OPTIMIZING FERTILIZER RATES FOR TWO CULTIVARS OF GRAZIOSA GERANIUMS
Determining appropriate fertilization rates for newly introduced cultivars is important. The Graziosa series of geraniums ((Pelargonium × domesticum) × crispum) were recently released to the market, but the optimum fertilizer rate is unknown. Additionally, it is unknown if nutrition stress results in earlier flowering for this cultivar. Therefore, this fertilizer rate experiment was conducted to evaluate different levels of fertilizer rates for effective production of Merlot Red and Cherry Picotee Graziosa geraniums. Ten plants of each cultivar were fertigated with 50, 75, 100, 200, 300, or 400 mg/L N. After 8 weeks of growth, half of the Cherry Picotee and Merlot Red geraniums received a clear water leach for one week. The leached plants were then returned to constant fertigation. EC and pH were measured on a biweekly schedule and also on week 9 after the leaching event. Days to flower and the number of buds present greater than 1 cm long when the first, second, and third inflorescence flowered were recorded. The experiment was terminated when all plants had three flowering inflorescences, Merlot Red on 01 Feb. 2011 and Cherry Picotee on 17 Feb. 2011. Three non-leached plants were selected for destructive harvest to determine critical tissue concentration for each element. Leaching did not enhance flowering of either cultivar. Days to flower and number of buds for Merlot Red were not significantly different for any of the fertilizer rates. However, for Cherry Picotee, 75, 100, 200, and 400 mg/L N treatments bloomed the earliest, and while 200 mg/L N had the fewest buds, it was one of the earliest flowering and could have had a lower number of buds at this time. Based on only the EC and pH data, Merlot Red should be grown at a rate between 150 to 200 mg/L N, and using the days to bloom, EC, pH data, and foliar burn at 200 mg/L N for Cherry Picotee, the crop should be grown at a rate of 100 to 150 mg/L N.
Barnes, J., Whipker, B.E. and McCall, I. (2014). OPTIMIZING FERTILIZER RATES FOR TWO CULTIVARS OF GRAZIOSA GERANIUMS. Acta Hortic. 1034, 471-476
fertilizer, leaching, macronutrients, nitrogen, (Pelargonium × domesticum) × crispum, phosphorus, potassium