The general aspects of the effect of nitrogen fertilization on the yield, storage quality and chemical composition of sweet potatoes have been covered in this three-year investigation at Muscatine Island;Sweet potatoes responded to nitrogen fertilizers whenever leaching of the natural soil nitrates occurred. The use of delayed applications of nitrogen appears to be the best approach to the solution of the problem;No nitrogen should be applied to the soil until the plants have become established. Then, providing that a loss of soil nitrates is probable because of leaching due to heavy rainfall, an initial application of nitrogen should be made at this time. Further applications should be made if the plants continue to show symptoms of nitrogen deficiency or if other rainy periods follow. Several inorganic fertilizers and possibly uramon are suitable sources of nitrogen for side-dressing;Phosphorus and potassium are definitely limited in the soils used in the investigation and these nutrients must be supplied before beneficial effects can be secured from the use of nitrogen;Nitrogen fertilizer applications showed no consistent or pronounced effect on the storage qualities and the sugar, starch or soluble nitrate content of sweet potatoes. The use of delayed applications of nitrogen increased the colloidal nitrogen content of the roots and in one year materially reduced the loss from storage rots.