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QPlant protectionHow can I control weeds with fewer herbicides?
Weeds take water, light and nutrients from the crop, and grass weeds and volunteers harbour diseases and pests. The rule is: prevention first, then agronomy, herbicide last.
1. Prevention
- Crop rotation — breaks the weed cycle. Fallow is an excellent preceding crop for wheat: weed pressure is lower and yield higher than after silage maize. Lucerne leaves a weed-free field.
- A clean field before sowing — destroy volunteers and grass weeds.
- Dense, competitive stands — dense crops suppress weeds more than sparse ones. On heavily infested fields (for example with wild oat), increase the seeding rate. Strongly tillering varieties (for example barley "Ahat") also help.
2. Agronomy and mechanical control
- Two shallow disc passes (6–8 cm) in July–August — weeds emerge and are destroyed before primary tillage.
- Spring harrowing against early weeds; inter-row cultivation and hoeing in row crops.
- Sowing date — later sowing reduces weed pressure but must be balanced against the risk to yield.
Trials show how strongly the seeding rate works:
| Measure | Effect on weeds |
|---|---|
| Wheat seeding rate +50% | Almost half as many weeds (Atanasova et al., 2011) |
| From 300 to 450 viable seeds per square metre (organic wheat) | Fewer weeds with no significant change in yield (Dover & East, 1990) |
| Up to 600 viable seeds per square metre | Much stronger control (Griepentrog et al., 2000) |
3. Herbicide — only when needed. Spray when infestation is really above the damage threshold, and on time — it is most effective at early weed stages. Rotate active substances. Under minimum tillage and direct drilling, weed pressure is higher in the first years and needs particular attention.
Material: Training Module 1, section 6 "Weed control"; Literature review (Penchev); Brochure 1.