Seedlings of Catharanthus roseus “Grape Cooler” was transplanted to cell packs of media: peat-vermiculite-perlite (MM220), peat-hydrophilic rockwool (ABS), and peat-hydrophobic rockwool (REP) and grown in subirrigation trays using 20N-4.4P-17K fertilizer at 50, 150 or 250 ppm N applied at each irrigation. Shoots of four plants in each of two replications were harvested 2, 3, 4 and 5 after transplant. Leaf samples from the third harvest were analyzed for essential elements. Electrical conductivity (EC) was measured in saturated media extracts at each harvest. Significant media by fertilizer interactions were obtained for fresh weight and leaf area at the final harvest. Greatest growth was obtained with 50 ppm N in ABS, but with 150 ppm N in MM 220 and REP. In tehse, growth was similar at 50 and 150 ppm N, but less growth REP than MM220 at 250 ppm. More growth was produced with ABS at 50 ppm N, but less at 150 or 250 ppm N. Leaf tissue N increased 38.5 to 54.5 mg g-1 dry wt. as fertilized increased 50 to 150 ppm, while other nutrients were not significantly affected. Media EC increased with time and fertilizer concentration, with EC in all media fertilized with 250 ppm N exceeding 4.5 dS m-1 at the final harvest.
If the inline PDF is not rendering correctly, you can download the PDF file here.