Heavy metal distribution under the influence of soil tillage methods in an agrosystem with edible bean plants (Phaseolus vulgaris L.)

To evaluate the effect of different soil tillage methods on heavy metal accumulation in soil and edible bean plants (Phaseolus vulgaris L.), a study was carried out in the county of Paty do Alferes, Rio de Janeiro State, Brazil, on a Red-Yellow Latosol with 30 % slope. On 22, 0 x 4,0 m Wischmeier plots, the following methods were installed: conventional tillage: downhill furrows and burning of vegetal residues (PC); tillage along contour lines: contour plowing by animal traction with strips of cropping grass every 7,0 m (PN); minimum tillage: opening of ditches for plants only, under preservation of the vegetal residues (CM). Samples of soil, plant and agrochemicals were collected for the determination of heavy metal contents. Peprosan fungicide was responsible for the highest addition of Cu to the soil system. Minimum tillage and tillage along contour lines accounted for a higher accumulation of heavy metals, probably due to smaller erosion losses. Fruits under PN and CM presented Pb concentrations above the levels allowed for fresh food, unfit for human consumption.