Properties of compacted fine-textured soils as affected by crop rotation and reduced tillage

The effects of crop rotation and reduced tillage on physical properties of compacted soil were investigated in held experiments on two fine-textured soils. Field experiments were established in 1990 when trial plots were compacted to 0.45-0.50 m depth by three passes with high axle load traffic. Control plots were not loaded. Both compacted (CO) and control (NC) plots were then ploughed to 0.18-0.23 m depth. In 1991, four cultivation treatments were commenced: RTSC, reduced tillage including autumn stubble cultivation, spring cereals; RTCR same as RTSC but with crop rotation; CTSC, conventional tillage including autumn ploughing, spring cereals; CTCR same as CTSC but with crop rotation. Several soil physical properties were measured in autumn 1994 (silt, Eutric Cambisol) and 1995 (clay loam, Vertic Cambisol), and structure of the soils was visually examined to 0.5 m depth. Soil penetrometer resistance was greater in CO than NC plots in the 0.35-0.49 m layer of the clay loam and the 0.25-0.35 m layer of the silt soil. The subsoil structure was also more massive and homogeneous in CO than in NC plots. The number of cylindrical pores (>2 mm diameter, NE) was nevertheless greater in CO than in NC plots at 0.55 m depth. At the bottom of the topsoil layer, NE was clearly less in conventional tillage (ploughed) than in reduced tillage (stubble cultivated) plots. Likewise, in the layer of 0.15 m below the topsoil, saturated hydraulic conductivity (K-sat) and at 0.55 m depth NE were greater in reduced tillage plots. The K-sat and macroporosity (diameter >250 mu m) were increased in the upper part of the subsoil by crop rotation with perennial crops. More detailed information about the size distribution of macroporosity and cylindrical pores and the continuity of the pores is required to evaluate the effects of different cultivation methods on the recovery of compacted soil structure. (C) 1998 Elsevier Science B.V. All rights reserved.