Herbicides can be classified according to their mode of action (killing and selective), metastatic (transmissive and contact) in plants, methods of use (soil treatment and stem and leaf treatment) and chemical structural systems.
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First, the selectivity principle of herbicides turf and weeds occur at the same time, and most weeds and turfgrass belong to higher plants, so it is required that herbicides have special selectivity or use appropriate methods to obtain selectivity, so Can be safely and effectively applied to the lawn. The selectivity principle of herbicides is as follows.
1. The difference between the position difference and the time difference selectivity indicates that some herbicides are highly toxic to the lawn, and the selectivity of weeds and lawns in the soil or spatial position can be used to obtain selectivity; time difference selectivity refers to The lawn has a highly toxic herbicide, which uses the difference between the turf and weed germination and the difference in emergence and emergence.
2. The selectivity obtained by morphologically selective morphological differences between turf and weeds is called morphological selectivity. The shape of the plant leaves, the structure of the leaf surface, and the location of the growth point are directly related to the attachment and absorption of the liquid, so these differences often affect the resistance of the plant. For example, monocots and dicots are very different in morphology from each other. With herbicide sprays, dicots are more sensitive to agents than monocots.
3. Physiological selectivity The selectivity due to differences in herbicide stems or roots to herbicide absorption and transport is called physiological selectivity. Plants that are easily absorbed and transported with herbicides are often sensitive to herbicides.
4. Biochemical selectivity The selectivity due to differences in the biochemical reactions of herbicides in plants is called biochemical selectivity. This selectivity is safe in turf applications and is a true selectivity for herbicides.
5. Selective use of protective or safeners Some herbicides are less selective and can be selected with protective substances such as activated carbon or safeners (NA).
Second, the use of herbicides 1. The soil treatment method applies the herbicide to the soil, which is called soil treatment. According to different treatment periods, it can be divided into soil treatment before sowing, soil treatment before sowing, and soil treatment after seedling.
(1) Soil treatment before sowing The crops are treated with herbicides before sowing or transplanting. The specific application methods can be divided into the following two types. 1 Soil surface treatment before sowing: The herbicide is applied to the soil surface before planting. For example, flowers, turf, vegetables, etc. are applied to control weeds such as metolachlor before transplanting. 2 Mixing soil before sowing: The herbicide is applied to the soil surface before planting, and the method of uniformly mixing into the shallow soil layer is called pre-sowing mixed soil treatment.
(2) Soil treatment before sowing The soil is treated after the crop has not been planted after sowing, and the soil treatment before sowing or the soil treatment before seedling is called. Most soil treatments are applied by this method, including the replacement of important herbicides such as ureas, triazines and amides.
(3) Post-emergence soil treatment The turf growth period is treated with soil or flower transplanting and slow seedling treatment, which is called post-emergence soil treatment. For example, after the flower is transplanted, the weeds have not been unearthed or applied at the seedling stage, such as butachlor or chlorpyrifos. In order to avoid the adhesion of the agent to the plant, granules or agents are often mixed with the wet soil to avoid phytotoxicity.
2. Stem and leaf treatment The method of spraying the herbicide directly onto the stems and leaves of the growing weeds is called stem and leaf treatment. The method of stem and leaf treatment generally adopts a spray method, because the spray method makes the agent easy to adhere and penetrate into the weed tissue, and can obtain better medicine effect. According to the period of administration, it is divided into the treatment of stems and leaves before sowing and the treatment of stems and leaves during the growth period.
(1) Before the sowing, the stems and leaves are treated. Before the plants are planted or the flowers are transplanted, the weeds that have grown are sprayed with the chemicals. Herbicide is generally required to have a broad spectrum, and the agent is easily absorbed by the foliage, and falling on the soil does not affect the planting. Commonly used agents are paraquat and glyphosate. However, this method of application can only eliminate the weeds that have grown, and it is difficult to control the weeds.
(2) Stem and leaf treatment during the growth period The method of applying the herbicide to treat the stems and leaves of the weeds after the emergence of the lawn is called the stem and leaf treatment during the growth period. Herbicides are therefore required to have a high selectivity between the lawn and weeds.