The cohesive nature of horizons of certain soils interferes directly with plant growth, by reducing the effective soil depth, plant root volume and seedling emergence, due to the decreased availability of water and air in the soil. This paper aimed to use soil physical characteristics to describe the cohesive character and the influence of the soil landscape position on two slopesof soils developed from sediments of the Macacu Formation in Itaboraí, RJ, Brazil. The soils of both slopes were classified as Argissolo Amarelo distrocoeso típico (Ultisol) in the upper position and as Latossolo Amarelo distrocoeso típico (Oxisol) at the foot slope. The soil bulk density of the cohesive subsurface horizons reached 1.78 Mg m-3. Another evidence of the trendto show cohesive character was the great difference between soil physical propertiesofthe A horizon and the subsurface layers (BA and BW). In the soils at the foot slope position the moisture content, hydraulic conductivity, and available water content were higher. The expression of the cohesive character was stronger at the upper position of the landscape. The physical properties that best distinguished the soil samples in terms of landscape positions were bulk density and macroporosity for soils at the summits, and available water and total porosity for the foot slope. The soils at the bottom of the slope had higher water contents, which must have minimized the expression of the cohesive character. This study indicates the importance of developing more studies on different aspects of the degree of cohesion existing along a landscape, controlled primarily by water flows down the slope.
soil toposequence; soil porosity; hydraulic conductivity; soil moisture; soil bulk density
