The best measures of crop residue quality for soil protection against erosion are the percentage of soil cover and its persistence on the soil surface. These two variables, in turn, may be strongly affected by soil tillage. This study was carried out in Rio Grande do Sul State, Southern Brazil (30°06'S; 51°39'W). Crop residue mulch persistence was evaluated over a fallow period, following the harvest of a soybean crop. Three conservation tillage methods (chiseling, disking, and no-till) were used as treatments for soybean residue management. Crop residue cover was measured using both the photographic and the line-transect methods. Soybean crop residues provided little protection to the soil, with very limited persistence. The degree of correlation among the data obtained with the two methods of cover measurement was greater when mulch was uniformly spread over the surface (no-tillage), as compared to the tilled surfaces. After chiseling and disking, the photographic method produced higher counts than the line transect. Results from the two methods of measurement were similar when the soil was not tilled after harvest.
crop residues; soil cover; methods of measurement; soil tillage