Critical levels of selenium in different crops grown in an alkaline silty loam soil treated with selenite-Se

Critical levels of selenium in raya (Brassica juncea Czern L.), maize (Zea mays L.), wheat ( Triticum aestivum L.) and rice ( Oryza sativa L.) were worked out by growing these crops in an alkaline silty loam soil treated with different levels of selenite-Se ranging from 1 to 25 mu g g(-1) soil. Significant decrease in dry matter yield was observed above a level of 5 mu g Se g(-1) soil in raya and maize; 4 mu g Se g(-1) soil in wheat and 10 mu g Se g(-1) soil in rice shoots. The critical level of Se in plants above which significant decrease in yield would occur was found to be 104.8 mu g g(-1) in raya, 76.9 mu g g(-1) in maize, 41.5 mu g g(-1) in rice and 18.9 mu g g(-1) in wheat shoots. Significant coefficients of correlation were observed between Se content above the critical level and dry matter yield of raya as well as rice (r = -0.99, P <= 0.01), wheat (r = -0.97, P <= 0.01) and maize (( r = -0.96, P <= 0.01). A synergistic relationship was observed between S and Se content of raya ( r = 0.96, P <= 0.01), wheat (r = 0.89, P <= 0.01), rice ( r = 0.85, P <= 0.01) and maize (r = 0.84, P <= 0.01). Raya, maize and rice absorbed Se in levels toxic for animal consumption (i.e. > 5 mg Se kg) 1) when the soil was treated with more than 1.5 mu g Se g(-1). In case of wheat, application of Se more than 3 mu g g(-1) soil resulted in production of toxic plants.