Critical Dilution Curves for Nitrogen, Phosphorus, and Potassium in Potato Group Andigenum

The critical dilution curves (CDC) for nitrogen (Nc), phosphorus (Pc), and potassium (Kc) obtained from total dry biomass (W) and leaf area index (LAI) were used as a diagnostic tool to determine nutrient status and to adjust fertilization rates in two cultivars of potato (Solanum tuberosum L.) group Andigenum. The research determined allometric ratios of Nc, Pc, and Kc (%) and nutrition index (NI) based on W and LAI in cultivars Diacol Capiro (Capiro) and Pastusa Suprema (Suprema). Additionally, optimal fertilization rate was evaluated to achieve maximum yields during two growth cycles in contrasting environments of the Andean zone of Colombia. The CDC was validated using W in Capiro: Nc = 6.23W(-0.320); Pc = 0.523W(-0.198); Kc = 9.02W(-0.269) and in Suprema: Nc = 6.74 W-0.327; Pc = 0.536W(-0.186); Kc = 6.58W(-0.135) and presented higher robustness than the CDC obtained from LAI. Capiro presented a lower dilution coefficient b for Kc than Suprema. The NI ranged between 0.25 and 1.32 with better fit in Capiro and relative yields (RY) starting from 40% without fertilization; for Suprema, null to marginal response to fertilization was obtained, indicating a luxury uptake of N (NI 1-1.5) with RY starting from 70%. Except for this research, Nc, Pc, and Kc have not been validated for cultivars of group Andigenum. The CDC for this cultivated group could serve to identify deficiency, sufficiency, or excess of N, P, and K, and to predict final yield per cultivar under highland equatorial conditions.