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 μg g-1 soil. Significant decrease in dry matter yield was observed above a level of 5 fig Se g-1 soil in raya and maize; 4 μg Se g-1 soil in wheat and 10 μg 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 μg g-1 in raya, 76.9 μg g-1 in maize, 41.5 μg g-1 in rice and 18.9 μg 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 μg Se g-1. In case of wheat, application of Se more than 3 μg g-1 soil resulted in production of toxic plants.