Book of Abstracts
11th IFOAM Scientific Conference
11-15 August 1996, Copenhagen, Denmark
Elm Farm Research Centre, Newbury, RG20 0HR, UK.
Mechanical methods of weed control available to the organic farmer include ploughing, false seed bed techniques, and in-crop cultivation with both inter-row and harrow equipment. The effect of timing and frequency of use of spring-tined harrow and inter-row hoe weeders on weed growth and crop yield was assessed in replicated experiments in organic winter wheat on three (spring-tined harrow) and two (inter-row hoe) organic farms.
In one experiment tined weeding resulted in a non-significant increase in winter wheat yield following weeding in November, which coincided with a reduction in density of poppy (Papaver rhoeas). Weeding in spring did not increase grain yield and but did reduce the density of chickweed (Stellariamedia). In the other two experiments the tined weeder reduced wheat yield, and many treatments failed to reduce the density of the weeds sufficiently to reduce weed dry matter at harvest, whilst some actually increased weed dry matter at harvest.
The use of the inter-row hoe reduced weed dry matter at harvest in both experiments, but failed to increase the wheat yield. This may have been due to low weed density at one site, whilst poor soil structure contributed to in effective operation at the other site.
The effectiveness of mechanical weeding depends upon the species and growth stage of the weeds present; the growth stage of the crop; and the soil physical condition at the time of weeding (which affects the ability of the tines or hoe blades to disturb the soil). Improvement of mechanical weed control methods depends on more effective and selective equipment and on the development of the ability to predict the optimum time for weed control.