Pre-emergence

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Pre-emergence application of a herbicide containing pendimethalin

Pre-emergence treatment (abbreviation: VA ) describes the application of plant protection products before the crop plants become visible after sowing (see field emergence ).

Pre-emergence treatments are mainly carried out with soil-acting herbicides ( pre-emergence herbicides ). Also, nematicides and fungicides are separated used pre-emergence.

Some pesticides are only suitable for pre-emergence treatments. As examples, the active ingredients are clomazone and metosulam to name.

distribution

Pre-emergence treatments are common practice for rapeseed, vegetables and potatoes. In winter cereals, the decision between pre-emergence treatment and post-emergence treatment is usually made depending on the weather.

advantages

• Crop plants survive pre-emergence treatments sometimes better than post-emergence treatments.
• The crop plants are free of weed competition from the start, and this has a major impact on the yield, especially with maize.

disadvantage

• Pre-emergence mixtures never work against the so-called "persistent weeds" (weeds that are more than two years old) such as thistles, goose thistles, couch grass, bindweed, dock and also not against volunteer potatoes and alfalfa. Successes against accrued root weeds are only possible in post-emergence.
• In dry weather, soil can trickle down potato ridges and thus destroy pre-emergence treatment.
• The user must know the weed spectrum of the target area. It is not possible to react individually to the weeds that have emerged.

requirements

technology

Mechanical track marking is required to find the spray track. Alternatively, GPS devices can be used.

Cultivation system

• A well-set seed bed is a prerequisite so that there is no erosion after application. Likewise, steep slopes are to be avoided. It should not rain for at least 2 hours after treatment.
• Moist soil is beneficial for the effect. In very dry weather, seeds often germinate from deeper, still moist soil layers. These weed plants can then not be combated by the comparatively thin spray film.
• Evenly deeply deposited seeds ensure that no seeds are hit directly.
• A fine crumbly seedbed: that doesn't mean coarse clods, but also not too fine because of the risk of silting up.

Similar procedures

Pre-sowing training

Pre-sowing incorporation (VSE) describes the mixing of the plant protection product with the soil. This process is only used occasionally. One example is the active ingredient trifluralin, which is no longer approved in Germany . The active ingredient napropamide is sometimes incorporated into special crops .

Web links

• LWK Lower Saxony on carrot cultivation
• Bavarian State Agency for Agriculture: Rapeseed herbicides - requirements for Clomazone

Individual evidence

1. ↑ LWK Luxembourg (PDF; 361 kB)
2. ↑ Fruit growing RLP on potato dams ( Memento from January 6, 2013 in the web archive archive.today )