The Gharbeya Experimental Farm, El-Gemmeiza, Agric Res. Station (ARC) (Middle Delta, Egypt) conducted a field experiment over the course of two consecutive summer seasons in 2023 and 2024 to investigate the effects of compost rates as organic manure (zero and 5 ton/feddan.) and some stimulants as foliar spray (seaweed extract, fulvic acid, yeast extract, and lithovit at 2ml of each) as well as their interactions on the growth, leaf pigments, yield, and tuber roots
quality of sweet potato (Beauregard cv.) under clay soil conditions. Fertilizing sweet potato plants grown in clay soil with compost as organic fertilizer at a rate of 5 tons/fed. and spraying with fulvic acid or yeast extract at a rate of 2 milliliters per liter increased the length of the plant, the number of branches and leaves per plant, the fresh weight of the shoots and the dry weight of the plant; it also increased the concentrations of chlorophyll a, b, and total chlorophyll (a+b) in
the leaf tissues of sweet potato; weight of tuber root, marketable and total yield per feddan ; and the total sugars and starch content in the tuber roots. In this regard, the conjunction between compost at a rate of 5 tons/fed. and spraying with yeast extract at 2 ml/liter recorded a relative increase in the total yield by 50.58%, followed by adding compost and foliar spray with fulvic acid at a concentration of 2 ml/liter, which recorded a relative increase of 47.0% as an average
for the two seasons compared to the control treatment (0 compost + spraying with water).