Effects of nitrogen nutrition on Sandersonia cut 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/ m2 (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/m2, 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/m2) 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 c. 28.4 g/m2 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.