Lupinus luteus cv. Wodjil takes up more phosphorus and cadmium than Lupinus angustifolius cv. Kalya

Abstract

A field experiment on an acidic lateritic ironstone gravel sand in south-western Australia compared how Lupinus luteus L. cv. Wodjil and L. angustifolius L. cv. Kalya used different sources of fertilizer phosphorus (P) to produce shoots and seed (grain). The sources of P were triple superphosphate, highly reactive North Carolina apatite phosphate rock and low reactive Queensland (Duchess) apatite phosphate rock, all applied 14 years previously, and triple superphosphate applied in the current year. The fertilizers contained different concentrations of cadmium (Cd) as an impurity. Concentrations of Cd were measured in lupin shoots and grain to compare how the two species took up cadmium applied as the different fertilizers. L. luteus used all sources of P more effectively than L. angustifolius to produce dried shoots and grain. Per unit of applied P as each source, the concentration of P in grain of L. luteus was consistently about double that in L. angustifolius. However, P concentrations in shoots harvested 2 months earlier were about similar, suggesting L. luteus transferred more P to grain. For each amount of each source of fertilizer P applied, the concentration of Cd in grain was always larger for L. luteus. Soil test Cd provided a good indication for when grain Cd concentration was likely to be above the maximum permissible concentration. L. luteus developed abundant third-order lateral roots (cluster roots?), which may have enabled L. luteus to take up more P and Cd from the soil than L. angustifolius.