First, photolysis
Herbicides applied to plants and soil surfaces undergo photochemical decomposition under sunlight. This photolysis is caused by ultraviolet light. The rate of photolysis depends on the type, variety and molecular structure of the herbicide. The intensity of ultraviolet light, the ability of herbicide molecules to absorb light, and temperature are all factors that affect photolysis.
Most herbicide solutions can perform photolysis, which absorbs spectra from 220 to 400 nm. The photolysis rates of different types of herbicides vary widely. Dinitroaniline herbicides, especially trifluralin, are most easily photolyzed. Other types of herbicides have a slightly slower photolysis rate. To prevent photolysis, the agent should be mixed in the soil after spraying.
Second, volatilization
Volatilization is one of the important ways for herbicides, especially soil treatment herbicides, to disappear. The volatility is closely related to the physical properties of the compound and the saturated vapor pressure. It is also restricted by environmental factors. The herbicide with high saturated vapor pressure is volatile. Strong; dinitroaniline herbicides belong to the class of higher saturated vapor pressure, followed by thiourethane herbicides. These herbicides will quickly evaporate and lose their activity when sprayed on the soil surface. Volatile gases are more likely to damage sensitive crops.
Among the environmental factors, temperature and soil moisture have the greatest influence on the volatilization of herbicides: the temperature rises, the saturated vapor pressure increases, and the volatility is stronger; the soil moisture is large, which is beneficial to desorption and makes the herbicide easy to release in the soil solution. It is in a free state, so it is easy to vaporize and volatilize.
Third, soil adsorption
Adsorption is closely related to the biological activity of the herbicide and its residual and persistence period in the soil. Herbicides are mainly adsorbed by soil colloids in the soil, including physical adsorption and chemical adsorption. The adsorption of herbicides on soil depends on the molecular structure of the herbicide on the one hand, and on the organic matter and clay content of the soil on the other hand, and many types of herbicides such as urea, tricus triphenylbenzene and thioamino acid esters in the soil. It is easy to be adsorbed, while sulfonylureas and imidazolinone herbicides are not easily adsorbed; soil organic matter and soil with high clay content have strong adsorption to herbicides. In the use of soil treatment herbicides, the adsorption capacity of the soil colloid to the herbicide should be considered to be saturated. Therefore, the dosage per unit area should be appropriately increased or decreased with the soil organic matter and clay content, and irrigation can also be carried out to promote the herbicide. Desorption to enhance the herbicide effect.
Four, leaching
Leaching is the distribution of herbicides in the soil along the soil in the soil profile. The leaching of herbicides in the soil is determined by its characteristics and water solubility, soil structure, organic matter content, pH value, permeability and water flow. The water-soluble varieties are easy to be leached, and the salts of the compounds are more leaching than the esters; the soils are different, resulting in a large difference in surface area, and the soils with high clay and organic matter have strong adsorption to herbicides, making them difficult. Leaching; on the contrary, sandy soil and sandy loam have strong soil permeability and poor adsorption, so it is beneficial for leaching. The pH value of soil mainly affects the leaching of herbicides by affecting the chemical reaction between adsorption and herbicide and soil components. The leaching of sulfonylurea herbicides in soil increases with the increase of PH value, so it is in alkaline soil. Medium is easier to leaching than acidic soil.
The leaching herbicide easily penetrates into the lower layer of the soil profile, which not only reduces the herbicide effect, but also easily accumulates or pollutes the groundwater in the lower layer of the soil. When using the difference in selectivity, the herbicide enters the soil layer where the crop seed is located due to leaching, which is easy to cause phytotoxicity. Therefore, it should be based on the water solubility and mobility of the herbicide variety, soil characteristics and other factors affecting water movement. The best way to determine the method is to buy the method and the amount of medication per unit area to improve the herbicidal effect and prevent soil and groundwater contamination.
5. Chemical decomposition
Chemical decomposition is one of the important ways for herbicides to disappear in the soil, including oxidation, reduction, hydrolysis and formation of insoluble salts and complexes. Sulfonylurea herbicides are gradually disappeared by hydrolysis in acidic soils. When the content of high-valent metal ions such as Ca2+, Mg2+, Fe2+ in the soil is high, some herbicides can react with these ions to form insoluble salts; some herbicides form cobalt, copper, iron, magnesium and nickel in the soil. A stable complex remains in the soil.
6. Biodegradation
Biodegradation of herbicides includes soil microbial degradation and degradation in plants after absorption by plants.
Microbial degradation is the most important route for most herbicides to disappear in the soil. Fungi, bacteria and actinomycetes are involved in degradation. Under the action of microorganisms, the molecular structure of the herbicide is subjected to dehalogenation, dealkylation, hydrolysis, oxidation, cyclohydroxylation and cleavage, nitro reduction, condensation and formation of a conjugate, and the herbicide activity is lost by these reactions.
Soil moisture, temperature, pH and organic matter content significantly affect the microbial degradation of herbicides, and suitable high temperature and soil moisture promote degradation.
In different regions, it is necessary to go deeper to explain the speed and half-life of the herbicide in order to rationally use and properly arrange the crops.
Herbicides absorbed by crops and weeds disappear through a series of biological metabolisms including oxidation, reduction, hydrolysis, dehalogenation, displacement, deuteration, cyclization, isomerization, ring cleavage and binding, among which The main reflections are oxidation, reduction, hydrolysis and combination.
The Carbon Crystal Heating Panel is a new kind of heating product. The heating meaterial is made from carbon crystal which is better than carbon fiiber. The heating effect is the best among the electric heaters.
The Carbon Crystal Heater has many advantages, such as clean, and beautiful looking, and not any pollution, and no noise.
The using of this heater is for example: a 20m2 room will need about 1500 - 2000w, the choose then can be 4pcs x 400w or 4pcs x 500w.
We are the biggest manufacturer in China of heating panels. Our Laiwu factory covers more than 130000m2, more than 200 employee, and annual output is now half million pcs.
Dexiang heater has all certificate needed, such as ISO, CE, ETL, etc.
We welcome all customer all over the world come to visit us and be friend !
Warmer Appliance,Infrared Radiant Panel Heaters,Floor Infrared Heater,Bed Mattress
Shandong Dexiang Electrical Technology Co.,Ltd , https://www.infraredroomheater.com