An experiment, 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 pH in water, exchangeable Al and Ca + Mg, organic matter, extractable P, and exchangeable K were evaluated, using a completely randomized design, in 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 the 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. Differences observed among soil tillage treatments in relation to pH and exchangeable Al and Ca + Mg were due to the depth of soil turnover and lime incorporation. The distribution of exchangeable K and extractable P in the soil profile varied with the depth of soil turnover. Tillage systems that cause less soil turnover improved P concentration at upper soil surface layer. Crop rotations including soybean showed higher pH and exchangeable Ca + Mg and lower exchangeable Al than other rotations. Soil tillage systems and rotations maintained soil organic matter at initial level after 12 cultivations.
moldboard plough; harrow; no-tillage