Herbicides are commonly used products in paddy field production. However, phytotoxicity problems often occur when using paddy field herbicides. Therefore, it is very important to understand the types, causes and remedial measures of herbicide damage in paddy fields. Farmers must also strengthen prevention and control measures against herbicide damage in paddy fields.
The safety of herbicide application is very important. Nowadays, phytotoxicity problems often occur in paddy field production. For example, the concentration of herbicides used is too high and the methods of use are inappropriate, resulting in phytotoxicity. There are varying degrees of phytotoxicity incidents every year. Through a large number of field surveys and analysis of phytotoxicity symptoms, it was found that rice phytotoxicity mostly occurs in newly reclaimed rice areas and in rice farmers who have been planting rice for a short time and have insufficient production experience. The widespread use of herbicides in production makes crop damage inevitable. Therefore, understanding the types and symptoms of crop damage and taking timely preventive and control measures are issues that cannot be ignored in the safe use of pesticides.
Generally speaking, there are mainly the following types of phytotoxicity in paddy fields.
The conversion of dry fields to paddy fields caused phytotoxicity caused by residual herbicides. After the application of chemical herbicides such as chlorsulfuron-methyl, Pusite and atrazine to soybeans, corn and other upland crops in the previous crop, they were replanted in the second year. In paddy fields, if no corresponding prevention and control measures are taken, the residual herbicides from the previous crop will cause phytotoxicity to the next crop of rice. The characteristic of this kind of phytotoxicity is that after the pesticide is applied, the crops of the current season will not suffer phytotoxicity, but the pesticide remaining in the soil will cause phytotoxicity to the more sensitive crops in the next crop. When Honda rice tillers, the basal heart leaf tissue is distorted and deformed, swollen into a goose-head shape, and the leaf sheaths are burst. The tillers are also affected; atrazine shows that the seedlings gradually wither. If rice is planted in a field converted from drought to paddy during the pesticide residue period, the above symptoms will also appear.
Preventive measures: Use new matrix seedling technology for rice, take nursery soil from fields without residual herbicides, and pay attention to herbicide residues in the past three years in dry-to-water plots.
Bad medication habits When using chemical herbicides, the dosage and application period must be strict. Many farmers are not sure about the dosage and application period of herbicides, causing herbicides to cause phytotoxicity.
The atrazine rice contamination incident that shocked the country is an example of external inflow pollution or drift damage. This kind of exogenous pollution and non-target crop damage phenomena also appear frequently in today's production, causing trouble for correct identification and prevention.
This kind of phytotoxicity has the characteristics of rapid onset and obvious symptoms. Symptoms usually appear within a few hours to a few days. Generally, the symptoms include spots, perforations, scorching, curling, deformation and withering of crop leaves. , yellowing, chlorosis or whitening, etc.
1. The main causes of herbicide damage in the usual sense are:
1. The quality of herbicides is poor. During the production and processing of herbicides, due to lax control of certain links, excessive harmful ingredients or uneven mixing, this kind of herbicide is very likely to cause phytotoxicity when used in rice fields. For example, domestic butachlor contains impurities such as alachlor and acetochlor, which can easily cause phytotoxicity. Typical symptoms of butachlor damage are: short, twisted and deformed young roots and shoots, enlarged base, and difficulty in growth.
2． Misuse of herbicides, substandard operation, excessive dosage, and improper use period. Each herbicide has its specified use range, period, and dosage. Improper use period or excessive concentration can easily cause phytotoxicity. For example, quick-kill barnyardgrass is easy to cause phytotoxicity when applied in the seedling stage of rice. The rice seedlings do not show symptoms of phytotoxicity, but the rice seedlings show symptoms of phytotoxicity at the 7-leaf stage after being inserted into the field. Use 2-methyl-4-chloride in the bud stage, seedling stage and jointing stage of rice. It is prone to phytotoxicity.
3. Improper Mixing Due to the lack of understanding of the physical and chemical properties of herbicides, improper mixing of herbicides is also a factor that causes phytotoxicity. For example, mixing propanil and dimethoate can cause phytotoxicity in rice.
4. Improper application methods can easily cause phytotoxicity. The use of herbicides requires that the field surface be flat and a shallow water layer should be maintained for a certain period of time after application. If the water layer floods the core leaves, phytotoxicity is likely to occur. Applying pesticides using the bottle-throwing method can easily cause phytotoxicity.
5. Climatic conditions There is no scientific application of pesticides based on climate and other environmental conditions. Environmental factors such as climate and soil not only affect the efficacy of the medicine, but also affect the occurrence of phytotoxicity.
The main climatic factors that affect the occurrence of phytotoxicity include temperature, humidity, rainfall, wind and light, among which the most obvious effects are temperature and light. Low temperature can easily cause phytotoxicity, low sunlight can easily cause phytotoxicity, and soil with low organic matter can easily cause phytotoxicity.
