Yield of soybean crop in function of soil compaction affected by tillage system on Oxisol of subtropical region

The increase in conservation tillage offers possibles benefits of decreasing soil compaction risk by wheeling.The objective this work was to evaluate the effect of the minimum tillage and direct drilling system after four and eight yars of continuous no-tillaging, on the soybean yield in function of the soil density and organic matter content.This trial was carried out on Oxisol, at Parana, subtropical region from Brazil.The relationship between yield of soybean and tillage system was analyzed as function of the soil density and organic carbon using linear regression model.No-tillage system four years (NT4) and minimum cultivation system in eight years of no tillage (MT8) showed greater decrease in soil density on the surface layer as a function of time, respectively, 0.22g cm-3 (1.318 -1.098) and 0.24 g cm-3 (1.248 -1.010).Adjust of response curves of soybean yield as function of soil density and organic matter describes strong positive contribution of organic carbon in soybean productivite on the NT4 system and describes no interference of soil density on this system.In both systems (NT8 and MT8), the soybean yield decreases with increasing soil density.Soil sub-surface management after continuous periods of no-tillage should be investigated. Keywords: soil management,