A study was conducted to evaluate the effects of crop succession and rotation on the crop yields and physical properties of an oxisol (clayey Haplortox) under no-tillage system, in Rio Grande do Sul State, Brazil. The treatments included four cropping sequences, used from 1998 to 2001: (1) succession wheat/soyabean; (2) rotation corn/oat/corn + Cajanus cajan/wheat/soyabean/wheat; (3) rotation Cajanus cajan/wheat/soyabean/wheat/soybean/oat; and (4) rotation Crotalaria juncea/wheat/soyabean/oat/corn/wheat. In October 2000 and 2001, soil samples were collected to determine the physical properties, and in all years, crop yields were measured. The oxisol under no-tillage had a high degree of compaction with the greater soil bulk density and lower macroporosity than the critical limit for clay texture. The largest limitations were observed below the layer of 0-0.03 m, because in the uppermost layer, soil mobilization by successive operations of fertilizer application and sowing increased soil porosity and reduced soil density. Thus, greater volume of pores was observed between soil saturation and field capacity, responsible for soil aeration, and between field capacity and wilting point, responsible for storage of plant available water. The use of cover crops once every three years was not efficient to reduce soil compaction. The yield of the subsequent crops was positively influenced in the rotation with Crotalaria juncea, while the other cropping systems did not differ from crop succession.
