Studies on the nutrition of pasture plants in the south-west of Western Australia. I. The effect of copper, zinc and potassium on the growth of Dwalganup strain of Trifolium subterraneum L. on sandy soils

Abstract

The results of pot-culture experiments and field trials designed to examine the effects of copper, zinc, and potassium on the growth of Dwalganup subterranean clover on a number of Western Australian soils are presented and discussed. Highly significant yield increases from application of one or more nutrients were observed on all soils examined. The effects of applied copper were greater in the second year than in the seeding year under deficiency conditions in the field. Significant interaction effects were observed only with copper and potassium. Maximum yields in two of the field trials were low even with application of all three nutrients. Reasons for this are suggested. Data on leaf area changes indicated that, in contrast to the increasing severity of potassium deficiency with age of the plant, both copper and zinc deficiency tended to diminish after the commencement of the flowering stage. The importance of such time trends in the interpretation of interaction effects is emphasized. The economic significance of the potassium problem is stressed and a number of aspects requiring investigation are outlined.