Nutrition of Grevillea robusta

Abstract

Seedlings of G. robusta were grown in perlite in a glasshouse in which the day/ night temperature regime was controlled at approximately 25/20°C. The effects of nutrient deficiencies and of potassium × nitrogen interactions were examined. Deficiency symptoms were observed when each major element, and the minor elements manganese and boron, were omitted from the nutrient solution, and in general omissions had significant effects on height, basal stem diameter, stem weight, leaf weight, root weight, and number and weight of branches. Omissions of zinc, copper, and molybdenum had no effect on these characteristics, and no deficiency symptoms were observed. Significant effects of increasing nitrogen and increasing potassium were obtained for all characters measured, and except for basal stem diameter there were significant potassium × nitrogen interactions. The development of deficiency symptoms for potassium and nitrogen is dependent not only on the absolute level of the particular nutrient but also on the balance of both nutrients. This was particularly evident in the case of potassium deficiency.