Electrical conductivity and frequency of application in the fertigation of Oncidium flexuosum | Electrical conductivity and frequency of application in the fertigation of Oncidium flexuosum

English. Fertigation is very common in orchid nutrition, although there are no instructions that match electrical conductivity to the frequency of application. The objective was to analyze the action of electrical conductivity and fertilizer application frequencies on the growth and nutrition of Oncidium flexuosum (Orchidaceae). Cloned seedlings of Oncidium flexuosum were cultivated in a greenhouse for 18 months. As substrate, sieved pine bark was used. Irrigation was manual, applying 6 mm of water daily. Fertigations were performed by watering with 50 mL of NPK solution. As a source of nitrogen (N), phosphorus (P) and potassium (K) urea, mono ammonium phosphate and potassium chloride were used diluted in five different concentrations of equal proportions by mass: C1 (1.5 g L- 1), C2 (3.0 g L-1), C3 (6.0 g L-1), C4 (12.0 g L-1) and C5 (24.0 g L-1). The electrical conductivities of the solutions showed 1,294, 2,315, 4,986, 8,632.5 and 16,750 mS cm-1 respectively. The solutions were applied at three frequencies: monthly (F1), biweekly (F2) and weekly (F3). Only irrigated plants were used as controls. Aerial part height, number of pseudobulbs and shoots, length and diameter of the largest pseudobulb, dry mass of leaves, pseudobulbs and roots; and macronutrient contents (N, P, K, Ca and Mg) in the shoot, were submitted to analysis of variance and Tukey test at 5% of significance. The design was completely randomized with 10 replications, in a 5x3+1 factorial scheme. The electrical conductivity of the solutions showed better values ​​on plant height and root dry mass. The increase in electrical conductivity enhanced the growth of Oncidium flexuosum and increased P and K levels in leaves and K in pseudobulbs. The NPK 20-20-20 formulation is suitable when applied monthly at 3.0 g L⁻¹, biweekly at 1.5 g L⁻¹, or weekly at 0.75 g L⁻¹.

Portuguese. Fertigation is very common in orchid nutrition, although there are no instructions that match electrical conductivity to the frequency of application. The objective was to analyze the action of electrical conductivity and fertilizer application frequencies on the growth and nutrition of Oncidium flexuosum (Orchidaceae). Cloned seedlings of Oncidium flexuosum were cultivated in a greenhouse for 18 months. As substrate, sieved pine bark was used. Irrigation was manual, applying 6 mm of water daily. Fertigations were performed by watering with 50 mL of NPK solution. As a source of nitrogen (N), phosphorus (P) and potassium (K) urea, mono ammonium phosphate and potassium chloride were used diluted in five different concentrations of equal proportions by mass: C1 (1.5 g L- 1), C2 (3.0 g L-1), C3 (6.0 g L-1), C4 (12.0 g L-1) and C5 (24.0 g L-1). The electrical conductivities of the solutions showed 1,294, 2,315, 4,986, 8,632.5 and 16,750 mS cm-1 respectively. The solutions were applied at three frequencies: monthly (F1), biweekly (F2) and weekly (F3). Only irrigated plants were used as controls. Aerial part height, number of pseudobulbs and shoots, length and diameter of the largest pseudobulb, dry mass of leaves, pseudobulbs and roots; and macronutrient contents (N, P, K, Ca and Mg) in the shoot, were submitted to analysis of variance and Tukey test at 5% of significance. The design was completely randomized with 10 replications, in a 5x3+1 factorial scheme. The electrical conductivity of the solutions showed better values ​​on plant height and root dry mass. The increase in electrical conductivity enhanced the growth of Oncidium flexuosum and increased P and K levels in leaves and K in pseudobulbs. The NPK 20-20-20 formulation is suitable when applied monthly at 3.0 g L⁻¹, biweekly at 1.5 g L⁻¹, or weekly at 0.75 g L⁻¹.