Competitive effects of weeds in winter linseed, Linum usitatissimum

摘要

Two experiments have studied the effects of broad-leaved weeds on winter linseed (Linum usitatissimum). The first investigated the effects of cleavers (Galium aparine) on linseed growth and yield, whilst the second looked at both cleavers, and chickweed (Stellaria media). In each experiment the plots either received an application of amidosulfuron in the spring, or no herbicide. Destructive biomass samples were taken at intervals, with measurements made on crop and weeds. In the first experiment there were no reductions in linseed yield, indicating that a cleaver population of 6.8 plants/m~2 was insufficient to compete with the crop. In the second experiment, where cleaver numbers were higher (minimum density 19 plants/m~2), all unsprayed plots hadlower yields than cleaver free plots. Application of amidosulfuron in spring prevented loss in yield from both chickweed and cleavers, so their presence over the winter had not caused irreversible reductions in crop vigour. All non-sprayed chickweed plots had lower yields than the herbicide treated and the weed free plots. The threshold density for treating chickweed appears to be less than c. 40 plants/m~2.