SELENIUM UPTAKE BY PLANTS AS A FUNCTION OF SOIL TYPE, ORGANIC-MATTER CONTENT AND PH

In pots containing sandy soils at two levels (pH 5 and 7) to which 0.5 mg Se L-1 soil had been added, and increase in the proportion of clay soil or peat soil led to a decrease in the uptake of Se by spring wheat grain (Triticum aestivum L., var. Drabant) and winter rape plants (Brassica napus L., var. Emil). The effect was most pronounced for the smallest additions of clay and peat soils. Differences in Se uptake between the two pH levels were greatest in treatments where the additions of clay and peat soils were small. At the high pH, an increase in clay content from 7% to 39% resulted in a decrease in Se uptake of 79% for wheat and 70% for rape. At the low pH, the uptake decreased by 72% and 77%, respectively. At the higher pH, an increase in the content of organic matter from 1.4% to 39% resulted in decreases in Se uptake of 88% for wheat grain and 69% for rape. At the low pH, Se uptake decreased by 63% and 48%, respectively. Adding peat soil to clay soil had little effect on Se uptake. Among the limed, unmixed clay, sand and peat soils to which Se had not been added, uptake was highest from the sandy soil, i.e. 8.3 ng Se/g wheat grain and 42 ng Se/g rape. The lowest uptake rates were obtained in the clay soil, i.e. 3.0 ng Se/g for wheat grain and 9.0 ng Se/g for rape.