The influence of crop density and sowing delay on weed germination in winter wheat

Due to changes in agronomic practices and cropping systems such as the development of reduced soil tillage systems, monocropping; changing climate conditions that result in longer warmer periods in autumn and due to other factors such as herbicide resistance approaches for integrated weed management are needed. Crop competitiveness could be one of several measures of cultural weed control, which is an important factor in integrated weed control. Delayed sowing dates or higher crop seed rates could be an integrated tool for weed management, because higher crop plant densities generally are more competitive with weeds. Two field trials were conducted to investigate the influence of winter wheat plant density and delay of sowing date at the Institute of Agriculture, LRCAF in conventional soil tillage system over the period of 2014 –-2016. Winter wheat var. ‘Ada’ was drilled at three different seeding rates (2, 4 and 8 million germinal seeds per hectare) at the regional recommended sowing date, three weeks later and six weeks later. Main weeds in winter wheat crops were annual dicotyledonous, common for the winter cereals stands in Lithuania such as Thlaspi arvense, Viola arvensis, Galium aparine and Lamium purpureum. Furthermore, volunteer oilseed rape and the annual monocotyledonous weed Apera spica-venti were presented in the field. Admittedly, meteorological conditions were favourable for cereals vegetation during the autumn. In plots with the highest seeding rate weed biomass was significantly lower, however lodging problem, especially in early seeded plots occurred. The weed biomass in plots drilled at the end of September was significantly lower compared to early drilled plots. The lowest weed mass was recorded in plots with the latest sowing date, however a significant decrease in grain yield was recorded in these plots.