Field experiments were conducted in Passo Fundo (1984-89) and in Coxilha (1996-97), Rio Grande do Sul, and in Guarapuava (1984-90 and 1990-94), Parana, Brazil, to study the effects of winter crop residues on soyabean grown in succession, under no-till system. Winter crops were white oats knife rolled for mulching purposes, white oats, barley, rapeseed, flax, and wheat for grain yield. In these cropping systems, soyabean was grown in the summer in monoculture and in rotation with maize and pearl millet. Soyabean grown after flax and rape showed lower yield and plant height than soyabean after barley and wheat. Yields of soyabean grown in monoculture were moderate compared with yields of soyabean grown in crop rotation and soyabean grown after rape or flax. Soyabean grown after barley and wheat may be included in the different systems studied without yield losses. Volunteer white oat seeds may reduce soyabean yield and plant height.
