TIMES OF AGITATION AND CONCENTRATION OF NaOH TO CHARACTERIZE THE SOIL TEXTURE

Abstract

The particle size distribution is an important index to assess the physical, chemical and biological attributesof a soil with practical applications in erosion and adsorption of nutrients. Thus, the aim of the present study was to test the effects of different concentrations of NaOH and agitation time for the particle-size distributions of four soils from the western region of Santa Catarina State, Brazil. Four soils were collected, being HumicCambisol, Histosols, Red Ferralsols and Red Nitisols, by sampling “A” horizon of the Cambisol, “H” horizon of the Histosols, and “B” horizons of the Ferralsols and the Nitisols. The hydrometer method was used to evaluate the texture through the variation of the agitation time (4, 8, 12, 16, 24 and 30 hours) and variation in concentrations of the chemical dispersant (NaOH: 0.1; 0.5; 1 and 2mol L^-1) only at 16 hours of agitation. The clay content in the Cambisol was stabilized with the agitation time of 22.52h and 31,28h in
the Ferralsols. An adequate agitation time was not observed for the Histosols and the Nitisols was not influenced by the agitation times. For the concentrations of the chemical dispersant (NaOH), the clay content of the Ferralsols was stable with 1.16 mol L^-1and the Nitisols with 0.92 mol L^-1. The Cambisol and the Histosols, however, showed no stabilization of the clay content.