Soil Test Extractants for Predicting Selenium in Plants

Two Greenhouse studies were conducted in which fourwing saltbush [Atriplex canescens (Pursh) Nutt.] and (Astragalus bisucatus L.) were grown in pots containing 3 kg of 18 different soils and mine spoil materials collected from locations in Wyoming with documented histories of selenium (Se) toxicity in livestock. Plant Se concentration was compared to total soil Se and Se extracted by ammonium bicarbonate-DTPA (AB-DTPA), hot water, saturated paste extracts, DTPA (2 h), and 0.5 mol Na2CO3 L−1. Data from saturation extracts were found to be the most useful in predicting Se concentration in both fourwing saltbush (r 2 = 0.66) and two-grooved milkvetch (r 2 = 0.78). The results suggest that soil or mine spoil materials that yield < 0.1 mg L−1 in a saturation extract may produce Se-toxic fourwing salt-bush plants (> 5 mg Se kg−1). Sodium carbonate extracted the largest fraction of the total soil Se among the five soil tests. Values obtained from all five extractants were highly correlated.