The results of a field experiment on two acid podzolized soils in the Heytesbury area, Victoria, are presented. Nutrient elements were tested on a phalaris (Phalaris tuberosa L.) - subterranean clover (Trifolium subterraneum L.) pasture on an area cleared from heath and on an adjoining area cleared from timber with an understorey of heath. Responses of clover to lime and copper, and interactions between these treatments were obtained. There was no response to potash, zinc, manganese, molybdenum, iron, magnesium, or boron on either soil. Lime increased the yield of clover at both sites, the greater effect occurring on the area cleared from timber. The effect of lime was not due to the release of soil molybdenum. Lime corrected defective nodulation, increased the survival of the plants, and to some extent also increased the yield of individual plants. The relative significance of these effects of lime in determining the final yield of clover per acre is discussed. The effect of copper was very different on the two soils. On the area cleared from heath, copper deficiency was severe. Here, copper increased the yield in the absence as well as in the presence of lime. The effect was considerably greater in the presence of lime, and this positive interaction was highly significant. Copper increased the number of plants per unit area and the yield of individual clover plants. On the area cleared from timber, copper decreased the yield in the absence of lime. Where lime had been applied, the effect of copper on the yield, though not significant, was positive. The evidence presented indicates that copper is also required on this soil. A copper deficiency symptom of subterranean clover is described. It is suggested that the copper status of the soils may influence the distribution of trees in the area.
THE EFFECT OF COPPER ON NITROGEN FIXATION IN SUBTERRANEAN CLOVER (TRIFOLIUM SUBTERRANEUM)
