Winter cover crops reduce the soil seed bank and infestations of Italian ryegrass in no-tillage system.
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.