Organic weed control - getting it right in time

Weed control is often a major problem in organic horticultural systems; a c ritical aspect of non-chemical weed control programmes is the timing of ope rations. The concept of optimum weeding periods based on crop-weed competit ion experiments is outlined. Field studies with radish demonstrate how rapi d crop development can avoid the need for weeding. The defined weeding time s for a range of temperate horticultural crops have been compiled from publ ished and unpublished sources. The incorporation of timing into an organic weed control strategy is discussed. Future developments in weed control are highlighted, with special reference to computer-aided decision support sys tems.