Volume or Weight Soil Sampling for Extracting Mehlich III Elements with Routine Analyses?

Abstract

ABSTRACTThe subsampling of soil for laboratory testing may be done by the volumetric or gravimetric methods. The specific method used may depend on regional or national regulations. Here, we present an analysis of the results, obtained by Mehlich III extraction, of 100 mineral soils and 24 organic soils in Quebec. Samples were selected by independent laboratories and were analyzed using the volumetric method (soil scoop), the volumetric–gravimetric method (using the soil scoop then weighing the scoop), and as a reference, the fully gravimetric method. The results showed that volumetric sampling was inadequate to accurately determine base cation content (KM-III, CaM-III, and MgM-III). Also, the volumetric–gravimetric method was inaccurate in determining the content of PM-III, AlM-III, and FeM-III. Moreover, the results reported using ratio-based indexes showed none of these imprecise behaviors and showed accurate results regardless of the sampling method.