Corn "How can we use corn herbicides without hurting seedlings" and "What should we do in the face of repeated cropping"?

Too many weeds in the field not only affect the growth of maize seedlings, but also compete for nutrients with maize seedlings, making seedlings grow poorly and affecting yields
.
Most people use herbicides to kill weeds in the field, but improper use of herbicides will not only not have the effect of weeding, but also affect the growth of corn seedlings
.
How to use herbicides to kill the weeds without damaging the seedlings? The herbicides should be used as early as possible.
It is best to use the herbicides after sowing and before the weeds emerge
.
If the weeds emerge and have exceeded the 3-leaf stage, the efficacy will be reduced
.
If you are using corn post-emergence weeding drugs, the best period of application is the 3-5 leaf stage of corn and the 1-3 leaf stage of weeds
.
Properly grasp the weeding time
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Ensuring the moisture of the soil for pre-emergence application The temperature and humidity of the soil are the key factors to ensure the efficacy of the medicine
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Use the medicine after it rains before the emergence of the seedlings to ensure that the medicine can quickly reach the position where the weeds can absorb it
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The soil is relatively moist, and the actually sprayed medicinal solution can easily form a medicinal film on the surface of the soil.
Once the weeds germinate and emerge from the soil, they will contact and absorb the medicinal solution and eventually die
.
The soil is dry, so the water in the liquid medicine is easy to volatilize, and the effective components of the liquid medicine cannot be guaranteed to diffuse into a medicine film, which seriously affects the effect of weeding
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The amount of the herbicide should be selected reasonably and reasonably, and the appropriate amount should be ensured.
Too much or too little is not allowed
.
Too much will have a great negative effect on corn seedlings, and too little will not have the effect of weeding.
Strictly use the dosage in accordance with the instructions for use
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Pre-emergence soil treatment type agent: 150-250 g per mu of land
.
Corn post-emergence weeding type agent: 80-150 g per mu of land .
When spraying drugs, you must pay attention to the skill level and choose the appropriate herbicide.
Follow the instructions and use the amount of the drug.
Shake the drug evenly.
Spray evenly.
Choose the afternoon spray when there is no wind and the weather is clear.
--Spray as close to the ground as possible to avoid spraying on corn leaves
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Excessive application amount, incorrect application method during application period, or high temperature, high humidity or arid environment will cause the occurrence of phytotoxicity
.
In fact, many phytotoxicity can be recovered on their own or spray some growth-promoting regulators or liquid fertilizers to promote recovery, but there are also many people who cannot eliminate the phytotoxicity of herbicides and cannot be rescued in time
.
The editor sorts out the phytotoxicity symptoms of several herbicides commonly used in corn fields for your reference
.
At the same time, the causes of herbicide phytotoxicity are eliminated, which can be prevented in advance, reducing the probability of phytotoxicity
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Nicosulfuron Nicosulfuron is most prone to phytosulfuron in the use of large amounts or heavy spray core leaves plus high temperature and dry weather
.
After being injured, the corn heart leaves first turn yellow, and then spread to the entire leaf and other leaves; the growth of corn will be inhibited, the plant will be dwarfed, and some clumping and secondary stems may be produced.
The milder can recover within a week, and the severer will severely inhibit the growth.
It is difficult to recover
.
Pictured: Typical phytotoxicity symptoms of nicosulfuron applied during the growth period▲ Atrazine is used in large amounts or is prone to phytotoxicity in high temperature weather
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The top of the leaves is chlorosis, yellow or light green, and slow growth.
Generally, the phytotoxicity is not serious, and it can be recovered in 7-10 days
.
Pictured: Improper application of atrazine during the growth period of corn causes phytotoxicity ▲ Mesotrione Mesotrione has a slightly better control effect on large grasses because of its high safety.
It is favored by some farmers because of its high safety.
It is possible to spray the whole field to reduce the safety awareness of herbicides.
However, the use of large doses and high temperature weather will still cause phytotoxicity
.
The main manifestation is that corn leaf bleaching (fading but not drying in the early stage, which is different from paraquat phytotoxicity) affects photosynthesis, and has obvious inhibitory effect on corn growth, and the greater the dosage, the more serious the phytotoxicity
.
