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 plant growth  and  chemical constituents of sweet potato (Buregard cv.) grown in clay soil. Results showed that, the triple interaction among sulphur application at 150 kg/fad., FYM at 4 ton/fad., and spraying sweet potato plants with chitosan at 150 ppm, significantly increased vine length, both number of branches and leaves/plant, dry weight of shoot, chlorophyll a and total chlorophyll, N, P and K contents and its uptake by shoot. On the other hand, the lowest values of each of the above-mentioned traits were recorded with the interaction treatment among without sulphur, without FYM and without chitosan   in both seasons.