6533b856fe1ef96bd12b2318

RESEARCH PRODUCT

La nuisibilité directe des adventices en grandes cultures : quelles réponses nous apportent les essais désherbages ?

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The direct harmful effect of weeds in field crops : what do herbicide trials tell us ? Weeds are plants whose undesirable qualities (“harmfulness") outweigh their desirable qualities (trophic resources). Few studies conclude that weeds do not affect crop yield. However, it is difficult to generalize since weeds compete with crops for resources and these resources are spatially and temporally variable. This study analyzed 110 herbicide trials (untreated vs. treated plots) performed in France from 1993 to 2015 on three major grain crops: winter wheat, winter oilseed rape and sunflower. Significant yield losses were found in 92% of wheat trials (average over all trials: -2.6 t/ha), 51% of winter oilseed rape trials (average: -0.35 t/ha) and 61% of sunflower trials (average: - 0.41 t/ha). Wheat yield losses were not related to weed density in untreated plots. Yield losses in oilseed rape were related to weed density in untreated plots and herbicide efficacy. Non-significant yield losses are more due to low weed density before treatment than low herbicide efficacy.