Integrating the mehlich‐3 extractant into existing soil test interpretation schemes

Abstract

Abstract Nutrients were extracted from samples of two Ohio soils derived from Wisconsin‐age glacial till, a Crosby silt loam (Aerie Ochraqualfs, fine, mixed, mesic) and a Hoytville silty clay (Mollic Ochraqualfs, fine, illitic, mesic) using the Mehlich‐3 extractant, and also using Bray‐1 for phosphorus (P) and ammonium acetate (NH4OAc) for potassium (K), calcium (Ca), and magnesium (Mg). Mehlich‐3 removed more P from the soils than did Bray‐1, and determining P in the Mehlich‐3 extracts by ICP revealed more P than when determination was made using molybdate‐blue colorimetry. All relationships between quantities of P extracted by Bray‐1 and Mehlich‐3 were linear. Both Mehlich‐3 and NH4OAc removed similar quantities of K, Ca, and Mg from the Crosby soil, but results from the Hoytville soil were considerably more variable. On these and similar soils, P‐fertilizer recommendation schemes based on Bray‐1 could be adapted to Mehlich‐3 using simple linear relationships; however, relationships involving exchangeable cations may require further evaluation.