No abstract

The effect of nitrogen (N), phosphorus (P), potassium (K) and lime additions to container-grown Schlumbergera x buckleyi were examined in two experiments. In each case rooted cuttings were grown in peataperlite (1:1, vav), with three plants per pot, for 17 months in a heated greenhouse. Foliage growth and¯ow-ering were strongly enhanced by added N and fertilization of between 1800 and 2200 g N m 73 (105±130 g N m 73 per month) and a foliar N content of 3.4±4.2% were recommended. Flowering was delayed by high N but promoted by added P. Added P also strongly in¯uenced foliage growth and¯owering but at lower rates than that for N fertilization. Recommended P rates were between 650 and 850 g P m 73 (40±50 g P m 73 per month) and a foliar P content of 1.3±1.5%. This species appeared tolerant of a wide range of pH levels, with a range of lime rates having no signi®cant effect. A foliar calcium (Ca) content of 0.7% to 0.9% was suggested with a recommended media pH of 5.5±6.5. High K strongly in¯uenced the production of stem segments and¯owering in a small experiment and fertilization of JOURNAL OF PLANT NUTRITION, 24(4&5), 767±778 (2001) 767

Seedlings of Radermachera sinicaHemsl. were grown in peat/composted bark (7:3, v/v) medium to evaluate their response to five levels of nitrogen (N), phosphorus (P), potassium (K), and lime. R. sinica proved to be an adaptable species quite tolerant of nutrient extremes. There was a strong response to added N with an optimum at 300 g N/m 3 , equivalent to 85 g N/m 3 per month and a leaf N content of 2.5%. P, and more noticeably K, had little influence on foliage growth and consequently there were few nutrient interactions. Optimum P additions were at c. 200 g P/m 3 or a leaf P content of 0.35%, whereas high P fertilisation depressed foliage growth. The lime rate for optimum growth was at 6 kg/m 3 and pH 4.8.

Low-cost potting mixes containing sawdust, Nitrolime, and Floranid were evaluated as possible growing media for bedding plants and vegetable seedlings. Plants of all varieties grown in peat/sand media consistently performed better than those grown in peat/sand/sawdust. Nitrogen immobilisation in the sawdust-based medium was probably the reason for the reduced growth. The peat/sandlOsmocote combination was significantly better than any other medium/fertiliser combination for lettuce, polyanthus, and silverbeet (dry weight). The peatlsandlsawdust/Osmocote combination, although producing less foliage growth than the former, promoted more foliage growth than the other medium/fertiliser combination for lettuce, cabbage, and silverbeet (visual rating) and for lettuce, polyanthus, and silverbeet (dry weight). Plants grown with Osmocote (14:6: 12) consistently outperformed those grown with the other two fertilisers.

Rooted cuttings ofAcalypha hispaniolae were grown in peat/composted bark (7 : 3 v/v) medium for 4 months to evaluate their response to five levels of nitrogen (N), phosphorus (P), potassium (K), and lime. There was a linear response to added N with foliar dry matter increasing over the range 0-600 g N/m 3 and a leaf N content of c. 3.3% at this highest rate of N. Predicted maximum flower dry weight occurred at 400 g N/m 3 . P additions suppressed growth and flowering. Foliage P content needs to be held at c. 0.2%. Chlorosis of mature leaves was most severe with N deficiency but was also caused by P toxicity. Chlorosis in immature leaves was attributed to Pinduced iron deficiency and was most severe when the P : Fe ratio in the leaves was 62 : 1. Liming reduced P toxicity and the lime rate for maximum growth was 6-9 kg/m 3 and a pH of c. 5. K additions had little effect on growth. A foliage K content of c. 2% is recommended.