The growth of Yellow Bells (Geleznowia verrucosa) seedlings in response to additions of nitrogen, potassium and phosphorus fertiliser

Native plants are increasingly grown in Western Australia to produce flowers for export. The nitrogen (N), phosphorus (P) and potassium (K) requirements for optimum production of one of these species, Geleznowia verrucosa (Yellow Bells), was measured for 17-week-old seedlings in a glasshouse experiment reported here. There was a significant (P < 0.05) growth response to all levels of N fertilisers. At all levels of P and K, except for the nil K treatments, the lowest level of applied N (20 mg N/kg soil) gave the maximum dry weight of shoots. The dry weight of shoots increased with the addition of P fertiliser to the highest level (160 mg P/kg soil), particularly for the lower levels of applied K (0 and 30 mg/kg soil) and the lowest level of applied N (20 mg/kg soil). Combinations of high levels of P (P-160) and N (N-80) fertiliser severely depressed shoot growth. When applied at greater than 30 mg K/kg soil, K fertiliser depressed plant growth at all levels of N and P when compared with the lower levels of applied K. At the seedling stage of growth, critical concentrations for deficiency of both N and K were 1.3% in shoots. The critical concentrations for toxicity in whole shoots of Yellow Bells appeared to be about 1.7% for N and about 2.2% for K. Adequate concentrations of N were 1.4-1.5%, while 1.7% K appeared adequate for growth of Yellow Bell shoots.