Field experiments were conducted to study the effect of gypsum and phosphate fertilizer on selenium concentration in berseem (Trifolium alexandrinum) and sorghum (Sorghum bicolor) crops in the seleniferous region of Punjab. Sulphur was applied through gypsum at 0, 4, 8 and 12 q ha^_1 and phosphorus at 0, 60, 90 and 120 kg P₂O₅ ha^_1 through di-ammonium phosphate. Selenium concentration in berseem and sorghum decreased significantly with the application of 8 and 12 q gypsum ha^_1. In different cuts of berseem, the decrease in Se concentration varied from 39% to 49% with the application of 12 q gypsum ha^_1. The effectiveness of gypsum decreased, as the growth of berseem advanced towards maturity. No consistent changes in Se concentration of fodder crops were observed with the application of phosphate fertilizer. The results suggest that gypsum application to seleniferous soils may be an economically viable option for reducing Se accumulation by forage crops. However, there is a need to further verify the role of P in regulating Se uptake by different crops.

Selenium is not an essential element for plant growth, but its level in the diet affects the health of animals and humans. The Food and Nutrition Board of the National Academy of Sciences, USA (1980) has accepted 5 mg Se kg^_1 diet (dry wt. basis) as the critical level between toxic and nontoxic feeds. Consumption of Se-rich feed is seriously affecting the health of animals and human beings in some parts of Punjab (Dhillon and Dhillon, 1997). Soils containing as low as 0.5 mg Se kg^_1 can produce fodder containing toxic levels of Se (Dhillon et al., 1992). The transfer of Se from soil through plants to food is governed by many soil-related factors, including the presence of other ions such as S, P or Fe in the soil solution (Mikkelsen et al., 1989). The classical antagonistic relationship between sulphate-S and selenate-Se uptake by various plants has been reported by many research studies (Pratley and McFarlane, 1974; Mikkelsen and Wan, 1990; and Dhillon and Dhillon, 2000). Although alfalfa (Medicago sativa) accumulated more Se than western wheat grass (Pascopyrum smithii), S amendments either as elemental S or gypsum at 1.0 Mg ha^_1 were equally effective in suppressing Se uptake (>60%) in both the forage species (Mackowiak and Amacher, 2008). Sulfate-S is a structural analog of selenate-Se, resulting in competitive uptake. Absorption of selenate-Se takes place through high affinity sulfate transporters, but the transporters favor S over Se in nonaccumulating plants (Sors et al., 2005). Greater sulphate/selenate ratios in soil solution may shift the balance toward greater sulphate uptake, resulting in lower plant Se concentrations.

Soil And Water Sciences Journal, Se content, Gypsum, Phosphorus, Berseem, Sorghum, Fluorometric Method, Antagonistic Effect, Selenate Form, Fluorometric Method, Antagonistic Relationship, Economical Amendment, Selenium Determination, Selenium Concentration.