Weed management in organic echinacea (Echinacea purpurea) and lettuce (Lactuca sativa) production

Weed management is a major constraint in organic production. It can be expensive and time-consuming and severe crop yield losses may be incurred when weeds are not adequately controlled. Research on organic weed management (OWM) in herb and vegetable production is increasing internationally, although in Australia very little work has been done to assess current OWM knowledge among growers, and to test the efficacy and cost effectiveness of the weed management practices used by organic growers. The effect of hand weeding, tillage, hay mulch, pelletized paper mulch (PP) and an unweeded control treatment on weed growth, crop growth and cost effectiveness were evaluated in several field trials on the Northern Tablelands of New South Wales using lettuce (Lactuca sativa L.) and echinacea (Echinacea purpurea Moench. [L.]). In echinacea, hand weeding, hay mulch and PP reduced weed growth by at least 90% compared with the control, while tillage reduced weed levels by about 50%. The more expensive weeding methods such as hand weeding and hay mulch (AU$9600 and 8900 ha-1 respectively) produced higher yields, while the cheaper methods such as tillage ($4000 ha-1) had low crop yields and were therefore 25-50% less cost effective. In lettuce, weed growth was reduced by 96% for hand weeding and PP compared with the control, 85% for hay mulch and 66% for tillage. Weed management was cost-effectively achieved using cheaper weeding methods such as tillage ($985 ha-1) compared with more expensive methods such as hand weeding and hay mulching ($4400 and 7600 ha-1 respectively). PP had lower yields and was expensive ($12,500 ha-1) and was usually not cost effective in these trials. The results highlight several important advantages and disadvantages of currently used OWM methods in the field.