Pictured: Symptoms of mesotrione spraying in corn fields ▲ The herbicide dimethyl tetrachloride has a good control effect on corn field sedge and larger broad-leaved weeds, and it is often compounded with nicosulfuron Used, there are certain sales in the market, this kind of herbicides are hormone-type herbicides, they mainly induce crop distortion, roots, stems, leaves, flowers and ears have obvious deformation phenomenon
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When the corn is sprayed on a hot day or when the amount of use is too large, the corn leaves are curled, the leaves are dark green, the heart leaves are horsewhip or onion-like, the stems become flat and fragile, easy to break, and the ground produces short and thick deformed supporting roots, and the tap root is short.
, Fertility is inhibited; it is prone to lodging in rainy and humid weather.
The later stage mainly affects the developing aerial roots, and the root system shrinks, which affects the absorption of corn's normal nutrients and also has a certain impact on the ears of corn
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Pictured: Symptoms of dimethyltetrachloride phytotoxicity in corn fields ▲ In summary, the phytotoxicity of the herbicides mentioned above is mainly caused by the dosage and weather, so the application should be based on the weeds in the ground
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1.
Do not increase the dosage at will; 2.
Secondly, avoid high temperature application, preferably when the sun sets in the afternoon when the temperature is relatively cool; 3.
When there is not much land, try to direct spray to avoid the core leaves; 4.
If the weather is too dry It is best to water all over, create a field microclimate environment, and then spray; 5.
You can choose high-safety herbicides, such as the popular safe nicotinic pyridine, or add safener spray; 6.
The need for phytotoxicity has occurred Rescue in time.
If the herbicide is too large and cause phytotoxicity, it should be sprayed with clean water in time to remove the residual liquid from the corn leaf surface, reduce the concentration of the herbicide in the corn body, and reduce the phytotoxicity; 7.
When the phytotoxicity is relatively light, it will affect the leaves.
For corn that is yellow and dry, but with normal heart leaves, spray some foliar fertilizers or regulators to alleviate the phytotoxicity, such as brassinolide, strengthen the management of corn fertilizer and water in the later stage, and remediate water and fertilizer in time, so as not to cause large-scale losses; 8 .
Found that there are corn cob leaves twisted together, cut open by hand or a hard object
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Precautions for spraying: 1.
Avoid the high temperature and strong light at noon.
Spray the herbicide when the temperature is high around noon and the light is strong.
First, the medicament is volatile and wastes serious! Second, the stomata of weeds are closed at this time, the absorption of liquid medicine is limited, the spray is not easy to hit the target, and the control effect is not ideal
.
2.
Choose a cloudy day without rain.
If it is sunny, spray the medicine at 8-10 am after sunrise or after 5 pm without dew before sunset
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When the wind is strong, the spraying should be stopped, otherwise it will cause uneven spraying and easy to cause phytotoxicity
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3.
Pay attention to body protection taboo.
The liquid medicine in the barrel is too full.
Some farmers like to fill the liquid medicine in the sprayer barrel very full when spraying. .
This is not only detrimental to spraying, but more importantly, if the sprayer cover is not tightly closed, the sprayer will splash and get on the body when the sprayer is walking in the field, which can easily cause poisoning in the hot season
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The correct method is that the upper liquid level of the liquid medicine in the barrel should be below the graduation line when dispensing the medicine, and the closure ring of the lid must be intact to ensure that the lid is tightly closed
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4.
It is contraindicated to increase the concentration of the liquid medicine at will.
Some farmers often increase the amount of herbicide, reduce the dilution ratio of the herbicide, and increase the herbicide concentration at will in order to improve the work efficiency or to enhance the control effect, even in the high summer season
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As the water volatilizes quickly under the scorching sun and high temperature, if the sprayed pesticide concentration is too high, it is easy to cause damage to the plant leaves
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5, contraindications and organophosphorus pesticides mix as dichlorvos, omethoate, chlorpyrifos, phoxim, malathion
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It is easy to cause phytotoxicity when mixed with herbicides in high temperature weather
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Source: Encyclopedia of Agriculture, Countryside and Farmer "What should we do in the face of continuous cropping" (Puchuang Agricultural Technology Exchange Platform) The protected land has accumulated due to long-term continuous cropping, causing accumulation of germs and eggs; excessive use of physiological acid fertilizers, excessive use of nitrogen fertilizers, and organic fertilizers It is too small and the soil has poor buffering properties, which makes the soil acidified.
