EFFECT OF VARIOUS SOURCES OF SELENIUM FERTILIZATION ON THE SELENIUM CONCENTRATION OF FEED CROPS

This study was conducted in Prince Edward Island (PEI) Canada to determine the effect of various sources of selenium (Se) (i) sodium selenate (ii) selcote (iii) selcote 2 year and (iv) lime coated Se-granules on the Se concentration in cereals, forages and soybeans. All sources were applied to the soil at 10 g Se ha-1. For soybeans, sodium selenate was also applied as a foliar spray. All sources, in the year of application, proved effective in raising the feed crop Se to more than 100 mug Se kg-1, the minimum level required to prevent Se deficiency diseases in livestock. Lime coated Se granules resulted in much lower Se in all crops than other Se sources. Selenium concentration in soybean grain was higher than in cereals and forages treated with Se. Selenium concentration in soybean grain was higher following foliar applications of sodium selenate (3005 mug kg-1) than following soil application (1930 mug kg-1). Experiments conducted at a second location produced similar results. In most cases, soybean grain contained higher Se than either the whole plant or leaves. Selcote resulted in significantly higher Se, during the first year in soybean and forages, than selcote 2 year. This relationship was not consistent on cereals. Selenium concentrations in the second year crop of soybeans were below the minimum required level of 100 mug kg-1 needed to prevent Se deficiency in livestock for all Se sources except for the selcote 2 year source. Only the latter Se source resulted in a Se concentration of > 100 mug kg-1 for 2 yr. Soybeans fertilized with Se should prove to be an excellent feed crop for enriching grain with Se.