SOIL PHYSICAL PROPERTIES UNDER MAIZE IN MONOCULTURE OR INTERCROPPED WITH SUMMER LEGUMES

The use of cover crops is a practice that can improve the physical quality of soils. The objective of this work was to evaluate the potential of intercropping of summer legumes with maize to improve soil physical properties. The study was conducted in the field from September 2008 to September 2009, in an Ultisol in Santa Maria, Rio Grande do Sul. The experiment was arranged in a randomized block design with five treatments and four replications. The treatments consisted of the consortia: maize + cowpea, maize + dwarf pigeonpea, maize + velvet bean, monoculture maize, and a fallow area as control. Samples were collected from the soil layers 0-5 and 5-10 cm three times per plot (at the beginning of the experiment, 30 days after leaving the residues of each crop on the soil surface, and one year after the beginning of the experiment). We measured the following properties: soil bulk density, porosity, macro- and microporosity, and aggregate stability. All crops decreased bulk density and increased macroporosity and total porosity in the 0-5 cm soil, compared to the fallow area. The consortium of maize and pigeonpea increased the mean weighted diameter of aggregates in the 0-5 cm layer, compared to the fallow treatment, but this effect was temporary, and had disappeared by the last measurement. The intercropping of maize and dwarf pigeonpea was the most promising for improvements in the soil structure.