Variability of extratected phosphorus caused by analytical variation on Mehlich - 1 and 3 methods

Conselho Nacional de Desenvolvimento Científico e Tecnológico Performing a soil analysis requires a series of operations so a specific element may be conveniently extracted to be then detected or measured. Protocol methods have been adjusted to facilitate the execution, however here may be variability in analytical results by different laboratories even if they follow the same general principles of the method. This study aimed to identify sources of variability that affect analytical precision and accuracy of phosphorus extracted by Mehlich-1 and Mehlich-3 under variations in protocol procedures. Eleven soil samples in the surface layer (0 - 20 cm) were selected and collected in the geomorphologic Plateau and Central Depression of Rio Grande do Sul state, Brazil, which have wide variation of physical, chemical and mineralogical composition, including different clay contents and phosphorus availability. In the laboratory, seven experiments were conducted to determine the effect of different factors: sample particle size (