EFFECTS OF NITROGEN AND POTASSIUM NUTRITION ON SOIL-GROWN SANDERSONIA-AURANTIACA STEM AND TUBER PRODUCTION

The effects of four nitrogen (N) application rates (5, 10, 20, 40 g N/ m(2)) and four potassium (K) soil levels (0.4, 0.8, 1.8, 3.2 me/100 g) on soil-grown Sandersonia aurantiaca (Hook.) stem and tuber productio n were evaluated. Leaf concentrations of N and K declined with plant a ge but were greater at the higher N and K levels, respectively. Small increases in some stem production indices (flower number, percentage s ide laterals) occurred with increasing N but declined with increasing K (stem length). Tuber weights declined with increasing levels of N an d K with the largest tubers, 7.9 g produced at 10 g/m(2) N and 1.8 me/ 100 g K. This study indicates that moderate N and K nutrition rates sh ould be used for soil-grown sandersonia to optimise both stem producti on and tuber weights.