Uptake of native and applied selenium by pasture species

Abstract

Abstract Selenium at 1 and 4 oz per acre was applied as sodium selenite in (a) monocalcium phosphate, and (b) superphosphate, to pastures in 13 localities covering a range of soil types. Uptake of selenium was comparatively high in the first cut. By the end of a year 1 oz treatments were of the same order as controls. The effects of 4 oz treatments were still perceptible after 400–600 days. A depression of selenium uptake by superphosphate as against monocalcium phosphate in certain cases is attributed to an increase, through correction of sulphur deficiency, of the proportion of clover in the mixed sward and to its more vigorous growth leading to dilution of selenium absorbed through the leaves. A detailed comparison between the effects of applied selenium on clover uptake from the various soils was made over the period 300–450 days following treatment. On two soils in Central Otago, a brown‐grey earth and an upland yellow‐grey earth, the effect was more sustained than on other soils. A lesser effect on an irrigated trial on Lismore silt loam is attributed to some transfer of treatments in irrigation water. Over the period the selenium content of clover, with the above exceptions, diminished exponentially with time regardless of soil type. A trial on a peat soil showed a higher initial uptake of applied selenium than was the case on mineral soils.