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Variable selenium (Se) concentration effects in sand culture and sandy soils were studied on raya (Brassica juncea Coss.), an oil crop, in the greenhouse. The sand cultures were supplied with Se at rates of 0, 0.5, 1, 2, 4, 8, 16, and 32 parts per million (ppm), whereas the sandy soil was treated with 0, 0.1, 0.5, 1, 2, 4, 8, and 16 ppm Se as sodium selenite (Na2SO3·5H2O). Sulfur (S) was supplied at rates of 0, 50, and 100 ppm in both cases. When S was not applied in the sand cultures, 1 ppm and higher Se decreased root and shoot weight significantly. Four parts per million and higher concentrations of Se induced white chlorosis in younger leaves of raya. In sandy soil, yield reduction started with 2 ppm and higher Se doses, but there was no chlorosis in the leaves. When S was applied at the rate of 50 and 100 ppm in both cases, the dry weights of roots and shoots increased significantly. In the presence of 100 ppm S, shoot dry matter was higher than the control for 1, 2, 4, and 8 ppm Se application, and significant reduction in dry matter yield was observed with 16 and 32 ppm Se. In the absence of added S, Se tended to accumulate in the plant roots, but with the addition of S, more Se was translocated to the shoots.The plant nitrogen, sulfur, methionine, cystine, and cysteine concentration decreased with increased Se concentration in the growth medium. Supplying S at 50 and 100 ppm decreased Se and increased all other measured chemical concentrations in raya plants. Selenium and S were antagonistically related.