Two field experiments were carried out on sweet potato plants (Beauregard cv.) during two successive growing summer seasons of 2008 and 2009 at the newly reclaimed area, at Sadat City, of the Environmental Studies and Research Institute Farm, Minufiya University, Minufiya Governorate, Egypt. The experiments were designed to evaluate the effect of 4 concentrations of the antitranspirant (Folicote), 4 rates of irrigation level and their interaction on some characteristics of sweet potato crop. The rates of irrigation level were 100 % (control), 85%, 70% and 55% of potential evapotranspiration. The concentrations of Folicote were 15%, 10%, 5% and 0% (v/v). The results obtained showed that tuber root yield/plant and total tuber root yield decreased gradually with decreasing the amount of irrigation rates. The same trend was also recorded regarding tuber root yield with the Folicote concentrations. The interaction between irrigation
rates and Folicote concentrations was highly effective on tuber root yield character only in the first season. Water use efficiency exhibited the highest value at 85% and 70% irrigation rates in the first season of the study. Two vegetative characters, i.e. plant length and foliage fresh weight were affected by both irrigation rates and Folicote spraying concentrations. The interaction was significantly effective only in the first season of the study. Non-reducing sugars and starch percentages were positively affected by the interaction between the irrigation rates and Folicote concentrations during the second season of the study.
In this respect, foliar spray with Folicote, at 15% level can be applied as a foliar three times to the growing sweet potato plants in arid or semi-arid areas to save 15% of the recommended irrigation water and to improve the productivity of the growing sweet potato crop.