Effect of humic acid, seaweed extract and active dry yeast in Calendula officinalis plants.

Calendula officinalis is an annual herbaceous ornamental and medicinal plants were treated with humic HA at (0, 3 and 6 g/l), seaweed extract (SWE) or active dry yeast (ADY) each at (0, 1 and 2 g/l). Investigated factors significantly increased plant fresh and dry as well as flower fresh and dry weights with significant interactions between them. However, the control plants had significantly the lowest dry weight Moreover, the highest value (78.60 g/plant) being for 2g/l of SWE + 6 g/l HA treatment. The lowest flower fresh yield being for non-treated plants however, these treated with 3 or 6 g/l HA + 2 g/l of SWE or ADY had the highest yield (494.5 to 512.0 g/plant). Non-treated plants had the lowest yield of flower dry weights 52.17 g/plant. Whereas these treated with 3 g/l HA + 2 g/l of SWE or ADY had the highest yield (141.35 and 135.72 g/plant respectively). Non-treated plants had the lowest chlorophyll content 38.44. However, the highest value was for plants treated with 3 g/l HA + 1g/l SWE. The plant content of NPK was significantly increased due to HA treatment as well as SWE/ADY application with a significant interaction between them. Generally, there was no significant difference between 3 and 6 g/l of HA and plants treated with (3 g/l of HA + 2g/l of SWE or ADY) and (6 g/l of HA + 1g/l of SWE or ADY) had the highest content of these elements.  Therefore, it is recommended to treat marigold plants with 3 g/l HA + 2 g/l of SWE or ADY to achieve the highest yield of flower fresh and dry weights.