Available Phosphorus by Five Different Soil Testing Methods in Sandy Soils of Southwest Florida, USA

Phosphorus (P) fertilization is critical for improved vegetable production on Florida sandy soils. Mehlich 1 (M1) is the standard soil P testing solution for P fertilization recommendation in acidic soils with low cation exchange capacity. However, its suitability for calcareous and/or alkaline soils needs to be evaluated, therefore compared with that of other soil P testing methods (Mehlich 3, Bray, Olsen, and AB-DTPA) in this study. Soil samples collected from vegetable farms were characterized as alkaline/non-calcareous and calcareous soils. M1-P was well correlated with M3-, Bray-, and Olsen-P, respectively, for both soils. M1-, M3-, and Bray-P were greater from calcareous soil than non-calcareous soil for given labile P, which indicated an overestimation from calcareous soil. Olsen-P for given labile P was similar for both soils, thus well represented available P from both soils. Appropriate soil P testing methods need to be developed in calcareous and/or alkaline soils in southern Florida for improved P fertilization recommendations.