Effect of Phosphorus Fertilization on the Selenium Concentration in Alfalfa (Medicago sativa)

A study was conducted to determine the effect of P fertilization on the Se concentration in alfalfa. Adding P to the soil increased the Se concentration in alfalfa grown in the greenhouse on six of 14 soils from the northwestern United States. The Se concentration increase in alfalfa resulting from P addition was noted on some alkaline and some acid soils. Phosphorus addition increased the availability to alfalfa of both native and applied Se in the Portneuf silt loam. Applying 160 kg P/ha either as H 3 PO 4 or concentrated superphosphate to Gooding sandy loam in the field increased the Se concentration in alfalfa from a level marginal for animal requirements to an adequate level.