Inventory and mechanisms of cultural control practices for weed management, a review

An inventory of cultural control practices is undertaken by considering each practice for its biological selectivity with respect to weeds. Descriptions of cultural practices in the literature are often brief. Some recent syntheses neglect knowledge from older publications. Disagreement concerning the delimitation of these practices is common. Clarification of the knowledge base concerning the cultural management of field flora is required for "sustainable agriculture". The selectivity most often mentioned for each practice is limited to a few examples of taxa in a geographically limited area and is rarely considered in the light of general mechanisms of action on biological cycles. The controversial distinction made by many authors between preventive and curative methods is unnecessary. Each practice listed is presented with its biological target. On the scale of a single cultural cycle, thirty practices are compared. Each target tends to have a specific biological descriptor. Most of the practice target pairs have the disadvantage of having an extreme state opposed to that of the target. Crop rotations are described as successions between non-competitive crops or practices that encourage certain weeds on the one hand and cleaning crops or practices on the other. The latter mainly target diaspores that have a lifespan inferior to the planned cleaning duration. The allelopathic after-effects show three mechanisms. In temperate climates, rotations may be complex with respect to the diversity of crop and weed phenologies. Combinations of cultural interventions must take into account the mechanisms involved, particularly because some results could cancel each other out.