Methods of soil physical analysis of the Agronomic Institute of Campinas: particle size analysis (Métodos de análise física de solos do Instituto Agronômico (IAC): análise granulométrica)

Particle-size analysis separates the mineral fraction of the soil into size classes: sand, silt, and clay. The proportion of classes in the mineral material of a soil provides essential information on its characteristics and properties, which are necessary for understanding its behavior and for defining agricultural management. This bulletin presents the two most commonly used laboratory methods for particle-size analysis of soil samples, mainly for agronomic use: the pipette method and the hydrometer method. Both methods require the dispersion of individual particles and the use of sieves and sedimentation to separate the size classes. Dispersion is the most critical phase of the analytical procedure, requiring chemical dispersants and mechanical agitation. In addition to the description of the methods, some of the procedure variations and the associated successes and failures are discussed.