The principle of action of herbicides is relatively complex, and different principles of action need to be implemented through certain methods. On the one hand, weeds are killed and on the other hand, damage to the same field crops or even the rear crops is avoided.
The technical points for using pre-emergence herbicides include:
(1) The quality of site preparation is better. The ground is required to be crushed and there is no plant residue on the surface to ensure uniform distribution of pesticides.
(2) Select the officially registered pesticide species in the country.
(3) Select standardized pesticide application machinery. Spraying pre-emergence herbicides requires droplet diameters of 300 to 400 microns and 30 to 40 droplets per square centimeter. Artificial backpack sprayer should use fan-shaped sprayer, with 11003 fan-shaped nozzle, 50 mesh filter, spray pressure 2 atm, spray volume 225 ~ 300 liters / ha (15 ~ 20 liters per acre), a spray when spraying In a ridge, the spray shall not be shaken left or right, and the height of the sprayer and the ground, the spray pressure, and the speed of the spray shall be uniformly sprayed.
The tractor sprayer is a fan-type sprinkler with 11003 and 11004 fan-shaped nozzles and a 50-mesh filter. The spray pressure is 2 to 3 atmospheres, the spray volume is 180 to 200 liters/ha, and the spray bar is 40 to 60 cm above the ground. When the drug speed 6 ~ 8 km / h.
Most of the pre-emergence herbicides are absorbed by the weed seedlings (usually monocotyledonous weeds are absorbed by the coleoptile and dicotyledonous weeds are absorbed by the hypocotyls) and are rarely absorbed by roots. Therefore, when spraying pesticides, try to create a “weed germination circle†of 0 to 5 cm.
During the spring spraying season in our province (from late April to mid-May), we often meet with strong winds, drought, and rain. After the herbicide is applied, it is easily scratched by the wind or stays on the surface, and it cannot contact with the weed sprouts. It is difficult to exert herbicidal effects. If there is no rainfall or irrigation after spraying, mechanical measures should be taken to ensure efficacy.
Many peasant households pay attention to the requirements of pre-emergence herbicides on the waterlogging conditions, and they have a habit of waiting for rain to fight drugs. However, they have brought a series of problems: (1) When the missed young shoots are absorbed, the medicine is not in contact with the young shoots. (2) After the rain, the soil moisture goes upward. It is difficult for the herbicide to reach the 0-5 cm tillage layer to be absorbed by the weeds. In addition, after the spring rain, sunny and high-temperature weather often occurs, and the herbicide can be lost as the water evaporates. Actually, spraying before rain or before irrigation is better than applying after rain. The application of pesticides after raining should also be conducted in a timely manner with shallow soil mixing or cultivating 2 cm of soil in a timely manner to prevent loss of herbicides due to evaporation and wind blows.
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