Varietal choice, a lever against weeds

Technical articles - Conserwa - Weeds

Field crops Field crops Genotype Variety

A competitive crop is a crop capable of reducing weed growth over time. Competing crops therefore constitute an integrated management tactic against weeds.

Traits of interest for a competitive cereal crop

Height at the end of the cycle

The crop must grow quickly and reach a high height at the end of the cycle in order to deprive the weed of light.

This parameter shows great inter-varietal variability.

Vigor at the beginning of the cycle

Vigorous crops at the beginning of the cycle seem to be more competitive; studies suggest that the high plant height at the end of the cycle and the vigor at the beginning of the cycle are the main traits influencing the competitiveness of varieties.

It has also been noted that wheat varieties vigorous at the beginning of the cycle are more tolerant to weeds.

Tillering capacity

Tillering capacity is a trait regularly highlighted to improve the competitiveness of wheat, barley, oat, triticale, buckwheat, or hemp varieties. When this ability is high, the plant has a large number of productive tillers, which results in reducing the biomass production of weeds.

Sensitivity of some weeds to smothering

This trait strongly depends on environmental conditions, leading to contrasting results depending on the studies conducted.

Leaf characteristics

The leaf habit and leaf area of the uppermost leaves of the plant from the heading stage strongly affect the level of competitiveness, especially for wheat and triticale. The most efficient genotypes seem to be characterized by a large leaf area and a semi-erect habit because they deprive the weed of light.

Root development

Varieties with a more developed root system can compete more effectively with weeds in the absorption of nutrients and water.

Degree of earliness or lateness

The degree of earliness or lateness of phenological stages of plants also seems to be a key trait in weed control, but this depends on the crops, climatic conditions... An early heading or maturity date can, for example, reduce weed biomass since the latter will develop once the cultivated plant is already well established, thus the weed will be partly deprived of light and nutrients.

Studies on varietal competitiveness of certain crops

Barley

A study conducted in Australia demonstrated that the Litmus, Compass, and Urambie varieties were more competitive because the weed biomass in their plots was 20 to 50% lower than that of other cultivars, 100 days after emergence. These varieties contributed to significant reductions in weed biomass, notably of annual grasses such as perennial ryegrass.

Another conclusion of the study identifies parameters significantly contributing to the competitiveness of barley: early crop biomass and its allelopathic activity.

Canola

Another study conducted in Australia compared four genotypes of canola (PAK85388-502, AV-OPAL, AV-GARNET, and BAROSSA). The experiments showed that genotypes PAK85388-502 and AV-OPAL were more effective in weed suppression since, at equal planting density (10 plants/m²), they reduced weed biomass by more than 80%.

The four tested genotypes had a similar aerial canopy; however, PAK85388-502 and AV-OPAL had an additional mechanism: allelopathy which may have played a role in suppressing neighboring weeds.

Wheat

A study conducted in France concluded that:

• the main traits of a competitive wheat variety are its height at maturity, its ability to cover the soil, and its leaf habit
• the most competitive wheat varieties for weed suppression are grandval and LD76B (among the following: pegassos, apache, saturnus, renan, CF99102, LD269, quebon, caphron, glasgow, sankara, grandval, and LD76B)

Sources

• Agrotransfert. Weed management levers _ Mitigation - competition by the crop for sale. [10/02/2026]. https://www.agro-transfert-rt.org/ressources/adventices/je-minforme/leviers-de-gestion-des-adventices/competition-par-la-culture-de-vente/
• Bruno Chauvel, Stéphane Cordeau, Laëtitia Lever, Rémi Perronne and Bernard Rolland. Varietal traits associated with the competition of cereal straw genotypes against weeds and avenues for their selection: a literature review. [10/02/2026]. https://agronomie.asso.fr/aes-12-1-18