6． The quality of soil preparation is poor. Honda's uneven soil preparation is prone to phytotoxicity, and at the same time, the weed control effect in higher areas is not good
7. Seedlings with poor quality are prone to phytotoxicity, whereas strong seedlings are less prone to phytotoxicity.
8. The volatilization and drift of fog droplets or the inflow and drift of exogenous pollutants or the inflow of exogenous pollutants can cause damage to nearby polluted sensitive crops.
2. How to correctly distinguish between rice phytotoxicity, pests and diseases, and fertilizer damage?
1. Phytotoxicity refers to various abnormal reactions caused by improper application of pesticides to rice, including abnormal physiological changes in the rice body, stunted growth, and metamorphosis of the plant or certain organs of the plant, often showing spots, burns, deformities, and chlorosis. , withering, etc., and even a series of symptoms such as death.
2． Pests and diseases refer to the damage reaction caused by the attack and infection of the rice itself by foreign organisms. Generally, symptoms include nicks and holes in the plant or some organs of the plant; symptoms such as lesions, mold layers, scabs, and bacterial concentration.
3. Fertilizer damage refers to physiological disorders that cause slow growth and development of rice, or even death, caused by improper use of fertilizers. After rice is damaged by fertilizer, not only is its growth and development inhibited, but its ability to resist adverse external environments is reduced, making it susceptible to pests and diseases, seriously affecting the yield and quality of rice.
3. Methods to remedy the phytotoxicity caused by herbicides in paddy fields
Based on the past few years of production practice and exploration, the main methods to remedy the phytotoxicity caused by herbicides in paddy fields include the following points:
1. If upland herbicides accidentally enter paddy fields, first, apply zinc fertilizer, which can promote the root system; second, spray potassium dihydrogen phosphate plus glucose on the leaves (glucose has a detoxifying effect); To cause phytotoxicity to the plants and leaves, spray large amounts of water repeatedly 3-4 times to try to wash away the medicaments on the surface of the plants. At present, most pesticides are easy to decompose and lose effectiveness when encountering alkaline substances. You can also add 0.2% alkali surface or o. 5% lime water to speed up the decomposition of the agent. At the same time, spraying clean water increases the moisture in the crop cells and dilutes the concentration of the liquid in the crop, which can also reduce crop damage.
2． If it is said that the paddy fields are damaged by herbicides, and if the damaged fields are found, the field water where the pesticides have been applied must first be drained and fresh running water poured in. After draining the field water, let it sit in the sun for 2-3 days and then re-irrigate, so that the herbicide can be exposed to light to accelerate decomposition; followed by plowing the field, lightly plowing the soil once to increase root activity, change soil permeability, and absorb the topsoil. The pesticide is dug into the deep soil to reduce the effect of the pesticide on the rice root system. Growth accelerators such as foliar fertilizer can be sprayed 2-3 days after tilling the fields to promote root growth and leaf growth and accelerate growth. For rice dwarfing diseases caused by some herbicides such as herbicides, the fields can be immediately drained and exposed in the early stage, and then intermittent irrigation can be used to reduce pesticide residues and thus reduce the degree of phytotoxicity. Rooting agents or quick-acting fertilizers can also be applied appropriately. It has a good effect on root promotion.
In addition, the inflow of external pollutants leads to soil contamination.
Although production activities can be gradually resumed after a period of pesticide degradation, a small amount of pesticides still remain in the soil. In order to speed up the recovery of production and reduce the harm of residual pesticides in rice fields, for similar problems, deep plowing should first be promoted as agronomic measures. Plow deeply for more than 20cm so that the residual chemicals can be leached to the bottom layer of the soil with water. Irrigate with water for 2-3 times, then rinse the field with large water, rake the ground with a hand tractor, and re-establish the bottom layer of the plow to reduce the amount of chemicals that will rise with water. Then transplant the rice seedlings; secondly, apply more agricultural fertilizer, because agricultural fertilizer is full of nutrients and powerful, which is conducive to microbial activity to decompose residual chemicals; thirdly, it is necessary to apply fertilizer in a formula, apply fertilizer in stages, increase the frequency of topdressing appropriately, insist on eating less and more meals, and apply more potassium fertilizer and zinc fertilizer; switch to new water sources such as underground deep well water to reduce pollution; fourth, it is advocated to use upland soil and seedling strengthening agent to prepare nutrient soil, sparsely sow dry seedlings (180g-200g/_), and isolate seedlings (200g/_) -250 g Liang/_) to grow strong seedlings and transplant large seedlings to enhance resistance; fifth, apply "Medina" soil activator to activate soil microorganisms, promote microorganisms to decompose residual chemicals, and reduce the amount of chemical residues in rice fields. Or spray the natural endogenous plant growth enhancer "Bihu" to alleviate rice phytotoxicity.