ABSTRACT
Chemical analysis is one of the most important tools for soil and water characterization. Soil testing began in the nineteenth century and was primarily used for soil classification and fertilizer recommendations. Recently the purpose of soil testing has been extended beyond improving crop production to encompass environmental evaluation. Before Daubeny (1845) proposed the concept of active (plant-available) and dormant (plant-unavailable or slowly available) forms of plant nutrients in soils, only total nutrient analysis was conducted. In the century and a half since that time, many chemical
solutions (‘‘extractants’’) have been tested and used for the determination of plant-available nutrients in soils. In addition, emphasis has shifted from the simple determination of total concentrations to determining the various fractions of the forms of each element in soil. Often the most commonly used extractants are mixtures of two or more chemicals. Each of the different extractants requires a corresponding specific set of analytical procedures for quantifying the elements of interest in the extraction solution. These analyses have been widely used for agronomic purposes, contaminated soil remediation, ecosystem restoration, and solute transport modeling. Some methods were developed to be universally applicable procedures. However, because of complexity of soils, no method has been accepted as universally applicable. Soil testing laboratories in each region of the United States have established standard extractants and analytical methods for selected chemicals for agronomic purposes only. In 1980 the U.S. Environmental Protection Agency (USEPA) published a document, Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (SW-846), which includes testing methods for soils and other solids. The third edition of this document, released recently, lists 127 standard methods (USEPA, 2004).
