Abstract
Roselle calyces were evaluated for their chemical composition (Ca, K, Na, Mg, vitamin C and calcium oxalate) under four nitrogen fertilizer rates (0, 184, 276 and 368 kg N ha(-1)) with four cultivars ('Sudan-1', 'Sudan-2', 'Sewa' and 'Aswan'). The 16 treatment combinations were laid out in a split plot design with four replications, and evaluated during the dry season in 2007 and 2008 at the Agricultural Experiment Station, Hada Al-Sham, King Abdulaziz University, Saudi Arabia. The results obtained show that application of 276 kg N ha(-1) produced the highest concentrations of Mg, vitamin C and calcium oxalate whereas application of 368 kg N ha(-1) produced the highest Na concentration. The cultivar 'Sudan-2' had the highest concentrations of Ca, K, Na, Mg and calcium oxalate whereas 'Sewa' had the highest concentration of vitamin C.