P.A. ROSBROOK, C.J. ASHER and L.C. BELL
The Co status of the surface horizon of eleven Queensland soils, five from sites where Co deficiency of livestock had been recorded, plus one Western Australian soil on which yield responses of lupins to applied Co had been demonstrated, was investigated in two glasshouse trials.
In one experiment, the Co-sensitive test legume, Lupinus angustifolius, was grown on the 12 soils to determine whether Co was limiting to legume growth. A significant response to added Co occurred only on the siliceous sand from Western Australia. On the basis of plant Co concentrations, two of the Queensland soils were considered deserving of further study under field conditions.
The second glasshouse experiment was designed to study species variation in Co concentration and involved growing nine grasses and nine legumes on the surface horizon of a xanthozem containing low levels of plant-available Co. Cobalt was also applied to the legume species, but no yield response was observed. With no added Co, tissue Co concentrations ranged from 15–22 µg/kg for the grass species and from 20–59 µg/kg for the legumes. The results suggest that the Co status of some Queensland soils should be investigated in the field.