Yacón is an Andean plant, which has been cultivated since the Inca's times for its tuber roots and their high content of fructo-oligosaccharides (FOS), sugars with low caloric yield. The consumption of yacón is recommended by holistic medicine practitioners and natural physicians alike to avoid the increase of blood glucose levels in diabetic people. Due to its economic potential, an experiment was conducted to establish N, P and K uptake. Yacón plants of the "yellow" ecotype were grown under simulated marginal nutritional and winter conditions at the Hydroponics Module of the Universidad Nacional Agraria La Molina, Lima, Peru. Nutritional conditions were controlled by utilizing a soilless culture technique. The plants were grown in sand and were supplied with four different nutrient solutions: 1) control (150 ppm N, 36 ppm P and 260 ppm K), 2) low N (100 ppm), 3) low P (20 ppm) and 4) low K (100 ppm). There were no significant differences in the growth and yield between 60 and 180 days after seeding (das) but there were at 210 das. Plants started to produce tuber roots between 60 and 90 das and the crop period was shortened from 10 to 7 months. Tuber roots were produced with the four treatments studied. At 210 das, the high and low yields were reached in the treatments low K (1.875 kg/plant) and control (1.083 kg/plant), respectively. There were no significant differences in the N, P and K concentrations in leaves and roots but there were in their uptake. There was higher K uptake in the roots than leaves. At 210 das, the tuber roots of yacón contained a greater quantity of K (4373 a 6665 mg) followed by N (1068 to 1640 mg) and P (106 to 222 mg). K would be more important for the formation and filled out of the tuber roots. The highest reducing sugars con-c1entrations in the tuber roots were reached with the treatments low K (3.40 mg.g-1)-1 and low N (3.00 mg.g-1) and the lowest reducing sugars concentrations with the treatments low P (1.27 mg.g-1) and control (1.12 mg.g -1) respectively. Finally, it is possible to grown yacon and other plants that produce roots and tubers with the soilless culture technique.