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The genus Digitaria has a great ecological adaptability, being exceptionally harmful to maize crops. Appropriate management practices are necessary to reduce the negative effects of this weed and avoid maize yield losses. The effects of different cover crops straw levels, when incorporated or maintained on the soil surface, on the initial development of Digitaria spp. (crabgrass) were evaluated. The experimental design used consisted of randomized blocks, with four replications. Treatments were arranged in factorial scheme with the following factors: (A) - cover crops management (incorporated and on the soil surface), (B) - cover crops (Brassica napus, Raphanus sativus, Trifolium vesiculosum and Lolium multiflorum, and (C) - straw levels (0, 1, 2, 4, 6 and 10 t ha-1). At least 6 t ha-1 of straw were needed on the soil surface to reduce crabgrass growth. Lolium multiflorum straw provided, in general, greater reduction in the growth parameters of Digitaria spp. As the cover crops straw levels increased on the soil surface, a reduction of Digitaria spp. growth was observed. [ABSTRACT FROM AUTHOR]

The chemical substances released by plant residues left on soil surface have different behaviors from the incorporation. The aim of this study was to investigate the effects of different levels of cover crops straws, when incorporated or maintained on the soil surface, on the emergence of Digitaria spp. (crabgrass). The experimental design was randomized blocks with four replications. Treatments were arranged in a factorial scheme with the following factors: (A) - cover management (incorporated and on the soil surface), (B) - cover crops (Brassica napus, Raphanus sativus, Trifolium vesiculosum and Lolium multiflorum) and (C) - straw levels (0, 1, 2, 4, 6 and 10 t ha-1). The Digitaria spp. emergence rates were favored by the increasing levels of straw on the soil surface. With increasing levels of cover crop straws incorporated into the soil a tendency on the reduction of Digitaria spp. emergence was observed. The cover crops had little influence on reducing the emergence of Digitaria spp. [ABSTRACT FROM AUTHOR]