In severe cases, crops will appear dead seedlings and growth points necrosis; the single and excessive fertilization will cause the soil salinity to rise and increase the salt damage
.
Therefore, the improvement of soil acidification and salinization in protected areas is particularly important
.
Protected soil should be selected with a soil layer thickness of 50-70 cm, organic matter content 2.
5-3.
5%, total nitrogen 0.
1-0.
15%, total phosphorus 0.
1-0.
25%, loose texture, good arable loam, and its porosity is large.
Good air permeability, the soil solution is neutral or slightly acidic, and has a strong buffering capacity.
It is not easy to appear fertilizer damage after fertilization, and it will not appear fertilizer damage and defertilization if it is not applied in time
.
1.
Soil acidification continuous crop protection land.
Due to the long-term application of physiological acid fertilizers and excessive application of nitrogen fertilizers, a large amount of nitrate nitrogen accumulates.
At the same time, the application amount of farm manure is too small, and the soil buffer is poor, so the soil is acidified.
In severe cases, crops will die.
, Growth point necrosis and other phenomena
.
The protected area has high soil temperature throughout the year, coupled with high humidity, and vigorous soil microbial activities have accelerated the conversion of soil nutrients and the decomposition of organic matter.
At the same time, due to unreasonable excessive fertilization throughout the year and lack of rainwater leaching, residues remain in the soil.
Various fertilizer salts in the soil accumulate to the plow layer with the irrigation water, forming secondary salinization
.
It is determined that when the soil salt concentration reaches 0.
3%-0.
5%, because it is higher than the plant cell solution concentration, it is difficult for the crop to absorb water and is prone to withering.
When the alkali hydrolyzable nitrogen, available phosphorus, and available potassium in the soil exceed the salt damage threshold When the concentration is high, the crop is prone to salt poisoning, which affects the roots of the plant to absorb water and fertilizer and even grow, resulting in overall wilting and dead seedlings
.
3.
Nitrogen dioxide and excess ammonia poisoning.
Farmers tend to apply nitrogen fertilizers when fertilizing in protected areas.
They think that nitrogen fertilizers have a quick effect and are easy to increase production, but they ignore that when there are too many nitrogen fertilizers, ammonium nitrogen is easily converted into nitrite nitrogen dioxide.
When the concentration of nitrogen dioxide reaches 2×10-6, it will poison the leaves of vegetables and produce white spots and yellow spots on the back of the leaves.
At the same time, there is too much free ammonia in the plant, and the plant immunity will be greatly reduced.
Blight, anthracnose, downy mildew, virus disease and other pests are prone to serious occurrence
.
4.
Soil nutrient imbalance.
Soil nutrient imbalance causes physiological deficiency barriers.
In continuous cropping, the same or similar fertilizers are continuously applied in large quantities, and specific crops have a certain selectivity in the absorption of nutrients, which will cause excessive shortage of certain elements.
And some elements have accumulated too much surplus, resulting in an imbalance of soil nutrients
.
The specific reasons for soil nutrient imbalance are as follows: 1.
More chemical fertilizers and less farmyard manure affect the natural quality of vegetables
.
2.
Too much nitrogen fertilizer and lack of potassium fertilizer will reduce the utilization rate of nitrogen fertilizer and increase fertilizer damage
.
3.
There are many macroelement fertilizers, which tend to reduce the effectiveness of medium and trace element fertilizers.
For example, too much nitrogen and phosphorus will reduce the effectiveness of nutrients such as calcium, boron, and zinc.
Continuous cropping is prone to dry Chinese cabbage caused by calcium deficiency.
Heartburn, umbilical rot of tomatoes and sweet peppers, etc.
