Optimization of solution: Soil ratio and shaking times of the Mehlich‐III soil test on Histosols

Abstract

Abstract The University of Florida Everglades Soil Testing Laboratory has been determining water‐extractable P in organic soils (Histosols) since 1944. The water extractant has consistently provided reliable correlations for vegetable commodities, but not for agronomic crops. Recent research has suggested that the Mehlich‐III soil test has potential for use on Histosols. However, no information indicated if solution: soil ratios (RAs) and shaking times (SHs) used for mineral soils would be appropriate for organic soils, which have appreciably lower soil bulk densities. A laboratory study with SHs ranging from 1 to 29 min and RAs ranging from 8 to 22 (v/v) arranged in a central composite rotatable design (ccd) was conducted using four Florida Histosols. Nine treatment combinations of RAs and SHs were used. Two replications of the ccd were performed with duplicate extractions for each sample. The fitted second‐degree response surface equations for P and K nutrients with surface contour plots were shown for ...