SUPPLEMENTAL LIGHTING AND NITROGEN NUTRITION EFFECTS ON YIELD AND QUALITY OF FOREVER YOURS ROSES

Abstract

Supplemental lighting and nitrogen nutrition affected growth, flowering, flower yield, foliar nitrogen content, and flower keeping quality of Rosa hybrida ’Forever Yours.’ Light treatments consisted of ambient light and ambient light supplemented with high pressure sodium lamps at intensities of 105 and 158 μEm−2 sec−1 18 h/day (7.4 and 10.8 klx). Three nitrogen levels, 100, 200, and 400 ppm, were applied with each irrigation. Supplementary light of 105 μEm−2 sec−1 increased yield, stem length, fresh weight, and stem grade but caused decreased foliar N and keeping quality. Lighting at 158 μEm−2 sec−1 increased flower yield, but decreased days to flowering, stem length, fresh weight, foliar N, keeping quality, and stem grade. Nitrogen levels of 100 and 200 ppm were insufficient to maintain foliar N content at optimum levels in lighted roses, but 200 ppm N resulted in better keeping quality compared with 100. Nitrogen alone, however, had little effect on yield and quality. Increasing the nitrogen level to 400 ppm resulted in higher foliar N content in the lighted treatments but failed to have a significant effect on the yield or quality of roses.