The leaves of rice grown in rice fields often have yellowing (some whitening), which makes the farmers have no reason. There are many reasons for leaf yellowing in rice fields, and misuse, over- or excessive use of herbicides is the main reason for many years. Based on years of investigation and observation, the author introduces the yellowing phenomenon in the seedlings or growing season brought by some of the following herbicides for your reference.
Chlorsulfuron and metsulfuron
Chlorosulfuron and metsulfuron have a long residual period in the soil, especially in areas where the soil is alkaline and where the precipitation is less or the residual period is longer. The rice plantlets formed by the residues of these two herbicides usually do not divide after the transplanting of the seedlings. The whole seedlings are clustered and the plants are dwarfed. When the leaves are yellow, even the whole plant is dead, the roots are yellow and black. White roots, and then the roots of the roots are broken, like the scissors cut, the seedlings are easy to pull out from the soil. After the occurrence of phytotoxicity, the field management can be strengthened, and some foliar fertilizers can be sprayed, which has certain detoxification and long-term effects. Chlorsulfuron-methyl and metsulfuron-methyl are rapidly degraded under the condition that the soil is easily acidic. It is necessary to add organic fertilizer to the field with drug residues and increase the acidity of the soil solution, which is beneficial to reduce the amount of drug residues in the field as soon as possible and prevent it from being There is a phytotoxicity.
Misty spray of cedar and butachlor in rice seedlings
There is a herbicide called "Tian Shuang" on the market, which is a compounding agent of butachlor and oxadiazon. The drug can be applied before the sowing of the dry-broadcast rice. It can also be applied in the toxic soil method of rice seedlings. After application, the field water can not be drowned, nor can it be sprayed, otherwise it is easy to cause phytotoxicity. Direct contact with oxaloacetone in rice leaves is prone to yellowing of leaves. If the amount of medicinal application is not very large, or if the irrigation is not too devastating, the rice seedlings should generally recover quickly without special measures. Appropriate topdressing of fertilizer, shallow water irrigation, timely exposure, spraying humate foliar fertilizer can promote timely recovery of rice seedlings.
Cholesterol
The herbicide is generally used for controlling grass weeds such as rice, gold, and crabgrass, and has good effects, but the application technique is high, and it is generally required to be applied after the rice 5 leaf stage, and the dosage is strictly controlled, and the dosage is exceeded. It is easy to produce phytotoxicity to rice seedlings. In the 5~6 leaf stage, indica rice uses 6.9% of fenvalerate and water emulsion 40 ml per acre, which generally does not cause phytotoxicity to rice. However, some places use electric sprayers to add 10 kg of water per acre. The spray droplets are fine. If there is wind when spraying, it is easy to cause drifting phytotoxicity, which leads to excessive dosage in some areas, causing phytotoxicity in rice and leaves appearing to fade. Green and yellow. After this happens, spraying foliar fertilizer such as urea and potassium dihydrogen phosphate is conducive to promoting the recovery of rice.
Oxazolone
The herbicide is a contact herbicide, and the action speed is fast. If it is mixed with “Taojie†(pentaflufenazone), especially when the dosage is large, the rice is administered in an amount of 15 grams per acre during the tillering period. Slightly large, if the normal application of the drug does not generally occur, but improperly mixed with the emulsifiable concentrate, the application concentration is too large or the application of the drug at noon on a sunny day, there is a risk of phytotoxicity. That is, within 1 to 2 days after application, contact with the spray site causes injury. If the rice seedlings are small and the drug is too heavy after application, it may be further harmed by other ingredients. If the field phytotoxicity is not very heavy, the new leaves are quickly picked up and the growth is basically normal, and the fertilizer can be properly applied; if the damage is heavy, the new leaves are slowly pumped, and the new leaves are yellow, and the plant growth regulator should be sprayed . And humate foliar fertilizer, etc., to promote the rapid recovery of rice seedlings, and minimize the damage caused by phytotoxicity.
Fluroxypyroxyacetic acid
The herbicide is mainly used for controlling broad-leaved weeds such as rice, water and peanuts, and should generally be used after the 3 leaf stage of rice until before jointing. Note that the amount of use should not be too large, to avoid applying the drug in the hot and sunny weather, otherwise there will be yellowing of rice leaves. From the point of view of the occurrence of phytotoxicity in production, different rice varieties have different susceptibility to flufenoxyacetic acid, and some varieties are relatively sensitive, and it is easy to appear yellowish and reddish leaves after application. After the application of the drug, the color of the leaves of the rice appeared yellow, which generally recovered in a short period of time and had no obvious effect on the growth of the rice. If the root growth of rice is poor, spraying sodium nitrophenolate or potassium dihydrogen phosphate is beneficial to promote the rapid elimination of harmful effects caused by phytotoxicity.
Pyrazosulfuron
The herbicide is a systemic herbicide that can control annual or perennial broadleaf weeds, sedge weeds and young psyllium, and has good safety to rice. However, in recent years, it has been found that the herbicide is applied in a direct seeding rice field, posing a risk of phytotoxicity. For example, 4 to 5 days after the direct seeding of rice, 10% of pyrazosulfuron-methyl WP can be applied per acre, and symptoms of phytotoxicity will occur after 3 days. Mainly manifested as growth stagnation, dwarf yellowing of rice plants, and less white roots in rice. The reason is mainly because the application is too early, the seedlings are still weak within 7 days after the direct seeding of rice, and the application of pyrazosulfuron is easy to produce phytotoxicity; the dosage is too large, generally 10% of pyrazosulfuron-methyl WP can be used per mu. In the field of more than 20 grams of phytotoxicity, the amount of medicinal damage is less than 15 grams per acre. The resistance of different rice varieties was different. The resistance of indica and japonica rice was poor, and the resistance of indica rice was strong. When using pyrazosulfuron to control weeds in direct seeding rice fields, the rice varieties should be selected separately. The use of pyrazosulfuron-methyl is also related to the soil organic matter content. The sandy soil has low organic matter content, strong water permeability and permeability, and the use of pyrazosulfuron-methyl is poor in water and fertilizer retention, which is prone to phytotoxicity.
Heterophyllum
It has been used for many years, mainly for weed control in dryland crops, but in recent years it has been extended from soybean fields to rice, sugar cane and various vegetable crops. In the prevention of weeds in paddy fields, some use the toxic soil method to apply the dysentery. Due to improper operation, symptoms of phytotoxicity appear in many places, that is, white spots appear in the toxic soil exposed to the rice leaf, or the whole leaves turn yellow. It turns white and does not spread to other leaves. If you pay attention to the application method, try not to make the poisonous soil contact with the rice leaves, and the phytotoxicity can be completely avoided.
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