Effect of Nitrogen on the Nutritional Quality andMicrobial Load of Roselle (Hibiscus sabdariffa L)

The effect of nitrogen concentration on the nutritional quality and microbial load of samples of Hibiscus sabdariffa were studied. Samples of calyces harvested from three different nitrogen levels viz; 0 kg N / ha, 30 kg N / ha and 60 kg N / ha were used. Nutritional composition and the microbial counts of the calyces were determined. Highest significantly (P = 0.01) different crude protein and nitrogen value of 12.06% and 1.93 % were obtained from calyces fertilized with 60 kg N / ha. Ascorbic acid content of the calyces increased with increase in nitrogen levels. For the microbial load analysis, there was no significant influence of nitrogen on the microbial load. However, the least bacteria (2.6 x 104 cfu / ml) and fungi (5.68 x 105 cfu / ml) counts were obtained from calyces fertilized with 30 kg N / ha. Therefore, inorganic nitrogen fertilizer of up to 60 kg N / ha can be applied to Roselle plant in order to increase some of the nutritional constituents but should not exceed 30 kg N / ha for the purpose of reduced microbial load.