Pre-emergence herbicide
Preemergence herbicides are a group of pesticides that before the emergence of the crop so on land that most of the somewhat earlier accrual of weeds and / or grass weeds are suppressed. Application as a pre-emergence herbicide is a widely used method of applying broad spectrum herbicides .
Preemergence herbicides (Engl. Pre-emergence treatment herbicides or short pre-emergence herbicides ) but, mostly deployed shortly after the sowing of the crop before emergence of the first crops. They are not mechanically worked into the soil. The mechanism of action is based on the fact that the germinating weeds and grass weeds usually come from the top soil layers (<50 mm). The crops, however, are sown deeper. The herbicide must be washed into the top soil layer through (light) rain or overhead irrigation.
A special form of application is the killing of an existing vegetation cover with a pre-emergence herbicide and subsequent sowing of the crop. This application is typical of the no-till tillage ( no-till systems ) and for the reseeding of grass .
Advantages and disadvantages
Compared to other chemical plant protection methods, pre-emergence herbicides have some specific advantages and disadvantages.
advantages
- Spraying as a method of application results in a high concentration of herbicides in the top soil layers. This concentration is particularly effective against shallow germinating weeds that originate from these soil layers. Herbicides that are incorporated into the soil usually do not reach these high concentrations.
- Spreading is also possible when incorporation is impossible because the soil is too wet.
- The spatial separation of the effect in the uppermost soil layers from the germination of the cultivated plants further down increases the safety of use.
- The early application in the plant cycle leads to a high reduction in competition in favor of the crop.
- The combination of sowing and herbicide application saves driving on the field.
- Pre-emergence herbicides can be used for tillage without plowing as well as for plowing.
disadvantage
- Without rain or irrigation, pre-emergence herbicides either cannot be used at all (arid areas) or their effectiveness decreases after a long period without rain.
- Too much rain, on the other hand, can wash out the herbicide too much and carry it into the depths of the sown crop. The crop is then damaged.
Active ingredient examples
- Glyphosate (e.g. Roundup )
- Flufenacet (e.g. Bacara)
- Clomazone (e.g. Centium)
- Dinitroaniline like
- Chloroacetamides like
- Dimethenamid -P
- Thiocarbamates like
- EPTC (prohibited)
See also
Web links
literature
- Thomas J. Monaco, Stephen C. Weller, Floyd M. Ashton (2002) Weed science: principles and practices. John Wiley and Sons. 671 pages, p. 75, p. 128, p. 327.