals of 2-3 days. More importantly, the use of corn post-emergence herbicides must be done properly to avoid phytotoxicity. Please see below for the specific operation method!
Seven precautions for the use of corn herbicides
First, spraying time
Since the corn seedling herbicide requires 2-6 hours of absorption after spraying, in the 2-6 hours, the effect of the drug is good (that is, the herbicidal effect is ideal) and the temperature and air humidity are closely related.
Spraying in the morning, noon or afternoon when the temperature is high and the weather is dry, because the temperature is high, the light is strong, the liquid evaporates quickly, and after a spraying, the liquid will evaporate, so that the amount of the herbicide entering the weed body is limited, and the absorption is limited. The amount is obviously insufficient, which affects the herbicidal effect; at the same time, when spraying at high temperature and drought, corn seedlings are also prone to phytotoxicity.
The best spraying time is after 6 o'clock in the evening, because the spraying at this time, the temperature is lower after application, the humidity is larger, the liquid stays on the weed leaves for a longer period of time, and the weed can fully absorb the herbicide. The ingredients ensure the herbicidal effect, and the evening medication can also significantly improve the safety of the corn seedlings, and it is not easy to cause phytotoxicity.
Second, spraying method
The amount of medicine used is 15-30 kg for water. See the grass spray, spray carefully, no grass to go, save time and effect.
Third, look at the grass size
When spraying herbicides after spraying corn seedlings, many farmers have a misunderstanding. The smaller the weeds, the smaller the resistance, and the easier the grass is to kill.
Actually, it is not the case. Because the grass is too small, there is no medicine area, and the weeding effect is not ideal. The best grass age is 2 leaves 1 heart to 4 leaves 1 heart period. At this time, the weeds have a certain area of ​​medicine, the weed resistance is not large, and the weeding effect is remarkable.
Fourth, the size of corn seedlings
The best spraying time for corn post-emergence herbicides is corn 2-5 leaf stage. At this time, the corn is highly resistant and is not susceptible to phytotoxicity.
5 leaves can be sprayed in the whole field before the leaves, spray after 6 leaves, the nozzle should be lowered, and the corn seed spray should be sprayed to prevent the poisoning of the liquid (mainly the nicosulfuron without safety agent, if it is safe smoke) Sulfasulfuron can also be sprayed in the whole field.).
V. Corn varieties
Since most of the corn seedling herbicides are currently nicosulfuron-methyl, some corn varieties are sensitive to this ingredient and are prone to phytotoxicity. Therefore, corn fields such as sweet corn, waxy corn and Denghai series cannot be sprayed to prevent drugs. Harmful. For new corn varieties, please test and promote.
Sixth, the problem of pesticide mixing
It is strictly forbidden to spray organic phosphorus insecticides 7 days before and after spraying the herbicides, otherwise it is prone to phytotoxicity. However, it can be mixed with pyrethroids and carbamate insecticides. When spraying, pay attention to avoiding happy leaves and anti-drug solution.
This year, some corn fields have serious occurrences of Swedish flies and thrips. The two small pests can be sprayed with imidacloprid or acetamiprid, but they should not be sprayed with post-emergence herbicides, although imidacloprid or acetamiprid is not organic. Phosphorus, because it is necessary to spray the heart leaf to prevent and control two small pests, if it is mixed with the heart leaf, it is easy to cause phytotoxicity. It can be sprayed separately: the herbicide is sprayed on the front side, followed by the spray of the heart leaf with imidacloprid or acetamiprid.
Seven, the resistance of weed itself
In recent years, the weed resistance of weeds has been strengthened. In order to prevent excessive evaporation of water in the body, weeds grow not so watery and thick, but grow gray and short, and the actual grass age is not small (so-called "Little old man").
Most of these weeds are covered with white small fluff to reduce the evaporation of water. When spraying pesticides in this way, the liquid is topped on the surface of the weed stems and leaves, and the weeds themselves absorb very little, which naturally affects the exertion of the drug effect. Therefore, no matter what medicine is applied during high temperature and drought, it should be added. The amount of liquid sprayed by the large spray does not affect the exertion of the drug effect. Please do not cherish the water when applying pesticides to farmers.
How to use corn post-emergence herbicide correctly
The application of post-emergence herbicides on corn has a great influence on the post-crop crops. If the post-emergence herbicides are used improperly, it is easy to affect the normal growth of post-corn crops. What are the aspects of using herbicides after using corn? ?
First, when applying corn in the field, do: "To distinguish the varieties, do not blindly use drugs"
Since most of the current corn seedling herbicides are nicosulfuron-methyl, some corn varieties are sensitive to this ingredient and are susceptible to phytotoxicity.
