Prediction of phosphorus availability from 88 Ontario soils using five phosphorus soil tests

Abstract

Abstract Five chemical soil‐P extractants were compared. Surface samples from 88 Ontario soils were collected and used to grow corn (Zea mays L.) in a greenhouse. Soil pH ranged from 5.0 to 7.6 and organic matter from 60 to 575 g kg‐1. The amount of P extracted by the five extractants was used to predict P availability to corn plants. The amounts of P extracted by the five extractants were highly correlated (r = 0.83 to 0.97). The correlation of extractable P to plant P uptake resulted in r2 values of 0.74, 0.73, 0.54, 0.65, and 0.66 for the NaHC03, AB‐DTPA, Bray‐Kurtz P1, Bray‐Kurtz P2, and Mehlich 3 extractants respectively. Adding soil pH to the equations improved the prediction of plant P uptake resulting in R2 values of 0.80, 0.80, 0.70, 0.73, and 0.75 for the NaHC03, AB‐DTPA, Bray‐Kurtz P1, Bray‐Kurtz P2 and Mehlich 3 extractants, respectively. The two alkaline extractants appeared to be equally effective and superior to the three acidic extractants with the Bray‐Kurtz P1 extractant being least effective.