Bray/Kurtz, Mehlich III, AB/D and ammonium acetate extractions of P, K and MG in four oklahoma soils

Multi‐element soil extraction solutions offer increased convenience in soil testing laboratory operations. The recently developed Mehlich III and ammonium bicarbonate‐DTPA multi‐element extraction solutions were each compared with the more conventional Bray/Kurtz extractant for P determination and with 1N ammonium acetate for K and Mg determinations. The latter two solutions are single and tri‐element extractants in current use by the Oklahoma State University Soil Testing Laboratory. The Bray/Kurtz extractant was also compared with the 1N ammonium acetate for K and Mg determination. A total of 310 soil samples from four soil types, which included five long‐term soil fertility experiments, were used for these comparisons. All sites have been in continous wheat production and received various N‐P‐K fertilizer treatments for at least: five years prior to soil sampling. AIT soil samples were extracted in triplicate for each extractant. Results showed that extraction of elements, by all solutions were highly correlated to the Bray/Kurtz and 1N ammonium acetate:extractants for Oklahoma soils.