AbstractTwo laboratory‐prepared ferric hydroxy bi‐selenites and CuSeO3 applied to Portneuf silt loam in the field provided slowly available Se to alfalfa, resulting in Se concentration adequate but nontoxic for livestock. These materials have potential as Se fertilizers at low application rates. The ferric hydroxy bi‐selenites offer little or no advantage over CuSeO3. Se from BaSeO4 alone, BaSeO4‐BaSO4 mixtures, and CuSeO4 was absorbed by alfalfa in concentrations toxic to livestock. A small fraction of applied elemental Se was available immediately after application, providing adequate Se to alfalfa for livestock. The remaining elemental Se was rather inert, and supplies only slightly more Se to alfalfa than did the untreated soil the year following application.