Methods of Using Glyphosate and Experience Sharing

Pesticides Jan 1, 1970 0 views

Glyphosate, as a herbicide, is currently used in large quantities and has a good weeding effect, and is deeply welcomed by farmers. However, its use still requires a certain level of technical skill; a little carelessness can easily bring adverse effects to production, and it deserves everyone's attention.
1. Why does the efficacy of glyphosate herbicide vary when applied.
Glyphosate is an organophosphorus systemic conductive non-selective herbicide, also known as Roundup and Zhencaoning. It has a broad herbicidal spectrum and strong non-selectivity, leaves no residue in soil, and is widely used for chemical weeding in no-till fields and for directed weeding in forests and orchards. It can kill various weeds growing above ground, but is ineffective against weeds that have not yet emerged from underground buds. Glyphosate herbicide is effective against weeds of more than 40 families, including monocotyledonous and dicotyledonous, annual and perennial herbaceous weeds, as well as shrubs, algae, ferns, and so on. According to our investigation and observation, the inconsistent weeding effects of glyphosate herbicide reported by farmers come down to just a few reasons: First, different cultivation methods lead to differences in efficacy. Glyphosate herbicide is best used for no-till sowing. Spray 1-3 days before crop sowing; to seize the season for sowing, it can also be sown after spraying. Because the pre-sowing application does not bring the chemical into direct contact with crop seeds, it will not affect crop seed germination and seedling growth, so the weeding and weed-suppressing effects are both better than with tillage. No-till does not turn the weed seeds in the deeper soil layer up to the surface layer, so weed seeds find it hard to germinate; once the crop grows and closes its canopy, weed seeds and seedlings cannot sprout and grow because they cannot see sunlight. Therefore, the weeding effect of glyphosate herbicide in no-till land is better than in tilled land. Second, applying the chemical at different growth stages of weeds leads to differences in efficacy. Glyphosate is a systemic conductive herbicide, so it should be applied when the weeds are growing most vigorously. In terms of time, this is generally from March to October; in terms of botanical characteristics, the period before flowering should be the best time for application. Generally speaking, it is most suitable to spray when annual weeds are about 15 cm tall, perennial weeds are 30 cm tall, and have 6-8 leaves. If the growth stage of the weeds is not considered and spraying is done blindly after the weeds have aged, then of course the ideal control effect cannot be achieved. When weeding between crop rows, when the crop plants are relatively tall and there is a certain height difference from the weeds, the application effect is better and safer. At this time, when using glyphosate herbicide, because the lower leaves of the crop have already aged, their sensitivity to the chemical is low and their conductivity is poor, so the chemical's effect on the crop is very small. For example, weeding between corn rows, and weeding between rows of beans and melons after they have been trained onto supports, can all use this method. Third, different spray concentrations lead to differences in efficacy. According to surveys, when farmers use glyphosate, the concentration used does not have strict requirements like other pesticides, and is quite arbitrary; increasing or reducing the dosage often occurs. When determining the application concentration, the type of weeds must be considered. Generally, grass-family weeds are more sensitive to glyphosate and can be killed by a low-dose solution, while controlling broadleaf weeds requires a higher concentration; for some malignant weeds that reproduce by perennial rhizomes, a relatively high concentration is needed, and as weed leaf age increases and tolerance rises, the corresponding dosage must also increase. For example, when controlling orchard weeds, for annual grass-family weeds, 500-700 g of 10% glyphosate can be mixed with 30-40 kg of water; when controlling annual broadleaf weeds, the amount of solution should be increased to 750-1000 g; when controlling perennial malignant weeds, the dosage should reach 1250-1500 g. However, an excessive dosage will quickly kill the plant's conductive tissues, which instead is not conducive to absorption of the solution and reduces efficacy. Therefore, for economical use, a lower concentration should first be used to kill tender weeds, and then about 10 days later a corresponding concentration should be used for directed spraying of malignant weeds.
2. How to fully bring out the weeding effect of glyphosate
First, the glyphosate solution must be conducted in large amounts to the underground rhizome tissues of the weeds in order to produce a weeding effect. This requires the weeds to have relatively many leaves. If, before use, the weed area is small and photosynthesis is not strong, the nutrients stored in the roots are conducted from below upward; if the chemical is applied at this time, very little of the solution is transported downward into the roots, so it cannot produce a weeding effect. In the middle and late stages of weed growth, however, photosynthesis is strong and photosynthetic products are conducted from above downward, so applying the chemical at this time gives the best effect. Therefore, the most important point in using glyphosate is to select the best time for application. For example, to control weeds in corn fields with glyphosate, the best time to apply is when the corn seedlings are 1.5 m tall with 2-3 old residual leaves at the lower part and the weeds have reached 10 cm in height. Second, environmental conditions must be taken into account. Within the range of 24-25 degrees, as the temperature rises, the amount of glyphosate absorbed by weeds doubles, so applying the chemical at high air temperature gives a better effect than at low temperature; high relative air humidity can prolong the time the solution remains moist on the plant surface, which is conducive to conduction of the chemical; when the soil is dry and has low water content, it is not conducive to plant metabolism, and therefore not conducive to conduction of the chemical in the weeds, so efficacy also declines. Third, regarding the issue of mixing glyphosate with other herbicides, some farmers want to control multiple kinds of weeds and, in order to save labor, arbitrarily add other herbicides when using glyphosate, but the result is instead poor, because some herbicides cannot be mixed with glyphosate. For example, fast-acting herbicides such as MCPA and Gramoxone cannot be mixed with glyphosate, lest the above-ground parts of the weeds die too early and lose the ability to systemically conduct glyphosate, thereby reducing glyphosate's killing effect on underground weed rhizomes. However, adding some plant growth regulators and adjuvants to glyphosate can improve control efficacy. Fourth, choose the best application method. The application method is crucial to glyphosate's control of weeds, because within a certain concentration range, the higher the concentration, the finer the spray droplets from the sprayer, which is conducive to absorption by weeds. At the same concentration, the greater the dosage, the better the weeding effect. Adding 0.1% laundry detergent to glyphosate, or adding 30 g of diesel oil per mu, can enhance the chemical's spreading, penetration, and adhesion, and improve control efficacy.
3. Pay attention to the safety of glyphosate for crops when using it
Glyphosate is a non-selective herbicide. If used improperly, it will bring safety risks to crops. Some farmers use glyphosate to weed field ridges, and often because of glyphosate drift, it causes phytotoxicity to nearby crops; there are also farmers who, after use, do not clean the sprayer as required, and as a result, when spraying other pesticides, they spray residual glyphosate agents onto other crops and cause phytotoxicity. If phytotoxicity occurs on rice, in mild cases the leaves lose green color, causing serious growth obstruction, and in severe cases the plants may die early, or fail to head, or produce deformed heads, causing losses to rice production.
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Methods of Using Glyphosate and Experience Sharing

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