PHYSICAL, CHEMICAL AND BIOLOGICAL ATTRIBUTES OF DYSTROPHIC RED OXISOL UNDER TWO CROP ROTATIONS

Abstract

The objective of this study was to evaluate the effect of two crop rotations on soil physical, chemical and biological attributes of a dystrophic red Oxisol. A randomized block design with split plot arrangement was used, with six replications. The treatments were two crop rotations, common bean/soybean + Brachiaria grass/common bean (F/S+B/F) and common bean/maize + Brachiaria grass/common bean (F/M+B/F), and a savannah area (";cerradão";) as reference, with soil samples at depths of 0-2.5 cm and 15-17.5 cm. The samples were collected in September 2004, at the common bean flowering stage. The attributes evaluated were: bulk density, total porosity, macroporosity, microporosity, average geometric diameter, average weighed diameter, aggregation greater than 2.0 mm, organic carbon, total nitrogen, microbial biomass carbon, and microbial quotient. The transition from ";cerradão"; to agricultural production, independent of crop rotation, increased soil bulk density and reduced total pore volume, macroporosity, organic carbon, total nitrogen, and microbial biomass carbon. The rotation F/S+B/F reduced soil bulk density and macroporosity, and increasing microporosity, average geometric diameter, average weighed diameter, aggregation greater than 2.0 mm, organic carbon, and total nitrogen, as related to the F/M+B/F rotation.

KEY-WORDS: Soil density; microbial biomass.