Paty do Alferes in the State of Rio de Janeiro, Brazil, is a county with agricultural tradition, whose main economical source is horticulture. Topography and rainfall regime of the region are favorable for erosion. Due to the lack of an appropriate soil management, besides excessive application of agrochemicals, physical and chemical soil degradation processes are favored, causing serious environmental impacts. With the objective to evaluate accumulated heavy metals in soil and in tomato plants (Lycopersicon esculentum Mill), raised in different soil tillage systems, a study was carried out in the county of Paty do Alferes (RJ), in the months from August to December 1999. Wischmeier plots of 22.0 x 4.0 m (with runoff and sediment collectors) were installed on a Red-Yellow Latosol with 30 % incline. Each tillage system represented a treatment: (a) conventional tillage: downhill furrows and burning of vegetal residues (PC); (b) tillage along contour lines: contour plowing by animal traction with strips of cropping grass every 7.0 m (PN); (c) minimum tillage: opening of ditches for plants only, under preservation of the vegetal residues (CM). Soil and tomato plant samples were collected for analyses of heavy metal contents, plant productivity and soil fertility. Productivity in the minimum tillage treatment was significantly lower than in the others, although this system benefited the highest soil fertility. It provided the greatest accumulation of heavy metals in the aerial part of the plants as well, and Cu and Zn contents lay above the permitted heavy metal levels in plants. The fruits of all three soil tillage systems presented Pb concentrations near the limits allowed for fresh food.
agrochemicals; contamination; soil tillage methods; conservation tillage