This study examined the effects of different sources and doses of fertilizers, as well as nutritional efficiency during the initial growth phase of rootstocks. The experiment was conducted at the Federal University of Pelotas, in a greenhouse. The experimental design consisted of completely randomized, in a three-factor scheme (2 x 2 x 4), represented by the combination of two peach rootstock cultivars (Capdeboscq and Flordaguard), two types of fertilizers (controlled release and ready availability) and four doses of fertilizer (0, 4, 8 and 12 g L−1), corresponding to a total of 16 treatments, with four replications, each including five plants. The dose of 4 g L−1 of readily available fertilizer induced superiority in the MST accumulation of the 'Capdeboscq' plants, however for the 'Flordaguard' was necessary a higher dose (8 g L−1). Higher doses than these provided a reduction in the accumulation in the phytomass, length and volume of the roots, suggesting sensitivity of the peach rootstocks to the excess of nutrients in the substrate. Despite the higher doses having induced superiority in the absorption efficiency, the lower dose (4 g L−1) of the ready-to-use fertilizer provided greater efficiency of use, which is why it is indicated for the fertilization of rootstocks, allowing greater benefit-cost. 'Capdeboscq' is suggested for use in the production of rootstocks because it exhibits greater efficiency in the use of N-P-K in view of the reduced absorption efficiency rates of these nutrients, in the lowest tested dose.