Mineral elements in temperate crop and pasture plants. III.* Copper

Abstract

Concentrations and total amounts of copper in the tops were measured in 24 varieties of 21 annual crop and pasture species, grown in the field on a lateritic gravelly sand with three levels of copper application and sampled at three growth stages and maturity. Copper applications at the normal commercial rate in Western Australia and at three times this rate did not increase yield. Both rates increased copper concentrations slightly in young plants, but this effect had largely disappeared by flowering. Copper application did not change the relative order of species when ranked according to their copper concentrations. Copper concentrations in the tops declined with age in all species, but at differing rates. All species continued to accumulate copper up to harvest 3 (near maturity), with the exception of lupins which suffered net losses from the tops after flowering. Species varied greatly in their copper concentrations. In cereals and grasses, copper concentrations increased linearly with increasing nitrogen contents, with a tendency towards higher copper/nitrogen ratios as concentrations of both elements increased. Legumes had higher copper concentrations than grasses and cereals, especially late in the growing season, but lower and more variable copper/nitrogen ratios. Within taxonomic groups, species adapted to sandy and copper-deficient soils tended to have the highest copper concentrations and copper/nitrogen ratios, and to translocate most copper to the seeds. *Part I, Aust. J. Agric. Res., 18: 427 (1967); Part II, Aust. J. Agric. Res., 19: 353 (1968).