Mineral elements in temperate crop and pasture plants. I. Zinc

Abstract

Twenty-five annual crop and pasture plant varieties, from 21 species, were grown on a lateritic gravelly sand at each of three rates of a trace element mixture containing copper, zinc, manganese, molybdenum, cobalt, selenium, and iodine. The plant tops were sampled at three stages during the growing season, and at maturity.

Zinc concentrations in the tops fell with increasing age in all species and trace element treatments. Total amounts of zinc in the tops rose throughout the growing season in all species except lupins, which showed marked declines after flowering.

Trace element applications increased the zinc contents of most species by similar relative amounts, so that rankings of species on the basis of the zinc concentrations varied only slightly among treatments. Yield responses to trace elements other than zinc did not appear to affect changes in zinc concentration due to treatment. Nor did the species rankings vary appreciably among harvests.

Compared on the basis of their geometric mean concentrations over all treatments and harvests, species varied widely in their zinc contents. Legumes and herbs had higher concentrations than cereals and grasses. Within taxonomic groups other than the grasses, species adapted to sandy or acid soils had generally higher concentrations in the tops than those adapted to medium- or heavy-textured soils.

It is suggested that species differ characteristically in their feeding power for zinc, and that relative differences among species are probably maintained over a wide range of soil types and nutritional levels. These differences, being considerably greater than apparent differences in zinc requirement, are probably the major factor governing susceptibility to zinc deficiency in the field.

Possible bases for species differences in their feeding power for soil zinc are discussed.