Assessment of Mehlich3 and Ammonium Bicarbonate‐DTPA Extraction for Simultaneous Measurement of Fifteen Elements in Soils

Abstract

Few existing extractions such as Mehlich3 and ammonium bicarbonate‐DTPA (ABDTPA) can be used as a multi‐element soil test. A multi‐element extraction is attractive to scientists and soil testing laboratories because it eliminates the need for multiple extractions and allows simultaneous measurement of elements by using the Inductively Coupled Plasma (ICP). The objective of this study was to evaluate Mehlich3 and ABDTPA for simultaneous measurement of 15 elements in 30 acidic and 20 alkaline U.S. soils from 21 states. Widely‐accepted, and conventional soil tests (Bray1 and Olsen for phosphorus (P); NH4OAc for calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na); diluted HCl and DTPA for aluminum (Al), cadmium (Cd), cobalt (Co), chromium (Cr), Copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were employed for the evaluation. Single and multiple regression analysis were applied to investigate the relationship between Mehlich3 or ABDTPA and the respective soil test. The results can be summarized: 1) Mehlich3 provided a good measurement for labile P in all soils while ABDTPA provided reliable results for alkaline soils; 2) Mehlich3 was a suitable extract for Ca, Mg, K, and Na for all soils while ABDTPA could not be used for Ca; 3) Mehlich3 or ABDTPA was an appropriate extract for Al, Cd, Cu, Fe, Mn, Ni, Pb, and Zn in all soils. The fact that most soils investigated had trace amounts of Co, and Cr hindered their evaluation. Accordingly, Mehlich3 extraction could be recommended for simultaneous measurement of at least 13 elements in soils.