The physiological activity of soil-applied herbicides depends on the degree of inherent plant tolerance, the location of the herbicide in the soil and the depth of plant roots. Classification based on the mode of action takes into account differences in the physiological and biochemical action of the herbicides. After entering cracks, holes or crevices in the epicuticular waxes on the leaf surface, the herbicide moves internally along the relatively polar components of the cell wall.
Once the herbicide absorption process is complete, translocation of the herbicide to the site of action becomes the primary physiological function involved in the mode of action. Systemic herbicides (translocated herbicides) can be translocated to other parts of the plant either in the xylem or the phloem or both. The chemical can be partitioned into parts of the plant away from the site of action and therefore rendered inactive.
The degree of translocation is often related to the hydrophilic/lipophilic balance of the herbicide. The addition of a -OH group to the ring structure of the molecule is called ring hydroxylation. The persistence of herbicides in soil is expressed as the half-life or the time required to break down fifty percent of the original molecule.
Most of the herbicides fall into category III and IV, but few herbicides are classified into category II such as paraquat, 2, 4-D and anilophos.
Gas or vapours (ppm)
Many herbicides can incorporate hydrogen ions into their molecular structure, changing the charge of the herbicide molecule. Volatilization is considered one of the major routes of herbicide dispersal from the site of herbicide application. The degree of sorption to the soil matrix is influenced by the carbon content of the soil, which in turn influences the rate of volatilization from the soil.
Soil moisture content has been found to be one of the most important environmental parameters affecting herbicide volatilization rates. The use of emulsifiable concentrations (EC) results in direct application of the active ingredient to the soil, allowing sorption into the soil matrix. Microbial degradation is one of the most important methods of herbicide degradation in soil.
The speed of the photolytic reaction is directly related to the overlap of the herbicide absorption spectrum and the spectral distribution of sunlight. In addition, direct photodegradation may be important, depending on the properties of the chemical (McCall and Gavit 1986). The site of uptake of soil active herbicides is a characteristic of the herbicide and not of the plant.
The inactivation of linuron in the roots of roots, for example, prevents the translocation of the herbicides to the leaves and their site of action in the chloroplast. Alteration of the herbicide within the plant is the main reason for selectivity among most species. Diclofop-methyl itself is not toxic, but hydrolysis of the herbicide in the plant leads to the formation of the herbicide diclofop, which is toxic.
Tolerant plants such as wheat metabolize diclofop by hydroxylation of the ring structure and conjugation. Soil-active herbicides are commonly applied to the soil surface, where they can either be left undisturbed or incorporated into the soil. The band application of herbicide is primarily a cost-saving device, as it reduces the amount of herbicide in the ratio of the treated band width to the width of the crop.
Blanket or top application of herbicides is their uniform application to standing crops without regard to the location of the crop plants. However, when possible, self-selective herbicides should be used with this method to place most of the herbicide on the weeds.
Methods of treating brush and trees
All the contact herbicides and some of the translocated herbicides are only effective when applied to leaves because they are rapidly inactivated in the soil. The most common effect of surfactants is to lower the surface tension of the spray solution. A similar relationship was observed between surfactant concentration and wetting of the plant surface (Becher and Becher, 1969).
Similarly, the drying time and characteristics of the spray droplet could be significantly modified by the presence of a surfactant. Even in the case of isolated cuticles, the dissociated group in the cuticle appears to be little affected by the pH of the spray solution. At high concentrations of the herbicides, physiological changes can be induced in the uptake and transport process and thus change the subsequent penetration.
Volatilization can be reduced through incorporation of the herbicide into the soil by mechanical incorporation, irrigation or precipitation. Surfactants should be considered inactive ingredients, although they can have a pronounced effect on product performance (Figure 6). Surfactants are generally classified by the nature of the polar segment of the molecule.
Spreading of spray droplets occurs when the surface tension of the droplet is less than the surface tension of the leaf surface. Organosilicone surfactants are often compounds of a trisiloxane framework (lipophilic or hydrophobic part), with an ethylene oxide chain (hydrophilic part) attached to one of the silicon atoms. The organosilicon surfactant causes a remarkable reduction in the surface tension of the water-based spray solution and causes a significantly greater spreading of the spray droplet than would be predicted by the reduction in surface tension.
With the exception of social insects, there has been little research on the behavior of soil fauna (Christiansen 1970). Various authors cite this as the cause of their observations of the decline of soil fauna (Fox, 1964, Curry 1970). Weight of commercial material required = weight of chemical (ai) to be used Percentage expressed as a decimal (ai).
No. Herbicide common name
In this case, 1.33 kg of commercial product is added to the amount of water required for one hectare. Similarly, the amount of herbicide formulation required for a particular area can be calculated using the following formulation formula. The following herbicides have been registered for use in various crops for weed control by the Central Insecticide Board, Faridabad.
