Comparing tests for soil fertility. III. Evaluation of phosphate availability in Alfisols by Olsen, Mehlich 3, electro‐ultrafiltration, and the paper‐strip methodology procedures

Abstract The suitability of the “iron‐impregnated paper‐strip”; (Pi) methodology for the assessment of phosphate (P) availability in soils has been tested on the basis of a comparison with the classical Olsen method as well as with the new‐generation electro‐ultrafiltration (EUF) and Mehlich No. 3 (M3) extraction procedure. The EUF extractions were performed by a first 30 min run at low (L) energy conditions (20°C, max 15 mA, and 200V), followed by a 10 min run at high (H) energy conditions (80°C, max 150 mA, and 400V). The total EUF‐P extracted (T‐EUF‐P), given by the sum L‐EUF‐P + H‐EUF‐P, was also considered. The investigation was carried out on twenty samples of representative Alfisols ("Terra Rossa") from the pedoclimatic environments of the Mediterranean area. The soil samples were characterized by a large variability of their available‐P values, whose ranges were, as mg‐kg‐1 soil, 0.1–34.0 for L‐EUF‐P, 0.2–39.3 for HEUF‐P, 0.3–73.3 for T‐EUF‐P, 0.8–113.6 for Olsen‐P, 1.0–122.4 for Pi‐P, 1.1–224.6 f...