Foliar application of selenite and selenate to potato (Solanum tuberosum):Effect of a ligand agent on selenium content of tubers

The effect of a foliar spray of selenium on potatoes was investigated for 2 years. Amounts of 0, 50, and 150 g of Se ha(-1) were applied both as sodiu m selenate and as sodium selenite in water, either pure or with the additio n of 0.15% of soluble leonardite as a source of humic acids (pH 7). Tuber s elenium concentration increased with the application levels, both with sodi um selenate and with sodium selenite, when only aqueous solutions were used . When humic acids were added, the tuber selenium level rose more markedly after the application of sodium selenate as compared to the case of the aqu eous solutions; however, in the case of sodium selenite, the level showed a large increase only after the application of 50 g of Se ha(-1). Kinetics s howed that humic acids raised the selenate availability, but, no difference s were found in the distribution of selenium in the tuber fractions. Foliar application of selenium with humic acids was proven to be a good way to in crease the selenium content of potatoes, but the assimilation process of se lenium was simpler with selenate than with selenite.