Weed populations in winter wheat as affected by crop sequence, intensity of tillage and time of herbicide application in a cool and humid climate

Abstract

Summary There is a lack of information on the combined effects of preceding crop, reduced tillage (especially no‐tillage) and the time of herbicide application on the development of weed populations and the efficiency of weed control in winter wheat in humid temperate climates. An experiment was conducted with a crop rotation (winter wheat – oilseed rape – winter wheat – maize) on a sandy loam and a loamy silt soil in the Swiss midlands to investigate the impact of different preceding crops and pre‐ and post‐emergence control of weeds in conventional tillage (CT; mouldboard plough), minimum tillage (MT; chisel plough) and no‐tillage (NT; no soil disturbance systems). When winter wheat was grown after maize and winter wheat was grown after oilseed rape, the ranking order of weed density in treatments without herbicide application was NT < MT < CT and CT < MT < NT respectively. Analysis of variance and canonical discriminant analysis showed that Epilobium spp., Sonchus arvensis, Myosotis arvensis and volunteer crops were more abundant in NT than in MT and CT. The efficiency of post‐emergence weed control was generally better than that of pre‐emergence weed control, regardless of tillage intensity.