COMPARISON OF AN ACID AND AN ALKALINE EXTRACTING SOLUTION FOR MEASURING AVAILABLE PHOSPHORUS IN ALBERTA SOILS

Abstract

Two extracting solutions, 0.03 NH₄F + 0.03 N H₂SO₄ and 0.5 M NaHCO₃, were used to extract available phosphorus from 79 Alberta soils. Of these soils, 23 had a pH above 7.0 and 18 contained free CaCO₃. A barley test crop was grown in the greenhouse on these soils with and without added phosphorus fertilizer.The amounts of available phosphorus extracted by the NH₄F + H₂SO₄ solution were highly correlated with the amounts extracted by the NaHCO₃. The NaHCO₃ solution extracted about 40 per cent as much phosphorus as the NH₄F + H₂SO₄.The available phosphorus levels determined by both methods were highly correlated with barley growth in the greenhouse. The correlation coefficient for per cent yield and available phosphorus by the NaHCO₃ method was slightly higher than that for per cent yield and available phosphorus by the NH₄F + H₂SO₄ method. However when the check yield (yield of the treatment not receiving phosphorus fertilizer) was used as the measure of plant growth, the correlation between yield and available phosphorus was the same for both methods.