Pitaya is still a culture lacking of research and information that support the definition/adaptation of production systems adapted to Brazilian soils and climate, although in recent years there has been an increase in its agricultural expansion, as in Brazil as in other countries. Thus, the aim of this study was to evaluate the effect of mineral fertilization on the early growth of pitaya and then to obtain directed information to the definition of adequate fertilization managements of the culture. For this purpose, we tested five doses of nitrogen (N) (0, 150, 300, 450 and 600 mg dm-3) and potassium (K) (0, 75, 150, 225 and 300 mg dm-3) , and the levels of each nutrient, arranged in a 5x5 factorial design with four blocks. For a significant interaction (p<0.05) it was proceeded an adjustment in response surfaces of type Y = β0 + β1(A) + β2(A)² + β3(B) + β4(B)² + β5(A).(B) + e. Estimates of phenotypic correlations were obtained considering only the range of N and K that promoted the best answers to the access pitaya traits. At the end of this study it was found that the application of increasing doses of N and K, and the interaction NxP affected the levels of both nutrients in the soil, roots and shoots, thus influencing the early growth of the pitaya plants. The most satisfactory yields occur when there is 0.7 mmol dm-3 of K in the soil, and 20 - 25 g kg-1 of N with 30 - 40 g kg-1 of K in the shoot. These values were obtained for the application 300 - 450 mg dm-3 of N with 150 - 225 mg dm-3 of K. The sum of the length of cladodes (SCC) and the dry mass of the root system (DMRS) are the explanatory variables that have large direct effects on the dry weight of cladodes (DWC).
manuring; Cactaceae; exotic fruits; Hylocereus undatus
