Two field experiments were carried out during the two successive summer seasons of 2014 and 2015 at El-Gemmeiza Agric. Res. Station, Gharbeya Governorate, Egypt, toevaluatethe effect of sulphur, farmyard manure (FYM) levels and chitosan concentration as foliar spray and their interactions on yield and its components as well as tuber roots quality of sweet potato (Buregard cv.) grown in clay soil. Average tuber root diameter, average tuber weight, both marketable and total yield, N, P, K, total sugars and total carbohydrates contents in tuber roots at harvest time were significantly increased with the triple interaction among 150 kg/fad., sulphur, 4 ton/fad., FYM and spraying plants with  150 ppm chitosan. The increases in total yield were about 101.20 and 93.51% in for the triple interaction among 150 kg/fad., sulphur, 4 ton/fad., FYM and chitosan sprayed at 150 ppm than the untreated plants with sulphur, FYM and chitosan in the 1^st and 2^nd seasons, respectively.