Response of different types of winter oilseed rape varieties to sowing date and to various plant density in the field

The paper presents the effect of four sowing dates: early, optimal, delayed and late sowing, and three sowing rate (40, 80 and 120 seeds per sq. m.) on the dynamics of the autumn growth and development of plants, overwintering and yield of three varieties of winter oilseed rape: open pollinated variety (Starter) and two restored hybrids (semi-dwarf - PR 45D01 and long-stem - Poznaniak). Reaction of varieties to examined factors was similar. The studied factors significantly differentiated character of hibernating plants and significantly modified morphological characters of harvested plants and yield and yield components.