Weed management is reported to be a major constraint in organic agriculture. Organic growers also report a lack of information about non-chemical weed control. A series of field trials was conducted in lettuce (Lactuca sativa L.) and echinacea (Echinacea purpurea (L.) Moench) crops to evaluate a range of weed control methods commonly used in organic herb and vegetable production systems. The criteria for evaluating the methods were weed growth, crop yield and cost effectiveness.
Hand weeding, tillage and organic mulches (hay and pelletised paper) were effective to very effective at suppressing weeds. In general, good weed suppression was correlated with good crop yields; however, crop yields were reduced by tillage and paper mulch. Deducting the cost of the weed control method from the gross crop value caused a greater re-ranking of the treatment performance in lettuce than in echinacea. This is partly due to the different growing season lengths and market prices of the two test crops. The most cost effective methods for managing weeds in lettuce were tillage and hand weeding. When weed competition is low, the unweeded control treatment was also cost effective. In echinacea, hand weeding and hay mulch were consistently the most cost effective methods for managing weeds
