The mineral composition of lupins. 1. A survey of the copper, molydbenum and managanese contents of lupins in the south-west of Western Australia

Abstract

Mature plant samples of four Lupinus species from several districts in the south-west of Western Australia, grown on a range of soil types, were analysed for copper, manganese and molybdenum. L. angustifolius had consistently lower copper and molybdenum contents than L. digitatus and L. luteus. L. albus was notable for its extremely high manganese contents, the levels in the seeds being 5-15 times higher than in seeds of other lupin species grown at the same site. Some correlation was found between contents of the three elements in the plants and the nature of the soil and natural vegetation at the site of collection. Manganese and molybdenum, and to a lesser extent copper, contents fell markedly on passing from the brownish sands developed over limestone along the west coast to the deeper and more leached sands further inland. All samples from sandy or gravelly soils characterised by jarrah (Eucalyptus marginata) and Banksia and Casuarina species were low in both copper and molybdenum. Samples from soils characterised by marri (E. calophylla) also tended to be low in copper, but some had quite high molybdenum contents. Manganese levels in the plants appeared to be closely related to soil texture. The levels of copper in lupins on several of the soil types used for commercial lupin growing were below those considered necessary to meet the requirements of grazing stock, especially where Lupinus angustifolius was used. Copper topdressing at commercial rates did not appear to increase the copper content of lupins substantially. No evidence was found of any relationship between the copper, manganese or molybdenum contents of lupins and the incidence of lupinosis in stock.