Calibration of phosphorus and potassium fertilization for beet in Vale do Itajai region

Studies on fertilization for beet are still needed in some regions of Santa Catarina State, Brazil. The objective of this work was to evaluate the response of beet to phosphorus (P) and potassium (K) in an Haplic Cambisol, which is the predominant soil type in 70% of the Alto Vale do Itajai region. The experiment was carried out in Rio do Sul, Santa Catarina, in two crops. The first cultivation was in randomized blocks in a factorial 4x4 design (0, 200, 400 and 600 kg/ha P2O5) and (0, 150, 300 and 450 kg/ha K2O), with 3 replications. On the second crop, the rates of P and K for replacement were assessed, each original plot being splitted into three and applied 0, 33 and 66% of the initial rate of P and K. At 60 days after transplanting, diameter of roots and fresh and dry weight of leaves and roots were evaluated. In the first crop, a significant effect (alpha = 5%) was observed for the P factor on dry and fresh weight of roots as well as on root diameter. On the other hand, no effect of K was noticed, but K exportation by plants was high, reaching 172.27 kg/ha K with the dose 418 kg/ha K2O. The maximum production took place with 379 kg/ha P2O5, and exportation was 21.30 kg/ha P on dry mass of roots and leaves. In the second crop, plants responded to application of P and K, and the maximum yield was obtained with higher initial rates (450 kg/ha K2O and 600 kg/ha P2O5) and replacement rates (300 kg/ha K2O and 400 kg/ha P2O5). Beet is a crop highly demanding on nutrients, with needs of P and K higher than those recommended by local fertilization tutorials.