This study, covering 12 cultivations, was carried out at Embrapa Rice & Beans Research Center, Santo Antônio de Goiás, Goiás, Brazil, in an Oxisol, under center pivot, for six consecutive years. The effects of four soil tillage systems and six crop rotations on bulk density and soil porosity were evaluated. The experiment was conducted in a completely randomized design, using a splitplot arrangement, with three replications. The tillage treatments were: moldboard plough/harrow disc, moldboard plough, harrow disc, and no-tillage. Tillage treatments constituted the main plots and rotation treatments, the subplots. The crop rotations were: (a) upland rice-common bean, (b) corn-common bean, (c) soybean-wheat, (d) soybean-wheat-soybean-common bean-upland rice-common bean, (e) upland rice associated to calopogonium-common bean, and (f) corn-common bean-corn-common bean-upland rice-common bean. Crop rotations a, b, c, and e were annuals and d and f were of three years'duration. The soil under no-tillage at the surface layer (0-10 cm) showed the highest bulk density value and the lowest total porosity and macroporosity values. Whereas the soil under harrow treatment showed the lowest bulk density and the highest total porosity values. Under moldboard plough, the 10-20 and 20-30 cm soil layers had the lowest bulk density values and the highest total porosity and macroporosity values. On the surface layer, crop rotations composed by soybean and wheat showed the highest bulk density and microporosity values and the lowest macroporosity values while the crop rotation composed by upland rice associated to calopogonium and common bean showed the highest macroporosity value and the lowest microporosity value .
moldboard plough; harrow; no-tillage