Soil solution charge balance for defining the speed and time of centrifugation of two Brazilian soils

Abstract

Soil solution chemistry is a powerful tool for studying many aspects of soil science. Consequently, isolation and chemical analysis of the soil solution are essential procedures in soil chemistry studies. Among several isolation techniques, centrifugation appears most promising as a method of extracting the soil solution in the laboratory. However, some operational conditions must be defined. The present work reports the influence of the centrifugation time (30 and 60 min) and speed (560, 2,260, and 5,080 g) on the observed composition of the soil solution of four samples from two typical and representative Brazilian Oxisols. The concentrations of Ca, Mg, Al, Na, K, Mn, Fe, Zn, Cl−, and F− varied significantly with the centrifugation speed but not with time. Charge balance calculations for the evaluation of the electrochemical neutrality showed that an extraction time of 1 h at a speed of 2,260 g should be recommended for further studies with similar soil samples. Some relationships, such as ionic strength vs. electrical conductivity and pH vs. Al concentration were also investigated.