Boron deficiency can cause radish and celery stem cracking, and the leaves are twisted and thickened and become brittle. .
5.
The soil microbial population is alienated, producing some biologically toxic substances that are the same as the root exudates of the same crop, causing some soil microorganisms to multiply and some soil microorganisms are inhibited, so that the microbial population will be alienated, which is not conducive to soil maturation and fertilizer The decomposition and transformation of nutrients can easily cause the deterioration of soil properties
.
In addition, changes in the microbial population in continuous cropping soil can accumulate diseased bodies year by year, and the number of soil pathogenic fungi will increase rapidly, and antagonistic bacteria and actinomycetes will be inhibited, which can cause soil-borne diseases such as fusarium wilt, bacterial wilt and root-knot nematodes.
Serious occurrence
.
6.
Control measures 1.
Application of straw bioreactor technology.
Straw is transformed into carbon dioxide required for plant growth under the action of microbial fermentation bacteria, etc.
, heat resistant to disease spores, enzymes, organic and inorganic nutrients, in the reactor planting layer, 25 cm The soil porosity of the cultivated layer is more than doubled, the beneficial microbial populations increase, and the water, fertilizer, gas, and heat are moderate, which has a permanent effect on the continuous cropping obstacles of the protected soil
.
2.
Soil disinfection (1) Water soaking: Where conditions permit, the crops can be used in the fallow season to soak the soil for about 20 days, which can significantly eliminate harmful bacteria and pests in the soil
.
(2) High temperature and stuffy shed technology in summer: In the morning of the sunny day in the hot season, the greenhouse is sprayed with insecticide and fungicide on the ground, and 100 ml of alcohol is added for every 30 kilograms of liquid medicine, and covered with plastic film in time.
Above 70℃, to kill some germs and eggs in the shed and soil
.
The dull shed time is generally controlled within 15-20 days, and 1 month is better
.
(3) Damp heat sterilization method: It can effectively kill various nematodes, harmful fungi and bacteria in the soil, and solve the problem of repeated cropping and dead seedlings
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Specific method: After pulling the seedlings of vegetables in winter and spring, 70 kg of quicklime powder, 10-15 cubic meters of raw chicken manure or other livestock manure, 3,000 kg of plant stalks, and 8 kg of microbial fermentation strains are sprinkled per acre
.
Rotate the pear again to mix the orange stalks, livestock and poultry manure, and bacteria evenly, then turn the soil 35 cm deep, pour water thoroughly, cover with mulch film, buckle the shed film, keep it for about a month, remove the mulch, plow the land again , It can kill germs and activate the soil after drying on bare ground for a week
.
This method has obvious control effects on soil-borne diseases caused by repeated cropping, and among them, grafted cucumber root rot and root-knot nematode disease, which are the most serious damage to cucumbers, have the best control effect
.
It also has obvious effects on the bacterial rot disease of the graft interface
.
3.
Increase the use of decomposed farm manure for many years of continuous cropping in greenhouses.
The clay soil with poor cultivability should be improved by pressing sand, and the sandy soil with low water and fertilizer retention performance should be mixed with clay for improvement
.
The fertilization of vegetable fields should be based on farmyard manure, which has comprehensive nutrients and has a strong buffering effect on soil pH, salinity, and permeability
.
Farmyard fertilizers commonly used in protected areas mainly include decomposed human dung, livestock and poultry manure, soil miscellaneous manure, and plant ash.
Various materials must be fully decomposed before they are applied
.
In addition, the organic activated nutrient Jiamei dividend can also be directly applied.
The principle that it can relieve or solve soil salinization is that on the one hand, the dividend is dissolved in water to form an organic-inorganic clay composite colloid.
Generally, the water absorption capacity of the soil clay is 50.
%-60%, while the composite colloid can be as high as 400%-600%, and the ability to adsorb ions is 2-3 times that of soil clay particles.
After the dividend is dissolved in water, it can adsorb free sodium and magnesium ions in the soil and form in the soil.
