Effects of nitrogen nutrition onSandersoniacut flower and tuber production in a soil‐less medium

Abstract

The effects of five nitrogen (N) application rates-14. 2, 28.4, 56.8, 113.6, and 227.2 g N/ m 2 (equivalent to 37.5, 75, 150, 300, and 600 ppm of N as a daily liquid feed), on greenhouse cut flower production and outdoor tuber production in Sandersonia aurantiaca (Hook.) were compared in two experiments using a peat:pumice medium. Stem length and weight declined with increasing N rate. Tuber weight declined slightly along with tuber quality with increasing N rate. High N rates resulted in an increased incidence of tuber disorders including secondary tuber formation and tuber rots. Leaf N concentration increased with N rate to a maximum of 56.8 g N/m 2 , but tuber N continued to increase (from 0.68 to 2.01% dry weight) with increasing N rate. The effects of the N rates on tuber storage and subsequent cut flower production were assessed at two N rates (28.4 and 113.6 g N/m 2 ) in a third experiment. Leaf nutrient concentrations were not affected when tubers were forced at the two N rates in the third experiment nor was vase-life of stems. This study indicates that sandersonia requires low-medium amounts of nitrogen and that an N rate of Received 12 May 1998; accepted I February 1999 c. 28.4 g/m 2 would optimise both tuber quality and stem production for sandersonia grown in a soil-less medium. Tuber and leaf nutrient concentrations at this N rate could be used for crop cultural guidelines for both flower and tuber production. H98021

Effects of soil nutrient levels on leaf purpling inHypericum

“…The leaf concentrations of Mg are greatest at the early sampling dates when the leaves are young and rapidly growing, and least at the later sampling date when the leaves were older and new leaf production had ceased. This pattern of nutrient decline during the season has been shown in other crops such as sandersonia (Clark & Burge 1999). Increasing K/Mg ratio did not affect leaf K concentrations at the second sampling date (P = 0.195).…”

Effects of soilless media, nutrition, and pH on tuber russeting inSandersonia aurantiaca

“…Tuber weight increased with N rate in the bark medium, but in the peat/pumice medium maximum tuber weight occurred at the middle N rate (100 g/m 2 ). The high N rate resulted in higher tuber N concentrations (3.92-4.22% dry weight) than reported previously (Clark 1997;Clark & Burge 1999a, 2000. In these previous studies N rates were 5-227.2 g N/m 2 and maximum tuber weight occurred at tuber N concentrations of c. 2.0-2.5%.…”

“…Similarly, in the current study tuber weight was greatest for peat/pumice at the middle N rate (tuber N concentration 2.37%), but for the bark medium at the high N rate when tuber N concentration was 4.22%. In previous studies using soilless media, tuber weight was less at low rates of nutrients and at tuber N concentrations of c. 1% (Clark & Burge 1999a, 2000. In a soil-based experiment (Clark 1997), tuber weight was greater at very low rates of N (5-20 g N/m…”

“…Regression analysis of tuber weight and percentage secondary tubers gives a relationship of R 2 = 0.780. Previous studies have found that secondary numbers are greater at high N rates (Clark & Burge 1999a), lower plant densities (Clark & Burge 1996), with production during the warmer summer months (Clark & Burge 1997), and at warmer temperatures and higher irradiance (Brooking et al 1997). This indicates that secondary tuber numbers are affected by a number of factors such as growing medium, nutrition, temperature, and light.…”

“…The strongest relationship with russeting was with nitrogen (N) (R 2 = 86%) and then with potassium (K) (R 2 = 75%). In a N study (Clark & Burge 1999a) tubers were observed to be white at a low N rate whereas those from high N rates were often russeted.…”