effect of humic acid and phosphorus on the quantity and quality of marigold (calendula officinalis l.) yield

to evaluate the effect of humic acid and phosphorus on the quantity and quality of marigold yield an experiment was conducted at research field of islamic azad university, mashhad branch, mashhad, iran, in cropping season 2010-2011. the experiment was in split plot based on randomized complete block design, with four replications. the main plots were humic acid in four levels (0, 5, 10 and 15 kg/ha) and sub plots were phosphorus (p2o5) in three levels (40, 60 and 80 kg/ha). the result showed that the highest dry flower yield (158.4 g/m2), flower number (1356 per m2), essential oil (0.55%), active ingredient of flower (0.31%), obtained in humic acid (10 kg/ha) and phosphorus (60kg/ha). the results also revalued that highest grain yield (133.8 g/m2) and seed oil (0.41%) obtained when (5 kg/ha) humic acid and 80kg/ha phosphorus were used. based on this study, humic acid (10 kg/ha) and phosphorus (60kg/ha) may result in higher yield.