In the subtropical region of Brazil, the no-till system has been used with soil conservation practices required to control water erosion generated by runoff. The absence of terraces has resulted in runoff with sediments enriched with agrochemicals and organic matter, with economical and environmental impacts. The present study aimed at to evaluate, through enriching sediment index, the efficiency of the vertical mulching as a conservation tillage practice used to reduce water erosion losses under no-till system. Three field surveys were used to pair sample soil and sediment, in 106 no-till farming fields, under no-till system, in Rio Grande do Sul state. Survey I: composed by 31 farming fields with no conservation tillage practices. Survey II: composed by 43 farming fields fully terraced. Survey III: composed by 32 farming fields with vertical mulching as conservation tillage practice. Paired samples constituted treatment T₁ (soil samples of the 0 to 10 cm layer of each farming field) and T₂ (sediment samples generated by erosion in each farming field). In Survey II, the T₂ treatment was constituted by soil samples of the 0 to 10 cm layer inside of the terrace channel. In each soil sample and sediment was determined: pH, available P, exchangeable K, Ca, Mg and Al, and organic matter. The enrichment sediment indexes showed that the vertical mulching presents potential to reduce water erosion losses under no-till system, preventing risks of pollution.

Key words: enrichment index, sediment