Selenium concentration of fescue and bahiagrasses after applying a selenium fertilizer

Two experiments were conducted, one with bahiagrass in North Central Florida (Gainesville) and the other with fescue in Northwest Florida (Quincy), to evaluate the selenium levels of the grasses after applying a slow release selenium fertilizer (Selcote Ultra). In the bahiagrass study, forage samples were collected from 3 X 5 m plots which had been sprayed with Selcote Ultra at treatment rates of 0, 5, 10, 15, and 20 g ha(-1) selenium. Samples were collected every two weeks for a total of six collections. In the fescue study, the procedure was the same except that forage samples were collected at 2, 4. 6, 10, 16, and 22 wk after applying the fertilizer, and the rates were 0, 5, 10, 24, and 120 g ha(-1) selenium. For bahiagrass, only the 10, 15, and 20 g ha(-1) selenium treatments reached acceptable levels in the forage (> 0.1 mg kg(-1)) for beef cattle. The 10 ha(-1) selenium treatment reached adequate levels (0.25 mg kg(-1)) only at 4 wk after application. The 15 g ha(-1) selenium treatment presented adequate levels of selenium at 21, 4. and 6 wk after application (0.19. 0.17, and 0.17 mg kg(-1). respectively). The 20 g ha(-1) selenium treatment had adequate forage selenium at 4 and 6 wk after application (0.19 and 0.23 mg kg(-1). respectively). The 5 g ha(-1) selenium treatment and the control did not reach acceptable values and were selenium deficient. All treatments were deficient at 8 and 12 wk. In the fescue study, all treatments presented adequate concentrations (0.1 mg kg(-1)) of selenium in the forage. except for the control. At two weeks after application. the 24 hit and the 120 g ha(-1) selenium treatments had toxic selenium levels in forage. However, these values declined to below toxicity (4-5 mg kg(-1)) at all other collection dates.