Some products indicate that it is forbidden to use on corn inbred lines, sweet corn, waxy corn and other varieties. Therefore, it is said that the post-emergence herbicides are not used in any variety. The product descriptions should be read in detail. Use, improper use, do not use, to prevent phytotoxicity of corn seedlings.
Second, do the medicine : "Secondary dilution, do not mix water, medicine directly" especially powder type medicament
The second dilution is like the chef making noodle porridge. Under the premise of selecting a certain amount of water, first mix a small amount of water with the medicine, then add the remaining water, stir evenly and spray. Avoid the uneven mixing of water and medicine. The weeds in this place where the medicine is sprayed are dead. The weeding effect of the weeds that continue to grow in the place where the water is sprayed.
Third, when spraying, do "do not spray high spray"
The term "low and high" as used herein refers to the low and high temperature. That is to say, before 9:00 am in the middle of the day, the spray is taken after 4 pm. Do not spray in the morning, noon or afternoon when the temperature is high and the weather is dry. The amount of herbicide entering the weed body is limited, the absorption is insufficient, and the herbicidal effect is affected. At the same time, the high temperature spraying corn seedling is also prone to phytotoxicity.
Fourth, do the weeding: "To spray small, do not spray old "
Grab the weeds and leaves one heart to four leaves and one heart. Weeds have a certain area of ​​drug application and a small period of resistance to spraying. Don't wait until the weeds grow to a height of 10 cm or more, and when the eyes are green, they are sprayed.
In the high temperature and dry years, the weeds are short, but due to the long growing time, the roots are developed, forming a "small old grass" with pale gray color. Should increase the amount of liquid sprayed, use no less than 40 kg of liquid per acre, spray the whole plant with weeds, do not hesitate to take the medicine, otherwise it will not achieve the effect of removing weeds.
5. When weeding and controlling insects, do : "To be mixed with pyrethroid pesticides, do not mix with organophosphorus pesticides."
When there is pest in the seedling stage of the corn field, in order to save labor and time, when spraying the post-emergence herbicide, weeding and pest control can be carried out simultaneously. However, the mixed pesticides should be selected from pyrethroids and carbamate insecticides. When spraying, care should be taken to avoid the leaves and prevent the liquid.
Sixth, the corn seedlings after the five leaves to apply : "To fix the spray, do not spray all the fields"
The 2~5 leaf stage of corn is the best spraying time for post-emergence weeding. If the best period is missed and the necessary weeding is necessary, it should be sprayed with the ridge and can not be sprayed all over the field to avoid causing phytotoxicity. Otherwise, the light heart will cause the corn heart to turn yellow, and the heavy ones will turn white and the whole plant will stop growing.
Common corn herbicides
(1) Nicosulfuron phytotoxicity
After 5-10 days of spraying niacinsulfuron, the corn heart leaves chlorotic and yellowing, or irregular chlorotic spots appear in the leaves.
Some of the leaves are curled into a tube shape, the leaf margins are shrunk, and the heart leaves are ox-tailed and cannot be properly withdrawn. Corn growth is inhibited, plants are dwarfed, and partial clumps and secondary stems may be produced. The light damage can restore normal growth and seriously affect the yield.
(2) 2 methyl 4-chloro sodium salt phytotoxicity
The symptoms of phytotoxicity are mainly the distortion of the leaves, the leaves of the heart are formed into clover-like curls, and the leaves are abnormally elongated, the base of the stem is swollen, the roots of the gas are not grown, and the non-artificial tassels cannot be extracted.
The leaves are dark green, when the plants are short, the leaves become yellow and dry; the ears cannot form on the fruit. Therefore, the ears are often grown at the lower nodes of the plants; the lower nodes are fragile and fragile, the roots are underdeveloped, and the roots are short. The lateral root growth is irregular, which has a great impact on the yield, and even the harvest.
(3) Amide herbicides
Acetochlor is a broad-spectrum, high-efficiency, selective pre-emergence soil treatment herbicide that is sprayed on the soil surface before emergence of crops. Gramineous weeds are absorbed by young shoots, broad-leaved weeds are absorbed by roots and shoots, and agents entering the body can interfere with nucleic acid metabolism and protein synthesis, so that the young shoots and young roots stop growing and eventually die.
It can last for about 2 months in the soil. Amide herbicides can inhibit plant respiration and photosynthesis, inhibit the biosynthesis of proteins and RNA, and cause plants to die without producing the substances needed for life.
