This field study was undertaken at the Experimental Farm of Agriculture Faculty, Tanta University, during two seasons of 2015 and 2016 to investigate the efficiency of yeast and humic acid foliar application with the half recommended dose of NPK on plant growth, yield components and biochemical composition of roselle plant. The experiment consisted of five levels of yeast extract 0, 2, 4, 6 and 8 g/l and three levels of humic acid i.e. 0, 1 and 2 g/l. Fifteen treatment combinations were laid out in a split plot design. Treatments were twice applied, the first application was 30 days after sowing while, the second one was 20 days after the first one. Yeast and humic acid combinations influenced positively on roselle productivity as it raised plant height, stem diameter, branch number, fruit number/plant, calices yield/plant compared to control plants. Total chlorophyll, carbohydrates and anthocyanin content were increased by yeast and humic acid applications. Total protein and macro elements N, P and K showed an increase more so by the treatment of 8 g/l yeast plus 2 g/l humic acid.
So, it could be recommended for using foliar spray of yeast at concentration of 8 g/l plus 2 g/l humic acid with the half recommended dose of NPK for improving the growth and productivity of roselle plant.