Further observations on plant selenium levels in Western Australia

Abstract

A survey of plant selenium was carried out in the agricultural district of Western Australia in the spring of 1962. Pasture samples were collected from mid-August to mid-November during, or shortly after, the spring flush of growth in the different districts. Pastures were collected from both 'light' and 'heavy' country in each of the districts, and whenever possible, fertilizer history was recorded and botanical composition determined. Pasture samples from the 10-15 inch rainfall belt averaged 0.26 p.p.m. selenium ; from the 15-20 inch rainfall belt, 0.08 p.p.m., from the 21-30 inch rainfall belt, 0.056 3.p.m ; and from the higher than 30 inch belt, 0.036 p.p.m. If the critical level for selenium deficiency syndromes is placed at 0.05 p.p.m., then deficiency levels mg appear in all rainfall belts, the lower limit of which is the 15 inch isobyet. Regression analyses showed that there was a significant difference between the selenium contents of pastures from heavy and light soils in each rainfall area. The indicator condition of selenium levels of 0.05 p.p.m or less (white muscle disease) has not been seen in the northern range of the higher rainfall districts, although here, as elsewhere, plant selenium levels appear to be predicated on mean annual rainfall figures and on type of county. Grasses and cereals tended to dominate the pastures in the areas with less than 15 inches of rainfall a-year, while subterranean clover with admixtures of capeweed and grasses were chiefly found in the higher rainfall districts.