This type of herbicide can only control the shoots of grass weeds, but can not control adult weeds. The field amounts of alachlor, metolachlor (Dour) and acetochlor are 120-144 grams, 72-144 grams and 25-50 grams of active ingredients per mu (667 square meters).
When the dosage is too large, the corn plants will be dwarfed; some seeds can not be unearthed, growth is inhibited, leaves are deformed, and heart leaves are rolled.
The song can't stretch, sometimes it is whip, the other leaves shrink, and the roots are swollen. Soil stickiness, cold and wet plots can promote the formation of phytotoxicity.
(4) Atrazine herbicide phytotoxicity
The tris-nitrobenzene herbicide mainly aims to interfere with the inhibition of photosynthesis by affecting a series of physiological and biochemical processes in the plant, so that the weed seedlings can not be photosynthetically used, and it is difficult to supplement the necessary organic nutrients and starve to death.
This type of herbicide can effectively control annual grass weeds and broadleaf weeds in the field, and it is safe to use in corn fields.
The main application varieties are atrazine (Atrazine), Caojingjin, cyanazine, etc.; the field use is 67-100 grams and 120-160 grams per mu (667 square meters). However, in the sandy soil with low organic matter content (less than 2.0%) or heavy rain after application, it can cause leaching phytotoxicity.
It is used in the 5th leaf stage of corn seedlings, and it will also cause phytotoxicity to corn under low temperature and rainy conditions. It is characterized by yellowing of corn leaves. Generally, after 10-15 days, the leaf color can turn green and return to normal growth.
Corn remedy solution
The remedial measures that can be taken in the phytotoxicity of corn are mainly to improve the growth conditions of crops, promote crop growth and enhance their resistance to stress. If farming measures are taken, the soil is loosened, and the ground temperature and soil aeration are increased.
According to the growth of the crop, supplement some quick-acting nitrogen, phosphorus, potassium fertilizer or other micro-fertilizer. Foliar fertilization is better, and fertilizer effect is faster. It is also possible to spray some plant growth regulators that encourage and encourage growth , especially for root growth.
But it must be applied according to the needs of the crop, otherwise it will be counterproductive. If there is water on the ground, it should be eliminated early; if pests and diseases occur, it should be prevented as soon as possible. In short, as long as measures are conducive to crop growth and development, it is beneficial to alleviate phytotoxicity and reduce losses.
(1) For the soil-treated herbicides, the phytotoxicity caused by excessive dosage can be used to reduce the phytotoxicity by cultivating, continuous irrigation, and repeated rinsing, and a certain amount of lime powder can be applied during watering. It is used to neutralize the acidic herbicide, thereby washing out the residual agent and reducing the residual herbicide content in the soil. At the same time, strengthen field management and enhance corn resistance.
(2) Strengthen field management and promote early growth of seedlings. It is necessary to strengthen the management of corn fields where phytotoxicity occurs, combined with watering, increase the application of decomposing quick-acting fertilizers such as animal waste, hydrogen carbonate money, nitric acid money, urea, etc., promote root development and regeneration, restore the physiological functions of the damaged corn, and promote The crops grow healthily to reduce the harm of herbicides to crops.
Strengthen cultivating loose soil, break soil compaction, enhance soil permeability, increase ground temperature, promote beneficial microbial activities, accelerate the decomposition of soil nutrients, enhance the absorption capacity of roots for nutrients and water, and restore plant growth and development as soon as possible, reducing phytotoxicity Loss. At the same time, foliar spray 1% - 2% urea, or 0.3% potassium dihydrogen phosphate solution to promote crop growth and development, restore growth as soon as possible.
(3) Spraying plant growth regulators or antidote to different agents . Plant growth regulators have a good stimulating effect on corn growth and development. At the same time, zinc, iron, aluminum and other micro-fertilizers and foliar fertilizers can be used to promote crop growth and effectively reduce phytotoxicity. Common plant growth regulators include gibberellic acid, brassinolide vinegar, and sodium nitrophenolate.
Herbicide antidote can reduce or eliminate the toxicity of herbicides to crops. For example, tea is a selective seed dressing protectant that can be absorbed by seeds and inhibits damage to crops in roots and leaves. These drugs can protect corn from acetochlor, butachlor, and isoamylamine. The damage of the herbicide.
(4) Promptly remedy the destruction . For heavier phytotoxics, targeted remedies should be taken as soon as possible on the basis of identifying the causes of phytotoxicity. If there is no remedy for serious phytotoxicity, it is necessary to hurry to replant, replant and compensate for losses.
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