The present work was carried out during two successive seasons of 2017/2018 and 2018/2019 at the Experimental Farm of El-Qassassein Horticultural Research Station, Ismailia Governorate, to study the effect of active dry yeast aqueous solution rates (2, 4, 6 and 8 g/L.) with two application types (soil drench and foliar spray) each solely or in combination to obtain the pest growth,
good production of flowers yield and the highest chemical composition of Calendula officinalis L. plants, under sandy soil conditions. The active dry yeast levels were applied three times starting from
1 st Dec. with 21 days interval between them. The flower heads were collected manually in 13 flower picking times starting from 1st Feb. with one-week intervals between them. The treatment of 4 g/L. active yeast solution in both soil drench and foliar spray and their interaction gave the highest plant
height, number of branches/plant, fresh and dry weights of herb/plant, number of inflorescences/plant, fresh and dry weights of inflorescences and ray flowers (g)/plant, dry yield of inflorescences, ray flowers (kg)/fed. and total carotenoids content, during the two seasons. The interaction treatment of 4 g/L. soil drench + 4 g/L. foliar spray yielded 86.8 and 85.4 % of total productivity/year of dry weight of inflorescences (g)/plant, and 85.3 and 84.0 % of total productivity/year of dry weight of ray flowers (g)/plant from the 6th to 13th flower picking times, during the two seasons, respectively.