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Italian ryegrass (Lolium perenne spp. multiflorum Lam.) is a troublesome weed commonly found in winter cereals. Winter cover crops represent an alternative for weed suppression, reducing weed soil seed banks, and future infestations. The aim of this study was to evaluate the suppression of winter cover crops on reducing the soil seed bank and infestations of Italian ryegrass in fields managed under no‐tillage system. Field experiment was carried out during three consecutive years, in a strip‐plot design with four blocks, containing the winter cover crops. Wheat (Triticum aestivum), canola (Brassica napus), barley (Hordeum vulgare), common vetch (Vicia sativa), cereal rye (Secale cereale), feral radish (Raphanus sativus), and black oat (Avena strigosa) were sown in each strip (block) under no‐tillage system and compared with weedy fallow. Seed bank was quantified at 0.0‐ to 0.05‐ and 0.05‐ to 0.10‐m depths, whereas Italian ryegrass infestations were measured with a sample frame of 0.0625 m2. Greater suppression and lower soil seed bank were reported in plots managed with cereal rye, common vetch, black oat, and feral radish, reducing up to 80% in the first year, and up to 96% after 3 yr of continuous management in comparison to weedy fallow. Italian ryegrass infestations increased four‐ to six‐fold when managed with canola. High suppressor potential of Italian ryegrass occurred for cover crops with biomass dry accumulation greater than 8.7 tons ha−1, especially to plants with a height upper to 1 m, plant characteristics essential to reduce strongly Italian ryegrass infestations and ensure weed‐free fields throughout the time. Core Ideas: Winter cover crops reduce up to 97% the Italian ryegrass infestations and soil seed bank.Cover crops with greater biomass dry accumulation exhibit higher weed suppression.Cereal rye, black oat, feral radish, and common vetch have higher potential suppressor.Suppression with cover crops is a tool to manage herbicide resistance Italian ryegrass. [ABSTRACT FROM AUTHOR]

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]