There is a relative lack of technical studies on the adequate management of organic wastes from food processing. The aim of this study was to evaluate the effect of applying doses of a byproduct from guava processing, in the presence and absence of mineral fertilization, on the fertility of a an Ultisol (or Red-Yellow Argisol) under laboratory conditions. An entirely randomized 5x2 factorial experimental design was used with five byproduct doses, in the presence and absence of mineral fertilization, with four repetitions, for a total of 40 experimental units. Under the experimental conditions, the attributes pH, OM, K, Mg, BS, T, V, B, Fe, Zn and S-SO4(2-) were affected by the guava byproduct doses, as well as by the presence or absence of mineral fertilization. With the use of this fertilization, the variables OM, K, H+Al, T, Fe and Zn increased more as a function of byproduct dose than in the absence of fertilization. The results obtained demonstrate the potential of using this waste material in the cycling and supply of nutrients.