Stabilize the chelated aggregate structure, break the compaction, improve the soil, adjust the moisture and heat balance, make the soil loose and breathable, keep warm, and have the properties of water and fertilizer retention; on the other hand, it promotes the root system to extend widely to form a healthy and large A new complex absorption system; it also contains biological stress resistance factors such as ABP, PAM, phytoalexin, etc.
, which creates a good rhizosphere micro-ecological environment for plants, which can more effectively alleviate various replanting diseases
.
4.
Balanced fertilization.
Unreasonable application of chemical fertilizers, especially excessive application of nitrogen fertilizers, is the leading factor in soil obstacles in continuous cropping protected areas
.
Therefore, balanced fertilization is a key measure for protected field production, high yield, high quality, and high efficiency.
It is recommended to increase the application of organic activated nutrition, high potassium and high calcium package fertilizer Jiamei Jinli, Hailibao, and profit to regulate the soil, activate nutrients, and promote nutrient absorption and Transformation, strong seedlings and many fruits, high yield
.
5.
Reasonable intercropping, rotation and stubble use the differences in nutrient requirements and disease and insect resistance of different vegetable crops.
Reasonable rotation and intercropping, mixing, and intercropping can also reduce the occurrence of soil barriers and soil-borne diseases. .
(2) Intercropping: intercropping eggplant with green onions and chives to prevent ants; intercropping peppers and cucumbers in greenhouses to effectively prevent pepper anthracnose and cucumber downy mildew; intercropping Chinese cabbage and other cruciferous vegetables with lettuce to repel cabbage caterpillars; intercropping with garlic and rape Avoid vegetable aphid; garlic and cotton intercropping to repel cotton aphid; tomato and cabbage intercropping to avoid cabbage pests; onion and peas intercropping to prevent pea black spot; leek and Chinese cabbage to prevent soft rot of Chinese cabbage
.
6.
Soil washing and salt deep plowing For vegetable plots with a certain salt content of more than 0.
2% in the soil, flood irrigation can be carried out to wash the salt
.
When the salt damage is serious, you can stop planting vegetables for one year and plant a crop of salt-absorbing plants for biological desalination
.
Deep turning the soil 35-40 cm can increase the soil cultivation layer, break the soil compaction, improve soil permeability, improve soil physical and chemical properties, and eliminate soil continuous cropping obstacles
.
Combined with deep turning and soil preparation, chemical disinfection with Mianlong granules can also effectively reduce the occurrence of continuous cropping obstacles
.
7.
It is a common phenomenon to adjust the pH value of the soil.
Continuous cropping of vegetables causes soil acidification.
The pH value of the soil in the shed should be tested once a year.
When the pH is ≤5.
5, 50-100 kg of lime can be applied per acre when turning the ground.
Mix thoroughly, which will not only increase the pH value, but also have a certain killing effect on soil pathogens
.
8.
The use of resistant varieties and grafting techniques to select disease-resistant, high-quality, and high-yield varieties is a prerequisite for improving disease resistance and the most cost-effective and effective measure to prevent and control soil-borne diseases
.
The grafting technology is used to prevent and control root diseases, and varieties with high resistance to root knot nematodes and strong roots are selected as grafting rootstocks, such as black seed pumpkin grafting cucumbers, etc.
, which have many years of successful experience
.
Especially in disease epidemic years and regions, combining with other prevention and control measures is an important guarantee for stable and high yields of vegetables
.
9.
Chemical control can be based on the type of disease, select the corresponding chemical, disinfect the soil before sowing, spray and irrigate the root during the growth period
.
In addition to irrigating the roots, you can also remove the nozzle of the sprayer and directly use the spray rod to irrigate the roots. .
In the growth period, the agents that can be used to prevent and control root rot are: hymexazol, fludioxonil, likugen, DT, etc.
; agents that can be used to prevent fusarium wilt and verticillium wilt: synergistic carbendazim and metalaxyl , DT, colaminones water, etc.
; agents for the prevention and control of epidemic diseases: metalaxyl mancozeb, chlorothalonil, etc.
; agents for the prevention and treatment of bacterial wilt: norfloxacin, agricultural streptomycin sulfate, saccharide, chlorobromide isocyanurate, DT and so on
.